Felmy Anja, Streiff Alena B, Jokela Jukka
Department of Biology, Aquatic Ecology Unit, Lund University, 22362 Lund, Sweden.
Department of Aquatic Ecology, EAWAG, Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland.
R Soc Open Sci. 2023 Oct 4;10(10):230532. doi: 10.1098/rsos.230532. eCollection 2023 Oct.
To understand mating-system evolution in self-compatible hermaphrodites, variation in selfing rates is highly relevant. Empirical studies are rarely designed to capture variation between individuals, instead often comparing species and populations. Yet, evolution primarily occurs within populations, rendering among-individual variation essential. Observed individual selfing rates depend on the environment (e.g. differences in mate availability) and individuals' propensity for selfing. We quantified individual variation in selfing propensity in the snail by conducting laboratory mating trials that manipulated mate availability (low versus moderate) and estimating selfing rates from progeny arrays. We also measured female lifetime fitness. We found substantial among-individual variation in selfing propensity, including pure selfers (32%), pure outcrossers (31%) and mixed-mating individuals that selfed and outcrossed (37%). Experimental levels of mate availability did not significantly affect selfing rates. Selfers had reduced female liftetime fitness. Our results show that the propensity for selfing can differ considerably among individuals, with similar proportions of selfers, outcrossers and mixed maters. As mate availability did not affect selfing, our 'moderate' experimental level of mate availability might still have been too low to prompt selfers to outcross. This and the observed fitness differences also cautiously suggest that investigating the heritability of selfing propensities might be worthwhile in this population.
为了理解自交亲和的雌雄同体生物的交配系统进化，自交率的变化具有高度相关性。实证研究很少旨在捕捉个体间的差异，而是常常比较物种和种群。然而，进化主要发生在种群内部，这使得个体间的差异至关重要。观察到的个体自交率取决于环境（例如配偶可获得性的差异）以及个体的自交倾向。我们通过进行实验室交配试验来量化蜗牛自交倾向的个体差异，该试验操纵了配偶可获得性（低与中等），并从子代阵列中估计自交率。我们还测量了雌性的终生适合度。我们发现自交倾向存在显著的个体间差异，包括纯自交者（32%）、纯异交者（31%）以及既自交又异交的混合交配个体（37%）。配偶可获得性的实验水平并未显著影响自交率。自交者的雌性终生适合度较低。我们的结果表明，自交倾向在个体间可能存在很大差异，自交者、异交者和混合交配者的比例相似。由于配偶可获得性并未影响自交，我们“中等”的配偶可获得性实验水平可能仍然过低，无法促使自交者进行异交。这一点以及观察到的适合度差异也谨慎地表明，在这个种群中研究自交倾向的遗传力可能是值得的。
