Lifetime reproductive success, selection on lifespan, and multiple sexual ornaments in male European barn swallows

Abstract

Natural and sexual selection arise when individual fitness varies according to focal traits. Extra-pair paternities (EPPs) can affect the intensity of selection by influencing variance in fitness among individuals. Studies of selection require that individual fitness is estimated using proxies of lifetime reproductive success (LRS). However, estimating LRS is difficult in large, open populations where EPPs cause reallocation of biological paternity. Here, we used extensive field sampling to estimate LRS in a population of barn swallows (Hirundo rustica) to estimate selection on lifespan and ornamental traits of males. We found selection on lifespan mediated both by within- and extra-pair fertilization success and selection on tail length mediated by within- but not extra-pair fertilization success. In addition, we found selection on tail white spots via extra-pair fertilization success after controlling for selection on other traits. These results were not confounded by factors that hamper studies of LRS, including nonexhaustive sampling of offspring and biased sampling of males. Hence, natural and sexual selection mediated by LRS operates on lifespan, tail length, and size of the tail white spots in barn swallows.

Selection on multiple sexual signals in two Central and Eastern European populations of the barn swallow

“…Consistent with this prediction, we found that two putative secondary sexual traits, tail length and ventral coloration, in Czech and Romanian barn swallow populations were not significantly correlated, the magnitude of trait expression differed between the two populations, as did patterns of selection. In support of the prediction for the role of tail length in sexual selection in H. r. rustica, we found significant directional linear selection on this trait for both populations, in concordance with previous findings on other European populations (Costanzo, Ambrosini, Caprioli, Gatti, Parolini, Canova et al, ; Møller et al, ). However, the magnitude of selection on tail length differed between populations, age groups, and sexes: Selection was stronger in first‐time breeders than in experienced birds and in males than in females in the Romanian population, while differences between age groups and sexes were slight in Czech birds (Tables and ).…”

“…These results are consistent with what has been found in an Italian population of barn swallows (Parolini et al, ; Saino, Romano, Rubolini, Teplitsky, et al, ). In this particular Italian population, darker males had significantly higher seasonal reproductive success, but coloration did not predict the lifetime reproductive success of the birds (Costanzo, Ambrosini, Caprioli, Gatti, Parolini, Canova et al, ; Parolini et al, ). These findings show that ventral coloration may give some advantages to the bearer over the breeding season, but the underlying mechanism of this relationship is not clarified (see (Costanzo, Ambrosini, Caprioli, Gatti, Parolini, Romano et al, ).…”

“…On the same Italian population, darker males had significantly higher seasonal reproductive success (Parolini et al, ), and survival was higher in males with relatively higher eumelanin‐to‐pheomelanin ratio of ventral body feathers (Saino, Romano, Rubolini, Ambrosini, et al, ). However, ventral coloration did not predict the lifetime reproductive success of these birds (Costanzo, Ambrosini, Caprioli, Gatti, Parolini, Canova et al, ). It appears that sexual selection acts on the ventral coloration of females as well, because females with higher UV reflectance of their ventral plumage coloration were more promiscuous and the proportion of male offspring in a nest increased with maternal plumage darkness (Costanzo, Ambrosini, Caprioli, Gatti, Parolini, Romano et al, ; Romano et al, ).…”

Telomere length is reflected by plumage coloration and predicts seasonal reproductive success in the barn swallow

“…Previous studies of other barn swallow subspecies have documented a relationship between male coloration and annual breeding success, with darker males producing a larger number of biological offspring per breeding season (Safran & McGraw, ; Vortman, Lotem, Dor, Lovette, & Safran, ; Wilkins et al., ; Romano, Costanzo, Rubolini, Saino & Møller, ). In the European subspecies, the role of plumage coloration in sexual selection has not been fully elucidated (Romano et al, , , ; Costanzo, Ambrosini, et al, ). If TL correlates with coloration and predicts breeding success, we also expected coloration to predict seasonal reproductive success, with darker individuals showing higher success.…”

Inter-generational resemblance of methylation levels at circadian genes and associations with phenology in the barn swallow

“…the males that attend the offspring) are also the genetic fathers of the offspring (hereafter, within-pair offspring, WPO) that they attend; second, families where the parental father is the ‘social’, but not the genetic father (hereafter, ‘social father’) of one or more of the offspring (hereafter, extra-pair offspring, EPO) that they attend. Extra-pair fertilizations, which are common in the barn swallow 41,42 , afford an opportunity to get an insight into the contribution of different mechanisms of parent-offspring resemblance in methylation states, and we therefore subjected the 65 sampled offspring to genetic parentage tests. If genetic father-WPO resemblance in methylation is stronger than social father-EPO resemblance, a mechanism of inheritance mediated by the paternal germline or via non-genetic sperm and seminal fluid constituents can be invoked.…”