Open Access

Petrus C. Heyligers

• Euphorbia paralias, Sea Spurge (Euphorbiaceae), indigenous to the sandy shores of southern Europe and northern Africa, was first collected in Australia near harbours: at Albany, Western Australia in 1927 and at Port Victoria, South Australia in 1934. E. paralias seeds are buoyant and dispersed by ocean currents. By 1974 E. paralias had reached Wilsons Promontory, but was not recorded from southern New South Wales until 1987, while in East Gippsland it was first recorded in 1993. Since then it has spread to other beaches in this region and has also turned up on Lord Howe Island. Surveys have been carried out to ascertain the status of Euphorbia paralias in East Gippsland and southern New South Wales during the last decade. The results together with other observations have been correlated with the published results of drifter experiments. The latter relied on reporting back of stranded bottles, cards or envelopes released at certain distances offshore. The establishment of E. paralias in southern New South Wales, before doing so in East Gippsland, is in agreement with the stranding pattern of bottles released west of Wilsons Promontory. Another bottle and two cards released in eastern Bass Strait washed up on Lord Howe Island, thus underpinning the assumption that the colonising E. paralias seed was carried there on ocean currents. E. paralias is still expanding its range in New South Wales. Modelling based on climatic parameters has shown that extension to the lower North Coast of New South Wales can be expected. However, the spread of the introduced sea-rocket Cakile edentula beyond its known climatic range into the Great Barrier Reef area could provide a precedent for what may also happen in the case of E. paralias.