Red de Biología Evolutiva, Instituto de Ecología, A.C., Xalapa, Veracruz, Mexico.
Department of Biological Sciences, Ohio University, Athens, Ohio, United States of America.
PLoS One. 2013 Dec 9;8(12):e82723. doi: 10.1371/journal.pone.0082723. eCollection 2013.
The differential allocation hypothesis predicts that reproductive investment will be influenced by mate attractiveness, given a cost to reproduction and a tradeoff between current and future reproduction. We tested the differential allocation hypothesis in the swordtail fish Xiphophorus multilineatus, where males have genetically influenced (patroclinous inheritance) alternative mating tactics (ARTs) maintained by a tradeoff between being more attractive to females (mature later as larger courting males) and a higher probability of reaching sexual maturity (mature earlier as smaller sneaker males). Males in X. multilineatus do not provide parental care or other resources to the offspring. Allelic variation and copy number of the Mc4R gene on the Y-chromosome influences the size differences between males, however there is no variation in this gene on the X-chromosome. Therefore, to determine if mothers invested more in offspring of the larger courter males, we examined age to sexual maturity for daughters. We confirmed a tradeoff between number of offspring and female offspring's age to sexual maturity, corroborating that there is a cost to reproduction. In addition, the ART of their fathers significantly influenced the age at which daughters reached sexual maturity, suggesting increased maternal investment to daughters of courter males. The differential allocation we detected was influenced by how long the wild-caught mother had been in the laboratory, as there was a brood order by father genotype (ART) interaction. These results suggest that females can adjust their reproductive investment strategy, and that differential allocation is context specific. We hypothesize that one of two aspects of laboratory conditions produced this shift: increased female condition due to higher quality diet, and/or assessment of future mating opportunities due to isolation from males.
差异分配假说预测，在存在繁殖成本和当前繁殖与未来繁殖之间权衡的情况下，繁殖投资将受到配偶吸引力的影响。我们在剑尾鱼 Xiphophorus multilineatus 中测试了差异分配假说，其中雄性具有受遗传影响的（父系遗传）替代交配策略（ART），这种策略是通过在对雌性更有吸引力（作为更大的求爱雄性成熟较晚）和更高的性成熟概率（作为更小的偷偷摸摸雄性成熟较早）之间进行权衡来维持的。X. multilineatus 中的雄性不会为后代提供父母照顾或其他资源。Y 染色体上 Mc4R 基因的等位基因变异和拷贝数影响雄性之间的大小差异，但 X 染色体上没有这种基因的变异。因此，为了确定母亲是否会更多地投资于更大求爱雄性的后代，我们检查了女儿的性成熟年龄。我们证实了繁殖数量与雌性后代性成熟年龄之间的权衡，这证实了繁殖存在成本。此外，父亲的 ART 显著影响了女儿达到性成熟的年龄，表明对求爱雄性的女儿进行了更多的母性投资。我们检测到的差异分配受到野生捕获母亲在实验室中时间长短的影响，因为存在由父亲基因型（ART）交互作用的窝次差异。这些结果表明，雌性可以调整其繁殖投资策略，并且差异分配是特定于上下文的。我们假设实验室条件的两个方面之一产生了这种变化：由于高质量饮食，女性状况得到改善，以及/或者由于与雄性隔离而对未来交配机会的评估。
