Data from: Combining niche-shift and population genetic analyses predicts rapid phenotypic evolution during invasion

Rapid evolution of non-native species can facilitate invasion success, but recent reviews indicate that such microevolution rarely yields expansion of the climatic niche in the introduced habitats. However, because some invasions originate from a geographically restricted portion of the native species range and its climatic niche, it is possible that the frequency, direction and magnitude of phenotypic evolution during invasion has been underestimated. We explored the utility of niche-shift analyses in the red seaweed Gracilaria vermiculophylla, which expanded from the northeastern coastline of Japan to North America, Europe and northwestern Africa within the last 100 years. A genetically-informed climatic niche shift analysis indicates that native source populations occur in colder and highly seasonal habitats, while most non-native populations typically occur in warmer, less seasonal habitats. This climatic niche expansion predicts that non-native populations evolved greater tolerance for elevated heat conditions relative to native source populations. We assayed 935 field-collected and 325 common-garden thalli from 40 locations and as predicted, non-native populations had greater tolerance for ecologically-relevant extreme heat (40ºC) than did Japanese source populations. Non-native populations also had greater tolerance for cold and low-salinity stresses relative to source populations. The importance of local adaptation to warm temperatures during invasion was reinforced by evolution of parallel clines: populations from warmer, lower-latitude estuaries had greater heat tolerance than did populations from colder, higher-latitude estuaries in both Japan and eastern North America. We conclude that rapid evolution plays an important role in facilitating the invasion success of this and perhaps other non-native marine species. Genetically-informed ecological niche analyses readily generate clear predictions of phenotypic shifts during invasions, and may help to resolve debate over the frequency of niche conservatism versus rapid adaptation during invasion.

非本土物种的快速演化可助力其入侵成功，但近期综述研究表明，此类微演化（microevolution）极少能推动入侵生境中的气候生态位（climatic niche）发生扩张。然而，由于部分入侵事件起源于本土物种分布范围及其气候生态位中地理受限的区域，因此入侵过程中表型演化（phenotypic evolution）的频率、方向与强度可能遭到了低估。我们以红藻（red seaweed）细基江蓠（Gracilaria vermiculophylla）为研究对象，探讨了生态位偏移分析（niche-shift analyses）的应用价值：该物种在过去100年间从日本东北海岸扩散至北美、欧洲与西北非地区。整合遗传信息的气候生态位分析结果显示，本土源种群栖息于寒冷且季节波动强烈的生境，而多数非本土种群则分布于温暖、季节波动较弱的生境。这种气候生态位扩张现象预示，相较于本土源种群，非本土种群对高温环境的耐受能力更强。我们对来自40个采样点的935份野外采集样本与325份同质园（common-garden）培育的藻体（thalli）开展了耐受实验，结果正如预测那般：非本土种群对生态相关的极端高温（40℃）的耐受能力显著高于日本本土源种群；相较于本土源种群，非本土种群对低温与低盐胁迫的耐受能力也更强。入侵过程中对高温的本地适应的重要性，通过平行渐变群（parallel clines）的演化得到了进一步证实：在日本与北美东部地区，来自温暖低纬度河口的种群，其高温耐受能力均显著高于来自寒冷高纬度河口的种群。综上，快速演化在助力该物种乃至其他非本土海洋物种入侵成功的过程中发挥了关键作用。整合遗传信息的生态位分析方法可便捷地对入侵过程中的表型偏移做出清晰预测，或有助于解决关于入侵过程中生态位保守性（niche conservatism）与快速演化适应发生频率的学术争议。