Abstract Detail

Dynamics and Demography of Alpine Islands

Oldfather, Meagan [1].

Incorporating Demographic Responses to Climate Manipulations into Leading-Trailing Edge Dynamics of an Alpine Plant.

Range shifts in response to climate changes may be driven be expansions at leading range edges and/or contractions at trailing range edges. However, these expectations have been complicated in part by the importance of multiple climate variables and the potential for diverse responses of different life stages to changing climatic conditions. We test the robustness of the leading-trailing hypotheses for range shift predictions by manipulating climate and measuring population growth responses in nine populations across an alpine plant species range. Our approach brings together 1) range-wide spatial replication of demography and microclimate measurements, 2) climate manipulations of summertime temperature and precipitation, and 3) quantification of population growth responses to climate manipulations using integral projection models. Previous work on the focal species has found that complementary and compensatory relationships between demographic rates across multidimensional climate gradients lead to stable range-wide populations growth. I hypothesize that experimental heating will have a negative effect on population growth rate at hotter edge populations (trailing), and a positive effect at the cooler sites (leading), and that this effect will be ameliorated or exaggerated by experimental increases in precipitation in the driest or wettest populations respectively. These overall responses would result in a range expansion at the cool, wet edge of the species range and a contraction at the hot, dry edge. I found that the effect of the experimental manipulation on the demographic rates (germination, growth, reproduction, survival) was partially consistent with our predictions, with some by not all demographic responses following leading-trailing dynamics. Further, the effect of the manipulations for the demographic rate was highly dependent on individual size (e.g., the smallest individuals only were negatively affected by heating in the hottest, driest sites).     In terms of population growth rate, I found support for the leading-trailing hypothesis with reduction in the population growth rate in hot, dry population with experimental heating. This effect was ameliorated by experimental increases in summertime precipitation. However, I did not observe a requisite positive impact of heating in the coolest sites. Further, in the hotter, drier populations ambient (unmanipulated) population growth was the most robust, whereas cooler, wetter populations showed evidence of population decline under ambient conditions. These results lead to predictions of range contractions, as opposed to range shifts, with changing climatic conditions for this species and highlight that spatial patterns of population dynamics may not be indicative of population responses to a changing climate.      

1 - CU Boulder, Ecology and Evolutionary Biology, 1900 Pleasant Street, Boulder, CO, 80309, US

range shifts
climate change

Presentation Type: Colloquium Presentations
Number: 0004
Abstract ID:181
Candidate for Awards:None

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