title: Defining individual size in the model filamentous fungus Neurospora crassa.
abstract: It is challenging to apply the tenets of individuality to filamentous fungi: a fungal mycelium can contain millions of genetically diverse but totipotent nuclei, each capable of founding new mycelia. Moreover, a single mycelium can potentially stretch over kilometres, and it is unlikely that its distant parts share resources or have the same fitness. Here, we directly measure how a single mycelium of the model ascomycete Neurospora crassa is patterned into reproductive units (RUs), meaning subpopulations of nuclei that propagate together as spores, and function as reproductive individuals. The density of RUs is sensitive to the geometry of growth; we detected 50-fold smaller RUs when mycelia had expanding frontiers than when they were constrained to grow in one direction only. RUs fragmented further when the mycelial network was perturbed. In mycelia with expanding frontiers, RU composition was strongly influenced by the distribution of genotypes early in development. Our results provide a concept of fungal individuality that is directly connected to reproductive potential, and therefore to theories of how fungal individuals adapt and evolve over time. Our data show that the size of reproductive individuals is a dynamic and environment-dependent property, even within apparently totally connected fungal mycelia.
authors.affiliation: Department of Mathematics, University of California Los Angeles, Los Angeles, CA 90095-1555, USA.
authors.forename: Linda
authors.initials: L
authors.lastname: Ma
authors.affiliation: Department of Mathematics, University of California Los Angeles, Los Angeles, CA 90095-1555, USA.
authors.forename: Boya
authors.initials: B
authors.lastname: Song
authors.affiliation: Department of Mathematics, University of California Los Angeles, Los Angeles, CA 90095-1555, USA.
authors.forename: Thomas
authors.initials: T
authors.lastname: Curran
authors.affiliation: Department of Mathematics, University of California Los Angeles, Los Angeles, CA 90095-1555, USA.
authors.forename: Nhu
authors.initials: N
authors.lastname: Phong
authors.affiliation: Department of Mechanical and Aerospace Engineering, New York University Tandon School of Engineering, Brooklyn, NY 11201, USA.
authors.forename: Emilie
authors.initials: E
authors.lastname: Dressaire
authors.affiliation: Department of Mathematics, University of California Los Angeles, Los Angeles, CA 90095-1555, USA Department of Biomathematics, University of California Los Angeles, Los Angeles, CA 90095-1555, USA mroper@math.ucla.edu.
authors.forename: Marcus
authors.initials: M
authors.lastname: Roper
mesh_terms: D014644:Genetic Variation; D025282:Mycelium / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D009492:Neurospora crassa / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D012098:Reproduction
keywords: chimaerism; fungal biology; individuality; unit of selection