Doctoral Dissertation Research: Examining the evolutionary significance of chest patch coloration in a wild primate population

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In animal species, a variety of social and physiological cues are thought to convey information about an individual’s health, status, rank, or reproductive fitness to other individuals. Many primate species, for example, rely on social cues about status and rank of other group members to gauge competitiveness and mate quality, which requires the ability to keep track of multiple individuals. However, there may be an upper limit to how many individuals can be recognized. In this doctoral dissertation project, the investigator studies a primate species with very large group sizes to examine whether male chest patch coloration may replace social knowledge of rank as a signal of male competitive ability. The project directly engages with evolutionary theories about trade-offs between social and morphological indicators of reproductive fitness, specifically advancing knowledge about the social and ecological environments that favor the evolution of costly visual signals (like chest coloration) relative to social knowledge as a means to appraise fighting ability of competitors. While conducting the proposed research, the investigator continues her involvement in local public science engagement to help foster an interest in science among young students of all backgrounds, improve science literacy in her local community, and promote open science communication to build trust between researchers and the public. The colored patch on the chest of male geladas has been hypothesized to be the product of sexual selection -- a quality signal to ward off would-be rival males. This research empirically tests the relationship between the intensity of male chest color, physiology, and reproductive fitness in a wild population of geladas. The investigators first examine what might cause red chests at a mechanistic level by analyzing color-gauged photographs taken from individually-known adult males to determine if male redness is associated with testosterone levels and/or gene expression related to vascularization and blood flow in the local tissue. At a functional level, the investigators then use demographic data paired with individual male redness to determine whether redder chests are associated with a longer reproductive tenure for those males, and whether this contributes to more offspring in the long-term, as determined by paternity testing of all infants.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.