Richardson D M, Van Wilgen B W, Mitchell D T
South African Forestry Research Institute, Jonkershoek Forestry Research Centre, Private Bag X 5011, 7600, Stellenbosch, South Africa.
Department of Botany, University of Cape Town, 7700, Rondebosch, South Africa.
Oecologia. 1987 Feb;71(3):345-354. doi: 10.1007/BF00378706.
Four shrub species of the Australian Proteaceae (Hakea sericea, H. gibbosa, H. suaveolens and H. salicifolia) were introduced to South African fynbos shrublands between 1840 and 1860. H. sericea is highly invasive, H. gibbosa and H. suaveolens are moderately invasive and H. salicifolia is not invasive. The allocation of reproductive energy, germinability, the ability to survive fires and to germinate in burnt and unburnt areas, and the nutrient content of seeds were assessed for the four species. The information was used to investigate whether the success of H. sericea relative to the other three species could be explained by the superior expression of any trait. The most important trait which separates H. sericea from the other species is its ability to produce a large seed bank in its adopted environment in the absence of seed predators. Seed production in H. sericea shrubs with an above-ground dry mass of 8 kg is four times greater than H. gibbosa and more than 16 times that of H. suaveolens. Although H. salicifolia also produces a large seed bank, its seeds are unable to survive fires due to inadequate insulation by the small follicles. The results are compared to dispersal and seed bank data for indigenous South African Proteaceae, which have low dispersal and suffer high pre-dispersal seed predation. We suggest that potential invasives in the fynbos can be identified as species that have: (i) a potentially high seed production that is limited by specialized predators; (ii) an ability to disperse over long distances; and (iii) are pre-adapted to frequent fires and low soil nutrients. The data also support the current strategy of combatting H. sericea using specialized insect seed predators.
1840年至1860年间，四种澳大利亚山龙眼科灌木物种（绢毛哈克木、瘤状哈克木、软叶哈克木和柳叶哈克木）被引入南非开普植物群落灌木丛地区。绢毛哈克木具有高度入侵性，瘤状哈克木和软叶哈克木具有中等入侵性，而柳叶哈克木则没有入侵性。对这四个物种的生殖能量分配、发芽能力、在火烧和未火烧地区的存活及发芽能力以及种子的营养成分进行了评估。利用这些信息来研究绢毛哈克木相对于其他三个物种的成功是否可以通过任何性状的优势表达来解释。将绢毛哈克木与其他物种区分开来的最重要性状是其在没有种子捕食者的情况下，能够在其引入环境中产生大量种子库。地上干重为8千克的绢毛哈克木灌木的种子产量是瘤状哈克木的四倍，是软叶哈克木的16倍多。虽然柳叶哈克木也产生大量种子库，但其种子由于小蒴果的隔热不足而无法在火烧中存活。研究结果与南非本土山龙眼科植物的传播和种子库数据进行了比较，本土山龙眼科植物的传播率低，且在种子传播前遭受大量捕食。我们认为，开普植物群落中潜在的入侵物种可以被确定为具有以下特征的物种：（i）潜在种子产量高，但受到专门捕食者的限制；（ii）具有长距离传播的能力；（iii）预先适应频繁的火灾和低土壤养分。这些数据也支持目前使用专门的昆虫种子捕食者来对抗绢毛哈克木的策略。
