Although connectivity tools are numerous and growing steadily, there’s no point in managing for connectivity without the practicality of knowing how to prioritize management decisions. Questions such as which patches are most important, which corridors provide the greatest connectivity, and which type of connectivity is most useful to preserve all need to be answered before on-the-ground actions can be taken. In their recent paper in Landscape Ecology, Creech et al. use bighorn sheep in the Mojave Desert as a system to understand how to prioritize management decisions when different types of connectivity might come into play. Many species, including bighorn sheep, show sex-biased dispersal, which means that demographic connectivity (the potential for recolonization of empty patches) may differ from genetic connectivity (the potential for gene flow). Given these differences, how can managers determine connectivity priorities in a reliable and quantifiable way?
The authors first used resistance-based connectivity models to estimate the cost of dispersal among fragmented bighorn populations and determine which populations were genetically or demographically connected. The novelty of the research emerges when they combine these models with network theory to determine high-priority patches and corridors. Network theory provides numerous metrics that allow the user to quantify the relative importance of patches and corridors. In bighorn sheep, they found much higher connectivity over the short term and long term in the genetic network, which affects management decisions for colonization and gene flow. However, some features were important both genetically and demographically, showing that prioritization need not always be conflicting. Managers need to be explicit in what their goals are for creating connectivity, and if trade-offs are necessary, know where priorities lie. By combining both resistance-based and network-based models, the authors are able to provide a much more useful and objective framework for managers to determine conservation priorities when selecting how to allocate resources for connectivity between fragmented populations.