Ecology and Evolution of Melanism in Big Cats: Case Study with Black Leopards and Jaguars

Abstract

Variations in animal coloration have intrigued evolutionary biologists for a long time. Among the observed pigmentation polymorphisms, melanism has been reported in multiple organisms (influencing several biological factors), and classical hypothesis has suggested that such variant can present adaptive advantages under certain ecological conditions. In leopards (Panthera pardus) and jaguars (Panthera onca), melanism is caused by recessive and dominant mutations in the ASIP and MC1R genes, respectively. This chapter is focused on melanism in these two species, aiming to analyze its geographic pattern. About 623 leopard and 980 jaguar records that were used as baseline for modeling and statistical analyses were obtained. The frequency of melanism was 10% for both species. In leopards, melanism was present in five subspecies and strongly associated with moist forests, especially in Southeast Asia. In jaguars, melanism was totally absent from open and periodically flooded landscapes; in contrast, forests displayed a frequency that was similar to the expectations. The analyses of the environmental predictors suggest a relevant role for factors such as moisture and temperature. These observations support the hypothesis that melanism in big cats is not a neutral polymorphism (influenced by natural selection), leading to a nonrandom geographic distribution of this coloration phenotype.

Natural Selection of Melanism in Costa Rican Jaguar and Oncilla: A Test of Gloger’s Rule and the Temporal Segregation Hypothesis

“…Of the six felid species that occupy Costa Rica, three are known to exhibit melanistic polymorphisms-jaguar (Panthera onca), jaguarundi (Herpailurus yagouaroundi), and northern tiger cat (Leopardus tigrinus oncilla); there are no records of melanistic puma (Puma concolor) or ocelot (Leopardus pardalis) in Costa Rica, and melanistic margay (Leopardus wiedii) have only recently been reported . It is reported that about 10% of jaguars globally are melanistic (Silva, 2017), and melanism in this species is inherited as a dominant trait caused by a 15-bp deletion in the MC1R gene that produces eumelanin in the background regions of the coat (Eizirik et al, 2003;Haag et al, 2010). As of this writing, there are only two published records of melanistic jaguar in Costa Rica in this century (Cart ın & Carrillo, 2009;Sa´enz-Bolaños et al, 2015).…”

“…Of the 41 species of felids (Kitchener et al, 2017), 14 species exhibit a melanistic (black) coat morph that coexists with a wild-type "non-melanistic" coat pattern of visible spots, rosettes, or uniform color (Graipel et al, 2019;Schneider et al, 2012;Silva, 2017;Silva et al, 2016). The presence of alternative color morphs that coexist within a population, called coat color polymorphism, has long presented an evolutionary puzzle (Forsman et al, 2008;Graipel et al, 2014).…”

“…The presence of alternative color morphs that coexist within a population, called coat color polymorphism, has long presented an evolutionary puzzle (Forsman et al, 2008;Graipel et al, 2014). The multiple independent evolutionary origins of the melanistic mutation in Felidae (at least eight) and the high frequency of color polymorphism in some felid species strongly suggest that melanism is favored by natural selection in wild populations (Eizirik et al, 2003;Schneider et al, 2012;Silva, 2017). Although it has been proposed that melanistic coloration is adaptive under certain ecological conditions (Schneider et al, 2015;Silva, 2017), the functional advantages of melanism remain an enigma.…”

“…The multiple independent evolutionary origins of the melanistic mutation in Felidae (at least eight) and the high frequency of color polymorphism in some felid species strongly suggest that melanism is favored by natural selection in wild populations (Eizirik et al, 2003;Schneider et al, 2012;Silva, 2017). Although it has been proposed that melanistic coloration is adaptive under certain ecological conditions (Schneider et al, 2015;Silva, 2017), the functional advantages of melanism remain an enigma. The proposed functions of melanism include camouflage, thermoregulation, parasite resistance, and sexual selection (Graipel et al, 2019).…”

“…Both mechanisms of Gloger's rule predict a higher frequency of melanism in tropical forests compared with open grasslands or savannah. In addition, melanistic individuals may be selected against in open areas where they would be more conspicuous, and where dark coats would absorb more solar radiation and heat up faster (Delhey, 2017;Silva, 2017), leading to the prediction that melanistic individuals should occur less frequently in open habitats.…”