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Advisor(s)
Abstract(s)
The desiccation of the Mediterranean Sea during the Messinian Salinity Crisis 6.0–5.3 million
years ago (Ma), caused a major extinction of the marine ichthyofauna of the Mediterranean.
This was followed by an abrupt replenishment of the Mediterranean from the Atlantic after
the opening of the Strait of Gibraltar. In this study, we combined demographic and phylogeographic
approaches using mitochondrial and nuclear DNA markers to test the alternative
hypotheses of where (Atlantic or Mediterranean) and when (before or after the Messinian
Salinity Crisis) speciation occurred in the Mediterranean damselfish,
Chromis chromis. The
closely related geminate transisthmian pair
Chromis multilineata and Chromis atrilobata was used as a way of obtaining an internally calibrated molecular clock. We estimated C.
chromis speciation timing both by determining the time of divergence between
C. chromis and its Atlantic sister species
Chromis limbata(0.93–3.26 Ma depending on the molecular marker used, e.g. 1.23–1.39 Ma for the control region), and by determining the time of coalescence for C. chromis
based on mitochondrial control region sequences (0.14–0.21 Ma). The time
of speciation of C. chromis
was always posterior to the replenishment of the Mediterranean basin, after the Messinian Salinity Crisis. Within the Mediterranean,
C. chromis population
structure and demographic characteristics revealed a genetic break at the Peloponnese, Greece, with directional and eastbound gene flow between western and eastern groups. The eastern group was found to be more recent and with a faster growing population (coalescent time = 0.09–0.13 Ma, growth = 485.3) than the western group (coalescent time = 0.13–0.20 Ma, growth = 325.6). Our data thus suggested a western origin of
C. chromis, most likely within
the Mediterranean. Low sea water levels during the glacial periods, the hydrographic
regime of the Mediterranean and dispersal restriction during the short pelagic larval phase of C. chromis(18–19 days) have probably played an important role in
C. chromis historical colonization.
Description
Keywords
Chromis Coalescence Mediterranean Messinian Salinity crisis Phylogeography Speciation
Citation
Molecular Ecology, 14, 4051-4063