Genome size and phenotypic change: insights on contemporary evolution across biological groups

Environmental changes threaten the persistence of wild populations and can drive adaptive phenotypic changes. However, predicting the phenotypic outcome of an environmental change based on features of the species remains challenging. Genome size has been linked to variables that could influence the amount and rate of phenotypic change on contemporary time-scales. Two contrasting hypotheses have been proposed. The first suggests that larger genome sizes are associated with greater amounts and rates of phenotypic change, due to increased genetic variance and phenotypic plasticity. The second suggests the opposite based on the negative effect of genome size on both generation time and cell duplication time. We tested these two hypotheses using the Phenotypic Rates of Change Evolutionary and Ecological Database. We analysed the relationships among genome size, phenotypic trait variability, mean trait change, and generation time. We found no support for the either of the tested hypotheses. Overall, the genome size explained less than 2% of the total variance in the amount of phenotypic change. In plants only, we found a consistent and negative effect of genome size on phenotypic change. However, we found no relationship between genome size and generation time, and we found no relationship between genome size and phenotypic variance. However, the consistent and relevant effect of phenotypic variance on the mean-scaled phenotypic change is worth highlighting from a conservation perspective because assessing the phenotypic variability of traits related to the niche breadth in different dimensions could inform us about the vulnerability of natural populations facing unexpected environmental changes.