Hews Diana K
Department of Zoology, University of Texas, Austin, Texas, 78712, USA.
Evolution. 1990 Dec;44(8):1956-1966. doi: 10.1111/j.1558-5646.1990.tb04302.x.
I examined sexual selection in the iguanid lizard Uta palmeri by measuring phenotypic selection in a cohort of males. Relative fitness was estimated by copulation rate from one breeding season, and I analyzed selection on five morphological traits (snout-vent length, mass, jaw length, head width, and head depth) and on male territory quality. Only territory quality and head depth were identified as direct targets of selection in a linear selection gradient analysis. Head depth was suggested to also be subject to quadratic selection. All traits exhibited significant directional selection differentials, suggesting indirect selection also was present because of the correlation of these traits with direct targets of selection. I used these results to generate hypotheses about the mechanisms of selection. For traits not identified as direct targets of selection (snout-vent length, mass, head width, jaw length), I could accept the null hypothesis of no female preference for the analyzed male traits; if these morphological traits were preferred by females in mate choice, they would have been identified as direct targets of selection. Exploring possible functional relationships within the cohort, I found that all five morphological traits contributed to explaining variation in territorial status. And in staged aggressive interactions between males that were similar in snout-vent length and mass, winning was associated only with greater head depth and not with head width or jaw length. Several possible interpretations of these results are presented. This study suggests that differential mating success arising from variation in territory quality gives rise to indirect selection on morphology. The possible mechanisms giving rise to the proposed direct selection on head depth require further study.
我通过测量一群雄性的表型选择，研究了变色蜥属蜥蜴帕尔默氏强棱蜥的性选择。通过一个繁殖季节的交配率估算相对适合度，并且我分析了对五个形态特征（吻肛长度、体重、颌长、头宽和头深）以及雄性领地质量的选择。在一次线性选择梯度分析中，只有领地质量和头深被确定为选择的直接目标。有人提出头深也受到二次选择。所有特征都表现出显著的定向选择差异，这表明由于这些特征与选择的直接目标相关，间接选择也存在。我利用这些结果生成了关于选择机制的假设。对于未被确定为选择直接目标的特征（吻肛长度、体重、头宽、颌长），我可以接受关于雌性对所分析的雄性特征没有偏好的零假设；如果这些形态特征在配偶选择中受到雌性偏好，它们就会被确定为选择的直接目标。通过探究群体内可能的功能关系，我发现所有五个形态特征都有助于解释领地地位的差异。并且在吻肛长度和体重相似的雄性之间进行的阶段性攻击性互动中，获胜仅与更大的头深相关，而与头宽或颌长无关。本文给出了这些结果的几种可能解释。这项研究表明，由领地质量差异导致的不同交配成功率会引起对形态的间接选择。导致对头深提出直接选择的可能机制需要进一步研究。
