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

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

4. Barn Swallow Species Complex

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

6. Count North AmericaCzech Republic

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

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

9. Nests paired by: -Hatch date -Brood size (± 1) Swapped 90 nests (45 nest pairs) 56 control nests After Predation and Mortality: 431 Offspring (211 WPY, 189 EPY, 31?) Site A Nest 1 Site B Nest 1 Summer 2012: COSummer 2013: CZ 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 Random effects Pedigree Nest Origin Nest Reared Phenotypic Variation Genetic Variation Environmental Variation Unmeasured Variation Early Environment Rearing Environment Response Variables Theta Phi r Achieved Brightness

11. (95% Bayesian Credible Interval – BCI) ThetaPhir AchievedBrightness Heritability 0.1630.1610.1650.172 (0.132 - 0.205)(0.133 - 0.205)(0.132 - 0.206)(0.136 - 0.210) Early Environment 0.3730.3520.3280.356 (0.281 - 0.421)(0.281 - 0.427)(0.282 - 0.426)(0.271 - 0.418) Rearing Environment 0.3590.350.347 (0.274 - 0.416)(0.269 - 0.413)(0.273 - 0.417)(0.266 - 0.410) Heritability 0.1490.1530.1490.161 (0.112 - 0.195)(0.111 - 0.197)(0.107 - 0.198)(0.115 - 0.207) Early Environment 0.3540.3670.3520.318 (0.262 - 0.461)(0.262 - 0.46)(0.255 - 0.459)(0.248 - 0.449) Rearing Environment 0.3610.3830.3590.364 (0.27 - 0.463)(0.267 - 0.464)(0.263 - 0.471)(0.266 - 0.467)

12. Environmental Context e 2 ≅ 0.32 - 38 Selection h 2 ≅ 0.15 - 17

13. Population 1 Population 2 h 2 is not directly comparable V A1 /V P1 ≅ V A2 /V P2 Phenotypic Variation Genetic Variation Environmental Variation Phenotypic Variation Genetic Variation Environmental Variation Compare genetic variance- covariance matrices

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

15. Comparative Quantitative Genetics CO 1,1 CO 2,1...CO 1,n... CO m,1 CO m,2...CO m,n CZ 1,1 CZ 2,1...CZ 1,n... CZ m,1 CZ m,2...CZB m,n alpha E1 Observed Randomized No Divergence Aguirre et al Heredity 2014

16. G-Matrix Comparison Lower BCIUpper BCI Observed3.9 x 10 -5 2.67 x 10 -4 Randomized08 x 10 -6 Brightness contributes to this difference more so than other color metrics

17. Phenotypic Variation Environmental Variation Genetic Variation Divergence in covariance structure ? Selection A1 A2 A3A6 A5 A7 A9 A6A3 A8

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. Collaborators: Adela Petrželková Romana Michálková Martina Soudková Olda Tomášek Natália Prekopová Lucie Jančíková Funding: EBIO department CU Graduate School Animal Behavior Society American Ornithologists’ Union American Museum of Natural History Colorado Field Ornithologists Max Joseph Matt Wilkins Liz Scordato David Zonana Iris Levin Undergraduate Assistants Site Owners Acknowledgments