Green Leon, Havenhand Jonathan N, Kvarnemo Charlotta
Department of Biological and Environmental Sciences University of Gothenburg Gothenburg Sweden.
Linnaeus Centre for Marine Evolutionary Biology University of Gothenburg Gothenburg Sweden.
Evol Appl. 2019 Sep 28;13(3):533-544. doi: 10.1111/eva.12859. eCollection 2020 Mar.
Invasive species may quickly colonize novel environments, which could be attributed to both phenotypic plasticity and an ability to locally adapt. Reproductive traits are expected to be under strong selection when the new environment limits reproductive success of the invading species. This may be especially important for external fertilizers, which release sperm and eggs into the new environment. Despite adult tolerance to high salinity, the invasive fish (round goby) is absent from fully marine regions of the Baltic Sea, raising the possibility that its distribution is limited by tolerance during earlier life stages. Here, we investigate the hypothesis that the spread of is limited by sperm function in novel salinities. We sampled sperm from two invasion fronts with higher and lower salinities in the Baltic Sea and tested them across a range of salinity levels. We found that sperm velocity and percentage of motile sperm declined in salinity levels higher and lower than those currently experienced by the Baltic Sea populations, with different performance curves for the two fronts. Sperm velocity also peaked closer to the home salinity conditions in each respective invasion front, with older localities showing an increased fit to local conditions. By calculating how the sperm velocity has changed over generations, we show this phenotypic shift to be in the range of other fish species under strong selection, indicating ongoing local adaptation or epigenetic acclimation to their novel environment. These results show that while immigrant reproductive dysfunction appears to at least partly limit the distribution of invasive in the Baltic Sea, local adaptation to novel environments could enable future spread beyond their current boundaries.
入侵物种可能会迅速在新环境中定殖，这可能归因于表型可塑性和局部适应能力。当新环境限制入侵物种的繁殖成功率时，生殖性状预计会受到强烈选择。这对于将精子和卵子释放到新环境中的体外受精者可能尤为重要。尽管成年圆口铜鱼能耐受高盐度，但在波罗的海的完全海洋区域却没有这种入侵鱼类，这增加了其分布受到早期生命阶段耐受性限制的可能性。在这里，我们研究了圆口铜鱼的扩散受到新盐度条件下精子功能限制这一假设。我们从波罗的海盐度较高和较低的两个入侵前沿采集了精子，并在一系列盐度水平下对其进行了测试。我们发现，当盐度高于或低于波罗的海种群目前所经历的盐度水平时，精子速度和活动精子百分比都会下降，两个前沿的表现曲线不同。每个入侵前沿的精子速度也在更接近本地盐度条件时达到峰值，较老的区域显示出对当地条件的适应性增强。通过计算精子速度在几代间的变化，我们表明这种表型转变处于其他受到强烈选择的鱼类物种的范围内，表明正在进行局部适应或对新环境的表观遗传适应。这些结果表明，虽然外来生殖功能障碍似乎至少部分限制了入侵圆口铜鱼在波罗的海的分布，但对新环境的局部适应可能使其未来扩散到当前边界之外。
