ABSTRACT
Morphological stasis is generally associated with relative constancy in ecological pressures throughout time, producing strong stabilizing selection that retains similar shared morphology. Although climate and vegetation are commonly the main key factors driving diversity and phenotypic diversification in terrestrial vertebrates, fossorial organisms have their morphology mostly defined by their fossorial lifestyle. Among these secretive fossorial organisms, blind snakes of the South American genus Amerotyphlops are considered poorly studied when compared to other taxa. Here, we evaluate the cryptic diversity of Amerotyphlops using phylogenetic and multivariate approaches. We based our phylogenetic analysis on a molecular dataset composed of 12 gene fragments (eight nuclear and four mitochondrial) for 109 species of Typhlopidae. The multivariate analysis was implemented using 36 morphological variables for 377 specimens of Amerotyphlops. Additionally, we contrast our phylogenetic result with the morphological variation found in cranial, external and hemipenial traits. Our phylogenetic results recovered with strong support the following monophyletic groups within Amerotyphlops: (1) a clade formed by A. tasymicris and A. minuisquamus; (2) a clade composed of A. reticulatus; (3) a north-eastern Brazilian clade including A. yonenagae, A. arenensis, A. paucisquamus and A. amoipira; and (4) a clade composed of A. brongersmianus and a complex of cryptic species. Based on these results we describe four new species of Amerotyphlops from north-eastern and south-eastern Brazil, which can be distinguished from the morphologically similar species, A. brongersmianus and A. arenensis.
ABSTRACT
Typhlopidae is the most diverse family of Scolecophidia, with 269 species. Amerotyphlops was recently erected within subfamily Typhlopinae and comprises fifteen species distributed from Mexico to Argentina and the southern Lesser Antilles. Despite recent advances, affinities among typhlopines remain poorly explored, and the phylogenetic relationships and morphology of the South American (SA) species were never accessed before. Here, we performed a phylogenetic analysis including 106 species of Typhlopidae and ten genes. Our dataset represents the most comprehensive for SA species, containing seven of eight recognized species. Corroborating previous studies, we recovered the main groups of Typhlopoidea, and for typhlopines, we recovered with strong support two clades: (a) the Greater Antilles radiation, and the (b) Lesser Antilles and SA radiation. Within the SA radiation, we recovered four main lineages: (a) a clade formed by A. tasymicris and A. minuisquamus; (b) a clade composed by A. reticulatus as the sister group of all other SA species; (c) a clade composed by A. brongersmianus as the sister group of a clade comprising all Northeast Brazilian Species (NBS); and (d) a clade of the NBS, including A. yonenagae, A. arenensis, A. paucisquamus, and A. amoipira. We supplemented our phylogenetic result with the description of hemipenial morphology for seven SA species and comment their relevance to the systematics of Typhlopinae. Hemipenes of SA Amerotyphlops follow the general pattern in scolecophidians (single organ with undivided sulcus). Only A. reticulatus and A. minuisquamus have organs with calcified spines. According to our results, hemipenial ornamentation have shown highly informative and could represent a potential source of systematic and taxonomic characters in that group. We also present an extensive review of the geographical distribution for all SA species. Our study represents the first integrative analysis of a poorly known evolutionary radiation of one of the most widespread SA fossorial snakes.
ABSTRACT
Typhlopidae is the most diverse family of Scolecophidia, with 269 species. Amerotyphlops was recently erected within subfamily Typhlopinae and comprises fifteen species distributed from Mexico to Argentina and the southern Lesser Antilles. Despite recent advances, affinities among typhlopines remain poorly explored, and the phylogenetic relationships and morphology of the South American (SA) species were never accessed before. Here, we performed a phylogenetic analysis including 106 species of Typhlopidae and ten genes. Our dataset represents the most comprehensive for SA species, containing seven of eight recognized species. Corroborating previous studies, we recovered the main groups of Typhlopoidea, and for typhlopines, we recovered with strong support two clades: (a) the Greater Antilles radiation, and the (b) Lesser Antilles and SA radiation. Within the SA radiation, we recovered four main lineages: (a) a clade formed by A. tasymicris and A. minuisquamus; (b) a clade composed by A. reticulatus as the sister group of all other SA species; (c) a clade composed by A. brongersmianus as the sister group of a clade comprising all Northeast Brazilian Species (NBS); and (d) a clade of the NBS, including A. yonenagae, A. arenensis, A. paucisquamus, and A. amoipira. We supplemented our phylogenetic result with the description of hemipenial morphology for seven SA species and comment their relevance to the systematics of Typhlopinae. Hemipenes of SA Amerotyphlops follow the general pattern in scolecophidians (single organ with undivided sulcus). Only A. reticulatus and A. minuisquamus have organs with calcified spines. According to our results, hemipenial ornamentation have shown highly informative and could represent a potential source of systematic and taxonomic characters in that group. We also present an extensive review of the geographical distribution for all SA species. Our study represents the first integrative analysis of a poorly known evolutionary radiation of one of the most widespread SA fossorial snakes.
