Anssi Karvonen, Bjarni K. Kristjánsson, Skúli Skúlason, Maiju Lanki, Christian Rellstab and Jukka Jokela Water temperature, not fish morph, determines parasite infections of sympatric Icelandic threespine sticklebacks (Gasterosteus aculeatus) Ecology and Evolution 3
Ecological differences in selection by parasites have recently been hypothesized to facilitate evolutionary differentiation of freshwater fish morphs. However, as parasites may also respond directly to abiotic environment, such as water temperature, it is not clear how consistent these selection gradients are when abiotic factors change. We examined parasite pressure in sympatric morphs of threespine stickleback in two Icelandic lakes with opposing habitat-specific water temperature gradients. We found higher infestation in fish living in higher temperature irrespective of the fish morph, but also a strong effect of host ecology in a morph living in deep cold water habitat. These results suggest complex interactions between water temperature and biotic factors in determining the parasite community structure, a pattern that may have implications for differentiation of stickleback morphs.
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