Stable isotope composition (δ¹³ C and δ¹⁵ N values) of slime molds: placing bacterivorous soil protozoans in the food web context

Abstract

A comparison with reference groups of soil organisms suggests strong trophic links of slime molds to saprotrophic microorganisms which decompose plant litter, but not to humus-decomposing microorganisms or to mycorrhizal fungi. Under the assumption that slime molds are primarily feeding on bacteria, the isotopic similarity of slime molds and mycophagous soil animals indicates that saprotrophic soil bacteria and fungi are similar in bulk isotopic composition.

Uncovering trophic positions and food resources of soil animals using bulk natural stable isotope composition

“…More recent results suggest that this also applies to fungal hyphae in soil (Wallander et al ., ). There is evidence that the isotopic signature of saprotrophic soil bacteria resembles that of saprotrophic fungi (Tiunov et al ., ). Hence, soil animals feeding on mycorrhizal fungi ([4] in Fig.…”

“…To partly overcome the lack of experimental data, organisms with well‐known trophic ecology could be used as ‘reference trophic species’. For instance, certain species of earthworms or termites can be sampled and their stable isotope compositions used for assessing the trophic position of other species in the community (Kudrin, Tsurikov & Tiunov, ; Tiunov et al ., ). Further, Potapov & Tiunov () estimated fungivory of Collembola by comparing their δ 13 C and δ 15 N values with those of mycoheterotrophic plants known to be trophically linked to mycorrhizal or saprotrophic fungi.…”

“…To partly overcome the lack of experimental data, organisms with well-known trophic ecology could be used as 'reference trophic species'. For instance, certain species of earthworms or termites can be sampled and their stable isotope compositions used for assessing the trophic position of other species in the community (Kudrin, Tsurikov & Tiunov, 2015;Tiunov et al, 2015). Further, Fig.…”

Isotope analyses of amino acids in fungi and fungal feeding Diptera larvae allow differentiating ectomycorrhizal and saprotrophic fungi‐based food chains

“…However, it remains a riddle whether mycorrhizal fungi are consumed by soil animals in significant amounts. Comparisons of isotopic signatures of soil animals to those of other consumers of saprotrophic micro‐organisms, such as mycotrophic plants (Potapov & Tiunov, 2015) or fungus growing termites (Tiunov et al, 2015), suggest that fungal feeders primarily rely on saprotrophic fungi; however, this suggestion needs further verification as there also is evidence that few soil animal taxa are specialized ECM fungal feeders, for example, Protura (Bluhm et al., 2019). Potentially, 13 C fingerprinting may separate consumers of saprotrophic and mycorrhizal fungi, providing the opportunity to distinguish these feeding types.…”

Genetic barcoding of dark‐spored myxomycetes (Amoebozoa)—Identification, evaluation and application of a sequence similarity threshold for species differentiation in NGS studies

“…Together with fungi, unicellular protists constitute the most abundant soil eukaryotes (Ekelund & Rønn, ; Geisen, Tveit, et al., ). They play a key role in soil food webs as major predators of bacteria (Bonkowski, ; Rønn, Mccaig, Griffiths, & Prosser, ) and fungi (Geisen et al., ); influencing main ecosystem processes such as nutrient turnover and energy flow (Bonkowski, ; Briones, ; Tiunov et al., ). The advances in high‐throughput sequencing of marker genes (e.g., reviewed in Bálint et al., ) and the improvement of sequence databases for accurate taxon annotation (Nilsson et al., ) have enabled the exploration of the hidden world of microscopic organisms to an unprecedented level (Tedersoo et al., ; Urich et al., ; Valentini, Pompanon, & Taberlet, ).…”