Fitness costs associated with low genetic variation are reduced in a harsher environment in amphibian island populations |
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Authors: | Björn Rogell Hanna Thörngren Anssi Laurila Jacob Höglund |
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Institution: | 1.Population Biology and Conservation Biology/Department of Ecology and Evolution, Evolutionary Biology Centre,Uppsala University,Uppsala,Sweden;2.Animal Ecology/Department of Ecology and Evolution, Evolutionary Biology Centre,Uppsala University,Uppsala,Sweden |
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Abstract: | A basic premise of conservation geneticists is that low levels of genetic variation are associated with fitness costs in terms
of reduced survival and fecundity. These fitness costs may frequently vary with environmental factors and should increase
under more stressful conditions. However, there is no consensus on how fitness costs associated with low genetic variation
change under natural conditions in relation to the stressfulness of the environment. On the Swedish west coast, natterjack
toad Bufo calamita populations show a strong population genetic structure and large variation in the amount of within-population genetic variation.
We experimentally examined the survival of natterjack larvae from six populations with different genetic variation in three
thermal environments corresponding to (a) the mean temperature of natural ponds (stable, laboratory), (b) a high temperature
environment occurring in desiccating ponds (stable, laboratory) and (c) an outdoor treatment mimicking the natural, variable
thermal conditions (fluctuating, semi-natural). We found that larvae in the outdoor treatment had poorer survival than larvae
in the stable environments suggesting that the outdoor treatment was more stressful. Overall, populations with higher genetic
variation had higher larval survival. However, a significant interaction between treatments and genetic variation indicated
that fitness costs associated with low genetic variation were less severe in the outdoor treatment. Thus, we found no support
for the hypothesis that fitness costs associated with low genetic variation increase under more stressful conditions. Our
results suggest that natural thermal stress may mask fitness losses associated with low genetic variation in these populations. |
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