Data from: Estimating encounter rates as the first step of sexual selection in the lizard Anolis sagrei

How individuals move through their environment dictates which other individuals they encounter, determining their social and reproductive interactions and the extent to which they experience sexual selection. Specifically, females rarely have the option of mating with all males in a population—they can only choose among the males they encounter. Further, quantifying phenotypic differences between the males that females encounter and those that sire females’ offspring lends insight into how social and reproductive interactions shape male phenotypes. We used an explicitly spatiotemporal Markov chain model to estimate the number of potential mates of Anolis sagrei lizards from their movement behavior, and used genetic paternity assignments to quantify sexual selection on males. Females frequently encountered and mated with multiple males, offering ample opportunity for female mate choice. Sexual selection favored males that were bigger and moved over larger areas, though the effect of body size cannot be disentangled from last-male precedence. Our approach corroborates some patterns of sexual selection previously hypothesized in anoles based on describing them as territorial, whereas other results, including female multiple mating itself, are at odds with territorial polygyny, offering insight into discrepancies in other taxa between behavioral and genetic descriptions of mating systems.

个体在环境中的移动模式，决定了其所能遭遇的其他个体，进而塑造其社交与繁殖互动，以及其经历性选择（sexual selection）的程度。具体而言，种群中的雌性极少有机会与所有雄性完成交配，仅能在其所遭遇的雄性个体中进行配偶选择。此外，量化雌性遭遇的雄性与成功使雌性繁育后代的雄性之间的表型（phenotypic）差异，有助于揭示社交与繁殖互动如何塑造雄性的表型特征。本研究采用显式时空马尔可夫链模型（spatiotemporal Markov chain model），基于萨氏安乐蜥（Anolis sagrei）的移动行为估算其潜在配偶数量，并结合遗传父权鉴定（genetic paternity assignments）量化雄性所经历的性选择。雌性个体频繁遭遇并与多只雄性交配，为雌性配偶选择提供了充足的机会。性选择倾向于体型更大、活动范围更广的雄性，但体型大小的效应无法与最后雄性交配优势（last-male precedence）相区分。本研究方法验证了此前基于领地性特征对安乐蜥（anoles）提出的部分性选择模式假说，但包括雌性多重交配在内的其他研究结果，则与领地性一夫多妻制相悖，这为揭示其他类群中交配系统的行为学描述与遗传学描述之间的差异提供了新的视角。