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Source-sink status of small and large wetland fragments and growth rate of a population network


Pasinelli, G; Runge, J P; Schiegg, K (2011). Source-sink status of small and large wetland fragments and growth rate of a population network. In: Liu, J; Hull, V; Morzillo, A T; Wiens, J A. Sources, Sinks and Sustainability. England: Cambridge University Press, 216-238.

Abstract

Many organisms persist in populations that are spatially structured by
human-induced loss and fragmentation of their native habitats. Despite
this, the demographic contributions of local populations to a population
network and to the growth rate of such a network are still largely unexplored.
Using data on individually marked young and adult female reed
buntings ( Emberiza schoeniclus ) from 21 local populations studied over six
years in northeastern Switzerland , we examined the source—sink status
of small and large local populations with recently developed metrics. We
hypothesized that including emigration to the population network (the
C r metric) would classify more local populations as sources than when
only focusing on the ability of local populations to maintain themselves
(the Rr metric). We further tested the hypothesis that the relative contribution
of small and large local populations to the population network
does not differ. The inclusion of emigration to the population network
resulted in significantly higher values than when only considering the
contribution of local populations to themselves, the difference between
the metrics averaging 30%. Despite this, most local populations in our
study turned out to be sinks (C r value <1), suggesting that substantial
immigration is required for maintaining local populations as well as
the entire population network (growth rate of network always <1). Both
large and small populations contributed equally to the population network.
We conclude that (a) the source—sink status of local populations is
more comprehensively described by metrics including emigration (such
as C r ) than by metrics focusing on processes within local populations (such as Rr ); (b) the network of local populations studied here is not
viable without immigration; and (c) small local populations can be as
valuable as large local populations in their contribution to a population
network.

Abstract

Many organisms persist in populations that are spatially structured by
human-induced loss and fragmentation of their native habitats. Despite
this, the demographic contributions of local populations to a population
network and to the growth rate of such a network are still largely unexplored.
Using data on individually marked young and adult female reed
buntings ( Emberiza schoeniclus ) from 21 local populations studied over six
years in northeastern Switzerland , we examined the source—sink status
of small and large local populations with recently developed metrics. We
hypothesized that including emigration to the population network (the
C r metric) would classify more local populations as sources than when
only focusing on the ability of local populations to maintain themselves
(the Rr metric). We further tested the hypothesis that the relative contribution
of small and large local populations to the population network
does not differ. The inclusion of emigration to the population network
resulted in significantly higher values than when only considering the
contribution of local populations to themselves, the difference between
the metrics averaging 30%. Despite this, most local populations in our
study turned out to be sinks (C r value <1), suggesting that substantial
immigration is required for maintaining local populations as well as
the entire population network (growth rate of network always <1). Both
large and small populations contributed equally to the population network.
We conclude that (a) the source—sink status of local populations is
more comprehensively described by metrics including emigration (such
as C r ) than by metrics focusing on processes within local populations (such as Rr ); (b) the network of local populations studied here is not
viable without immigration; and (c) small local populations can be as
valuable as large local populations in their contribution to a population
network.

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Additional indexing

Item Type:Book Section, refereed, original work
Communities & Collections:07 Faculty of Science > Institute of Evolutionary Biology and Environmental Studies
Dewey Decimal Classification:570 Life sciences; biology
590 Animals (Zoology)
Language:English
Date:2011
Deposited On:03 Aug 2011 13:22
Last Modified:05 Apr 2016 14:58
Publisher:Cambridge University Press
Series Name:Cambridge Studies in Landscape Ecology
Number:10
ISBN:978-0-521-19947-6
Related URLs:http://www.cambridge.org/us/knowledge/isbn/item6227676/Sources, Sinks and Sustainability/

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