Different analytical techniques used on the same data set may lead to different conclusions about the existence and strength of genetic structure. Therefore, reliable interpretation of the results from different methods depends on the efficacy and reliability of different statistical methods. In this paper, we evaluated the performance of multiple analytical methods to detect the presence of a linear barrier dividing populations. We were specifically interested in determining if simulation conditions, such as dispersal ability and genetic equilibrium, affect the power of different analytical methods for detecting barriers. We evaluated two boundary detection methods (Monmonier's algorithm and WOMBLING), two spatial Bayesian clustering methods (TESS and GENELAND), an aspatial clustering approach (STRUCTURE), and two recently developed, non-Bayesian clustering methods [PSMIX and discriminant analysis of principal components (DAPC)]. We found that clustering methods had higher success rates than boundary detection methods and also detected the barrier more quickly. All methods detected the barrier more quickly when dispersal was long distance in comparison to short-distance dispersal scenarios. Bayesian clustering methods performed best overall, both in terms of highest success rates and lowest time to barrier detection, with GENELAND showing the highest power. None of the methods suggested a continuous linear barrier when the data were generated under an isolation-by-distance (IBD) model. However, the clustering methods had higher potential for leading to incorrect barrier inferences under IBD unless strict criteria for successful barrier detection were implemented. Based on our findings and those of previous simulation studies, we discuss the utility of different methods for detecting linear barriers to gene flow.

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Richardson's ground squirrels, Spermophilus richardsonii, produce both repetitive and non-repetitive antipredator calls. While many hypotheses have been advanced to explain non-repetitive calls, the function of repetitive calling has received relatively little attention. We presented juvenile Richardson's ground squirrels with a predator model at distances ranging from 1 to 8 m and recorded the subsequent repetitive calls on digital audiotape. The rate of calling was inversely correlated with the distance between the model and the caller, with distance explaining almost 24% of the variation in call rate. To determine whether call recipients use that information, we manipulated the intersyllable latency of a single repetitive call exemplar to form 3 test stimuli varying only in call rate. Across 16 Richardson's ground squirrel colonies to which these calls were broadcast, the proportion of squirrels assuming the highly vigilant, alert posture increased with the rate of the repetitive call presented. Hence, juvenile Richardson's ground squirrels appear to communicate the proximity and presumably the degree of threat posed by potential predators.

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Connectivity conservation is an emergent approach to counteracting landscape fragmentation and enhancing resilience to climate change at local, national, and global scales. While policy that promotes connectivity is advancing, there has been no systematic, evidence-based study that assesses whether connectivity conservation plans (CCPs) resulted in conservation outcomes, and identifies specific plan attributes that may favor successful implementation. To fill this gap, we gathered 263 terrestrial CCPs from around the world, characterized attributes of 109 plans by surveying plan authors, and conducted semistructured interviews with authors and implementers of 77 CCPs. The production of CCPs started around 1990 and has increased markedly in all parts of the world, most notably in the United States (led by NGOs and a few states, with little federal involvement), Europe (led by the EU and national policies and implemented at local levels), and the Republic of South Africa (where national legislation mandates each municipality to map corridors and zone all land by 2020). All of the 109 plans that we examined in detail were followed by implementation actions such as crossing structures, ecological restoration, land purchases or easements, recognition of corridors through zoning or government designation, and public engagement. Interviewees emphasized the importance of initial buy-in from key government stakeholders, stakeholder involvement beyond initial buy-in, minimizing staff turnover, and transparent and repeatable procedures. Our quantitative and qualitative analyses similarly suggested that implementation of a CCP was enhanced by enduring partnerships among stakeholders, continuity of leadership, specific recommendations in the CCP using tools appropriately selected from a large toolbox, the existence of enabling legislation and policy, a transparent and repeatable scientific approach, adequate funding, and public outreach.