title: Patterns of diversity in soft-bodied meiofauna: dispersal ability and body size matter.
abstract: BACKGROUND
  Biogeographical and macroecological principles are derived from patterns of distribution in large organisms, whereas microscopic ones have often been considered uninteresting, because of their supposed wide distribution. Here, after reporting the results of an intensive faunistic survey of marine microscopic animals (meiofauna) in Northern Sardinia, we test for the effect of body size, dispersal ability, and habitat features on the patterns of distribution of several groups.
  
  
  RESULTS
  As a dataset we use the results of a workshop held at La Maddalena (Sardinia, Italy) in September 2010, aimed at studying selected taxa of soft-bodied meiofauna (Acoela, Annelida, Gastrotricha, Nemertodermatida, Platyhelminthes and Rotifera), in conjunction with data on the same taxa obtained during a previous workshop hosted at Tjärnö (Western Sweden) in September 2007. Using linear mixed effects models and model averaging while accounting for sampling bias and potential pseudoreplication, we found evidence that: (1) meiofaunal groups with more restricted distribution are the ones with low dispersal potential; (2) meiofaunal groups with higher probability of finding new species for science are the ones with low dispersal potential; (3) the proportion of the global species pool of each meiofaunal group present in each area at the regional scale is negatively related to body size, and positively related to their occurrence in the endobenthic habitat.
  
  
  CONCLUSIONS
  Our macroecological analysis of meiofauna, in the framework of the ubiquity hypothesis for microscopic organisms, indicates that not only body size but mostly dispersal ability and also occurrence in the endobenthic habitat are important correlates of diversity for these understudied animals, with different importance at different spatial scales. Furthermore, since the Western Mediterranean is one of the best-studied areas in the world, the large number of undescribed species (37%) highlights that the census of marine meiofauna is still very far from being complete.
authors.affiliation: Dipartimento di Zoologia e Genetica Evoluzionistica, Università di Sassari, Sassari, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Curini-Galletti
authors.forename: Tom
authors.initials: T
authors.lastname: Artois
authors.forename: Valentina
authors.initials: V
authors.lastname: Delogu
authors.forename: Willem H
authors.initials: WH
authors.lastname: De Smet
authors.forename: Diego
authors.initials: D
authors.lastname: Fontaneto
authors.forename: Ulf
authors.initials: U
authors.lastname: Jondelius
authors.forename: Francesca
authors.initials: F
authors.lastname: Leasi
authors.forename: Alejandro
authors.initials: A
authors.lastname: Martínez
authors.forename: Inga
authors.initials: I
authors.lastname: Meyer-Wachsmuth
authors.forename: Karin Sara
authors.initials: KS
authors.lastname: Nilsson
authors.forename: Paolo
authors.initials: P
authors.lastname: Tongiorgi
authors.forename: Katrine
authors.initials: K
authors.lastname: Worsaae
authors.forename: M Antonio
authors.initials: MA
authors.lastname: Todaro
mesh_terms: D000818:Animals; D049628:Body Size; D007448:Invertebrates / Q000033:anatomy & histology*