Abstract
Abstract. Overexploitation, habitat destruction and a changing climate threaten populations of the Roman snail (Helix pomatia Linnaeus, 1758), which has led to a high protection status in Germany. Vertebrate and invertebrate predators, including parasites and facultative parasitoids, further cause pressure on populations. Given the conservation concern for H. pomatia and its rarity in the study region (Cottbus, Germany), we studied how predators and facultative parasitoids utilize H. pomatia shells with a focus on non-invasive field methods. As previous studies indicated that shell size may affect prey selection by predators, morphometric traits were measured in eight subpopulations. We identified the total number and percentage of H. pomatia shells that showed external attack marks by predators and internal utilization marks by Diptera pupae and related those utilization patterns to the morphometric traits of shells. A large proportion of the shells in local subpopulations showed signs of external attack and internal utilization, and both utilization forms were positively correlated. External attacks by predators were more frequent in larger shells and internal utilization by Diptera was more common in shells with higher body density. These results suggest a considerable pressure by predators and potential facultative parasitoids on H. pomatia populations in the study area. Future research should focus on the relationship between snails from the family Helicidae and flies from the genus Discomyza. Conservation programmes should consider abiotic habitat conditions together with potential trophic interactions to maximize the success of conservation strategies.
Highlights
The Roman snail (Helix pomatia Linnaeus, 1758) is of considerable commercial interest as human food and in medical research (Dwek et al, 2001)
Out of 642 shells of H. pomatia analysed for external attack marks, 207 (32 %) showed signs of external attacks (Table 1)
Larger shells were more prone to external attack, and a higher body density resulted in more frequent internal utilization by Diptera
Summary
The Roman snail (Helix pomatia Linnaeus, 1758) is of considerable commercial interest as human food ( called “edible snail”; Bloszyk et al, 2010; Gheoca, 2013) and in medical research (Dwek et al, 2001). Habitat destruction (Andreev, 2006) and a changing climate (Nicolai and Ansart, 2017) may threaten H. pomatia populations in the future as well, in areas with unfavourable soil conditions. Those conservation concerns resulted in the development of breeding programmes to protect the species (Hardouin, 1995; Ligaszewski et al, 2014). National regulations protect H. pomatia in Germany (Bundesartenschutzverordnung (BArtSchV) Paragraph 1 Satz 1) and control the collection of snails, but they do not implement specific conservation programmes. A citizen science project coordinated by the Nature and Biodiversity Conservation Union focuses
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