Vilà Montserrat, Bartomeus Ignasi, Gimeno Isabel, Traveset Anna, Moragues Eva
Department of Animal and Plant Biology and Ecology, Unit of Ecology, CREAF, Center for Ecological Research and Forestry Applications, Universitat Autònoma de Barcelona, E-08193 Bellaterra, Barcelona, Spain.
Ann Bot. 2006 Jun;97(6):1055-62. doi: 10.1093/aob/mcl052. Epub 2006 Apr 13.
Success during the early stages of the life-history of alien plants is essential for invasion to occur. The reproductive components of plant invaders have mostly been studied in species reproducing sexually but little is known about invaders that depend exclusively on vegetative reproduction. In this paper, the importance of the different recruitment stages on population growth is quantified and, thus, the invasion potential of the South African annual geophyte Oxalis pes-caprae invading Mediterranean ecosystems is assessed.
Tests and experiments were conducted across Menorca (Balearic Islands) to analyse the spatial variability of Oxalis pes-caprae reproductive components (i.e. bulb production, bulb bank, bulb predation, bulb mortality, bulb dormancy, bulb germination, plant establishment and survival).
Oxalis pes-caprae has a transient bulb bank that remains dormant in the soil during summer. High levels of bulb predation after dispersal, followed by bulb mortality during summer or a failure to germinate in autumn were the most critical factors limiting plant establishment. Bulb germination was high. However, plant establishment and bulb production is constrained by intraspecific competition, but is not affected by soil disturbance. No symptoms of spatial discordance could be found between recruitment stages because the spatial variability of the life cycle was extremely low at all the scales examined (i.e. among populations, habitats and microsites). It was estimated that, on average, 4 % of bulbs can become plants the following year and the field rate of population increase (lambda) to be 0.08.
The results suggest that invasion is constrained by post-dispersal bulb predation, loss of viability of the propagule bank due to summer drought and high intraspecific competition. However, a high spatial concordance between recruitment stages and probably a high propagule pressure due to human and livestock bulb dispersal determine the success of this invader across Menorca Island.
外来植物在其生活史早期阶段的成功对于入侵的发生至关重要。植物入侵者的繁殖组成部分大多是在有性繁殖的物种中进行研究的，但对于那些完全依赖营养繁殖的入侵者了解甚少。本文量化了不同定居阶段对种群增长的重要性，从而评估了入侵地中海生态系统的南非一年生地下芽植物酢浆草的入侵潜力。
在梅诺卡岛（巴利阿里群岛）开展了测试和实验，以分析酢浆草繁殖组成部分（即球茎生产、球茎库、球茎捕食、球茎死亡率、球茎休眠、球茎萌发、植株定植和存活）的空间变异性。
酢浆草有一个短暂的球茎库，在夏季土壤中保持休眠状态。传播后球茎被捕食的水平很高，随后在夏季球茎死亡或秋季未能萌发是限制植株定植的最关键因素。球茎萌发率很高。然而，植株定植和球茎生产受到种内竞争的限制，但不受土壤干扰的影响。在定居阶段之间未发现空间不协调的症状，因为在所研究的所有尺度（即种群之间、生境之间和微生境之间），生命周期的空间变异性极低。据估计，平均而言，4%的球茎次年可长成植株，种群年增长率（λ）为0.08。
结果表明，入侵受到传播后球茎被捕食、夏季干旱导致繁殖体库活力丧失以及种内竞争激烈的限制。然而，定居阶段之间高度的空间一致性以及可能由于人类和牲畜传播球茎而产生的高繁殖体压力决定了这种入侵者在梅诺卡岛的成功。
