Ageing varies greatly within a single genus: evidence from Rhododendrons in botanic gardens

There is mounting evidence that age matters in plant demography, but also indications of that relationships between age and demographic rates may vary significantly among species. Age-based plant demographic data, however, is difficult to collect, and still lacking for most species. We used individual birth and death records for twelve Rhododendron species from botanical gardens and Bayesian survival trajectory analysis to assess how mortality changes with age and whether differences between species are related to ancestral environmental conditions. We found substantial among-species variation in age-trajectories of mortality, no clear relationships between demographic measures and ancestral habitat, but statistically significant differences among taxonomic groups. We conclude that demographic consequences of ageing can differ remarkably, even among species in the same genus, but that causes of this variation are still unclear. Furthermore, we suggest there is untapped potential in using botanic garden records in future studies on plant life history.