The lineages of Gymnodactylus associated to the Atlantic Forest are excellent models to investigate the mechanisms which create and maintain the biological diversity in this biome. Distributed from Rio Grande do Norte to São Paulo, they present a strong north-south genetic structure. The coincidence between clades and river drainage suggests that rivers promote separation of the lineages. On the other hand, the related lineages from Cadeia do Espinhaço suggest a vicariate process associated with the distribution of those mountains. Secondary contact zones and hybridization events between related linages or sister species are natural laboratories to study the process of formation and maintenance of species. In Gymnodactylus there is evidence of hybridization between two distinct lineages that occur south and north of the Doce River. Unknown processes could explain the emergence of lineages related to "darwinii" group that occur west of the Espinhaço range. Known from a few localities, these forms are related to lineages of the Atlantic forest, and not to those of the Espinhaço Range, or even to the species of the group "amarali" (Cerrado and Caatinga), sister of "darwinii" group.We propose here the detailed investigation of the darwinii group of Gymnodactylus in order to understand the process of species formation in one of the most diverse areas of the planet. The Gymnodactylus clades of the darwinii group shows: (1) A clinal structure due to its wide north-south distribution in the Atlantic Forest, where rivers act as potential barriers and could be involved in the formation of different clades within the formally recognized G . darwinii species. (2) A strong phylogeographic structure with morphological, genetical and geographically divergent lineages occurring allopatrically in the Espinhaço range [in Bahia (G. vanzolinii) and two in Minas Gerais (G. guttulatus in Diamantina, and a clade in the Serra de Grão Mogol)] (3) isolated populations recorded from a few places west of the Espinhaço, that are morphologically related to Atlantic Forest lineages. Thus, the objective is to locate in fine geographical scale the contact zones among phylogeographic lineages and / or sister species within the darwinii group throughout its distribution in the Atlantic Forest; identify the level of hybrid formation in contact zones, such as the region of the delta of the Rio Doce; and identifying and detailing cline of genetic and environmental variation in the contact areas.Genetic analyses will be performed with the use of nuclear markers (at least 6), ribosomal (1) and mitochondrial (2), five of them previously used by Cassimiro (2010) in analyses of the phylogeny of Gymnodactylus and in a phylogeographic study of the Gymnodactylus amarali species in Domingos et al. (2014). The methodology of extraction, amplification and sequencing of the samples is described in several works and can be seen in detail in (Cassimiro 2010). The analysis will follow that of Domingos et al. (2014). The proportion of hybrid individuals will be calculated by methods based on individual genotypes of multiple markers, using tests and algorithms implemented by the software STRUCTURE (Pritchard et al. 2000) and NewHybrids (Anderson and Thompson 2002).This proposal, an extension of the thematic project to which it is linked, will focusing on mechanisms and evolutionary processes in order to integrate the various themes studied in my laboratory: natural history, phylogeny, phylogeography, biogeography, eco-physiology, morphology and systematics.
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