Disentangling the mechanisms of mate choice in a captive koala population

Abstract

Successful captive breeding programs are crucial to the long-term survival of many threatened species. However, pair incompatibility (breeding failure) limits sustainability of many captive populations. Understanding whether the drivers of this incompatibility are behavioral, genetic, or a combination of both, is crucial to improving breeding programs. We used 28 years of pairing data from the San Diego Zoo koala colony, plus genetic analyses using both major histocompatibility complex (MHC)-linked and non-MHC-linked microsatellite markers, to show that both genetic and non-genetic factors can influence mating success. Male age was reconfirmed to be a contributing factor to the likelihood of a koala pair copulating. This trend could also be related to a pair’s age difference, which was highly correlated with male age in our dataset. Familiarity was reconfirmed to increase the probability of a successful copulation. Our data provided evidence that females select mates based on MHC and genome-wide similarity. Male heterozygosity at MHC class II loci was associated with both pre- and post-copulatory female choice. Genome-wide similarity, and similarity at the MHC class II DAB locus, were also associated with female choice at the post-copulatory level. Finally, certain MHC-linked alleles were associated with either increased or decreased mating success. We predict that utilizing a variety of behavioral and MHC-dependent mate choice mechanisms improves female fitness through increased reproductive success. This study highlights the complexity of mate choice mechanisms in a species, and the importance of ascertaining mate choice mechanisms to improve the success of captive breeding programs.

Genetic diversity of the endangered Japanese golden eagle at neutral and functional loci

“…Moreover, assuming MHC similarity is correlated to relatedness, MHC-based mate choice may also act as an inbreeding avoidance mechanism (Potts et al, 1994;Potts & Wakeland, 1990). Consequently, assessment of MHC diversity has many applications for conservation, for example in understanding variation in pathogen susceptibility (e.g., whether certain populations are more susceptible to diseases than others) as well as the genetic underpinnings of reproductive success both in the wild and in captivity (Brandies et al, 2018;Hedrick, 2002;Hedrick et al, 2001;Siddle et al, 2007).…”

Deciphering genetic mate choice: Not so simple in group‐housed conservation breeding programs

“…In pairing trials, an animal is housed with a test individual of the opposite sex, with behavioral indicators and/or reproductive outcomes used to determine whether the pairing is preferred or nonpreferred (e.g., Hartnett, Parrott, Mulder, Coulson, & Magrath, 2018; Martin‐Wintle et al., 2015; Parrott, Nation, & Selwood, 2019). Other studies compare the breeding success of pairings with varying genetic characteristics (Brandies, Grueber, Ivy, Hogg, & Belov, 2018; Parrott, Ward, & Temple‐Smith, 2006; Parrott, Ward, Temple‐Smith, & Selwood, 2015; Russell et al., 2018). While experimental trials are useful, they are labor‐intensive and require resources that may not be available in many conservation breeding programs; for example, the space required to house animals in pairs.…”

Modelling Genetic Benefits and Financial Costs of Integrating Biobanking into the Captive Management of Koalas

“…Increase the quality of the reproductive output by ensuring surrogate females can give birth to young; • Overcome geographic separation and behavioral incompatibility of desirable breeding combinations and genetic pairings [62] which could also allow those koalas admitted to hospitals, zoos or captured from the wild during opportunistic research to contribute genetic material for the management of the broader wild population [60,61];…”