Environmental and Genetic Considerations for the Conservation of an Arboreal Species: Phascolarctos cinereus
Many factors have been shown to affect mating behavior (e.g. day length, age, genotype). For instance, genes of the major histocompatibility complex (MHC) are known to influence mate choice in a wide variety of vertebrate species. The genetic management of captive populations can be confounded if intrinsic mate choice reduces or eliminates reproductive success between carefully chosen breeding pairs. For example, the San Diego Zoo (SDZ) koala colony only has a 45\% copulation rate for matched individuals. In order investigate if MHC had an effect on mating success in this population, we first had to characterize it in the koala, which we did via a transcriptome study of immunologically important tissues (blood and spleen). Using phylogenetic analyses, we identified 22 koala genes including toll-like receptors (TLRs), RIG-I like receptors (RLRs), major histocompatibility complex (MHC) genes, and koala retrovirus (KoRV). The full-length sequences we generated can serve as targets for future investigations that aim to conserve koala populations. We then investigated various determinants of SDZ koala mating success using breeding records (1984-2010): age, day length, and average pairwise kinship, and MHC genotypes (52 individuals and four MHC markers). We quantified MHC diversity according to functional amino acids, heterozygosity, and the probability of producing a heterozygous offspring then used categorical analysis and logistic regression to investigate both copulation and parturition success. Day length and dam age consistently had an effect on mating success, however MHC did not. These findings may be leveraged to improve the success of attempted pairs, conserve resources, and facilitate genetic management.
DeWoody, Purdue University.
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