Geographical variation in morphology and asymmetry in episyrphus balteatus degeer (Diptera: Syrphidae)

Abstract

An examination was conducted of morphological variation in Episyrphus balteatus (DeGeer) (Diptera: Syrphidae) from nine sites in the UK, Germany, Morocco and Madeira. Variation in total length, thorax width, wing length and asymmetry in wing length (males exhibited directional asymmetry, while females exhibited fluctuating asymmetry) was reduced to two factors (using principal components analysis), one of which represented size and the other asymmetry. These factors were then used in analyses of variance between sites. There was significant variation in size but not asymmetry between sites for both males and females. Post-hoc comparisons suggest that Madeiran males are relatively small, and females from one UK site were relatively large, but that overall there is considerable homogeneity between sites. We tentatively suggest that the Madeiran population may be resident.