Altered growth, population structure and realised niche of the weed Campuloclinium macrocephalum (Asteraceae) after exposure to the naturalised rust Puccinia eupatorii (Pucciniaceae)

作者：Goodall Jeremy^*; Witkowski E T F; McConnachie Andrew J; Keen Chris

来源：Biological Invasions, 2012, 14(9): 1947-1962.

DOI：10.1007/s10530-012-0205-1

• Biological control
• Climatic conditions
• Compensatory growth
• Realised niche
• Premature senescence
• Tolerance

The alien forb Campuloclinium macrocephalum (Less.) DC. (Asteraceae, pompom weed) invades disturbed rangelands in South Africa. After %26gt; 40 years of naturalisation, infestations around Pretoria were severely damaged in 2006 by the biotrophic rust Puccinia eupatorii Dietel (Pucciniaceae). The disease spread rapidly and has now established at most pompom weed infestations in the country. This study reports on the efficacy of the pathogen as a biocontrol agent of pompom weed, its effect on the retention of the weed%26apos;s realised niche and tolerance to the disease. Eighty rangeland infestations originally assessed over two years in 2003 and 2004 were re-surveyed in 2009. Data from untreated plots at two pompom weed experimental sites where the rust was first detected were also used. Puccinia eupatorii induced premature senescence in late summer and stimulated the production of compensatory growth in autumn. Plants without disease symptoms senesced in late autumn without compensatory growth and remained dormant throughout winter. Pompom weed density did not change significantly over time in both the rangeland study and untreated plots. Disease incidence in rangelands in 2009 was most severe in dense infestations, with sparse infestations having the highest incidence of natural senescence and fewer pustules. The rust did not reduce the realised niche; infestations in grasslands, savanna and wetlands persisted despite significant damage by the disease. Persistence, despite high annual stem mortality, suggests that pompom weed remains adapted to the fungus after prolonged separation from the disease. This study supports earlier findings that disturbance remains key to pompom weed invasion even under biological control. The rust may enhance the biological control of pompom weed with augmentation of additional insect agents, but is unlikely to inflict a significant reduction in the weed%26apos;s population on its own. This may be an important consideration for the biological control of weeds involving biotrophic fungi.

• 出版日期2012-9