COS 21-1
Climate change perils for dioecious plant species

Tuesday, August 12, 2014: 8:00 AM
308, Sacramento Convention Center
Kevin R. Hultine, Department of Research, Conservation, and Collections, Desert Botanical Garden, Phoenix, AZ
Kevin C. Grady, School of Forestry, Northern Arizona University, Flagstaff, AZ
Stephen M. Shuster, Biological Sciences, Northern Arizona University, Flagstaff, AZ
John C. Stella, Forest and Natural Resources Management, State University of New York, College of Environmental Science and Forestry, Syracuse, NY
Troy Wood, Colorado Plateau Research Station, U.S. Geological Survey, Flagstaff, AZ
Thomas G. Whitham, Department of Biological Sciences and Merriam Powell Center for Environmental Research, Northern Arizona University, Flagstaff, AZ

Rapid climate change poses a significant threat to plant species and the biotic communities they support, to the extent that mass extinctions are possible, if not likely over the next century. Dioecious species may be especially at risk to the effects of climate change given that these species often display a spatial segregation of the sexes, reinforced by physiological and morphological specialization of each sex to different habitats. Sex ratio biases have been reported in about 70 percent of all dioecious species studied, and in almost 80 percent of these studies, sex ratios are male biased in less favorable habitats, i.e., those most susceptible to environmental change. Therefore, the effects of climate change (i.e., increasing aridity) may exacerbate skewed sex ratios in resource-poor habitats.  This presentation addresses differences among sexes in resource allocation and the potential for climate change to result in trait mal-adaption of one gender but not the other. We summarize evidence from the recent literature showing that the physiological performance of females (e.g., productivity, leaf gas exchange) will likely suffer to a greater extent from climate stressors than males. 


Recent experiments show that either drought or climate warming may have a stronger negative impact on the productivity of female plants compared to male plants from the same population. In experiments where plants were well watered and kept in ambient temperatures, growth of male plants were 13% higher than co-occurring female plants (P = 0.0005, n = 67 studies). However, under drought and/or climate warming conditions, the productivity of male plants rose to 44% above that of females (P = 0.0014, n = 15 studies). Differences in growth between genders were reinforced by patterns of leaf gas exchange. Under well-watered, ambient temperature conditions, stomatal conductance (g) was equal between male and female plants (P = 0.87, n = 30), but was 96% higher in male plants under drought / climate warming conditions (P = 0.0138, n = 18). Likewise, net carbon assimilation (A) was equal between genders under well watered / ambient temperature conditions (P = 0.78, n = 39), but was 84% higher in male plants under drought / climate warming conditions (P = 0.0093, n = 21). These data suggest that the effects of climate change may yield extreme male-biased sex ratios and reduced population stability in dioecious species.