Evol Ecol Res 10: 1173-1185 (2008)     Full PDF if your library subscribes.

Physiological specialization by thermal adaptation drives ecological divergence in a sympatric fish species pair

Jan Ohlberger1, Georg Staaks1, Thomas Petzoldt2, Thomas Mehner1 and Franz Hölker1,3

1Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Berlin, Germany, 2Technische Universität Dresden, Institute of Hydrobiology, Dresden, Germany and 3Europoean Commission, DG Joint Research Centre, Institute for the Protection and Security of the Citizen, Maritime Affairs, Ispra, Italy

Correspondence: J. Ohlberger, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Department of Biology and Ecology of Fishes, PO Box 850 119, D-12561 Berlin, Germany.
e-mail: ohlberger@igb-berlin.de


Hypothesis: Divergence in thermal preference, in combination with temperature-related metabolic adaptations, promotes ecological specialization and co-existence of a sympatric species pair of coregonid fish.

Background: The coregonids 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 behavioural thermoselection.

Results: The species showed clearly different temperature selection behaviours. Vendace had a significantly higher FTP (9.0°C) than Fontane cisco (4.2°C). The FTPs comply with temperatures of minimum net swimming costs, suggesting that performance is optimized at the respective thermal preference of both species.

Conclusions: The correspondence of thermal preference, thermal performance functions, and thermal ecology shows that the species are adapted to different temperature regimes.

Keywords: Coregonus spp., divergence, sympatric species, temperature preference.

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