title: The hologenome concept: we need to incorporate function.
abstract: Are we in the midst of a paradigm change in biology and have animals and plants lost their individuality, i.e., are even so-called 'typical' organisms no longer organisms in their own right? Is the study of the holobiont-host plus its symbiotic microorganisms-no longer optional, but rather an obligatory path that must be taken for a comprehensive understanding of the ecology and evolution of the individual components that make up a holobiont? Or are associated microbes merely a component of their host's environment, and the holobiont concept is just a beautiful idea that does not add much or anything to our understanding of evolution? This article explores different aspects of the concept of the holobiont. We focus on the aspect of functional integration, a central holobiont property, which is only rarely considered thoroughly. We conclude that the holobiont comes in degrees, i.e., we regard the property of being a holobiont as a continuous trait that we term holobiontness, and that holobiontness is differentiated in several dimensions. Although the holobiont represents yet another level of selection (different from classical individual or group selection because it acts on a system that is composed of multiple species), it depends on the grade of functional integration whether or not the holobiont concept helps to cast light on the various degrees of interactions between symbiotic partners.
authors.affiliation: Institute for Evolution and Biodiversity, University of Münster, Hüfferstraße 1, 48149, Münster, Germany. francesco.catania@uni-muenster.de.|Münster Graduate School of Evolution, University of Münster, Hüfferstraße 1a, 48149, Münster, Germany. francesco.catania@uni-muenster.de.
authors.forename: Francesco
authors.initials: F
authors.lastname: Catania
authors.affiliation: Münster Graduate School of Evolution, University of Münster, Hüfferstraße 1a, 48149, Münster, Germany.|Department of Philosophy and Center for Philosophy of Science, University of Münster, Domplatz 6, 48143, Münster, Germany.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Krohs
authors.affiliation: Münster Graduate School of Evolution, University of Münster, Hüfferstraße 1a, 48149, Münster, Germany.|Institute of Hygiene , University of Münster, Robert-Koch-Strasse 41, 48149, Münster, Germany.
authors.forename: Marco
authors.initials: M
authors.lastname: Chittò
authors.affiliation: Institute for Evolution and Biodiversity, University of Münster, Hüfferstraße 1, 48149, Münster, Germany.|Münster Graduate School of Evolution, University of Münster, Hüfferstraße 1a, 48149, Münster, Germany.
authors.forename: Diana
authors.initials: D
authors.lastname: Ferro
authors.affiliation: Institute for Evolution and Biodiversity, University of Münster, Hüfferstraße 1, 48149, Münster, Germany.|Münster Graduate School of Evolution, University of Münster, Hüfferstraße 1a, 48149, Münster, Germany.
authors.forename: Kevin
authors.initials: K
authors.lastname: Ferro
authors.affiliation: Institute for Evolution and Biodiversity, University of Münster, Hüfferstraße 1, 48149, Münster, Germany.|Münster Graduate School of Evolution, University of Münster, Hüfferstraße 1a, 48149, Münster, Germany.
authors.forename: Gildas
authors.initials: G
authors.lastname: Lepennetier
authors.affiliation: Münster Graduate School of Evolution, University of Münster, Hüfferstraße 1a, 48149, Münster, Germany.|Department of Zoology, Biological Institute, University of Stuttgart, Pfaffenwaldring 57, 70569, Stuttgart, Germany.
authors.forename: Hans-Dieter
authors.initials: HD
authors.lastname: Görtz
authors.affiliation: Münster Graduate School of Evolution, University of Münster, Hüfferstraße 1a, 48149, Münster, Germany.
authors.forename: Rebecca S
authors.initials: RS
authors.lastname: Schreiber
authors.affiliation: Institute for Evolution and Biodiversity, University of Münster, Hüfferstraße 1, 48149, Münster, Germany.|Münster Graduate School of Evolution, University of Münster, Hüfferstraße 1a, 48149, Münster, Germany.
authors.forename: Joachim
authors.initials: J
authors.lastname: Kurtz
authors.affiliation: Institute for Evolution and Biodiversity, University of Münster, Hüfferstraße 1, 48149, Münster, Germany. Juergen.Gadau@asu.edu.|Münster Graduate School of Evolution, University of Münster, Hüfferstraße 1a, 48149, Münster, Germany. Juergen.Gadau@asu.edu.|School of Life Sciences, Arizona State University, Tempe, AZ, 85281, USA. Juergen.Gadau@asu.edu.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Gadau
mesh_terms: D000220:Adaptation, Biological; D000818:Animals; D037421:Anthozoa; D005075:Biological Evolution; D001695:Biology / Q000379:methods*; D004330:Drosophila; D004463:Ecology / Q000379:methods*; D005658:Fungi; D006801:Humans; D010247:Paramecium; D010641:Phenotype; D010944:Plants; D012281:Rickettsia; D013559:Symbiosis
keywords: Evolution; Function; Functional integration; Holobiont; Hologenome; Symbiosis