Journal articles: 'Specialist species'

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Yamada, Toshihiro, Eizi Suzuki, Takuo Yamakura, and Sylvester Tan. "Tap-root depth of tropical seedlings in relation to species-specific edaphic preferences." Journal of Tropical Ecology 21, no. 2 (February 16, 2005): 155–60. http://dx.doi.org/10.1017/s0266467404002238.

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We compared seedlings of sandy-soil specialist species (Dryobalanops aromatica and Scaphium borneense) and clay-rich-soil specialist congeners (D. lanceolata and S. longipetiolatum) in a tropical rain forest in Lambir Hills National Park, Malaysia, to determine whether variations in belowground seedling architecture and allometry were related to edaphic specialization. A convergent trait that was phylogenetically independent across the two genera was the presence of a deeper tap-root at any height and any root biomass in sandy-soil specialists than in clay-rich-soil specialists. This trait was fixed independently of the edaphic conditions in which the trees actually grew. Finer-textured soils generally have better water-holding capacity; we concluded that seasonal water limitation would be more severe in sandy soils than in clay-rich soils, and that water limitation would provoke convergence in seedling root depth among species with the same edaphic preferences. All significant differences found in interspecific comparison within Dryobalanops were consistent with the water-availability hypothesis; the sandy-soil specialist had larger root biomass at any total biomass and had smaller leaf biomass at any root biomass than the clay-rich-soil specialist. However, for Scaphium this was not the case, suggesting that factors other than water-limitation may also underlie seedling allometric relationships.

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Litsios, Glenn, Anna Kostikova, and Nicolas Salamin. "Host specialist clownfishes are environmental niche generalists." Proceedings of the Royal Society B: Biological Sciences 281, no. 1795 (November 22, 2014): 20133220. http://dx.doi.org/10.1098/rspb.2013.3220.

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Why generalist and specialist species coexist in nature is a question that has interested evolutionary biologists for a long time. While the coexistence of specialists and generalists exploiting resources on a single ecological dimension has been theoretically and empirically explored, biological systems with multiple resource dimensions (e.g. trophic, ecological) are less well understood. Yet, such systems may provide an alternative to the classical theory of stable evolutionary coexistence of generalist and specialist species on a single resource dimension. We explore such systems and the potential trade-offs between different resource dimensions in clownfishes. All species of this iconic clade are obligate mutualists with sea anemones yet show interspecific variation in anemone host specificity. Moreover, clownfishes developed variable environmental specialization across their distribution. In this study, we test for the existence of a relationship between host-specificity (number of anemones associated with a clownfish species) and environmental-specificity (expressed as the size of the ecological niche breadth across climatic gradients). We find a negative correlation between host range and environmental specificities in temperature, salinity and pH, probably indicating a trade-off between both types of specialization forcing species to specialize only in a single direction. Trade-offs in a multi-dimensional resource space could be a novel way of explaining the coexistence of generalist and specialists.

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Mills, Catherine G., Rosalind J. Allen, and Richard A. Blythe. "Resource spectrum engineering by specialist species can shift the specialist-generalist balance." Theoretical Ecology 13, no. 2 (July 24, 2019): 149–63. http://dx.doi.org/10.1007/s12080-019-00436-8.

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Bowden, Chris, and André Botha. "IUCN Species Survival Commission: Vulture Specialist Group." Vulture News 72, no. 1 (March 29, 2018): 42. http://dx.doi.org/10.4314/vulnew.v72i1.a.

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Loos, Jacqueline, Jochen Krauss, Ashley Lyons, Stephanie Föst, Constanze Ohlendorf, Severin Racky, Marina Röder, Lennart Hudel, Volker Herfert, and Teja Tscharntke. "Local and landscape responses of biodiversity in calcareous grasslands." Biodiversity and Conservation 30, no. 8-9 (May 26, 2021): 2415–32. http://dx.doi.org/10.1007/s10531-021-02201-y.

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AbstractAcross Europe, calcareous grasslands become increasingly fragmented and their quality deteriorates through abandonment and land use intensification, both affecting biodiversity. Here, we investigated local and landscape effects on diversity patterns of several taxonomic groups in a landscape of highly fragmented calcareous grassland remnants. We surveyed 31 grassland fragments near Göttingen, Germany, in spring and summer 2017 for vascular plants, butterflies and birds, with sampling effort adapted to fragment area. Through regression modelling, we tested relationships between species richness and fragment size (from 314 to 51,395 m2), successional stage, habitat connectivity and the per cent cover of arable land in the landscape at several radii. We detected 283 plant species, 53 butterfly species and 70 bird species. Of these, 59 plant species, 19 butterfly species and 9 bird species were grassland specialists. Larger fragments supported twice the species richness of plants than small ones, and hosted more species of butterflies, but not of birds. Larger grassland fragments contained more grassland specialist plants, but not butterfly or bird specialists. Increasing amounts of arable land in the landscape from 20 to 90% was related to the loss of a third of species of plants, and less so, of butterflies, but not of birds. Per cent cover of arable land negatively correlated to richness of grassland specialist plants and butterflies, but positively to grassland specialist birds. We found no effect by successional stages and habitat connectivity. Our multi-taxa approach highlights the need for conservation management at the local scale, complemented by measures at the landscape scale.

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Li, Shuning, Richard Jovelin, Toyoshi Yoshiga, Ryusei Tanaka, and Asher D. Cutter. "Specialist versus generalist life histories and nucleotide diversity in Caenorhabditis nematodes." Proceedings of the Royal Society B: Biological Sciences 281, no. 1777 (February 22, 2014): 20132858. http://dx.doi.org/10.1098/rspb.2013.2858.

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Species with broad ecological amplitudes with respect to a key focal resource, niche generalists, should maintain larger and more connected populations than niche specialists, leading to the prediction that nucleotide diversity will be lower and more subdivided in specialists relative to their generalist relatives. This logic describes the specialist-generalist variation hypothesis (SGVH). Some outbreeding species of Caenorhabditis nematodes use a variety of invertebrate dispersal vectors and have high molecular diversity. By contrast, Caenorhabditis japonica lives in a strict association and synchronized life cycle with its dispersal host, the shield bug Parastrachia japonensis , itself a diet specialist. Here, we characterize sequence variation for 20 nuclear loci to investigate how C. japonica 's life history shapes nucleotide diversity. We find that C. japonica has more than threefold lower polymorphism than other outbreeding Caenorhabditis species, but that local populations are not genetically disconnected. Coupled with its restricted range, we propose that its specialist host association contributes to a smaller effective population size and lower genetic variation than host generalist Caenorhabditis species with outbreeding reproductive modes. A literature survey of diverse organisms provides broader support for the SGVH. These findings encourage further testing of ecological and evolutionary hypotheses with comparative population genetics in Caenorhabditis and other taxa.

