Morphometric and systematic analyses of populations of the Schwiebea barbei - group (acari: acaridae) with particular reference to populations from North America and Japan

Abstract

Statistical analyses using PCA (principal components analysis) and CAD (canonical analysis of discrimination) were conducted on morphological characters of five populations of Schwiebea mites of the “barbei” group (four from North America and one from Japan). The Japanese population was determined to be parthenogenetic, and other populations and nominal species in this group are probably parthenogenetic because of the lack of males in the populations. The four North American populations were generally clustered together in PCA while all five were discriminated from one another by CAD. When specimens from the type series of the nominal species, S. elongata, S. barbei, S. zingiberi, S. receptacula, S. similis, S. athiasae, S. obesa, S. codognoensis and S. estradai were included in PCA, most clustered with the original five populations. Inclusion of some of these individuals in CAD, however, resulted in discrimination only of S. estradai Within the Japanese population, reared in the laboratory from a single female foundress, considerable variation was noted in general size, the presence of dorsal seta dl, depth of indentation of prodorsal sclerite and spermathecal morphology, all characters previously used to separate species. We hypothesize that spermathecal morphology is the only reliable character which can distinguish populations. One of the five original populations is different from the others and is identified as S. zingiberi and the others are placed in S. elongata. We synonymize S. athiasae, S. barbei, S. codognoensis, S. obesa and S. receptacula with S. elongata based upon these morphological analyses, and suggest other nominal species (S. dissimilis, S. volgini, S. adzharica) may also be synonymous. Schwiebea estradai, S. similis and S. zingiberi are considered as distinct morphospecies based upon consistent differences in spermathecal morphology.