Maintenance of genetic variation in sexual ornamentation : role of precopulatory and postcopulatory sexual selection
Year: 2010
Type: dissertation
Abstract: According to the lek paradox, secondary sexual ornaments are under strong directional selection, which should deplete additive genetic variation of these traits. I studied the signalling content of male and female secondary sexual ornaments and the potential factors that may help to maintain the genetic variation of these traits and thus contribute to the resolution of the lek paradox. The results of my thesis are based on three fish species, the Eurasian minnow (Phoxinus phoxinus), the Arctic charr (Salvelinus alpinus) and the whitefish Coregenus lavaretus. In minnows, multiple sexual ornamentation of the males signalled dominance status, courtship activity, parasite resistance and condition of the individuals. Females differed in their ornament-based mating preferences on these traits. In whitefish, the ornamentation of both sexes predicted genetic differences in offspring post-hatching performance, and female ornamentation was positively associated with the size of the offspring and their yolk reserves. However, offspring fitness was also dependent on the parental genetic combination. In the Arctic charr, the intensity of the male breeding colouration was positively associated with their sperm quality (velocity) and potentially also with offspring viability. On the other hand, it could not be ruled out that the cryptic female choice criteria are at least partly inconsistent (non-directional) with the criteria used in pre-copulatory mate choice. My results on charr major histocompatibility complex genes also show that the superiority of the heterozygote individuals may lead to disassortative mating, where females prefer to pair with genetically dissimilar males. All of these factors (varying female preferences, selection on compatible or dissimilar genes and non-directional cryptic female choice) may weaken the directional selection on ornamental traits and thus maintain the genetic variation of the traits. Together, they may provide light on a way towards the resolution of the lek paradox.
Author: Jukka Kekäläinen
Language: English
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W2279700252