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Gaete-Eastman, C., C. C. Figueroa, R. Olivares-Donoso, H. M. Niemeyer, and C. C. Ramírez. "Diet breadth and its relationship with genetic diversity and differentiation: the case of southern beech aphids (Hemiptera: Aphididae)." Bulletin of Entomological Research 94, no. 3 (June 2004): 219–27. http://dx.doi.org/10.1079/ber2004298.

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AbstractHerbivorous insect species with narrow diet breadth are expected to be more prone to genetic differentiation than insect species with a wider diet breadth. However, a generalist can behave as a local specialist if a single host-plant species is locally available, while a specialist can eventually behave as a generalist if its preferred host is not available. These problems can be addressed by comparing closely related species differing in diet breadth with overlapping distributions of insect and host populations. In this work, diet breadth, genetic diversity and population differentiation of congeneric aphid species from southern beech forests in Chile were compared. While at the species level no major differences in genetic diversity were found, a general trend towards higher genetic diversity as diet breadth increased was apparent. The aphid species with wider diet breadth, Neuquenaphis edwardsi (Laing), showed the highest genetic diversity, while the specialist Neuquenaphis staryi Quednau & Remaudière showed the lowest. These differences were less distinct when the comparisons were made in the same locality and over the same host. Comparison of allopatric populations indicates that genetic differentiation was higher for the specialists, Neuquenaphis similis Hille Ris Lambers and N. staryi, than for the generalist N. edwardsi. Over the same host at different locations, genetic differentiation among populations of N. edwardsi was higher than among populations of N. similis. The results support the assumption that specialists should show more pronounced genetic structuring than generalists, although the geographical distribution of host plants may be playing an important role.

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Melville, Jane. "Evolutionary correlations between microhabitat specialisation and locomotor capabilities in the lizard genus Niveoscincus." Australian Journal of Zoology 55, no. 6 (2007): 351. http://dx.doi.org/10.1071/zo08035.

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The evolutionary consequences of generalised versus specialised habit is a central issue in organismal biology. Theory predicts that specialist species may have greater capabilities than generalist species in particular habitats but will not be able to maintain this excellence across a broad range of habitats. The evolutionary consequences of ecological specialisation, in terms of functional capabilities, were investigated in the lizard genus Niveoscincus from Tasmania. Breadth of microhabitat occupation and ecologically relevant locomotor capabilities were quantified across the genus. Laboratory performance trials demonstrated that some species excelled in just a few of the five performance traits measured, while other species performed well at all traits but did not excel at any. Results of comparative analyses demonstrate that there is a significant evolutionary correlation between microhabitat breadth and range of locomotor capabilities. These results provide convincing evidence that habitat specialists have a correspondingly limited range of locomotor capabilities.

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Garcés-Restrepo, Mario F., M. Zachariah Peery, and Jonathan N. Pauli. "The demography of a resource specialist in the tropics: Cecropia trees and the fitness of three-toed sloths." Proceedings of the Royal Society B: Biological Sciences 286, no. 1894 (January 16, 2019): 20182206. http://dx.doi.org/10.1098/rspb.2018.2206.

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Resource specialists persist in a narrow range of resources. Consequently, the abundance of key resources should drive vital rates, individual fitness, and population viability. While Neotropical forests feature both high levels of biodiversity and numbers of specialist species, no studies have directly evaluated how the variation of key resources affects the fitness of a tropical specialist. Here, we quantified the effect of key tree species density and forest cover on the fitness of three-toed sloths ( Bradypus variegatus ), an arboreal folivore strongly associated with Cecropia trees in Costa Rica, using a multi-year demographic, genetic, and space-use dataset. We found that the density of Cecropia trees was strongly and positively related to both adult survival and reproductive output. A matrix model parametrized with Cecropia –demography relationships suggested positive growth of sloth populations, even at low densities of Cecropia (0.7 trees ha −1 ). Our study shows the first direct link between the density of a key resource to demographic consequences of a tropical specialist, underscoring the sensitivity of tropical specialists to the loss of a single key resource, but also point to targeted conservation measures to increase that resource. Finally, our study reveals that previously disturbed and regenerating environments can support viable populations of tropical specialists.

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Wang, Sibao, Andreas Leclerque, Monica Pava-Ripoll, Weiguo Fang, and Raymond J. St. Leger. "Comparative Genomics Using Microarrays Reveals Divergence and Loss of Virulence-Associated Genes in Host-Specific Strains of the Insect Pathogen Metarhizium anisopliae." Eukaryotic Cell 8, no. 6 (April 24, 2009): 888–98. http://dx.doi.org/10.1128/ec.00058-09.

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ABSTRACT Many strains of Metarhizium anisopliae have broad host ranges, but others are specialists and adapted to particular hosts. Patterns of gene duplication, divergence, and deletion in three generalist and three specialist strains were investigated by heterologous hybridization of genomic DNA to genes from the generalist strain Ma2575. As expected, major life processes are highly conserved, presumably due to purifying selection. However, up to 7% of Ma2575 genes were highly divergent or absent in specialist strains. Many of these sequences are conserved in other fungal species, suggesting that there has been rapid evolution and loss in specialist Metarhizium genomes. Some poorly hybridizing genes in specialists were functionally coordinated, indicative of reductive evolution. These included several involved in toxin biosynthesis and sugar metabolism in root exudates, suggesting that specialists are losing genes required to live in alternative hosts or as saprophytes. Several components of mobile genetic elements were also highly divergent or lost in specialists. Exceptionally, the genome of the specialist cricket pathogen Ma443 contained extra insertion elements that might play a role in generating evolutionary novelty. This study throws light on the abundance of orphans in genomes, as 15% of orphan sequences were found to be rapidly evolving in the Ma2575 lineage.

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Powney, Gary D., Steve S. A. Cham, Dave Smallshire, and Nick J. B. Isaac. "Trait correlates of distribution trends in the Odonata of Britain and Ireland." PeerJ 3 (November 19, 2015): e1410. http://dx.doi.org/10.7717/peerj.1410.

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A major challenge in ecology is understanding why certain species persist, while others decline, in response to environmental change. Trait-based comparative analyses are useful in this regard as they can help identify the key drivers of decline, and highlight traits that promote resistance to change. Despite their popularity trait-based comparative analyses tend to focus on explaining variation in range shift and extinction risk, seldom being applied to actual measures of species decline. Furthermore they have tended to be taxonomically restricted to birds, mammals, plants and butterflies. Here we utilise a novel approach to estimate occurrence trends for the Odonata in Britain and Ireland, and examine trait correlates of these trends using a recently available trait dataset. We found the dragonfly fauna in Britain and Ireland has undergone considerable change between 1980 and 2012, with 22 and 53% of species declining and increasing, respectively. Distribution region, habitat specialism and range size were the key traits associated with these trends, where habitat generalists that occupy southern Britain tend to have increased in comparison to the declining narrow-ranged specialist species. In combination with previous evidence, we conclude that the lower trend estimates for the narrow-ranged specialists could be a sign of biotic homogenization with ecological specialists being replaced by warm-adapted generalists.

