利用生态化学计量特征研究鱼类入侵机制：以豹纹脂身鲶为例

Biological invasion has been one of the main threats to aquatic ecosystems. Understanding the mechanism on invasion success will be favorable for ecological restoration. The input of nitrogen and phosphorus caused by anthropogenic activities is known as an important driving factor, which can facilitate the invasion of aquatic alien species. However, unlike invasive plants, aquatic animals are indirectly affected by nitrogen and phosphorus enrichment through the food chain in aquatic ecosystems, suggested that the mechanism of fish invasion cannot be simply explained by fluctuating resource availability hypothesis. In this project, we use Pterygoplichthys pardalis, which is an invasive detritivorous fish with high body phosphorus content, as model organism to explore whether ecological stoichiometry could explain the mechanism of fish invasion. To this end, an in-situ experiments was conducted to investigate the spatial variation of stoichiometric traits of P. pardalis responding to the phosphorus availability variation. Also, a common garden experiment is carried out to explore whether stoichiometric traits of P. pardalis had evolved to adapt the variation of phosphorus availability in drainages. Additionally, a pair-wise study is conducted to examine whether stoichiometric traits of P. pardalis was more plastic relative to native fishes and non-native Pterygoplichthys fishes in the condition where phosphorus availability is fluctuating. Finally, we clarify the impact of adaption of stoichiometric traits on the success of fish invasion. These results will be favorable for understanding the relationship between biogeochemical cycling and ecosystem invisibility and developing management strategies for aquatic ecosystems, as well as provide basic data for risk assessment of non-native aquatic species.

外来物种入侵是水生生态系统的主要威胁之一，研究入侵机制对生态系统修复有重要的指导意义。人类活动导致水体氮磷元素输入量增加是外来水生生物入侵的重要诱因。但与水生入侵植物不同，水体氮磷元素主要通过食物链间接地影响入侵鱼类，暗示着鱼类入侵机制不能简单的用资源波动假说来解释。本项目从生态化学计量学的视角出发，以机体磷含量高的碎屑食性入侵鱼类豹纹脂身鲶为研究对象，通过野外原位实验，探讨豹纹脂身鲇化学计量特征对磷可用性变化的空间变异格局；通过同质园实验明确豹纹脂身鲇对磷可用性变化的适应性；比较豹纹脂身鲶与土著和及非入侵近缘种对磷可用性变化响应的差异，明确豹纹脂身鲶的化学计量特征对磷可用性变化的可塑性强度。阐明外来鱼类化学计量特征适应性在其入侵成功中的作用。本项目研究结果可加深对元素生物地球化学循环与生态系统可入侵性的关系的认识，为外来物种风险评估和生态系统管理提供数据和理论支持。

本项目通过野外原位和室内控制实验相结合的方法，旨在探讨豹纹脂身鲶的的化学计量特的可塑性是否是其入侵成功的原因，主要研究内容包括水体养分富集对豹纹脂身鲶生活史的影响、豹纹脂身鲶及其生态位相似种本地鲮鱼对水体氮磷增加的响应、不同地理种群豹纹脂身鲶化学计量特征的空间变异以及该入侵鱼类与生态位相似种对食物中磷增加响应的差异。结果表明豹纹脂身鲶对磷元素具有较高的利用率，主要表现为排泄到水体中的总磷相对鲮鱼低，水体中营养元素增加能够影响豹纹脂身鲶的性成熟年龄和大小，从而影响种群的扩散。豹纹脂身鲶元素在各部位的分配、吸收和排泄存在明显的空间变异，说明该鱼的生理活动并非处于严格的内稳态调节状态。豹纹脂身鲶对氮和磷的矿化和固定作用存在生态系统特异性，这一结论是对翼甲鲶属鱼类能够影响水生生态系统养分循环的观点的拓展。豹纹脂身鲶身体碳氮磷钙含量与其生态位相似的鲮鱼、鲤鱼、齐氏罗非鱼相近，对氨氮和可溶性磷的排泄率相似，但对氮磷的吸收率小于这三种鱼，说明豹纹脂身鲶对这两种营养元素的转化率较高。这些初步的研究结果表明豹纹脂身鲶生活史特征和化学计量特征对生态系统中元素变化有一定的适应性，可能是其入侵成功的原因之一，同时也表明了该鱼对生态系统的养分循环的影响存在生态系统特异性，为制定个性化的外来鱼类防控方案提供了技术支持。