Photoperiodic responses are major factors entraining circannual life-cycles, functioning to adaptively synchronize annual routines to seasonal fluctuations in ecological conditions. delay molt in Africa. Though based on a limited number of is involved in the photoperiodic control of both molt and breeding, potentially also via reciprocal carry-over effects. If confirmed in species with higher polymorphism, present results may have far-reaching consequences for the study of photoperiodic control of molt and expression of annual routines. gene, Hirundo rustica, Migration, Sexual dimorphism, Molecular sexing Introduction Organisms are selected to match the timing of life stages to seasonal variation in NVP-BEP800 ecological conditions. A major extrinsic driver of synchronization of phenological or physiological events, such as breeding or migration, to seasonal fluctuations in environmental conditions is variation in photoperiod (Gwinner, 1986; Beacham & Murray, 1988; Bradshaw & Holzapfel, 2001; Dawson et al., 2001; Goldman, NVP-BEP800 2001; Gwinner, 2003). Rhythmicity of circannual life-cycles can be enforced by so called circadian clocks that can sense variation in day/night cycles and cause shifts in physiology and behaviour by triggering a NVP-BEP800 cascade of photoperiodic responses (Darlington et al., 1998; Yasuo et al., 2003; Kyriacou et al., 2007). Genes responsible for regulation of such circadian biochemical oscillators are phylogenetically highly conserved and their mechanism of action has been well described (Bell-Pedersen et al., 2005). genes, in particular, seem to play a role in the photoperiodic responses of diverse invertebrates and vertebrates, including migration Rabbit Polyclonal to BLNK (phospho-Tyr84). in fish and breeding in birds (DeBruyne et al., 2006; OMalley & Banks, 2008; Liedvogel et al., 2009), but the studies that have investigated photoperiodism in relation to in the wild are still sparse. A domain of genes which is functionally relevant to photoperiodism is the carboxyl-terminal polyglutamine repeat (Poly-Q), as the number of Poly-Q repeats is known to affect circadian rhythms in mice (Gekakis et al., 1998; Vitaterna et al., 2006). In the Chinhook salmon (allele frequencies parallels that of spring migration phenology (OMalley & Banks, 2008; OMalley, Ford & Hard, 2010). Among birds, timing of breeding of the resident/short-distance migratory blue tit (polymorphism and a cline in genotype (Caprioli et al., 2012). In all these instances, late phenology has been found to be associated with an increase in the number of Poly-Q terminal repeats. However, other studies of birds (e.g.?on great tits, and no relationship between and breeding phenology (Liedvogel & Sheldon, 2010; Dor et al., 2012). As huge variation in polymorphism exists even among closely related species (e.g.?swallow; blue tit and great tit) (Liedvogel et al., 2009; Liedvogel & Sheldon, 2010; Caprioli et al., 2012; Dor et al., 2012), difficulties in identifying an association between phenology and may in some species stem from rarity of phenologically deviant, potentially counter-selected genotypes, in combination with large environmental noise in breeding phenological data. It has been suggested that photoperiod may have no or minor role in synchronizing circannual rhythms at the tropics where limited oscillations in photoperiod occur through the year (e.g. Miller, 1965; Cockrem, 1995; see Hau, Wikelski & Wingfield, 1998). On the other hand, even minor changes in photoperiod can be sensed by tropical birds and cause for example gonadal maturation (Hau, Wikelski & Wingfield, 1998; see also Burns, 1985; Wayne & Rissman, 1991 for effects of tropical photoperiod on other vertebrates), suggesting that photoperiod can act as a of circannual rhythms also at low latitudes. In addition, at the tropics information from daytime light intensity may be integrated with that of daylength or time of sunrise and sunset to serve as a circannual (Gwinner & Scheuerlein, 1998; Gwinner, 2003; Goymann et al., 2012; see also Bentley et al., 1998). However, we are aware of no study where the association between and photoperiodic events has been analyzed at the tropics in vertebrates. Annual life-cycles are often cadenced by a regular succession of fundamental activities which can be reciprocally constrained by time and/or resource limitation (McNamara & Houston, 2008). The evolution and expression of individual photoperiodic traits therefore occur under.