23 research outputs found
Changes in Plant Species Richness Induce Functional Shifts in Soil Nematode Communities in Experimental Grassland
Changes in plant diversity may induce distinct changes in soil food web structure and accompanying soil feedbacks to plants. However, knowledge of the long-term consequences of plant community simplification for soil animal food webs and functioning is scarce. Nematodes, the most abundant and diverse soil Metazoa, represent the complexity of soil food webs as they comprise all major trophic groups and allow calculation of a number of functional indices.We studied the functional composition of nematode communities three and five years after establishment of a grassland plant diversity experiment (Jena Experiment). In response to plant community simplification common nematode species disappeared and pronounced functional shifts in community structure occurred. The relevance of the fungal energy channel was higher in spring 2007 than in autumn 2005, particularly in species-rich plant assemblages. This resulted in a significant positive relationship between plant species richness and the ratio of fungal-to-bacterial feeders. Moreover, the density of predators increased significantly with plant diversity after five years, pointing to increased soil food web complexity in species-rich plant assemblages. Remarkably, in complex plant communities the nematode community shifted in favour of microbivores and predators, thereby reducing the relative abundance of plant feeders after five years.The results suggest that species-poor plant assemblages may suffer from nematode communities detrimental to plants, whereas species-rich plant assemblages support a higher proportion of microbivorous nematodes stimulating nutrient cycling and hence plant performance; i.e. effects of nematodes on plants may switch from negative to positive. Overall, food web complexity is likely to decrease in response to plant community simplification and results of this study suggest that this results mainly from the loss of common species which likely alter plant-nematode interactions
Patterns and dynamics of neutral lipid fatty acids in ants – implications for ecological studies
Patterns and dynamics of neutral lipid fatty acids in ants – implications for ecological studies
Background: Trophic interactions are a fundamental aspect of ecosystem functioning, but often difficult to observe
directly. Several indirect techniques, such as fatty acid analysis, were developed to assess these interactions. Fatty
acid profiles may indicate dietary differences, while individual fatty acids can be used as biomarkers. Ants
are among the most important terrestrial animal groups, but little is known about their lipid metabolism,
and no study so far used fatty acids to study their trophic ecology. We set up a feeding experiment with
high- and low-fat food to elucidate patterns and dynamics of neutral lipid fatty acids (NLFAs) assimilation
in ants. We asked whether dietary fatty acids are assimilated through direct trophic transfer, how diet
influences NLFA total amounts and patterns over time, and whether these assimilation processes are similar
across species and life stages.
Results: Ants fed with high-fat food quickly accumulated specific dietary fatty acids (C18:2n6, C18:3n3 and
C18:3n6), compared to ants fed with low-fat food. Dietary fat content did not affect total body fat of workers or amounts
of fatty acids extensively biosynthesized by animals (C16:0, C18:0, C18:1n9). Larval development had a strong effect on the
composition and amounts of C16:0, C18:0 and C18:1n9. NLFA compositions reflected dietary differences, which became
more pronounced over time. Assimilation of specific dietary NLFAs was similar regardless of species or life stage, but
these factors affected dynamics of other NLFAs, composition and total fat.
Conclusions: We showed that ants accumulated certain dietary fatty acids via direct trophic transfer. Fat content of the
diet had no effect on lipids stored by ants, which were able to synthesize high amounts of NLFAs from a sugar-based
diet. Nevertheless, dietary NLFAs had a strong effect on metabolic dynamics and profiles. Fatty acids are a useful tool to
study trophic biology of ants, and could be applied in an ecological context, although factors that affect NLFA patterns
should be taken into account. Further studies should address which NLFAs can be used as biomarkers in natural ant
communities, and how factors other than diet affect fatty acid dynamics and composition of species with
distinct life histories