title: Using simulations to evaluate Mantel-based methods for assessing landscape resistance to gene flow.
abstract: Mantel-based tests have been the primary analytical methods for understanding how landscape features influence observed spatial genetic structure. Simulation studies examining Mantel-based approaches have highlighted major challenges associated with the use of such tests and fueled debate on when the Mantel test is appropriate for landscape genetics studies. We aim to provide some clarity in this debate using spatially explicit, individual-based, genetic simulations to examine the effects of the following on the performance of Mantel-based methods: (1) landscape configuration, (2) spatial genetic nonequilibrium, (3) nonlinear relationships between genetic and cost distances, and (4) correlation among cost distances derived from competing resistance models. Under most conditions, Mantel-based methods performed poorly. Causal modeling identified the true model only 22% of the time. Using relative support and simple Mantel r values boosted performance to approximately 50%. Across all methods, performance increased when landscapes were more fragmented, spatial genetic equilibrium was reached, and the relationship between cost distance and genetic distance was linearized. Performance depended on cost distance correlations among resistance models rather than cell-wise resistance correlations. Given these results, we suggest that the use of Mantel tests with linearized relationships is appropriate for discriminating among resistance models that have cost distance correlations <0.85 with each other for causal modeling, or <0.95 for relative support or simple Mantel r. Because most alternative parameterizations of resistance for the same landscape variable will result in highly correlated cost distances, the use of Mantel test-based methods to fine-tune resistance values will often not be effective.
authors: Department of Environmental Conservation University of Massachusetts Amherst Massachusetts 01003.
authors: Katherine A
authors: KA
authors: Zeller
authors: Department of Fisheries and Wildlife Oregon State University Corvallis Oregon 97331.
authors: Tyler G
authors: TG
authors: Creech
authors: Department of Biology McGill University Montreal Quebec H3A 1B1 Canada.
authors: Katie L
authors: KL
authors: Millette
authors: Department of Fisheries and Wildlife Oregon State University Corvallis Oregon 97331.
authors: Rachel S
authors: RS
authors: Crowhurst
authors: Field Conservation Program Woodland Park Zoo Seattle Washington 98103.
authors: Robert A
authors: RA
authors: Long
authors: Department of Ecology and Evolutionary Biology University of Toronto Mississauga Ontario L5L 1C6 Canada.
authors: Helene H
authors: HH
authors: Wagner
authors: Department of Wildlife Sciences University of Göttingen Büsgenweg 3 37077 Göttingen Germany.
authors: Niko
authors: N
authors: Balkenhol
authors: Division of Biological Sciences University of Montana Missoula Montana 59846.
authors: Erin L
authors: EL
authors: Landguth
keywords: CDPOP; landscape fragmentation; landscape genetics; landscape resistance; simulations