Signatures of seaway closures and founder dispersal in the phylogeny of a circumglobally distributed seahorse lineage |
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Authors: | Peter R Teske Healy Hamilton Conrad A Matthee Nigel P Barker |
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Institution: | (1) Molecular Ecology and Systematics Group, Botany Department, Rhodes University, 6140, Grahamstown, South Africa;(2) Evolutionary Genomics Group, Department of Botany and Zoology, Stellenbosch University, Private Bag X1, 7602, Matieland, South Africa;(3) Research Division, California Academy of Sciences, 875 Howard St., 94103 San Francisco, CA, USA |
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Abstract: | Background The importance of vicariance events on the establishment of phylogeographic patterns in the marine environment is well documented,
and generally accepted as an important cause of cladogenesis. Founder dispersal (i.e. long-distance dispersal followed by
founder effect speciation) is also frequently invoked as a cause of genetic divergence among lineages, but its role has long
been challenged by vicariance biogeographers. Founder dispersal is likely to be common in species that colonize remote habitats
by means of rafting (e.g. seahorses), as long-distance dispersal events are likely to be rare and subsequent additional recruitment
from the source habitat is unlikely. In the present study, the relative importance of vicariance and founder dispersal as
causes of cladogenesis in a circumglobally distributed seahorse lineage was investigated using molecular dating. A phylogeny
was reconstructed using sequence data from mitochondrial and nuclear markers, and the well-documented closure of the Central
American seaway was used as a primary calibration point to test whether other bifurcations in the phylogeny could also have
been the result of vicariance events. The feasibility of three other vicariance events was explored: a) the closure of the
Indonesian Seaway, resulting in sister lineages associated with the Indian Ocean and West Pacific, respectively; b) the closure
of the Tethyan Seaway, resulting in sister lineages associated with the Indo-Pacific and Atlantic Ocean, respectively, and
c) continental break-up during the Mesozoic followed by spreading of the Atlantic Ocean, resulting in pairs of lineages with
amphi-Atlantic distribution patterns. |
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