Experimentally flight-impaired females show higher levels of extra-pair paternity in the pied flycatcherFicedula hypoleuca

Abstract

There is no consensus yet on the reasons why females engage in extra-pair copulations (EPCs). In some species, females have been shown to accrue some indirect benefits, but these effects are not consistent across species and studies. The sexual conflict hypothesis posits that extra-pair paternity (EPP) is the result of strong selection for male pursuit of EPC without real benefits for females. In order to test this hypothesis, we experimentally reduced wing area (reversibly tying together some primary feathers), in a group of pied flycatcher females ( Ficedula hypoleuca ). The manipulation increases wing loading (body mass/wing area), which is negatively associated with flying ability, and thus with the capacity to escape from unwanted copulations. We compared the levels of EPP in this experimental group with those of a group of un-manipulated females. Experimental females almost doubled the proportion of extra-pair young (EPY) with respect to control females. In addition, more males sired EPY in experimental than in control broods containing EPY. These results suggest that in our study population, EPP could be partially a product of female capacity to avoid EPCs. We also discuss the alternative hypothesis that results might be due to an eventual reduction of female attractiveness.

An experimental increase in female mass during the fertile phase leads to higher levels of extra-pair paternity in pied flycatchers Ficedula hypoleuca

“…Our experimental results showed that females of the experimental group displayed a higher condition and wing loading as well as higher EPP levels. These results are in accordance with a previous study reported by Plaza et al (2019), in which handicapped females with a diminished flying ability caused by an increased wing loading, also displayed higher EPP levels. Wing loading has previously been negatively correlated with flying capacity and a reduced manoeuvring ability (van den Hout et al 2010;Salewski et al 2014).…”

“…One interpretation of our results would support the role of sexual conflict in the evolution of EPP. This interpretation would explain the patterns as caused by experimental females being less able to escape from unwanted copulations with extra-pair males, thereby increasing their EPP rate (Plaza et al 2019). This is in agreement with a scenario in which the levels of EPP would be influenced by male coercion instead of female choice (Björklund and Westman 1983) and it is consistent with the results found in a non-experimental study by Moreno et al (2015), where a positive association between wing loading and EPP was reported.…”

“…For instance, if EPCs are the result of male coercion (Westneat and Stewart 2003;Boulton et al 2018), an increase in female mass would result in a higher wing loading which is translated into a reduced flight ability and a diminished capacity of the females to evade unwanted suitors. Indeed, such a negative relation between EPP and female flight ability has been found in some recent studies (Moreno et al 2015;Plaza et al 2019).…”

Extra-pair paternity explains cooperation in a bird species

“…Applied Biosystems MagMAX DNA Isolation Kit (Thermo Fisher Scientific, Waltham) was used to isolate the DNA from tissues and blood, following the manufacturer’s protocol. PCR was done using five microsatellite DNA loci: Fhyu336, Fhyu234, Fhyu304, Fhyu453, and Fhyu448 ( 28 , 43 , 44 ). Applied Biosystems 3130xl Genetic Analyzer (Thermo Fisher Scientific, Waltham) was used to separate the PCR product fragments.…”

Analysis of within-individual variation in extrapair paternity in blue tits (Cyanistes caeruleus) shows low repeatability and little effect of changes in neighborhood

“…Although the majority of species are socially monogamous, copulations outside the social pair bond are widespread and cause varying levels of EPP ( Griffith et al 2002 ; Westneat and Stewart 2003 ; Brouwer and Griffith 2019 ). Extrapair copulations will typically benefit males because they can sire additional offspring, but the adaptive value of extrapair behavior for females remains controversial ( Forstmeier et al 2014 ; Whittingham and Dunn 2016 ; Plaza et al 2019 ). To understand the evolution of EPP and its consequences for sexual selection ( Webster et al 1995 ; Schlicht and Kempenaers 2013 ), we need to find out why males vary in extrapair siring success and why females vary in how many of their eggs are sired by their social mate.…”