Document Type

Honors Thesis

Publication Date

Spring 2015


Amelanchier is a genus of plants that produces seeds both sexually and by apomixis (asexual seed production). Asexuality is the dominant mode of reproduction in tetraploids (which contain four sets of chromosomes) and has created uncertainty about species delimitation in this genus. A tetraploid population of Amelanchier at a site called Pudding Rock on the Aroostook River in northern Maine has long been hypothesized to belong to Amelanchier gaspensis, a member of the Amelanchier sanguinea species complex. Using structural features (morphology), knowledge of the number of sets of chromosomes (ploidy level), and DNA sequence data, I tested this hypothesis. Analyses of my samples plus those obtained by others falsify this hypothesis because A. gaspensis does not form a distinct morphological or genetic cluster that includes the Pudding Rock population and that would warrant species status. Instead, my results confirm other data supporting the conclusion that plants that have been called A. gaspensis are members of a massive hybrid swarm.

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Biology Commons