Growing or reproducing? Assesing the existence of a trade-off in the globose cactus Gymnocalycium monvillei

Abstract

• Resource allocation in plants is a fundamental aspect of life history theory. In Cactaceae,the specific trade-off between sexual reproduction and vegetative growth has stillnot been studied. The aim of this work was to assess if there is a trade-off betweengrowth and reproduction, and to analyse whether both growth and allocation toreproduction depend on size of the individual.• In this study, we used Gymnocalycium monvillei, a globose cactus endemic to themountains of central Argentina, as a model species. Specifically, we analysed the relationshipof growth (percentage increase in diameter) and size of individuals (diameter)to seed production, seed mass, germination, and mean germination time. Torelativize the effect of size on seed production, two variables were calculated: the ratioof seed production to plant size (RSPS), and the ratio of total seed mass to plant size(RSMS).• We found that both seed production and total seed mass were significantly related tocactus size. However, growth was not related to seed mass or to seed production, evenwhen they were relativized. Germination and mean germination time were not relatedto plant size or growth.• In the studied species, a slow-growing globose cactus, we did not find a trade-offbetween growth and reproduction.