Evolutionarily Distinct Species and Their Partners Have Fewer Links in Ecological Networks

Abstract

Aim

Ecological networks describe the complex set of interconnections among species and their environment, and network structure can inform the stability, resilience, and functioning of ecosystems. Increasing attention is being paid to the mechanisms that determine species interactions. Phylogeny has informed our understanding of connections within networks, mostly by describing the strength of phylogenetic conservation of interactions. Here, we examine how the phylogenetic position of a species relates to its functional position within a network, testing the relationship between phylogenetic and network topologies.

Location

Global.

Time Period

Early 20th century to present.

Major Taxa Studied

Birds and plants.

Methods

We used a large dataset of frugivore interactions to calculate the network degree of focal species (degree) and the partners they interact with (partner degree) and bird and plant phylogenies to calculate local evolutionary distinctiveness (ED), a measure of evolutionary distinctiveness calculated on a community-level phylogeny. We then fit binomial Bayesian models to estimate the effect of species' local ED on their degree and that of their partners. In avian networks, we incorporated bird traits from AVONET in models to determine their contributions to degree and partner degree relative to those of local ED.

Results

The partners of both high local ED birds and plants tend to have fewer interactions in a network than do partners of low local ED species, and birds with high local ED tend to interact with fewer plant species. In birds, the statistical effect sizes of local ED on degree and partner degree are comparable to or larger than those of measured traits.

Main Conclusions

Our analysis illustrates how phylogenetic relationships affect present-day ecologies and underscores the unique ecological contribution of evolutionary outliers.