Small populations of endangered species risk losing already eroded genetic diversity, important for adaptive potential, through the effects of genetic drift. The magnitude of drift can be mitigated by maximising the effective population size, as is the goal of genetic management strategies. Different mating systems, specifically those leading to reproductive skew, exacerbate genetic drift by distorting contributions. In the absence of an active management strategy, reproductive skew will have long-term effects on the genetic composition of a population, particularly where admixture is present. Here we examine the contrasting effects of conservation management strategies in two ex situ populations of the Critically Endangered eastern black rhino (Diceros bicornis michaeli), one managed as a semi-wild population in South Africa (SAx), and one managed under a mean-kinship breeding strategy in European zoos. We use molecular data to reconstruct pedigrees for both populations and validate the method using the zoo studbook. Using the reconstructed pedigree and studbook we show there is male sex-specific skew in both populations. However, the zoo’s mean-kinship breeding strategy effectively reduces reproductive skew in comparison to a semi-wild population with little genetic management. We also show that strong male reproductive skew in SAx has resulted in extensive admixture, which may require a re-evaluation of the population’s original intended role in the black rhino meta-population. With a high potential for admixture in many ex situ populations of endangered species, molecular and pedigree data remain vital tools for populations needing to balance drift and selection.

Susanne Shultz

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Linking environmental conditions to the modulators of individual fitness is necessary to predict long-term population viability and resilience. Behavioural and physiological biomarkers can provide this mechanistic insight into how individuals perceive and respond to environmental challenges through primary physiological responses, secondary downstream responses and tertiary whole organism responses. To fully exploit biomarkers, we need to move beyond single biomarker studies to develop an integrative approach that models the interactions between extrinsic challenges, physiological and behavioural pathways and their modulators. Here we introduce two frameworks for using multiple integrated biomarkers to establish changes in functional condition. The Functional Marginality Hypotheses proposes that relative changes in allostatic load, reproductive health and behaviour can evidence and establish causation driving macroecological processes such as local extirpation, colonisation, population dynamics and range change. The Functional Recovery Hypothesis proposes that a similar approach can serve as a valuable conservation tool for evaluating individual and population level health, predicting responses to future environmental change and measuring the impact of interventions. We highlight specific studies that have used complementary biomarkers to link extrinsic challenges to population performance. This framework of integrated biomarkers has untapped potential to identify causes of decline, predict future changes and mitigate against future biodiversity loss.