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Abstract Detail

Dynamics and Demography of Alpine Islands

Sethi, Meera Lee [1], HilleRisLambers, Janneke [2].

Higher, Faster, Hungrier: Complex Dynamics of a Subalpine Plant-Insect Herbivore Interaction.

Because short growing seasons constrain plant growth and biomass accumulation in high elevation habitats, herbivory can have profound impacts on both individual fitness and community dynamics in these settings. Climate change is generally expected to increase the activity of insect herbivores in particular, since higher temperatures are strongly correlated with the metabolic rates of exotherms. However, montane communities may not respond in the same ways as lowland ecosystems. From 2016-2018 we measured apparent leaf damage along two elevational transects spanning a total gradient of 1490-2020m for nine perennial wildflower species in the subalpine meadows of Mt. Rainier National Park. Contrary to our expectation that leaf loss would be highest at low-elevation sites, we found either no differences with elevation (six species) or the opposite pattern (three species). Here we present data from the abundant and ecologically important Subalpine Lupine (Lupinus latifolius var. subalpinus), for which we found a significant increase in herbivory with elevation despite the corresponding decrease in air temperature; for some individuals at the highest-elevation sites, upwards of 40% of total biomass could be lost to insect herbivory over the course of the summer, resulting in negative impacts on photosynthetic capacity. Experimental feeding trials with field-caught individuals of the dominant chewing insect herbivore in this system, the Cascade Timberline Grasshopper (Prumnacris rainierensis), explained part of this pattern. High-elevation grasshoppers had higher feeding rates overall and increased their feeding rates more in response to warmer temperatures compared to low-elevation conspecifics, enabling “eating sprees” that are likely facilitated by the decrease in canopy cover and increased sun exposure at high elevations. In addition, high-elevation Lupine leaves had higher carbon-nitrogen ratios than low-elevation leaves, suggesting compensatory feeding may play a role in this pattern. These findings highlight the complexity of predicting how species interactions will change with warming in alpine and subalpine ecosystems, where acclimation or local adaptation, vegetation structure, and edaphic factors add a tremendous complexity to ecological dynamics.

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1 - University of Washington, Seattle, Biology, c/o Hille Ris Lambers Lab , Box 351800, Seattle, WA, 98195-1800, USA
2 - University of Washington, Seattle, Biology, c/o Hille Ris Lambers Lab, Box 351800, Seattle, WA, 98195-1800, United States

biotic interactions

Presentation Type: Colloquium Presentations
Session: CO02, Dynamics and demography of Alpine Islands
Location: San Luis 2/Starr Pass
Date: Monday, July 29th, 2019
Time: 10:15 AM
Number: CO02009
Abstract ID:321
Candidate for Awards:Ecological Section Best Graduate Student Paper

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