Physiological Specialization by Thermal Adaptation Drives Ecological Divergence in a Sympatric Fish Species Pair

Hypothesis: Divergence in thermal preference, in combination with temperature-related metabolic adaptations, promotes eco-physiological specialization of a sympatric species pair of coregonid fish. Background: The species show substantially lower divergence in diet composition than other sympatric fish pairs in temperate freshwater lakes, but segregate vertically within the pelagic area and differ in physiology with respect to metabolism. Organism: Sympatric European vendace (Coregonus albula) and endemic dwarf-sized Fontane cisco (C. fontanae) from Lake Stechlin, Germany. Methods: We determined the final thermal preferendum (FTP) of both species previously hatched and raised under identical laboratory conditions by using a shuttle-box system that allowed the fish to control body temperature through behavioral thermoregulation. Results: The species showed clearly different temperature selection behaviors. Vendace had a significantly higher FTP (9.0°C) compared to Fontane cisco (4.2°C). The FTPs comply with temperatures of minimum net swimming costs, suggesting that performance is optimized at the respective thermal preferences of both species. Conclusions: The correspondence of thermal preference and thermal physiology correspond to the vertical habitat segregation of the two species and show that they are adapted to different thermal regimes.

OHLBERGER Jan;  STAAKS Georg;  PETZOLDT Thomas;  MEHNER Thomas;  HOELKER Franz; 

2009-01-07

EVOLUTIONARY ECOLOGY LTD

JRC48391

1522-0613,