Changes in Tetragnatha Spider Abundance and Web Characteristics Throughout Rice Field Development

Vegetation change is one of the major drivers affecting web-building spider species, causing them to vary in abundance and to adapt their web traits accordingly. Rice ecosystems are among the most important agricultural areas, and understanding the influence of vegetation complexity throughout rice development on common Tetragnatha spiders is crucial to developing sustainable management practices. Six sympatric species of Tetragnatha spiders, T. javana, T. mandibulata, T. maxillosa, T. nitens, T. praedonia and T. virescens, were found in rainfed lowland rice fields in southern Thailand. The abundance, web diameter and web height of each species were measured and compared across rice developmental stages. Overall, the number of Tetragnatha spiders was significantly higher in the tillering stage than the flowering stage, while abundance during the booting stage was not significantly different from either. The numbers of T. javana, T. mandibulata and T. maxillosa were higher than those of T. nitens, T. praedonia, and T. virescens during all rice stages. Throughout the rice growing season, vegetation complexity increased continuously while both web diameter and web height exhibited hump-shaped patterns for all spider species (i.e., webs were larger and built higher above ground level during the middle of the growing season). The diameter and height of Tetragnatha webs varied by species, but only web diameter was positively related to spider body length for almost all spider species. Our findings confirm that changes in vegetation complexity during rice development, as well as spider body length, affect the functional traits of Tetragnatha webs in rice ecosystems.