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de Andrade, Rafael B., Jennifer K. Balch, Junia Y. O. Carreira, Paulo M. Brando, and André V. L. Freitas. "The impacts of recurrent fires on diversity of fruit-feeding butterflies in a south-eastern Amazon forest." Journal of Tropical Ecology 33, no. 1 (December 20, 2016): 22–32. http://dx.doi.org/10.1017/s0266467416000559.

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Abstract:In the south-eastern Amazon, positive feedbacks between land use and severe weather events are increasing the frequency and intensity of fires, threatening local biodiversity. We sampled fruit-feeding butterflies in experimental plots in a south-eastern Amazon forest: one control plot, one plot burned every 3 y, one plot burned yearly. We also measured environmental parameters (canopy cover, temperature, humidity). Our results show no significant differences in overall species richness between plots (34, 37 and 33 species respectively), although richness was lower in burned plots during the dry season. We found significant differences in community composition and structure between control and burned plots, but not between burned treatments. In the control plot, forest-specialist species represented 64% of total abundance, decreasing to 50% in burned every 3 y and 54% in yearly burned plots. Savanna specialist species were absent in the control plot, but represented respectively 8% and 3% of total abundance in burned plots. The best predictor of the change in spatial community patterns and abundance of forest specialists was canopy cover. Although we found high resilience to forest burning in many species, our study suggests that fire disturbance can still be a threat to forest specialists due to changes in microclimate.

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Mather, Jennifer A., Tatiana S. Leite, and Allan T. Batista. "Individual prey choices of octopuses: Are they generalist or specialist?" Current Zoology 58, no. 4 (August 1, 2012): 597–603. http://dx.doi.org/10.1093/czoolo/58.4.597.

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Abstract Prey choice is often evaluated at the species or population level. Here, we analyzed the diet of octopuses of different populations with the aim to assess the importance of individual feeding habits as a factor affecting prey choice. Two methods were used, an assessment of the extent to which an individual octopus made choices of species representative of those population (PSi and IS) and 25% cutoff values for number of choices and percentage intake of individual on their prey. In one population of Octopus cf vulgaris in Bermuda individuals were generalist by IS=0.77, but most chose many prey of the same species, and were specialists on it by >75% intake. Another population had a wider prey selection, still generalist with PSi=0.66, but two individuals specialized by choices. In Bonaire, there was a wide range of prey species chosen, and the population was specialists by IS= 0.42. Individual choices revealed seven specialists and four generalists. A population of Octopus cyanea in Hawaii all had similar choices of crustaceans, so the population was generalist by IS with 0.74. But by individual choices, three were considered a specialist. A population of Enteroctopus dofleini from Puget Sound had a wide range of preferences, in which seven were also specialists, IS=0.53. By individual choices, thirteen were also specialists. Given the octopus specialty of learning during foraging, we hypothesize that both localized prey availability and individual personality differences could influence the exploration for prey and this translates into different prey choices across individuals and populations showed in this study.

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Ngumbi, E., and H. Fadamiro. "Species and sexual differences in behavioural responses of a specialist and generalist parasitoid species to host-related volatiles." Bulletin of Entomological Research 102, no. 6 (May 30, 2012): 710–18. http://dx.doi.org/10.1017/s0007485312000326.

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AbstractThe relationship between the degree of specialization of parasitoids and their responses to host-related volatiles is an important and current evolutionary question. Specialist parasitoids which have evolved to attack fewer host species are predicted to be more responsive to host-related volatiles than generalists. We tested the above prediction by comparing behavioural responses of both sexes of two parasitoids (Hymenoptera: Braconidae) with different degrees of host specificity, Microplitis croceipes (Cresson) (specialist) and Cotesia marginiventris (generalist), to different suites of synthetic host-related volatile compounds. The compounds tested at two doses (1 and 100μg) include two green leaf volatiles (GLVs: hexanal and (Z)-3-hexen-1-ol) and four herbivore-induced plant volatiles (HIPVs: (Z)-3-hexenyl acetate, linalool, (Z)-3-hexenyl butyrate and (E,E)-α-farnesene). Two hypotheses were tested: (i) M. croceipes (specialist) would show relatively greater behavioural responses to the HIPVs, whereas C. marginiventris (generalist) would show greater behavioural responses to the GLVs, and (ii) females of both species would show greater responses than conspecific males to the host-related volatiles. At the low dose (1μg), females of the specialist showed significantly greater responses than females of the generalist to three of the tested HIPVs, (Z)-3-hexenyl acetate, linalool and (Z)-3-hexenyl butyrate. In contrast, females of the generalist showed relatively greater responses to the GLVs. The same trends were recorded at the high dose but fewer significant differences were detected. In general, similar results were recorded for males, with the exception of linalool (an HIPV) which elicited significantly greater response in the generalist than the specialist. Comparing the sexes, females of both species showed greater responses than conspecific males to most of the tested volatiles. The ecological significance of these findings is discussed.

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M. J. S. Bowman, D., and J. C. Z. Woinarski. "Biogeography of Australian monsoon rainforest mammals: implications for the conservation of rainforest mammals." Pacific Conservation Biology 1, no. 2 (1994): 98. http://dx.doi.org/10.1071/pc940098.

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Monsoon rainforests form an archipelago of small habitat fragments throughout the wet-dry tropics of northern Australia. According to the definition of Winter (1988) the current monsoon rainforest mammal assemblage contains only one rainforest specialist mammal species (restricted to Cape York Peninsula), and is dominated by eutherian habitat generalists (murids and bats) that mostly occur in surrounding savannah habitats. The mammal assemblages in monsoon rainforests across northern Australia (Cape York Peninsula, Northern Territory and the Kimberley) are essentially regional subsets of the local savannah and mangrove mammal assemblages, and consequently share only a limited number of species in common (most of which are bats). The lack of rainforest specialists in northwestern Australia is thought to be due to: (i) the lack of large tracts (> 1 000 ha) of monsoon rainforest habitat; (ii) the possible substantial contraction of these habitats in the past; and (iii) the limited extent of gallery rainforests, such rainforests being important habitats for rainforest mammals in South American savannahs. Unfortunately it is not possible to identify the threshold of habitat area required to maintain populations of monsoon rainforest specialist mammal species because of an impoverished fossil record pertaining to the past spatial distribution of monsoon rainforests. The implications of the lack of a specialist mammal fauna in Australian monsoon rainforests for the future of heavily fragmented tropical rainforests elsewhere in the world is briefly discussed. It is concluded that the analogy of habitat fragments to true islands is weak, that rainforest plant species are less vulnerable to local extinction than mammals, that the loss of mammal rainforest specialists may not result in a dramatic loss of plant species, and that corridors of rainforest may be critical for maintenance of rainforest mammal assemblages in areas currently subject to forest clearance.

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Ramiadantsoa, Tanjona, Ilkka Hanski, and Otso Ovaskainen. "Responses of generalist and specialist species to fragmented landscapes." Theoretical Population Biology 124 (December 2018): 31–40. http://dx.doi.org/10.1016/j.tpb.2018.08.001.

