Detecting the Effects of Environmental Change Above the Species Level with Beetles in a Fragmented Tropical Rainforest Landscape

Abstract

1. Invertebrate data identified to coarse groupings according to taxonomy or ecology are easier to obtain than species-level data. However, it is unclear if such data are suitable for detecting environmental change. 2. We compared the performance of four types of data (species, family, trophic group, and body size) to quantify the responses of beetle assemblages with three types of environmental change on the Atherton Tableland in north-eastern Queensland, Australia. Clearing of rainforest creates two levels of environmental change: first the extreme, forest loss, and second, the more subtle change associated with forest fragmentation. A strong rainfall gradient across the study landscape also influences the biota, imposing a third type of environmental change, independent of rainforest modification. 3. Almost 20 000 beetles were sampled from six replicate sites in each of pasture, small rainforest remnants, and both the edges and interiors of large rainforest remnants. 4. All four types of data showed significant multivariate differences in assemblage composition between pasture and rainforest sites. Species-level data in multivariate analyses showed an effect of fragmentation on small remnants and also showed variation which corresponded with the spatial aridity gradient across sites. Both of these patterns were only weakly evident or were non-existent at the level of family, trophic group, or body size class. No level of taxonomic resolution gave consistently stronger results when univariate tests were applied to individual component taxa. 5. We conclude that data above the species level may not have the sensitivity required to detect more subtle forms of environmental change.