Abstract Detail

Dynamics and Demography of Alpine Islands

Winkler, Daniel [1], Yu-Chan Lin, Michelle [2], Chapin, Kenneth [3], Huxman, Travis [4].

Nowhere left to go: phenotypic shifts undercompensate warming and drought effects in a rare, endemic alpine cushion.

Global change is expected to fragment and contract many species ranges. This is especially true in high altitude biodiversity hotspots, where plant communities are often composed of rare and endemic species. Warmer growing seasons and increased drought events may negatively impact these populations by limiting regeneration. However, phenotypic variation may enable new individuals to establish and persist. Here, we test for high altitude species responses to the interactive effects of warming and drought in Heterotheca brandegei, a perennial cushion plant endemic to alpine outcroppings in Sierra de San Pedro Mártir National Park, Baja California, México. We exposed H. brandegei seedlings to experimental warming and drought conditions to test early life history responses and the species’ ability to tolerate change. Drought negatively influenced seedling carbon allocation, with overall reductions in above- and belowground biomass. Warming and drought each led to substantial reductions in allocation to photosynthetic structures. At the same time, individuals maintained a high specific leaf area and carbon investment in leaves despite treatments, suggesting that existing phenotypic variation within populations may be large enough to withstand change. However, warming and drought interacted to negatively influence leaf-level water-use efficiency, an effect not observed in either individual warming or drought treatments where stressors did not appear large enough to negatively impact plant water-use. Seedling mortality rates were nearly three times higher in warming and drought treatments compared to controls, suggesting bleak prospects for H. brandegei to maintain populations at their current levels. Overall, our results suggest H. brandegei populations may experience substantial declines under future conditions but new individuals may be able to establish, albeit, as smaller, more stressed plants. These results further suggest that warming alone may not be as consequential to populations as drought will be in this already water-limited system.

1 - US Geological Survey, 2290 S West Resource Boulevard, Moab, UT, 84532, USA
2 - University of California, Irvine, Biological Sciences, Irvine, California, 92697-2525, United States
3 - University of Arizona, Ecology & Evolutionary Biology, Tucson, AZ, USA
4 - University of California, Irvine, Irvine, California, 92697-2525, United States

Keywords:
Baja California
chasmophyte
cushion
endemic
establishment
golden aster
Heterotheca
México
outcropping
Sierra de San Pedro Mártir.

Presentation Type: Colloquium Presentations
Session: CO02, Dynamics and demography of Alpine Islands
Location: San Luis 2/Starr Pass
Date: Monday, July 29th, 2019
Time: 8:15 AM
Number: CO02002
Abstract ID:267
Candidate for Awards:None