Geographic restriction, genetic divergence, and morphological disparity in the Brazilian Atlantic Forests: Insights from Leposoma lizards (Gymnophthalmidae, Squamata)

Abstract

Lineage differentiation, long-term persistence, and range limitation promote high levels of phylogenetic and phylogeographic endemisms and likely underlie the abundant morphologically cryptic diversity observed in the Brazilian Atlantic Forests (AF). We explore lineage differentiation and range restriction in the AF and ask if genetic divergence and morphological disparity are correlated by integrating coalescent-based species delimitation, molecular phylogenetic, and morphological analyses in the lizard genus Leposoma. We present the first species tree for Leposoma and of their tribe, the Ecpleopodini. The analyses are based on the largest dataset ever assembled for Leposoma in terms of number of species (all represented), genetic markers (12 loci), and geographic coverage (~2,500km). The exercise allows us to robustly delimit species within the genus and phylogeographic lineages within all species. We find support for the monophyly of the genus and for the recognition of a yet undescribed species around the Baía de Todos-os-Santos, in the state of Bahia; this form is distinct from all other congeners, both genetically and morphologically. We find that L. baturitensis, from the northeastern state of Ceará, is basal to the genus - and sister to a clade of six species restricted to the AF across the eastern coast of Brazil. Relationships within this coastal clade are ((((L. annectans, Leposoma sp.), L. scincoides), L. puk) (L. nanodactylus, L. sinepollex)). Phylogenetic and phylogeographic analyses, together with precise distribution data, allowed us to update the ranges of species and phylogeographic lineages. We reveal pervasive geographic restriction of divergent lineages in Leposoma at and below species level and discuss how forest refuges and rivers might have contributed to it. We find that morphological disparity lags behind genetic divergence in the genus because although they are correlated, the first accumulates at a much slower rate than the latter. We hope to encourage new studies in the area of AF north of the Doce river; phylogeographic sampling in that region has been much less common relative to southern sites, yet it may hold the key to several important processes defining biodiversity patterns in eastern Brazil. This appears to specially apply to processes underlying geographic restriction of morphologically cryptic, yet genetic divergent lineages, as the case of Leposoma.