Pre- and post-germination determinants of spatial variation in recruitment in the perennial herb Helleborus foetidus L. (Ranunculaceae)

Abstract

1. Recruitment in plant populations is a multiphase ssquential process. An integrated view of the relationships between the stages and processes involved is therefore needed, but few studies have analysed the direct and indirect effects concerned. We propose a causal model of these relationships and use structural equation modelling (SEM) and path analysis to investigate the direct and indirect effects of pre- and post-germination processes on recruitment. 2. We collected information on seed production, pre-dispersal seed losses, seed removal from the ground, seedling emergence and mortality, and seedling recruitment during the first year after emergence from 1 x 1 m plots centred on reproductive individuals in three geographically distant populations of the perennial herb Helleborus foetidus. 3. The results suggest some congruence between the three populations and indicate that post-germination processes shape the spatial variation in recruitment more than pre-germination processes. Although between-plot variation in recruitment: was mostly explained by seedling emergence and mortality, factors such as seed production and removal still have significant effects on recruitment through various, and frequently contrasting, pathways. 4. Path analysis is a powerful analytical tool for revealing important aspects of the recruitment dynamics of plant populations and the factors determining their spatial variation. Such aspects, including indirect effects, are difficult to quantify with other, more classical, approaches to recruitment.