Whitney, Kenneth D.2013-07-242013-07-242013-07-242013-07-242012-122013-07-24December 2Sneck, Michelle. "Evolutionary responses to global change: an experimental test of the effect of altered precipitation on hybridization rates in sunflower (Helianthus)." (2013) Master’s Thesis, Rice University. <a href="https://hdl.handle.net/1911/71692">https://hdl.handle.net/1911/71692</a>.https://hdl.handle.net/1911/71692Climate change is rapidly altering natural ecosystems. Plastic and adaptive responses to climate change (i.e., range shifts and phenology) have been widely noted across taxa. However, the effects of climate change on evolutionary processes such as interspecific gene flow (hybridization) are less well known. In this study, we quantified hybridization rates in response to experimental manipulations of rainfall, an important dimension of global change. We used rain-out shelters in the field and quantified rates of hybridization between two congeners, Helianthus annuus (common sunflower) and H. petiolaris (prairie sunflower). We found that H. annuus maternal plants produced hybrid progeny more than H. petiolaris maternal plants, with a trend for decreased rates of hybridization with increased soil moisture (when rain-out shelters were absent). The relative number of open inflorescences of each species predicted hybridization rates. Thus, this study demonstrates how changing environmental conditions, specifically precipitation, could influence hybridization rates.application/pdfengCopyright is held by the author, unless otherwise indicated. Permission to reuse, publish, or reproduce the work beyond the bounds of fair use or other exemptions to copyright law must be obtained from the copyright holder.Climate changeEvolutionPhenologyGene flowHybridizationThesis2013-07-24123456789/ETD-2012-12-329