Phylogeography and taxonomy of Coleonyx elegans Gray 1845 (Squamata: Eublepharidae) in Mesoamerica: The Isthmus of Tehuantepec as an environmental barrier.

Population divergence leading to speciation is often explained by physical barriers causing allopatric distributions of historically connected populations. Environmental barriers have increasingly been shown to cause population divergence through local adaptation to distinct ecological characteristics. In this study, we evaluate population structuring and phylogeographic history within the Yucatán banded gecko Coleonyx elegans Gray 1845 to assess the role of both physical and environmental barriers in shaping the spatio-genetic distribution of a Mesoamerican tropical forest taxon. We generated RADseq and multi-locus Sanger datasets that included sampling across the entire species' range. Results find support for two distinct evolutionary lineages that diverged during the late Pliocene and show recent population expansions. Furthermore, these genetic lineages largely align with subspecies boundaries defined by morphology. Several mountain ranges identified as phylogeographic barriers in other taxa act as physical barriers to gene flow between the two clades. Despite the absence of a physical barrier between lineages across the lowland Isthmus of Tehuantepec, no introgression was observed. Here, a steep environmental cline associated with seasonality of precipitation corresponds exactly with the distributional limits of the lineages, whose closest samples are only 30 km apart. The combination of molecular and environmental evidence, and in conjunction with previous morphological evidence, allows us to reassess the current taxonomy in an integrative framework. Based on our findings, we elevate the previously recognized subspecies from the Pacific versant, the Colima banded gecko C. nemoralis Klauber 1945, to full species status and comment on conservation implications.

All in all its just another branch in the tree: A new species of Acanthocercus Fitzinger, 1843 (Squamata: Agamidae), from Angola.

Recent integrative taxonomic studies of the agamid genus Acanthocercus Fitzinger, 1843 have shown that Angola harbors three different taxa, all within the Acanthocercus atricollis (Smith, 1849) species complexA. cyanocephalus (Falk, 1925) in the northeastern parts of the country, A. margaritae Wagner et al. 2021 in the southern regions, and an unnamed species in the central and northwestern parts of Angola. Using the previously published molecular data as evidence of phylogenetic support and newly collected morphological, meristic and coloration data, we here describe this unnamed lineage as a new species. The new species is morphologically very similar to A. cyanocephalus, but it can easily be differentiated from the latter by the coloration pattern of displaying males, with a blue coloration restricted to the head region, and by its inferior scale counts compared to other species of the A. atricollis complex group. As reported in other studies in this group, male breeding coloration is an effective trait for diagnosing these morphologically conserved species. This description raises the number of Acanthocercus species recognized to 15 and is another contribution revealing the rich but still incompletely described herpetological diversity of Angola.

Geographic variation in morphology in the Mohave Rattlesnake (Crotalus scutulatus Kennicott 1861) (Serpentes: Viperidae): implications for species boundaries.

The Mohave Rattlesnake (Crotalus scutulatus) is a highly venomous pitviper inhabiting the arid interior deserts, grasslands, and savannas of western North America. Currently two subspecies are recognized: the Northern Mohave Rattlesnake (C. s. scutulatus) ranging from southern California to the southern Central Mexican Plateau, and the Huamantla Rattlesnake (C. s. salvini) from the region of Tlaxcala, Veracruz, and Puebla in south-central Mexico. Although recent studies have demonstrated extensive geographic variation in venom composition and cryptic genetic diversity in this species, no modern studies have focused on geographic variation in morphology. Here we analyzed a series of qualitative, meristic, and morphometric traits from 347 specimens of C. scutulatus and show that this species is phenotypically cohesive without discrete subgroups, and that morphology follows a continuous cline in primarily color pattern and meristic traits across the major axis of its expansive distribution. Interpreted in the context of previously published molecular evidence, our morphological analyses suggest that multiple episodes of isolation and secondary contact among metapopulations during the Pleistocene were sufficient to produce distinctive genetic populations, which have since experienced gene flow to produce clinal variation in phenotypes without discrete or diagnosable distinctions among these original populations. For taxonomic purposes, we recommend that C. scutulatus be retained as a single species, although it is possible that C. s. salvini, which is morphologically the most distinctive population, could represent a peripheral isolate in the initial stages of speciation.

Spatial distribution of epibionts on olive ridley sea turtles at Playa Ostional, Costa Rica.

There is a wealth of published information on the epibiont communities of sea turtles, yet many of these studies have exclusively sampled epibionts found only on the carapace. Considering that epibionts may be found on almost all body-surfaces and that it is highly plausible to expect different regions of the body to host distinct epibiont taxa, there is a need for quantitative information on the spatial variation of epibiont communities on turtles. To achieve this, we measured how total epibiont abundance and biomass on olive ridley turtles Lepidochelys olivacea varies among four body-areas of the hosts (n = 30). We showed that epibiont loads on olive ridleys are higher, both in terms of number and biomass, on the skin than they are on the carapace or plastron. This contrasts with previous findings for other hard-shelled sea turtles, where epibionts are usually more abundant on the carapace or plastron. Moreover, the arguably most ubiquitous epibiont taxon for other hard-shelled sea turtles, the barnacle Chelonibia spp., only occurred in relatively low numbers on olive ridleys and the barnacles Stomatolepas elegans and Platylepas hexastylos are far more abundant. We postulate that these differences between the epibiont communities of different sea turtle taxa could indicate that the carapaces of olive ridley turtles provide a more challenging substratum for epibionts than do the hard shells of other sea turtles. In addition, we conclude that it is important to conduct full body surveys when attempting to produce a holistic qualitative or quantitative characterization of the epibiont communities of sea turtles.