Geographical variation in mutualistic networks: similarity, turnover and partner fidelity

Abstract

Although species and their interactions in unison represent biodiversity and all the ecological and evolutionary processes associated with life, biotic interactions have, contrary to species, rarely been integrated into the concepts of spatial b-diversity. Here, we examine b-diversity of ecological networks by using pollination networks sampled across the Canary Islands. We show that adjacent and distant communities are more and less similar, respectively, in their composition of plants, pollinators and interactions than expected from random distributions. We further show that replacement of species is the major driver of interaction turnover and that this contribution increases with distance. Finally, we quantify that species-specific partner compositions (here called partner fidelity) deviate from random partner use, but vary as a result of ecological and geographical variables. In particular, breakdown of partner fidelity was facilitated by increasing geographical distance, changing abundances and changing linkage levels, but was not related to the geographical distribution of the species. This highlights the importance of space when comparing communities of interacting species and may stimulate a rethinking of the spatial interpretation of interaction networks. Moreover, geographical interaction dynamics and its causes are important in our efforts to anticipate effects of large-scale changes, such as anthropogenic disturbances.

Ecological networks are more sensitive to plant than to animal extinction under climate change

“…Empirical studies have shown a high variability of mutualistic plant–animal interactions across years3031, suggesting a high flexibility in these networks. In contrast, recent studies have highlighted the importance of partner fidelity in both antagonistic and mutualistic ecological networks3233 that might be associated with a high degree of trait matching between interacting species in these networks3435. According to these studies, the flexibility of interactions will be constrained in ecological networks under future conditions, suggesting that unconstrained rewiring of interactions is unlikely even for generalized mutualistic networks.…”

Species interactions in an Andean bird–flowering plant network: phenology is more important than abundance or morphology

“…To explore similarity between sites, we calculated pairwise Sorenson dissimilarity indices for plant species observed in the three sites (see Trojelsgaard et al, 2015) where values close to 0 indicate very similar community composition and values close to 1 indicate very distinct communities. For our sites, Sorenson values ranged from 0.13 to 0.25, indicating very similar plant composition.…”

The use of DNA barcodes in food web construction—terrestrial and aquatic ecologists unite!

“…2B) will do so wherever and whenever they meet. While studies of ecological networks to date have mostly been concerned with the distribution of interactions within locations, and less so with the variation among locations, there is now ample evidence that ecological interactions vary in space and time (Poisot et al 2012;Trøjelsgaard et al 2015). It is in resolving how interaction structure varies with the environment (see Poisot et al 2012Poisot et al , 2015 that DNA barcodes will reveal their true potential.…”