Ecology of 'Phyla canescens' (Verbenaceae) in Australia

Abstract

'Phyla canescens' has invaded large areas of wetland and grassland on floodplains in Australia, particularly the Murray Darling Basin, where 'P. canescens' threatens the sustainability of internationally significant wetlands and the viability of grazing enterprises. The species was introduced into Australia from South America, where it is a common and widespread species of floodplains and waterways, particularly in areas subject to constant grazing, or otherwise continuously disturbed. It has been promoted in Australia and elsewhere as a hardy groundcover for its perceived aesthetic and soil conservation values. 'Phyla canescens' continues to be sold in the horticulture industry, invariably labelled "Phyla nodiflora"; a closely related species with which it is frequently confused. Both species are generally associated with waterways and floodplains and share a prostrate habit, with adventitious roots developing at each node along the numerous, intertwining stolons. Both species form dense mats to the exclusion of other vegetation. While 'P. canescens' has typically smaller features and inhabits more southerly, inland areas with heavy clay soils, the coarser "P. nodiflora" is more common in northern, coastal regions with sandy soils. The general lack of quantitative information on fundamental aspects of the life-history of 'P. canescens' is a substantial impediment to the development of sustainable and ecologically sound management protocols for this species, including biological control, and the communities which it invades. Experiments were devised to help address this information gap, the results of which are presented in this thesis.