VARIATION IN THE MORPHOLOGY AND FLOWERING TIME OF CLUSTER CLOVER (TRIFOLIUM-GLOMERATUM L) AND ITS RELATIONSHIP TO DISTRIBUTION IN SOUTHERN AUSTRALIA

Cluster clover is a widely distributed and ecologically successful int roduced legume in southern Australia. In an attempt to understand the role of genetic variation in this success, morphological and physiolog ical traits were measured in 94 accessions from southern Australia and 6 from the Mediterranean basin. Flowering time ranged from 105 to 185 days after sowing, but was not strongly correlated with annual rainfa ll or length of growing season at the site of collection. Variation in other traits partitioned the populations into two morphs which, apart from flowering time and leaf marker, were largely homogeneous. The mo rphs differed significantly in floret number per inflorescence (22 v. 32-37) and seed mass (379 mu g v. 523 mu g), had different growth habi ts and strong within-morph associations between leaf markers and stipu le and petal coloration. The morphs differed in their distributions wi thin southern Australia and the pattern of distribution was related to summer maximum temperatures, winter minimum temperatures and spring r ainfall. These results demonstrate that genetic variation has been imp ortant to the success of cluster clover and suggests that the variatio n is organized. The pattern of variation observed and its relationship to ecogeography is consistent with findings for other highly inbreedi ng species. A map of the species distribution in Western Australia is presented.