Plant Conservation and Population Biology, University of Leuven, Arenbergpark 31, Leuven, Belgium.
Department of Biology, Norwegian University of Science and Technology, NTNU, Trondheim, Norway.
Ann Bot. 2020 Oct 30;126(6):1005-1016. doi: 10.1093/aob/mcaa110.
It remains unclear whether invasive species can maintain both high biomass and reproductive output across their invaded range. Along latitudinal gradients, allocation theory predicts that faster flowering onset at high latitudes results in maturation at smaller size and thus reduced reproductive output. For annual invasive plants, more favourable environmental conditions at low latitudes probably result in stronger competition of co-occurring species, potentially driving selection for higher investment in vegetative biomass, while harsher climatic conditions and associated reproductive uncertainty at higher latitudes could reduce selection for vegetative biomass and increased selection for high reproductive investment (stress-gradient hypothesis). Combined, these drivers could result in increased or constant reproductive allocation with increasing latitude.
We quantified life-history traits in the invasive annual plant Impatiens glandulifera along a latitudinal gradient in Europe. By growing two successive glasshouse generations, we assessed genetic differentiation in vegetative growth and reproductive output across six populations, and tested whether onset of flowering drives this divergence.
Trait variation was mainly caused by genetic differentiation. As expected, flowering onset was progressively earlier in populations from higher latitudes. Plant height and vegetative biomass also decreased in populations from higher latitudes, as predicted by allocation theory, but their variation was independent of the variation in flowering onset. Reproductive output remained constant across latitudes, resulting in increased reproductive allocation towards higher latitudes, supporting the stress-gradient hypothesis. We also observed trait genetic differentiation among populations that was independent of latitude.
We show that an annual invasive plant evolved several life-history traits across its invaded range in ~150 years. The evolution of vegetative and reproductive traits seems unconstrained by evolution of flowering onset. This genetic decoupling between vegetative and reproductive traits possibly contributes to the invasion success of this species.
目前尚不清楚入侵物种是否能够在其入侵范围内保持高生物量和高繁殖产量。随着纬度的增加，分配理论预测，高纬度地区开花时间的提前会导致成熟时体型更小，从而降低繁殖产量。对于一年生入侵植物，低纬度地区更有利的环境条件可能导致共生物种之间的竞争更加激烈，这可能会促使它们在营养生长上投入更多，而高纬度地区更恶劣的气候条件和相关的繁殖不确定性可能会降低对营养生长的选择，增加对高繁殖投入的选择（压力梯度假说）。综合来看，这些因素可能导致随着纬度的增加，繁殖分配增加或保持不变。
我们在欧洲的一个纬度梯度上量化了入侵一年生植物 Impatiens glandulifera 的生活史特征。通过连续两代温室种植，我们评估了六个种群在营养生长和繁殖产量上的遗传分化，并测试了开花时间是否驱动了这种分化。
性状变异主要是由遗传分化引起的。正如预期的那样，来自高纬度地区的种群开花时间逐渐提前。植物高度和营养生物量也随着纬度的升高而降低，这符合分配理论的预测，但它们的变化与开花时间的变化无关。繁殖产量在整个纬度范围内保持不变，导致繁殖分配向更高的纬度增加，支持压力梯度假说。我们还观察到种群之间的性状遗传分化与纬度无关。
我们表明，一种一年生入侵植物在大约 150 年的时间里在其入侵范围内进化了几个生活史特征。营养和繁殖特征的进化似乎不受开花时间进化的限制。这种营养和生殖性状之间的遗传分离可能有助于该物种的入侵成功。
