Effects of landscape alteration on Hymenoptera trophic guilds at several scales of fragmentation in the Chaco forests of Cordoba, Argentina

MUSICANTE, M. L.; MONASTEROLO, M.; GALETTO, L.; SALVO, A.

Congreso; VII Southern Connection Congress; 2013

Winter deciduous dry tropical monsoon forests of the Chaco region are being destroyed at an accelerated pace, mainly due to the expansion of soya (200,000 ha/year). This study examines the impact of fragmentation of Chaco Serrano forests in the province of Córdoba, Argentina, on Hymenoptera trophic guilds in 9 forest fragments ranging in size from 0.5 to 10,500 hectares. Four sampling methods were used to detect the occurrence of a great number of species: observations on flowering plants, trap nests, pan traps and sweep nets. Parasitoids presented the highest species richness, while pollinators had the highest abundance, predators occupied an intermediate position, and cleptoparasites had the lowest numbers of species and individuals. Guild species richness varied according to fragment size, site features,distance to other fragments, and matrix (composition and heterogeneity). Although some species are lost with fragmentation, small fragments can maintain high species richness as long as the surrounding matrix provides heterogeneity with adequate food and nesting sites. Conversely, small fragments provide the surrounding matrix (typically soya cultivation and or areas of secondary regrowth) with services inversely proportional to their distance. Thus, even small fragments are essential to maintaining hymenopteran biodiversity and ecosystem services for both cultivated and native plants.