Abstract
Alien gastropods have caused extensive harm to biodiversity and socioeconomic systems like agriculture and horticulture worldwide. For conservation and management purposes, information on impacts needs to be easily interpretable and comparable, and the factors that determine impacts understood. This study aimed to assess gastropods alien to South Africa to compare impact severity between species and understand how they vary between habitats and mechanisms. Furthermore, we explore the relationship between environmental and socioeconomic impacts, and both impact measures with life‐history traits. We used the Environmental Impact Classification for Alien Taxa (EICAT) and Socio‐Economic Impact Classification for Alien Taxa (SEICAT) to assess impacts of 34 gastropods alien to South Africa including evidence of impact from their entire alien range. We tested for correlations between environmental and socioeconomic impacts per species, and with fecundity and native latitude range using Kendall's tau tests. Kruskal–Wallis tests were used to compare impact magnitude among mechanisms and habitats, respectively. This study presents the first application of EICAT and SEICAT for invertebrates. There was no correlation between environmental impacts and socioeconomic impacts. Habitats did not differ regarding the severity of impacts recorded, but impacts via disease transmission were lower than other mechanisms. Neither fecundity nor native range latitude was correlated with impact magnitude. Despite gastropods being agricultural and horticultural pests globally, resilience of socioeconomic systems makes high impacts uncommon. Environmental systems may be vulnerable to gastropod impacts across habitats, having experienced multiple local extinctions of wetland island snail fauna. South Africa stands out as the only continental country that follows this trend. The knowledge gained on severity and nature of gastropod impacts is useful in risk assessment, which can aid conservation management. To make impact assessments more realistic, we suggest alternative ways of reporting impacts classified under EICAT and SEICAT.
Highlights
Alien species introductions continue to be a major driver of global change (Banks, Paini, Bayliss, & Hodda, 2015; Hulme, 2015)
A filter was applied to Scopus, which included the following fields: “Agricultural and Biological Sciences,” “Medicine, Immunology and Microbiology,” “Environmental Science,” “Veterinary, Pharmacology, Toxicology and Pharmaceutics” and “Multidisciplinary.” Titles and abstracts were screened regarding their relevance for gastropod impacts, and the search considered complete when the literature begun to repeat itself, no further information on impact was found, or the search engine ran out of results
This study has successfully categorized the global impacts of South African alien gastropods into Environmental Impact Classification for Alien Taxa (EICAT) and Socio-Economic Impact Classification for Alien Taxa (SEICAT), adding a novel taxonomic group to a growing list of universally comparable alien impact assessments (Bacher et al, 2017; Evans et al, 2016; Kumschick et al, 2017)
Summary
Alien species introductions continue to be a major driver of global change (Banks, Paini, Bayliss, & Hodda, 2015; Hulme, 2015). Many gastropods have been the cause of significant problems in agriculture (Barker, 2002; Coupland & Baker, 1995; Nash & Hoffmann, 2012), resulting in economic losses by reducing yield and leading to rejection of exports (Charwat, Davies, & Fraser, 1995; Cowie, Hayes, Tran, & Meyer, 2008; Moran, Gotlib, & Yaakov, 2004). They have been implicated as playing a role in the transmission of diseases to humans (Senanayake, Pryor, Walker, & Konecny, 2003)
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