Interspecific competition among terrestrial slugs

Abstract

Interspecific competition among terrestrial gastropods has previously been considered to have little effect on population dynamics and local distribution. Recent studies, however, demonstrate several cases in which interspecific competition plays a major role in structuring terrestrial gastropod communities. To explore the general importance of interspecific competition for the ecology of slugs, we conducted a semi-systematic literature review, synthesizing available peer-reviewed literature relating interspecific interactions to the following: (1) mortality and reproduction; (2) activity, movement, feeding and growth; and (3) habitat use and geographical distribution of slugs. To support the literature on slugs, we also reviewed literature on terrestrial snails. The body of available literature is relatively limited, but the effect of interspecific competition on survival, reproduction, movement and activity has clearly been demonstrated in laboratory experiments for different slug species. The occurrence of interspecific competition seems, however, to be species specific, and no negative effects due to the presence of heterospecifics have been reported for many of the species combinations investigated to date. Most of the studies demonstrating interspecific effects between slug species involved interference from a few aggressive species (mainly Limax maximus as the aggressor). In addition, several correlative studies have indicated that in terrestrial gastropods, habitat use and geographical distribution might be mediated by interspecific competition. Further, well-designed experiments are needed to explore the general importance of interspecific competition among slugs, potentially with a focus on interactions between invasive and native species, where the lack of a shared evolutionary history and niche separation may increase the intensity of competition. Such experimental studies may produce information that has implications for the conservation of native species, as well as for management of invasive pests, because interspecific competition may result in local extinction of vulnerable species and influence the possibility of non-native species establishing invasive populations in new areas.

Dispersal movements of non‐native and native terrestrial slugs in an urban environment

“…From a pest ecology perspective, crawling activity and movement rates might relate both to slug dispersal but also to potential competitive interactions (Watz & Nyqvist, 2022). Although there is little evidence for interspecific competition in the wild among terrestrial slugs, the effects of interspecific competition on survival, reproduction, movement, and activity have been demonstrated in laboratory experiments for different slug species, mainly in the form of interference competition through aggressive interactions or reactions to mucus trails (O'Hanlon et al, 2020; Rollo, 1983a; Watz & Nyqvist, 2022). The outcome of the interspecific interaction, however, is species specific, with several studies showing no competitive effects (Watz & Nyqvist, 2022).…”

“…Although there is little evidence for interspecific competition in the wild among terrestrial slugs, the effects of interspecific competition on survival, reproduction, movement, and activity have been demonstrated in laboratory experiments for different slug species, mainly in the form of interference competition through aggressive interactions or reactions to mucus trails (O'Hanlon et al, 2020; Rollo, 1983a; Watz & Nyqvist, 2022). The outcome of the interspecific interaction, however, is species specific, with several studies showing no competitive effects (Watz & Nyqvist, 2022). For example, in enclosure experiments, individuals of L. maximum (a slug that is considered particularly aggressive), L. maximum displaced individuals of A. ater and Ariolimax columbianus , whereas no such effect was seen among the other species (Rollo, 1983b; Rollo & Wellington, 1979).…”

Dietary Niche Partitioning Among Sympatric Terrestrial Gastropods in a Temperate Woodland

“…However, with such morphological similarity among species, organisms must nd ways to limit direct competition (Scriven et al 2016). Evidence of the mechanisms behind interspeci c competition and its in uence in structuring gastropod communities remains elusive, particularly with respect to niche partitioning (see Watz and Nyqvist, 2022).…”

Egg production in Arion vulgaris: density dependence in A. vulgaris and interspecific effects of Limax maximus

“…petition may mediate niche segregation, habitat exclusion or local extinction ( Watz & Nyqvist, 2022 ). In terrestrial slugs, exploitation competition is probably rare, whereas there are several examples of interference competition, both direct via aggressive behaviour ( Wellington & Rollo, 1979 ;Cook, 1981 ;Rollo, 1983 ) and indirect via mucus trails ( O'Hanlon et al ., 2020 ).…”

“…Egg production in terms of the number of eggs and clutches, as well as egg size and timing, is under endocrine control ( South, 1992 ). Individual slugs seem to be able to adjust these reproductive features to both biotic factors, such as competition ( Rollo, 1983 ;Watz & Nyqvist, 2022 ), and the physical environment ( South, 1992 ). Our study design did not allow us to identify the mechanism behind the negative effect.…”