Habitat restoration and the diversity of species interactions

Small-scale habitat restoration of different ecosystems has taken place in Mauritius over the past 20 to 30 years. Currently this is done by manually weeding the dominant alien invasive plant species, replanting native plants and excluding or eradicating alien animals, which is partly effective but cost and labour intensive. We evaluate the success of this management by comparing(1) quantified interaction webs of flowering plants and their associated pollinators in restored and unrestored upland heath areas and (2) quantified food webs of a reptile community on an offshore island. The restored pollinator web showed higher species richness, interaction diversity and abundance than the unrestored web. However, pollinators of particular taxa consisted to a high degree of exotic species in both restored and unrestored habitats. We describe the reptile food web based on a plant community recovering from heavy grazing by invasive mammals and show that the consumer community has improved in terms of reptile population sizes. We show that interaction diversity is linked to the specific habitat type and identify the species which can connect the different sub-webs. As a new management tool to eradicate alien invasive plant species that still present an obstacle to full recovery of the ecosystems, we propose the use of tortoises that had key roles in grazing and seed dispersal in the past. We present first result on their effectiveness in removing alien plant species in a grazing experiment.