Shuldman, M.I. , Dawson, Todd .
Taking the Heat: Ecotypic differentiation in response to extreme heat events in a California native shrub.
There are many studies examining species’ responses to changes in average climatic conditions but few studies examine species responses to extreme climatic events such as heatwaves. The number of yearly heatwaves is predicted to increase in California (CA). We are investigating if populations of the widespread near-endemic Heteromeles arbutifolia will differentially tolerate heatwaves given that they have historically experienced drastically different regional climate. Specifically, we tested for ecotypic variation in growth, water use, and photosystem integrity for seedlings from two populations during an artificial heatwave. We grew the seedlings in the greenhouse from seeds collected from one northern population in Mendocino County (39 N 43’50, 123 W 38’40) and one southern population from San Diego County (32 N 53’29, 117 W 05’41). During the experiment, 40 plants received ambient conditions (28 Â°C) and 40 received elevated air temperature conditions (38Â°C) for 4 days. Before the heatwave we determined the integrity of the photosystem using chlorophyll florescence and the average leaf conductance of water vapor (site significantly different P = <0.001). On day zero and day two of the heatwave there was no significant difference in predawn Fv/Fm between the two populations. However, during day two of the heatwave, plants from southern CA had extremely low midday Fv/Fm compared to plants under ambient conditions. This suggests southern plants were more functionally compromised. When grown in a common environment the populations responded differently, suggesting there are underlying genetic differences. Our results show that H. arbutifolia exhibits ecotypic variation in response to an artificial
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1 - University of California, Berkeley, Integrative Biology, 3060 Valley Life Science Building, MC# 3140, Berkeley, CA, 94720, USA
Presentation Type: Oral Paper:Papers for Topics
Location: 551B/Convention Center
Date: Tuesday, August 3rd, 2010
Time: 11:15 AM