DISSERTATION RESEARCH: Direct and indirect effects of invasive species on plant-seed disperser mutualisms

许多植物依靠吃水果的动物来传播种子。这种相互作用对植物和动物都有好处，因此被称为互惠共生。由于种子传播可以决定植物的丰度和范围，因此种子传播的相互作用可以使以该植物为食物或住所的其他物种受益，从而影响整个景观的生物多样性模式。人类将新物种引入栖息地可能会破坏种子传播的互惠关系，但我们对这种破坏可能会影响其他相关物种知之甚少。该项目将测试破坏阿根廷巴塔哥尼亚北温带森林中一种重要的种子传播互惠关系的更大生态影响。槲寄生Tristerix corymbosus是蜂鸟Sephanoides sephaniodes的唯一冬季花蜜来源，它全年都在该地区，反过来又负责该地区近20%的特有木本植物群的授粉。槲寄生的种子只由有袋动物穴居动物传播。在通过有袋动物的肠道后，大部分排出的种子会附着在猕猴的树枝上。猕猴是森林中最丰富的下层灌木，也是槲寄生最常见的寄主。由于这些密切的生态关系，外来物种减少了猕猴的密度，也减少了槲寄生、蜂鸟和有袋动物的丰度，从而改变了整个森林。这个项目将测试外来黄蜂德国黄蜂和外来有蹄类动物对马基种群和森林中相关物种的影响。生物多样性的保护对人类社会具有重要意义，而对生物多样性的主要威胁之一是人类在世界范围内偶然和故意引入新物种。这项研究将进一步加深我们对引进物种如何影响生物多样性的理解，并有助于指导管理以保护生物多样性。这项研究还将加强国际科学合作和培训。

Many plants rely on fruit-eating animals to disperse their seeds. This interaction benefits both the plant and the animal and is therefore termed a mutualism. Because seed dispersal can determine the abundance and range of the plant, seed dispersal mutualisms can benefit other species that use the plant for food or shelter and thus affect patterns of biodiversity across the landscape. The introduction by humans of new species into a habitat can disrupt seed dispersal mutualisms, but we know little about such disruptions may affect other, interrelated species. This project will test the larger ecological effects of disruption of an important seed dispersal mutualism in the northern temperate forests of Patagonia in Argentina. The mistletoe Tristerix corymbosus is the sole winter nectar source for the hummingbird Sephanoides sephaniodes, which remains in the region year-round and is in turn responsible for the pollination of nearly 20% of the endemic woody flora in the region. The seeds of the mistletoe are dispersed exclusively by the marsupial Dromiciops gliroides. After passing through the gut of the marsupial, most of the defecated seeds stick to branches of maqui, Aristotelia chilensis, the most abundant understory shrub in the forest and the most common host for the mistletoe. Because of these close ecological relationships, exotic species that reduce the density of maqui could also reduce the abundances of the mistletoe, the hummingbird, and the marsupial, changing the forest as a whole. This project will test the effects of the exotic wasp Vespula germanica and of exotic ungulates on maqui populations and on the linked species in the forest.Conservation of biological diversity is important to human society, and one of the major threats to biodiversity are the accidental and intentional introductions of new species around the world by humans. This research will further our understanding of how introduced species can affect biodiversity and help guide management to conserve diversity. The research will also strengthen international scientific collaboration and training.