Data from: Gene expression stasis and plasticity following migration into a foreign environment

Selection against migrants is key to maintaining genetic differences between populations linked by dispersal. However, migrants may mitigate fitness costs by proactively choosing among available habitats, or by phenotypic plasticity. We previously reported that a reciprocal transplant of lake and stream stickleback (Gasterosteus aculeatus) found little support for divergent selection. Here, we revisit that experiment to test whether phenotypic plasticity in gene expression may have helped migrants adjust to unfamiliar habitats. We measured gene expression profiles in stickleback via TagSeq and tested whether migrants between lake and stream habitats exhibited a plastic response to their new environment that allowed them to converge on the expression profile of adapted natives. We report extensive gene expression differences between genetically divergent lake and stream stickleback, despite gene flow. But for many genes, expression was highly plastic. Fish transplanted into the adjoining habitat partially converged on the expression profile typical of natives from their new habitat. This suggests that expression plasticity may soften the impact of migration. Nonetheless, lake and stream fish differed in survival rates and parasite infection rates in our study, implying that expression plasticity is not fast or extensive enough to fully homogenize fish performance.

对迁徙个体的选择是维持通过扩散连接的种群间遗传差异的核心机制。然而，迁徙个体可通过主动选择适宜生境或借助表型可塑性（phenotypic plasticity）来缓解适合度代价。我们此前曾针对湖泊与溪流棘鱼（Gasterosteus aculeatus）开展互易移植实验，研究结果几乎未发现趋异选择的相关证据。本研究重新审视该实验，旨在检验基因表达层面的表型可塑性是否可帮助迁徙个体适应陌生生境。我们通过TagSeq技术测定棘鱼的基因表达谱，并检验湖泊与溪流生境间的迁徙个体是否对新环境产生了可塑性响应，进而使其表达谱能够趋近于已适应该生境的本土种群的表达谱。本研究发现，尽管存在基因流（gene flow），遗传分化显著的湖泊与溪流棘鱼之间仍存在广泛的基因表达差异。但对于多数基因而言，其表达具有高度的可塑性。被移植到相邻生境的个体，其基因表达谱部分趋近于该新生境本土种群的典型表达谱。这表明表达可塑性或许可缓解迁徙带来的影响。尽管如此，本研究中湖泊与溪流棘鱼的存活率及寄生虫感染率仍存在显著差异，这意味着表达可塑性的响应速度与覆盖广度均不足以完全使种群的生存表现趋于一致。