Morphometric Variations in Leg Segments’ Length in the Family Dolichopodidae (Diptera)

Abstract

Interspecific variations of legs’ morphometric signs have been investigated on 2885 individuals from 65 species of 22 genera of the family Dolichopodidae. Nine morphometric signs of legs, including lengths of femora, tibia, and first segment of tarsi have been measured, and the data on 12 relative signs have been obtained. The results of analysis of variance showed significant differences between the genera but not between the subfamilies. Most of the studied signs showed weak phylogenetic signal. Significant phylogenetic signal has been found in only one of the studied signs: the ratio of length of mid legs' femora and tibia. Principal component analysis revealed the set of characters most typical for the family representatives as well as two general trends in leg morphometry diversity: elongation of the first segment of the mid- and hind-legs and variation in the ratio of fore-, mid-, and hind-femora. Cluster analysis revealed three morphologically distinguishable species groups that also differed in terms of their microhabitats: Medetera-like species (lengths of fore-, mid-, and hind-femora are nearly equal), Hydrophorus-like species (mid- and hind-femora and tibia are significantly extended regarding the fore-femora and tibia), and Sciapus-like species (all first segments of tarsi are significantly extended). Each of the identified groups includes species belonging to different subfamilies. Therefore, the similarity in leg morphometry features in dolichopodids is supported to be related to convergent evolution and not to the presence of a common ancestor with a similar morphology.