Using spatial network structure in landscape management and planning: A case study with pond turtles

Connectivity is currently a central issue in landscape management and planning for the conservation of wildlife species occupying scarce habitat patches. In recent years, this issue has increasingly been addressed using methodologies based on spatial network analysis. Here, we propose a hybrid approach based on network analysis tools and empirical habitat suitability models to integrate connectivity on decision-making. The study is focused on a pond system used by the European pond turtle, Emys orbicularis, in a coastal area in southwestern Iberia. The main objective of the study was to illustrate how the output of graph models may be useful to guide habitat management and planning. We assessed ponds according to three complementary structural and functional properties derived from a graph model: (1) pond importance as measured by the sensitivity of the overall connectivity to each pond loss, (2) pond coreness, used to identify the most cohesive pond subsystems and (3) pond betweenness, which measure the importance of ponds as stepping stones. The graph model took into account a resistanceto- movement surface, the maximum traveled distance and a habitat suitability model based on field sampling. Pond importance and coreness were shown to be positively related to occupancy, especially by turtle's youngest age classes, suggesting an important contribution of connectivity attributes for turtle populations. We discuss the ways these pond connectivity-related attributes may be helpful to assist and optimize management efforts for the conservation of the European pond turtle in the study area.

Keywords: Connectivity Emys orbicularis Fragmentation Graph analysis Pond network