PARENT SESSION
MA4 The Use of Ecological Models and Concepts in Aquatic Higher Tier Risk Assessment.
9:00 AM to 12:30 PM, Monday, 07 May 2001
Session Chair: Paul van den Brink
Room 4

(033) A metapopulation approach to investigating population recovery potential in fragmented aquatic landscapes.

Waller, Martin¹, Kedwards, Tim¹, ¹

ABSTRACT- Ponds are important habitats in terms of both biodiversity and refuges of rare or local species. They are predominant in many agricultural landscapes , with approximately 225,000 water bodies in lowland landscapes (or roughly 1.5 every square km), and when not connected by streams can be considered as island habitats. Where they are in proximity to agricultural fields, there is the potential for contamination by crop protection products through drift. This in turn may pose a risk to the indigenous populations of non-target organisms. In order to increase our understanding of how affected populations might recover in such fragmented habitats, a spatially explicit meta-population model was developed with the objective of investigating population recovery probabilities and recolonisation times of physically unconnected ponds subject to population losses. Recolonisation of ponds is through immigration of reproducing stages, as exemplified by the alate adults of many aquatic insects. Other forms of recolonisation (such as passive transfer of propagules or spread through connected pond systems) are not currently considered in this example. A monte-carlo simulation approach was used to investigate the importance of dispersal ability in conjunction with other population characteristics (reproductive rate, voltinism, etc.) on population recovery potential. The model considers a system of two or more spatially separated ponds, with populations characterised by growth (number of stages, development rate, fecundity, etc.) and dispersal (dispersal distance probability). By altering the size, number and distance between ponds, and changing the life-history characteristics of the organisms, the effects on recovery times as functions of these parameters are considered and the results discussed in the context of pesticide risk assessment. The approach provides a useful tool for identifying a range of landscapes and life-history types that are likely to be most and least susceptible to environmental disturbances.

Key words: meta-population, aquatic, recovery, pesticides