A moveable feast: insects moving at the forest-crop interface are affected by crop phenology and the amount of forest in the landscape

GONZÁLEZ, E.; SALVO, A.; DEFAGO, M. T.; VALLADARES, G. R.

PLOS ONE

PUBLIC LIBRARY SCIENCE

Lugar: San Francisco; Año: 2016

1932-6203

Edges have become prevailing habitats, mainly as a result of habitat fragmentation andagricultural expansion. The interchange of functionally relevant organisms like insectsoccurs through these edges and can influence ecosystem functioning in both crop and noncrophabitats. However, very few studies have focused on the directionality of insect movementthrough edges, and the role of crop and non-crop amount has been ignored. Using bidirectionalflight interception traps we investigated interchange of herbivore, natural enemy,pollinator and detritivore insects between native forest fragments and soybean crops, simultaneouslyconsidering movement direction, forest cover in the landscape and crop phenology.In total, 52,173 specimens and 877 morphospecies were collected. We found that,within most functional and taxonomic groups, movement intensity was similar (richnessand/or abundance) between directions, whereas a predominantly forest-to-crop movementcharacterized natural enemies. Insect movement was extensively affected by crop phenology,decreasing during crop senescence, and was enhanced by forest cover particularly atsenescence. Mainly the same herbivore species moved to and from the forest, but differentnatural enemy species predominated in each direction. Finally, our analyses revealedgreater forest contribution to natural enemy than to herbivore communities in the crop, fadingwith distance to the forest in both groups. By showing that larger amounts of forest leadto richer insect interchange, in both directions and in four functional groups, our study suggeststhat allocation to natural and cultivated habitats at landscape level could influencefunctioning of both systems. Moreover, natural enemies seemed to benefit more than pestsfrom natural vegetation, with natural enemy spillover from forests likely contributing to pestcontrol in soybean fields. Thus consequences of insect interchange seem to be mostly positivefor the agroecosystem, although consequences for the natural system deserve furtherstudy.