Effects of Inbreeding on Endangered Red Wolves (Canis rufus)

Abstract

Inbreeding depression, the reduction in offspring fitness caused by mating among close relatives, is widespread in small populations and a major concern in conservation biology because it can affect population persistence. The negative effects of inbreeding results in the evolution of inbreeding avoidance behaviors; within small populations, such behaviors may encourage individuals to select mates outside of their respective species. Mate choice may also be facilitated by variation at major histocompatibility complex (MHC) genes, a gene group critical for immune response and disease resistance. Given broad impacts of inbreeding and MHC variation on fitness and behavior, evaluating their effects is an important component of wildlife management. My dissertation research examined how inbreeding and immunogenetic variation influenced fitness, disease susceptibility, and mating behavior in endangered wild red wolves (Canis rufus). I also evaluated mitochondrial DNA from ancient canid bones to inform an ongoing debate regarding the species status of red wolves. I found evidence for an ancient red wolf origin which supports contemporary red wolf management practices (Chapter 2). Although these analyses were not directly related to inbreeding, clarifying red wolf taxonomic status is vital for effective species conservation. With regard to inbreeding depression, I found that red wolves were extremely inbred but their fitness was not associated with inbreeding. However, more inbred wolves tended to be smaller, which may have an indirect effect on reproductive success (Chapter 3). Next, I evaluated how immunogenetic variation influenced disease susceptibility by collecting baseline disease prevalence in red wolves and sympatric coyotes (Canis latrans), and sequencing MHC and toll-like receptor (TLR) genes. Coyotes harbored more parasite species then wolves and may act as disease reservoirs for red wolves (Chapter 4). Red wolves had lower immune gene variation then coyotes; variation may have been maintained through positive selection at MHC genes (Chapter 5). There were also several TLR haplotypes which were correlated with disease susceptibility. Finally, I evaluated red wolves’ mate choice (Chapter 6). I found little evidence for pedigree kinship avoidance but red wolves may avoid mates with more similar MHC alleles. This could contribute to hybridization with coyotes to avoid MHC-similar mates.