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

9902301Simpson and Larkin蜜蜂属（Callandrena）是一个新世界的亚属，在蜜蜂属中有大约80种，是最大的蜜蜂属，在全世界有超过1200种被描述。DNA序列数据的初步分析对目前对该亚属的认识提出了质疑；物种关系与以前基于形态学的观点不同，其他亚属的成员显然是嵌套在Callandrena本身的系统发育中。研究生Leah Larkin，在德克萨斯大学Beryl Simpson博士的指导下，将研究这群蜜蜂的系统发育，强调线粒体和核基因序列是数据的主要来源，从墨西哥和美国的野外工作中收集了尽可能多的物种样本。对进化关系（系统发育）的估计结果将提供对一大群北美蜜蜂的更好理解。并将有助于形成目前缺乏的安德列娜整体的系统发育。从系统发育中，人们可以推断出哪些形态特征变化太大而无法进行分类，这些信息可能适用于其他蜂群的研究。此外，系统发育将允许进一步研究行为和适应，包括季节活动，巢结构和巢寄生虫。Callandrena亚属也被认为是研究蜜蜂在花粉觅食过程中饮食选择进化的一个模型系统，但如果没有健全的系统发育来指导宿主转移和变化方向的解释，这些行为的进化变化无法进行分析。蜜蜂从花中收集花粉来提供它们的巢穴，并在此过程中表现出一系列寄主植物的特异性，从通用型（众多和不同的植物物种，称为多聚型）到专一型（少数物种，通常在一个植物家族中，称为寡聚型）到罕见的单聚型（使用单一植物物种）。虽然这种行为类似于食草昆虫的寄主选择，但人们对其进化知之甚少。我们将在墨西哥和美国实地研究许多种Callandrena的花粉选择，并从主要收藏的博物馆蜜蜂标本的花粉负荷分析中推断。这项研究将是第一个在蜜蜂进化背景下彻底评估花粉寄主选择的研究。这项研究将提高对蜜蜂行为进化和食草动物进化的理解。

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.