The existence of two Pisaster ochraceus subspecies has been proposed; one located northwards (P. ochraceus ochraceus) and the other southwards (Pisaster ochraceus segnis) from Point Conception. We used polymerase chain reaction–restriction fragment length polymorphism of the CO I and CO III mitochondrial genes to assess the degree of population structure from 126 samples collected along the western coast of North America, from Vancouver, Canada to Punta San Carlos, of Baja California, Mexico. The genetic structure was tested through molecular analysis of variance and by Monte Carlo simulations of the original data set. The phylogeographical pattern was deduced from a minimum spanning network analysis. No genetic structure was detected. Instead, a high degree of genetic homogeneity along the species distribution was evident from haplotype frequencies at each location. Two haplotypes, Po1 and Po5, were predominant along the distribution and were considered ancestral because of their central position in the minimum spanning network. Since Pisaster ochraceus depicts a planktotrophic larval stage with very long duration before settlement, it seems to be able to surpass the biogeographical boundary that limits other species around Point Conception, thereby maintaining homogeneity of its genetic pool. Results of this study recognize P. ochraceus as a single species.
In this study, polychaetous annelids are recorded for the first time in Mexican cenotes and anchialine caves. These organisms were collected in the Cenote Aerolito (Cozumel Island, on the Caribbean coast of Quintana Roo) during three sampling events from February 2006 to April 2008, among algae, roots of mangroves, and in karst sediments. A total of 1518 specimens belonging to five families (Paraonidae, Capitellidae, Nereididae, Dorvilleidae, and Syllidae), ten genera, and eleven species were collected. In the cave system, two specimens of the amphinomid Hermodice carunculata were found. This cenote and its biota are now in danger of disappearing because of a marina construction project in its western shore.
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