Genetic Variation and Phenotypic Plasticity in Populations of Paterson's Curse (Echium plantagineum L.) In South-Eastern Australia

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Abstract
Natural populations of Echium plantagineum on an east-west line across south-eastern Australia were sampled on three occasions during the growing season, and seeds collected from individual plants in each population were grown in a common glasshouse. In another experiment seedlings of E. plantagineum were divided and clones from each plant were grown under two soil moisture regimes. Field populations differed significantly in all seven characters measured at all sampling dates but, with one exception, between-population differences were unrelated to five climatic indices. Glasshouse populations differed significantly in 15 of 27 characters; variations in some of these characters were related by regression analysis to one or more of the climatic indices. Clones grown under moisture stress flowered later, had proportionally wider leaves and were smaller than well watered clones. The data suggest that an ecocline has developed, or is developing, in E. plantagineum in south- eastern Australia in response to large-scale and long-term aspects of climate, although extensive genetic variation between individuals in each population was also observed. This species exhibits a great deal of phenotypic plasticity in response to localized environmental factors.