Academic literature on the topic 'Lizards – Classification'

The Liolaemidae lizard evolutionary radiation has resulted from active spatial expansions into an extensive territorial area accompanied by active events of cladogenesis that have produced high levels of taxonomic and ecological diversity, especially within the Liolaemus genus. As a result, these lizards have been for decades the subject of intense taxonomic and systematic debates. Here, I provide an analysis of a recent paper where discussions on Liolaemidae diversity and classification involved biased and arbitrary interpretations and observations of two previously published monographs.

Although tropical forest birds are known to prey upon small lizards and frogs, no study has documented the attributes of vertebrate-eating birds or whether birds prey opportunistically on the different elements of the herpetofauna within tropical communities. This study is based on a 14-mo investigation on avian diet, supplemented with a 3-y census of frogs and a 1-y census of lizards in a humid forest of central Panama. From 91 bird species, 1086 regurgitates were collected, in which were found 75 lizards and 53 frogs. Over 50% of the common, primarily insectivorous bird species preyed upon lizards or frogs, with a mean frequency of 0.26 prey/sample. These birds (22 species, nine families) foraged on various substrates from different strata of the forest, fed on invertebrates averaging from 3.3 to 17.2 mm in length, weighed from 11 to 195 g, and had bill lengths that varied from 12.2 to 49.8 mm. Based on a logistic regression analysis, intensity of foraging at army-ant swarms was the variable that best explained the likelihood that a bird species preyed upon lizards, leading to a classification that was 91% correct. In contrast, bill length and body length classified correctly 88% of the frog-eating birds, which showed a fairly constant 1:7 bill length/body length ratio (as opposed to a mean but highly variable 1:10 ratio in other species). A multiple regression analysis showed that seasonal variation in intensity of lizard predation was positively related to arthropod abundance except during the breeding season when lizard intake decreased, presumably because nesting birds did not follow ant swarms. Intensity of frog predation correlated with frog abundance over time, the latter being inversely related to arthropod availability. Ninety-seven per cent of all lizards and frogs identified in the diet samples (n = 105) were from two genera, Anolis and Eleutherodactylus, respectively. Prey size distribution in the regurgitates suggested an optimal prey size of 33.5 mm snout-vent length (SVL) for lizards and 14.5 mm SVL for frogs. Birds preyed opportunistically on the different Anolis species, but almost exclusively upon juvenile individuals. Abundances of the different Eleutherodactylus species correlated with their predation rates, but these frogs represented only 10% of all the frogs observed during the censuses. The two most common local anurans, Colostethus flotator and Bufo typhonius, were not taken by any bird species.

Lizards of the family Diploglossidae occur in moist, tropical forests of Middle America, South America, and Caribbean islands. Our analyses based on new molecular and morphological data indicate that the widely distributed genera Celestus Gray, 1839 and Diploglossus Wiegmann, 1834 are paraphyletic. We restrict the former to Caribbean islands and the latter to South America and Caribbean islands. We assign species in Middle America, formerly placed in Celestus and Diploglossus, to Advenus gen. nov., Mesoamericus gen. nov., and Siderolamprus Cope, 1861. We assign species on Caribbean islands, formerly placed in Celestus, to Caribicus gen. nov., Comptus gen. nov., Celestus, Panolopus Cope, 1862, Sauresia Gray, 1852, and Wetmorena Cochran, 1927. Our phylogenetic tree supports three major clades in the family: Celestinae subfam. nov. (Advenus gen. nov., Caribicus gen. nov., Comptus gen. nov., Celestus, Panolopus, Sauresia, and Wetmorena), Diploglossinae (Diploglossus and Ophiodes Wagler, 1828), and Siderolamprinae subfam. nov. (Mesoamericus gen. nov. and Siderolamprus). Our timetree indicates that the diploglossid lineage originated in the early Cenozoic and established three major centers of diversification in the Americas: Middle America (siderolamprines and one celestine), South America (diploglossines), and Caribbean islands (celestines and diploglossines). The majority of threatened species are on Caribbean islands, with the major threats being deforestation and predation by the introduced mongoose. Molecular and morphological data indicate that there are many undescribed species in this family of lizards.

