Pioneer herbaceous plants contribute to the restoration of pollination interactions in restinga habitats in tropical Atlantic Forest

The Brazilian Atlantic Forest is one of the most endangered biodiversity hotspots in the world and restinga ecosystems are exposed to intense degradation. The restoration of these ecosystems is challenging as there is a lack of understanding, among other aspects, of how plants interact with pollinators. Ecological networks are useful for assessing restoration outcomes as they provide data on the reestablishment of interactions. Here, we evaluated the restoration success of pollination interactions in a restinga in Brazil, by comparing structure, complexity, and robustness of plant-flower visitor networks in newly planted sites (restoration) with target reference sites (control). In the restoration area, more species and interactions were recorded (120 insect species, 25 plant species, and 1,361 interactions) compared to the control area (74, 19, and 471, respectively), mainly due to the high abundance of common insect species. The majority of the interactions in restoration sites (81.1%) occurred with naturally arriving pioneers (68% of plant species visited). While network robustness was significantly higher in restoration sites, as a result of a high number of generalist species, interaction evenness was significantly lower, indicating less uniformity in interaction frequencies compared to control sites. Interaction turnover was high, driven by differences in the composition of plants and insects between sites. Our results demonstrate that pollinating insects do reestablish interactions with herbaceous species, enabling their interaction with later flowering target plants in the most advanced stages of restoration. These results should be taken into consideration when proposing measures to attract and retain pollinators in areas under restoration.