Edge effects on flower-visiting insects in grapefruit plantations bordering premontane subtropical forest

CHACOFF, N.P Y M.A. AIZEN

JOURNAL OF APPLIED ECOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2006 vol. 43 p. 18 - 27

0021-8901

1.Over the last decade, there has been much concern about the decline in pollinatorabundance and diversity caused by different types of anthropogenic disturbances,including deforestation and habitat fragmentation. However, little empirical informationexists documenting this decline and its consequences for cultivated floweringcrops. We tested the hypothesis that remnants of natural habitats act as a source offlower-visiting insects for neighbourhood crops.2.Over 3 consecutive years we evaluated flower-visiting insect diversity, visitationfrequency and composition in four grapefruitCitrus paradisiMacf. plantations atincreasing distances (edge, 10, 100, 500 and 1000 m) from remnants of subtropicalpremontane forest in NW Argentina.3.The frequency of visits to grapefruit flowers decreased by more than twofold as distanceto the forest increased and the flower-visiting fauna became more depaupurate.Even the feral africanized honeybeeApis mellifera, the dominant flower visitor to grapefruitflowers, showed a decline at distances > 500 m from the forest edge. However, thegreatest relative declines occurred among stingless and solitary bees as well as othernative flower visitors, which were rarely seen a few hundred metres inside the plantations.In addition, flower-visiting insect faunas among plantations became morehomogeneous as distance from the edge increased.4.These trends were consistent over years and among plantations up to 50 km apart.Thus, we can conclude that negative forest edge effects on flower-visiting insects insidegrapefruit plantations are widespread in the increasingly deforested landscape of NWArgentina.5.Synthesis and applications. This study provides empirical evidence for consideringremnants of natural habitats as a source of both native and alien flower-visiting insectsthat can be potential pollinators for agriculture. Increasing edge density in agriculturallands, through preservation and restoration of natural habitats, can foster stocks ofdiverse and abundant insect pollinators.