Postdispersal Parent-Offspring Conflict in Plants: Antecedent and Hypothesis from the Andes

Abstract

Analyses of plant life history have ignored post-dispersal interactions between parent and offspring, although such effects may be widespread. Field studies of demography and population control in Espeletia schultzii (Compositae), a dominant species above treeline in the Venezuelan Andes, suggest a model in which parent-offspring conflict increases in importance along a gradient of increasing interspecific competition: where vegetation is dense, parents create safe sites for offspring, so that juvenile survivorship is greatest near parents, even though offspring and parents compete for resources. This, along with very local seed dispersal, causes aggregation of offspring around parents, intensifying parent-offspring competition for resources in the future. In this case, parental inclusive fitness may be increased by the evolution of decreased longevity. In more extreme habitats other species are uncommon compared to E. schultzii, so interspecific competition is less important, eliminating the parental safe site phenomenon; juvenile establishment is rare everywhere, and is lowest near conspecific adults, because adults and juveniles still compete for resources. As a result, offspring do not aggregate around parents. This reduces subsequent parent-offspring competition, and so reduces selection for early parent death.