Data from: Habitat niche breadth predicts invasiveness in solitary ascidians

A major focus of invasion biology is understanding the traits associated with introduction success. Most studies assess these traits in the invaded region, while only few compare non-indigenous species to the pool of potential invaders in their native region. We focused on the niche-breadth hypothesis, commonly evoked but seldom tested, which states that generalist species are more likely to become introduced since they are capable of thriving under a wide set of conditions. Based on the massive introduction of tropical species into the Mediterranean via the Suez Canal (Lessepsian migration), we defined ascidians in the Red Sea as the pool of potential invaders. We constructed unique settlement plates, each representing six different niches, to assess ascidian niche breadth, and deployed them in similar habitats in the native and invaded regions. For each species found on plates, we evaluated its abundance, relative abundance across successional stages and niche breadth, and then compared (1)species in the Red Sea known to have been introduced into the Mediterranean (Lessepsian species) and those not known from the Mediterranean (non-Lessepsian); and (2)non-indigenous and indigenous species in the Mediterranean. Lessepsian ascidians identified on plates in the Red Sea demonstrated wider niche breadth than non-Lessepsian ascidians, supporting the niche-breadth hypothesis within the native region. No differences were found between Lessepsian and non-Lessepsian species in species abundance and successional stages. In the Mediterranean, non-indigenous species numerically dominated the settlement plates. This precluded robust comparisons of niche breadth between non-indigenous and indigenous species in the invaded region. In conclusion, using Red Sea ascidians as the pool of potential invaders, we found clear evidence supporting the niche-breadth hypothesis in the native region. We suggest that such patterns may often be obscured when conducting trait-based studies in the invaded regions alone. Our findings indicate that quantifying the niche breadth of species in their native regions will improve estimates of invasiveness potential.入侵生物学 (invasion biology) 的核心研究方向之一，是解析与物种引种成功 (introduction success) 相关的性状特征。多数相关研究仅在入侵区域评估此类性状，仅有少数研究会将外来物种 (non-indigenous species) 与其原产地的潜在入侵类群库进行对比。本研究聚焦于生态位宽度假说 (niche-breadth hypothesis)——该假说虽常被援引却极少得到实证检验，其核心观点为广适性物种更易成功引种，因其能够在多样的环境条件下存活繁衍。基于通过苏伊士运河大量热带物种向地中海迁徙的莱塞普斯迁徙 (Lessepsian migration) 事件，我们将红海的被囊动物 (ascidians) 划定为潜在入侵类群库。我们定制了专属的附着基盘 (settlement plates)，每个基盘均包含六种不同的生态位 (niche)，以此评估被囊动物的生态位宽度，并将其部署在原产地与入侵区域的相似生境中。针对附着基盘上发现的每个物种，我们分别评估了其丰度、演替阶段 (successional stages) 中的相对丰度以及生态位宽度，随后开展了两项对比：(1) 红海地区已知已入侵地中海的莱塞普斯入侵物种 (Lessepsian species) 与尚未在地中海被记录的非莱塞普斯物种 (non-Lessepsian species)；(2) 地中海地区的外来物种与土著物种 (indigenous species)。在红海的附着基盘上发现的莱塞普斯入侵被囊动物，其生态位宽度显著宽于非莱塞普斯被囊动物，这一结果证实了原产地范围内的生态位宽度假说。在物种丰度与演替阶段方面，莱塞普斯与非莱塞普斯物种未表现出显著差异。在地中海区域，外来物种在附着基盘上占据了数量上的绝对优势，这使得我们无法对入侵区域的外来物种与土著物种的生态位宽度开展可靠对比。综上，以红海被囊动物作为潜在入侵类群库，我们找到了明确的实证证据支持原产地范围内的生态位宽度假说。我们认为，若仅在入侵区域开展基于性状的入侵生物学研究，此类模式往往会被掩盖。本研究结果表明，量化物种在原产地的生态位宽度，将有助于提升入侵潜力 (invasiveness potential) 评估的准确性。