Carabids (Coleoptera: Carabidae) in a forest patchwork: a connectivity analysis of the Bereg Plain landscape graph
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For many species, one important key to persistence is maintaining connectivity among local populations that allow for dispersal and gene flow. This is probably true for carabid species (Coleoptera:Carabidae) living in the fragmented forests of the Bereg Plain (NE Hungary and W Ukraine). Based on field data, we have drafted a landscape graph of the area representing the habitat network of these species. Graph nodes and links represented two kinds of landscape elements: habitat (forest) patches and corridors, respectively. The quality of habitat patches and corridors were ranked (from low (1) to high (4)), reflecting local population sizes in the case of patches and estimated permeability in the case of corridors. We analysed (1) the positional importance of landscape elements in maintaining the connectivity of the intact network, (2) the effect of inserting hypothetical corridors into the network, (3) the effects of improving the quality of the existing corridors, and (4) how to connect every patch in a cost-effective way. Our results set quantitative priorities for conservation practice by identifying important corridors: what to protect, what to build and what to improve. Several network analytical techniques were used to account for the directed (source-sink) and highly fragmented nature of the landscape graph. We provide conservation priority ranks for the landscape elements and discuss the conditions for the use of particular network indices. Our study could be of extreme relevance, since a new highway is being planned through the area.
KeywordsLandscape graph Reachability Isolation Connectivity Carabidae Hungary Directed graph
We are grateful for Zoltán Peresztegi-Nagy for developing a computer programme for one part of the analysis, András Báldi and Gábor Lövei for useful discussions and three anonymous reviewers for their comments on the manuscript. We thank K. Csepi and G. Lövei for linguistic revision. FJ and TM were supported by grants from the Hungarian Scientific Research Fund (OTKA T 37726 and F 61651, respectively). FJ was also supported by Society in Science: the Branco Weiss Fellowship from ETH Zürich, Switzerland.
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