Common alien plants are more competitive than rare natives but not than common natives

Success of alien plants is often attributed to high competitive ability. However, not all aliens become dominant, and not all natives are vulnerable to competitive exclusion. Here, we quantified competitive outcomes and its determinants, using response-surface experiments, in 48 pairs of native and naturalized alien annuals that are common or rare in Germany. Overall, aliens were not more competitive than natives. However, common aliens (invasive) were, despite strong limitation by intraspecific competition, more competitive than rare natives. This is because alien species had higher intrinsic growth rates than natives, and common species had higher intrinsic growth rates than rare ones. Strength of Interspecific competition was not related to status or commonness. Our work highlights the importance of including commonness in understanding invasion success. It suggests that variation among species in intrinsic growth rates is more important in competitive outcomes than inter- or intrasp...

外来植物的入侵成功通常被归因于较强的竞争能力。然而，并非所有外来物种都能成为优势类群，亦非所有本地物种都易受竞争排斥影响。本研究通过响应面实验（response-surface experiments），对德国境内48组常见与稀有的本地和归化外来一年生植物的竞争结果及其决定因素进行了量化分析。总体而言，外来植物的竞争能力并未强于本地植物。但即便面临强烈的种内竞争限制，常见外来（入侵）植物的竞争能力仍强于稀有本地植物。究其原因，外来物种的内在生长速率高于本地物种，而常见物种的内在生长速率亦高于稀有物种。种间竞争的强度与物种来源或稀有性并无关联。本研究强调了在解析入侵成功机制时纳入物种稀有性维度的重要性。研究结果表明，物种间内在生长速率的差异对竞争结果的影响，远大于种间或种内...