干旱区生态环境知识资源中心

Marsdenia australis and Rhyncharrhena linearis are woody climbers (family Asclepiadaceae) found in semi-arid to arid areas of all mainland states of Australia. Where Studied, they arc declining drastically, probably due to grazing. In Victoria, their conservation Status is vulnerable. In 1991, in Hattah-Kulkync National Park, a site was found carrying single plants of each species. At this site, 384 seedlings and 1,741 seeds of Marsdenia and 240 seedlings of Rhyncharrena were planted underneath trees of Eucalyptus socialis in 1991-1992, half of the seedlings in mammal-proof cages. After higli seedling mortality due to mammal grazing and especially to drought in the first summer, only six of the planted seedling, all of Marsdenia, survived by the end of 1992. All of these, and a further 15 Marsdenia plants derived from seed sowing, have survived until present. Most of them have climbed up nets and ropes provided onto the stems of three Eutcalyptus host plants and at least two of them have produced fruits. Marsdenia is likely to be an obligate outbrccder, in which case the genotypes introduced to the site will be vital in allowing future seed production there. Implications of the work for conservation arid management are stated.