An Analysis of Continent-Wide Patterns of Sexual Selection in a Passerine Bird

Abstract

Abstract. Patterns of selection are widely believed to differ geographically, causing adaptation to local environmental conditions. However, few studies have investigated patterns of phenotypic selection across large spatial scales. We quantified the intensity of selection on morphology in a monogamous passerine bird, the barn swallow Hirundo rustica, using 6495 adults from 22 populations distributed across Europe and North Africa. According to the classical DarwinFisher mechanism of sexual selection in monogamous species, two important components of fitness due to sexual selection are the advantages that the most attractive males acquire by starting to breed early and their high annual fecundity. We estimated directional selection differentials on tail length (a secondary sexual character) and directional selection gradients after controlling for correlated selection on wing length and tarsus length with respect to these two fitness components. Phenotype and fitness components differed significantly among populations for which estimates were available for more than a single year. Likewise, selection differentials and selection gradients differed significantly among populations for tail length, but not for the other two characters. Sexual selection differentials differed significantly from zero across populations for tail length, particularly in males. Controlling statistically for the effects of age reduced the intensity of selection by 60 to 81%, although corrected and uncorrected estimates were strongly positively correlated. Selection differentials and gradients for tail length were positively correlated between the sexes among populations for selection acting on breeding date, but not for fecundity selection. The intensity of selection with respect to breeding date and fecundity were significantly correlated for tail length across populations. Sexual size dimorphism in tail length was significantly correlated with selection differentials with respect to breeding date for tail length in male barn swallows across populations. These findings suggest that patterns of sexual selection are consistent across large geographical scales, but also that they vary among populations. In addition, geographical patterns of phenotypic selection predict current patterns of phenotypic variation among populations, suggesting that consistent patterns of selection have been present for considerable amounts of time.

Sexual Dimorphism in Melanin Pigmentation, Feather Coloration and Its Heritability in the Barn Swallow (Hirundo rustica)

“…Thus, given what is known about the genetic and physiological machinery behind pheo- and eumelanogenesis and what has been hypothesized about the role of melanin in communication, these results suggest that any socio-sexual role of melanin-based coloration could also differ between geographical populations. This would of course not be surprising given ample evidence for geographical variation in natural and sexual selection regimes among geographical populations ([80]; see [81] and references therein).…”

Viability Is Associated with Melanin-Based Coloration in the Barn Swallow (Hirundo rustica)

“…In this scenario, genetically based color variation may be maintained by contrasting sexual and viability selection. However, it must be emphasized that geographical barn swallow populations have been shown to markedly differ in several aspects of morphology, coloration and behavior, including sexual selection [37], [47], [48], and more information on the fitness correlates of darkness in belly coloration from our study population is required before any conclusion can be drawn. It should also be noted that selection in relation to color may also occur during the first year of life [25], although this hypothesis will be difficult to test owing to practical difficulties set by natal dispersal.…”

Macroautophagy is impaired in old murine brain tissue as well as in senescent human fibroblasts

“…During selective MA specifically ubiquitinated cargo (linked to K-63 polyubiquintin chains) is delivered to the autophagosomal membrane by proteins such as p62 [5]. The initiation of autophagosome formation is a very well-regulated conjunction, among others carried out by Beclin-1-VPS34 and mammalian target of rapamycin complex I (mTORC1) [8]. Particularly MA has been reported to be inhibited by mTORC1 (referred to as mTOR from here on) [9].…”