The role of demography in the evolution of breeding strategies

Abstract

The five chapters of this thesis all focus on the role of demography in the evolution of breeding strategies. In the first chapter we explore the role of the adult sex ratio (ASR) in the evolution of mate-guarding duration. Our two models predict male guarding duration to increase with decreasing female availability and increasing number of male competitors. However, with a male biased ASR there are several factors, such as guarding inefficiency and incomplete last male sperm precedence, that prevent the mating system from switching to male monogamy. The second chapter adresses a situation where females have a larger effect on population dynamics than males (i.e. female demographic dominance). This occurs when female fecundity is relatively independent of male abundance, while male reproduction is proportional to female abundance. Our two simulation models combine dispersal evolution with local adaption subjected to intralocus conflict and environmentally driven sex ratio biases, respectively. Our proof of principle demonstrates that trait evolution is dominated by environments with a higher abundance of females, although this does not imply that all measures of population performance are improved. In the third chapter we focus on the role of owning a breeding territory for different rates of natal and breeding dispersal. For this we investigate the interplay of the asset-protection principle and the multiplier effect. Our simulation model is set in habitats of spatially varying quality and individuals express dispersal rates based on their life history stage, sex and quality of their habitat. Breeders can evolve high dispersal rates but only if better opportunities are readily available. Non-breeders evolve dispersal mostly in response to competition. For the fourth chapter we stay with the importance of breeding territories, however we shift our focus to its role as a selective force for early arrival in migratory species. We investigate the role of predation upon arrival at breeding grounds as a selective force for later arrival. We use two models, a semi-analytic and a simulation model, to show that predation upon arrival can select for later arrival however in most cases it also selects for highly synchronous arrival. This high synchrony results in predator satiation and provides safety in numbers. In chapter 5 we use meta-analyses to investigate three questions related to paternity protection in birds. In socially monogamous birds males are presumed to protect their paternity with mate-guarding or frequent copulation. We first test if these presumed paternity protection behaviors protect a male’s paternity. Our second question focusses on the role of male quality, if females prefer high quality males to sire their offspring then does this mean that high quality males can protect their paternity less? The third question is based on the expected relationship between paternal care and paternity protection behaviors (as a proxy for certainty of paternity), i.e. males are expected to provide more care for offspring they ‘think’ they have sired. We combine the results of these meta-analyses with the extensive literature on topics frequently associated with paternity in an attempt to provide a general overview.