Comparative populational study of Lepidonotothen larseni and L. nudifrons (Teleostei: Nototheniidae) from the Antarctic Peninsula and the South Shetland Islands, Antarctica

摘要

Most Antarctic notothenioids exhibit clear geographic structure at large scales of spatial separation, generally between populations off different Ocean sectors. At smaller distances, there is great variation in the extent of population structuring. The Antarctic Peninsula and the archipelago of the South Shetland Islands are separated by a narrow strait of deep water (1000 m). Despite the proximity of these two areas, the confluence of water masses of different origins establishes frontal systems and local gyres which may preclude migration between shelf populations. Among the most abundant fish species in the area, the painted notothen Lepidonotothen larseni and the gaudy notothen Lepidonotothen nudifrons are two of the most numerous and widely distributed. In the present study, the genetic and morphological population structure of these closely related species was evaluated between the Antarctic Peninsula and the South Shetland Islands. Nine meristic counts, 18 inter-landmark distances and a mitochondrial DNA marker (D-loop) were analyzed. Populations of L. nudifrons were significantly different based on both, morphogeometric and genetic analyses, while L. larseni showed no population differentiation. The results showed a moderate structuring not correlated with distance between L. nudifrons populations off the Antarctic Peninsula and the South Shetland Islands. These findings provide evidence that differences between the studied species may be linked to key life history events, such as timing and location of egg development, hatching times and dispersal period of larvae. The present data suggest that notothenioid population structuring at regional scale may be related to a combination of life history traits, oceanographic features and local adaptation.