Latitudinal countergradient variation in the common frog (Rana temporaria) development rates - evidence for local adaptation

Ane Laugen, A Laurila, K Räsänen, J Merilä

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    Abstract

    Adaptive genetic differentiation along a climatic gradient as a response to natural selection is not necessarily expressed at phenotypic level if environmental effects on population mean phenotypes oppose the genotypic effects. This form of cryptic evolution - called countergradient variation - has seldom been explicitly demonstrated for terrestrial vertebrates. We investigated the patterns of phenotypic and genotypic differentiation in developmental rates of common frogs (Rana temporaria) along a ca. 1600 km latitudinal gradient across Scandinavia. Developmental rates in the field were not latitudinally ordered, but displayed large variation even among different ponds within a given latitudinal area. In contrast, development rates assessed in the laboratory increased strongly and linearly with increasing latitude, suggesting a genetic capacity for faster development in the northern than the southern larvae. Experiments further revealed that environmental effects (temperature and food) could easily override the genetic effects on developmental rates, providing a possible mechanistic explanation as to why the genetic differentiation was not seen in the samples collected from the wild. Our results suggest that the higher developmental rates of the northern larvae are likely to. be related to selection stemming from seasonal time constrains, rather than from selection dictated by low ambient temperatures per se. All in all, the results provide a demonstration of environmental effects concealing substantial latitudinally ordered genetic differentiation understandable in terms of adaptation to clinal variation in time constrains.
    Original languageUndefined/Unknown
    Pages (from-to)996–1005
    Number of pages10
    JournalJournal of Evolutionary Biology
    Volume16
    Issue number5
    DOIs
    Publication statusPublished - 2003
    MoE publication typeA1 Journal article-refereed

    Keywords

    • amphibians
    • countergradient variation
    • developmental rate
    • egg size
    • latitudinal gradient
    • local adaptation

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