The Effect of Ant Nests on Plant Nutrition and Selection for Extrafloral Nectaries

花外蜜腺(EFN)是位于植物叶和茎上的器官，它们分泌糖和氨基酸。目前，对于EFN的进化和维持，唯一被接受的假说是它们引诱捕食性节肢动物，特别是蚂蚁，进入植物组织，从而减少草食动物造成的损害。然而，支持这种对EFN的解释的证据喜忧参半。这项研究的目的是检验另一种假说，即营养假说，以促进该性状的进化和维持。在北美灌木相思中，EFN似乎鼓励蚂蚁在植物的根区筑巢，蚂蚁可以在那里提高土壤矿质养分浓度，并可能增加植物的适合度。一些相思树个体在底部有蚂蚁巢穴，而另一些则没有。相思树下的巢是动态的，每年夏天都会重新形成。之前在研究地点的工作已经证明，蚂蚁窝土壤含有丰富的营养物质，往往会限制植物的繁殖。这项拟议的研究使用田间和实验室实验来测试营养和保护对狭纹夜蛾适合度的相关性的相对重要性。这项研究还测试了蚂蚁巢所提供的增强的植物营养是否通过生产高质量的食物奖励来反馈给蚂蚁。这项研究的结果将为用于植物-食草动物相互作用的进化生态学的模型系统提供重要的见解。该项目还将更广泛地促进蚂蚁在干旱和半干旱生态系统中的养分分配和积累方面所发挥的作用。该项目将在实验室和温室(阿拉斯加大学费尔班克斯分校)和实地(亚利桑那州西南研究站)为一名博士生和几名本科生提供培训。将特别努力招收从未有机会到阿拉斯加州以外旅行的本地和农村本科生。该项目将拓宽生态专业学生的视野，向他们介绍一种具有高度生物多样性的新生物群，该生物群由气候挑战构成，不同于他们所在的州。

Extrafloral nectaries (EFNs) are organs located on leaves and stems of plants; they secrete sugars and amino acids. Currently, the only well-accepted hypothesis for the evolution and maintenance of EFNs is that they lure predatory arthropods, especially ants, onto plant tissues and thereby reduce the damage caused by herbivores. Evidence supporting this explanation for EFNs is mixed, however. The goal of this study is to test an alternative hypothesis, the nutrition hypothesis, for the evolution and maintenance of the trait. In the North American shrub, Acacia constricta, EFNs appear to encourage ants to nest within the rooting zone of the plant, where ants can enhance soil mineral nutrient concentrations and may increase plant fitness. Some acacia individuals have ant nests at the base and others do not. Nests under acacia are dynamic, forming anew each summer. Previous work at the study site has demonstrated that ant nest soils are enriched in nutrients that frequently limit plant reproduction. The proposed research uses field and laboratory experiments to test the relative importance of nutrition and protection to correlates of fitness for A. constricta. The research also tests whether enhanced plant nutrition, provided by ant nests, feeds back to the ants through the production of high-quality food rewards. Results from this research will contribute important insights to a model system used in the evolutionary ecology of plant-herbivore interactions. The project also will contribute more generally to the role that ants play in nutrient distribution and accumulation in arid and semi-arid ecosystems. The project will provide training for a Ph.D. student and several undergraduates in the laboratory and greenhouse (University of Alaska Fairbanks) and in the field (Southwestern Research Station, Arizona). Special effort will be made to recruit native and rural undergraduates who have never had the opportunity to travel outside the state of Alaska. The project will broaden the view of ecology students by introducing them to a new biome with high biodiversity, structured by climatic challenges unlike those of their home state.