Adult survival and microsatellite diversity in possums: effects of major histocompatibility complex-linked microsatellite diversity but not multilocus inbreeding estimators

Abstract

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.

Viability selection creates negative heterozygosity–fitness correlations in female Black Grouse Lyrurus tetrix

“…In addition to body mass, heterozygosity also positively influenced the survival of female Black Grouse. This is similar to the findings of many other studies where genome-wide heterozygosity and heterozygosity at specific loci have been associated with increased survival in some vertebrate species [mammals (Banks et al 2010;Forcada and Hoffman 2014); fish (Evans et al 2010); birds (Worley et al 2010;Cézilly et al 2016)]. Similar to body size, the relationship between survival and heterozygosity has been mainly found in juveniles (e.g.…”

Genetic diversity at neutral and adaptive loci determines individual fitness in a long-lived territorial bird

“…Although some studies point out intermediate rather than maximal levels of MHC diversity to be more advantageous [53,54], the observed relationship with MHC diversity in this study is in line with recent findings suggesting that higher MHC heterozygosity enhances fitness, either through survival or reproductive performance. For example, Banks et al [55] described a positive correlation between heterozygosity at MHC-linked markers and survival in a long-lived mammal species (the mountain brushtail possum Trichosurus cunninghami). In males of fat-tailed dwarf lemur (Cheirogaleus medius) and grey mouse lemur (Microcebus murinus), MHC individual allelic diversity was associated with increased reproductive success [56].…”

Kin selection in den sharing develops under limited availability of tree hollows for a forest marsupial

“…12 years, reproducing after 2 -3 years) marsupial of southeast Australian forests [29,30]. It is primarily a nocturnal generalist herbivore and uses hollows in living or dead standing trees for day-time shelter [31].…”