Porter School of the Environment and Earth Sciences, Tel Aviv University, Tel Aviv, Israel.
The Invasive Plant Lab, Shamir Research Institute, University of Haifa, Katzrin, Israel.
Am J Bot. 2023 Jul;110(7):e16192. doi: 10.1002/ajb2.16192. Epub 2023 Jun 27.
Dispersal ability (i.e., investment in dispersing structures) can vary across plant species or populations, such as between core compared to leading populations of invasive plants. However, in heterocarpic plants, which produce propagules with varying dispersal abilities, dispersal potential can also vary via investment in the proportion of dispersing morphs (termed dispersal rate). Nevertheless, very little is known about the interplay between investment in dispersal ability vs. dispersal rate or how each is affected by varying environmental pressures.
This study examined the interplay between dispersal ability and dispersal rate across the invasion route of the heterocarpic plant Heterotheca subaxillaris. Capitula of H. subaxillaris were collected from eight populations along its invasion route in the Eastern Mediterranean coastal plain. The dispersal ability of the dispersing pappus-bearing achenes was measured as the ratio between pappus width and biomass. Dispersal rate was calculated as the ratio between the number of dispersing achenes and total achenes per capitulum.
Dispersal ability and dispersal rate were found to be negatively correlated across populations of H. subaxillaris, with a greater investment in pappus width in populations at the leading edge of the invasion compared to a greater proportion of dispersing achenes in core populations.
Our results suggest a trade-off might exist between dispersal ability and dispersal rate, which could change along the invasion route of heterocarpic plants such as H. subaxillaris and contribute to their invasive success. This study highlights the importance of examining both dispersal traits when studying the dispersal potential of heterocarpic species.
扩散能力（即分散结构的投资）在植物物种或种群之间可能会有所不同，例如在入侵植物的核心种群与前沿种群之间。然而，在异果性植物中，由于具有不同扩散能力的繁殖体的产生，通过对分散形态的投资（称为扩散率），扩散潜力也会发生变化。然而，人们对投资分散能力与扩散率之间的相互作用知之甚少，也不知道它们如何受到不同环境压力的影响。
本研究通过对异果性植物 Heterotheca subaxillaris 的入侵途径，检验了扩散能力和扩散率之间的相互作用。从 Heterotheca subaxillaris 入侵路线的八个种群中收集了头状花序。具有分散的毛状附属物的瘦果的扩散能力通过毛状附属物宽度与生物量的比值来衡量。扩散率的计算方法是分散瘦果的数量与每个头状花序中总瘦果的比例。
发现 H. subaxillaris 的种群之间的扩散能力和扩散率呈负相关，在入侵前沿的种群中，毛状附属物宽度的投资较大，而在核心种群中，分散瘦果的比例较大。
我们的研究结果表明，在异果性植物如 H. subaxillaris 的入侵途径中，可能存在扩散能力和扩散率之间的权衡，这可能会随着入侵的发生而发生变化，并有助于它们的入侵成功。本研究强调了在研究异果性物种的扩散潜力时，同时检查两种扩散特征的重要性。
