Landscape Ecology

, Volume 27, Issue 2, pp 281–290 | Cite as

Connectivity providers for semi-aquatic vertebrates: the case of the endangered otter in Italy

  • Maria Laura Carranza
  • Evelina D’Alessandro
  • Santiago Saura
  • Anna Loy
Research Article


Modeling habitat connectivity for conservation of semi-aquatic vertebrates is a particularly challenging task, due to the fine-scale and linear distribution of riverine habitats and to the capacity of species to move both on freshwater and terrestrial realms. We showed how the integrated analytical framework provided by the habitat availability (reachability) metrics and their fractions can be used to effectively evaluate the distinctive roles and contributions of both habitat patches (aquatic and riparian) and linkage areas (permeable land matrix) to the connectivity and functioning of a complex system composed of multiple river catchments. Analysis focused on the Eurasian otter (Lutra lutra L.), one of the most endangered mammals in Italy. We developed a network connectivity model based on suitable otter habitats and multiple least-cost paths between catchments. A graph analytical approach was used to identify critical nodes and links for the potential expansion and long-term viability of the species in the region. Our results showed that few basins concentrate most of the importance for sustaining the overall habitat connectivity, due to the extension of suitable habitats they contain, their strong connections with other basins, and their importance as stepping stones that uphold ecological fluxes between otherwise weakly connected habitats. The potential contribution of each basin to enhance the dispersal and expansion of otters in the area strongly depended on the key functional paths (sequences of links and nodes) among the catchments. We identified vacant basins that could be colonized by otters in the near future, and connecting areas in the intermediate matrix that might be preferentially used to conduct and promote dispersal movements and gene flow in the area. The novel approach here adopted could be easily extended to other semiaquatic species and catchment systems, offering a management strategy to preserve the hydrographic network as an integrated system, as well as a joint evaluation of the role of both the river courses and the matrix in between in a single landscape model.


Functional connectivity Graph theory Habitat suitability models Dendritic networks Least-cost modeling Probability of connectivity Matrix permeability Riverscapes 



The research was funded by the Italian Ministry of Environment (project ‘Rete Ecologica della Lontra—Fase 1′). Part of the research was developed during a PhD visiting period in the University of Lleida funded by the University of Molise. Support was also provided by the DECOFOR project (AGL2009-07140/FOR). We also thank the editor and two anonymous reviewers for helpful comments on the manuscript.


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Copyright information

© Springer Science+Business Media B.V. 2011

Authors and Affiliations

  • Maria Laura Carranza
    • 1
  • Evelina D’Alessandro
    • 1
  • Santiago Saura
    • 2
  • Anna Loy
    • 1
  1. 1.Environmetrics Laboratory, Department STATUniversity of MolisePescheItaly
  2. 2.ETSI Montes, Polytechnic University of MadridCiudad Universitaria s/nMadridSpain

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