Data from: Climatic conditions cause spatially dynamic polygyny thresholds in a large mammal

The polygyny threshold (PT) is a critical transition point in the sexual selection process for many organisms in natural populations, characterizing when females choose to mate with an already mated male over an unmated one to improve fitness. Understanding its causes and consequences is therefore of high interest. While both theoretical and empirical work suggest that the degree of polygyny within a species is plastic and a function of male inequality, the functional relationship between underlying availability of resources occupied by breeding males under variable climatic conditions and the dynamics of PTs across space and time has received less attention. Here, we use a standardized measure of male mating inequality as the culmination of female mate choices to analyse how spatially dynamic PTs in a naturally regulated feral horse (Equus ferus caballus) population emerge along a geographic gradient in a known, limiting resource (freshwater) each year from variable climatic conditions. Polygyny threshold distance from permanent freshwater increased with increasing precipitation during the breeding season of each year, suggesting a relationship between annual resource availability and female mate choice. The mechanism by which climatic conditions underpin the spatial dynamics of PTs was likely through precipitation providing ephemeral freshwater sources across the study area that effectively weakened the gradient in availability of permanent freshwater, thereby providing mating males that occupied home ranges far from permanent water with access to this limiting resource and enabling them to attract and retain females. Increased precipitation also coincided with a decreased proportion of males in the population that experienced sexual selection pressure attributed to female mate choice in relation to the acquisition and/or defence of freshwater sources. Climatic conditions caused spatial shifts in PTs annually along the geographic gradient in resource availability. Our findings reveal that such environmental gradients may either buffer or amplify impacts of climatic variation on selection pressure operating in natural populations, and emphasize the importance of integrating spatially explicit PTs with atmospheric fluctuations when predicting the effect of climatic change on selection processes within populations that occupy environmental gradients.多配偶阈值（polygyny threshold）是自然种群中多数生物性选择过程的关键转折点，用于表征雌性为提升自身适合度，选择与已交配雄性而非未交配雄性交配的临界条件。因此，解析其成因与影响具备重要研究价值。尽管理论与实证研究均表明，物种种内的多配偶程度具有可塑性，且是雄性交配不平等程度的函数，但在可变气候条件下，繁殖雄性所占据的基础资源可用性，与多配偶阈值在时空维度上的动态变化之间的功能关系，尚未得到足够关注。 本研究采用以雌性配偶选择最终结果为依据的标准化雄性交配不平等度量指标，分析了每年受可变气候条件影响的自然调控野生马（Equus ferus caballus）种群中，沿已知限制性资源（淡水）地理梯度形成的空间动态多配偶阈值的形成机制。研究发现，繁殖季内降水量的增加会导致多配偶阈值与永久淡水的距离增大，这表明年度资源可用性与雌性配偶选择之间存在显著关联。 气候条件驱动多配偶阈值空间动态的潜在机制，可能是降水量为研究区域带来了临时淡水资源，有效削弱了永久淡水的可用性梯度，从而使占据远离永久水源家域的繁殖雄性能够获取该限制性资源，并得以吸引和留住雌性。降水量增加的同时，种群中因雌性配偶选择（与淡水获取和/或防御相关）而承受性选择压力的雄性比例也有所下降。 气候条件每年都会驱动多配偶阈值沿资源可用性的地理梯度发生空间位移。本研究结果表明，这类环境梯度既可能缓冲也可能放大气候变异对自然种群选择压力的影响，并强调在预测气候变化对占据环境梯度的种群内选择过程的影响时，将空间显式（spatially explicit）的多配偶阈值与大气波动相结合的重要性。