title: Sex ratio and sexual dimorphism of three lice species with contrasting prevalence parasitizing the house sparrow.
abstract: Female-biased sex ratio is a common phenomenon in parasites; however, the cause and consequence of the skewed sex ratio is less well known. Here, we studied the difference in sex ratio, a possible mechanism responsible for the development of unbalanced proportion of sexes and its consequences on sexual size dimorphism, between 3 louse species parasitizing the house sparrow Passer domesticus. Philopterus fringillae was more prevalent than Sturnidoecus refractariolus and Brueelia cyclothorax. As expected, the most common species, which was probably least affected by isolation and, hence, inbreeding, was characterized by a balanced sex ratio, whereas the 2 other species with low prevalence were significantly more female biased than expected on the basis of the local mate competition hypothesis. Further, in support of this notion, we found that P. fringillae infrapopulation size significantly, and positively, correlated with the sex ratio. Finally, we found significant differences in sexual dimorphism among the 3 louse species and, as expected, the relative size of males was smallest in species with a more female-biased sex ratio.
authors.affiliation: Evolutionary Ecology Group, Hungarian Department of Biology and Ecology, Babeş-Bolyai University, RO-400006 Cluj Napoca, Clinicilor Street 5-7, Romania.
authors.forename: Péter László
authors.initials: PL
authors.lastname: Pap
authors.forename: Costică
authors.initials: C
authors.lastname: Adam
authors.forename: Csongor István
authors.initials: CI
authors.lastname: Vágási
authors.forename: Zoltán
authors.initials: Z
authors.lastname: Benkő
authors.forename: Orsolya
authors.initials: O
authors.lastname: Vincze
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D016010:Binomial Distribution; D001715:Bird Diseases / Q000453:epidemiology / Q000469:parasitology*; D016009:Chi-Square Distribution; D005241:Feathers / Q000469:parasitology; D005260:Female; D058326:Ischnocera / Q000033:anatomy & histology*; D010373:Lice Infestations / Q000453:epidemiology / Q000469:parasitology / Q000662:veterinary*; D016014:Linear Models; D008297:Male; D016012:Poisson Distribution; D015995:Prevalence; D012383:Romania / Q000453:epidemiology; D012727:Sex Characteristics; D012744:Sex Ratio; D046370:Sparrows / Q000469:parasitology*