RUI: Evaluating Mechanisms of Selection for the Maintenance of Sexual Dimorphism

性别差异在包括人类在内的动物中普遍存在，生物学家认为性别差异的进化机制有三种：由配偶竞争和配偶选择引起的性选择；2：雄性生殖角色的性别差异导致的自然选择；和3。自然选择：由于两性之间争夺食物而产生的自然选择自然条件下的野外实验将用于检验自然选择和性选择在两性二态性维持中的作用。尽管研究表明，性选择和生殖角色机制在自然种群中起作用，但对于食物竞争在两性异形维持中的作用几乎一无所知。问题是，在许多物种中，饮食上的性别差异通常与体型上的性别差异有关，这使得人们不清楚饮食上的差异是二态性的原因还是结果。拟议的研究通过关注喂养解剖学中的两性二态性来避免这个问题：蜂鸟的喙的大小和形状可以与鸟类访问的花朵的大小和形状相匹配。因此，拟议的研究将首次明确地将取食形态的性别差异与天然食物来源的取食性能的性别差异联系起来，并将自然选择和性选择对体型和解剖结构的影响分开。

Sexual differences are widespread in animals, including humans, and biologists recognize three mechanisms for their evolution: 1. Sexual selection resulting from mate competition and mate choice; 2: Natural selection resulting from sexual differences in reproductive roles of males; and 3. Natural selection resulting from competition between the sexes for food. Field experiments under natural conditions will be used to examine the roles of natural and sexual selection in the maintenance of sexual dimorphism.Although studies demonstrate that sexual selection and reproductive role mechanisms operate in natural populations, almost nothing is known about the role of food competition in the maintenance of sexual dimorphisms. The problem is that in many species, sexual differences in diet are often associated with sexual differences in size, making it unclear whether dietary differences are the cause or the consequence of dimorphism. The proposed studies avoid this problem by focusing on sexual dimorphisms in feeding anatomy: the beak size and shape of a hummingbird, which can be matched to the size and shape of the flowers the birds visit. Consequently, the proposed studies will be the first to unambiguously link sexual differences in feeding morphology to sexual differences in feeding performances at natural food sources, and to separate the effects of natural from sexual selection on body size and anatomy.