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 relati...

入侵物种是生态系统面临的最严重威胁之一，有证据表明进化在入侵的成败中扮演着关键角色。然而，针对入侵物种（尤其是入侵动物）的自然选择强度及对选择的进化响应的研究却较为匮乏。我们量化了密歇根湖（Lake Michigan）中一种入侵性浮游动物——长肢北镖水蚤（Bythotrephes longimanus）的防御形态（远端棘刺，distal spine）在三个生长季多个月份中的自然选择强度。我们采用多维度证据，包括历史与当代野外捕获个体、回收棘刺的古生态学分析，来评估入侵以来远端棘刺长度的表型变化。我们发现了时间依赖性可变选择的证据：生长季初期选择倾向于缩短远端棘刺长度，而季末则倾向于增加其长度。这一自然选择趋势与季节变化中的相对...