Salinity effects on competition between cryptic species of the nematode Rhabditis (Pellioditis) marina

Behind the morphological similarity of many species, a substantial hidden genetic diversity can be found. This cryptic diversity has been well documented in the marine nematode, Rhabditis (Pellioditis) marina, where several cryptic species occur sympatrically. Despite the growing knowledge about its cryptic diversity, little is known about potential differences in the ecology and functional roles of the different species. In this experiment four cryptic species of Rhabditis (Pellioditis) marina were reared together, starting from identical initial abundances at two different salinity concentrations to investigate differences in their environmental preferences and how they may affect the outcome of their competitive interactions. Every fifth day of the experiment one third of the adults was removed from the population for analyzing the genetic composition of the population; adult and juvenile population dynamics were also examined. The first results show a difference in population dynamics dependent on the salinity. At low salinity, a population crash occurred after 15 days in all the populations. Only half of the populations recovered from this bottleneck and reached higher abundances than before. Genetic analyses revealed that the composition of these populations consists solely of individuals of one cryptic species. This effect was totally absent in the populations reared at higher salinity. Two explanations are possible: (1) the different cryptic species have different survival rates at different salinities and (2) the competitive interactions between them differ at different salinities. We are currently identifying the sampled adults using a restriction fragment analysis to assess these explanations and to elucidate the effect of salinity on the coexistence of cryptic species of Rhabditis (Pellioditis) marina.

Jaar van publicatie:2010

Toegankelijkheid:Closed