人類世下的生態系損害、生物適應及生物防治

Abstract

在人類世（Anthropocene）中，人類活動已成為塑造地球生態系統的主導力量，驅動著空間與時間尺度上前所未有的環境變化。氣候快速暖化、降水模式改變及土地利用變化等因素，共同重塑了物種生存的非生物環境，產生新的選擇壓力並重組生物互動與生態群落。農業生態系統為受影響的重要系統之一，了解受影響下的植物-草食性昆蟲-天敵三營養層互動，對於理解生物防治和作物生產力具有關鍵意義。目前這些互動在快速、多維環境變化下的反應仍不清楚，因此本論文從三個部分探討環境快速變化對植物-昆蟲互動及生物防治的影響： 第一部分（第二章）研究植物葉片構造的物理防禦（毛狀體）對蚜蟲偏好及天敵捕食效率的影響。本研究透過同側葉片實驗，發現蚜蟲偏好葉片背面（65.3%）勝於正面（23.7%），主要受到葉片表面結構的影響，例如背面有較高的毛狀體密度；瓢蟲在正面葉片結構下捕食蚜蟲的效率較背面葉片結構下高出 84.5%，顯示高密度毛狀體會降低瓢蟲的捕食率。族群成長模型進一步證明，正面表面結構增強了瓢蟲對蚜蟲的抑制效果。以上結果證明植物結構特徵可影響三營養層互動，因此本研究建議未來的作物育種與害蟲管理策略應考量植物結構因素。 第二部分（第三章）採用長期演化實驗，檢視蚜蟲在長期暖化（+2°C）與捕食壓力下歷經 100 世代的演化反應。結果顯示「演化拯救」效應：初期暖化降低蚜蟲體重與存活率，但長期壓力下（第 60–100 世代）促成適應性演化，蚜蟲恢復族群成長並增強極端高溫耐受性。雖然捕食壓力在初期會加強對蚜蟲生物量的抑制，但在長期暖化歷史下，其控制效果顯著改變。本研究進一步測試長期適應下的蚜蟲潛在危害，發現適應暖化的蚜蟲對大豆植株可造成更嚴重損害，相較於短期暴露族群，可加劇產量、植株高度及總生物量的下降。此結果顯示害蟲可透過演化快速克服生理限制，暗示現行綜合害蟲管理策略（IPM）可能低估暖化情境下的蟲害威脅。 第三部分（第四章）探討溫度與濕度如何交互影響真菌生物防治效能。此研究以含昆蟲病原菌 Aspergillus nomius 的餌劑控制疣胸琉璃蟻 (Dolichoderus thoracicus)，結果顯示菌絲生長率及分生孢子產生率會隨溫度升高而增加，而螞蟻死亡率亦隨溫度與濕度提高而增加，且真菌僅在較高溫度下發育，溫濕度升高可加速分生孢子成熟。空間分析顯示，高溫季節環境格點大多適合真菌感染，低溫季節則不利。此結果強調，理解氣候因子與生物防治效能的交互作用，對永續害蟲管理至關重要。 綜合而言，本論文揭示生物階層之間的互動與相關的生態系統服務(或損害)會隨植物構造、時間尺度與環境梯度而變化: 植物毛狀體雖能防禦大型草食動物，卻無意間為小型害蟲提供庇護；長期環境壓力下的蚜蟲展現快速演化能力，可對作物造成更大損害；微生物可用於防治入侵螞蟻，但其效能需與適當的環境條件匹配。將這些因素納入整合研究視角，不僅能更精準地理解物種如何應對人類世的快速變化，也為基礎的農業與害蟲管理策略提供指引。

In the Anthropocene, human activities have become a dominant force shaping Earth's ecosystems, driving unprecedented environmental changes across spatial and temporal scales. Rapid climate warming, altered precipitation patterns and land-use changes collectively reshape the abiotic environment of species interactions, generating novel selection pressures and reorganizing ecological communities. Agricultural ecosystems are particularly sensitive to these changes. Therefore, it is important to understand how trophic interactions among plants, herbivorous insects, and natural enemies in agroecosystems are affected, and how these changes influence biological control and crop productivity. Since the response of the trophic interactions to rapid, multifaceted environmental change remains poorly understood, this dissertation examines how rapid environmental changes affect plant-insect interactions and biological control from t the following three perspectives. The first part (Chapter 2) investigates how plant leaf structure (e.g., physical defense such as trichomes) influences aphid preference and predator foraging efficiency. Using same-side leaf experiments, this study shows that aphid preference is primarily driven by leaf surface structure, favoring the abaxial side (65.3%) over the adaxial side (23.7%), consistent with higher trichome density on the abaxial surface. Ladybird predation on aphids was 84.5% higher on the adaxial side, indicating that dense trichomes reduce predator efficiency. Population growth models further demonstrate that adaxial leaf structure enhances ladybird suppression of aphids. These findings indicate that plant structural traits mediate trophic interactions and highlight the importance of incorporating such traits into crop breeding and pest management strategies. The second part (Chapter 3) employs a long-term evolution experiment to examine aphid responses under sustained warming (+2°C) and predation pressure over 100 generations. The results reveal an “evolutionary rescue” effect: initial warming reduced aphid body mass and survival, but long-term selection (generations 60–100) led to adaptive evolution, restoring aphid population growth and enhancing aphid tolerance to extreme heat. While predation initially exerted strong top-down control, its suppressive effect on aphid biomass and dynamics changed significantly under prolonged warming. Warming-adapted aphids inflicted more severe damage on soybean plants, causing greater reductions in yield, height, and total biomass than short-term exposure populations. These results demonstrate that pests can rapidly overcome physiological constraints through adaptation, suggesting that current integrated pest management (IPM) may underestimate pest threats in a warming world. The third part (Chapter 4) explores how temperature and humidity jointly affect the efficacy of fungal biological control. Using baits containing the entomopathogenic fungus Aspergillus nomius to target the ant pest Dolichoderus thoracicus, this study shows that fungal mycelial growth and conidial production increased with temperature. Ant mortality also increased with higher temperature and humidity, and fungal development occurred only at elevated temperatures, with higher temperature and humidity accelerating conidial maturation. Spatial analysis indicates that warm-season grids are mostly suitable for fungal infection, whereas cold-season grids are less favorable. These findings highlight that understanding the interaction between climatic factors and biocontrol efficacy is critical for sustainable pest management. Overall, this dissertation demonstrates that ecological interactions and related ecosystem service (or disservices) may vary with plant structure, temporal scales, and environmental gradients: Trichomes that deter large herbivores inadvertently provide shelter for small pests, reducing predator efficiency; aphids under long-term environmental stress exhibit rapid evolutionary responses that increase crop damage, contrasting with short-term responses; and microbial biocontrol efficacy depends on precise environmental matching. Integrating these dimensions into a comprehensive research framework will improve predictions of species responses to Anthropocene environmental changes and inform the development of resilient, evidence-based agricultural and pest management strategies.