Distance decay reveals contrasting effects of land-use types on arthropod community homogenization

Abstract

Global biodiversity decline with increasing land-use intensity is supposedly linked to the homogenization of species communities across landscapes. However, the contribution of landscape homogenization to insect diversity loss is still largely untested. We compared an indicator for community homogenization, the distance decay slope between four local habitats of increasing land-use intensity, from forests to managed grasslands, to arable lands and to settlements, imbedded in near-natural, agricultural and urban regions. This comparison was based on 12k arthropod species from 400 families, covering an area of 70.500 km². Distance decay – taking rarity and species traits into account - identified grasslands as the most homogenous local land-use type. In contrast, settlements and arable lands showed the most heterogeneous arthropod communities between locations. Large and low-mobility species communities were the most heterogeneous in space, but distance decay patterns were dependent on local land-use. Regional landscape type modified local land-use patterns: near-natural landscapes lowered, while agricultural landscapes increased the impact of homogenisation. Based on our findings we recommend enhanced conservation efforts particularly in grasslands to reverse current homogenization, while settlements and arable lands could be more strongly considered in insect beta-biodiversity heterogenization.