DISSERTATION RESEARCH: Inter-strain variation and evolution of resistance to phytochemicals in the bumblebee trypanosome parasite, Crithidia bombi

动物授粉维持了生态系统的生物多样性，每年对世界农业的价值为2150亿美元。大黄蜂和其他野生传粉者使野生植物物种得以繁殖，每年为美国粮食生产贡献30亿美元;如果蜜蜂种群继续崩溃，大黄蜂的重要性可能会增加。然而，寄生虫导致美国大黄蜂种群减少高达96%。植物产生一系列化学物质，称为“植物化学物质”，可以保护植物免受食草动物和病原体的侵害。这些化学物质可以是有效的抗菌剂;它们用于传统和现代药物，并赋予草药和香料以味觉和食物保存特性。蜜蜂消耗的抗菌花蜜化学品可以减少传粉者的感染，但也可能选择对普通化学品有抗性的蜜蜂寄生虫，从而失去药用价值。该项目将提高对花卉景观如何影响的理解，并可用于减少传粉者疾病。这项工作将使用熊蜂寄生虫，Crithidia bombi，以确定植物化学物质如何影响寄生虫的生长和进化，特别是：（1）菌株不同的植物化学抗性？实验室数据表明，植物化学品摄入的影响取决于蜜蜂感染的寄生虫菌株。这种变化可能反映或允许差异应变健身响应常见的花化学型。本试验将测试8种花蜜植物化学物质对4种C.孟买菌株。(2)菌株能进化出对单个植物化学物质的抗性吗？慢性植物化学品暴露可以选择耐受基因型，从而减少传粉者实现的药用效果。实验将评估植物化学物质的生长抑制作用是否在4周的植物化学物质暴露中下降。(3)植物化学混合物会减缓抗性的进化吗？在自然界中，传粉者遇到的植物化学物质是混合物而不是单一化合物。在农业和临床研究中，当寄生虫同时暴露于多种化学物质时，抗性的进化就会延迟，就像蜜蜂在不同的景观中觅食时一样。本项目将测试C.当这种寄生虫暴露于植物化学混合物而不是单一化合物时，bombi会发育迟缓。研究结果将产生关于植物与动物病原体的相互作用如何影响传粉者健康的假设，并提出使用植物化学物质来减轻传粉者下降的策略。

Animal pollination maintains ecosystem biodiversity and is valued at $215B/year to world agriculture. Bumblebees and other wild pollinators enable reproduction of wild plant species and contribute $3B/year to US food production; bumblebees may increase in importance if honeybee populations continue to collapse. However, parasites have contributed to US bumblebee population decreases of up to 96%. Plants produce an arsenal of chemicals, termed 'phytochemicals', that confer protection against herbivores and pathogens. These chemicals can be potent antimicrobials; they are used in traditional and modern medicines and confer herbs and spices with gustatory and food-preserving properties. Antimicrobial nectar chemicals consumed by bees could reduce pollinator infection, but might also select for bee parasites that are resistant to common chemicals, which would then lose medicinal value. This project will enhance understanding of how floral landscapes affect and could be manipulated to reduce pollinator disease. This work will use a bumblebee parasite, Crithidia bombi, to determine how phytochemicals affect parasite growth and evolution, specifically: (1) Do strains vary in phytochemical resistance? Laboratory data suggest that effects of phytochemical ingestion depend on the parasite strain with which bees are infected. Such variation may reflect or allow differential strain fitness in response to common floral chemotypes. The proposed experiments will test the effects of 8 nectar phytochemicals on 4 C. bombi strains. (2) Can strains evolve resistance to individual phytochemicals? Chronic phytochemical exposure could select for tolerant genotypes, thereby reducing medicinal effects realized by pollinators. Experiments will evaluate whether growth-inhibiting effects of phytochemicals decrease over 4 weeks of phytochemical exposure. (3) Do phytochemical blends slow the evolution of resistance? In nature, pollinators encounter phytochemicals in blends rather than single compounds. In agricultural and clinical studies, evolution of resistance is delayed when parasites are simultaneously exposed to multiple chemicals, as would occur when bees forage in diverse landscapes. This project will test whether phytochemical resistance in C. bombi is retarded when the parasite is exposed to phytochemical blends rather than single compounds. Results will generate hypotheses about how plant interactions with animal pathogens influence pollinator health; and suggest strategies for using phytochemicals to mitigate pollinator decline.