AI Insight
This study analyzed how natural selection acts on new genetic mutations across 11 animal species, finding that the distribution of fitness effects (DFE) varies systematically across the animal kingdom. Mammals show a significantly higher proportion of strongly harmful mutations (22-47%) compared to insects and birds (0-5.4%), with these differences following phylogenetic relationships where closely related species have more similar mutation effects. The results support predictions from Fisher's Geometric Model, suggesting that organismal complexity, genome size, and long-term population size influence how deleterious mutations are across different animal lineages.
Why it matters
Understanding how mutations affect fitness differently across species is fundamental for predicting evolutionary responses to environmental change, assessing extinction risk in endangered populations, and interpreting genetic variation in conservation genetics and human disease studies. The findings suggest that conservation strategies and genetic risk assessments may need to be tailored based on the taxonomic group and life-history characteristics of the species in question.
Understand the Science
by Meixi Lin, Sneha Chakraborty, Carlos Eduardo G. Amorim, Sergio F. Nigenda-Morales, Annabel C. Beichman, Paulina G. Nuñez-Valencia, Jonathan C. Mah, Jacqueline A. Robinson, Christopher C. Kyriazis, Christian D. Huber, Andrew E. Webb, Sarah D. Kocher, Frederick I. Archer, Andrés Moreno-Estrada, Robert K. Wayne, Kirk E. Lohmueller
The distribution of fitness effects (DFE) describes the selection coefficients of newly arising mutations and fundamentally influences population genetic processes. However, the extent and mechanisms of differences in the DFE for non-synonymous mutations have not been systematically investigated across species with divergent phylogenetic histories and ecologies. Here, we inferred the DFE in natural populations of 11 animal (sub)species, including humans, mice, fin whales, vaquitas, wolves, collared flycatchers, pied flycatchers, halictid bees, Drosophila, and mosquitoes. We found that mammals have a higher proportion of strongly deleterious mutations (defined as s≤−0.01; 22% to 47% in mammals; 0.0% to 5.4% in insects and birds) and a lower proportion of weakly deleterious mutations than insects and birds. Further, the DFE co-varies with phylogeny, such that the mean mutation effects are more similar in closely related species (Pagel’s λ = 0.84, P = 0.01). Next, we investigated whether various summary statistics of the DFE were related to variation in life-history traits across these organisms. We found some support for genome size, body mass, and long-term effective population size being correlated with the DFE. Overall, our findings are consistent with predictions derived independently from the Fisher’s Geometric Model (FGM), which defines organismal complexity as the number of phenotypes under selection. FGM predicts that mutations are more deleterious in complex organisms, while strongly deleterious mutations occur more frequently in smaller populations. Our study demonstrates strong phylogenetic signal in the evolution of a fundamental population genetics parameter, and proposes that, through mechanisms of epistasis, long-term population size and organismal complexity could be underlying variation in the DFE across animals.