Hoverflies as a biodiversity tool
Syrphids: a tool for biodiversity management
Maintenance of biodiversity can be regarded as a function of habitats. The performance of the biodiversity maintenance function in a particular habitat can be assessed and then, through management, modified. Assessment of the performance of the biodiversity maintenance function of a site can be achieved by comparison between the expected biodiversity of the combination of habitats present on that site and their observed biodiversity. Syrphids represent the ideal model for this approach. It is an example of use of the “expert system” approach in biodiversity maintenance: an expert system may be defined as “a computer programme into which has been incorporated the knowledge of experts on a particular subject so that non‐experts can use it for making decisions, evaluations or inferences”.
Why are Syrphids such a useful group for assessing the biodiversity function of habitats?
- The national Syrphid checklist is sufficiently stable at 180 species (new species are not being continually added), the literature on syrphid identification is accessible, and most species can be identified with confidence [in contrast to groups like parasitic wasps].
- The ecology and life history of Irish syrphid species is well known. As a consequence of many years of effort by experts, sufficient habitat, microhabitat and trait information is available for more than 95% of the Irish syrphid species [in contrast to groups like solitary bees].
- Because the various species inhabit different parts of the ecosystem, syrphids can provide information about all habitat strata, from grass‐root zone to the canopy of dominant forest trees. They also occur in a wide range of habitat types, there being species characteristic of nearly all of the non‐marine habitats that occur in Ireland, except large or deep water bodies, cliffs and caves [in contrast to groups like dragonflies and ground beetles (Carabidae)].
- Syrphids can be efficiently collected in a standardised way using malaise traps. Furthermore, the large catchment area of an individual Malaise trap ensures that the material it collects provides information about more than the immediate vicinity of the trap, making them suitable for landscape-scale investigations. The sample bottles collected from Malaise traps can also be used for storage of samples, and upon extraction, the specimens are immediately available for identification. There are many taxonomic groups that are not susceptible to standardised trapping methods, like the long-horn beetles (Cerambycidae), which would otherwise have considerable potential in woodland interpretation. Other taxonomic groups, like spiders and molluscs, can be sampled by standardised methodology but require time-consuming sorting, to extract them from the samples of soil or other debris making up the greater part of the samples.
- Finally, there is one advantage to using syrphids that makes them almost unique among European terrestrial invertebrates – information needed for the interpretation of species lists has already been databased and is available to those who wish to use it for analytical procedures, in the form of the StN database, from which the Database of Irish Syrphidae is derived.
Speight, M. C. D. (2008). Database of Irish Syrphidae (Diptera). Irish Wildlife Manuals, No. 36. National Parks and Wildlife Service, Department of Environment, Heritage and Local Government, Dublin, Ireland. Syrphids_IWM This file is 6.7MB in size and contains a pdf version of the Irish Wildlife Manual along with an accompanying excel database.