Authors: Alessio Mortelliti Giovanni Amori Luigi Boitani
Publish Date: 2010/04/23
Volume: 163, Issue: 2, Pages: 535-547
Abstract
There is increasing empirical evidence that the quality of habitat patches determined by either habitat degradation or natural heterogeneity in the quality of habitat plays an important role in determining species distribution patterns and in regulating spatial dynamics in fragmented landscapes However to date most of the debate has focused on whether or not to include habitat variables in fragmentation studies and we still lack general conclusions as well as standard and robust research approaches In this paper we show how a weak conceptualization of “patch quality” and the inappropriate choice of target surrogate variables eg density is often used as an indicator of patch quality have mainly produced casespecific results rather than general conclusions We then identify weaknesses in the inclusion of habitat quality measurements within fragmentation studies In particular we focus on 1 the lack of appropriate experimental design outlining how few studies have actually included a gradient of habitat quality in their sample 2 the lack of fundamental information provided eg lack of standard outputs which in turn hampers the possibility of carrying out metaanalyses We finally synthesize available knowledge from empirical studies and highlight the different conceptual frameworks needed for patch occupancy versus patch use studiesAlessio Mortelliti was supported by a grant of the ARP Agenzia Regionale dei Parchi del Lazio to the CNR Institute for Ecosystem Studies while carrying out this work Thanks to two anonymous referees that helped us improve a previous version of this manuscript thanks to Christina Thwaites for language revisionC r is the contribution of a member of the focal subpopulation “r” to the spatially structured population Φ A rr is the apparent survival of adults that remain in the subpopulation r Φ A rs is the apparent survival of adults that emigrate to other subpopulations β r is the number of juveniles per adult Φ j rr is the apparent survival of juveniles that remain the subpopulation r and Φ j rs is the apparent survival of juveniles that emigrate to other subpopulations If C r 1 the focal subpopulation contributes more individuals than it loses via mortality and is a source If C r 1 the focal subpopulation loses more animals to mortality than it contributes and is a sink
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