Molecular phylogeny, biogeography and chromosome evolution of Malagasy dwarf geckos of the genus Lygodactylus (Squamata, Gekkonidae)

Abstract

We performed a phylogenetic analysis using nuclear (RAG‐1, RAG‐2) and mitochondrial (16S) markers, a statistical Bayesian reconstruction of ancestral distribution areas and a karyological analysis on most Malagasy species of the gekkonid genus Lygodactylus. The phylogenetic analysis largely confirms major basal branching pattern of previous molecular studies, but highlights significant differences concerning both the relationships between different species groups as well as those within groups. The biogeographic analysis supports a Malagasy origin of Lygodactylus, an oversea dispersal to continental Africa and a return to Madagascar. The L. madagascariensis group (also including a new candidate species identified herein) is the most basal clade in Lygodactylus, and the sister group of a clade with all the remaining species. The second most basal clade is the L. verticillatus group, placed as the sister group of a clade comprising African and Malagasy species. The sister lineage of the L. verticillatus group originated the African radiation through an oversea dispersal out of Madagascar. Eventually, the sister lineage of the L. capensis group originated secondary dispersals from Africa to Madagascar. In Madagascar, lineage diversification in different species groups mainly occurred from southern to northern and eastern regions. Dispersal, vicariance and paleoclimatic refugia probably played a relevant role in the evolutionary history of closely related taxa and in speciation mechanisms. The cytogenetic analysis evidenced a high karyotypic variability in Lygodactylus (from 2n = 34 to 2n = 40), which is at least partly consistent with the phylogenetic relationships and the composition of the various species group. Chromosome evolution occurred independently in different lineages, mainly through a reduction in the chromosome number and starting from a putative primitive karyotype of 2n = 40 with all telocentric elements.