Meristem allocation and life-history evolution in herbaceous plants

Generalisations of life histories in plants are often framed in terms of allocation to reproduction. For example, relative allocation to reproduction is commonly found to be higher in semelparous than in iteroparous plant species. However, the association between vegetative traits and life history has been largely unexplored. In higher plants, reproductive and vegetative function can be measured in terms of meristem allocation. Under this approach, two vegetative traits (apical dominance (the suppression of axillary meristem development) and branching intensity (the commitment of axillary meristems to branches)) can be measured as well as one reproductive trait (reproductive effort). We used phylogenetically independent contrasts to compare reproductive and vegetative function in annual semelparous and perennial iteroparous species. Twenty congeneric species pairs (each species pair represented by one semelparous and one iteroparous species) across nine families were selected based on availability of herbarium specimens. Semelparous life-history evolution was associated with higher reproductive effort. Conversely, iteroparous life-history evolution was associated with higher apical dominance. Branching intensity was not associated with life history. An evolutionary association between life history and apical dominance but not branching intensity suggests a complex relationship between allocation to vegetative traits and the evolution of plant strategies across environments.