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

University Of California-Santa Cruz, Santa Cruz CA

Investigators

Abstract

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.