A critically endangered estuarine limpet’s only two populations are genomically and morphologically distinct

Seagrass habitats are declining worldwide, placing several seagrass‐associated animals at risk of extinction. The Critically Endangered limpet Siphonaria compressa is one of the rarest molluscs in Africa, and has been reported from only two disjunctive lagoons in South Africa. Being a highly special...

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Bibliographic Details
Published in:	Aquatic conservation Vol. 33; no. 9; pp. 867 - 883
Main Authors:	Coito, Paula M., Emami‐Khoyi, Arsalan, Hedderson, Terry A., Toonen, Robert J., Teske, Peter R., Branch, George M.
Format:	Journal Article
Language:	English
Published:	Oxford Wiley Subscription Services, Inc 01-09-2023
Subjects:	Aquatic plants Biogeography Brackishwater environment Conservation Endangered species Estuaries Extinction Gene flow Genetic diversity Genetic variation Genomes Haplotypes isolation Lagoons limpet Marine molluscs Mitochondrial DNA Mollusks Morphology Nucleotide sequence Nucleotides Outbreeding Pleistocene Polymorphism Population genetics Populations rarity Restoration Sea grasses seagrass Shellfish Shells Single-nucleotide polymorphism speciation Species extinction Strategy Survival Temperature effects Thermal environments Translocation
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Summary:	Seagrass habitats are declining worldwide, placing several seagrass‐associated animals at risk of extinction. The Critically Endangered limpet Siphonaria compressa is one of the rarest molluscs in Africa, and has been reported from only two disjunctive lagoons in South Africa. Being a highly specialized grazer that lives exclusively on the narrow blades of Cape eelgrass, Zostera capensis, which is itself listed as Endangered in the South African Red List and has decreased in abundance, conservation initiatives are urgently needed to ensure the long‐term survival of S. compressa. Molecular data (sequence data from the mitochondrial genome and single nucleotide polymorphism data of the nuclear genome) and morphological data were analysed to determine whether the two populations are conspecific, with implications for whether translocation between localities could be a viable management strategy to restore either population in the event of a collapse, or to maintain the genetic diversity of each population. Strong evidence emerged for the distinctness of the two populations, including a lack of shared mtDNA haplotypes that indicate an absence of contemporary gene flow, a divergence time that dates to the late Pleistocene, and a number of morphological characters that distinguish their shells. These findings indicate that the two populations are distinct cryptic subspecies. As the two populations occur in different temperature‐defined marine biogeographical regions, they are probably adapted to different thermal environments. Translocations are not recommended, as this management strategy has considerable potential to result in outbreeding depression and exacerbate the extinction risk. Instead, each population should be managed separately, and several alternative conservation measures are discussed, including the protection and restoration of seagrass beds.
ISSN:	1052-7613 1099-0755
DOI:	10.1002/aqc.3993