The 81st Annual Meeting of the American Association of Physical Anthropologists (2012)


Biogeography of squirrel monkeys (Saimiri)

JESSICA W. LYNCH ALFARO1 and MICHAEL E. ALFARO2.

1Center for Society and Genetics, UCLA, 2Ecology and Evolutionary Biology, UCLA

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Squirrel monkeys are distributed across Amazonia with isolated populations in Central America. Taxonomists disagree over the number of distinct species and species relationships in Saimiri. Chiou et al. (2011) determined that present-day Saimiri diversified in the Pleistocene. Lavergne et al. (2010) estimated the diversification leading to modern Saimiri as significantly earlier, ~ 4.3 Ma; they found support for two main clades of Saimiri, including (1) S. cassiquiarensis, S. albigena, S. macrodon, S. collinsi and S. ustus; and (2) S. sciureus, S. oerstedii and S. boliviensis. Here we analyzed cytochrome b data from 35 new Saimiri museum samples of wild-caught individuals from Brazil, Bolivia, Peru, Guyana, Colombia, Ecuador, and Costa Rica, along with 41 GenBank sequences. A Bayesian analysis recovered three distinct clades: (1) Saimiri boliviensis; (2) Saimiri sciureus and S. oerstedii; and (3) S. macrodon, S. cassiquiarensis, S. albigena, S. ustus, and S. sciureus from far northeastern Brazil. We applied a Bayesian discrete-states diffusion model to reconstruct the most probable history of invasion across nine biogeographic regions in Saimiri distribution. We used comparative methods to test for dispersal rate variation across the three recovered clades of squirrel monkeys. We calibrated the timing of the splits within Saimiri from a fossil-calibrated platyrrhine time tree and compared the timing of invasion of Saimiri into different regions to the invasion of these areas by their sister group, capuchin monkeys. Our study provides a major advance in the biogeographic understanding of the expansion of squirrel monkeys across the Amazon Basin and into Central America.

Funding for this research was provided by NSF BCS 0833375 to J.L.A. and NSF DEB 0918748 to M.E.A.

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