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Diamanda Zizis

Heading for a breakdown: Assessing evolution through the hybridization of two sexual systems

Diamanda Zizis ’23

Faculty Mentor(s):
Christopher Martine, Biology.
Tanisha Williams, Biology.
Funding Source:
Wayne Manning Internship Fund, David Burpee Endowment, Botanical Society of America Undergraduate Student Research Grant

Hybridization is an important evolutionary pathway that has contributed to the world’s vast biodiversity. In plants, hybridization is known to be an important mechanism for speciation, phenotypic divergence, and changes in reproductive systems. Solanum species present an ideal system to investigate how hybridization between two different sexual systems impacts the reproductive and phenotypic biology of the hybrid progeny. Hybrids were acquired from crosses between Australian species Solanum dioicum (dioecious) and S. ultraspinosum (andromonoecious). The only successful hybrids from the original crosses were those derived from S. diocium as the pollen donor and S. ultraspinosum as the pollen recipient. Due to strong maternal effects, all the F1 hybrids resembled S. ultraspinosum, so all F1 plants were andromonoecious. To assess phenotypic differences between the hybrids and their parents, I collected morphometric data and used ImageJ software. A series of statistical analyses were done using R. A principal component analysis confirmed that the hybrids were distinct from both parents, but were most similar to S. ultraspinosum. The F2 hybrids appear to demonstrate variability in inflorescence architecture, which may be suggestive of a change in sexual system, although further analysis is needed. In attempts to create an F3 hybrid generation, nearly all of our crosses have failed—suggesting that a hybrid breakdown is occurring. To determine where the breakdown is occurring, I will be employing a technique using fluorescent microscopy. Overall, my study will promote a better understanding of hybridization—a driving force of plant speciation—which has broad impacts for the long-term viability of plant species.

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