Aging varies greatly within a single genus: A demographic study of Rhododendron spp. in botanic gardens

Abstract

PREMISE OF THE STUDYThere is mounting evidence that age matters in plant demography, but also indications that relationships between age and demographic rates may vary significantly among species. Age‐based plant demographic data, however, is time‐consuming to collect, and still lacking for most species, and little is known about general patterns across species or what may drive differences.METHODSWe used individual birth and death records for twelve Rhododendron species from botanical gardens and conducted Bayesian survival trajectory analyses to assess how mortality changed with age. We calculated the demographic measures of aging rate, lifespan equality, and life expectancy for each species, and assessed their relationships with the climatic conditions at species’ sites of ancestral origin and with taxonomic group (subgenus).KEY RESULTSWe found substantial among‐species variation in survival trajectories, with mortality increasing, decreasing, or remaining constant with advancing age. Moreover, we found no relationships between demographic measures and ancestral climatic conditions but there were statistically significant differences among taxonomic groups in the rate of change in mortality with age (aging rate).CONCLUSIONSWe conclude that demographic consequences of aging can differ qualitatively, even among species in the same genus. In addition, taxonomic trends in aging rates indicate they may be genetically determined even though evolutionary drivers are still unclear. Furthermore, we suggest there is untapped potential in using botanic garden records in future studies on plant life history.This article is protected by copyright. All rights reserved.