The influence of habitat quality on the foraging strategies of the entomopathogenic nematodes Steinernema carpocapsae and Heterorhabditis megidis

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

Strain identity of the ectomycorrhizal fungus Laccaria bicolor is more important than richness in regulating plant and fungal performance under nutrient rich conditions

This work was funded by the Natural Environment Research Council (NE/I014527/1).Peer reviewedPublisher PD

Influence of habitat on the behaviour of entomopathogenic nematodes

In seeking new hosts, entomopathogenic nematode foraging strategies are believed to range from sit-and-wait foragers (ambushers) to widely active foragers (cruisers).  This study investigated the behaviour, dispersal and competitive ability of entomopathogenic nematodes of the genera Heterorhabditis and Steinernema in relation to soil habitat. The host finding and competitive ability of Steinernema carpocapsae, an “ambusher” and Heterorhabditis megidis, a “cruiser” in two contrasting soil habitats (sand and peat) showed “habitat-specific” differences in foraging mode between the two species.  In peat, S. carpocapsae outcompeted H. megidis in terms of host finding, whereas the opposite was true in sand.  In the appropriate habitat, both nematodes showed behaviours not predicted by their supposed foraging strategy.  Experiments examining the interspecific interactions between S. carpocapsae and H. megidis also showed significant differences in the population dynamics between the two species in relation to habitat. Nictation behaviour is frequently cited as a host finding strategy in ambush foraging nematodes. The study confirms that ambush foraging species S. carpocapsae and Steinernema scapterisci frequently nictate, but show that habitat is an important factor regulating this behaviour.  This study also demonstrates the ability of the cruise foraging nematode, H. megidis to nictate on habitats not previously examined.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Analysis of hydrological seasonality across northern catchments using monthly precipitation–runoff polygon metrics

Seasonality is an important hydrological signature for catchment comparison. Here, the relevance of monthly precipitation–runoff polygons (defined as scatter points of 12 monthly average precipitation–runoff value pairs connected in the chronological monthly sequence) for characterizing seasonality patterns was investigated to describe the hydrological behaviour of 10 catchments spanning a climatic gradient across the northern temperate region. Specifically, the research objectives were to: (a) discuss the extent to which monthly precipitation–runoff polygons can be used to infer active hydrological processes in contrasting catchments; (b) test the ability of quantitative metrics describing the shape, orientation and surface area of monthly precipitation–runoff polygons to discriminate between different seasonality patterns; and (c) examine the value of precipitation–runoff polygons as a basis for catchment grouping and comparison. This study showed that some polygon metrics were as effective as monthly average runoff coefficients for illustrating differences between the 10 catchments. The use of precipitation–runoff polygons was especially helpful to look at the dynamics prevailing in specific months and better assess the coupling between precipitation and runoff and their relative degree of seasonality. This polygon methodology, linked with a range of quantitative metrics, could therefore provide a new simple tool for understanding and comparing seasonality among catchments

McDonnellJeffreyJForestEngineeringResourcesManagementHydroclimaticHydrochemicalControls.pdf

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. Wecharacterized 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 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

Contrasting effects of intra- and interspecific identity and richness of ectomycorrhizal fungi on host plants, nutrient retention and multifunctionality

Acknowledgements This work was funded by the Natural Environment Research Council (NE/I014527/1). We thank Prof. I. C. Anderson for scientific discussions and Dr H. Weitz for technical support. We also thank the referees for their helpful input. A.F.S.T. receives funding from the Scottish Government.Peer reviewedPostprin