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

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

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

Barn Swallow Species Complex

t = ; p < Czech Republic North America

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

How is phenotypic variation within populations influenced by genetic and environmental variation? How can we use this information to better understand reproductive isolation and the process of speciation?

Phenotypic Variation Genetic Variation Environmenta l Variation Unmeasured Variation Animal Model y i = µ + a i + e i + ε i a i = breeding value ei = environmental value

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

Nests paired by: -Hatch date -Brood size (± 1) Swapped 90 nests (45 nest pairs) 56 control nests After Predation and Mortality: 494 Offspring; 107 Mothers; 96 Fathers 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; 60 Mothers; 59 Fathers

Multivariate Animal Model Response Variables (standardized to the mean): 1.Brightness 2.Hue 3.Red Chroma Random effects 1.Pedigree – genetic variance 2.Nest ID – environmental variance

BrightnessHueChroma Heritability (0.102 – 0.325)(0.106 – 0.376)(0.093 – 0.285) Environmental Influence (0.120 – 0.280)(0.222 – 0.426)(0.110 – 0.266) Extra-Pair Paternity: ~35-40% (95% Bayesian Credible Interval – BCI) Colorado

Environmental Context e 2 ≅ 0.2 – 0.3 Female Preference h 2 ≅ 0.2 – 0.25

BrightnessHueChroma Heritability ( )( )( ) Environmental Influence ( )( )( ) Extra-Pair Paternity: ~16% (95% Bayesian Credible Interval – BCI) Czech Republic

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

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

ColoradoCzech Republic Brightness & Red Chroma ( ) Brightness & Hue ( – 0.370) Red Chroma & Hue ( ) Brightness & Red Chroma ( ) Brightness & Hue ( – 0.495) Red Chroma & Hue ( – 0.327)

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

G-Matrix Comparison Lower BCIUpper BCI Observed Randomize d

Phenotypic Variation Environmental Variation Genetic Variation No divergence in covariance structure ? Selection A1 A2 A3A6 A5 A7 A9 A6A3 A8

Conclusions Melanin-based color variation is affected by environmental variation Divergent selection may have driven phenotypic divergence among barn swallow subspecies Photo: Matt Wilkins

Future Directions Identify pigmentation genes that associate with color variation within and across populations Identify specific environmental factors that influence coloration (Amanda Hund – Session 3C_306C – Visual Signaling on Monday)

Collaborators: Tomáš Albrecht 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 Undergraduate Assistants Site Owners Acknowledgments

Total Amount of pigment Ratio of pigment type

CO results - Social BrightnessHueChroma VAVA ( )( )( ) VEVE ( )( )( ) VRVR ( )( )( ) VPVP ( )( )( )

CO results - Genetic BrightnessHueChroma VAVA (0.131 – 0.567)(0.129 – 0.473)(0.121 – 0.573) VEVE (0.144 – 0.401)(0.135 – 0.361)(0.144 – 0.396) VRVR (0.313 – 0.627)(0.426 – 0.723)(0.293 – 0.615) VPVP (0.942 – 1.238)(0.977 – 1.263)(0.939 – 1.239)

CR results - social BrightnessHueChroma VAVA ( )( )( ) VEVE ( )( )( ) VRVR ( )( )( ) VPVP ( )( )( )

CR results - genetic BrightnessHueChroma VAVA ( )( )( ) VEVE ( )( )( ) VRVR ( )( )( ) VPVP ( )( )( )