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A multilocus test of simultaneous divergence across the Isthmus of Panama using snapping shrimp in the genus Alpheus.

Authors
  • Hurt, Carla1
  • Anker, Arthur
  • Knowlton, Nancy
  • 1 Department of Biology, University of Miami, Coral Gables, Florida 33124, USA. [email protected]
Type
Published Article
Journal
Evolution
Publisher
Wiley (Blackwell Publishing)
Publication Date
Feb 01, 2009
Volume
63
Issue
2
Pages
514–530
Identifiers
DOI: 10.1111/j.1558-5646.2008.00566.x
PMID: 19154357
Source
Medline
License
Unknown

Abstract

The completion of the Panamanian Isthmus is one of the greatest natural experiments in evolution, sending multiple species pairs from a broad range of taxonomic groups on independent evolutionary trajectories. The resulting transisthmian sister species have been used as model systems for examining consequences that accompany cessation of gene flow in formerly panmictic populations. However, variance in pairwise genetic distances of these "geminates" often exceeds expectations, seemingly conflicting with the assumption that separation of populations was contemporaneous with the final closure of the Isthmus. Multilocus datasets and coalescent-based analytical methods can be used to estimate divergence times while accounting for variance in gene divergence that predates isolation, thus removing the need to invoke unequal divergence times. Here we present results from Bayesian analyses of sequence data from seven nuclear and one mitochondrial marker in eight transisthmian species pairs in the snapping shrimp genus Alpheus. Divergence times in two species pairs were shown to occur much earlier than the Isthmus final closure, but much of the variance in pairwise genetic distances from cytochrome oxidase I (COI) was explained when ancestral polymorphisms were accounted for. Results illustrate how coalescent approaches may be more appropriate for dating recent divergences than for estimating ancient speciation events.

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