Data from: Evolutionary stasis despite selection on a heritable trait in an invasive zooplankton

Invasive species are one of the greatest threats to ecosystems and there
is evidence that evolution plays an important role in the success or
failure of invasions. Yet, few studies have measured natural selection and
evolutionary responses to selection in invasive species, particularly
invasive animals. We quantified the strength of natural selection on the
defensive morphology (distal spine) of an invasive zooplankton,
Bythotrephes longimanus, in Lake Michigan across multiple months during
three growing seasons. We used multiple lines of evidence, including
historic and contemporary wild-captured individuals and paleoecology of
retrieved spines, to assess phenotypic change in distal spine length since
invasion. We found evidence of temporally variable selection, with
selection for decreased distal spine length early in the growing season
and selection for increased distal spine length later in the season. This
trend in natural selection is consistent with seasonal changes in the
relative strength of non-gape-limited and gape-limited fish predation.
Yet, despite net selection for increased distal spine length and a known
genetic basis for distal spine length, we observed little evidence of an
evolutionary response to selection. Multiple factors likely limit an
evolutionary response to selection, including genetic correlations,
trade-offs between components of fitness, and phenotypic plasticity.