DISSERTATION RESEARCH: The Lost Herbivores: Phylogeny and Floral Host Preferences of Callandrena Bees (Hymenoptera: Andrenidae: Andrena)

9902301Simpson和Larkin Callandrena是新大陆的一个亚属，约有80种，隶属于Andrena，是最大的蜜蜂属，全世界已描述的种类超过1200种。对DNA序列数据的初步分析使人们对目前对该亚属的理解产生了怀疑；物种关系与之前基于形态的想法不同，其他亚属的成员显然嵌套在马蹄莲属本身的系统发育中。研究生Leah Larkin将在德克萨斯大学Beryl Simpson博士的指导下研究这类蜜蜂的系统发育，重点放在线粒体和核基因序列作为主要数据来源，从墨西哥和美国的田野工作中收集尽可能多的物种样本。对进化关系(系统发育)的估计将提供对一大群北美蜜蜂的更好了解，并将有助于目前缺乏的Andrena作为一个整体的系统发育。从系统发育中，人们可以推断哪些形态特征对于分类目的来说太过可变，这一信息可能适用于其他蜜蜂群体的研究。此外，系统发育将允许对行为和适应的进一步研究，包括季节性活动、巢建筑和巢寄生虫。Callandrena亚属也是研究蜜蜂觅食过程中食物选择进化的模式系统，但如果没有强大的系统发育来指导对宿主转移和变化方向的解释，这些行为的进化变化就不能进行分析。蜜蜂从花中收集花粉来供应它们的巢，在这样做的过程中表现出一系列寄主植物的专一性，从多面性(许多不同的植物种类，称为多倍性)到专业性(少数种类，通常在一个单一的植物科中，称为寡聚性)，再到罕见的单性(使用单一的植物物种)。虽然这种行为类似于食草性昆虫的寄主选择，但人们对其进化知之甚少。将在墨西哥和美国的野外研究马蹄莲属许多物种的花粉选择，并将通过分析主要收藏品中保存的博物馆蜜蜂标本的花粉含量来推断。这项研究将是第一次在进化的背景下彻底评估蜜蜂的花粉宿主选择。这项研究将提高对蜜蜂行为进化和食草动物进化的总体理解。

9902301Simpson and Larkin Callandrena is a New World subgenus of ca. 80 species in Andrena, the largest genus of bees, with over 1200 described species worldwide. Preliminary analysis of DNA sequence data casts doubt on the current understanding of the subgenus; species relationships are different from what was previously thought based on morphology, and members of other subgenera are apparently nested within the phylogeny of Callandrena itself. Graduate student Leah Larkin, under the direction of Dr. Beryl Simpson at the University of Texas, will be studying the phylogeny of this group of bees, emphasizing mitochondrial and nuclear gene sequences as primary sources of data, sampled from as many species as can be collected from field work in Mexico and the U.S. The estimate of evolutionary relationships (phylogeny) which results will provide a better understanding of a large group of North American bees, and will contribute to a phylogeny, currently lacking, of Andrena as a whole. From the phylogeny, one can infer which morphological characters are too variable for classification purposes, information which may be applicable to the study of other bee groups. Additionally, the phylogeny will permit further studies of behavior and adaptation, including seasonal activity, nest architecture, and nest parasites. The subgenus Callandrena has also served as a model system for the study of the evolution of bee diet choice in pollen foraging, but the evolutionary changes in these behaviors have not been amenable to analysis without a robust phylogeny to guide interpretation of host shifts and direction of change. Bees collect pollen from flowers to provision their nests, and in so doing exhibit a range of hostplant specificity from generalist (numerous and different plant species, called polylectic) to specialist (few species, usually within a single plant family, called oligolectic) to rare cases of monolecty (use of a single plant species). While this behavior is analogous to hostplant choice in herbivorous insects in general, its evolution is poorly understood. Pollen choice in numerous species of Callandrena will be studied in the field in Mexico and the U.S., and will be inferred from analysis of pollen loads in museum specimens of bees maintained in major collections. This study will be the first to evaluate thoroughly pollen host choice in an evolutionary context in bees. The study will improve understanding of the evolution of bee behavior and the evolution of herbivory in general.