title: Neutrality and the response of rare species to environmental variance.
abstract: Neutral models and differential responses of species to environmental heterogeneity offer complementary explanations of species abundance distribution and dynamics. Under what circumstances one model prevails over the other is still a matter of debate. We show that the decay of similarity over time in rocky seashore assemblages of algae and invertebrates sampled over a period of 16 years was consistent with the predictions of a stochastic model of ecological drift at time scales larger than 2 years, but not at time scales between 3 and 24 months when similarity was quantified with an index that reflected changes in abundance of rare species. A field experiment was performed to examine whether assemblages responded neutrally or non-neutrally to changes in temporal variance of disturbance. The experimental results did not reject neutrality, but identified a positive effect of intermediate levels of environmental heterogeneity on the abundance of rare species. This effect translated into a marked decrease in the characteristic time scale of species turnover, highlighting the role of rare species in driving assemblage dynamics in fluctuating environments.
authors.affiliation: Dipartimento di Biologia, Università di Pisa, Pisa, Italy. lbenedetti@biologia.unipi.it
authors.forename: Lisandro
authors.initials: L
authors.lastname: Benedetti-Cecchi
authors.forename: Iacopo
authors.initials: I
authors.lastname: Bertocci
authors.forename: Stefano
authors.initials: S
authors.lastname: Vaselli
authors.forename: Elena
authors.initials: E
authors.lastname: Maggi
authors.forename: Fabio
authors.initials: F
authors.lastname: Bulleri
mesh_terms: D000465:Algorithms; D000818:Animals; D044822:Biodiversity; D003247:Conservation of Natural Resources; D004463:Ecology; D017753:Ecosystem; D004777:Environment; D056890:Eukaryota / Q000235:genetics / Q000502:physiology*; D053476:Extinction, Biological; D008954:Models, Biological; D015233:Models, Statistical; D008962:Models, Theoretical; D011156:Population Density; D011157:Population Dynamics; D013997:Time Factors