Global climate change has the potential to dramatically alter multiple ecosystem processes, including herbivory. The development rates of both plants and insects are highly sensitive to temperature. Although considerable work has examined the effects of temperature on spring phenologies of plants and insects individually, few studies have examined how anticipated warming will influence their phenological synchrony. We applied elevated temperatures of 1.7 and 3.4. °C in a controlled chamberless outdoor experiment in northeastern Minnesota, USA to examine the relative responses in onset of egg eclosion by forest tent caterpillar (. Malacosoma disstria Hübner) and budbreak of two of its major host trees (trembling aspen, Populus tremuloides Michaux, and paper birch, Betula papyrifera Marshall). We superimposed four insect population sources and two overwintering regimes onto these treatments, and computed degree-day models. Timing of egg hatch varied among population source, overwintering location, and spring temperature regime. As expected, the development rates of plants and insects advanced under warmer conditions relative to ambient controls. However, budbreak advanced more than egg hatch. The degree of phenological synchrony between M. disstria and each host plant was differentially altered in response to warming. The interval by which birch budbreak preceded egg hatch nearly doubled from ambient to +1.7 °C. In the case of aspen, the sequence changed from egg hatch preceding, to following, budbreak at +3.4 °C. Additionally, under temperature regimes simulating future conditions, some insect populations currently south of our study sites became more synchronous with the manipulated hosts than did currently coexisting insect populations. These findings reveal how climate warming can alter insect-host plant interactions, through changes in phenological synchrony, possibly driving host shifts among tree species and genotypes. They also suggest how herbivore variability, both among populations and within individual egg masses, may provide opportunities for adaptation, especially in species that are highly mobile and polyphagous.
Bibliographical noteFunding Information:
We thank B4WarmED site managers Artur Stefanski and Karen Rice, who provided technical expertise. Dr. Jun Zhu and Peter Crump (University of Wisconsin) provided valuable statistical modeling assistance. The Wisconsin DNR, Minnesota DNR and Jana Albers, Christine Buhl, as well as local citizens provided assistance locating and collecting insects. This research was funded by the National Institute of Food and Agriculture, U.S. Department of Agriculture (AFRI project 2011-67013-30147 ), the Office of Science (BER), U.S. Department of Energy (Grant No. DE-FG02-07ER64456 ), the University of Wisconsin College of Agricultural and Life Sciences, a UW Zoology Department teaching assistantship, a UW PEOPLE project assistantship, the Minnesota Department of Natural Resources, the University of Minnesota College of Food, Agricultural, and Natural Resources Sciences and the UM Wilderness Research Foundation. Reviews by two anonymous reviewers substantially improved this paper.
© 2015 Elsevier B.V.
- Climate change
- Plant-insect interactions