Academic literature on the topic 'Oniscidae Classification'

A significant diversity of terrestrial oniscidean isopods was recently discovered in the subterranean ‘calcrete islands’ of Western Australia, but the species and higher-level systematic status of much of the fauna are currently uncertain. Here we focus on one group of species that was initially assigned to the genus Trichorhina (Platyarthridae), based on several shared characters, and investigate the phylogenetic relationships of these species to 21 oniscidean genera, including 13 known families, using 18S rDNA sequence data. We then present phylogenetic analyses using 28S-only and combined 18S, 28S rDNA and mitochondrial cytochrome c oxidase subunit I (COI) data for a more restricted sampling of taxa, and present results for a detailed morphological study of the antennae and other cephalic structures of exemplar taxa. Bayesian and maximum likelihood analyses of the extended 18S-only, the 28S-only and multi-gene datasets provide strong evidence for a distinct well-supported monophyletic group comprising the new Western Australian and one South American taxon. This clade is unrelated to all included members of Platyarthridae, which appears to be polyphyletic, and it forms a distinct group relative to other oniscidean families. Given these findings and the results of the morphological study, a new southern hemisphere oniscidean family, Paraplatyarthridae Javidkar & King, fam. nov. is erected based on Paraplatyarthrus subterraneus Javidkar & King, gen. & sp. nov. (type genus and species), and several undescribed taxa which occur in the arid (terrestrial and subterranean) regions of Western Australia and subtropical South America. Paraplatyarthridae is distinguishable from all other oniscidian families on a combination of character states including, among others, the presence of fan-like scale setae on the dorsal body, and the ventral second antenna with leaf-like scale setae and a furrow containing elongated hair-like capillary setae that form part of a water conducting system unique within Oniscidea. This study has important implications for the higher-level classification of oniscidean crustaceans and points to the need for a more detailed molecular phylogeny that includes a comprehensive sampling of southern hemisphere taxa.

Fusarium solani, a soil-borne pathogen of stored potato may be disseminated, and thus, the damage caused by the pathogen may be aggravated by the grazing activities of arthropods. To investigate whether terrestrial woodlice contribute to the spread or, instead, to the control of F. solani, we launched a series of pilot experiments. First, a laboratory feeding trial was set up to find whether and to what extent woodlice consume the mycelia of fungal pathogens, namely, Aspergillus niger, F. solani, Macrophomina phaseolina, and Sclerotinia sclerotiorum. This was followed by a second set of experiments to simulate storage conditions where potato tubers, either healthy or infected with F. solani, were offered to woodlice. We found that: (1) F. solani was accepted by woodlice but was not their most preferred food source; (2) the presence of woodlice reduced the spread of F. solani among potato tubers. Our results suggest that the classification of terrestrial woodlice as “storage pests” needs re-evaluation, as isopods have the potential to disinoculate infective plant remnants and, thus, reduce the spread of storage pathogens.

The history of the systematics of isopod suborders is summarised. Several authors have suggested that the traditional suborder Flabellifera is paraphyletic and includes one or more of the suborders Gnathiidea, Epicaridea and Anthuridea. Two suborders, Cymothoida and Sphaeromatidea, have been proposed as replacement taxa for the Flabellifera, but it has not been possible on the basis of phylogenetic analyses to elucidate significant relationships between the suborders and families. Morphological characters are used to explore relationships between 35 genus-, family- and suborder-level taxa of flabelliferan Isopoda in a cladistic analysis (using Phreatoicidea and Asellota as outgroups) and to derive a new classification. The analysis did not find a synapomorphy for 'Flabellifera' sensu lato, but recognises two diverging clades of 'long-tailed' isopods. Members of the Oniscidea are not part of either clade. Nor are the Tainisopidea, a new suborder erected for members of the family Tainisopidae. The Tainisopidea has many synapomorphies and plesiomorphic features, but does not share characters with either clade. The first clade comprises Phoratopidea (for Phoratopus remex) and sister-taxa Cymothoida and Limnoriidea. Representatives of these suborders have uropodal rami ventral to the pleotelson and articulating from side-to-side inside the branchial space. The new suborder, Phoratopidea, is for one species with unique, broad articles of pereopods 3 and 4 with reduced dactyls. It lacks the synapomorphies of the following two suborders. In members of the suborder Cymothoida, the mandibular molar is either a flat triangular blade, reduced to a conical process, or absent, and the maxillipedal endite is rarely longer than palp article 1 (or is absent), distally tapering and has few setae. The suborder Limnoriidea is diagnosed as lacking the mandibular molar, and the non-tapering, slender (except in Keuphylia) maxillipedal endite reaches to at least the distal margin of palp article 4. Members of the second clade share a vaulted pleotelson enclosing a branchial chamber defined by ventrolateral ridges and uropods lateral to the pleotelson margin that fold down alongside the branchial space. It comprises two suborders. Members of the Sphaeromatidea have pleonite 1 much narrower than pleonite 2 and a reduced (or absent) right lacinia mobilis fused to the spine row. They lack operculiform uropods, which characterise Valvifera. The suborder Anthuridea is reduced to superfamily rank and Epicaridea is reduced to two superfamilies within Cymothoida. Unambiguous relationships between most families are resolved, but Sphaeromatidae is suspected to be paraphyletic, Paravireia is placed as the most plesiomorphic of the Sphaeromatoidea and a new family, Basserolidae, is proposed. The Tainisopidea includes freshwater taxa in a relictual environment. The sole species of Phoratopidea is marine, rare, and its ecology is unknown. The Cymothoida are most diverse in tropical regions. Members of the most plesiomorphic family, the Cirolanidae, are mobile predators or scavengers and the more derived families are ectoparasites on fishes and other crustaceans. Members of the Limnoriidea are mainly tropical and at least one family is herbivorous. The Valvifera and Sphaeromatidea are benthic, with respiratory pleopods in a branchial chamber. They are most diverse in the temperate southern hemisphere, and most are detritivores.

