Similarities between predator mite populations (Acari: Gamasina) from natural forests in the Bucegi Massif, Romania

Ecological research of gamasid mites was carried out in three natural forest ecosystems with Picea abies (1350 m a.s.l.), Abies alba (950-1000 m a.s.l.) and Fagus sylvatica (1200 m a.s.l.) situated in the Bucegi Massif, Southern Carpathians, Romania during 2001-2003. In the studied forest ecosystems, the taxonomic structure of gamasids was represented by 11 families (Epicriidae, Parasitidae, Veigaiidae, Ameroseiidae, Aceosejidae, Rhodacaridae, Macrochelidae, Pachylaelapidae, Laelapidae, Eviphididae and Zerconidae), with 39 genera and 97 species. The maximum number of species was recorded in the ecosystem with Abies alba (80), followed by the ecosystem with Fagus sylvatica (73), while the minimum in the ecosystem with Picea abies (68). 2,016 samples, 97 species with 23,441 individuals were analysed. In order to show similarities between predator mite populations from these areas, the vegetation and some abiotic parameters of the soil (temperature, humidity, pH) were analysed and described. Similarities between gamasid mite populations from the investigated ecosystems were analysed using the Jaccard index (q). The highest similarity index (q = 0.706) was recorded between gamasids identified in Picea abies and Abies alba forests, at soil level, in comparison with those from Abies alba and Fagus sylvatica forests (q = 0.656). Based on the similarity index, it is discussed that the gamasid population structure was influenced by the type of soil, the specific composition of the herbaceous, shrub and tree layers, the microclimatic factors, all characteristic for each studied ecosystem.