Adult survival and microsatellite diversity in possums: effects of major histocompatibility complex-linked microsatellite diversity but not multilocus inbreeding estimators
- 238 Downloads
Adult survival is perhaps the fitness parameter most important to population growth in long-lived species. Intrinsic and extrinsic covariates of survival are therefore likely to be important drivers of population dynamics. We used long-term mark-recapture data to identify genetic, individual and environmental covariates of local survival in a natural population of mountain brushtail possums (Trichosurus cunninghami). Rainfall and intra-individual diversity at microsatellite DNA markers were associated with increased local survival of adults and juveniles. We contrasted the performance of several microsatellite heterozygosity measures, including internal relatedness (IR), homozygosity by loci (HL) and the mean multilocus estimate of the squared difference in microsatellite allele sizes within an individual (mean d 2). However, the strongest effect on survival was not associated with multilocus microsatellite diversity (which would indicate a genome-wide inbreeding effect), but a subset of two loci. This included a major histocompatibility complex (MHC)-linked marker and a putatively neutral microsatellite locus. For both loci, diversity measures incorporating allele size information had stronger associations with survival than measures based on heterozygosity, whether or not allele frequency information was included (such as IR). Increased survival was apparent among heterozygotes at the MHC-linked locus, but the benefits of heterozygosity to survival were reduced in heterozygotes with larger differences in allele size. The effect of heterozygosity on fitness-related traits was supported by data on endoparasites in a subset of the individuals studied in this population. There was no apparent density dependence in survival, nor an effect of sex, age or immigrant status. Our findings suggest that in the apparent absence of inbreeding, variation at specific loci can generate strong associations between fitness and diversity at linked markers.
KeywordsSurvival Mark-recapture Major histocompatibility complex Assignment test Parasite load
This work was supported by the Hermon Slade Foundation (grant 08-4), the Australian Research Council (project DP0984876) and the Commonwealth Environment Research Facility Applied Environmental Decision Analysis research hub. Thanks to Lachlan McBurney, Damian Michael, Chris Macgregor and Mason Crane for assistance in the field. The manuscript editor, Jörg Ganzhorn, and two anonymous referees provided constructive criticism of an earlier version of the manuscript.
- Burnham KP, Anderson DR (2003) Model selection and multi-model inference: a practical information-theoretic approach, 2nd edn. Springer, New YorkGoogle Scholar
- Goudet J (1995) FSTAT (Version 1.2): a computer program to calculate F-statistics. J Hered 86:485–486Google Scholar
- Heppell SS, Caswell H, Crowder LB (2000) Life histories and elasticity patterns: perturbation analyses for species with minimal demographic data. Ecology 65:4–665Google Scholar
- Lam MKP, Hickson RE, Cowan PE, Cooper DW (2000) A major histocompatibility (MHC) microsatellite locus in brushtail possums (Trichosurus vulpecula). J Vet Res 4:139–141Google Scholar
- Raymond M, Rousset F (1995) Genepop (version-1.2)—population-genetics software for exact tests and ecumenicism. J Hered 86:248–249Google Scholar
- Saether BE, Bakke O (2000) Avian life history variation and contribution of demographic rates to the population growth rate. Ecology 81:642–653Google Scholar
- Seebeck JH, Warneke RM, Baxter BJ (1984) Diet of the bobuck, Trichosurus caninus (Ogilby) (Marsupialia: Phalangeridae) in a mountain forest in Victoria. In: Smith AP, Hume ID (eds) Possums and gliders. Surrey Beatty, Sydney, pp 145–154Google Scholar
- Viggers KL (1996) Assessment of health, condition and the effects of parasites in the mountain brushtail possum. Ph.D. thesis, Australian National University, CanberraGoogle Scholar