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Project title

Monitoring, functional significance and management tools for the maintenance and economic utilisation of bio-diversity in the farmed landscape(Ag-Biota)

Primary Funding Agency

Environmental Protection Agency

Co-Funding Organisation(s)

n/a

Lead Organisation

University College Dublin (UCD)

Lead Applicant

Gordon Purvis

Project Abstract

This study set out to test the hypothesis that parasitoid wasps (Hymenoptera: Parasitica) are suitable bioindicators for and can provide a useful means to assess the wider biodiversity of arthropod populations in agro-ecosystems. There is a wide range of theoretical arguments to support such a claim including the high trophic position of these taxa within the arthropod communities in which they occur and the unique nature of their biological relationships with the vast majority of terrestrial insect groups. Currently grassland can be managed according to REPS specifications by reducing only the intensity of nitrogen use and stocking rates. However if the widely used method of intensive grass utilisation by short-term rotational grazing and conservation for silage remains unchanged our data suggest that the net benefit for biodiversity is likely to be small. More detailed studies of alternative grazing and grass utilisation systems are required to maximise the potential biodiversity benefits of REPS policy.A total of 178 genera of parasitoid Hymenoptera were identified in agricultural grasslands during the study. These identifications have been verified by independent taxonomic experts and include ten taxa not previously recorded from Ireland. All taxa including the new records were collected from moderately-to-intensively managed grasslands suggesting that even in such commonplace habitats there may be much Irish biodiversity yet to be discovered. Using multiple data sets we show that in agricultural grasslands both the abundance and diversity of parasitoid wasp taxa are more closely correlated with overall arthropod diversity than is the incidence of any other insect group; a fact that provides us with a practicable and usable monitoring tool for tracking change in wider arthropod diversity.Assessment of parasitoid assemblages in existing Teagasc field experiments contrasting different aspects of grassland husbandry (the use of conservation field margins at Johnstown Castle and the reduction of nutrient inputs and stocking rates at Johnstown Castle and Grange) showed a consistent pattern of management effects on parasitoid abundance diversity and altered community structure; parasitoid taxa associated with predictable host groups such as aphids and dung-breeding Diptera being more prominent in more intensive grassland treatments while a greater diversity of parasitoids of particularly well concealed plant-mining and gall-forming insect larval hosts and insect and spider eggs being characteristic of more extensive management treatments. The degree to which such management effects are apparent is effectively a reflection of the relative contrast in the i'intensityi of the systems being compared. These results support previous work that has shown the overwhelming importance of grassland sward structure on arthropod populations. The project has confirmed the initial hypothesis and illustrated the bioindicator potential of parasitoids populations. The total abundance of parasitoids is a reliable and relatively easily measured indicator of overall arthropod diversity in agricultural grasslands providing an eminently user friendly monitoring tool. However the project has also shown that a more detailed knowledge of parasitoid taxonomy biology and host groups can provide a unique ecological insight into underlying environmental influences affecting wider arthropod biodiversity and community structure. With improving knowledge of their host group relationships parasitoids offer a unique means to study the highly i'cryptici hidden biodiversity that occurs even in the most mundane of habitats and which would otherwise be almost impossible to assess directly by any other means.

Grant Approved

�202,343.00

Research Hub

Natural Environment

Research Theme

Sectoral Impacts on Biodiversity

Start Date

01/12/2003

Initial Projected Completion Date

n/a