Can habitat loss be treated independently of habitat configuration? Implications for rare and common taxa in fragmented landscapes

Abstract

Habitat loss leads to a reduction in number of remnant habitats in continuous landscapes and inevitably leads to increased distances between habitats. We tested the independent and interactive effects of habitat number (number of suitable habitats per unit area) and habitat proximity (distance between these habitats) on assemblages of invertebrates associated with kelp holdfasts (Ecklonia radiata). We tested whether these kinds of habitat modifications have disproportionate effects on rare taxa. Loss and fragmentation of habitat did not operate independently. Patterns of diversity responded markedly to decreases in number of habitats, but this effect was reduced when neighbouring habitats were proximate rather than distant. Rare rather than common taxa primarily responded to these varying aspects of fragmentation. Results highlight the importance of considering the number of suitable habitats in an area (habitat number) when testing the influence of their isolation (habitat proximity) on biodiversity in fragmented landscapes. Awareness that number and proximity of patches are not independent at local scales may provide insights needed to predict the effects of habitat fragmentation on biodiversity, particularly on components of assemblages that tend to be rare.