Abstract
Shifting of trophic niches of soil microarthropods may allow them to adapt to changing resource conditions as induced by global change processes. However, the capability of microarthropods to shift their trophic niches is little studied. Whereas some studies based on stable isotopes (15N/13C) point to distinct and narrow trophic niches, others indicate that trophic niches are plastic. Here, we investigated shifts in trophic niches of oribatid mites (Oribatida, Acari), a major soil detritivore microarthropod group, due to forest management, i.e., plantation of beech and spruce forests in Central Europe, using neutral lipid fatty acid (NLFA) markers. Due to differential microbial communities, we expected a fungi-based diet of oribatid mites in beech forest, but more bacterial contributions to the diet in spruce forest. Supporting these hypotheses, NLFA markers indicated that the trophic niches of each of the studied oribatid mite species differed between beech and spruce forests and shifted from feeding predominantly on litter and fungi in beech forest to more intensively feeding on bacteria in spruce forest. Oribatid mite species with the most pronounced differences in trophic niches included Achipteria coleoptrata, Eupelops hirtus, Eupelops plicatus and Liacarus xylariae, which had been classified as primary or secondary decomposers in previous studies. Overall, the results indicate that the ability of oribatid mite species to colonize different habitats and ecosystems is due to their ability to adjust their diet, i.e., to trophic plasticity. Changes in trophic niches in each of the studied oribatid mite species suggest that detritivores in soil may better cope with future changes in environmental conditions and associated changes in resource composition than species above the ground.
Highlights
Shifting of trophic niches allows animals to cope with fluctuating or changing resource conditions
For fatty acid (FA) analysis oribatid mite species from litter and soil were pooled as, based on results of stable isotope studies, trophic niches of oribatid mite species differ little between litter and soil (Scheu and Falca 2000)
Species with body size > 300 μm were used for the analyses. They included eight species that occurred in both forest types [Achipteria coleoptrata (11 samples from beech, 12 from spruce), Damaeus riparius (7, 6), Euzetes globulus (1, 3), Eupelops hirtus (6, 11), Eupelops plicatus (7, 3), Liacarus xylariae (2, 2), Nothrus palustris (4, 1) and Platynothrus peltifer (4, 5)], five which only occurred in beech forests [Hermannia gibba (2 samples), Phthiracaridae (7), Steganacarus magnus (8), Tritegeus bisulcatus (3), Xenillus tegeocranus (2)], and three that only occurred in spruce forests [Adoristes ovatus (3), Edwardzetes edwardzi (7), Liacarus coracinus (2); for details see Online Appendix 1]
Summary
Shifting of trophic niches allows animals to cope with fluctuating or changing resource conditions. Shifting trophic niches may allow species to cope with changing abiotic conditions as these may indirectly affect resource availability and accessibility (Carreira et al 2016). Trophic plasticity is an important trait allowing species to cope with global change processes such as increasing temperature or increasing frequency of extreme climatic events (Hoffmann and Sgrò 2011). Some animal species may evade changing resource conditions by moving to other habitats, but many species are limited by dispersal (Riibak et al 2015), or may be inferior competitors and not survive in new habitats (Hågvar et al 1990). The degree of trophic plasticity in animal taxa is likely to be a major determinant of their survival in a changing world
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