Evolution of odorant receptor (OR) genes in perfume-making orchid bees

雄性兰花蜜蜂收集和积累复杂的和特定物种的挥发性化学物质（香水）的混合物，它们从环境中的各种来源收获，然后在求爱期间暴露，大概是为了向同种雌性传达雄性身份（物种）和/或质量（健身）。这种交流系统在昆虫中是独特的，因为获得雄性性别特征（香水）和雌性对其的偏好同时受到化学感受系统的控制，即通过编码嗅觉敏感性的基因家族联系在一起。这种遗传联系创造了未知的机会，共同进化的男性特征和女性的偏好，并可能促进香水驱动的生殖隔离和物种形成。在这里，我们建议（1）比较气味受体（OR）基因和OR基因表达在触角的两个最近分歧的同胞物种的Euglossa，（2）功能特征的分歧OR基因下的积极方向选择，（3）探索这些OR基因和相应的香水表型在中美洲的地理分布，（4）比较雄蜂和雌蜂触角中OR基因的表达以测试性别特异性嗅觉结构。这个基于感官的项目补充了正在进行的基于化学的香水差异化研究，并将增强我们对这种专门通信系统演变的理解。

Male orchid bees collect and accumulate complex and species-specific mixtures of volatile chemicals (perfumes), which they harvest from various sources in their environment and later expose during courtship, presumably to communicate male identity (species) and/or quality (fitness) to conspecific females. This communication system is unique among insects in that the acquisition of the male sex trait (perfume) and the female preference for it are simultaneously controlled by the chemosensory system, i.e. are linked through the gene families encoding olfactory sensitivity. This genetic linkage creates unexplored opportunities for coevolution of male trait and female preference, and may facilitate perfume-driven reproductive isolation and speciation. Here, we propose to (1) compare odorant receptor (OR) genes and OR gene expression in the antennae of two recently diverged sibling species of Euglossa, (2) functionally characterize diverged OR genes that are under positive directional selection, (3) explore the phylogeography of these OR genes and corresponding perfume phenotypes in Central America, and (4) compare OR gene expression in the antennae of male and female bees to test for sex-specific olfactory architectures. This sensory-based project complements ongoing chemistry-based research on perfume differentiation, and will enhance our understanding of the evolution of this specialized communication system.