The ratio of exotic-to-native dung beetles can indicate habitat quality in riparian restoration

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Abstract

1. Replanting natives on cleared riparian land is a common form of restoration. While most assessments of success are focussed on flora, the impact on fauna is often unknown.

2. We evaluated the effectiveness of revegetation for dung beetles in the riparian zone in a temperate Australian river. Total abundance, abundance of individual species, total species richness and species composition were compared using a chronosequence approach using four habitat types: unplanted; 1–3 and 7–10 year old revegetated plots, and mature native woodland.

3. A total of 1651 individuals and 20 species were trapped. Abundance and richness showed no trends across the chronosequence; however, changes in species composition appeared to be triggered by revegetation. Composition in older revegetation was more similar to mature woodland than the young revegetation or unplanted habitat. These shifts were largely due to a decline in the abundance and diversity of exotic dung beetles across the chronosequence.

4. Native revegetation also appeared to affect six species. Any of these six species could be used as indicators of progress in this region, but whether they are useful elsewhere cannot be guaranteed. This is a shortcoming of any study that recommends individual species as indicators.

5. Exotic-to-native ratios of plants are success indicators in restoration projects, and we suggest that this could also be used for monitoring success for invertebrate fauna. The exotic-to-native ratio has the advantage over single species indicators because the metric does not rely on those species being present in a particular region.