The Growth, Distribution and Neighbour Relationships of Trifolium Repens in a Permanent Pasture. VI. Conditioning Effects by Neighbours

Abstract

(1) Genetic diversity and phenotype plasticity within any population will allow it to adjust to changing environmental conditions. Their relative importance will depend upon the amount of spatial and temporal heterogeneity and rapidity of change as seen from the plant's-eye-view. (2) Clones of Trifolium repens were collected from patches dominated by Agrostis capillaris, Holcus lanatus and Lolium perenne in an old permanent pasture. The clones were multiplied and then subjected to three different conditioning treatments: repeated cloning in glasshouse conditions, repeated cutting (but not cloning) in boxes outdoors, and transplanting into the original pasture. The conditioning was carried out for varying lengths of time, and the pasture transplants were made into three patch types. (3) Newly collected T. repens showed significant among-grass-neighbour patterns of differentiation for five out of eight morphological characters. Clones from Holcusdominated sites were largest and those from Agrostis-dominated sites smallest. These patterns were altered by the different conditioning treatments. For clones transplanted into the pasture, shorter conditioning periods in the pasture lead to fewer amongsubpopulation differences. (4) The ecological and evolutionary consequences of life in a spatially and temporally patchy environment are discussed. Genetic diversity of the T. repens population may reflect both the avoidance of mortality through phenotype plasticity and the existence of multiple adaptive optima to which genotypes have been fitted by natural selection.