栅藻诱导型防御的权衡策略与代价分析

Inducible defenses in plankton can prevent strong population fluctuations in bi- and tritrophic food chains and play an important role in maintaining the stability of community and trophic structure. Inducible colony formation in Scenedesmus spp. can be activated by zooplankton infochemicals; such "Scenedesmus - zooplankton"system has been developed to a well-established model system for studying inducible defenses. However, direct costs associated with inducible defenses of Scenedesmus have proved difficult to measure empirically and are still a fundamental scientific issue. Measuring the expression degree of inducible defenses of Scenedesmus under different environmental conditions is also extreme important to understand trade-off strategies of anti-grazing defenses of Scenedesmus. To explore these key issues, the proposal will conduct studies including following several parts: (1) trade-off of inducible defenses in Scenedesmus results from grazer conditions; (2) changes in the expression degree of inducible defenses in Scenedesmus after repeatedly stimulated by grazer's infochmicals; (3) quantitative relationship between expression degree of inducible defenses in Scenedesmus and resources availability in the environment; (4) trade-off between competing for resources and expression degree of inducible defenses in Scenedesmus resulted from competition (intra-specific competition and inter-specific competition); (5) influences of stresses causing by pollutants (e.g. heavy metals, chemical pollutants) and changes in water chemistry on trade-off and costs of inducible defenses in Scenedesmus. The research has important theoretic and realistic significance in developing theory of inducible defense ecology and revealing the influences of multiple environmental factors on inter-specific relationship in aquatic ecosystem.

浮游生物诱导型防御能降低种群的剧烈波动，对于维持群落和营养级结构稳定发挥重要作用。栅藻在浮游动物牧食下形成诱导型防御群体，已发展为用于研究诱导型防御的良好模式系统。但是，栅藻诱导型防御直接代价的检测还是一个尚未解决的基础科学问题，而栅藻在不同环境下诱导型防御的表达程度对于理解栅藻诱导型防御的权衡策略至关重要。为了探明这些基础科学问题，本申请项目将开展以下研究：(1)来自牧食者因素导致的栅藻诱导型防御的权衡；(2)栅藻受到牧食者信息物质连续多次刺激后诱导型防御强度的变化；(3)栅藻诱导型防御强度及代价与环境资源可得性的定量关系；(4)竞争因素（种内竞争与种间竞争）导致的栅藻在竞争资源与诱导型防御之间的权衡；(5)污染物及水质指标变动造成的环境胁迫对栅藻诱导型防御的权衡及代价影响。本研究对丰富和发展诱导型防御生态学理论以及揭示水域生态系统中多种因素对种间关系的影响具有重要的理论与实际意义。

栅藻在浮游动物牧食下形成诱导型防御群体，已发展为用于研究诱导型防御的良好模式系统。但是，栅藻诱导型防御直接代价的检测还是一个尚未解决的基础科学问题，而栅藻在不同环境下诱导型防御的表达程度对于理解栅藻诱导型防御的权衡策略至关重要。本项目的主要研究结果如下：.(1)来自牧食者因素导致的栅藻诱导型防御的权衡.通过设置枝角类的密度、年龄、生物量、摄食强度研究牧食者自身因素对栅藻诱导型防御的影响，发现栅藻诱导型防御群体形成强度与牧食者的摄食强度所指示的捕食压力直接相关，本质上取决于外界潜在捕食风险的大小。.(2)栅藻受到牧食者信息物质连续多次刺激后诱导型防御强度的变化.通过设置了两种周期的长期反复诱导模式，发现栅藻防御群体会随着多次反复的信息素刺激而削弱，且与刺激的频率和周期有显著的相关性。.(3)栅藻诱导型防御强度及代价与环境资源可得性的定量关系.通过设置不同的资源梯度，发现栅藻诱导型反牧食防御的表达依赖于充足的环境资源。当环境资源可得性降低时，栅藻的防御强度受到影响，且伴随着易于检测的直接生长代价。.(4)种间竞争导致的栅藻在获取资源与诱导型防御之间的权衡.通过与微囊藻、小球藻、硅藻、水生植物等种间竞争实验，发现栅藻在面临种间竞争和捕食风险双重压力时，防御强度削弱，说明栅藻在形成防御群体和保持单细胞利于竞争方面存在权衡策略。.(5)污染物及水质指标变动造成的环境胁迫对栅藻诱导型防御的权衡及代价影响。.通过采用重金属、化学污染物、紫外辐射、pH变化等多种环境胁迫实验，发现栅藻在环境胁迫下防御强度受到显著干扰，且存在显著的浓度相关性，同时防御代价也易于直接体现在生长性能上。. 综上所述，栅藻的诱导型防御的表达强度在综合外界环境下存在权衡，在资源不足、竞争以及环境胁迫下其防御代价易于体现。本研究对丰富和发展诱导型防御生态学理论以及揭示水域生态系统中多种因素对种间关系的影响具有重要的理论与实际意义。