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Alouw, J. C., and N. J. Miller. "Effects of benzoxazinoids on specialist and generalist Diabrotica species." Journal of Applied Entomology 139, no. 6 (December 16, 2014): 424–31. http://dx.doi.org/10.1111/jen.12194.

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Soga, Masashi, and Shinsuke Koike. "Patch isolation only matters for specialist butterflies but patch area affects both specialist and generalist species." Journal of Forest Research 18, no. 3 (June 2013): 270–78. http://dx.doi.org/10.1007/s10310-012-0349-y.

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Martinez, Mariano M., Juan P. Isacch, and Martin Rojas. "Olrog's Gull Larus atlanticus: specialist or generalist?" Bird Conservation International 10, no. 1 (March 2000): 89–92. http://dx.doi.org/10.1017/s0959270900000071.

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A study was made of the feeding behaviour of Olrog's gull Larus atlanticus in winter. Although feeding mainly on crabs they also, contrary to previous observations, made use of discarded offal, much as other species of gull. Such generalist feeding habits are likely to be beneficial to the conservation of the species.

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Martin, K. C., and W. J. Freeland. "Herpetofauna of a northern Australian monsoon rain forest: seasonal changes and relationships to adjacent habitats." Journal of Tropical Ecology 4, no. 3 (August 1988): 227–38. http://dx.doi.org/10.1017/s0266467400002790.

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ABSTRACTThe herpetofauna of a floodplain monsoon rain forest in northern Australia is composed primarily of species from non rain forest habitats. The majority of frog species use rain forest as a seasonal refuge, and there is a marked increase in numbers during the dry season. Faunal richness lies within limits expected on the basis of the length of the dry season and species richnesses of non-Australian faunas. There are few lizard species and an abundance of frog species (none of which is a rain forest specialist) in comparison to rain forest herpetofaunas in other tropical regions. The impoverished lizard fauna, and the paucity of rain forest specialists may be because (a) seasonal invasion of rain forest by frogs prevents evolution of, or colonization by, specialists or (b) rain forest specialists may not have been able to cross semiarid habitats separating the Northern Territory from eastern Australian rain forests. The herpetofaunas of monsoon forests in Cape York Peninsula may provide a means of distinguishing between these hypotheses.

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Sugasawa, Shoko, and Hiroyoshi Higuchi. "Seasonal contrasts in individual consistency of oriental honey buzzards' migration." Biology Letters 15, no. 6 (June 2019): 20190131. http://dx.doi.org/10.1098/rsbl.2019.0131.

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Individual consistency in migration can shine light on the mechanisms of migration. Most studies have reported that birds are more consistent in the timing than in the routes or stopover sites during migration, but some specialist species showed the opposite patterns, being more consistent in spatial than temporal aspects of migration. One possible explanation for this contrast is that specialists rely on particular food or habitat resources, which restrict the migratory routes they can take, leading to high spatial consistency. If this is the case, the effect of specialist foraging should become apparent only when birds forage, instead of fasting and flying continuously. To test this effect, we analysed individual consistency in migration of the oriental honey buzzard ( Pernis ptilorhynchus ), a specialist raptor that feeds on honeybees and wasps, using a long-term tracking dataset. As honey buzzards make extended stopovers during which they forage in spring but not in autumn, the spatial consistency should be higher in spring than in autumn. Honey buzzards were highly consistent in both their migratory routes and stopover sites in Southeast Asia, but only during spring migration. Our results highlight an important link between species' migratory consistency and foraging ecology.

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Zhao, Lei, Hua Yong Zhang, Wang Tian, and Fang Zhao. "Species Coexistence in Ecosystems with Specialist Predation: Trophic Regulation in Gradients of Resource Productivity." Advanced Materials Research 1073-1076 (December 2014): 1178–81. http://dx.doi.org/10.4028/www.scientific.net/amr.1073-1076.1178.

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Specialist predation is believed to play a crucial role in maintaining biodiversity of ecosystems, whereas its underlying mechanism is still unclear. Here we analyzed a general model of a tritrophic system containing specialist predators. A new graphical approach based on the balance of resource recruitment and consumption was used. The analyses show that specialist predation can promote coexistence of producer species by increasing resource availability, which waken the exploitive competition between producers. TheR* rule, the dominant rule in traditional resource competition theory, is still dominant in infertile environment. In rich environment, the occurrence of specialist predator increases the equilibrium resource concentration and thus leads to the coexistence of the weak competitor. In high resource productivity environment all the species can coexist.

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VÁSQUEZ-ARÉVALO, Francisco A., Ricardo ZÁRATE-GÓMEZ, Jacob B. SOCOLAR, Juan DÍAZ-ALVÁN, and Pedro E. PÉREZ-PEÑA. "First record of the gray-legged tinamou, Crypturellus duidae, and other poor-soil specialist birds from peatlands in the Putumayo River basin, Loreto, Peru." Acta Amazonica 50, no. 2 (June 2020): 155–58. http://dx.doi.org/10.1590/1809-4392201901531.

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ABSTRACT Crypturellus duidae (Tinamidae) is a poor-soil specialist with isolated populations in Amazonia, and is considered restricted to white-sand forest habitats. We report the first record of C. duidae in a peatland forest in northern Peru, in the Putumayo River basin. Our record extends the known distribution of C. duidae between two disjoint areas of occurrence in Peru and Colombia, and shows its presence in peatland forest, another forest type on nutrient-poor soils. Additionally, we report the presence of other poor-soil specialist bird species that were previously registered in peatlands. Together with the new record of C. duidae, these bird records provide evidence of the diversity of poor-soil specialists in peatland forests.

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Szöllősi, Eszter, Zsófia Tóth, Katharina Mahr, Herbert Hoi, and Ádám Z. Lendvai. "Extremely low malaria prevalence in a wetland specialist passerine." Parasitology 147, no. 1 (September 12, 2019): 87–95. http://dx.doi.org/10.1017/s0031182019001215.

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AbstractAvian malaria (caused by Plasmodium spp.) and avian malaria-like infections (caused by Haemoproteus spp.) are widespread and can seriously affect the health of their bird hosts, especially of immunologically naïve individuals. Therefore, these parasites have long been in the focus of bird-parasite studies. However, the species richness and diversity of these protozoan species have only been revealed since the use of molecular techniques. Diversity and prevalence of these parasites among different bird species and even between populations of a species show a large variation. Here, we investigated prevalence of avian malaria and avian malaria-like parasites in two distant populations of a non-migratory wetland specialist passerine, the bearded reedling (Panurus biarmicus). While previous studies have shown that reed-dwelling bird species often carry various blood parasite lineages and the presence of the vectors transmitting Plasmodium and Haemoproteus species has been confirmed from our study sites, prevalence of these parasites was extremely low in our populations. This may either suggest that bearded reedlings may avoid or quickly clear these infections, or these parasites cause high mortality in this species. The remarkably low prevalence of infection in this species is consistent with earlier studies and makes bearded reedlings a possible model organism for investigating the genetic or behavioural adaptations of parasite resistance.

