Filogeografia em áreas abertas da América do Sul: origem e diversificação de linhagens de Scinax squalirostris (Anura, Hylidae)
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2012-04-27
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Universidade Federal de Goiás
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(Phylogeography of Scinax squalirostris). In this work we used 175 individuals of
Scinax squalirostris from 26 localities in the Brazilian states of Minas Gerais, São
Paulo, Goiás, Mato Grosso do Sul, Santa Catarina, Rio Grande do Sul, Parana, and
Distrito Federal, as well as individuals from Paraguay, Uruguay and Argentina. Three
mitochondrial (cytb, 12S and CO1) and one nuclear (RAG-1) gene fragments were
sequenced. The determination of the phylogenetic structured populations and the
relationships among them were made under phylogenetic analyses based on Bayesian
statistical methods. The most parsimonious relationship among haplotypes was made
under the method of median-joining network. The delineation of the hypothetical
operational taxonomic units was made under DNA mini-barcoding procedures,
combined with genetic and phylogenetic evidence. In addition, we performed
population structure tests of, gene flow and changes in population sizes. Finally, times
of divergence among genealogical lineages were estimated by relaxed molecular clock
procedures. Considering the phylogenetic species concept, there are two possible
scenarios for the taxonomic lineages of the cryptic complex named Scinax squalirostris.
In the first scenario, there are two possible species: one with tropical and other with
subtropical/temperate distributions, respectively. The second scenario points to the
existence of at least nine species: one in the Pampas, one in the Chaco and the
remaining seven isolated in 'sky-islands' from the Cerrado and Atlantic Forest domains.
The first cladogenetic event of the lineages dates from the Upper Miocene,
approximately 7.5 million years ago. This may have occurred by the last contraction of
Paranaense Sea. During this period, new suitable areas for S. squalirostris emerged,
leading to the clades belonging to tropical and subtropical/temperate zones
diversification, and it would be consistent with the first taxonomic scenario. The
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diversification within these two major clades occurred in the transition between the late
Tertiary and early Quaternary. The current distribution of S. squalirostris in the tropical
zone probably should be linked to climatic and geological changes that occurred in the
transition between the Pliocene and Pleistocene. During the Quaternary glaciations, the
grasslands have undergone expansion (periods during glaciations) and retraction (during
interglacials). When the temperature and moisture increased in the Late Holocene,
occurred retraction of the grasslands in favor to the expansion of forests and tree/shrub
savannas. Thus, the suitable habitats to S. squalirostris were restricted to the grasslands
at altitudes greater than 800m in the tropics. The cycles of grasslands isolation on
islands must have influenced the recent diversification of the local clades of S.
squalirostris.
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MAGALHÃES, R. F. Filogeografia em áreas abertas da América do Sul: origem e diversificação de linhagens de Scinax squalirostris (Anura, Hylidae). 2012. 98 f. Dissertação (Mestrado em Ecologia e Evolução) - Universidade Federal de Goiás, Goiânia, 2012.