DISSERTATION RESEARCH: Mechanisms Maintaining Coexistence of Sympatric Cytotypes in Arnica Cordifolia (Asteraceae)

多倍体，即在一个基因组中存在多个染色体副本，是构建被子植物遗传多样性的一个中心过程，但人们对其生态学意义知之甚少。少数细胞型排斥理论预测多种细胞型不应该共存；然而同域多倍体并不少见。共存机制包括：1)通过自交或孤雌生殖保证生殖；2)生境分化。关于多倍体如何影响栖息地的利用，或栖息地分化如何影响多倍体的生产和分布，人们知之甚少。本工作探讨了多年生草本植物山金车三倍体和四倍体共存的机制。三倍体的起源将使用遗传指纹技术进行评估。将确定繁殖模式以评估逃脱少数人细胞型排斥的可能性。三倍体之间的栖息地分化将被量化，相互移植实验将被用来检验三倍体在受干扰的栖息地被选择性地维持的假设。这项工作将告诉我们多倍体、孤雌生殖和生境分化对植物种群空间结构的重要性。这项研究将为多倍体和干扰在植物种群景观遗传学中的作用提供重要信息。更广泛的影响包括本科培训和对经典方法和高科技现代方法的独立研究，这是本科生通常无法获得的。

Polyploidy, the existence of multiple copies of chromosomes in a genome, is a central process structuring genetic diversity in angiosperms, yet its ecological significance is poorly understood. The minority cytotype exclusion theory predicts multiple cytotypes should not coexist; yet sympatric polyploids are not uncommon. Coexistence mechanisms include: 1) reproductive assurance via selfing or parthenogenesis and 2) habitat differentiation. Little is known about how polyploidy influences habitat use, or how habitat differentiation influences polyploid production and distribution. This work investigates the mechanisms contributing to the coexistence of triploids and tetraploids in the perennial herb, Arnica cordifolia. The origin of triploids will be assessed using genetic fingerprinting. Reproductive mode will be determined to evaluate the potential for escape from minority cytotype exclusion. Habitat differentiation between ploidies will be quantified and reciprocal transplant experiments will be used to test the hypothesis that triploids are being selectively maintained in disturbed habitat. This work will inform us of the importance of polyploidy, parthenogenesis and habitat differentiation to the spatial structure of plant populations. This study will provide crucial information on the roles of polyploidy and disturbance in the landscape genetics of plant populations. Broader impacts include undergraduate training and independent research in both classical methods and highly technical modern methods not usually available to undergraduates.