Morphological data of Littorina obtusata populations from reciprocal transplant experiments in the Gulf of Maine conducted 20 years apart

The impact of invasive predators during the early stages of invasion is often variable in space and time. Such variation is expected to initially favor plasticity in prey defenses but fixed defenses as invaders become established. Coincident with the range expansion of the invasive green crab (Carcinus maenas) in the Gulf of Maine we document rapid changes in shell thickness – a key defense against shell crushing predators – of an intertidal snail (Littorina obtusata). These data summarize the results of reciprocal transplant experiments between snail (Littorina obtusata) populations in the northern and southern Gulf of Maine that were conducted 20 years apart. The results revealed that temporal shifts in snail shell thickness were driven by the evolution of increased trait means and erosion of thickness plasticity. The virtual elimination of the trade-off in snail tissue mass that often accompanies thicker shells is consistent with the evolution of fixed defenses under increasingly certain predation risk and are therefore consistent with the predicted impacts of spatiotemporal changes in green crab abundance throughout the Gulf of Maine.

入侵捕食者在入侵初期的影响通常存在空间与时间维度上的变异。此类变异最初会促使猎物防御策略呈现可塑性，而当入侵物种成功定殖后，则会倾向于选择固定防御策略。伴随入侵性欧洲绿蟹（Carcinus maenas）在缅因湾的分布扩张，我们记录了潮间带滨螺（Littorina obtusata）壳厚这一抵御碎壳捕食者的关键防御性状的快速变化。本数据集总结了相隔20年开展的缅因湾北部与南部滨螺（Littorina obtusata）种群间互易移植实验的研究结果。研究结果显示，滨螺壳厚的时间动态变化由性状均值提升以及壳厚可塑性的消退共同驱动。伴随壳厚增加通常伴随出现的螺软组织重量权衡关系几乎完全消失，这与捕食风险日益确定的环境下固定防御策略的演化规律相符，同时也与缅因湾全境绿蟹种群丰度的时空变化所带来的预期影响一致。