Odreitz Ulrike, Sefc Kristina M
Institute of Zoology, University of Graz, Universitätsplatz 2, 8010 Graz, Austria.
Behav Ecol Sociobiol. 2015;69(4):593-601. doi: 10.1007/s00265-014-1870-0. Epub 2015 Jan 17.
Non-sexual social selection can underlie the evolution of sexually monomorphic phenotypes. A causal relationship between territorial competition and sexual monomorphism predicts that male and female competitors should employ similar contest behavior and that contest outcome should depend on the same traits in males and females. We test this prediction in a sexually monomorphic cichlid fish of the genus in which males and females defend individual feeding territories. Lineages basal to are sexually dimorphic and have non-territorial females, suggesting that a switch to female territoriality and loss of sexual dimorphism occurred in the lineage. We compare rates of agonistic behavior and the effects of body size asymmetries on competitive success between male-male and female-female contests in an experimental setup. Body size asymmetry had the same effect in male and female contests, being negatively correlated with contest duration and positively correlated with the probability of winning. Male and female winners employed the same rates of frontal and lateral displays as well as charges against their opponents. Contest duration was longer in females. In tied contests, females displayed more than males. Our data suggest that intraspecific contest competition for territories selects for large body size in both sexes and support a link between the evolution of female territoriality and the loss of sexual size dimorphism in .
非性社会选择可能是两性单态表型进化的基础。领地竞争与两性单态之间的因果关系预测，雄性和雌性竞争者应采用相似的竞争行为，且竞争结果应取决于雄性和雌性的相同特征。我们在一种两性单态的丽鱼科鱼类中检验了这一预测，该属的雄性和雌性都保卫各自的觅食领地。该属的基部谱系是两性异形的，且雌性不具有领地性，这表明在该谱系中发生了向雌性领地性的转变以及两性异形的丧失。我们在一个实验装置中比较了雄性与雄性、雌性与雌性竞争中攻击行为的发生率以及体型不对称对竞争成功的影响。体型不对称在雄性和雌性竞争中具有相同的影响，与竞争持续时间呈负相关，与获胜概率呈正相关。雄性和雌性获胜者对对手采用正面和侧面展示以及冲锋的比率相同。雌性的竞争持续时间更长。在平局的竞争中，雌性比雄性展示得更多。我们的数据表明，种内对领地的竞争选择了两性的大体型，并支持了雌性领地性的进化与该属两性体型差异丧失之间的联系。
