This study examined genetic variation across the range of Brachidontes variabilis to produce a molecular phylogeography. Neighbour joining(NJ), minimum evolution (ME) and maximum parsimony (MP) trees based on partial mitochondrial DNA sequences of 16S-rDNA andcytochrome oxidase (COI) genes revealed three monophyletic clades: (1) Brachidontes pharaonis s.l. from the Mediterranean Sea and the Red Sea;(2) B. variabilis from the Indian Ocean; (3) B. variabilis from the western Pacific Ocean. Although the three clades have never been differentiatedby malacologists employing conventional morphological keys, they should be ascribed to the taxonomic rank of species. The nucleotidedivergences between Brachidontes lineages (between 10.3% and 23.2%) were substantially higher than the divergence between congeneric Mytilusspecies (2.3–6.7%) and corresponded to interspecific divergences found in other bivalvia, indicating that they should be considered three differentspecies. Analysis of the 16S-rDNA sequences revealed heteroplasmy, indicating dual uniparental inheritance (DUI) of mtDNA in the species ofBrachidontes collected in the Indian Ocean, but not in the species in the Pacific nor in the species in the Red Sea and the Mediterranean Sea. Whenwe employed the conventional estimate of the rate of mitochondrial sequence divergence (2% per million years), the divergence times for the threemonophyletic lineages were 6–11 Myr for the Indian Ocean and Pacific Ocean Brachidontes sp. and 6.5–9 Myr for the Red Sea and Indian OceanBrachidontes sp. Thus, these species diverged from one another during the Miocene (23.8–5.3 Myr). We infer that a common ancestor of the threeBrachidontes species probably had an Indo-Pacific distribution and that vicariance events, linked to Pleistocene glaciations first and then to theopening of the Red Sea, produced three monophyletic lineages.
|Numero di pagine||10|
|Rivista||Journal of Zoological Systematics and Evolutionary Research|
|Stato di pubblicazione||Published - 2007|
All Science Journal Classification (ASJC) codes
- Ecology, Evolution, Behavior and Systematics
- Animal Science and Zoology
- Molecular Biology