Specialists and generalists fulfil important and complementary functional roles in ecological processes

D. Matthias Dehling, Irene M.A. Bender, Pedro G. Blendinger, Katrin Böhning-Gaese, Marcia C. Muñoz, Eike L. Neuschulz, Marta Quitián, Francisco Saavedra, Vinicio Santillán, Matthias Schleuning, Daniel B. Stouffer

Research output: Contribution to journalArticlepeer-review

5 Scopus citations

Abstract

Species differ in their resource use and their interactions with other species and, consequently, they fulfil different functional roles in ecological processes. Species with specialized functional roles (specialists) are considered important for communities because they often interact with species with which few other species interact, thereby contributing complementary functional roles to ecological processes. However, the contribution of specialists could be low if they only interact with a small range of interaction partners. In contrast, species with unspecialized functional roles (generalists) often do not fulfil complementary roles but their contribution to ecological processes could be high because they interact with a large range of species. To investigate the importance of the functional roles of specialists versus generalists, we tested the relationship between species' degree of specialization and their contribution to functional-role diversity for frugivorous birds in Andean seed-dispersal networks. We used two measures for the specialization of birds—one based on the size, and one based on the position of their interaction niche—and measured their effect on the birds' contribution to functional-role diversity and their functional complementarity, a measure of how much a species' functional role is complementary to those of the other species. In all networks, there were similar log-normal distributions of species' contributions to functional-role diversity and functional complementarity. Contribution to functional-role diversity and functional complementarity increased with both increasing niche-position specialization and increasing niche size, indicating that the composition of functional roles in the networks was determined by an interplay between specialization and generalization. There was a negative interaction between niche-position specialization and niche size in both models, which showed that the positive effect of niche-position specialization on functional-role diversity and functional complementarity was stronger for species with a small niche size, and vice versa. Our results show that there is a continuum from specialized to generalized functional roles in species communities, and that both specialists and generalists fulfil important functional roles in ecological processes. Combining interaction networks with functional traits, as exemplified in this study, provides insight into the importance of an interplay of redundancy and complementarity in species' functional roles for ecosystem functioning. A free Plain-Language Summary can be found within the Supporting Information of this article.

Original languageEnglish
Pages (from-to)1810-1821
Number of pages12
JournalFunctional Ecology
Volume35
Issue number8
DOIs
StatePublished - Aug 2021

Bibliographical note

Funding Information:
DMD was supported by a grant from the German Research Foundation DFG (DE 2754/1-1). DMD also acknowledges funding from the European Research Council under the European Union’s Horizon 2020 research and innovation program (grant 787638) and the Swiss National Science Foundation (grant 173342), both awarded to C. H. Graham. P.G.B. acknowledges funding by CONICET (PIP 2014-592) and FONCyT (PICT 2013-1280). K.B.G., E.L.N., M.Q., V.S. and M.S. acknowledge funding by the German Research Foundation (DFG) in the framework of the Research Bundle 823–825 ‘Platform for Biodiversity and Ecosystem Monitoring and Research in South Ecuador’ (PAK 825/1) and the Research Unit FOR2730 ‘Environmental changes in biodiversity hotspot ecosystems of South Ecuador: RESPonse and feedback effECTs’. D.B.S. acknowledges the support of a Rutherford Discovery Fellowship and the Marsden Fund Council from New Zealand Government funding, both of which are managed by the Royal Society of New Zealand Te Apārangi (RDF-13-UOC-003 and 16-UOC-008).

Funding Information:
D.M.D. was supported by a grant from the German Research Foundation DFG (DE 2754/1‐1). P.G.B. acknowledges funding by CONICET (PIP 2014‐592) and FONCyT (PICT 2013‐1280). K.B.G., E.L.N., M.Q., V.S. and M.S. acknowledge funding by the German Research Foundation (DFG) in the framework of the Research Bundle 823–825 ‘Platform for Biodiversity and Ecosystem Monitoring and Research in South Ecuador’ (PAK 825/1) and the Research Unit FOR2730 ‘Environmental changes in biodiversity hotspot ecosystems of South Ecuador: RESPonse and feedback effECTs’. D.B.S. acknowledges the support of a Rutherford Discovery Fellowship and the Marsden Fund Council from New Zealand Government funding, both of which are managed by the Royal Society of New Zealand Te Apārangi (RDF‐13‐UOC‐003 and 16‐UOC‐008).

Publisher Copyright:
© 2021 British Ecological Society.

Keywords

  • Andean seed dispersal
  • ecosystem function
  • foraging niche
  • frugivory
  • interaction networks
  • plant–bird mutualism
  • redundancy
  • traits

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