Abstract
In Angiosperms, perennials typically present much higher levels of inbreeding depression than annuals. The mechanisms leading to this pattern are poorly understood. In fact, despite the potential significance of this pattern for important evolutionary questions, only two hypotheses have been proposed to explain it. Based on the fact that mutations occurring in somatic tissues may be passed onto the offspring in plants, because they do not have a segregated germline, the first hypothesis states that more long-lived species may accumulate more somatic mutations as they grow, thereby generating higher inbreeding depression. The second hypothesis, which is not in contradiction with the first, stems from the observation that inbreeding depression is typically expressed across multiple life stages in Angiosperms. It posits that increased inbreeding depression in more long-lived species could also be explained by the fact that mutations, regardless of whether they are produced during mitosis or meiosis, may differ in the way they affect fitness in annual and perennial populations, through the life stages at which they are expressed. In this study, we aim to investigate the second hypothesis, setting aside somatic mutations accumulation. We combine a physiological growth model and multilocus population genetics approaches in order to describe a full genotype-to-phenotype-to-fitness map, where the phenotype relates to fitness through biological assumptions, so that the fitness land-scape emerges from biological assumptions instead of being assumed a priori. We study the behaviour of different types of mutations affecting growth or survival, and explore their consequences in terms of inbreeding depression and mutation load. Then, we discuss the role deleterious mutations maintained at mutation-selection balance may play in the coevolution between growth and survival strategies.