Ground-living invertebrate assemblages in native, planted and invasive vegetation in South Africa

Abstract

Invasive plants and plantations may be detrimental to native, ground-living, invertebrate fauna. Using pitfall traps at 20 sites in Pietermaritzburg, South Africa, an assessment was made of the distribution of epigaeic fauna under stands of the exotic invader plants: Acacia longifolia (long-leaved wattle), Acacia mearnsii (black wattle), Lantana camara (lantana) and Solanum mauritianum (bugweed), and also under a canopy of two major plantation trees: Eucalyptus grandis and Pinus patula. Control plots were minimally disturbed grassland and woodland in the same area. The effects of the invasive and cultured plants suggest that the impact is a complex interaction of factors. In general, there was a lower (but not significantly so) species richness, and also diversity, of invertebrates in exotic compared with indigenous vegetation. Certain individual species rather than whole families were affected most by these types of vegetation. There was a different assemblage of species associated with exotic compared with indigenous vegetation, with some species being good indicators for exotic or for indigenous vegetation. Although the weeds and vegetation caused a few species to increase in abundance, many other species decreased or even disappeared locally. Whereas different species assembled according to whether vegetation was exotic or indigenous, families and orders assembled along a gradient of closed to open canopy vegetation irrespective of origin. Although a few species were restricted to exotic vegetation (presumably having invaded at some time in the past from somewhere apart from the control sites), many others were restricted to indigenous vegetation. Vegetation management should be sensitive to the needs of certain invertebrate species so as to conserve them when native vegetation is replaced by exotics. Some management recommendations for conserving local invertebrate diversity are made.