Effects of the Landscape on Gene Flow and Connectivity of Boreal Toads

1. Effects of the Landscape on Gene Flow and Connectivity of Boreal Toads Jennifer Moore, Julie Nielsen, David Tallmon, Sanjay Pyare University of Alaska Southeast

2. Landscapes have profound effects on species ecology

3. Landscape genetics Landscape ecology + population genetics • Aims to quantify the effects of the landscape on microevolutionary processes • Cryptic boundaries • Secondary contact among previously isolated pops • Hypothesis driven • Novel individual-based methods

4. Landscape genetics Two key steps: • Detect genetic discontinuities • Correlate these with landscape and environmental features

5. Amphibians • Good models for studies of connectivity • Function as metapopulations • Patchy distributions = limited connectivity • Population dynamics difficult to understand with traditional ecological methods • High population stochasticity

6. Boreal toads • Widespread • IUCN listed as near threatened • Status in Alaska? • northern range margin

7. Boreal toads • Pond breeding, but variable habitat and climate tolerance • Capable of long distance movements • High breeding site fidelity Highly differentiated? Strongly affected by the landscape?

8. Study sites Admiralty Island Haines

9. Hypotheses • H1: Isolation by distance • Euclidean distance • H2-n: Isolation by landscape resistance • Habitat structure (x 5) • Insolation • Rugosity • Saltwater • Permanent snow and ice • Roads (Haines only) Genetic distance Geographic distance

10. Methods • Sample breeding populations • Amplify microsatellites • Calculate genetic distance (Fst) • Generate GIS models, calculate geographic distances • Correlate pairwise genetic with pairwise geographic distance (Mantel tests)

11. Geographic distance Least cost paths Circuit theory Distance that incorporates multiple potential paths of least resistance • Single path of least resistance Mcrae et al. 2008

12. Wolverine gene flow McRae and Beir 2007, PNAS Circuit theory outperforms traditional methods Circuitscape software

13. Sample locations + resistance surface = Circuitscape current map

14. Results Toad populations moderately differentiated on a small scale • Mean pairwiseFst ANM = 0.061, 0.008 - 0.122 HNS = 0.053, 0.006 – 0.143 • Mean pairwise Euclidean distance ANM = 14.5 km, 0.33-45 km HNS = 11.4 km, 0.11-50 km

15. Small effective population sizes (Ne)

16. Permanent snow/ice strongest single factor model

17. Permanent snow and ice affects genetic connectivity R = 0.59

18. Summary and conclusions • Limited gene flow, small scale differentiation • Small Ne for many populations • Gene flow strongly affected by permanent snow/ice • Differs from other parts of range • Barrier due to physiological/thermal limits

19. Summary and conclusions • Impacts of climate change? Glaciers, permanent snow and ice Toad connectivity? =

20. Future directions • Improve model fit • Combine surfaces, multiple parameters • Compare methods: least cost path vs. circuit theory • Broad-scale phylogeographic analysis • Do patterns hold true at different scales?

21. Thanks • NSF Alaska EPSCoR • ADF&G Non Game program • USFS • USGS • Emma Caragano, Ray Slayton, Tim Shields, Kim Obermeyer, Karin McCoy, Colin Shanley, Iris Shields, Robbie Piehl, Lance Lerum, Brett Addis, Cat Frock, Dave Moore