Data from: Bioinvasion triggers rapid evolution of life-histories in freshwater snails

Biological invasions offer interesting situations to observe how novel interactions between closely related, formerly allopatric species may trigger phenotypic evolution in situ. Assuming that successful invaders are usually filtered to be competitively dominant, invasive and native species may follow different trajectories. Natives may evolve traits that minimize the negative impact of competition, while trait shifts in invasives should mostly reflect expansion dynamics, through selection for colonization ability and transiently enhanced mutation load at the colonization front. These ideas were tested through a large-scale common-garden experiment measuring life-history traits in two closely related snail species, one invasive and one native, co-occurring in a network of freshwater ponds in Guadeloupe. We looked for evidence of recent evolution by comparing uninvaded or recently invaded with long-invaded sites. The native species adopted a life history favoring rapid population growth (i.e. increased fecundity, earlier reproduction and increased juvenile survival) that may increase its prospects of coexistence with the more competitive invader. We discuss why these effects are more likely to result from genetic change than from maternal effects. The invader exhibited slightly decreased overall performances in recently colonized sites, consistent with a moderate expansion load resulting from local founder effects. Our study highlights a rare example of rapid life-history evolution following invasion.生物入侵（biological invasions）为探究亲缘关系相近、曾为异域分布（allopatric）的物种间全新相互作用如何原位触发表型进化（phenotypic evolution）提供了极具研究价值的场景。学界普遍认为，成功入侵的物种通常经筛选后具备竞争优势，因此入侵物种与本地物种往往会走上不同的演化轨迹。本地物种可能演化出能够弱化竞争负面影响的性状，而入侵物种的性状转变则主要反映其扩张动态——即通过对定殖能力的选择，以及在定殖前沿出现暂时性升高的突变负荷（mutation load）。上述假说已通过一项大规模共同花园实验（common-garden experiment）得到验证：该实验针对瓜德罗普岛淡水池塘群落中同域共存的两种亲缘关系相近的螺类——一种为入侵物种，另一种为本地物种——的生活史性状（life-history traits）展开了测量。研究通过对比未入侵、近期入侵与长期入侵的样地，寻找近期演化的相关证据。结果显示，本地物种采取了更利于种群快速增长的生活史策略，具体包括提升繁殖力、提前繁殖以及提高幼体存活率，这或可增强其与竞争力更强的入侵物种共存的潜力。我们进一步讨论了为何这些效应更可能由遗传改变而非母体效应（maternal effects）所导致。入侵物种在近期定殖的样地中整体表现略有下降，这与局部奠基者效应（founder effects）引发的中等程度扩张负荷相符。本研究揭示了入侵后快速发生生活史演化的罕见案例。