The comparative demography of the pasture weed Echium plantagineum betweenits native and invaded ranges

1. Echium plantagineum is native to the western Mediterranean Basin, where it is a common, but not dominant, component of species-rich annual grasslan ds. Since its introduction into Australia, E. plantagineum has spread to in fest vast areas of predominantly agricultural land in south-east and south- west Australia, where it can be the dominant pasture species. 2. To unravel the ecological factors responsible for the high population ab undance of E. plantagineum in Australia, its demography was compared betwee n sites in the invaded and native ranges. Demographic parameters of E. plan tagineum populations were estimated at a site near Canberra in south-easter n Australia, and at a site near Evora in southern Portugal. Identical facto rial experiments were set up at each site with treatment combinations of th e presence or absence of grazing and pasture competition. 3. The recruitment, survival, fecundity and seed bank dynamics of E. planta gineum populations were measured for each of the treatment combinations ove r 2 years at each site. These data allowed the estimation of demographic pa rameters describing the proportion of E. plantagineum individuals moving fr om one life-cycle stage to the next. 4. Seedling establishment fractions were two to five times greater at Canbe rra than at Evora, and seed bank incorporation rates were three times great er at Canberra than Evora. These demographic differences were those most li kely to play an important role in the greater abundance of E. plantagineum in Australia compared with Mediterranean Europe. Neither seed bank survival rates nor seed production differed between populations at Canberra and Evo ra, while seedling survival rates were always lower at Canberra than at Evo ra. 5. Neither grazing nor pasture competition limited the seed production or s eedling survival of E. plantagineum populations at Evora more than at Canbe rra. 6. An effective approach for the control of E. plantagineum in Australia ma y thus be through the reduction of the seedling establishment fraction. Thi s may be achieved by maintaining significant pasture vegetation cover and r educing the available space for E. plantagineum establishment during autumn .