Biology of Willow Leaf Beetles

Project Overview

Project Overview This project began as an attempt to characterize the ecology of a plant-feeding beetle along a montane elevation gradient, and has grown into a long-term research program studying the ecology, physiology and genetics of insect populations, environmental gradients, and climate change. The Willow Leaf Beetle, Chrysomela aeneicollis (Coleoptera: Chrysomelidae; see above, center) is the dominant herbivore on willows in the subalpine zone of the east-central Sierra Nevada Mountains of California, between Tioga Pass and Taboose Pass. As shown in the figure below, the elevational range of the beetles has expanded and contracted over a multi-year time scale, and there seems to be a correlation to multi-year fluctuation in snowfall. See also our Preliminary analysis of our data on snow cover in these drainages.

Symmorphus with beetle prey

C. aeneicollis with eggs

Parasyrphus maggot hunting beetle larvae

Elizabeth Dahlhoff (1,3), Nathan Rank (2,3), and John Smiley (3)

1 . Santa Clara University
2. Sonoma State University
3. University of California White Mountain Research Station

Individual web pages: Dahlhoff, Rank, Smiley

Below: Elevational range of C. aeneicollis in the North Forth of Big Pine Creek since 1981.
Far Below: Red line = precipitation index (% of normal) Blue line = days of snow cover at 2700m elevation
Note that during wet years with long periods of snow cover, there is a tendancy for the beetles' range to expand.

We have investigated different aspects of the ecology, evolution and physiology of this system, including (1) predator-prey-willow interactions, including the biology of two prey-specific predators (see photos above), (2) ecology and disctribution of willow salicylate chemicals, (3) ecology and genetics of adaptation to temperature, elevation, and geographic gradients, (4) physiology and behavior of locally adapted genotypes, and (5) mechanisms of thermal adaptation. Several Sierran drainages have been studied, with long term data from North Fork Big Pine Creek, multiple Bishop Creek drainages, Rock Creek and other drainages. See the reference list for specific publications, and the history page for the history of the project. We have also prepared a poster entitled Genetics, Physiology And Ecology Of Subalpine Beetle Populations: Responses To Climate Change (powerpoint 5MB) which was presented at the 2006 PACLIM meetings, held at Asilomar, Pacific Grove CA on March 26-29. Recent presentations by all three senior authors were made at "Climate, Ecosystems and Resources in Eastern California" conference in Bishop, CA, November 2008. See CEREC website for abstracts and pdf's of the presentations.

Climate effects and need for long-term monitoring This system should be very useful for studying the biology of subalpine insects as their populations respond to climate change. We predict rising temperatures will interact with wet-dry cycles to produce stepwise but upward-trending populations of willows, beetles and their predators, with varying time-lags which can only be observed in 10-20 yr. data sets. It will be crucial to continue, and in some cases augment, annual monitoring efforts in order to be able to obseve these phenomena.

Acknowledgements: We wish to thank "team beetle" in all of its manifestations over the years, including students, family members and friends who have lugged equipment, endured mosquitos, slaved in the lab and counted "countless" beetles. This work has also been supported by the National Science Foundation, Division of Environmental Biology and the University of California White Mountain Research Station.