Data from: Demonstration of pollinator-mediated competition between two native Impatiens species, Impatiens noli-tangere and I. textori (Balsaminaceae)

Plant–plant interspecific competition via pollinators occurs when the flowering seasons of two or more plant species overlap and the pollinator fauna is shared. Negative sexual interactions between species (reproductive interference) through improper heterospecific pollen transfer have recently been reported between native and invasive species demonstrating pollination-driven competition. We focused on two native Impatiens species (I. noli-tangere and I. textori) found in Japan and examined whether pollinator-mediated plant competition occurs between them. We demonstrate that I. noli-tangere and I. textori share the same pollination niche (i.e., flowering season, pollinator fauna, and position of pollen on the pollinator's body). In addition, heterospecific pollen grains were deposited on most stigmas of both I. noli-tangere and I. textori flowers that were situated within 2 m of flowers of the other species resulting in depressed fruit set. Further, by hand-pollination experiments, we show that when as few as 10% of the pollen grains are heterospecific, fruit set is decreased to less than half in both species. These results show that intensive pollinator-mediated competition occurs between I. noli-tangere and I. textori. This study suggests that intensive pollinator-mediated competition occurs in the wild even when interacting species are both native and not invasive.传粉者介导的植物种间竞争，发生于两个或多个植物物种花期重叠且共享传粉者区系的场景中。近期已有研究报道，本土物种与入侵物种间可通过不当异种花粉传递引发物种间有害生殖相互作用（生殖干扰），进而表现为传粉驱动的竞争。本研究聚焦于日本境内分布的两种本土凤仙花属（Impatiens）物种：水金凤（I. noli-tangere）与野凤仙花（I. textori），旨在探究二者之间是否存在传粉介导的植物竞争。研究证实，水金凤与野凤仙花共享相同的传粉生态位——即二者的花期、传粉者类群以及花粉在传粉者体表的着生位置均一致。此外，若两种凤仙花的植株间距在2米以内，二者的绝大多数柱头表面均会沉积异种花粉，进而导致坐果率下降。进一步通过人工授粉实验发现，即使仅10%的花粉为异种花粉，两种凤仙花的坐果率均可降至原本的一半以下。上述结果表明，水金凤与野凤仙花之间存在强烈的传粉介导竞争。本研究表明，即使相互作用的物种均为本土非入侵物种，野外环境中仍可能发生强烈的传粉介导竞争。