暖化和乾旱對大豆表現與害蟲（蚜蟲）、害蟲保護者（螞蟻）、害蟲天敵（瓢蟲）互動關係的影響

Abstract

氣候變遷(如暖化和乾旱)在本世紀會更加顯著，但它們對糧食安全（如作物生產）和作物上物種交互作用（如食草動物、共生、捕食和敵對關係）的影響有待釐清。為回答以上這些問題，本研究探討兩種氣候變遷事件（暖化和乾旱）是否會交互影響 1）作物的生長和生產，以及 2）作物上的物種關係（例如共生和捕食）。本研究著重在臺灣的作物系統，實驗物種包括大豆植株 (Glycine max)、蚜蟲 (Aphis glycines)、瓢蟲 (Cheilomenes sexmaculata) 和螞蟻 (Anoplolepis gracilipes)。我們的室內實驗為 2×2×2×2 的複因子實驗設計，實驗處理包含溫度（控制/+3°C 升溫）、土壤含水量（控制/乾旱）、螞蟻（存在/不存在）和瓢蟲（存在/不存在），每種處理組合皆包含用絹網圈養的大豆植物及蚜蟲。我們記錄的數據包括作物表現、蚜蟲數量以及螞蟻和瓢蟲的死亡率。實驗結果顯示：1）暖化和乾旱常會交互影響物種關係與作物的生長和生產，暗示著重在個別氣候變遷因子的評估可能無法反映真實的作物反應。2）在暖化下，瓢蟲可以顯著地抑制蚜蟲的數量，暗示暖化可以加強天敵（瓢蟲）控制害蟲（蚜蟲）的生物防治效果。3）在暖化下，瓢蟲的存在會增加螞蟻的死亡率，暗示暖化可能會加劇瓢蟲與螞蟻的敵對關係（瓢蟲捕食害蟲vs.螞蟻保護害蟲並與其共生）。根據以上實驗結果，本研究建議評估糧食安全時應考慮非生物（氣候變遷）和生物（物種關係）因子間的交互作用。

Climate change events, such as warming and drought, will occur more often in this century, but their interactive effects on food security (e.g., crop production) and species interactions (e.g., herbivory, mutualism, predation, and antagonism) remain to be investigated. To help fill this knowledge gap, this study investigated how two climate change events (warming and drought) may interactively affect 1) crop growth, defense, and production, and 2) species interactions (e.g., herbivory, mutualism, predation, and antagonism) on crop plants. Specifically, this study focused on a crop system in Taiwan, including soybean plants (Glycine max), aphids (Aphis glycines), lady beetles (Cheilomenes sexmaculata), and ants (Anoplolepis gracilipes). We conducted a laboratory experiment with a 2×2×2×2 factorial design, including the temperature (control/+3°C warming), soil water content (control/drought), ant (presence/absence), and lady beetle (presence/absence) treatments. Note that each replicate of a treatment combination at least had aphids on a caged soybean plant. We recorded crop performance, aphid populations, and ant and lady beetle mortality. The results show the following: 1) Warming and drought commonly interacted with each other and species interactions, consequently affecting crop growth and production. This suggests that an estimation on crop production based on individual factors only may not reflect the reality. 2) Warming enhanced the suppression of aphid populations by lady beetles, implying that biocontrol of pests (aphids) by natural enemies (lady beetles) may become more efficient under warming. 3) Under warming, ant mortality increased with lady beetle presence, suggesting that warming may intensify the antagonism between lady beetles and ants (i.e., predation on pests vs. mutualism with pests). Taken together, the results suggest that evaluating food security this century should consider the interplay between abiotic (climate change) and biotic (species interaction) factors.