Heterozygosity is low where rare color variants in wild carnivores prevail

Abstract

Coat color and pattern are a distinguished feature in mammalian carnivores, shaped by climatic cycles and habitat type. It can be expressed in various ways, such as gradients, polymorphisms, and rare color variants. Although natural selection explains much of the phenotypic variation found in the wild, genetic drift and heterozygote deficiency, as prominent in small and fragmented populations, may also affect phenotypic variability through the fixation of recessive alleles. The aim of this study was to test whether rare color variants in the wild could relate to a deficiency of heterozygotes, resulting from habitat fragmentation and small population size. We present an overview of all rare color variants in the order Carnivora, and compiled demographic and genetic data of the populations where they did and did not occur, to test for significant correlations. We also tested how phylogeny and body weight influenced the presence of color variants with phylogenetic generalized linear mixed models (PGLMMs). We found 40 color‐variable species and 59 rare color variants. In 17 variable phenotypic populations for which genetic diversity was available, the average AR was 4.18, HO = 0.59, and HE = 0.66, and FIS = 0.086. We found that variable populations displayed a significant reduction in heterozygosity and allelic richness compared to non‐variable populations across species. We also found a significant negative correlation between population size and inbreeding coefficients. Therefore, it is possible that small effective size had phenotypic consequences on the extant populations. The high frequency of the rare color variants (averaging 20%) also implies that genetic drift is locally overruling natural selection in small effective populations. As such, rare color variants could be added to the list of phenotypic consequences of inbreeding in the wild.

New record of strawberry leopard (Panthera pardus) in Selous Game Reserve, Tanzania

“…It is possible that the strawberry colouration offers a selective benefit for leopards in the landscape, like the potential higher hunting success of white morphs of the black bear (Ursus americanus kermodei; Klinka & Reimchen, 2009) and possible advantage of the servaline serval's smaller spots in forested areas (Leptailurus serval; Bantlin & Evers, 2023). However, if this were the case, we would expect the morph to be more common within the Selous leopard population than observed (Tensen & Fischer, 2024). Alternatively, the strawberry phenotype could have arisen in Selous as a result of heterozygote deficiency due to inbreeding (Tensen & Fischer, 2024), as the leopard population is subject to trophy hunting .…”

“…The presence of a strawberry leopard in Selous could be the result of a stepping‐stone dispersal from northern South Africa. However, 2000 km is a considerable distance – male leopards in a South African population were found to disperse 11 km on average (Fattebert et al., 2015 ), although one dispersal event of 350 km has been recorded (Fattebert et al., 2013 ) – particularly as the phenotype is thought to occur in South Africa as a result of males dispersing shorter than usual distances (Tensen et al., 2022 ; Tensen & Fischer, 2024 ). Dispersers would also have had to successfully navigate through extensive areas of non‐habitat, as well as major rivers (particularly the Zambezi and Ruvuma Rivers).…”

“…Alternatively, the strawberry phenotype could have arisen in Selous as a result of heterozygote deficiency due to inbreeding (Tensen & Fischer, 2024 ), as the leopard population is subject to trophy hunting (Searle, Strampelli, Parsais, et al., 2023 ). This is the mechanism believed to be behind the phenotype's proliferation in northern South Africa, where a high offtake of adult males has meant that young males do not need to disperse far from their mothers, which increases inbreeding and thus the chance of rare recessive alleles being expressed (Pirie et al., 2016 ; Tensen et al., 2022 ).…”