title: Historical processes constrain patterns in global diatom diversity.
abstract: There is a long-standing belief that microbial organisms have unlimited dispersal capabilities, are therefore ubiquitous, and show weak or absent latitudinal diversity gradients. In contrast, using a global freshwater diatom data set, we show that latitudinal gradients in local and regional genus richness are present and highly asymmetric between both hemispheres. Patterns in regional richness are explained by the degree of isolation of lake districts, while the number of locally coexisting diatom genera is highly constrained by the size of the regional diatom pool, habitat availability, and the connectivity between habitats within lake districts. At regional to global scales, historical factors explain significantly more of the observed geographic patterns in genus richness than do contemporary environmental conditions. Together, these results stress the importance of dispersal and migration in structuring diatom communities at regional to global scales. Our results are consistent with predictions from the theory of island biogeography and metacommunity concepts and likely underlie the strong provinciality and endemism observed in the relatively isolated diatom floras in the Southern Hemisphere.
authors.affiliation: Ghent University, Biology Department, Protistology and Aquatic Ecology, Krijgslaan 281 S8, 9000 Gent, Belgium. Wim.vyverman@Ugent.be
authors.forename: Wim
authors.initials: W
authors.lastname: Vyverman
authors.forename: Elie
authors.initials: E
authors.lastname: Verleyen
authors.forename: Koen
authors.initials: K
authors.lastname: Sabbe
authors.forename: Koenraad
authors.initials: K
authors.lastname: Vanhoutte
authors.forename: Mieke
authors.initials: M
authors.lastname: Sterken
authors.forename: Dominic A
authors.initials: DA
authors.lastname: Hodgson
authors.forename: David G
authors.initials: DG
authors.lastname: Mann
authors.forename: Steve
authors.initials: S
authors.lastname: Juggins
authors.forename: Bart
authors.initials: B
authors.lastname: Van de Vijver
authors.forename: Vivienne
authors.initials: V
authors.lastname: Jones
authors.forename: Roger
authors.initials: R
authors.lastname: Flower
authors.forename: Donna
authors.initials: D
authors.lastname: Roberts
authors.forename: Victor A
authors.initials: VA
authors.lastname: Chepurnov
authors.forename: Cathy
authors.initials: C
authors.lastname: Kilroy
authors.forename: Pieter
authors.initials: P
authors.lastname: Vanormelingen
authors.forename: Aaike
authors.initials: A
authors.lastname: De Wever
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D044822:Biodiversity; D017377:Diatoms / Q000502:physiology*; D017753:Ecosystem; D008386:Marine Biology; D008954:Models, Biological; D011157:Population Dynamics; D013045:Species Specificity; D014867:Water