Stratification and seasonal dynamics of weevil (Coleoptera, Curculionoidea) assemblages in the North Caspian semi-desert

In 2003–2004, 102 species of five weevil families were found in the steppe and desert associations of the Caspian semi-desert (Dzhanybek Station). Representatives of Curculionidae predominated (87 species). The majority of the commonest weevil species (20) were most abundant in the steppe associations, only 6 species being found in the desert ones. The composition of the weevil community changed abruptly from spring to summer. The greatest species richness (86 species) was observed in spring; only in this period weevils living mostly on the soil surface had high densities. In the herbage, both in the steppe and desert communities, detritophagous steppe species Archaeophloeus inermis and Trachyphloeus amplithorax were abundant; the habitats of the solonetz complex (on microelevations and in the depressions), the desert-steppe and steppe species ( Humeromima nitida, Mesagroicus poriventris, Temnorhinus strabus ) associated with saline substrates were also present. The spring hortobiont assemblage was dominated by the polyphagous steppe weevils, Euidosomus acuminatus, Phyllobius brevis and Omias spp. In summer, 53 species of weevils were recorded; their numbers on the soil surface sharply dropped, the core of the herbage assemblage consisted of the weevils feeding on alfalfa ( Stenopterapion tenue, Sitona spp., Tychius spp.) in the steppe associations, with the maximum abundance in the more humid depressions. The summer assemblage of the desert herbage was poor and consisted of the species associated with wormwoods and chenopods ( Ptochus porcellus, Phacephorus argyrostomus, Metadonus anceps ). The autumn groupings with only 24 species were poor and had low population densities.