Genetic & environmental contributions to a divergent plumage trait in barn swallows

1. Genetic & environmental contributions to a divergent plumage trait in barn swallows Joanna Hubbard, Amanda Hund, Tomas Albrecht, & Rebecca Safran University of Colorado Boulder Ecology & Evolutionary Biology Photo: Matt Wilkins

2. McGraw 2003 Hill 1992 Genetic variation in biosynthetic pathway ♀ ♂ ♂ Brawner et al 2000 Geographic Location Hill 1993

3. Melanin-Based Color Rosenblum et al 2005 Nachman et al 2003 Theron et al 2001

4. Barn Swallow Species Complex

5. Tetrahedral Color Space Stoddard & Prum. 2008. Am Nat

6. North America Czech Republic Count

7. Nestling color is predictive of adult color • Mechanism to maintain color throughout lifetime • Genotype or Developmental Plasticity? Hubbard et al in review

8. Cross-Foster Nestlings Reciprocal exchange Site B Nest 1 Site A Nest 1 Decouple genetic and environmental influences

9. Summer 2012: CO Summer 2013: CZ • Nests paired by: • Hatch date • Brood size (± 1) Site A Nest 1 Site B Nest 1 Swapped 90 nests (45 nest pairs) 56 control nests After Predation and Mortality: 431 Offspring (211 WPY, 189 EPY, 31?) Swapped 60 nests (30 nest pairs) 11 control nests After Predation and Mortality: 283 Offspring (227 WPY, 47 EPY, 9 P)

10. Multivariate Animal Model Response Variables • Theta • Phi • r Achieved • Brightness Genetic Variation Random effects • Pedigree • Nest Origin • Nest Reared Phenotypic Variation Unmeasured Variation Early Environment Environmental Variation Rearing Environment

11. (95% Bayesian Credible Interval – BCI)

12. Environmental Context e2≅ 0.32 - 38 Selection h2≅ 0.15 - 17

13. Genetic Variation Genetic Variation h2is not directly comparable VA1/VP1≅ VA2/VP2 Phenotypic Variation Phenotypic Variation Environmental Variation Environmental Variation Population 1 Population 2 Compare genetic variance-covariance matrices

14. The G-Matrix Trait 2 Breeding Value Trait 2 Breeding Value Trait 1 Breeding Value Trait 1 Breeding Value Breeding Value: how an individual’s genotype shifts it away from the mean phenotype

15. Comparative Quantitative Genetics No Divergence Divergence Observed Randomized alpha E1 E1 Aguirre et al Heredity 2014

16. G-Matrix Comparison Brightness contributes to this difference more so than other color metrics

17. Divergence in covariance structure Phenotypic Variation ? Genetic Variation Environmental Variation A5 A8 Selection A1 A7 A2 A9 A3 A6 A6 A3

18. Conclusions • Melanin-based color variation is affected by environmental variation with low heritability • Divergent selection on plumage brightness will increase phenotypic differences • Divergent selection may have led to current phenotypic differences Photo: Matt Wilkins

19. Future Directions • Identify pigmentation genes that associate with color variation within and across populations • Include additional subspecies and incorporate comparative phylogenetic methods • Identify specific environmental factors that influence coloration

20. Funding: • EBIO department • CU Graduate School • Animal Behavior Society • American Ornithologists’ Union • American Museum of Natural History • Colorado Field Ornithologists Acknowledgments Collaborators: • Adela Petrželková • RomanaMichálková • Martina Soudková • OldaTomášek • NatáliaPrekopová • Lucie Jančíková • Max Joseph • Matt Wilkins • Liz Scordato • David Zonana • Iris Levin • Undergraduate Assistants • Site Owners