Varying patterns on varying scales: A metacommunity analysis of nematodes in European lakes

Dümmer B, Ristau K, Traunspurger W. Varying patterns on varying scales: A metacommunity analysis of nematodes in European lakes. PLOS One. 2016;11(3): e0151866.Ecological community patterns are often extremely complex and the factors with the greatest influence on community structure have yet to be identified. In this study we used the elements of metacommunity structure (EMS) framework to characterize the metacommunities of freshwater nematodes in 16 European lakes at four geographical scales (radius ranging from 80 m to 360 km). The site characteristics associated with site scores indicative of the structuring gradient were identified using Spearman rank correlations. The metacommunities of the 174 nematode species included in this analysis mostly had a coherent pattern. The degree of turnover increased with increasing scale. Ordination scores correlated with geographical variables on the larger scales and with the trophic state index on a regional scale. The association of the structuring gradient with spatial variables and the scale-dependent increase in turnover showed that nematode dispersal was limited. The different metacommunity patterns identified at the increasing geographical scales suggested different, scale-related mechanisms of species distribution, with species sorting dominating on smaller and mass effects on larger geographical scales

Distributional patterns of lentic nematodes

Ristau K. Distributional patterns of lentic nematodes. Bielefeld; 2012

Biomass estimation across the benthic community in polluted freshwater sediment - a promising endpoint in microcosm studies?

Faupel M, Ristau K, Traunspurger W. Biomass estimation across the benthic community in polluted freshwater sediment - a promising endpoint in microcosm studies? Ecotoxicology and Environmental Safety. 2011;74(7):1942-1950

The functional response of a freshwater benthic community to cadmium pollution

Faupel M, Ristau K, Traunspurger W. The functional response of a freshwater benthic community to cadmium pollution. Environmental Pollution. 2012;162:104-109

Species and trait compositions of freshwater nematodes as indicative descriptors of lake eutrophication

Ristau K, Spann N, Traunspurger W. Species and trait compositions of freshwater nematodes as indicative descriptors of lake eutrophication. Ecological Indicators. 2015;53:196-205.In recent years, the analysis of single or multiple species trait patterns was regarded as a reliable biomonitoring tool alternative or in addition to the traditional taxon-based methods. Hitherto, the trait approach was overwhelmingly applied to macroinvertebrate assemblages to monitor anthropogenic induced degradations of freshwater ecosystems. However, little is known yet whether bio-ecological traits derived from speciose and functionally diverse meiobenthic taxa might also provide diagnostic descriptors for the assessment of ecosystem health. The aim of our pilot study was to assess if the trait composition (including life history, morphometrical and ecological attributes) of lake nematode assemblages can reflect signs of cultural eutrophication equally well as the concomitant change in the species composition. Sediment samples for the analysis of the nematodes assemblage structure were taken at littoral sites of 15 German and Swedish lakes. Lakes were assigned to three traditional classes along the trophic continuum— oligotrophic, mesotrophic, and eutrophic. Canonical correspondence analyses illustrated that both the nematode trait and species compositions were significantly altered to similar extents along the eutrophication gradient. A set of 7 out of 28 trait modalities and a group of 12 from 30 species could be defined as indicative of oligotrophic or eutrophic conditions, and enabled us to discriminate among the three trophic lake states, without confounding effects of pronounced trait intercorrelations. Trait modalities such as a high number of offspring per year and the feeding type suction feeder predominated at the upper range of the enrichment gradient, whereas for modalities such as the obligate asexual reproduction, the feeding type chewer and several specifying nematode morphometrics (short body length, slender body shape) the opposite trend was revealed. However, the observed trait replacement did not imply an increased potential of resilience or resistance to disturbance, suggesting that eutrophication effects rather indirectly shaped nematode assemblages. This first attempt to apply a trait-based analysis to nematode assemblages was found to be successful for distinguishing among different degrees of lake eutrophication. However, compared to macroinvertebrate taxa there remains a great paucity on bio-ecological trait data for nematode species. Therefore future research is demanded to expand and refine nematode trait specifications with the intention to gain further insights into the mechanistic link between responses of nematode populations to environmental alterations

The Anhydrobiotic Potential of the Terrestrial Nematodes Plectus parietinus and Plectus velox

Sandhove J, Spann N, Ristau K. The Anhydrobiotic Potential of the Terrestrial Nematodes Plectus parietinus and Plectus velox. JOURNAL OF EXPERIMENTAL ZOOLOGY PART A-ECOLOGICAL GENETICS AND PHYSIOLOGY. 2016;325(7):434-440.Within the taxon Nematoda, many species possess an anhydrobiotic potential similar to other microscopic animals, such as tardigrades and rotifers. This interesting capability enables them to survive conditions even of extreme dehydration. We examined the anhydrobiotic abilities of the two widespread terrestrial nematode species, Plectus parietinus and P. velox, by subjecting adult and juvenile life stages of both species to two different desiccation regimes, one with a short time of adaption (2 hr) and the other with a long time of adaption (48 hr) prior to complete desiccation and recorded the nematodes' recovery after 24 hr of rehydration. We found adults of P. parietinus to be the superior anhydrobiotes compared to adults of P. velox at short times of adaption, whereas at a long time of adaption this pattern was reversed. Moreover, our results showed that a long time of adaption significantly increased the recovery rate, independent of species or life stage. Additionally, we found adults to have a remarkable higher anhydrobiotic potential than juveniles, presumably due to a larger amount of resources in adult nematodes or due to a different morphology (cuticle, surface area to volume ratio). Plectus parietinus as well as P. velox showed a distinct anhydrobiotic potential although there were obvious differences between those two species, probably ascribable to different species-specific anhydrobiotic mechanisms and rates of water loss. (C) 2016 Wiley Periodicals, Inc

Genetic diversity of widespread moss-dwelling nematode species in German beech forests

Schenk J, Traunspurger W, Ristau K. Genetic diversity of widespread moss-dwelling nematode species in German beech forests. European Journal of Soil Biology. 2016;74:23-31

The D3-D5 region of large subunit ribosomal DNA provides good resolution of German limnic and terrestrial nematode communities

Schenk J, Hohberg K, Helder J, Ristau K, Traunspurger W. The D3-D5 region of large subunit ribosomal DNA provides good resolution of German limnic and terrestrial nematode communities. Nematology. 2017;19(7):821-837

The D3-D5 region of large subunit ribosomal DNA provides good resolution of German limnic and terrestrial nematode communities

Reliable and well-developed DNA barcode databases are indispensable for the identification of microscopic life. However, effectiveness of molecular barcoding in identifying terrestrial specimens, and nematodes in particular, has received little attention. In this study, ca 600 ribosomal large subunit DNA fragments (D3-D5 region) were successfully amplified for 79 limnic and terrestrial nematode species sampled at 147 locations across Germany. Distinctive DNA motifs in the LSU region were identified in 80% of all species examined. For 13 supposedly single morphospecies, 2-7 LSU barcode groups were detected with a wide range of intraspecific variations (0.09-7.9%). This region seems to be more suitable for the assessment of limno-terrestrial nematode diversity than the frequently used mitochondrial gene COI, as amplification success of the latter fragment is low for several nematode species. Our reference database for nematodes may serve as a starting point for applied and fundamental studies for these ubiquitous, ecologically highly relevant, organisms