title: A forecast for extinction debt in the presence of speciation.
abstract: Predicting biodiversity relaxation following a disturbance is of great importance to conservation biology. Recently-developed models of stochastic community assembly allow us to predict the evolution of communities on the basis of mechanistic processes at the level of individuals. The neutral model of biodiversity, in particular, has provided closed-form solutions for the relaxation of biodiversity in isolated communities (no immigration or speciation). Here, we extend these results by deriving a relaxation curve for a neutral community in which new species are introduced through the mechanism of random fission speciation (RFS). The solution provides simple closed-form expressions for the equilibrium species richness, the relaxation time and the species-individual curve, which are good approximation to the more complicated formulas existing for the same model. The derivation of the relaxation curve is based on the assumption of a broken-stick species-abundance distribution (SAD) as an initial community configuration; yet for commonly observed SADs, the maximum deviation from the curve does not exceed 10%. Importantly, the solution confirms theoretical results and observations showing that the relaxation time increases with community size and thus habitat area. Such simple and analytically tractable models can help crystallize our ideas on the leading factors affecting biodiversity loss.
authors.affiliation: Department of Biological Applications and Technology, University of Ioannina, 45110 Ioannina, Greece. Electronic address: viki_sgard@yahoo.gr.
authors.forename: Vasiliki
authors.initials: V
authors.lastname: Sgardeli
authors.affiliation: Department of Biology, Kyushu University, 744 Motooka Nishi-ku, Fukuoka 819-0395, Japan. Electronic address: yohiwasa@kyushu-u.org.
authors.forename: Yoh
authors.initials: Y
authors.lastname: Iwasa
authors.affiliation: Department of Physics, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece. Electronic address: varvoglis@physics.auth.gr.
authors.forename: Harry
authors.initials: H
authors.lastname: Varvoglis
authors.affiliation: Department of Biological Applications and Technology, University of Ioannina, 45110 Ioannina, Greece. Electronic address: jhalley@cc.uoi.gr.
authors.forename: John M
authors.initials: JM
authors.lastname: Halley
mesh_terms: D000818:Animals; D044822:Biodiversity; D005075:Biological Evolution; D053476:Extinction, Biological; D049810:Genetic Speciation; D006801:Humans; D011157:Population Dynamics
keywords: Extinction rates; Neutral model; Random fission speciation; Relaxation process; Relaxation time