Bonenfant Christophe, Gaillard Jean-michel, Dray Stéphane, Loison Anne, Royer Manuela, Chessel Daniel
Université de Lyon, Université Lyon 1, CNRS, UMR 5558, Laboratoire de Biométrie et Biologic Evolutive, 43 Boulevard du 11 novembre 1918, Villeurbanne F-69622, France.
Ecology. 2007 Dec;88(12):3202-8. doi: 10.1890/07-0129.1.
The study of sexual segregation has received increasing attention over the last two decades. Several hypotheses have been proposed to explain the existence of sexual segregation, such as the "predation risk hypothesis," the "forage selection hypothesis," and the "activity budget hypothesis." Testing which hypothesis drives sexual segregation is hampered, however, by the lack of consensus regarding a formal measurement of sexual segregation. By using a derivation of the well-known chi-square (here called the sexual segregation and aggregation statistic [SSAS]) instead of existent segregation coefficients, we offer a reliable way to test for temporal variation in the occurrence of sexual segregation and aggregation, even in cases where a large proportion of animals are observed alone. A randomization procedure provides a test for the null hypothesis of independence of the distributions of males and females among the groups. The usefulness of SSAS in the study of sexual segregation is demonstrated with three case studies on ungulate populations belonging to species with contrasting life histories and annual grouping patterns (isard, red deer, and roe deer). The existent segregation coefficients were unreliable since, for a given value, sexual segregation could or could not occur. Similarly, the existent segregation coefficients performed badly when males and females aggregated. The new SSAS was not prone to such limitations and allowed clear conclusions regarding whether males and females segregate, aggregate, or simply mix at random applicable to all species.
在过去二十年中，对性别隔离的研究受到了越来越多的关注。已经提出了几种假说来解释性别隔离的存在，例如“捕食风险假说”、“觅食选择假说”和“活动预算假说”。然而，由于在性别隔离的正式测量方面缺乏共识，检验哪种假说驱动性别隔离受到了阻碍。通过使用著名的卡方统计量的一种衍生形式（这里称为性别隔离和聚集统计量[SSAS]），而不是现有的隔离系数，我们提供了一种可靠的方法来检验性别隔离和聚集现象发生的时间变化，即使在很大一部分动物是单独被观察到的情况下也是如此。一种随机化程序为检验雄性和雌性在各群体中分布独立的零假设提供了一种方法。通过对三种有蹄类动物种群的案例研究（伊比利亚盘羊、马鹿和狍，它们属于具有不同生活史和年度分组模式的物种），证明了SSAS在性别隔离研究中的有用性。现有的隔离系数不可靠，因为对于给定的值，可能会发生性别隔离，也可能不会发生。同样，当雄性和雌性聚集时，现有的隔离系数表现不佳。新的SSAS不容易受到此类限制，并且能够就雄性和雌性是隔离、聚集还是仅仅随机混合得出适用于所有物种的明确结论。
