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Abstract(s)
The genus Tripterygion (Risso 1826) is
restricted to the eastern Atlantic and the Mediterranean,
and comprises only three species. T. melanuros
and T. tripteronotus are essentially endemic to the
Mediterranean, while Tripterygion delaisi occurs in the
Atlantic and in the Mediterranean. Two subspecies of
T. delaisi have been described (T. d. xanthosoma in the
Mediterranean and T. d. delaisi in the Atlantic). Several
scenarios have been proposed for the evolution of
T. delaisi subspecies, but so far its subspeciation process
is not clear. In this study we present a population
survey of T. delaisi including specimens from the two recognized subspecies. We combined a phylogeographic
approach with estimates of the direction of
migration (between the Atlantic and the Mediterranean)
and of the coalescence time of the two subspecies,
using polymorphic mitochondrial and nuclear
genes. The results of this study clearly support the existence
of two Tripterygion delaisi clades, one in the eastern
Atlantic islands and another in the Atlantic coasts
of Europe and in the Mediterranean. Historical migration
between the islands and Western Europe plus
Mediterranean was restricted, and showed a westbound
trend, with a higher number of migrants going
from the Western Europe plus Mediterranean into the
islands. We estimated the time of coalescence of both
groups of T. delaisi to be more recent than the onset of
Pleistocene glaciations (1.7 Mya). Our results are consistent
with previous hypothesis that consider successive
dispersal events of a Tripterygion ancestor from
the western African coast colonizing the Atlantic
islands and the Mediterranean, promoting the evolutionary
divergence between these areas.
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Citation
Marine Biology, 150,509-519