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Clavel, Joanne, Romain Julliard, and Vincent Devictor. "Worldwide decline of specialist species: toward a global functional homogenization?" Frontiers in Ecology and the Environment 9, no. 4 (June 2, 2010): 222–28. http://dx.doi.org/10.1890/080216.

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Wilson, Brent, and Lee-Ann C. Hayek. "Distinguishing relative specialist and generalist species in the fossil record." Marine Micropaleontology 119 (September 2015): 7–16. http://dx.doi.org/10.1016/j.marmicro.2015.07.001.

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Pflüger, Femke J., Johannes Signer, and Niko Balkenhol. "Habitat loss causes non-linear genetic erosion in specialist species." Global Ecology and Conservation 17 (January 2019): e00507. http://dx.doi.org/10.1016/j.gecco.2018.e00507.

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Sobecka, E., and M. Słomińska. "Species richness, diversity and specificity of the parasites of bream Abramis brama (L.) and perch Perca fluviatilis L. in the estuary of the Odra River, Poland." Helminthologia 44, no. 4 (December 1, 2007): 188–92. http://dx.doi.org/10.2478/s11687-007-0030-8.

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AbstractThe parasitological studies were carried out on bream and perch from brackish water of Pomeranian Bay and the Szczecin Lagoon — a mouth of the Odra River. Bream and perch hosted 21 and 13 parasitic species, respectively. The species richness and diversity of parasites were much higher for bream and the abundance of parasites in bream was nearly four-fold higher than that in perch. Faunistic similarity of both parasite communities was low. The dominant group of parasites in both fish hosts was digeneans. Five species were specialists of bream, while only one species was a perch specialist. Five new host records have been reported in Poland for the following species: Myxobolus dispar, Hysterothylacium aduncum, Khawia sinensis, Echinorhynchus gadi and Pomphorhynchus laevis.

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Razola, I., and J. M. Rey Benayas. "Effects of woodland islets introduced in a Mediterranean agricultural landscape on local bird communities." Web Ecology 9, no. 1 (June 4, 2009): 44–53. http://dx.doi.org/10.5194/we-9-44-2009.

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Abstract. This study assesses whether the afforestation approach consisting in the introduction of woodland islets in “agricultural seas” can reconcile the restoration of woody vegetation and the persistence of open-habitat bird populations, providing further opportunities for other forest species to enrich bird diversity at the landscape level. We compared the species richness and abundance of bird communities in a field with 16 introduced woodland islets and in a nearby abandoned field located in central Spain during spring and winter time. The woodland islets presented higher accumulated species richness as well as a higher probability of finding new species if sampling effort were increased only in winter time. These trends were the opposite during spring time. Mean species richness and mean bird abundance were lower at the woodland islets than at the abandoned field in both seasons. We found a higher abundance of open-habitat specialist species in the abandoned field. Woodland islets favoured the wintering of chiffchaff Phylloscopus collybita. We did not find any effects on the only forest specialist species (blue tit Parus caeruleus) in spring. Bird richness and abundance were higher in edge islets than in inner islets. The introduction of larger and mixed plantations connected by hedgerows and a management that favoured the development of big trees, a lower tree density and a diverse shrub layer could promote bird diversity, allowing forest specialists and open-habitat species to coexist at the landscape scale.

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Halloy, Monique, and Gordon M. Burghardt. "Ontogeny of Fish Capture and Ingestion in Four Species of Garter Snakes (Thamnophis)." Behaviour 112, no. 3-4 (1990): 299–317. http://dx.doi.org/10.1163/156853990x00257.

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AbstractThe feeding behaviour of four species of garter snakes (Thamnophis butleri, T melanogaster, T. radix, and T sirtalis) was observed in an attempt to determine differences across species and among age groups with respect to capturing, handling and swallowing large and small fish. Although belonging to the same genus, the four species differ widely in habitat and prey preferences (T. butieri being recognized as an earthworm specialist, T melanogaster as an aquatic specialist, and the other two species as generalists). Overall, feeding patterns were quite similar across species following a general sequence of capturing fish, maneuvering the jaws to either the head or tail of the fish (the head being "chosen" more often), and swallowing it. Head-first ingestion was related to prey size: the larger the fish the greater the probability the snake would ingest it head first. When this behaviour was analysed more closely, species and age differences emerged. Adults were more efficient at capturing and ingesting fish head-first and took less time to handle and swallow their prey than did juveniles. This difference was not as marked in the two specialist species as in the two generalist species. Considering differences within species and age classes with respect to their handling behaviour of either a large or a small fish, T melanogaster handled both sizes of prey in a time period that was not significantly different, T. butleri took significantly more time to handle a large fish whereas T radix and T. sirtalis took considerably more time to handle a large fish as newborns but not as adults. These results support field observations that T. melanogaster is an aquatic specialist, T. butleri, an earthworm specialist, and the other two species, generalists. In spite of the similarities between the two generalist species, similarities were also found between T. butleri and T. radix which are believed to the taxonomically related.

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Piacentini, Vítor de Queiroz, and Isabela Galarda Varassin. "Interaction network and the relationships between bromeliads and hummingbirds in an area of secondary Atlantic rain forest in southern Brazil." Journal of Tropical Ecology 23, no. 6 (October 29, 2007): 663–71. http://dx.doi.org/10.1017/s026646740700449x.

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The reciprocal importance of bromeliads and hummingbirds has been proposed for many years, even suggesting coevolution between these two groups. Nevertheless, data are lacking that allow a better test of the relationships involved. Here we investigate the relationship between bromeliads and hummingbirds in an area of secondary Atlantic rain forest in southern Brazil. The study examined the interactions among 12 species of bromeliad and 10 of hummingbird at Reserva Natural Salto Morato, Paraná state. The number of flowering species of bromeliad and the species richness and abundance of hummingbirds were quantified monthly between November 2004 and October 2005. Focal observations on each bromeliad species were made to determine the hummingbird visitors. Neither species richness nor abundance of hummingbirds were related to bromeliad phenology. Together with the monthly variation in visit frequency by a given pollinator to a given plant, these factors indicate a generalization in the use of bromeliads by hummingbirds and argue against tight coevolution. Ramphodon naevius and Thalurania glaucopis were the main pollinators in the community. Aechmea nudicaulis was the most generalist bromeliad species. The generalist species interacted with other generalists or with asymmetric specialists and there was no specialist–specialist interaction. This produced a strongly organized and nested matrix of interactions. This nestedness is similar to other plant-pollinators networks, supporting the hypothesis that the evolutionary relationship between bromeliads and hummingbirds is no stronger than that of other pollination networks.

