热带东太平洋中上层头足类近缘种营养生态位分化及共存机制

Investigating the niche patterns and coexistence mechanisms of the sympatric closely related species is vital for understanding their evolution of behavior and environmental adaptation, and is a research hotspot in behavioral ecology. The cephalopods are typical mollusks of marine ecosystems, which have unique biological characteristics and life history strategies. They are ideal groups for testing the theories of resource utilization and interspecific interaction in the sympatric closely related species. In this project, taking feeding behavior as the point of penetration, the jumbo flying squid (Dosidicus gigas) and the purpleback flying squid (Sthenoteuthis oualaniensis), which have sympatric distribution in the eastern tropical Pacific, will be selected as research objects. Based on the gut content analysis and the applications of multiple biogeochemical tracers, the food resource utilization, interspecific competition, and trophic niche overlap and separation of these two species will be quantified from different time scales. Using comparative study of the coexistence mechanisms of two species from different regions, the inter- and intra-specific trophic niche partitioning and resource redistribution will be studied, as well as the relationships with marine environmental factors, with the purpose of testing and expanding the coexistence mechanisms of the sympatric closely related species. The results will be beneficial to the mechanisms of diversity maintenance and habitat expansion for cephalopods, be helpful in promoting our ability to predict and analyze population dynamics, and furthermore, provide a theoretical basis for sustainable development and scientific management.

研究同域近缘种生态位格局和共存机制对理解物种行为进化及环境适应具有重要意义，是行为生态学研究的热点科学问题。头足类是海洋生态系统特有的软体动物，具有独特的生物学特性和生活史对策，是检验同域近缘种资源利用和种间互作有关理论的理想类群。本项目以摄食行为作为切入点，选取热带东太平洋同域分布的中上层柔鱼科头足类近缘种茎柔鱼和鸢乌贼为研究对象，利用胃含物分析和多种生物地球化学示踪标记，从不同时间尺度量化分析两种头足类对食物资源的利用方式、竞争程度、营养生态位的重叠和分离关系。通过开展不同海域二者在自然生境中竞争、共存机制的比较研究，揭示种内和种间在不同海域内的营养生态位分化与资源再分，及其与海洋环境因子的相关性，检验和拓展同域近缘种共存机制的相关理论。研究成果可加深对头足类多样性维持机制和栖息地分布拓展机理的理解，提高种群动态的预测和分析能力，为资源可持续开发和科学管理提供理论依据。

由于进化选择的压力，同域共存的近缘种生活史对策会存在一定差异，这是物种相互竞争的产物。因此，研究同域近缘种生态位格局和共存机制对理解物种行为进化及环境适应具有重要意义。本项目在摄食生态学的理论框架下，以东南太平洋同海域分布的大洋性头足类茎柔鱼和鸢乌贼为研究对象，通过对胃含物、稳定同位素、脂肪酸组成、摄食器官形态和肠道微生物群落组成分析，探究生活史过程大洋性头足类的摄食策略及其变化规律，在此基础上解析两种头足类的营养生态位分化及竞争程度，进而揭示其共存机制。重要结果：1）同一海域不同体型的茎柔鱼在空间及食物资源利用上具有差异，并与其摄食器官的生长有关。较大的个体倾向于摄食更深层及个体较小的食物，以优化食物捕获成本及能量收益有利于减小种内竞争；2）不同海域茎柔鱼摄食策略具有空间异质性，可分为两种营养模式，分别利用大洋食物网或近岸-大洋食物网为主要食物来源，并形成差异化的营养生态位，体现了头足类摄食行为对环境的适应；3）茎柔鱼和鸢乌贼胃含物组成具有显著差异，主要体现在鱼类的种类组成和个数百分比上，必需脂肪酸和稳定同位素结果显示相同体型的茎柔鱼和鸢乌贼食物来源不同，但营养级相近，且摄食空间相似，二者营养生态位重叠面积低于89%，说明茎柔鱼和鸢乌贼通过食性特化和营养生态位分化，降低种间竞争，形成平衡而共存，并且对异常气候呈现协同响应。研究成果加深了对大洋性头足类多样性维持机理和种群动态机制，同时拓展了短生命周期海洋动物共存机制的相关理论。