The persistence of coat color polymorphisms—such as the coexistence of melanistic and “wild-type” coat color—is an ongoing evolutionary puzzle. We tested the predictions of Gloger’s rule and the Temporal Segregation hypothesis that propose that melanistic individuals will (a) occur more frequently in closed tropical forest versus open habitat due to camouflage and thermoregulation advantages and (b) be more active during brighter times of the circadian and lunar cycle because black pigmentation is cryptic under bright illumination. Based on 10 years of camera trap records of jaguar and oncilla from dense tropical forest in Costa Rica, we compared activity and relative abundance of non-melanistic wild-type morphs (rosetted or spotted) versus melanistic morphs. Twenty-five percent of jaguar records in dense forest were melanistic compared with the global average of 10% in both open and closed habitats; 32% of oncilla records were melanistic compared with 18% overall in Brazil. Overlap analysis indicated that melanistic jaguars were more active during daylight hours compared with non-melanistic jaguars, which were more nocturnal and crepuscular. Likewise, melanistic oncillas were significantly more diurnal than non-melanistic oncillas; melanistic oncillas were also more active during full moon, while non-melanistic oncillas were less active. These results imply that melanistic jaguar and oncilla enjoy the adaptive benefits of superior camouflage when inhabiting dense forest and accrue a fitness advantage when hunting during conditions of brighter illumination. If true, natural selection would ensure that melanistic individuals persist when dense forest is retained but may be threatened by deforestation and accelerating human presence.

中文翻译：

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哥斯达黎加 Jaguar 和 Oncilla 黑色素的自然选择：Gloger 规则和时间隔离假设的检验

毛色多态性的持续存在——例如黑色素和“野生型”毛色的共存——是一个持续的进化难题。我们测试了 Gloger 规则和时间隔离假设的预测，这些假设提出黑色素个体将 (a) 由于伪装和体温调节优势而更频繁地出现在封闭的热带森林中而不是开放的栖息地中，并且 (b) 在昼夜节律的光明时期更加活跃和月球周期，因为黑色色素沉着在明亮的照明下是神秘的。基于 10 年对哥斯达黎加茂密热带森林中美洲虎和 Oncilla 的相机陷阱记录，我们比较了非黑化野生型（玫瑰花或斑点）与黑化型变种的活动和相对丰度。茂密森林中 25% 的美洲豹记录是黑化的，而开放和封闭栖息地的全球平均水平为 10%；32% 的 oncilla 记录是黑色素的，而巴西的总体比例为 18%。重叠分析表明，与非黑化美洲虎相比，黑化美洲虎在白天更活跃，非黑化美洲虎在夜间和黄昏时更活跃。同样，黑化的 oncillas 比非黑化的 oncillas 明显更昼夜。满月期间黑色素瘤也更活跃，而非黑色素瘤则不太活跃。这些结果意味着黑化美洲虎和 Oncilla 在栖息在茂密的森林中时享有优越伪装的适应性优势，并在更明亮的照明条件下狩猎时获得健康优势。如果属实，