Longevity in plants impacts phylogenetic and population dynamics.

Phylogenies of long-lived plants often exhibit short molecular branch lengths and high levels of gene-tree conflict. However, the biological mechanisms underlying these patterns remain unclear. We examine this with simulations and through empirical examination of several large seed plant clades. We used an agent-based simulation model varying lifespan, degree of overlapping generations, and somatic mutation. We also compared simulated outcomes to phylogenomic patterns in several datasets of seed plants that include life-history shifts. Lifespan and overlapping generations together can generate both short branches and elevated gene-tree conflict. Somatic mutation can amplify these effects, although available evidence suggests mutation rates are often too low to drive major phylogenetic consequences. Variation across simulation parameterizations can mirror the diversity of phylogenomic patterns observed among lineages with differing life histories. Lifespan and generation overlap are potentially major contributors to characteristic phylogenetic signatures in long-lived plants. Consequently, life history should be considered when interpreting evolutionary patterns, substitution rates, and among-lineage heterogeneity in long-lived plant lineages.