Conservation priorities in an endangered estuarine seahorse are informed by demographic history

Thomas Kalama Mkare,Bettine Jansen Van Vuuren,Peter R Teske

doi:10.1038/s41598-021-83754-4

Thomas Kalama Mkare, Bettine Jansen Van Vuuren + Show 1 more

Open Access

https://doi.org/10.1038/s41598-021-83754-4

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Abstract

Historical demographic events shape genetic diversity that remains evident in the genomes of contemporary populations. In the case of species that are of conservation concern, this information helps to unravel evolutionary histories that can be critical in guiding conservation efforts. The Knysna seahorse, Hippocampus capensis, is the world’s most endangered seahorse species, and it presently survives in only three estuaries on the South African south coast. Factors that contributed to the species becoming endangered are unclear; additionally, the lack of information on whether the three populations should be managed separately because of potential long-term isolation hampers effective management efforts. In the present study, we reconstructed the seahorses’ demographic history using a suite of microsatellite loci. We found that the largest population (Knysna Estuary) has colonised the other estuaries relatively recently (< 450 years ago), and that its population size is comparatively large and stable. Neither of the other two populations shows signs of long-term reductions in population size. The high conservation status of the species is thus a result of its limited range rather than historical population declines. Our findings indicate that the long-term survival of H. capensis depends primarily on the successful management of the Knysna population, although the other estuaries may serve as reservoirs of genetic diversity.

Highlights

Historical demographic events shape genetic diversity that remains evident in the genomes of contemporary populations
It was believed that the absence of impermeable dispersal barriers in most marine systems would automatically result in genetic homogeneity[12]
The question whether translocation should be considered as a conservation tool in the management plan of the endangered Knysna seahorse has remained controversial ever since the first genetic study on this species was conducted[29]

Summary

Introduction

Historical demographic events shape genetic diversity that remains evident in the genomes of contemporary populations. Our findings indicate that the long-term survival of H. capensis depends primarily on the successful management of the Knysna population, the other estuaries may serve as reservoirs of genetic diversity Demographic events, both historical and more recent, leave long-lasting and tractable footprints in the genomes of natural populations[1]. When faced with severe population decline in low dispersal species, populations are often allowed to become extinct instead of facilitating the mixing of individuals from populations with unique genetic identities[24] This reluctance stems from the fact that the mixing of populations with supposedly long histories of isolation may result in outbreeding depression and the loss of unique a daptations[22]. There is a potential risk of introducing parasites or disease-causing vectors into the recipient population[25]

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