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.

入侵植物被认为在引入区域具有更高的适合度，这是因为它们脱离了本土的病原体与植食动物的压制，并将更多资源分配至繁殖过程。然而，鲜有研究在本土与引入区域同时验证这一假说。生物地理学研究方法是解析植物入侵机制、检测引入区域快速进化改变的核心手段。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）与长叶金合欢（Acacia longifolia），对其本土与入侵范围的繁殖特征展开评估。研究纳入两个分布范围内各7至10个种群，同时考量气候差异的影响，测定了单荚果种子产量、扩散前种子捕食率、种子与油质体大小，以及幼苗大小。

两种金合欢属植物在入侵范围内的荚果内发育完全种子占比均显著更高，败育种子占比更低，且未检测到扩散前种子捕食现象。长叶金合欢在入侵范围内的单荚果种子产量更高，而银叶金合欢则在入侵范围内的单株种子产量更高。两种植物的入侵范围种群所产种子均更大；长叶金合欢在入侵范围内的油质体/种子比值更低。入侵范围种群的幼苗体型也更大，这表明种子尺寸增大可提升后代幼苗的生长潜力。

两个分布范围内长叶金合欢种群所在生境的气候条件并无显著差异。葡萄牙境内银叶金合欢种群的生境最低温度更高，但该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，不过最低温度对单株荚果数量具有正向影响。

综合与结论：银叶金合欢与长叶金合欢在引入区域逃脱了扩散前种子捕食，且单果发育完全种子产量更高、种子尺寸更大。这些特征差异或可解释二者的入侵性：其提升了幼苗生长能力，并在引入区域形成了更为丰富的土壤种子库。