Stable isotope analysis suggests low trophic niche partitioning among co‐occurring land snail species in a floodplain forest

Abstract

Land snails are abundant invertebrates in many terrestrial ecosystems, playing an essential role in food webs and nutrient cycling. Although snails are commonly considered general grazers with a strong tendency to omnivory, their foraging strategy is well documented only for a few species. Virtually no data exist on trophic niche partitioning within snail assemblages. To fill this gap, we analyzed naturally occurring stable isotope (δ13C, δ15N), an approach widely applied in ecological research, but only rarely in terrestrial snail studies. We collected ten individuals of the dominant co‐occurring land snails (i.e., Aegopinella nitidula, Fruticicola fruticum, Oxyloma elegans, Succinea putris, Trochulus villosulus and Zonitoides nitidus) in a floodplain forest floor, along with their potential food sources and other invertebrates. All species, except for A. nitidula, showed high intraspecific variation in isotope signatures, indicating their opportunistic feeding behavior. Such a high intraspecific variation combined with the active movement range of all the species allows switching between food sources based on their accessibility. We observed that the trophic niches of the studied species highly overlapped, except for Z. nitidus. This suggests that trophic niche compartmentalization among co‐occurring species does not seem to be the mechanism to avoid competition for food. Virtually unlimited resources for snail food are assumed to explain the coexistence of many species in high‐density populations. Our results add to this concept of assembly rules in snail species by the finding of highly variable and overlapping trophic niches among the majority of the studied species.

Trophic niche size and overlap in temperate forest land snails are affected by their lifestyle and body size

“…In the present study, we found a high degree of overlap among isotopic niches of land snail species. This pattern has been documented previously and suggests that there is little or no trophic niche compartmentalisation between co-occurring land snail species (Schmidt et al, 2004;Bonkowski & Kappes, 2017;Němec et al, 2021). Consequently, the extent of food competition is generally considered negligible, as a virtually unlimited amount of food resources for snails can usually be expected.…”

“…It seems that differentiation in their microhabitat preferences is not driven to reduced interspecific competition among land snails, as it is generally negligible. Therefore, trophic niches are found to be highly overlapping as investigated using stable isotopes (Schmidt et al, 2004;Meyer & Yeung, 2011;Larson & Black, 2016;Bonkowski & Kappes, 2017;Němec et al, 2021), which is consistent with the finding of terrestrial communities showing high species overlap (Rossi et al, 2015). However, certain level of compartmentalisation has been documented for some gastropod species within an assemblage with respect to different trophic level (Meyer & Yeung, 2011), ontogenetic stage, utilisation of specific diet (Bonkowski & Kappes, 2017), or lifestyle (Saeki et al, 2017).…”

“…The obtained data file was extended by the published data of 60 individuals of six species (site D; table 1) adopted from Němec et al (2021). The sampling site represented floodplain forest situated in the Odra River alluvium (49.72208N, 18.11128E), Czech Republic.…”

The nature of dispersal barriers and their impact on regional species pool richness and turnover

“…These taxa represent an ideal system to analyse dispersal barriers because: (a) they have all undergone integrative taxonomic revision, occur throughout the entire region, and represent about 10% of the entire small‐sized Holarctic fauna. They are also among the most frequent land snails within the Holarctic fauna, and occur throughout the region across all habitat types and trophic states (Barker, 2001; Němec et al., 2021; Pilsbry, 1948; Sysoev & Schileyko, 2009; Welter‐Schultes, 2012); (b) post hoc analysis demonstrates that shell features allow for correct identification of all but one empirically validated taxon. It is thus possible to accurately determine occurrences from shells alone; (c) composition and abundance data are available for over 5000 modern sites across much of the Holarctic (Horsák & Meng, 2018; Horsáková et al., 2018; Nekola, 2014); (d) while being poor active movers (e.g.…”

An ecomorphic approach to assessing the biodiversity of soil macrofauna communities in urban parks

“…Часто зустрічається в антропогенних біотопах (Gural- Sverlova & Gural, 2012). Сапрофаг (Němec et al, 2021). Helix (Helix) albescens (Rossmassler, 1839) -поширений у причорноморських країнах.…”