Phylogenetic analysis and divergence times of the Chelonoidis chilensis complex (Testudinidae).

SANCHEZ JULIETA; HOLLEY JUAN ALFREDO; POLJAK SEBASTIÁN; BOLZÁN ALEJANDRO; BRAVI CLAUDIO

ZOOTAXA

MAGNOLIA PRESS

Lugar: Auckland; Año: 2017 vol. 4320

1175-5326

We present a phylogenetic and divergence times analysis of the Chelonoidis chilensis complex, the southernmost tortoises of South America. We compiled a dataset of 1118 bp cytochrome b (cytb) sequences derived from 111 individuals sampled across all the known geographic range, and performed a phylogenetic analysis employing Maximum Parsimony, Maximum Likelihood and Bayesian Inference methods. The resulting trees showed similar topologies and support values. The Chelonoidis chilensis complex was always recovered as a monophyletic group, and in turn composed by two major clades (i.e. haplogroups) that mirrors the biogeographic distribution: one clade is composed by individuals derived from the Dry Chaco eco-region while the other assembles those from the Monte eco-region. In order to date the origin and diversification times of these two clades, we employed a previously published two-steps molecular clock method. In the first step we dated the time of origin of Chelonoidis chilensis as a clade within the Testudinidae family using available sequences, the fossil record and the Fossilized Birth-Death (FBD) model. In the second step we dated the divergence between the haplogroups of C. chilensis based in the time of origin estimated in the first step and a coalescent evolution model. Our results suggest that divergence between Dry Chaco and Monte tortoises may have occurred about 2.47 millons of years ago. We interpret these results in the light of the environmental and geological changes occurred during the late Pliocene to Middle Pleistocene of South America.