Data from: Broad and flexible stable isotope niches in invasive non-native Rattus spp. in anthropogenic and natural habitats of central eastern Madagascar

Background: Rodents of the genus Rattus are among the most pervasive and successful invasive species, causing major vicissitudes in native ecological communities. A broad and flexible generalist diet has been suggested as key to the invasion success of Rattus spp. Here, we use an indirect approach to better understand foraging niche width, plasticity, and overlap within and between introduced Rattus spp. in anthropogenic habitats and natural humid forests of Madagascar. Results: Based on stable carbon and nitrogen isotope values measured in hair samples of 565 individual rodents, we found that R. rattus had an extremely wide foraging niche, encompassing the isotopic space covered by a complete endemic forest-dwelling Malagasy small mammal community. Comparisons of Bayesian standard ellipses, as well as (multivariate) mixed-modeling analyses, revealed that the stable isotope niche of R. rattus tended to change seasonally and differed between natural forests and anthropogenic habitats, indicating plasticity in feeding niches. In co-occurrence, R. rattus and R. norvegicus partitioned feeding niches. Isotopic mismatch of signatures of individual R. rattus and the habitat in which they were captured, indicate frequent dispersal movements for this species between natural forest and anthropogenic habitats. Conclusions: Since R. rattus are known to transmit a number of zoonoses, potentially affecting communities of endemic small mammals, as well as humans, these movements presumably increase transmission potential. Our results suggest that due to their generalist diet and potential movement between natural forest and anthropogenic habitats, Rattus spp. might affect native forest-dependent Malagasy rodents as competitors, predators, and disease vectors. The combination of these effects helps explain the invasion success of Rattus spp. and the detrimental effects of this genus on the endemic Malagasy rodent fauna.

研究背景：鼠属（Rattus）啮齿动物是全球分布最广、入侵成功性最强的外来入侵类群之一，会对本土生态群落造成显著剧变。学界普遍认为，宽泛且灵活的广食性食谱是鼠属物种得以成功入侵的核心关键。本研究采用间接研究方法，旨在深入解析马达加斯加人为栖息地与天然湿润林中，引入性鼠属物种内部及不同物种间的觅食生态位宽度、生态位可塑性及种间生态位重叠情况。
研究结果：基于对565只啮齿动物毛发样本的稳定碳氮同位素检测数据，本研究发现黑家鼠（Rattus rattus）拥有极宽的觅食生态位，其同位素空间覆盖范围完整涵盖了马达加斯加本土森林栖息小型哺乳动物群落的整体同位素空间。通过贝叶斯标准椭圆比较及多变量混合模型分析，结果显示黑家鼠的稳定同位素生态位呈现季节性波动，且在天然森林与人为栖息地间存在显著差异，表明其觅食生态位具有较强的可塑性。在同域共存场景下，黑家鼠与褐家鼠（Rattus norvegicus）实现了明确的觅食生态位分化。个体黑家鼠的同位素特征与其捕获生境存在明显不匹配，这提示该物种常在天然森林与人为栖息地之间发生频繁的扩散活动。
研究结论：已知黑家鼠可传播多种人畜共患病，可能对本土小型哺乳动物群落及人类健康构成潜在威胁，而上述跨生境扩散活动或会进一步提升疾病传播风险。本研究结果表明，鼠属物种凭借其广食性食谱，以及在天然森林与人为栖息地间的潜在扩散能力，可通过竞争者、捕食者及疾病传播媒介的多重身份，对依赖森林栖息的马达加斯加本土啮齿动物产生负面影响。上述多重效应的共同作用，正是鼠属物种得以成功入侵，以及该类群对马达加斯加本土啮齿动物区系造成有害影响的核心解释。