The evolution of parental care and associated life-history traits in teleost fishes and passerine birds : comparative and experimental approaches

Abstract

Parental care is any form of provisioning that improves offspring survival and can range from brief guarding of young to advanced adaptations such as viviparity. Despite the wide taxonomic spread of care, the evolution of such diversity and its impact on other aspects of species’ life history are not well understood and quantified. Using phylogenetic comparative methods and experimental approaches, I explore how variation in care provision, together with environmental context, affect a range of life-history traits in teleost fishes and passerines. In contrast to birds where advanced and prolonged care dominates, parental care in fishes encompasses a broad spectrum of strategies with varying levels of investment. Chapter 1 provides an overview of research into the evolution of parental care. In Chapter 2, I assess the relative effect of environment and care strategies on variation in offspring size across 1,639 species of marine teleosts. While investment in eggs is driven primarily by temperature, I find that species with parental care exhibit larger sizes at hatching compared to species with no care. I also show that large hatchlings promote the evolution of advanced forms of care but there is no evidence that post-spawning care in general, including simpler forms of care provided predominantly by males, co-evolves with offspring size. In Chapter 3, I use an experimental approach to investigate the potential trade-off between the provision of a safe environment for offspring development and attracting a mate in three-spined stickleback (Gasterosteus aculeatus) males that construct nests. I find that stickleback males build more conspicuous nests on backgrounds that are perceived as safer, but that their investment in nests is balanced against other courtship activities. In Chapter 4, I identify global correlates of variation in nest size using measurements from 1,117 species of cup-nesting passerines. I observe that the pattern of building larger nests in colder environments or habitats with reduced predation threat – first detected at population-level studies – does scale up globally and across a multitude of species. Finally, in Chapter 5, I evaluate the importance of predation and competition in shaping the evolution of nest type and associated life-history traits in passerines. Using data from 4,105 species, I determine that enclosed nests are associated with larger clutch sizes and longer periods of care irrespective of the level of competition in the breeding environment.