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方向之一，是解析与物种引种成功相关的性状。现有多数相关研究均在入侵区域内评估这些性状，仅有少数研究会将外来物种与其原生分布区的潜在入侵类群池进行对比分析。本研究聚焦于生态位宽度假说（niche-breadth hypothesis）——该假说虽常被援引却极少得到实证检验，其核心观点为泛化种更易实现成功引种，因其可在多样环境条件下存活繁衍。依托通过苏伊士运河（莱塞普斯迁移，Lessepsian migration）实现的热带物种大规模向地中海入侵事件，本研究将红海的被囊动物（ascidians）定义为潜在入侵类群池。我们构建了兼具六种不同生态位类型的专属附着基（settlement plates）以评估被囊动物的生态位宽度，并将其分别部署在原生分布区与入侵区域的相似生境中。针对附着基上采集到的每个物种，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：（1）红海已知已入侵地中海的被囊动物（莱塞普斯物种）与未在地中海被记录的物种（非莱塞普斯物种）；（2）地中海区域的外来物种与土著物种。红海附着基上采集到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，这一结果在原生分布区内验证了生态位宽度假说。莱塞普斯与非莱塞普斯物种在个体丰度与演替阶段分布上未呈现显著差异。在地中海区域，外来物种在附着基上的个体数量占据绝对优势，这使得我们无法对入侵区域内外来物种与土著物种的生态位宽度开展严谨对比。综上，本研究以红海被囊动物作为潜在入侵类群池，在原生分布区内找到了支持生态位宽度假说的明确实证。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，往往会掩盖这类关键规律。本研究结果表明，量化物种在原生分布区的生态位宽度，可有效提升入侵潜力评估的准确性。