Original Article

Heredity (2016) 116, 550–557; doi:10.1038/hdy.2016.17; published online 13 April 2016

Model-based analysis supports interglacial refugia over long-dispersal events in the diversification of two South American cactus species

M F Perez1,3, I A S Bonatelli1,3, E M Moraes1 and B C Carstens2

  1. 1Departamento de Biologia, Universidade Federal de São Carlos, Sorocaba, São Paulo, Brazil
  2. 2Department of Evolution, Ecology and Organismal Biology, The Ohio State University, Columbus, OH, USA

Correspondence: MF Perez or IAS Bonatelli, Department of Biology, Federal University of Sao Carlos, Rod Joao Leme dos Santos km 110, Sorocaba, 18052780 São Paulo, Brazil. E-mail: manolofperez@gmail.com or belbonatelli@gmail.com

3These authors contributed equally to this work.

Received 16 August 2015; Revised 26 January 2016; Accepted 2 February 2016
Advance online publication 13 April 2016

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Abstract

Pilosocereus machrisii and P. aurisetus are cactus species within the P. aurisetus complex, a group of eight cacti that are restricted to rocky habitats within the Neotropical savannas of eastern South America. Previous studies have suggested that diversification within this complex was driven by distributional fragmentation, isolation leading to allopatric differentiation, and secondary contact among divergent lineages. These events have been associated with Quaternary climatic cycles, leading to the hypothesis that the xerophytic vegetation patches which presently harbor these populations operate as refugia during the current interglacial. However, owing to limitations of the standard phylogeographic approaches used in these studies, this hypothesis was not explicitly tested. Here we use Approximate Bayesian Computation to refine the previous inferences and test the role of different events in the diversification of two species within P. aurisetus group. We used molecular data from chloroplast DNA and simple sequence repeats loci of P. machrisii and P. aurisetus, the two species with broadest distribution in the complex, in order to test if the diversification in each species was driven mostly by vicariance or by long-dispersal events. We found that both species were affected primarily by vicariance, with a refuge model as the most likely scenario for P. aurisetus and a soft vicariance scenario most probable for P. machrisii. These results emphasize the importance of distributional fragmentation in these species, and add support to the hypothesis of long-term isolation in interglacial refugia previously proposed for the P. aurisetus species complex diversification.