Max Planck Institute of Evolutionary Biology August-Thienemann Str. 2, Plön, 24306, Germany.
Department of Biology, Texas A&M University 3258 TAMU, College Station, Texas, 77843, USA.
Ecol Evol. 2014 Jan;4(1):67-78. doi: 10.1002/ece3.907. Epub 2013 Dec 11.
Size-assortative mating is a nonrandom association of body size between members of mating pairs and is expected to be common in species with mutual preferences for body size. In this study, we investigated whether there is direct evidence for size-assortative mating in two species of pipefishes, Syngnathus floridae and S. typhle, that share the characteristics of male pregnancy, sex-role reversal, and a polygynandrous mating system. We take advantage of microsatellite-based "genetic-capture" techniques to match wild-caught females with female genotypes reconstructed from broods of pregnant males and use these data to explore patterns of size-assortative mating in these species. We also develop a simulation model to explore how positive, negative, and antagonistic preferences of each sex for body size affect size-assortative mating. Contrary to expectations, we were unable to find any evidence of size-assortative mating in either species at different geographic locations or at different sampling times. Furthermore, two traits that potentially confer a fitness advantage in terms of reproductive success, female mating order and number of eggs transferred per female, do not affect pairing patterns in the wild. Results from model simulations demonstrate that strong mating preferences are unlikely to explain the observed patterns of mating in the studied populations. Our study shows that individual mating preferences, as ascertained by laboratory-based mating trials, can be decoupled from realized patterns of mating in the wild, and therefore, field studies are also necessary to determine actual patterns of mate choice in nature. We conclude that this disconnect between preferences and assortative mating is likely due to ecological constraints and multiple mating that may limit mate choice in natural populations.
体型选择交配是指交配对成员之间的体型非随机关联，并且预计在具有对体型相互偏好的物种中很常见。在这项研究中，我们调查了两种海龙，即佛罗里达海龙（Syngnathus floridae）和 Typhle 海龙（S. typhle），它们是否存在体型选择交配的直接证据。这两种海龙具有雄性怀孕、性别逆转和多雄多雌交配系统的特征。我们利用基于微卫星的“遗传捕获”技术，将野生捕获的雌性与从怀孕雄性的幼崽中重建的雌性基因型相匹配，并利用这些数据来探索这些物种的体型选择交配模式。我们还开发了一个模拟模型，以探索每个性别对体型的正、负和拮抗偏好如何影响体型选择交配。与预期相反，我们无法在不同地理地点或不同采样时间的两个物种中找到任何体型选择交配的证据。此外，两个可能在繁殖成功方面具有优势的特征，即雌性交配顺序和每个雌性转移的卵子数量，不会影响野生种群的配对模式。模型模拟的结果表明，强烈的交配偏好不太可能解释研究种群中观察到的交配模式。我们的研究表明，个体交配偏好，如通过实验室交配试验确定的偏好，可以与野外实际的交配模式脱钩，因此，野外研究也是确定自然种群中实际选择配偶模式所必需的。我们得出结论，这种偏好与选择交配之间的脱节可能是由于生态限制和多次交配导致的，这些因素可能限制了自然种群中的配偶选择。
