Variation in reproductive success (skew) is required for change in trait/allelic frequencies in a population resulting in evolution. Classically, processes generating this reproductive skew have majorly been studied under the lens of sexual selection. The Darwinian-Bateman paradigm of sexual selection suggests that individuals try to maximise their reproductive success through increased mating opportunities, and difference in gametic investment determines investment in multiple matings. Thus, sexual selection studies have primarily focused on reproductive skew in males, under the assumption that female investment in reproductive success is limited and individuals have relatively uniform number of offspring. In the past 35 years, however, evidence of reproductive skew in females has been found in some species, followed by multiple hypotheses proposed explaining said skew. Multiple researchers suggest that female skew is driven by access to resources rather than sexual processes, but there is still a dearth of quantitative studies. This thesis aims to fill the gap in female reproductive skew studies by looking at the pattern and evolutionary processes generating this skew through a phylogenetic meta-analytic approach.

In the first chapter, we will broadly identify the pattern of reproductive skew in females across the major animal classes and estimate the relative significance of classical sexual selection processes like intrasexual competition and mate choice compared to non-sexual selection (ecology, life history) variables.

Sociality determines the ability of individuals to monopolize resources, avoid predation, and gain access to mates. Reviews have thus partly attributed the ability to reproduce to sociality & social processes in case of females. In the second chapter, we focus specifically on the role of intraspecific social interactions in shaping the skew across taxa.

In the third chapter, we move from large-scale cross-taxa studies to longitudinal studies of individual species. We aim to tease apart the relative importance of viability, sexual and fecundity selection processes across the lifetime of individual females. We will further compare the variation in different fitness components across lifetime in these studies to the cross-taxa pattern observed in the previous two chapters.

This thesis will be one of the first broad-scale quantitative studies to investigate the reproductive skew and selection potential in females, filling the gap left by the classical sexual selection paradigm.