Landscape effects on gene flow for a climate‐sensitive montane species, theAmerican pika

Abstract

Climate change is arguably the greatest challenge to conservation of our time. Most vulnerability assessments rely on past and current species distributions to predict future persistence but ignore species' abilities to disperse through landscapes, which may be particularly important in fragmented habitats and crucial for long-term persistence in changing environments. Landscape genetic approaches explore the interactions between landscape features and gene flow and can clarify how organisms move among suitable habitats, but have suffered from methodological uncertainties. We used a landscape genetic approach to determine how landscape and climate-related features influence gene flow for American pikas (Ochotona princeps) in Crater Lake National Park. Pikas are heat intolerant and restricted to cool microclimates; thus, range contractions have been predicted as climate changes. We evaluated the correlation between landscape variables and genetic distance using partial Mantel tests in a causal modelling framework, and used spatially explicit simulations to evaluate methods of model optimization including a novel approach based on relative support and reciprocal causal modelling. We found that gene flow was primarily restricted by topographic relief, water and west-facing aspects, suggesting that physical restrictions related to small body size and mode of locomotion, as well as exposure to relatively high temperatures, limit pika dispersal in this alpine habitat. Our model optimization successfully identified landscape features influencing resistance in the simulated data for this landscape, but underestimated the magnitude of resistance. This is the first landscape genetic study to address the fundamental question of what limits dispersal and gene flow in the American pika.

Landscape-level analysis of mountain goat population connectivity in Washington and southern British Columbia

“…It is therefore difficult to anticipate biases in PCA-based conclusions. Although PCA has not been widely applied in landscape genetic studies, Shirk et al (2012) found consistent causal modeling outcomes when using PCA, proportion of shared alleles and Rousset's a (Rousset 2000), and Castillo et al (2014) found genetic distance based on Bray-Curtis percent dissimilarity (Legendre and Legendre 1998) was similar to PCA genetic distance. We detected significant landscape variables within all three regions despite relatively low sample size, supporting the utility of PCA in landscape genetic studies of continuously distributed species.…”

“…The use of Mantel testing in landscape genetics is controversial (Raufaste and Rousset 2001;Guillot and Rousset 2013;Graves et al 2013), but multiple analyses defend the use of this method within a causal modeling framework (Cushman and Landguth 2010;Shirk et al 2010;Cushman et al 2013b;Castillo et al 2014). Legendre and Fortin (2010) The effect of genetic distance metric choice on causal modeling outcomes has not been evaluated within the field of landscape genetics.…”

“…This could enable the development of a multivariate, movingwindow analysis that better accounts for complex landscape configuration. Recently, Castillo et al (2014) found that causal model outcomes based solely on relative support underestimated the magnitude of resistance compared to reciprocal causal modeling. The application of reciprocal causal modeling could increase confidence in our assigned resistance values.…”

Are American Pikas (<em>Ochotona princeps</em>) in the Canadian Rockies vulnerable to climate change?

“…More recent studies indicate a wide range of dispersal distances including < 20 km (hafner 1993), ≥ 2 km (Zgurski and hik 2012), 2-10 km (Peacock 1997), and 3 km (Merideth 2002). topographic complexity, water barriers, and west-facing slopes were the major factors found to restrict pika dispersal in oregon (Castillo et al 2014).…”

Connectivity of fragmented amphibian populations in a Neotropical landscape

“…When landscapes are complex, organisms perceive contrasts in habitat quality or risk among alternative pathways that may modify movement behavior and dispersal rates . Increased diversity and contrast of land-cover types, may disrupt isolation by distance relationships (Bender & Fahrig 2005, Heidinger et al 2013 making it more informative to analyze effective distances that account for species responses to landscape features , Castillo et al 2014, Soare et al 2014.). Local scale experiments can be used to estimate effective distances by providing information on species-specific responses to landscape features , such as gap crossing behavior (Smith et al 2013) and habitat-specific survival .…”