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.

现有假说认为，入侵植物在入侵区域具备更高的适合度（fitness），这源于它们脱离了病原菌与植食性动物的调控，并将资源重新分配至繁殖过程。然而，鲜有研究在本土与入侵区域同时验证这一假说。生物地理学研究方法（biogeographical approach）是解析植物入侵机制、检测入侵区域内快速进化改变的核心手段。
本研究针对两种来自澳大利亚的入侵性木本豆科植物——银叶金合欢（Acacia dealbata）与长叶金合欢（Acacia longifolia）的本土与入侵分布范围开展繁殖相关指标评估。研究在两个分布范围的7-10个种群中，测定了种子产量、扩散前种子捕食（pre-dispersal seed predation）、种子与油质体（elaiosome）大小以及幼苗大小，并考量了气候差异的影响。
两种金合欢在入侵区域的豆荚中完全发育种子的占比均显著更高，败育种子占比更低，且未发生扩散前种子捕食现象。长叶金合欢在入侵区域的单豆荚种子产量更高，而银叶金合欢则在入侵区域的单株种子产量更高。两种植物在入侵区域的种子体积均更大；长叶金合欢在入侵区域的油质体与种子的比值更小。此外，入侵区域的幼苗体积也更大，这表明种子体积的提升可带来后代生长的增强。
长叶金合欢在两个区域的分布位点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位点的最低气温更高，但该差异并不能解释入侵区域种子产量与种子体积的提升，不过其对单株豆荚数量具有正向影响。
综上，银叶金合欢与长叶金合欢在入侵区域摆脱了扩散前种子捕食的压力，并表现出单果完全发育种子产量提升与种子体积增大的特征。这些差异或可解释两种植物的入侵性：它们可促进幼苗生长，并在入侵区域形成丰富的土壤种子库。