Evaluating the Diversity of Philippine Slender Skinks of the Brachymeles bonitae Complex (Reptilia: Squamata: Scincidae): Redescription of B. tridactylus and Descriptions of Two New Species
We review the species of the Brachymeles bonitae Complex (B. bonitae and B. tridactylus) and describe an additional two new species in this highly specialized, limb-reduced, endemic Philippine clade of fossorial lizards. For more than 4 decades, B. bonitae has been recognized as a single “widespread” species, a perception that has persisted as a result of limited sampling and similar overall morphology (body sizes, scale pigmentation) among populations. However, on the basis of new collections we note consistent morphological differences between populations, and our new data build on previous observations, allowing us to utilize newly defined character state differences for the purpose of delimiting unambiguous boundaries between species. Here, we use morphological and molecular data to define species limits in B. bonitae and its close relatives. Our data indicate that the “widespread” species B. bonitae is actually a complex of four distinct evolutionary lineages, several of which are not each others' closest relatives. The taxa we define possess allopatric geographic ranges (biogeographically supporting our taxonomic conclusions) and differ from their congeners by several diagnostic characters of external morphology. We conclude that each, therefore, should be recognized as full species in accordance with lineage-based species concepts. Species diversity in the genus has doubled in the last 4 yr, with newly described taxa increasing the total number of species of Brachymeles to 38.Abstract
Map of the Philippine islands with island labels provided for islands with representative samples used for this study. The five recognized major PAICs, major island groups, and additional deep-water islands are labeled for reference. Current islands in the Philippines are shown in medium grey to black; light gray areas enclosed in black, 120-m bathymetric contours indicate the hypothesized maximum extent of land during the mid- to late Pleistocene.
(Left) Map of the Philippine islands showing revised distribution of Brachymeles bonitae and hypothesized distributions of B. isangdaliri, B. mapalanggaon, and B. tridactylus in the central and northern Philippines. Sampling localities are indicated by numerical labels, and the hypothesized geographic range of each species is indicated by shaded elevational ranges corresponding to the map's key. (Right) Hypothesized relationships of Brachymeles used for this study, illustrated by the maximum clade credibility tree resulting from Bayesian analyses. Nodes supported by ≥95% Bayesian posterior probabilities (PP) were considered significantly supported. Terminals are labeled with taxonomic names and sampling localities (Appendix 1) as well as fore- and hindlimb digit states and number of presacral vertebrae. Numerical labels correspond to sampling localities represented on the map.
Illustration of head of Brachymeles tridactylus (KU 307726) and Brachymeles bonitae (KU 326082) in dorsal, lateral, and ventral views. Taxonomically diagnostic head scales are labeled as follows: C, chin shield; F, frontal; FN, frontonasal; FP, frontoparietal; IL, infralabial; IP, interparietal; L, loreal; M, mental; N, nasal; Nu, nuchal; P, parietal; PF, prefrontal; PM, postmental; PN, postnasal; PO, preocular; PSO, presubocular; R, rostral; SC, supraciliary; SL, supralabial; SN, supranasal; and SO, supraocular. Roman numerals indicate scales in the supraocular series, with Arabic numbers indicating scales in the supraciliary series. Illustrations by K. D. Feller and C. D. Siler.
Illustration of head of adult female Brachymeles isangdaliri (PNM 9791; KU 323086; holotype) and adult female Brachymeles mapalanggaon (PNM 9792; formerly KU 323937; holotype) in dorsal, lateral, and ventral views. Taxonomically diagnostic head scales are labeled as follows: C, chin shield; F, frontal; FN, frontonasal; FP, frontoparietal; IL, infralabial; IP, interparietal; L, loreal; M, mental; N, nasal; Nu, nuchal; P, parietal; PF, prefrontal; PM, postmental; PN, postnasal; PO, preocular; PSO, presubocular; R, rostral; SC, supraciliary; SL, supralabial; SN, supranasal; and SO, supraocular. Roman numerals indicate scales in the supraocular series, with Arabic numbers indicating scales in the supraciliary series. Illustrations by K. D. Feller and C. D. Siler.
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