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Lybbert, Andrew H., Justin Taylor, Alysa DeFranco, and Samuel B. St Clair. "Reproductive success of wind, generalist, and specialist pollinated plant species following wildfire in desert landscapes." International Journal of Wildland Fire 26, no. 12 (2017): 1030. http://dx.doi.org/10.1071/wf16222.

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Wildfire can drastically affect plant sexual reproductive success in plant–pollinator systems. We assessed plant reproductive success of wind, generalist and specialist pollinated plant species along paired unburned, burned-edge and burned-interior locations of large wildfires in the Mojave Desert. Flower production of wind and generalist pollinated plants was greater in burned landscapes than adjacent unburned areas, whereas specialist species responses were more neutral. Fruit production of generalist species was greater in burned landscapes than in unburned areas, whereas fruit production of wind- and specialist-pollinated species showed no difference in burned and unburned landscapes. Plants surviving in wildfire-disturbed landscapes did not show evidence of pollination failure, as measured by fruit set and seed:ovule ratios. Generalist- and specialist-plant species established in the interior of burned landscapes showed no difference in fruit production than plants established on burned edges suggesting that pollination services are conserved with increasing distance from fire boundaries in burned desert landscapes. Stimulation of plant reproduction in burned environments due to competition release may contribute to the maintenance of pollinator services and re-establishment of the native plant community in post-fire desert environments.

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Gábor, Lukáš, Vítězslav Moudrý, Vincent Lecours, Marco Malavasi, Vojtěch Barták, Michal Fogl, Petra Šímová, Duccio Rocchini, and Tomáš Václavík. "The effect of positional error on fine scale species distribution models increases for specialist species." Ecography 43, no. 2 (November 2019): 256–69. http://dx.doi.org/10.1111/ecog.04687.

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Sandoval, Cristina P., and Vernon R. Vickery. "TIMEMA DOUGLASI (PHASMATOPTERA: TIMEMATODEA), ANEW PARTHENOGENETIC SPECIES FROM SOUTHWESTERN OREGON AND NORTHERN CALIFORNIA, WITH NOTES ON OTHER SPECIES." Canadian Entomologist 128, no. 1 (February 1996): 79–84. http://dx.doi.org/10.4039/ent12879-1.

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AbstractTimema douglasi sp.nov. is described from southwestern Oregon and northern California, USA. It is the third parthenogenetic species in the genus and is a specialist feeder on old-growth Douglas fir, occasionally causing serious defoliation. Timema knulli Strohecker is synonymized with Timema californicum Scudder.

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Ctvrtecka, Richard, Katerina Sam, Erik Brus, George D. Weiblen, and Vojtech Novotny. "Frugivorous weevils are too rare to cause Janzen–Connell effects in New Guinea lowland rain forest." Journal of Tropical Ecology 30, no. 6 (August 7, 2014): 521–35. http://dx.doi.org/10.1017/s0266467414000406.

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Abstract:A community of frugivorous weevils was studied by quantitative rearing of 57 weevil species represented by 10485 individuals from 326 woody plant species in lowland rain forest in Papua New Guinea. Only fruits from 35% of plant species were attacked by weevils. On average, weevils were reared from only 1 in 33 fruits and 1 kg of fruit was attacked by 2.51 individuals. Weevil host specificity was relatively high: 42% of weevil species fed on a single plant genus, 19% on a single plant family and only 16% were reared from more than one family. However, monophagous specialists represented only 23% of all reared individuals. The average 1 kg of fruits was infested by 1.84 individuals of generalist weevils (feeding on allogeneric or allofamilial host species), 0.52 individual of specialists (feeding on a single or several congeneric species), and 0.15 individual of unknown host specificity. Large-seeded fruits with thin mesocarp tended to host specialist species whereas those with thick, fleshy mesocarp were often infested with both specialists and generalists. Weevils tended to avoid small-seeded, fleshy fruits. The low incidence of seed damage (3% of seeds) suggests that weevils are unlikely to play a major role in regulating plant populations via density-dependent mortality processes outlined by the Janzen–Connell hypothesis.

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Fernandez, Juan Manuel, Luz Thomann, Blas Fandiño, Rodrigo Cajade, and Alejandra Hernando. "An annotated checklist of birds of Paraje Tres Cerros, Corrientes province, Argentina." Check List 17, no. 2 (March 8, 2021): 415–43. http://dx.doi.org/10.15560/17.2.415.

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We provide an updated checklist of birds of a unique landscape in northeastern Argentina, which is characterized by three isolated, rocky outcrops and their surrounding agroecosystem. We recorded 188 bird species, including nine that are globally or nationally threatened. We highlight the presence of several grassland-specialist birds of conservation concern. Of the species recorded, 80.6% are residents and 17.7% are migrants. The heterogeneity of the landscape and its structural complexity accounts the existence of a high avian species diversity, which includes both generalists and specialists. This study confirms the conservation value of this ecosystem, due both to the rocky outcrops and grassland matrix. Grasslands are one of the most threatened biomes in the world.

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Klimaszewski, Jan, David W. Langor, Timothy T. Work, Georges Pelletier, HE James Hammond, and Carole Germain. "The effects of patch harvesting and site preparation on ground beetles (Coleoptera, Carabidae) in yellow birch dominated forests of southeastern Quebec." Canadian Journal of Forest Research 35, no. 11 (November 1, 2005): 2616–28. http://dx.doi.org/10.1139/x05-170.

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We studied the impacts of increasing size and number of gapcuts and the effects of site preparation by scarification on the species richness and community composition of ground beetles (Coleoptera: Carabidae), using pitfall traps in early-successional yellow birch dominated forests in eastern Canada. Catches of all carabids, forest specialists, and generalists were generally higher in uncut controls than in treatments. The catch of open-habitat specialists was generally lower in controls than in treatments. Although not significant, there was a common trend for scarification to decrease the catches of forest specialists and generalists. BrayCurtis similarity measures and nonmetric multidimensional scaling ordination indicated that the composition of the carabid assemblage was more affected by harvesting treatment than by scarification. Carabid species composition varied consistently with increasing gap size and corresponded to the a priori generalized habitat-preference designations. Forest-specialist species were confined to uncut sites, while generalist species were widely distributed across all sites. Open-habitat species were found predominantly in clear-cut and two-gap sites. Hygrophilous species were consistently associated with two-gap, four-gap, and clear-cut sites. Small-gap harvesting is more favorable to the maintenance of the structure of natural arthropod assemblages than are traditional, larger clearcuts.

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Kumar, Mayank, Ruchika Bharti, and Tushar Ranjan. "The Evolutionary Significance of Generalist Viruses with Special Emphasis on Plant Viruses and their Hosts." Open Virology Journal 14, no. 1 (December 31, 2020): 22–29. http://dx.doi.org/10.2174/1874357902014010022.

