Understanding the mechanisms underlying the invasion success or failure of alien species can help to predict future invasions and cope with the invaders. The biotic resistance hypothesis posits that diverse communities are more resistant to invasion. While many studies have examined this hypothesis, the majority of them have focused on the relationship between alien and native species richness in plant communities, and results have often been inconsistent. In southern China, many rivers have been invaded by alien fish species, providing an opportunity to test the resistance of native fish communities to alien fish invasions. Using survey data for 60,155 freshwater fish collected from five main rivers of southern China for 3 years, we assessed the relationships between native fish richness and the richness and biomass of alien fishes at river and reach spatial scales, respectively. Based on two manipulative experiments, we further examined the impact of native fish richness on habitat selection and the reproductive ability of an exotic model species Coptodon zillii. We found no apparent relationship between alien and native fish richness, whereas the biomass of alien fish significantly decreased with increasing native fish richness. In experiments, C. zillii preferred to invade those habitats that had low native fish richness, given evenly distributed food resources; reproduction of C. zillii was strongly depressed by a native carnivorous fish Channa maculata. Together, our results indicate that native fish diversity can continue to provide biotic resistance to alien fish species in terms of limiting their growth, habitat selection, and reproduction when these aliens have successfully invaded southern China. We thus advocate for fish biodiversity conservation, especially for key species, to mitigate against the population development and ecological impact of alien fish species.
理解外来物种入侵成功或失败的机制有助于预测将来的入侵和应对已发生的入侵。生物抗性假说认为，多样性越高的群落越能抵抗外来物种入侵。虽然诸多研究对这一假设进行了检验，但是它们主要聚焦于植物群落，分析外来物种丰富度和本地物种丰富度之间的相关关系，且结果往往不尽相同。在中国华南地区很多河流已经被外来鱼类入侵，这为检验鱼类群落多样性对外来鱼类入侵的抗性作用提供了机会。本研究基于华南地区5条主要河流连续3年采集的60155条淡水鱼类数据，在河流和河段尺度上评估了本地鱼类丰富度与外来鱼类丰富度和生物量的关系。通过开展两个控制实验，研究进一步分析了本地鱼类丰富度对典型入侵物种齐氏罗非鱼(Coptodon zillii)的栖息地选择和繁殖能力的影响。调查结果显示，外来鱼类和本地鱼类的丰富度之间没有明显的相关性，而外来鱼类的生物量随着本地鱼类丰富度的增加而显著降低。实验结果表明，在食物资源分布均匀的情况下，齐氏罗非鱼偏好入侵鱼类丰富度较低的栖息地；齐氏罗非鱼的繁殖力受到本地肉食性鱼类斑鳢(Channa maculata)的严重抑制。本研究的结果表明，本地鱼类的多样性通过限制生长、栖息地选择和降低繁殖力持续对成功入侵中国华南地区的外来鱼类提供生物抗性。因此，保护鱼类生物多样性，特别是保护关键土著物种，对于抑制外来鱼类的种群增长、降低其生态影响具有重要意义。.
Keywords: biological invasions; biotic resistance; fish species; rivers; southern China; species richness.
© 2023 The Ecological Society of America.