Foliage and ground spiders respond differently to a semi-natural habitat-vineyard gradient

Abstract

Natural vegetation in and around crops effectively increases predators. Semi-natural habitats (SNHs; non-crop vegetation) surrounding crops provide refuge and resources. However, the function of SNHs may depend on several factors, and the response of natural predators may vary among crops and regions. Here, we examined the spider community in a SNH and at an adjacent vineyard in a semi-arid region of Argentina. We collected spiders in a gradient from an adjacent SNH, towards the vineyard at three distances from the SNH using two techniques: beating and pit-fall traps. We collected spiders in December and February during two consecutive years at two strata: in vegetation and on the ground. In vegetation, spider abundance significantly decreased from SNH towards the interior of the vineyard at 80 m. On the ground, spider abundance was also significantly higher in SNH. However, after decreasing at the 5 and 20 m sites inside the vineyard, the abundance increased at 80 m. For foliage spiders, species richness followed the same pattern as abundance, whereas ground spider richness significantly increased from SNH to the interior of the vineyard. Species composition also showed different tendencies between foliage and ground spiders. The foliage spider community differed between SNH vs. all the vineyard sites. Contrarily, at the ground stratum, SNH was similar in composition to the edge of the vineyard, and they both differed from the other vineyard sites. We found that the adjacent SNH influenced the spider community in the vineyard and that this effect depended on the distance from that habitat and the association of the community to various strata. These results highlight the importance of studying the whole community of spiders when aiming to increase predator abundance to enhance biological control in this kind of crop. In addition, we found species that may act as indicators of native vegetation which has important implications for the management of natural habitats in this region.