A population genetic study of the eusocial naked mole-rat (Heterocephalus glaber)

The existence of eusocial species is perplexing from an evolutionary perspective because of the large proportion of a population's members that never or rarely have the opportunity to breed, but rather spend their lifetimes in their natal social group as helpers. This behavior has been thought to evolve as a result of kin selection in which genes of non-breeding helpers are indirectly passed on through the reproduction of the breeding relatives they help. The effectiveness of kin selection is dependent on the average within-group relatedness. We studied the eusocial naked mole-rat, Heterocephalus glaber, to better understand the role that average within-group relatedness may have in maintaining eusociality. This is an ideal study species because, (1) it is a diploid system and therefore, does not have the haplodiploid condition of hymenopterans that may have predisposed them to evolving eusociality and (2) it belongs to a socially diverse family that is well suited for comparative studies. To obtain a generalizeable estimate of average within-group relatedness, we had to take into account environmental and historical influences that could bias the estimate. For example, rivers were correlated to fragmentation patterns in the population structure and are thus likely to be dispersal barriers for this species. Mostly our estimates of average within colony relatedness values were not significantly different than the 0.5 level of relatedness expected for siblings from randomly mated parents, although values ranged with geographic scale and sample size. Moreover, they were often significantly lower than a previous estimate that had not similarly accounted for these sources of bias. Our analysis of F-statistics indicated this species has an avoidance of inbreeding system of mating, which contradicts previous notions of an inbreeding system. In addition to our population genetic study, we developed a program that runs in ESRI ArcGIS and can generate a surface of FST values using a moving window analysis. These F ST surface maps can be used to visualize genetic data to inform the grouping of populations according to more homogenous genetic units and provide a means of formulating hypotheses as to the likely causes of genetic discontinuities by overlaying geographical features.