Morphological approaches to community structure in hoverflies (Diptera, Syrphidae)

Abstract

Simulation techniques are used to generate random communities of hoverflies that can be com pared with observed communities: both the species composition and morphological size ratios are compared. Patterns of morphology are also examined through the study of size ratios within taxa. Three sites were surveyed, two man-made garden habitats, and one ancient woodland. The man-made habitats contained assemblages of species indistinguishable from species assembled randomly from those present in the county (area = 3400 km 2 ) as a whole, given the assumptions of the random model. The ancient woodland site contained significantly fewer species in common with the man-made habitats than expected from the random model. Size ratios (of both absolute and relative proboscis length) show a similar pattern, with non-random (constant) ratios observed among the common species in ancient woodland. Significantly constant proboscis length ratios were detected in two genera, Eristalis and Platycheirus . In the former, these are due to regular ratios of general body size. In Platycheirus , species have significantly regular differences in relative as well as absolute proboscis length.