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Pascual, Mariana [1], Rieseberg, Loren [2].

Hurricane Harvey and the wild silverleaf sunflowers.

Hurricane Harvey is considered the wettest tropical cyclone on record in U.S. history. In late August 2017 Harvey’s center made landfall east of Rockport Texas, where it stalled for four days with sustained winds of at least 200 km/hr and produced excessive rainfall (> 60 inches in some places) that caused floods throughout the region.
Two months earlier, around where Harvey made its first landfall, six populations of the silverleaf sunflower, Helianthus argophyllus, were tagged, measured for height and flowering stage, and genotyped for HaFT1, a flowering locus inside a region of low recombination on chromosome 06. This gene explains 88% of the variation in reproductive phenology of two ecotypes of this species: 1) the late flowerers, which are homozygotes for a deletion of HaFT1, grow taller, produce fewer branches and occur throughout the species distribution in Texas; 2) the early flowerers, which are homozygotes or heterozygotes for HaFT1, tend to be shorter in stature, branchier, and are largely restricted to barrier islands in the Gulf of Mexico.
Two weeks after the hurricane, those same six populations (five on barrier islands and one in Rockport) were visited to look for surviving plants. Only 31(15%) of the tagged sunflowers survived. Survival varied widely between populations, and was best explained by plant height. Survivors were significantly shorter in height (mean=105.02 cm, sd=60.49816) than those sunflowers that didn’t survive (mean=138.4979, sd=66.36633). Being rarer in most populations the early allele was more strongly affected by the hurricane than the late allele. No surviving individual was an early homozygote (0/17), while 20% of heterozygotes survived (8/42), as well as 18% (22/119) of the late homozygotes. However, when sampling the same populations in 2018, none had significant genotype frequency differences (Fisher’s tests) with respect to 2017. Similarly, the early allele suffered only a minor reduction in frequency in island populations; it went from 0.258 in 2017 to 0.202 in 2018. It is possible that survival was determined by the development stage of the plants given that most of the survivors had not flowered yet and there is evidence that plants respond to flooding differently when in the reproductive phase.

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1 - University Of British Columbia, Botany, 3200-6270 University Blvd., Vancouver, BC, V6T 1Z4, Canada
2 - University Of British Columbia, Department Of Botany, 6270 University Blvd, Vancouver, BC, V6T 1Z4, Canada

extreme weather event.

Presentation Type: Oral Paper
Session: ECO1, Ecology: Phylogeny, Disturbance, and Tree Architecture Over Large Spatial Scales
Location: /
Date: Tuesday, July 20th, 2021
Time: 10:00 AM(EDT)
Number: ECO1001
Abstract ID:503
Candidate for Awards:Ecological Section Best Graduate Student Paper

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