Data from: Exotic flower visitors exploit large floral trait spaces resulting in asymmetric resource partitioning with native visitors

1.Exotic species often cause severe alterations in native communities due to their ability to rapidly and efficiently utilize a broad spectrum of resources. In flower-visitor interactions, the breadth of resource use by native and exotic animals as well as the partitioning of resources among them is often estimated based on the number of (shared) plant species used as resources. However, whether a flower visitor is able to exploit plant resources has been shown to be delimited by functional floral traits such as morphological barriers or attractive or repellent chemical cues. Each of the ecologically relevant traits can be viewed as a dimension of a Hutchinsonian n-dimensional hypervolume, which characterizes the range of phenotypes exploitable by a species.

2.In this study, we quantified the sizes and overlaps of n-dimensional hypervolumes defined by floral traits that are exploitable by native and exotic flower visitors (afterwards referred to as exploited space, ES). In the heavily invaded Hawai'i Volcanoes National Park, USA, we phenotyped 40 native and exotic plant species and recorded flower-visitor interactions. To quantify the size and overlap of ES, we applied dynamic range boxes (dynRB).

3.On average, exotic flower visitors were more generalized in resource use (larger ES) than natives ones, which is additionally indicated by the absence of native flower visitors on exotic flowering plant species. In particular, ES based on floral scent emission was larger for exotic flower visitors compared to native ones. The unevenly expanded ES of native and exotic animals led to an asymmetric overlap of floral ES where the exotic flower visitors shared only a small proportion of their ES with natives but occupied a large proportion of the ES of natives.

4.The asymmetry in resource use of native and exotic flower visitors suggests a potential advantage in resource exploitation of the latter, potentially explaining their success in Hawaiian ecosystems. Predicted range expansion of exotic plant and animal species may further increase the competition for and reduce the availability of resources for native animals. This may lead to further declines of native species and increasing threats for Hawaiian ecosystems.

1. 外来物种往往会对本地群落造成严重改变，因其能够快速且高效地利用广泛的资源。在访花互作（flower-visitor interactions）中，本地与外来动物的资源利用广度，以及二者间的资源分配情况，通常以被用作资源的（共享）植物物种数量来估算。然而已有研究表明，访花者能否利用植物资源，会受到功能性花部性状（functional floral traits）的限制，比如形态障碍、吸引或排斥性化学信号。每一项与生态相关的性状，均可被视为哈钦森n维超体积（Hutchinsonian n-dimensional hypervolume）的一个维度，该超体积用于表征某一物种可利用的表型范围。
2. 本研究量化了由本地与外来访花者可利用的花部性状所定义的n维超体积（后文简称利用空间（exploited space, ES））的大小与重叠度。在美国受严重生物入侵的夏威夷火山国家公园中，我们对40种本地与外来植物开展了表型分型，并记录了其访花互作情况。为量化利用空间的大小与重叠度，我们采用了动态范围盒（dynamic range boxes, dynRB）分析方法。
3. 平均而言，外来访花者的资源利用泛化程度高于本地访花者，其利用空间（ES）也更大，这一点还可从外来开花植物上未观测到本地访花者这一现象得到佐证。具体而言，基于花部气味释放性状的利用空间，在外来访花者群体中显著大于本地访花者。本地与外来动物的利用空间扩张不均衡，导致了花部利用空间的重叠模式呈不对称性：外来访花者仅与本地访花者共享自身小部分的利用空间，却占据了本地访花者大部分的利用空间。
4. 本地与外来访花者在资源利用上的不对称性，暗示外来访花者在资源利用方面具备潜在优势，这或可解释其在夏威夷生态系统中的入侵成功态势。预测中外来动植物的分布范围扩张，将进一步加剧本地动物面临的资源竞争并降低资源可获得性，这可能导致本地物种种群进一步衰退，并对夏威夷生态系统构成愈发严峻的威胁。