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

多倍体，即染色体在基因组中存在多个拷贝，是被子植物遗传多样性的核心过程，但其生态学意义尚不清楚。少数细胞型排斥理论预测多种细胞型不应共存；然而同域多倍体并不罕见。共存机制包括：1)通过自交或孤雌生殖实现生殖保证；2)生境分化。关于多倍体如何影响生境利用，或生境分化如何影响多倍体的产生和分布，我们知之甚少。本文研究了多年生草本植物山金车（Arnica cordifolia）三倍体和四倍体共存的机制。三倍体的起源将通过遗传指纹鉴定来评估。将确定生殖模式，以评估逃避少数细胞型排斥的潜力。本研究将量化三倍体在受干扰生境中的分化，并利用互反移植实验来验证三倍体在受干扰生境中被选择性维持的假设。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。本研究将为揭示多倍体和干扰在植物种群景观遗传中的作用提供重要信息。更广泛的影响包括本科生通常无法获得的经典方法和高技术现代方法的本科培训和独立研究。

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.