Martin A M, Festa-Bianchet M, Coltman D W, Pelletier F
Département de biologie, Université de Sherbrooke, Sherbrooke, QC, Canada; Canada Research Chair in Evolutionary Demography and Conservation, Département de biologie, Université de Sherbrooke, Sherbrooke, QC, Canada.
J Evol Biol. 2015 Jan;28(1):223-30. doi: 10.1111/jeb.12558. Epub 2014 Dec 11.
The reliability and consistency of the many measures proposed to quantify sexual selection have been questioned for decades. Realized selection on quantitative characters measured by the selection differential i was approximated by metrics based on variance in breeding success, using either the opportunity for sexual selection Is or indices of inequality. There is no consensus about which metric best approximates realized selection on sexual characters. Recently, the opportunity for selection on character mean OSM was proposed to quantify the maximum potential selection on characters. Using 21 years of data on bighorn sheep (Ovis canadensis), we investigated the correlations between seven indices of inequality, Is , OSM and i on horn length of males. Bighorn sheep are ideal for this comparison because they are highly polygynous and sexually dimorphic, ram horn length is under strong sexual selection, and we have detailed knowledge of individual breeding success. Different metrics provided conflicting information, potentially leading to spurious conclusions about selection patterns. Iδ, an index of breeding inequality, and, to a lesser extent, Is showed the highest correlation with i on horn length, suggesting that these indices document breeding inequality in a selection context. OSM on horn length was strongly correlated with i, Is and indices of inequality. By integrating information on both realized sexual selection and breeding inequality, OSM appeared to be the best proxy of sexual selection and may be best suited to explore its ecological bases.
数十年来，许多用于量化性选择的测量方法的可靠性和一致性一直受到质疑。通过选择差i来衡量的对数量性状的实际选择，是通过基于繁殖成功率方差的指标来近似的，使用性选择机会Is或不平等指数。关于哪种指标最能近似对性性状的实际选择，目前尚无共识。最近，提出了性状均值选择机会（OSM）来量化对性状的最大潜在选择。利用21年的大角羊（加拿大盘羊）数据，我们研究了七个不平等指数、Is、OSM与雄性角长度的选择差i之间的相关性。大角羊是进行这种比较的理想对象，因为它们高度一夫多妻且具有两性异形，公羊角的长度受到强烈的性选择，而且我们对个体的繁殖成功率有详细了解。不同的指标提供了相互矛盾的信息，可能导致关于选择模式的虚假结论。繁殖不平等指数Iδ，以及在较小程度上的Is，与角长度的选择差i显示出最高的相关性，这表明这些指数在选择背景下记录了繁殖不平等。角长度的OSM与选择差i、Is和不平等指数密切相关。通过整合关于实际性选择和繁殖不平等的信息，OSM似乎是性选择的最佳代理指标，可能最适合探索其生态基础。