In this essay, we review concepts of taxonomic categories of anoles, reanalyze accumulated characteristics of these lizards,use these analyses to summarize the topology of the phylogenetic tree for anoles, and use consistent major branches ofthis topology to recommend a classification scheme for this large group of squamates. We then use this new taxonomy todraw inferences about the evolution of habitat use, as well as the geologic ages and geographic distribution of anolelineages. Our taxonomy eliminates problems of paraphyly inherent in previous classifications by elevating eight majorlineages to generic status (Anolis, Audantia, Chamaelinorops, Ctenonotus, Dactyloa, Deiroptyx, Norops, and Xiphosurus), providing diagnoses of those genera, and then doing the same for species groups within each genus. With the exceptionof 19 species, the contents of our generic categories are consistent with all recent phylogenetic reconstructions. Thus, therevised taxonomy appears to provide a stable classification for at least 95% of the 387 species currently recognized andincluded in our treatment of the group. We argue that these lizards originated in South America ~130 ma, where they werelarge in size and occupied niches focused on the canopy of rainforest trees. The radiation diverged into eight genera125–65 ma within a volcanic island arc that connected North and South America. This evolutionary diversificationgenerated three genera (Deiroptyx, Dactyloa, and Xiphosurus) that retained an ancestral large size and canopy niche focusand five genera (Anolis, Audantia, Chamaelinorops, Ctenonotus, and Norops) that became small, with niches focusedtoward the ground. The complicated divergence and accretion events that generated the current conformation of theAntillean islands, and eventually closed the Panamanian Portal, transported six island genera to their current centers ofdiversity (Anolis, Audantia, Chamaelinorops, Ctenonotus, Deiroptyx, and Xiphosurus), leaving two genera on themainland (Dactyloa and Norops). Our historical reconstruction makes Norops a much older radiation than previousreconstructions, allowing basal diversification of this species-rich lineage to occur on mainland terrains that eventuallyseparated from the mainland to become parts of Cuba and Jamaica. This early diversification extended into northern South America, where a basal lineage of Norops coevolved with Dactyloa prior to the mainland-island separation.

Synopsis The integrity of regional and local biological diversity is under siege as a result of multiple anthropogenic threats. The conversion of habitats, such as rain forests, into agricultural ecosystems, reduces the area available to support species populations. Rising temperatures and altered rainfall patterns lead to additional challenges for species. The ability of conservation biologists to ascertain the threats to a species requires data on changes in distribution, abundance, life history, and ecology. The International Union for the Conservation of Nature (IUCN) uses these data to appraise the extinction risk for a species. However, many species remain data deficient (DD) or unassessed. Here, I use 14 morphological traits related to locomotor function, habitat, and feeding to predict the threat status of over 400 species of lizards in the infraorder Iguania. Morphological traits are an ideal proxy for making inferences about a species’ risk of extinction. Patterns of morphological covariation have a known association with habitat use, foraging behavior, and physiological performance across multiple taxa. Results from phylogenetic general linear models revealed that limb lengths as well as head characters predicted extinction risk. In addition, I used an artificial neural network (ANN) technique to generate a classification function based on the morphological traits of species with an assigned IUCN threat status. The network approach identified eight morphological traits as predictors of extinction risk, which included head and limb characters. The best supported model had a classification accuracy of 87.4%. Moreover, the ANN model predicted >18% of DD/not assessed species were at risk of extinction. The predicted assessments were supported by other sources of threat status, for example, Convention on International Trade in Endangered Species appendices. Because of the functional link between morphology, performance, and ecology, an ecomorphological approach may be a useful tool for rapid assessment of DD or poorly known species.