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The host range of a virus is defined as the number of species a virus potentially infects. The specialist virus infects one or few related species while the generalist virus infects several different species, possibly in different families. Origin of generalist viruses from their specialist nature and the expansion of the host range of the generalist virus occur with the host shift event in which the virus encounters and adapts to a new host. Host shift events have resulted in the majority of the newly emerging viral diseases. This review discusses the advantages and disadvantages of generalist over specialist viruses and the unique features of plant viruses and their hosts that result in a higher incidence of generalist viruses in plants.

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KACI-CHAOUCH, T., O. VERNEAU, and Y. DESDEVISES. "Host specificity is linked to intraspecific variability in the genus Lamellodiscus (Monogenea)." Parasitology 135, no. 5 (April 8, 2008): 607–16. http://dx.doi.org/10.1017/s003118200800437x.

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SUMMARYWe investigated whether host specificity is linked to variability within species of Lamellodiscus monogeneans, which are gill ectoparasites of the Sparidae. We sampled fish parasites in the northeastern part of the Mediterranean Sea: 4 specialist species, using 1 single host species, and 3 generalist species, using 2 distinct host species. Intraspecific variability was assessed from 2 different datasets. Morphometric variability of the attachment organ, called the haptor, was estimated first from measurements of several sclerified haptoral parts on 102 individuals. Genetic variability was calculated based on comparisons of sequences derived from the first internal transcribed spacer (ITS-1) of nuclear ribosomal DNA of 62 individuals. Morphometric variances in the specialist versus generalist species were compared via principal component analysis and F-tests, and uncorrected genetic distances (p-distances) were estimated within each species. We showed that the inter-individual variance of morphometric characters, as well as p-distances, are clearly greater within generalist species than specialist ones. These findings suggest that a relative increase in morphological and molecular variability enhances the possibility to colonize new host species in monogeneans, and supports the hypothesis that intraspecific variability could be a potential determinant of host specificity.

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Horsák, Michal, Michal Hájek, Daniel Spitale, Petra Hájková, Daniel Dítě, and Jeffrey C. Nekola. "The age of island-like habitats impacts habitat specialist species richness." Ecology 93, no. 5 (May 2012): 1106–14. http://dx.doi.org/10.1890/0012-9658-93.5.1106.

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Evangelista, Paul H., Sunil Kumar, Thomas J. Stohlgren, Catherine S. Jarnevich, Alycia W. Crall, John B. Norman III, and David T. Barnett. "Modelling invasion for a habitat generalist and a specialist plant species." Diversity and Distributions 14, no. 5 (September 2008): 808–17. http://dx.doi.org/10.1111/j.1472-4642.2008.00486.x.

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Krishna, Shivani, and Hema Somanathan. "Spatiotemporal strategies that facilitate recruitment in a habitat specialist tree species." AoB Plants 8 (2016): plw033. http://dx.doi.org/10.1093/aobpla/plw033.

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Ondine, Filippi-Codaccioni, Clobert Jean, and Julliard Romain. "Effects of organic and soil conservation management on specialist bird species." Agriculture, Ecosystems & Environment 129, no. 1-3 (January 2009): 140–43. http://dx.doi.org/10.1016/j.agee.2008.08.004.

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Cane, James H., Dale R. Gardner, and Melissa Weber. "Neurotoxic alkaloid in pollen and nectar excludes generalist bees from foraging at death-camas, Toxicoscordion paniculatum (Melanthiaceae)." Biological Journal of the Linnean Society 131, no. 4 (October 30, 2020): 927–35. http://dx.doi.org/10.1093/biolinnean/blaa159.

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Abstract Many plants produce broadly active toxins to which specialist herbivores—typically insects—have evolved counter-adaptations, sometimes spawning co-evolutionary arms races. Many non-social bee species are likewise taxonomic host specialists, but the specialists’ pollen hosts frequently attract diverse floral generalists as well, even to flowers of plants that are otherwise chemically defended. In this study of foothills death-camas, Toxicoscordion paniculatum (Nutt.) Rydberg (formerly Zigadenus), we show that its pollen and nectar both contain zygacine, the steroidal alkaloid responsible for this plant’s notorious mammalian toxicity. Hungry naïve adults of a generalist solitary bee, Osmia lignaria Say (Megachilidae), would briefly drink death-camas nectar or biologically relevant doses of zygacine in syrup, followed by prolonged bouts of irritable tongue grooming; many became paralyzed and some even died. Larvae fed dosed provision masses likewise often ceased feeding and sometimes died. Prolonged irritation and subsequent deterrence of foraging O. lignaria likely illustrates why it and 50+ other vernal bee species were absent from death-camas flowers in a five-state survey. The sole visiting bee, Andrena astragali, foraged exclusively at death-camas flowers for pollen and nectar. Thus, a toxic alkaloid found in death-camas pollen and nectar deters generalist bees from flowers of this pollinator-dependent monocot, restricting visitation to a single specialist bee that tolerates death-camas toxins and is its likely pollinator.

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Henke-von der Malsburg, Johanna, and Claudia Fichtel. "Are generalists more innovative than specialists? A comparison of innovative abilities in two wild sympatric mouse lemur species." Royal Society Open Science 5, no. 8 (August 2018): 180480. http://dx.doi.org/10.1098/rsos.180480.

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The propensity to flexibly innovate behavioural variants might advantage animals when dealing with novel or modified ecological or social challenges. Interspecific innovative abilities can be predicted by the degree of ecological generalism and intraspecific variation is predicted by personality traits. To examine the effects of these factors on innovation, we compared problem-solving abilities in the generalist grey mouse lemurs ( Microcebus murinus ) and the more specialized Madame Berthe's mouse lemurs ( Microcebus berthae ) in western Madagascar. We examined personality traits by testing 54 individuals in open field and novel object tests, and we assessed problem-solving abilities by presenting an artificial feeding-box that could be opened by three different techniques. The first two techniques presented novel problems and the third technique a modified problem to the more complex second novel problem. In both species, motivation, early success and better inhibitory control characterized innovators and predicted superior problem-solving performance. Although both species performed equally well in finding a solution to the novel problems, the specialist species was more efficient in finding a novel solution to a familiar problem. Since the ecological specialist also exhibited more inhibitory control in this task than the generalist, we propose that specialists may dispose of more efficient problem-solving behaviour.

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Wood, KA. "Bird assemblages in a small public reserve and adjacent residental area at Wollongong." Wildlife Research 23, no. 5 (1996): 605. http://dx.doi.org/10.1071/wr9960605.

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A total of 8262 birds of 57 species was counted in a degraded public reserve and adjacent residential area during 61 paired transects in 1990. Most of the reserve was remnant wet sclerophyll forest (5 ha) and subtropical rainforest (0.4 ha), whereas a variety of mature native and introduced trees and shrubs were present in the 55-year-old suburb. Species evenness was similar in the habitats of the reserve and residental area but not species richness, number of individuals or composition of the avifauna. In all seasons, the reserve was richer in species but poorer in absolute numbers of birds. Thirteen native species were reserve specialists, six species (five introduced) were suburb specialists and 17 species showed only slight habitat preference. Excluding silvereyes, which showed little preference for either habitat, there were twice as many regularly occurring species that preferred to use the reserve rather than the residential area but only half the number of individuals. Nine specialist species are at risk of local extinction because their populations in the reserve are critically small [range: 80 (brown gerygone, Gerygone mouki) to 5 birds (eastern whipbird, Psophodes olivaceus)]. Seventeen species have become locally extinct since Europeans arrived in 1816. Conservation of the avifauna is discussed.

