Nacella concinna, phenotypic plasticity or genetic differentiation: divergent opinions and supporting evidences

M. CARLA DE ARANZAMENDI; RICARDO SAHADE

Los Cocos, Córdoba

Workshop; First IMCOAST Workshop; 2010

Nacella concinna is one of the dominant and most abundant shallow waters invertebrates of the Antarctic, and one of the few inhabiting the intertidal zone. This species presents two morphotypes: littoral (migrant) and sublittoral (non-migrant). The first attempt to establish whether these differences were due to separate gene pools was conducted by allozyme electrophoresis; no genetic differences were found and it was hypothesized that such differences were due to phenotypic plasticity. However, using ISSR-PCR as molecular markers genetic differences between the two morphs in populations of Potter Cove were found as was in Admiralty Bay using AFLP, other dominant marker. But later, in Adelaide Island populations using also AFLP there was found no evidence of differentiation between morphs and again the differences were attributed to the phenomenon of phenotypic plasticity. Therefore the question is still open and although the later study was using a higher samples number, it is also true, that together with morphological differentiation, including more advance techniques as Elliptical Fourier Analysis, it has been observed physiological and behavioral differences, suggesting that some degree of genetic differentiation, not fully revealed yet, can be possible. The question acquires more relevance under the current warming process where shallow water and intertidal systems will be especially affected.