POWRE: Structural Specializations of Protea Flowers and their Role in the Biology of African Sugarbirds: A Solution to Dilution?

POWRE：普罗蒂亚花的结构特化及其在非洲糖鸟生物学中的作用：稀释的解决方案？

• 批准号: 9973921
• 负责人: Carol Beuchat
• 金额: $ 18.32万
• 依托单位: University of Arizona
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-08-01 至 2002-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9973921&HistoricalAwards=false
• 关键词: POWRE; Structural; Specializations; Protea; Flowers

There are many examples of plant-pollinator relationships in which one or both of the participants exhibit some degree of specialization. Many species of plants, for example, have flowers with long corollas that are suited to visitation by hummingbirds, but which exclude other animals such as bees. Little is known about pollination systems in the Cape Floral Kingdom of southern-most Africa. The African Cape is one of the richest areas in the world botanically, and although many of its species rely primarily on birds for pollination, its avian diversity is exceptionally low. There are only nine species of birds on which over 400 species of plants depend for pollination. Most conspicuous among these is the Cape sugarbird (Promerops cafer), which is found only in South Africa. It is a medium-sized (35 g), nectar-feeding bird that has a close relationship with plants in the family Proteaceae, and especially with species in the genus Protea, of which at least 33 are bird-pollinated. The Cape proteas produce large, compound inflorescences with copious nectar that is the major food resource of Cape sugarbirds during their winter breeding season. Winter is the rainy season in the African Cape, so a problem faced by sugarbirds is dilution of Protea nectar by rain, but not all species of Protea are equally vulnerable. Nectar of proteas with large bowl- or saucer-shaped inflorescences is most readily diluted by rain. Some species of proteas, however, produce flowers that have densely furred outer bracts that never open fully (the so-called "bearded" proteas). In these, the concentration of the nectar remains virtually unchanged by even heavy rain.Anecdotal accounts in the literature and personal observations suggest that areas most favored by Cape sugarbirds for breeding also tend to have significant stands of at least one species of bearded Protea. From the perspective of the bird, this would ensure a reliable, high quality food source at a time when its energy requirements are very high due to reproduction and low temperature, and its foraging is constrained by short days and the need to remain near the nest. For the proteas, the investment in floral structures to protect the nectar should pay off in enhanced pollinator fidelity after rains, which would facilitate pollination and high seed set.Together, the PIs are investigating the importance of the floral specializations that protect the nectar of proteas to the biology of Cape sugarbirds. Using comprehensive locality databases for both the proteas and the birds, the PI is identifying sugarbird breeding areas as well as habitats supporting the Protea species of interest. The PI is surveying these habitats to determine the number of breeding birds and the species of proteas present, as well as to estimate the quantity and quality of nectar available before and after rain. Behavioral observations document potential shifts in feeding behavior that might be associated with changes in nectar quality. Laboratory studies are determining the minimum nectar concentration on which sugarbirds are able to maintain body mass while energetically stressed, which will provide an indication of the degree of nectar dilution that can be tolerated by birds in the field.The results of this study will provide information about sugarbirds and proteas that might be crucial to the protection of these species in the face of increasing habitat degradation in South Africa's Western Cape, a region with one of the highest levels of biodiversity in the world.The opportunity to work in Africa arose after the PI resigned from her tenured faculty position because of inadequate infrastructural support that had crippled her research program. This project has grown out of ideas generated during a visit to South Africa that the PI took in spring 1998 to take advantage of the relative freedom of unemployment. The project is an exceptional opportunity for the PI because it blends her expertise in the biology of avian nectarivores with a chance to substantially broaden her ecological expertise. Most important, it offers the PI a way of maintaining a high level of productivity while she rebuilds her resume and searches for a suitable permanent faculty position.

有许多植物-传粉者关系的例子，其中一个或两个参与者表现出一定程度的专业化。 例如，许多种类的植物都有长花冠的花朵，适合蜂鸟的访问，但排除了其他动物，如蜜蜂。 在非洲最南部的开普花卉王国，人们对授粉系统知之甚少。 非洲开普省是世界上植物最丰富的地区之一，尽管许多物种主要依靠鸟类授粉，但其鸟类多样性非常低。 只有9种鸟类，400多种植物依靠它们授粉。 其中最引人注目的是海角糖鸟（Promerops cafer），仅在南非发现。 它是一种中等大小（35克），以花蜜为食的鸟类，与Proteaceae家族的植物关系密切，特别是Protea属的物种，其中至少有33种是鸟类授粉的。 好望角糖蜜鸟（Cape Proteas）的花序大而复杂，花蜜丰富，是冬季繁殖季节好望角糖蜜鸟的主要食物来源。 冬季是非洲开普省的雨季，因此糖鸟面临的一个问题是雨水稀释了Protea花蜜，但并非所有Protea物种都同样脆弱。 具有大碗状或碟状花序的Proteas的花蜜最容易被雨水稀释。 然而，有些种类的Proteas会产生具有浓密毛的外苞片的花朵，这些苞片从未完全开放（所谓的“胡须”Proteas）。 在这些地方，花蜜的浓度几乎保持不变，即使大雨。轶事在文献和个人的观察表明，地区最喜爱的角糖鸟繁殖也往往有显着的立场，至少有一个品种的胡子Protea。 从鸟类的角度来看，这将确保可靠，高质量的食物来源，因为繁殖和低温导致其能量需求非常高，并且其觅食受到白天短和需要留在巢附近的限制。 对于Proteas来说，花结构的投资，以保护花蜜应该在雨后增强传粉者的忠诚度，这将有利于授粉和高seedset.Together，PI正在调查保护Proteas花蜜的花的专业化的重要性，以开普糖鸟的生物学。 PI正在使用Protea和鸟类的综合地点数据库，确定糖鸟繁殖区以及支持Protea物种的栖息地。 PI正在调查这些栖息地，以确定繁殖鸟类的数量和现有的Proteas物种，以及估计降雨前后花蜜的数量和质量。 行为观察记录潜在的变化，可能与花蜜质量的变化有关的喂养行为。 实验室研究正在确定糖鸟在精力紧张的情况下能够保持体重的最低花蜜浓度，这将提供一个指示的花蜜稀释程度，可以容忍的鸟类在外地。这项研究的结果将提供有关糖鸟和蛋白酶，可能是至关重要的，以保护这些物种在面对日益恶化的栖息地在南非的西开普省是世界上生物多样性水平最高的地区之一。PI辞去终身教职后，她有机会在非洲工作，因为基础设施支持不足，削弱了她的研究计划。 这个项目是从1998年春天PI访问南非期间产生的想法中发展出来的，以利用失业的相对自由。 该项目对PI来说是一个难得的机会，因为它将她在鸟类食蜜动物生物学方面的专业知识与大幅扩展其生态专业知识的机会相结合。 最重要的是，它为PI提供了一种保持高水平生产力的方法，同时她重建了自己的简历，并寻找合适的永久教师职位。