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.

入侵生物学的核心研究议题之一，在于阐明与物种引种成功相关的性状特征。绝大多数相关研究均在入侵区域内评估这些性状，仅有少数研究将外来物种与其本土区域内的潜在入侵类群库进行对比分析。本研究聚焦于生态位宽度假说（niche-breadth hypothesis）：该假说常被援引却极少得到实证检验，其核心观点为泛化种更易成功引种，因为它们能够在多样的环境条件下存活繁衍。依托通过苏伊士运河大量热带物种入侵地中海的莱塞普斯迁徙（Lessepsian migration）现象，本研究将红海的被囊动物（ascidians）定义为潜在入侵类群库。我们构建了专属的附着板（settlement plate），每块板均对应6种不同的生态位，用于评估被囊动物的生态位宽度，并将其部署在本土区域与入侵区域的相似生境中。针对附着板上发现的每一个物种，我们分别评估其个体丰度、演替阶段中的相对丰度以及生态位宽度，随后开展两组对比分析：（1）红海已知已入侵地中海的莱塞普斯物种（Lessepsian species）与尚未在地中海被记录的非莱塞普斯物种；（2）地中海的外来物种与本土物种。在红海附着板上发现的莱塞普斯被囊动物，其生态位宽度显著宽于非莱塞普斯被囊动物，这一结果支持了本土区域内的生态位宽度假说。莱塞普斯物种与非莱塞普斯物种在个体丰度及演替阶段特征上未表现出显著差异。在地中海区域，外来物种在附着板的物种数量上占据绝对优势，这使得我们无法对入侵区域内外来物种与本土物种的生态位宽度开展严谨的对比分析。综上，本研究以红海被囊动物作为潜在入侵类群库，获得了支持本土区域内生态位宽度假说的明确实证证据。我们提出，若仅在入侵区域内开展基于性状的入侵生物学研究，这类模式往往会被掩盖。本研究结果表明，对物种在本土区域内的生态位宽度进行量化，将有助于提升入侵潜力评估的准确性。