title: The Evolution of Functionally Redundant Species; Evidence from Beetles.
abstract: While species fulfill many different roles in ecosystems, it has been suggested that numerous species might actually share the same function in a near neutral way. So-far, however, it is unclear whether such functional redundancy really exists. We scrutinize this question using extensive data on the world's 4168 species of diving beetles. We show that across the globe these animals have evolved towards a small number of regularly-spaced body sizes, and that locally co-existing species are either very similar in size or differ by at least 35%. Surprisingly, intermediate size differences (10-20%) are rare. As body-size strongly reflects functional aspects such as the food that these generalist predators can eat, these beetles thus form relatively distinct groups of functional look-a-likes. The striking global regularity of these patterns support the idea that a self-organizing process drives such species-rich groups to self-organize evolutionary into clusters where functional redundancy ensures resilience through an insurance effect.
authors.affiliation: Department of Aquatic Ecology and Water Quality Management, Wageningen University, P.O. Box 47, NL-6700 AA, Wageningen, The Netherlands.
authors.forename: Marten
authors.initials: M
authors.lastname: Scheffer
authors.affiliation: Department of Aquatic Ecology and Water Quality Management, Wageningen University, P.O. Box 47, NL-6700 AA, Wageningen, The Netherlands.
authors.forename: Remi
authors.initials: R
authors.lastname: Vergnon
authors.affiliation: Department of Aquatic Ecology and Water Quality Management, Wageningen University, P.O. Box 47, NL-6700 AA, Wageningen, The Netherlands.
authors.forename: Egbert H
authors.initials: EH
authors.lastname: van Nes
authors.affiliation: Department of Aquatic Ecology and Water Quality Management, Wageningen University, P.O. Box 47, NL-6700 AA, Wageningen, The Netherlands.
authors.forename: Jan G M
authors.initials: JG
authors.lastname: Cuppen
authors.affiliation: Department of Aquatic Ecology and Water Quality Management, Wageningen University, P.O. Box 47, NL-6700 AA, Wageningen, The Netherlands.
authors.forename: Edwin T H M
authors.initials: ET
authors.lastname: Peeters
authors.affiliation: South Australian Museum, North Terrace, Adelaide, South Australia, 5000, Australia; School of Earth and Environmental Science, University of Adelaide, Adelaide, South Australia, Australia; School of Biological Sciences, Flinders University of South Australia, Adelaide, South Australia, Australia.
authors.forename: Remko
authors.initials: R
authors.lastname: Leijs
authors.affiliation: Department of Ecology and Environmental Science, University of Umeå, S-901 87, Umeå, Sweden.
authors.forename: Anders N
authors.initials: AN
authors.lastname: Nilsson
mesh_terms: D000818:Animals; D005075:Biological Evolution; D001517:Coleoptera / Q000145:classification* / Q000235:genetics*; D010802:Phylogeny