title: The role of pollination in the population biology of the monocarpic species Cirsium palustre and Cirsium vulgare.
abstract: The absence of cross-pollination in Cirsium palustre and Cirsium vulgare resulted in reduced achene production while the achenes produced were heavier than those produced after cross-pollimation. Establishment of plants from non-cross-pollinated achenes is comparatively higher, facilitating the founding of a population from isolated individuals in these wind-dispersed species.If achene weight is the result of a balance between cross-pollination and self-pollination (and/or apomixis), the first causing more and thereby lighter achenes to develop, increasing density of flowering individuals in a population may lower achene weight and consequently seedling survival. This may account for the frequently observed decline of populations of fugitive monocarpic perennials.
authors.affiliation: Department of Ecology, University of Leiden, Kaiserstraat 63, 2300 RA, Leiden, The Netherlands.
authors.forename: B H
authors.initials: BH
authors.lastname: van Leeuwen