Differences between biota in anthropogenically fragmented habitats and in naturally patchy habitats

摘要

The extent to which the 'fragmented' properties of a landscape have actually been caused by anthropogenic fragmentation is often unknown. We can, however, understand links between spatial patterns of habitat in the current landscape and the biota. Built seawalls in Sydney Harbour, Australia, appear to fragment the natural, intertidal habitat. Rocky shores naturally occur, however, in a landscape of 'fragments', i.e. as patches of natural habitat separated by other natural habitats. To examine the extent to which fragmentation, i.e. due to human disturbance, has affected biota, we compared assemblages in these naturally patchy habitats to those in 'fragmented' habitats. Rocky shores were smaller and further apart from one another when surrounded by artificial habitat (called 'complete fragments') than when surrounded by other natural habitats (called 'natural patches'). This pattern matches the physical properties of 'fragmented landscapes'. We therefore tested whether patterns of diversity of biota in complete fragments, in mixed fragments (with one side adjacent to natural habitat and the other to artificial habitat) and in natural patches can be predicted from current models about the effects of the process of fragmentation. The number of taxa, number of unique taxa and variability in the number of taxa were all greater in natural patches than in mixed and complete fragments, although not all analyses were statistically significant. The current study supports notions that the composition and configuration of 'seascapes' is more important to the ecology of many marine organisms than previously thought.