Morphological variation in different host populations of Abacarus hystrix (Acari: Prostigmata: Eriophyoidea).

The present systematic classification of Eriophyoidea is widely recognised as artificial and not reflecting plant-herbivore linkage. Quantitative description of host-related morphological variation can provide the basic information needed to improve the eriophyoid taxonomic system and enhance our understanding of mechanisms generating this variation. The purpose of this study was to investigate quantitative morphological traits of populations of cereal rust mite Abacarus hystrix (Nalepa 1896) living on different hosts. Three populations of A. hystrix collected from different grasses (Lolium perenne, Bromus inermis and Elytrigia repens) were examined morphologically. MANOVA analysis revealed significant differences in vectors of means among the three populations. Discriminant analysis yielded 11 traits that significantly differentiate the three populations. Analysis of canonical loadings showed that traits, which best discriminate the populations living on different hosts, are: body elongation, length of setae and overall body size. Host-dependent morphological variation is interpreted in terms of adaptation to specific environmental conditions created by the host. Hypotheses on the sources of this variation are discussed.