Forest Ecology and Forest Management, Wageningen University, Wageningen, the Netherlands.
Centre for Crop Systems Analysis, Wageningen University, Wageningen, the Netherlands.
PLoS One. 2019 May 2;14(5):e0209631. doi: 10.1371/journal.pone.0209631. eCollection 2019.
Defoliation and light competition are ubiquitous stressors that can strongly limit plant performance. Tolerance to defoliation is often associated with compensatory growth, which could be positively or negatively related to plant growth. Genetic variation in growth, tolerance and compensation, in turn, plays an important role in the evolutionary adaptation of plants to changing disturbance regimes but this issue has been poorly investigated for long-lived woody species. We quantified genetic variation in plant growth and growth parameters, tolerance to defoliation and compensation for a population of the understorey palm Chamaedorea elegans. In addition, we evaluated genetic correlations between growth and tolerance/compensation.
We performed a greenhouse experiment with 711 seedlings from 43 families with twelve or more individuals of C. elegans. Seeds were collected in southeast Mexico within a 0.7 ha natural forest area. A two-third defoliation treatment (repeated every two months) was applied to half of the individuals to simulate leaf loss. Compensatory responses in specific leaf area, biomass allocation to leaves and growth per unit leaf area were quantified using iterative growth models.
We found that growth rate was highly heritable and that plants compensated strongly for leaf loss. However, genetic variation in tolerance, compensation, and the individual compensatory responses was low. We found strong correlations between family mean growth rates in control and defoliation treatments. We did not find indications for growth-tolerance/compensation trade-offs: genetic correlation between tolerance/compensation and growth rate were not significant.
The high genetic variation in growth rate, but low genetic variation in tolerance and compensation observed here suggest high ability to adapt to changes in environment that require different growth rates, but a low potential for evolutionary adaptation to changes in damage or herbivory. The strong correlations between family mean growth rates in control and defoliation treatments suggest that performance differences among families are also maintained under stress of disturbance.
落叶和光竞争是普遍存在的胁迫因素，会强烈限制植物的表现。对落叶的耐受性通常与补偿性生长有关，而补偿性生长可能与植物生长呈正相关或负相关。生长、耐受性和补偿的遗传变异反过来在植物对不断变化的干扰模式的进化适应中起着重要作用，但对于长寿命的木本物种，这个问题的研究还很不完善。我们量化了下层棕榈 Chamaedorea elegans 种群的生长和生长参数、对落叶的耐受性和补偿能力的遗传变异。此外，我们还评估了生长与耐受性/补偿之间的遗传相关性。
我们在温室中进行了一项实验，使用了来自墨西哥东南部的 43 个家庭的 711 个幼苗，每个家庭有 12 个或更多的 C. elegans 个体。种子是在 0.7 公顷的天然林地区收集的。对一半个体进行三分之二的落叶处理（每两个月重复一次），以模拟叶片损失。使用迭代生长模型量化特定叶面积、生物量分配到叶片和单位叶面积的生长等补偿反应。
我们发现生长速度具有高度的遗传性，并且植物对叶片损失有强烈的补偿能力。然而，耐受性、补偿和个体补偿反应的遗传变异很低。我们发现对照和落叶处理中家族平均生长速度之间存在强烈的相关性。我们没有发现生长-耐受性/补偿权衡的迹象：耐受性/补偿与生长速度之间的遗传相关性不显著。
这里观察到的生长速度的高遗传变异，以及耐受性和补偿的低遗传变异，表明适应需要不同生长速度的环境变化的能力很高，但对损伤或食草动物变化的进化适应潜力较低。对照和落叶处理中家族平均生长速度之间的强烈相关性表明，在干扰压力下，家族之间的表现差异也得以维持。