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Woinarski, J. C. Z., Hanna Reichel, and A. N. Andersen. "The distribution of ants on the Wessel and English Company Islands, in the seasonal tropics of Australia’s Northern Territory." Australian Journal of Zoology 46, no. 6 (1998): 557. http://dx.doi.org/10.1071/zo98012.

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A total of 74 ant species (from 23 genera) was recorded from 195 quadrats (50 × 50 m) from 39 continental islands off Arnhem Land, Northern Territory. In general, the ant fauna comprised generalist species widespread on the north Australian mainland. The functional group composition was also comparable to that of similar environments on the north Australian mainland. The ant fauna was not tightly structured. There were few habitat specialists, no species showed a clear preference for smaller islands, and only a few species showed unequivocal preferences for larger islands. There were no clear cases of congeneric, or otherwise ecologically similar, species replacing each other on different islands. In contrast to the north Australian mainland, there were no significant differences between habitats in ant species richness. However, the functional group composition varied significantly between the eight main habitats sampled across the islands, in a manner consistent with that reported for the mainland. The number of ant species recorded per island was most closely related to island size (80% of the deviance explained), but there was only slight or no relationship between island size and the number of species at the quadrat scale. Functional group composition varied between islands, with small islands supporting a relatively high proportion of Generalised Myrmicinae species. Low-lying (and presumably intermittently inundated) islands supported a higher proportion of Dominant Dolichoderinae and few Specialist Predators and Tropical Climate Specialist species. Very small islands supported a relatively high proportion of Dominant Dolichoderinae species. These differences are largely attributable to inter-island differences in habitat availability and disturbance regimes, and to differences between functional groups in dispersability, competitive ability and ecological flexibility. Species richness was little influenced by the extent of island isolation. Patterning in the ant fauna of these islands parallels that reported for islands elsewhere.

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Park, A. W., M. J. Farrell, J. P. Schmidt, S. Huang, T. A. Dallas, P. Pappalardo, J. M. Drake, et al. "Characterizing the phylogenetic specialism–generalism spectrum of mammal parasites." Proceedings of the Royal Society B: Biological Sciences 285, no. 1874 (March 7, 2018): 20172613. http://dx.doi.org/10.1098/rspb.2017.2613.

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The distribution of parasites across mammalian hosts is complex and represents a differential ability or opportunity to infect different host species. Here, we take a macroecological approach to investigate factors influencing why some parasites show a tendency to infect species widely distributed in the host phylogeny (phylogenetic generalism) while others infect only closely related hosts. Using a database on over 1400 parasite species that have been documented to infect up to 69 terrestrial mammal host species, we characterize the phylogenetic generalism of parasites using standard effect sizes for three metrics: mean pairwise phylogenetic distance (PD), maximum PD and phylogenetic aggregation. We identify a trend towards phylogenetic specialism, though statistically host relatedness is most often equivalent to that expected from a random sample of host species. Bacteria and arthropod parasites are typically the most generalist, viruses and helminths exhibit intermediate generalism, and protozoa are on average the most specialist. While viruses and helminths have similar mean pairwise PD on average, the viruses exhibit higher variation as a group. Close-contact transmission is the transmission mode most associated with specialism. Most parasites exhibiting phylogenetic aggregation (associating with discrete groups of species dispersed across the host phylogeny) are helminths and viruses.

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Socolar, Jacob B., and David S. Wilcove. "Forest-type specialization strongly predicts avian responses to tropical agriculture." Proceedings of the Royal Society B: Biological Sciences 286, no. 1913 (October 23, 2019): 20191724. http://dx.doi.org/10.1098/rspb.2019.1724.

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Species’ traits influence how populations respond to land-use change. However, even in well-characterized groups such as birds, widely studied traits explain only a modest proportion of the variance in response across species. Here, we show that associations with particular forest types strongly predict the sensitivity of forest-dwelling Amazonian birds to agriculture. Incorporating these fine-scale habitat associations into models of population response dramatically improves predictive performance and markedly outperforms the functional traits that commonly appear in similar analyses. Moreover, by identifying habitat features that support assemblages of unusually sensitive habitat-specialist species, our model furnishes straightforward conservation recommendations. In Amazonia, species that specialize on forests along a soil–nutrient gradient (i.e. both rich-soil specialists and poor-soil specialists) are exceptionally sensitive to agriculture, whereas species that specialize on floodplain forests are unusually insensitive. Thus, habitat specialization per se does not predict disturbance sensitivity, but particular habitat associations do. A focus on conserving specific habitats that harbour highly sensitive avifaunas (e.g. poor-soil forest) would protect a critically threatened component of regional biodiversity. We present a conceptual model to explain the divergent responses of habitat specialists in the different habitats, and we suggest that similar patterns and conservation opportunities probably exist for other taxa and regions.

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Infante, Sergio Díaz, Carlos Lara, and María del Coro Arizmendi. "Land-Use Change in a Mexican Dry Forest Promotes Species Turnover and Increases Nestedness in Plant-Hummingbird Networks: Are Exotic Plants Taking Over?" Tropical Conservation Science 13 (January 2020): 194008292097895. http://dx.doi.org/10.1177/1940082920978952.

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Background Despite the increasing knowledge of plant-pollinator interaction networks, the effects of human-induced disturbances on them have barely been studied. We analyzed whether land-use changes modified the structure and topology of plant-hummingbird interaction networks or promoted the integration of exotic plant species. Methods Fieldwork was carried out in two vegetation areas in Mexico: a protected tropical dry forest and nearby disturbed sites. For two years we registered hummingbird-plant interactions monthly in each area. Then, we constructed interaction matrices from these data and compared their assemblage structure. Results The conversion of original dry forest to disturbed habitats impacted some assemblage attributes of the plant-hummingbird network. In the disturbed sites, there were more plant species, mainly exotics, and one additional hummingbird species. Most network attributes remained the same except niche width and nestedness (pattern of interactions where generalists and specialists tend to interact with generalists whereas specialist-to-specialist interactions are infrequent), which were higher in the disturbed network. The generalist core in the disturbed network contained half of the core species in the conserved network. Implications for conservation Exotic plants that strongly integrated into the disturbed network may exert a large influence on network dynamics in these areas. Identifying the interacting species and their role provides valuable insights for their conservation and protection. Hummingbirds attracting native plant species have a potential for practical or ornamental use, and hummingbirds presence in human-modified landscapes not only provides positive aesthetic value to people but can additionally contribute to conserving native plants and the biodiversity associated with them.

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Journal articles on the topic 'Specialist species'

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