The role of parents in Evolution

In this thesis, I investigated the role of parental care in evolution. Parents provide the environment in which offspring develop and therefore have a large influence on their offspring's phenotypes, and so are in prime position to influence evolutionary processes. I used an experimental approach, and focused on the burying beetle, $\textit{Nicrophorus vespilloides}$. The burying beetle is a perfect system for this question: they exhibit elaborate biparental care which is correlated with rapid speciation in the $\textit{Nicrophorus}$ genus. I started with a thorough exploration of burying beetle ecology and how the guild structure and interspecific competition in local populations can shape phenotypic evolution of my focal species, $\textit{N.~vespilloides}$. Interspecific competition shapes how the carrion niche is partitioned, which feeds back onto the evolution of body size within $\textit{Nicrophorus}$ reducing competition. The evolution of parental care in this genus likely facilitated its adaptive radiation, as parental care is linked with body size, both within and across species. But to what extent does the ecology shape the production and maintenance of phenotypic and genetic variation? I then use a quantitative genetic approach to show that body size and development time of $\textit{N.~vespilloides}$ shows no additive genetic variation. Evolution of these fitness related traits can only occur through maternal effects or sibling effects. I tested this prediction by mimicking the radiation of the burying beetles by imposing my own selection on body size when parents could care for their offspring and when they could not. The presence of post-hatching parental care dramatically changed how populations responded to selection, through a combination of cooperation between parents and offspring, and cooperation between offspring. As well as shaping the evolutionary potential of populations, an experimental change in parental care can induce new selective forces, favouring adaptive novelties for the new social environment. Larvae evolving without parental care evolved disproportionately larger mandibles when small to better adapt them to a life without care. Much is known about the evolution of parental care across the animal kingdom, but what happens next: are the burying beetles a "one-off"? I compiled data across the arthropods comparing clades that exhibit post-hatching parental care with their sister clades and show that clades with care are more species rich. While the mechanism may not be the same as with $\textit{Nicrophorus}$, I discussed other potential mechanisms that may be at play in the role of parents in evolution.I was funded by the European Research Council (310785_Baldwinian_Beetles to Prof. Rebecca M. Kilner)