Female ornaments

Evolution of female ornaments

In 1995, Fitzpatrick & al. suggested that there is less ornamentation among females than males, because for females any investment in costly ornaments to improve access to fertilisations is made at the expense of their own fecundity. Based on this reasoning, one may expect female ornamentation to only evolve when females are more limited by access to males than by their own egg production. The argument by Fitzpatrick & al. rests on a trade-off between female fecundity and ornamentation (for which there is mixed support in the empirical literature). Still, if we assume there is a trade-off between female fecundity and ornamentation, one would expect female ornamentation to evolve more easily if a successful mating gives the female access to a valuable resource in addition to sperm (i.e. if the display trait is favoured by both natural and sexual selection, rather than sexual selection alone). I address these questions in collaboration with Leigh Simmons, Natasha LeBas, Adam Jones, Jono Henshaw, Luc Bussière, Varpu Pärssinen, and others, using a combination of modeling, phylogenetic methods and meta analysis. 

Several Master students have also done projects related to this theme: Ayushi Mahajan, Anna Waffender, and Beatriz Taboada, working on female ornamentation in sand goby, broadnose pipefish, and straightnose pipefish, respectively (see below):

Function of dark eyes in female sand gobies

Sand gobies are generally considered to have conventional sex roles and consistent with this males show breeding colour during the reproductive season along the anal and first dorsal fins (Kvarnemo 1994; Kvarnemo & al 1995). Yet, females also show a sex-specific colouration related to reproduction. It is a striking black pigmentation around the eyes ("dark eyes") that can be turned on/off quickly. It is only shown by females that carry mature eggs (Olsson & al 2017). Recent and ongoing work with Ayushi Mahajan, Karin Olsson, Helen Sköld, and others is investigating the function of dark eyes: Do they play a role in male mate choice, intra-sexual competition among females, or do they have some other function, for example related to vision? Is the expression of dark eyes affected by the adult sex ratio (ASR)?