Genetic Relationships (RAPD-PCR) between Geographically Separated Populations of the "Cosmopolitan" Interstitial Polychaete Hesionides gohari (Hesionidae) and the Evolutionary Origin of the Freshwater Species Hesionides riegerorum

In an analysis of the population genetics of the tiny meiofaunal polychaete Hesionides gohari, the RAPD-PCR method was applied to 49 specimens from 7 collecting sites far apart on three continents: French Atlantic coast, Mediterranean (Majorca, Giglio, Crete), Red Sea, Indian Ocean (Phuket), and U.S. Atlantic coast (Florida). In the band patterns produced with 14 arbitrary decamer primers, 496 genetic characters were detected. Genetic distances between the H. gohari populations vary between 0.55 and 0.70. The data were evaluated by three cluster programs; in the almost congruent phenograms, three clades were found with high bootstrap values: (1) European Atlantic-Mediterranean-Red Sea, (2) Indian Ocean, (3) Western Atlantic. In all cluster analyses, Hesionides riegerorum from a U.S. east coast river system is shown as genetically nearest to the Florida specimens of H. gohari, making it most probable that this freshwater species of the genus originated from a Western Atlantic H. gohari population. The genetic distances detected between the H. gohari specimens from the three continents are almost identical to those found between morphologically similar interstitial polychaete species pairs. Thus, the degree of genetic consistency is considered not to be high enough to corroborate the notion of a cosmopolitan distribution pattern, but rather suggests that the three clades represent different species.