Accelerating habitat degradation and fragmentation has highlighted the need for ecological restoration, yet evaluating restorative success remains difficult. Many restoration projects suffer from the lack of quantitative and comparative data, and focus solely on reinstating structure. However a functioning community is essential to ensure that ecological processes are in place, providing community resilience to future environmental perturbations. Ecological restoration has the potential to replace these ecosystem services.
Using a matched pairs design, we adopted a tri-trophic assessment of restoration success in communities of dry lowland heathland in southern England. Quantitative interaction webs were used to assess the degree to which interactions between flowering plants, their bumblebee pollinators, and a phylogenetically diverse array of bumblebee parasites, parasitoids and pathogens, were reinstated at restored relative to ancient reference sites.
Comparing webs from ancient and restored heathlands showed that both plant and bumblebee communities were successfully restored. Four species of external phoretic mites, and three internal gut protozoans were also found to be fully reinstated. However, the re-establishment of one of the parasitoids, the dipteran Conopidae, remained incomplete. Conopid larvae abundance, prevalence, load, frequency of superparasitism, and host range were significantly reduced at restored sites. These differences were substantial enough to impact upon web topology measures.
Our study supports the call for incorporating parasites into ecological networks, and highlights their particular worth in assessing restoration success, as their reliance upon the diversity and persistence of lower trophic levels will leave them to be amongst the last to re-establish in all ecological restoration projects.