We provide a critical review of a recent taxonomic revision of Chilean Liolaemus lizards (Iguania: Liolaemidae) by Pincheira-Donoso and Núñez (2005) and a recent paper (PincheiraDonoso et al. 2008), which proposed several new taxonomic and phylogenetic arrangements. We document fundamental problems with many of the proposed taxonomic revisions in both publications, which if followed, could lead to serious taxonomic confusion. In Pincheira-Donoso and Núñez (2005) a subgeneric classification is erected, which was produced by outdated methods (phenetic analyses), cannot be replicated (no matrix is presented), and is taxonomically untenable (some of the subgenera are nested within other subgenera). Most of the taxonomic groups that are proposed have been previously proposed, albeit differently constituted, yet often previous research is not given attribution; when findings are different, the research of others is either overlooked or dismissed without comment. The diagnoses of species and subspecies (including several newly proposed taxa) are often written in an authoritative manner (without supporting data or information), making them insufficient for distinguishing the focal taxon from others belonging to the same group, finally leading to uncertainty regarding the validity of several of the newly proposed taxa, combinations, or synonymies. We also describe less egregious errors of omission and commission. In Pincheira-Donoso et al. (2008), most of the proposals follow the Pincheira-Donoso and Núñez (2005) revisions, some species are allocated to groups without consistent cladistic support and other proposed relationships are based on incomplete evidence from other studies dismissing the limitations of the arrangement. Critical species are not identified in a list of material examined. Finally, Pincheira-Donoso et al. (2008) present a somewhat outdated and biased discussion of the relative value of using molecules or morphology in systematics. In light of these limitations, and in an effort to stabilize and prevent further taxonomic confusion, we provide an updated phylogenetic classification of the currently recognized lizards of the family Liolaemidae (Ctenoblepharys, Liolaemus, and Phymaturus), which is based on a consensus of studies published since the first phylogenetic major revision of the clade in 1995.

An individual's sex depends upon its genes (genotypic sex determination or GSD) in birds and mammals, but reptiles are more complex: some species have GSD whereas in others, nest temperatures determine offspring sex (temperature-dependent sex determination). Previous studies suggested that montane scincid lizards ( Bassiana duperreyi , Scincidae) possess both of these systems simultaneously: offspring sex is determined by heteromorphic sex chromosomes (XX–XY system) in most natural nests, but sex ratio shifts suggest that temperatures override chromosomal sex in cool nests to generate phenotypically male offspring even from XX eggs. We now provide direct evidence that incubation temperatures can sex-reverse genotypically female offspring, using a DNA sex marker. Application of exogenous hormone to eggs also can sex-reverse offspring (oestradiol application produces XY as well as XX females). In conjunction with recent work on a distantly related lizard taxon, our study challenges the notion of a fundamental dichotomy between genetic and thermally determined sex determination, and hence the validity of current classification schemes for sex-determining systems in reptiles.

AbstractWe investigated life history characters of the Cape grass lizard, Cordylus anguinus, and relate them to survival in the fire-prone habitat in which it occurs. Unlike in other cordylids, reproductive activity was found to be asynchronous among females, with vitellogenic and gravid females encountered virtually throughout the year. Aseasonal breeding will circumvent reduction or complete loss of reproductive effort for any given year due to fire. Female grass-lizards attain significantly larger body sizes than males. Clutch size ranged from three to seventeen and was positively correlated with snout-vent length. Maximum clutch size is more than three times that recorded for any other cordylid. We suggest that high fecundity will allow quick recruitment after a fire. To determine the reproductive cycle exhibited by males, testicular volume and seminiferous tubule diameter were measured, and spermatogenic activity assessed qualitatively, using Licht's classification system. Our data indicate that C. anguinus has a post-nuptial spermatogenic cycle. The species differs from other cordylids having a post-nuptial cycle, in that spermatogenesis already commences in spring.