Community spiders in lemon crops (Citrus limon), conventional and abandoned management, Montevideo, Uruguay

Abstract

Spiders are generalist predators during all stages of their life and effective natural enemies of phytophagous insects in almost all terrestrial ecosystems. However, the number of spiders can drastically reduce in monocultures, due to different farming practices. The citrus crops have an architectural physiognomy favoring the formation of refuges and microhabitats, which determine the diversity of spiders, together with agricultural practices. We analyze the spider’s fauna with different agricultural practices in abandoned crop (AC) vs. conventional crop (CC). AC was the most abundant (n= 4202, 19 families) with respect to CC (n= 2567, 24 families). During the stages of crop development, in both farming systems increased amount of spiders was observed during the curdling (November), fruit formation-1 (December) and fruit formation-2 (January). The predominance of juveniles over adults in AC was 79.3% (n= 955) and 85.9% (n=600) in CC. The richness in AC was 121 species and 100 species in CC. The Margalef and Shannon-Wiener indices indicated a high diversity in both agricultural systems, being greater CC. The spider´s guild most abundant in AC and CC were the ground hunter’s runners (37.38%, 30.34%), the orb web weavers (24.81%, 24.11%) and the wandering irregular sheet web weavers (16.33%, 22.83%). The ground hunters runners guild, showed a greater abundance and species richness in both agricultural systems. The greatest dominance of species according to Simpson indices was represented by the weavers of orb web weaver’s guild in AC and CC. The greatest diversity observed according to the Margalef and Shannon-Wiener indices’, in AC corresponded to the stalkers hunter guild, while for CC, the ground hunters runners. This type of study attempts to raise awareness among agricultural producers, to reduce the indiscriminate use of pesticides and to promote the incorporation of other plants, such as ground cover and natural shelters for spiders and other natural enemies.