Factors affecting abundance and species composition ofgeneralist predators (Tetragnathaspiders)in agricultural ditches adjacent to rice paddy fields

Publication date: Available online 3 September 2016 Source:Biological Control Author(s): Yuki G. Baba, Koichi Tanaka Agricultural ditches adjacent to paddy fields are expected to provide an alternative habitat to the fields for Tetragnatha spiders, a major component of the natural enemies of crop pests in rice paddy ecosystems. To better understand the spatial distribution of these spiders in agroecosystems, it is essential to evaluate their abundance and species composition in such alternative habitats. Here, we examined the factors determining abundance and species composition of Tetragnatha spiders in agricultural ditches around rice paddy fields. Field surveys were conducted in transects set along 43 concrete ditches in the northern Kanto region, Japan, prior to the rice growing season when spiders are absent in paddy fields. Four species of Tetragnatha spiders were found, with two species (T. maxillosa and T. extensa) accounting for 95% of the total abundance. These two species showed different responses to local and landscape factors. The abundance of T. maxillosa increased with ditch width, whereas that of T. extensa was highest at intermediate width. Vegetation height had a positive effect on the abundance of T. maxillosa but a negative one on that of T. extensa. Distance to the nearest forest had no effect on T. extensa, but negatively influenced T. maxillosa, indicating that forest environments are beneficial to the latter. Reflecting these differences, the prop...
Source: Biological Control - Category: Biology Source Type: research