Phylogenetic and divergence time analysis of the Chelonoidis chilensis complex (Testudines: Testudinidae)

JULIETA SÁNCHEZ; JUAN HOLLEY; SEBASTIÁN POLJACK; ALEJANDRO BOLZÁN; CLAUDIO M. BRAVI

ZOOTAXA

MAGNOLIA PRESS

Lugar: Auckland; Año: 2017 vol. 4320 p. 487 - 504

1175-5326

We present a phylogenetic and divergence time analysis of the Chelonoidis chilensis complex (the southernmost tortoisesof South America) within crown Testudinidae. We compiled a dataset of 1118 bp cytochrome b (cyt b) sequences derivedfrom 111 individuals sampled across the known geographic range of the species, and performed a phylogenetic analysisemploying Maximum Parsimony, Maximum Likelihood and Bayesian Inference methods. The resulting trees showed similartopologies and support values. The C. chilensis complex was always recovered as a monophyletic group composedby two major clades (i.e. haplogroups). The biogeographic distribution of one of these clades overlaps with the Dry Chacoeco?region, while the biogeographic distribution of the other overlaps with the Monte eco?region. In order to date the originand diversification time of these two clades, we employed a previously published two-step molecular clock method.In the first step we dated the time of origin of C. chilensis as a clade within the Testudinidae family using new and previouslypublished sequences, extinct testudinid taxa for age calibration and the Fossilized Birth-Death (FBD) model. In thesecond step we dated the divergence between the haplogroups of C. chilensis based on the time of origin estimated in thefirst step and a coalescent evolution model. Our results suggest that divergence between Dry Chaco and Monte tortoisesmay have occurred about 2.47 million of years ago. We interpret these results in the light of the environmental and geologicalchanges that occurred during the late Pliocene to Middle Pleistocene of South America.