Evolution of semelparity in Mount Kenya lobelias

Summary Two closely related long-lived rosette plants in the genusLobelia occur on alpine Mount Kenya.Lobelia telekii grows in drier sites and is semelparous (dies after first reproduction).Lobelia keniensis grows in wetter sites and is iteroparous (flowers repeatedly). I used long-term data to evaluate two related models of the evolution of semelparity (reproductive effort and demographic), and found evidence to support only one. Eight years of population data indicate that a simple mathematical model accurately describes the demographic conditions that have favoured the evolution of semelparity. In drier sites,Lobelia individuals flower so infrequently and suffer such high mortality between reproductive episodes that the probability of future reproduction is outweighed by the greater fecundity associated with semelparity.