Data from: Evidence for enemy release and increased seed production and size for two invasive Australian acacias

Invasive plants are hypothesized to have higher fitness in introduced areas due to their release from pathogens and herbivores and the relocation of resources to reproduction. However, few studies have tested this hypothesis in native and introduced regions. A biogeographical approach is fundamental to understanding the mechanisms involved in plant invasions and to detect rapid evolutionary changes in the introduced area. Reproduction was assessed in native and introduced ranges of two invasive Australian woody legumes, Acacia dealbata and A. longifolia. Seed production, pre-dispersal seed predation, seed and elaiosome size and seedling size were assessed in 7-10 populations from both ranges, taking into account the effect of differences in climate. There was a significantly higher percentage of fully developed seeds per pod, a lower proportion of aborted seeds and the absence of pre-dispersal predation in the introduced range for both Acacia species. Acacia longifolia produced more seeds per pod in the invaded range, whereas A. dealbata produced more seeds per tree in the invaded range. Seeds were bigger in the invaded range for both species and elaiosome:seed ratio was smaller for A. longifolia in the invaded range. Seedlings were also larger in the invaded range, suggesting that the increase in seed size results into greater offspring growth. There were no differences in the climatic conditions of sites occupied by A. longifolia in both regions. Minimum temperature was higher in Portuguese A. dealbata populations but this difference did not explain the increase in seed production and seed size in the introduced range. It did have however a positive effect on the number of pods per tree. Synthesis. Acacia dealbata and A. longifolia escape pre-dispersal predation in the introduced range and display a higher production of fully developed seeds per fruit and bigger seeds. These differences may explain the invasion of both species because they result in an increased seedling growth and the production of abundant soil seed banks in the introduced area.

入侵植物被学界假设在引入区域具有更高的适合度，这源于它们脱离了原生环境中的病原体与植食性动物的压制，并将资源重新分配至繁殖过程。然而，目前鲜有研究在原生分布区与引入分布区同时验证这一假说。生物地理学研究方法是理解植物入侵机制、并检测引入区域内快速演化过程的核心手段。本研究针对两种入侵性澳大利亚木本豆科植物——银叶金合欢（Acacia dealbata）和长叶金合欢（A. longifolia）——分别在其原生分布区与引入分布区开展繁殖相关指标评估。研究纳入两个分布区各7至10个种群，综合考量气候差异的影响，对种子产量、扩散前种子捕食率、种子与油质体大小以及幼苗大小进行了测定。两种金合欢属植物在引入区域均表现出显著更高的单荚饱满种子占比、更低的败育种子比例，且未检测到扩散前种子捕食现象。长叶金合欢在入侵区域的单荚种子数量更高，而银叶金合欢在入侵区域的单株种子产量更高。两个物种在入侵区域的种子均更大，且长叶金合欢在入侵区域的油质体/种子比值更低。入侵区域的幼苗体型也更大，这表明种子尺寸的提升可促进子代植株的生长。长叶金合欢在两个分布区所处生境的气候条件并无显著差异。葡萄牙境内的银叶金合欢种群所处生境的最低温度更高，但该气候差异无法解释其在引入区域的种子产量与种子尺寸提升现象，不过该差异对单株荚果数量具有正向影响。研究总结：银叶金合欢与长叶金合欢在引入区域摆脱了扩散前种子捕食压力，且单果饱满种子产量更高、种子尺寸更大。这些差异或可解释两个物种的入侵机制——它们可提升幼苗生长速率，并在引入区域形成大量土壤种子库。