Date Awarded


Document Type


Degree Name

Master of Science (M.Sc.)




Josh R Puzey

Committee Member

Matthais Leu

Committee Member

Harmony Dalgleish


Plants, unlike animals, lack the ability to quickly move to desirable locations, which poses a challenge when faced with climate change. Here, we use anthropogenic forest canopy loss in the eastern United States as a model for understanding the effects of climate change. Removal of the forest canopy significantly alters the abiotic habitat, as does climate change, by increasing the variability of moisture, light, and temperature. One powerful mechanism plants can use to cope with environmental change is hybridization, as it provides novel genetic variation. Hybridization, followed by introgression, makes it possible to pass along adaptive traits between species, which is crucial for safeguarding populations in challenging climates. Our study investigates the system of Asclepias syriaca (common milkweed) and Asclepias exaltata (poke milkweed) to understand how plants are responding to anthropogenic landscape changes. In areas where the forest canopy has been removed, these two species meet at an abrupt edge. Previous investigation found evidence of prolific gene flow and potential introgression between the two species, suggesting an adaptive benefit to having A. syriaca alleles. To explore further, we defined the native habitats of A. exaltata and A. syriaca and examined the adaptive potential of milkweed hybrids using both wild and purchased seed. Our results demonstrate that hybrids are not only intermediate in morphology but also physiologically, particularly in responses to light, herbivory, and desiccation stress. The plasticity these hybrids show suggest that they have the tools to adapt and pass on beneficial traits through gene flow. It also demonstrates how in a single generation, plants can show adaptive responses, which is imperative to the survival and genetic longevity of sessile organisms. These findings have important implications as anthropogenic activity is likely to continue altering light availability through forestry and urban development. Additionally, there will be pressure from a more variable climate, which will have trickle-down effects on plant-insect interactions. Our study highlights the adaptive potential of hybridization in plants and its importance in facilitating their response to climate change.




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