Small-scale spatial heterogeneity and diversity of plant-flower visitor interactions in high mountains

Abstract

Anthropic homogeneization of habitats reduces biodiversity, but its effects on the occurrence and frequency of plant-flower visitor interactions are unknown. Here, we explore how environmental heterogeneity at small scale (tens of m) contributes to the diversity of plant-flower visitor interactions in two alpine ecosystems. To do this, we obtained plant-flower visitor networks in habitat mosaics in both ecosystems and assessed the importance of two kinds of interaction turnover among habitats: changes in species identity (species turnover); and differences in interactions of these shared species turnover among habitats, i.e. species interact only in a subset of the habitats in which they co-occur. Small-scale spatial heterogeneity increased interaction diversity, differences in interactions among shared species contributed greatly to interaction diversity and plant species interacted with more floral visitors where they were more abundant. Interactions varied spatially more than predicted by the variation of species, indicating that species turnover does not predict well the interaction turnover. This supports the important role of spatial heterogeneity to maintain a high diversity of plant-flower visitor interactions.