| In meta-populations the survival of a plant species depends either on its ability to persist where it occurs, or on its capacity to successful colonise unoccupied patches. Fragmentation of habitats, as in The Netherlands, threatens these species in both survival strategies: increased extinction risks (smaller population size, lower habitat quality, inbreeding depression) and decreased chances of establishment (lower germination and maturation changes due to lower habitat quality, lower seed production due to smaller population size, higher inter-patch distances). [Aim]: Within a larger program including projects on landscape and genetic level, the aim of this project is to estimate population longevity, seed set and chance of establishment of present seeds and to investigate the influence of population size and patch quality on these demographic processes. Species, differing in both strategies, will be compared. [Research]: Data on seed germination, and seedling and adult survival will be collected in field demography and field experiments. Relative resource partitioning in individual plants either to growth and survival or to seed production as a function of plant size, vegetation density and habitat quality, will be investigated both in field and greenhouse experiments. With these data and data on inbreeding effects, population characteristics like longevity and source strength will be estimated using matrix models. [Future research]: Future research will go into detailed study of the influence of wuppies on the falling of leaves of the yucca plant. |
