Entomopathogenic nematodes (EPN) are soil-transmitted parasites and their foraging strategies are believed to range from 'ambush' to 'cruise' foragers. However, research on their behaviour has not considered the natural habitat of these nematodes. We hypothesized that EPN behaviour would be influenced by soil habitat quality and tested this hypothesis using 2 EPN species Steinernema carpocapsae (an 'ambusher') and Heterorhabditis megidis (a 'cruiser') in 2 contrasting habitats, sand and peat. As predicted from previous studies, in sand most S. carpocapsae remained at the point of application and showed no taxis towards hosts, but in peat S. carpocapsae dispersed much more and showed a highly significant taxis towards hosts. H. megidis dispersed well in both media, but only showed taxis towards hosts in sand. In outdoor mesocosms in which both species were applied, S. carpocapsae outcompeted H. megidis in terms of host finding in peat, whereas the opposite was true in sand. Our data suggest that these 2 EPN may be habitat specialists and highlight the difficulties of studying soil-transmitted parasites in non-soil media.

A major gap in our understanding of biodiversity-ecosystem function relationships concerns the role of intra- and interspecific diversity of mycorrhizal fungi, which are critical for plant fitness, biogeochemical cycling and other processes. Here, we test the hypothesis that the identity and richness of ectomycorrhizal (ECM) fungi at the intra- and interspecific levels affect ecosystem multifunctionality by regulating plant and fungal productivity, soil CO efflux and nutrient retention. Microcosms containing Scots pine (Pinus sylvestris) seedlings colonized by different ECM fungal isolates, in monocultures and mixtures, enabled us to test for both intra- and interspecific identity and richness effects, and transgressive overyielding. Intra- and interspecific identity had modest but significant effects on plant and fungal productivity and nutrient retention, but no effect on CO efflux. Intraspecific richness increased plant root productivity and ECM root tips but decreased hyphal length, whereas interspecific richness had no effects. Interspecific mixtures outperformed the most productive monocultures in only 10% of the cases, compared with 42% for the intraspecific mixtures. Both intra- and interspecific identity and richness of ECM fungi regulate ecosystem multifunctionality, but their effects on the direction and magnitude of individual variables differ. Transgressive overyielding suggests that positive niche complementarity effects are driving some of the responses to intraspecific richness.

Freshwater ecosystems in the mid-to upper-latitudes of the northern hemisphere are particularly vulnerable to the impact of climate change as slight changes in air temperature can alter the form, timing, and magnitude of precipitation and consequent influence of snowmelt on streamflow dynamics. Here, we examine the effects of hydro-climate, flow regime, and hydrochemistry on Plecoptera (stonefly) alpha (a) diversity and distribution in northern freshwater ecosystems. We characterized the hydroclimatic regime of seven catchments spanning a climatic gradient across the northern temperate region and compared them with estimates of Plecoptera genera richness. By a spacefor-time substitution, we assessed how warmer temperatures and altered flow regimes may influence Plecoptera alpha diversity and composition at the genus level. Our results show wide hydroclimatic variability among sites, including differences in temporal streamflow dynamics and temperature response. Principal component analysis showed that Plecoptera Handling editor: Mariana MeerhoffElectronic supplementary material The online version of this article (genera richness was positively correlated with catchment relief (m), mean and median annual air temperature (°C), and streamflow. These results provide a preliminary insight into how hydroclimatic change, particularly in terms of increased air temperature and altered streamflow regimes, may create future conditions more favorable to some Plecopteras in northern catchments.

Effects of biodiversity on productivity are more likely to be expressed when there is greater potential for niche complementarity. In soil, chemically complex pools of nutrient resources should provide more opportunities for niche complementarity than chemically simple pools. Ectomycorrhizal (ECM) fungal genotypes can exhibit substantial variation in nutrient acquisition traits and are key components of soil biodiversity. Here, we tested the hypothesis that increasing the chemical complexity and forms of soil nutrients would enhance the effects of intraspecific ECM diversity on host plant and fungal productivity. In pure culture, we found substantial variation in growth of strains of the ECM fungus Laccaria bicolor on a range of inorganic and organic forms of nutrients. Subsequent experiments examined the effects of intraspecific identity and richness using Scots pine (Pinus sylvestris) seedlings colonized with different strains of L. bicolor growing on substrates supplemented with either inorganic or organic forms of nitrogen and phosphorus. Intraspecific identity effects on plant productivity were only found under the inorganic nutrient amendment, whereas intraspecific identity affected fungal productivity to a similar extent under both nutrient treatments. Overall, there were no significant effects of intraspecific richness on plant and fungal productivity. Our findings suggest soil nutrient composition does not interact strongly with ECM intraspecific richness, at least under experimental conditions where mineral nutrients were not limiting. Under these conditions, intraspecific identity of ECM fungi becomes more important than richness in modulating plant and fungal performance.

The soil-dwelling nematodes Steinernema carpocapsae, S. scapterisci, S. feltiae, S. glaseri, Heterorhabditis bacteriophora, H. megidis, Phasmarhabditis hermaphrodita and Caenorhabditis elegans were placed on agar plates each containing four substrates (peat, sand, sandy loam and leaf litter). The body-waving behaviour of infective juveniles was recorded over a 10-day period in the presence or absence of an insect, Galleria mellonella, a susceptible host of some species. Body-waving behaviour differed amongst species and varied significantly in relation to substrate, time and the presence of G. mellonella. Steinernema carpocapsae showed body-waving behaviour more than other species and this tendency increased significantly with time. More S. carpocapsae were seen body waving on peat and leaf litter than on either sandy loam or sand. Conversely, sand promoted body waving in S. scapterisci. Body waving by C. elegans was more common on peat than on any of the other substrates. Heterorhabditis megidis, not previously known to body wave, did so in low numbers on peat and sandy loam. The remaining four species did not body wave. Previous work has shown that the presence of S. glaseri increases body waving by S. carpocapsae. We investigated whether substrate influenced this interaction and also included S. scapterisci in the study. The presence of S. glaseri significantly altered rates of body waving in S. carpocapsae and S. scapterisci in a way that was substrate-dependent. Our data suggest that body-waving behaviour is determined by substrate quality and differing body-waving behaviours may be a mechanism by which nematodes avoid competition.