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 seedbanks in the introduced area.

有假说认为，入侵植物在其引入分布区内具有更高的适合度，这是因为它们脱离了原生分布区的病原菌与植食动物制约，并将更多资源重新分配至繁殖过程。然而，鲜有研究在原生与引入分布区同时检验这一假说。采用生物地理学研究方法，是解析植物入侵机制、检测引入区种群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）的原生与引入分布区开展繁殖相关指标测定。研究从两个分布区各选取7至10个种群，测定了种子产量、播前种子捕食率、种子与油质体大小以及幼苗大小，并控制了气候差异的影响效应。
对于两种金合欢属植物，其引入分布区内的豆荚完全发育种子占比显著更高，败育种子占比更低，且未出现播前种子捕食现象。长叶金合欢在入侵分布区内的单豆荚种子产量更高，而银叶金合欢则在入侵分布区内的单株种子产量更高。两种植物在入侵分布区内的种子均更大，且长叶金合欢在入侵分布区内的油质体与种子大小比值更低。入侵分布区内的幼苗体型也更大，这表明种子尺寸的提升可带来子代生长能力的增强。
长叶金合欢在两个分布区的生境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，但该差异无法解释其在引入分布区内种子产量与种子尺寸的提升。不过，最低温度对单株豆荚数量具有正向影响效应。
综上，银叶金合欢与长叶金合欢在引入分布区内规避了播前种子捕食，且单果完全发育种子产量更高、种子尺寸更大。这些差异或可解释两种植物的入侵成功：其提升了幼苗生长能力，并在引入分布区内形成了更为丰富的土壤种子库。