Within-Species Diversity in Natural Populations of Holcus Lanatus, Lolium Perenne and Trifolium Repens from Four Different-Aged Pastures

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Abstract
(1) The nature and extent of diversity within single natural populations of Holcus lanatus, Lotium perenne and Trifolium repens, collected from four different-aged adjacent pastures in the lower Fraser Valley of British Columbia, Canada, was investigated. (2) One hundred clones of each species were collected from each pastures and planted in a common garden. Fifteen vegetative and floral characteristics were measured on each sampled clone during one growing season. (3) The variability within each population was large, but all three species showed significant differences in the quantity of variation present among the different-aged pastures. Many characters, especially for Lolium perenne and Trifolium repens, showed a decline in mean values and variance with increasing pasture age. (4) The overall high diversity may have been maintained by a heterogeneous biotic environment and the general decline in diversity may be attributable to continuous environment and the general decline in diversity may be attributable to continuous elimination of the less-fit genotypes by competition and grazing. The ecological and evolutionary implications of this are considered.