High consistency of trophic niches in generalist arthropod species (Oribatida, Acari) across soil depth and forest type

Abstract

Many traits including trophic niche parameters are attributed to species. However, generalist species may vary in trophic niches with environments, making species‐based knowledge hard to extrapolate beyond local food webs. Here we tested trophic consistency in oribatid mite species (Acari), one of the most abundant arthropods that occupy all trophic levels in soil food webs. We used stable isotope analysis to compare trophic niches of 40 Oribatida species that co‐occur in litter (O L ) and soil (0–5 cm, mainly O F/H , A H ) of five forest types (native European beech, non‐native Douglas fir, range‐expanding Norway spruce, two beech–conifer mixed forests). Although stable isotope signatures of bulk material differed between litter and soil, 13 C and 15 N values of Oribatida species were remarkably stable irrespective of soil depth. Furthermore, Oribatida were more enriched in 13 C in European beech than in coniferous forests, but forest type little affected 15 N values of Oribatida across a range of site conditions. We conclude that Oribatida species occupy virtually identical trophic niches (δ 13 C and δ 15 N values) irrespective of the soil depth they colonize and that forest management including non‐native tree species little affects trophic position (δ 15 N values) of oribatid mites. Our findings suggest that the trophic position can be used as a trait in community analysis of Oribatida across forest ecosystems. Our results further indicate that trophic niches of generalist species can be highly consistent irrespective of environment.

Opening up new niche dimensions: The stoichiometry of soil microarthropods in European beech and Norway spruce forests

“…On the other hand, it may also indicate that these taxa only allow very limited variations in element ratios supporting the idea of stoichiometric homeostasis (Andrieux et al, 2020; Persson et al, 2010; Sterner & Elser, 2002) and the view that, concerning trophic niches, soil animals have limited ability to respond to changing environmental conditions (Gan et al, 2014; Jochum et al, 2017). The latter is consistent with the rather constant trophic and stoichiometric niche of soil animals across forest ecosystems and soil depths (Lu et al, 2022; Scheu & Falca, 2000; Schneider et al, 2004; Zhang, Chen, Deng, Li, Chen, et al, 2022; Zhang, Chen, Deng, Li, González, & Wang, 2022).…”

“…Further, neutral lipid fatty acid analysis is increasingly used for investigating the trophic niche of soil animal species (Maraun et al, 2020 ; Ruess et al, 2007 ; Ruess & Chamberlain, 2010 ). The results suggest that trophic niches of soil arthropods are rather independent of the forest type they inhabit and also of the litter horizon they are living in (Lu et al, 2022 ; Scheu & Falca, 2000 ; Schneider et al, 2004 ). However, being based on two dimensions only, stable isotope analysis only displays a fraction of the niche dimensions of animal species.…”

Tree species identity, canopy structure and prey availability differentially affect canopy spider diversity and trophic composition

“…For detailed description of spider and leaf sample (baseline) preparation and the stable isotope analysis pipeline see Appendix S1. To compensate for variation in the isotopic baseline between plots, we calibrated all spider isotopic ratios with mean δ values of leaves from the respective plot (Lu et al 2022 ). Calibrated ratios henceforth are denoted as Δ 13 C and Δ 15 N.…”

Niche dimensions in soil oribatid mite community assembly under native and introduced tree species

“…Litter quality may therefore only be important for certain species (e.g., endophagous taxa such as Phthiracarus spp. or Microtritia minima ), whereas other species, such as those at high trophic positions (e.g., Oppiidae, Suctobelbidae and Quadroppiidae) may suffer from reduced root‐derived resources in Douglas fir stands (Lu, 2021 ; Lu, Cordes, et al., 2022 ). As the patterns of trait dissimilarity were similar for the monoculture/mixed forest fixed factor model and the beech presence model, the strong filtering effect in mixed forests was likely due to the effect of beech and not mixed forests in general.…”