title: Clock gene polymorphism and scheduling of migration: a geolocator study of the barn swallow Hirundo rustica.
abstract: Circannual rhythms often rely on endogenous seasonal photoperiodic timers involving 'clock' genes, and Clock gene polymorphism has been associated to variation in phenology in some bird species. In the long-distance migratory barn swallow Hirundo rustica, individuals bearing the rare Clock allele with the largest number of C-terminal polyglutamine repeats found in this species (Q8) show a delayed reproduction and moult later. We explored the association between Clock polymorphism and migration scheduling, as gauged by light-level geolocators, in two barn swallow populations (Switzerland; Po Plain, Italy). Genetic polymorphism was low: 91% of the 64 individuals tracked year-round were Q7/Q7 homozygotes. We compared the phenology of the rare genotypes with the phenotypic distribution of Q7/Q7 homozygotes within each population. In Switzerland, compared to Q7/Q7, two Q6/Q7 males departed earlier from the wintering grounds and arrived earlier to their colony in spring, while a single Q7/Q8 female was delayed for both phenophases. On the other hand, in the Po Plain, three Q6/Q7 individuals had a similar phenology compared to Q7/Q7. The Swiss data are suggestive for a role of genetic polymorphism at a candidate phenological gene in shaping migration traits, and support the idea that Clock polymorphism underlies phenological variation in birds.
authors.affiliation: Dipartimento di Bioscienze, Università degli Studi di Milano, via Celoria 26, I-20133 Milano, Italy.
authors.forename: Gaia
authors.initials: G
authors.lastname: Bazzi
authors.affiliation: Dipartimento di Scienze dell'Ambiente e del Territorio e di Scienze della Terra (DISAT), Università di Milano-Bicocca, Piazza della Scienza 1, I-20126 Milano, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Ambrosini
authors.affiliation: Dipartimento di Bioscienze, Università degli Studi di Milano, via Celoria 26, I-20133 Milano, Italy.
authors.forename: Manuela
authors.initials: M
authors.lastname: Caprioli
authors.affiliation: Dipartimento di Bioscienze, Università degli Studi di Milano, via Celoria 26, I-20133 Milano, Italy.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Costanzo
authors.affiliation: Swiss Ornithological Institute, Seerose 1, CH-6204 Sempach, Switzerland.
authors.forename: Felix
authors.initials: F
authors.lastname: Liechti
authors.affiliation: Dipartimento di Bioscienze, Università degli Studi di Milano, via Celoria 26, I-20133 Milano, Italy.
authors.forename: Emanuele
authors.initials: E
authors.lastname: Gatti
authors.affiliation: Dipartimento di Bioscienze, Università degli Studi di Milano, via Celoria 26, I-20133 Milano, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Gianfranceschi
authors.affiliation: Dipartimento di Bioscienze, Università degli Studi di Milano, via Celoria 26, I-20133 Milano, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Podofillini
authors.affiliation: Dipartimento di Bioscienze, Università degli Studi di Milano, via Celoria 26, I-20133 Milano, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Romano
authors.affiliation: Dipartimento di Bioscienze, Università degli Studi di Milano, via Celoria 26, I-20133 Milano, Italy.
authors.forename: Maria
authors.initials: M
authors.lastname: Romano
authors.affiliation: 1] Dipartimento di Bioscienze, Università degli Studi di Milano, via Celoria 26, I-20133 Milano, Italy [2] Swiss Ornithological Institute, Seerose 1, CH-6204 Sempach, Switzerland.
authors.forename: Chiara
authors.initials: C
authors.lastname: Scandolara
authors.affiliation: Dipartimento di Bioscienze, Università degli Studi di Milano, via Celoria 26, I-20133 Milano, Italy.
authors.forename: Nicola
authors.initials: N
authors.lastname: Saino
authors.affiliation: Dipartimento di Bioscienze, Università degli Studi di Milano, via Celoria 26, I-20133 Milano, Italy.
authors.forename: Diego
authors.initials: D
authors.lastname: Rubolini
mesh_terms: D000483:Alleles; D025041:Animal Migration / Q000502:physiology*; D000818:Animals; D056926:CLOCK Proteins / Q000235:genetics*; D002940:Circadian Rhythm / Q000235:genetics*; D005260:Female; D005838:Genotype; D007558:Italy; D008297:Male; D011110:Polymorphism, Genetic / Q000235:genetics*; D012098:Reproduction / Q000235:genetics; D012621:Seasons; D046388:Swallows / Q000235:genetics*; D013557:Switzerland
chemical_list: D056926:CLOCK Proteins