Revealing life-history traits by contrasting genetic estimations with predictions of effective population size

Abstract

Effective population size, a central concept in conservation biology, is now routinely estimated from genetic surveys, and can also be theoretically-predicted from demographic, life-history and mating-system hypotheses. However, by evaluating the consistency of theoretical predictions with empirically-estimated effective size, insights can be gained regarding life-history characteristics, as well as the relative impact of different life-history traits on genetic drift. These insights can be used to design and inform management strategies aimed at increasing effective population size. Here we describe and demonstrate this approach by addressing the conservation of a reintroduced population of Asiatic wild ass (Equus hemionus). We estimate the variance effective size (Nev) from genetic data (Nev = 24.3 ), and we formulate predictions for the impacts on of demography, polygyny, female variance in life-time reproductive success, and heritability of female reproductive success. By contrasting the genetic estimation with theoretical predictions, we find that polygyny is the strongest factor effecting genetic drift, as only when accounting for polygyny were predictions consistent with the genetically-measured , with 10.6% mating males per generation when heritability of female RS was unaccounted for (polygyny responsible for 81% decrease in ), and 19.5% when it was accounted for (polygyny responsible for 67% decrease in ). Heritability of female reproductive success was also found to affect , with h2 = 0.91 (heritability responsible for 41% decrease in ). The low effective population size is of concern, and we suggest specific management actions focusing on factors identified as strongly affecting —increasing the availability of artificial water sources to increase number of dominant males contributing to the gene pool. This approach – evaluating life-history hypotheses, in light of their impact on effective population size, and contrasting predictions with genetic measurements – is a general, applicable strategy that can be used to inform conservation practice.