Reproduction and growth of the endangered siphonariid limpet<i>Siphonaria compressa</i>(Pulmonata: Basommatophora)

Allanson, B. R.; Msizi, S. C.

doi:10.1080/07924259.2010.9652327

Cited by 9 publications

(16 citation statements)

References 20 publications

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“…Only a single ratio (apex height to shell height) failed to be significantly different. The smaller shell sizes of specimens from Knysna are corroborated by shell‐length measurements recorded there by Allanson & Herbert (2005; median 1.75 mm, range 0.5–4.5 mm), and by Allanson & Msizi (2010; median 0.89, range 0.5–3.0 mm). As populations at both localities occupy identical habitats, eelgrass in the intertidal zone, the morphological differences that have emerged between the two geographical areas are unlikely to be phenotypic responses to habitat differences.…”

Section: Discussionsupporting

confidence: 70%

“…With a recorded sea‐level rise of 2.19 mm per year, 40% of the intertidal saltmarshes of Knysna Lagoon will be lost by 2100 because development around the periphery of the estuary will prevent saltmarsh migration to higher levels (Raw et al, 2020). The estuary is additionally vulnerable to periodic flooding of the Knysna River (Allanson & Msizi, 2010), reducing salinities to levels that decimate S. compressa . Tourist foot traffic and recreational water activities cause both physical disturbance and degradation of the eelgrass beds, and suspend additional particulate matter in the relatively shallow water, which settles on the surfaces of the eelgrass, hampering both attachment and grazing by the limpet.…”

Section: Discussionmentioning

confidence: 99%

“…It has been experimentally established that the individuals of the Knysna population rapidly reach maturity and lay egg capsules at a high frequency, with a very short period between egg capsule deposition and recruitment. In fact, the short time for reproductive length to be reached (between 120 and 170 days) may be a selective advantage enabling rapid regeneration in an unstable environment (Allanson & Msizi, 2010; Allanson & Fearon, 2013). Indeed, it is a feature of the mollusc in both Knysna and Langebaan (Angel et al, 2006) that it has the ability to recover rapidly from very low densities.…”

Section: Discussionmentioning

confidence: 99%

“…As the genome‐wide mutation rate for the study species is unknown and no reliable published data for molluscs exist, the invertebrate mutation rate of 2.8 × 10 −9 per site per generation based on the spontaneous genome‐wide mutation rate of Drosophila melanogaster (Keightley et al, 2014) was employed as an approximation of the mean mutation rate across the S. compressa genome. The diffusion time scale was converted to time in years using a generation time of 150 days (Allanson & Msizi, 2010; Allanson & Fearon, 2013).…”

Section: Methodsmentioning

confidence: 99%

“…The limpet Siphonaria compressa Allanson, 1958, which lives exclusively on Cape eelgrass, Zostera capensis, is South Africa's most threatened marine mollusc (Herbert, 1999) and is listed by the IUCN as 'Critically Endangered' (Kilburn, 1996). For years, this species was known only from a single population in Langebaan Lagoon (Figure 1) on the cool-temperate west coast of South Africa (Herbert, 1998;Herbert, 1999), where drastic fluctuations in population size have been reported (Angel et al, 2006), and a substantial loss of seagrass in Langebaan Lagoon has been associated with declines in invertebrate abundance and species richness (Pillay et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

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

de Coito,

Emami‐Khoyi,

Hedderson

et al. 2023

Aquatic Conservation

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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.

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Section: Discussionsupporting

confidence: 70%

Section: Discussionmentioning

confidence: 99%