Rispoli V F, Wilson A B
Zoological Museum, University of Zurich, Zurich, Switzerland.
J Evol Biol. 2008 Jan;21(1):30-38. doi: 10.1111/j.1420-9101.2007.01470.x. Epub 2007 Nov 22.
The sex-role reversed pipefish Syngnathus typhle is a member of the Syngnathidae, a family of fishes in which males brood embryos on their body surface. As in most ectotherms, embryonic development is highly temperature dependent in syngnathids and male brooding periods are extended when water temperatures are reduced. The influence of temperature on reproduction is expected to effectively truncate the breeding season and reduce fecundity in cold waters, potentially enhancing the opportunity for both fecundity and sexual selection. We studied spatial variation in the morphology and reproductive biology of S. typhle in five European populations which vary in latitude and water temperature. Microsatellite analyses indicated that the average number of male mates per population ranged between 1.3 and 3.7. The frequency of multiple mating by males was negatively correlated with the degree of sexual size dimorphism in each population, suggesting that disproportionate increases in female fecundity may be able to compensate for increased male brood pouch capacity. Both sexes were larger and males had an increased brood size where water temperatures during the breeding season were lower. Morphological variation among populations may be mediated by differences in fecundity selection associated with different optimal reproductive strategies in cold and warm water environments.
性角色反转的尖海龙是海龙科的一员，海龙科鱼类中雄性在体表孵化胚胎。与大多数变温动物一样，海龙科动物的胚胎发育高度依赖温度，水温降低时雄性的孵化期会延长。预计温度对繁殖的影响会有效缩短繁殖季节并降低冷水环境中的繁殖力，这可能会增加繁殖力和性选择的机会。我们研究了五个欧洲种群中尖海龙形态和生殖生物学的空间变异，这些种群在纬度和水温上存在差异。微卫星分析表明，每个种群中雄性配偶的平均数量在1.3至3.7之间。雄性多次交配的频率与每个种群的两性体型差异程度呈负相关，这表明雌性繁殖力的不成比例增加可能能够补偿雄性育儿袋容量的增加。在繁殖季节水温较低的地方，两性体型都更大，雄性的育儿数量也更多。种群间的形态变异可能由与冷水和温水环境中不同最佳繁殖策略相关的繁殖力选择差异所介导。
