Invasion biology: comparing scales of local genetic adaptation to exotic predators by prey with high and low dispersal potential

人类活动造成的环境变化使外来捕食者和竞争者能够将其地理范围扩展到加拿大。例如，1997/98年厄尔尼诺期间海面温度上升，使亚热带的海岸蟹幼虫在加拿大西部海岸变形，捕食四种密切相关的本地蜗牛。这些温带蜗牛物种的外壳很容易受到来自热带地区的捕食者的专门破壳附属物的攻击。因此，气候驱动的亚热带食肉动物物种的范围扩张可能会导致温带猎物物种的范围收缩，除非它们能迅速进化出更厚的盔甲。这是一个很好的系统，研究猎物迁移对适应亚热带捕食者的影响。这四个潮间带腹足类动物的生态相似，但在其扩散潜力有很大的不同：两个物种有一个长寿命的自由游泳的幼虫阶段和两个物种已经失去了自由游泳的幼虫阶段，因此分散只能爬行。

Environmental change caused by human activities is allowing exotic predators and competitors to extend their geographical ranges into Canada. For example, increased sea surface temperatures during the 1997/98 El Niño allowed larvae of the subtropical lined shore crab to metamorphose on western Canadian shores and prey on four closely-related species of indigenous snails. These temperate snail species have shells that are vulnerable to the specialized shell-breaking appendages of predators from more tropical regions. Consequently, climate-driven range expansion of subtropical predator species may result in range contraction by temperate prey species unless they can quickly evolve thicker armour. This is an excellent system for studying the effect of prey migration on adaptation to subtropical predators. These four intertidal gastropods are ecologically similar but differ considerably in their dispersal potential: two species have a long-lived free-swimming larval stage and two species have lost the free-swimming larval stage and as a result disperse only by crawling.