Testing for biogeographic mechanisms promoting divergence in Caribbean crickets (genus Amphiacusta)

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Abstract:

Abstract Aim 

This work examines whether the history of diversification of Amphiacusta (Orthoptera, Gryllidae) in the Caribbean corresponds to a vicariant or a dispersalist model. Location 

The Greater Antillean islands of the Caribbean region. Methods 

The phylogenetic relationships among species were estimated using a procedure that directly estimates the underlying species tree from independent loci (in this case, one mitochondrial and one nuclear locus). This tree was then used to test for topological congruence with a vicariant model, and to estimate divergence times. Results 

The analyses based on the expected pattern of species divergence (i.e. species-tree topology) support a vicariant model. With the notable exception of a dispersal event marking the colonization of Jamaica, the timing of the events are generally consistent with a vicariant scenario, given the current taxon sampling and potential errors with dating the divergence events. Main conclusions 

The tendency of species to co-segregate by island suggests that intra-island diversification is common. Despite their flightlessness, species of Amphiacusta are apparently capable of long-distance dispersal, such as colonization from the Puerto Rican/Virgin Island bank to Jamaica. The topology of the species tree is consistent with a vicariant model of divergence, and the dates of divergence between island groups are generally consistent with an island–island vicariance model. A strict island–island vicariance scenario can, however, be rejected because of inferred dispersal events such as the colonization of Jamaica. Nevertheless, the biogeographic tests suggest that most of the diversity was generated under a combination of intra-island diversification and island–island vicariance. Additional sampling of taxa will be needed to verify this hypothesized scenario. Our findings indicate that Amphiacusta presents an ideal opportunity for examining the role of sexual selection in promoting diversification, which would complement the large number of studies focused on adaptive divergence of Caribbean taxa.

Keywords: Amphiacusta; Caribbean; Greater Antilles; dispersal; diversification; historical biogeography; island–island vicariance; sexual selection

Document Type: Research Article

DOI: http://dx.doi.org/10.1111/j.1365-2699.2009.02231.x

Affiliations: 1: Department of Biology, Duke University, 125 Science Drive, Durham, NC 27708, USA 2: Academy of Natural Sciences, 1900 Benjamin Franklin Parkway, Philadelphia, PA 19103, USA

Publication date: March 1, 2010

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