Department of Biology, Ecology and Evolution, University of Fribourg, Chemin du Musée 10, 1700 Fribourg, Switzerland.
Ecology. 2013 May;94(5):1005-14. doi: 10.1890/12-1393.1.
The evolution of optimal life history strategies is central for the fitness of organisms in a given environment. Besides divergent selection, other factors may determine regional patterns of differentiation and contribute to life history evolution. In a common-garden environment over three years, we examined life history differentiation across different eco-geographical regions and effects of a specialist root-insect herbivore in the widespread European plant Centaurea stoebe, spotted knapweed. This plant occurs as two cytotypes with contrasting life cycles: monocarpic diploids and polycarpic tetraploids. In addition, the tetraploid cytotype has more recently become invasive in North America. We found significant regional differentiation in traits related to the timing of reproduction and reproductive allocation, but contrasting patterns in diploids and tetraploids. In diploids the degree of regional differentiation was higher compared to native tetraploids, and in the latter compared to invasive tetraploids. Furthermore, a pronounced shift in environmental conditions between the native and introduced range could have contributed to the differentiation between native and invasive tetraploids. The study also revealed the potential of the root-mining insect herbivore Agapeta zoegana, used as a biological control organism, to increase plant performance (presumably through overcompensatory growth), especially in the polycarpic tetraploids, and more so in the introduced populations. These findings suggest that patterns of regional differentiation in C. stoebe may be partly determined by divergent selection, but also strongly modulated by life cycle differences among geo-cytotypes. Furthermore, our study highlights the importance in applying a comprehensive and long-term approach when studying regional differentiation in plants.
最优生活史策略的进化是生物体在特定环境中适应的核心。除了分歧选择，其他因素也可能决定区域分化模式，并有助于生活史进化。在三年的共同花园环境中，我们研究了不同生态地理区域的生活史分化，以及专门的根虫食草动物在广泛分布的欧洲植物矢车菊属斑点矢车菊中的作用。这种植物有两种具有不同生命周期的细胞型：单性二倍体和多性四倍体。此外，四倍体细胞型在北美最近变得具有入侵性。我们发现与繁殖时间和生殖分配有关的性状存在显著的区域分化，但在二倍体和四倍体中存在相反的模式。在二倍体中，与原生四倍体相比，区域分化程度更高，而在后者中，与入侵性四倍体相比，区域分化程度更高。此外，原生和引入范围之间环境条件的明显变化可能导致了原生和入侵性四倍体之间的分化。该研究还揭示了根钻食草昆虫食草动物 Agapeta zoegana 的潜力，它被用作生物防治剂，可以提高植物的表现（可能通过过度补偿生长），特别是在多性四倍体中，在引入种群中更为明显。这些发现表明，C. stoebe 的区域分化模式可能部分由分歧选择决定，但也受到地理细胞型之间生命周期差异的强烈调节。此外，我们的研究强调了在研究植物区域分化时应用全面和长期方法的重要性。
