Interaction frequency is the most common currency in quantitative ecological networks, although interaction quality can also affect benefits provided by mutualisms. Here, we evaluate if interaction quality can modify network topology, species’ role and whether such changes affect community vulnerability to species loss. We use a well-examined study system (bird-lizard and fleshy-fruited plants in the ‘thermophilous’ woodland of the Canary Islands) to compare network and species-level metrics from a network based on fruit consumption rates (Interaction Frequency, IF), against networks reflecting functional outcomes: a Seed Dispersal Effectiveness network (SDE) quantifying recruitment, and a Fruit Resource Provisioning network (FRP), accounting for the nutrient supply of fruits. Nestedness decreased in the FRP and the SDE networks, due to the lack of association between fruit consumption rates and (1) nutrient content, and (2) recruitment at the seed deposition sites, respectively. The FRP network showed lower niche overlap due to resource use complementarity among frugivores. Interaction evenness was lower in the SDE network, in response to a higher dominance of lizards in the recruitment of heliophilous species. Such changes, however, did not result in enhanced vulnerability against extinctions. At the plant species level, strength changed in the FRP network in frequently consumed or highly nutritious species. The number of effective partners decreased for species whose seeds were deposited in unsuitable places for recruitment. In frugivores, strength was consistent across networks (SDE vs IF), showing that consumption rates outweighed differences in dispersal quality. In the case of lizards, the increased importance of nutrient-rich species resulted in a higher number of effective partners.

Our work shows that although frequency strongly impacts interaction effects, accounting for quality improves our inferences about interaction assembly and species role. Thus, future studies including interaction outcomes from both partners’ perspectives will provide valuable insights about the net effects of mutualistic interactions.

Data from manuscript "Changes in the structure of seed dispersal networks when including interaction outcomes from both plant and animal perspectives" 
by Aarón González-Castro, Teresa Morán López, Manuel Nogales and Anna Traveset.

DOI:10.1111/oik.08315

Simulations_outputs.RData file contains results from simulations performed to obtain:

IF (interaction frequency), FRP (fruit resource provisioning) and SDE (seed dispersal effectiveness) networks. Datasets are organized in arrays that have the structure [plants, animals, repetitions]. For example, FRP[,,1] contains the first repetition for the fruit resource provisioning network.

Dryad_upload.xls file contains mean networks (across 10000 repetitions) of IF, FRP and SDE.

Also, results from stochastic coextinction models (SCMs) according to scripts provided by Vieira et al. 2015 (https://doi.org/10.1111/ele.12394)

Full description of field methods can be found in the article main text, as well as in González-Castro et al. 2015 (https://doi.org/10.1890/14-0655.1).

Full description of simulations to obtain IF, SDE and FRP networks can be found in the main text and in the supplementary material.

Read_me.txt contains a more detailed description of files uploaded.