Gilbert et al. 1998

Gilbert et al. 1998 - Corridors maintain species richness...

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Corridors maintain species richness in the fragmented landscapes of a microecosystem Francis Gilbert 1 , Andrew Gonzalez 2 and Isabel Evans-Freke 1 1 Department of Life Science, University of Nottingham, Nottingham NG7 2RD, UK ( francis.gilbert@nottingham.ac.uk ) 2 NERC Centre for Population Biology, Silwood Park, Ascot SL5 7PY, UK ( a.gonzalez@ic.ac.uk ) Theory predicts that species richness or single-species populations can be maintained, or at least extinc- tions minimized, by boosting rates of immigration. One possible way of achieving this is by establishing corridors of suitable habitat between reserves. Using moss patches as model microecosystems, we provide here probably the ¢rst ¢eld experimental test of the idea that corridors can reduce the rate of loss of species, and therefore help to maintain species richness. Connecting patches of habitat with corridors did indeed slow the rate of extinction of species, preserving species richness for longer periods of time than in discon- nected habitat patches. The pattern of g -diversity, the cumulative species richness of entire connected systems, is similarly higher than that of fragmented systems, despite the homogenizing e¡ects of movement. Predators are predicted to be more susceptible to fragmentation because of their greater mobility and smaller population sizes. Our data are consistent with this prediction: the proportion of predator species declined signi¢cantly in disconnected as compared with connected treatments. Keywords: conservation; extinction; metapopulations; island biogeography; microcosms; g -diversity 1. INTRODUCTION Conservation biologists frequently advise the establish- ment of corridors to connect isolated reserves (Saunders & Hobbs 1991; Harris & Scheck 1991; 1994; Noss 1994; Harris 1996), based on various theor- etical rationales (Wilson & Willis 1975; Harrison 1994; Lynch et al. 1995; Hanski et al. 1996). The potential cost of creating a connected system of reserves can be huge there are virtually no ¢eld experimental data supporting the major theoretical prediction that species richness is 1991; Simberlo¡ et al . 1992; Hobbs 1992; but see Schmiegelow et al . 1997). Almost the only ¢eld data suggesting that corridors actually work in promoting migration between patches, or slowing the rate of extinc- tion of populations, consist of observations that some organisms do indeed sometimes use corridors (e.g. Saunders & Hobbs 1991; Beier 1993; Haas 1995; Dunning et al. 1995; Downes et al. 1997 a , b ); experimental results are very few, and largely laboratory based (Ims & Sten- seth 1989; Holyoak & Lawlor 1996; Burkey 1997; but see Schmiegelow et al . 1997). In contrast, there has been a great deal of theory associated with the idea that corri- dors between habitat patches might o¡set some of the deleterious e¡ects of habitat fragmentation, principally
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This note was uploaded on 06/04/2011 for the course PCB 4043 taught by Professor Osenberg during the Fall '10 term at University of Florida.

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Gilbert et al. 1998 - Corridors maintain species richness...

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