Functional diversity mediates macroecological variation in plant–hummingbird interaction networks
Authors: Maruyama Pietro Kiyoshi , Sonne Jesper , Vizentin‐Bugoni Jeferson , Martín González Ana M. , Zanata Thais B. , Abrahamczyk Stefan , Alarcón Ruben , Araujo Andréa C. , Araújo Francielle P. , Baquero Andrea C. , Chávez‐González Edgar , Coelho Aline G. , Cotton Peter A. , Dehling D. Matthias , Fischer Erich , Kohler Glauco , Lara Carlos , Las‐Casas Flor Maria G. , Machado Adriana O. , Machado Caio G. , Maglianesi María A. , Malucelli Tiago S. , Marín‐Gómez Oscar Humberto , Oliveira Paulo E. , Ornelas Juan Francisco , Ortiz‐Pulido Raul , Ramírez‐Burbano Mónica B. , Rocca Márcia A. , Rodrigues Licléia C. , Rosero‐Lasprilla Liliana , Rui Ana M. , Sandel Brody , Svenning Jens‐Christian , Tinoco Boris A. , Varassin Isabela G. , Watts Stella , Rahbek Carsten , Sazima Marlies , Schleuning Matthias , Dalsgaard Bo 
Published: August 2018

Aim

Species interaction networks are known to vary in structure over large spatial scales. We investigated the hypothesis that environmental factors affect interaction network structure by influencing the functional diversity of ecological communities. Notably, we expect more functionally diverse communities to form interaction networks with a higher degree of niche partitioning.

Location:

Americas.

Time period:

Current.

Major taxa studied:

Hummingbirds and their nectar plants.

Methods

We used a large dataset comprising 74 quantitative plant–hummingbird interaction networks distributed across the Americas, along with morphological trait data for 158 hummingbird species. First, we used a model selection approach to evaluate associations between the environment (climate, topography and insularity), species richness and hummingbird functional diversity as predictors of network structure (niche partitioning, i.e., complementary specialization and modularity). Second, we used structural equation models (SEMs) to ask whether environmental predictors and species richness affect network structure directly and/or indirectly through their influence on hummingbird functional diversity. For a subset of 28 networks, we additionally evaluated whether plant functional diversity was associated with hummingbird functional diversity and network structure.

Results

Precipitation, insularity and plant richness, together with hummingbird functional diversity (specifically, functional dispersion), were consistently strong predictors of niche partitioning in plant–hummingbird networks. Moreover, SEMs showed that environmental predictors and plant richness affected network structure both directly and indirectly through their effects on hummingbird functional diversity. Plant functional diversity, however, was unrelated to hummingbird functional diversity and network structure.

Main conclusions:

We reveal the importance of hummingbird functional diversity for niche partitioning in plant–hummingbird interaction networks. The lack of support for similar effects for plant functional diversity potentially indicates that consumer functional diversity might be more important for structuring interaction networks than resource functional diversity. Changes in pollinator functional diversity are therefore likely to alter the structure of interaction networks and associated ecosystem functions.