Abstract Background The sky-island Ligidium species fauna in southwest China is poorly known. Before this study, six of the seven sky-island species of the genus were known to be endemic to southwest China. In morphology, Ligidium species are often difficult to identify, and an appraisal of integrative taxonomy is needed. Results We integrated morphology and molecular analyses to delimit Ligidium species. Molecular species delimitation based on distance- and evolutionary models recovered seven-candidate lineages from five gene markers (COI, 12S rRNA, 18S rRNA, 28S rRNA and NAK). We also estimated that the species divergences of sky-island Ligidium in southwest China started in late Eocene (40.97 Mya) to middle Miocene (15.19 Mya). Four new species (L. duospinatum Li, sp. nov., L. acuminatum Li, sp. nov., L. rotundum Li, sp. nov. and L. tridentatum Li, sp. nov.) are described. Morphological confusion among L. denticulatum Shen, 1949, L. inerme Nunomura & Xie, 2000 and L. sichuanense Nunomura, 2002 is clarified by integrative taxonomy. Conclusion This work confirms that an integrative approach to Ligidium taxonomy is fundamental for objective classification, and deduced the uplift of Qinghai-Tibetan Plateau in the late Eocene and middle Miocene as one of the principal reasons for the species divergences of sky-island Ligidium in southwest China. We also inferred that sky-island mountains have a huge reserve of higher Ligidium species diversity.

This thesis examines terrestrial isopod (Crustacea: Oniscidea) diversity and biogeography from south-western Australia, a region already recognised for the exceptional high biodiversity and concentrations of endemic species. A taxonomic investigation of isopods in the Western Australian Museum and material collected systematically as part of this study revealed seventy taxa, sixty of which were considered native species. The thesis provides a comprehensive review of regional taxonomic history and includes a key, complete with a set of forty characters states and taxa, illustrated by a number of photographic plates that are designed for use by specialists and non-specialists alike. Prior to this study all the region's indigenous terrestrial isopods were poorly described and, while many taxa are still to be resolved at the species level, it appears at least 35 species are new to science. The distributions of indigenous taxa form some clear and consistent biogeographical patterns. Distributions of taxa are influenced by steep rainfall gradients, the seasonality of rainfall and by biophysical characteristics of the landscape including, localised landforms and differing microhabitat utilisation. The region is one of high diversity, with both widely distributed species and highly localised endemics. Two areas, the Perth region of the Swan Coastal Plain and the tall, wet southern forests, are particularly species rich. Beta diversity is also high. This reflects a heterogeneous landscape with profound differences in microhabitat availability, differences often due to recent exogenous disturbance. The construction of a biogeographic model showed a major fauna/ break, which created northern and southern bioregions to which 68% of the taxa were endemic. This biogeographical boundary is significant in that it had not been recognised in any previous biogeographical schemes. Data derived from the analysis of soil, leaf litter and log microhabitat samples show that the existence of terrestrial isopods in south-western Australia is intractably related to organic matter. The geographical range of species is often best explained by the types of microhabitat utilised and their degree of moisture dependency. The wetter forests of the region contain relictual short range endemics reliant upon surface organic matter, particularly leaf litter. Moisture is clearly a limiting factor in the distribution of all species. The five most common genera can be differentiated by their dependence upon different moisture regimes in a range of microhabitat types. The spatial and temporal continuity of different types of organic matter in forested landscapes is considered critical to the conservation of the group in south-Western Australia. Land management practices, such as logging and burning, which influence the nature and distribution of organic matter, are likely to induce profound changes in terrestrial isopod communities. Regular and broadscale prescription burning and the increasing scarcity of large and decayed logs are considered to be a primary threat to their conservation status. Hypotheses involving the historical role of surface organic matter are developed to explain the speciation patterns of the group in the region. In order to test these models, and to provide an urgently needed assessment of the conservation status of relictual forest invertebrates, clear taxonomic priorities are recommended.