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Clonal growth is an important attribute of many groups of plants and animals (White 1979, Harper et al. 1986). In the plant kingdom, phyla from all evolutionary levels show the capacity for clonal growth. The ability to proliferate vegetatively is found within 10 out of 11 classes of vascular plants and within all seven classes with extant representatives, although rare within the Gymnospermopsida (Mogie and Hutchings 1990), and 69 out of 163 families of vascular plants are able to proliferate vegetatively (Tiffney and Nicklas 1985). The importance of clonal growth in temperate and more northerly ecosystems is apparent when the ground area covered by clonal plants is estimated. In the Arctic, 0.9 x 106 km2 of land is covered by Eriophorum vaginatum (Miller 1982) which is a caespitose clonal plant, where recruitment from seedlings depends on small and large scale disturbances in the vegetation (Gartner et al. 1986). In Britain, the most productive natural/seminatural vegetation is dominated by clonal plants such as Phragmites communes and Pteridium aquilinum (Callaghan et al. 1981), while infertile areas are also dominated by clonal plants such as Calluna vulgaris and Nardus stricta (Bunce and Barr 1988). The area of Britain is 230000 km2 and 19% of this is covered by Britain's ten most extensive species which are all clonal (Table 1; Bunce and Barr 1988). In temperate and boreal forests, clonally proliferating species such as Vaccinium and Empetrum species and Deschampsia flexuosa are also abundant. |
