Paleoecology of butterfly and moth populations

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Eastern spruce budworm (SBW) is a major disturbance agent of eastern North American forests, reaching epidemic proportions on a 25-40 year cycle. These outbreaks can have severe economic impacts; the SBW outbreak of 1967-1993 affected 50 M hectares of forest in eastern North America, with an estimated loss of 44 million m3 of timber per year of the cycle. Economic models indicate potential losses of $10.8 - 15.3 billion in Atlantic Canada during an outbreak. Disturbances are often classified based on their extent, severity, duration, and frequency. As climate warming continues to change landscapes worldwide, researchers are attempting to understand and predict how these aspects of disturbance are likely to change and how those changes may necessitate changes in forest management practices. Understanding the past relationships between moth outbreaks and climate will reveal how outbreaks are expected to change in the future and allow us to adapt appropriate management strategies. Unfortunately, the influence of a changing climate on the frequency, duration and severity of SBW outbreaks is largely unknown, mostly because 1) only two outbreaks have been studied in any detail because of their great length, and 2) the interactions of SBW with its hosts, predators, parasites, and climate are extremely complex and largely unknown. One objective of the proposed research program is to determine how the frequency, duration and severity of SBW outbreaks are related to climate. We will use a novel method to study past moth populations. Moth and butterfly wings are covered by microscopic scales of different shapes and sizes that are made of chitin, which preserves well in lake sediments. I will reconstruct the outbreak history of SBW from lake sediments for two contrasting climate periods -The Medieval Climate Anomaly (also called the Medieval Warm Period), when it was warmer than average, and the Little Ice Age, when it was colder than average. Each of these periods spans about 300 years, so we can expect 8-12 cycles within each. I will statistically compare the frequency, duration, and severity of SBW outbreaks between these contrasting climates, thereby gaining insight into the relationship of SBW population dynamics to climate. Another aspect of my research relates to the monarch butterfly, one of the few charismatic, iconic insects. To great consternation, its populations have been declining for the past 60 years. Why this is happening is an area of active research. But is this decline part of natural cycles? How unusual is this decline? Were populations perhaps smaller in general in pre-European times when there were fewer agricultural/disturbed fields that would support the monarch's host plant, milkweeds? I will core lakes within the main overwintering grounds of the monarch in Mexico where the highest concentrations of monarchs occur and use changes in the abundance of fossil wing scales as an index of past population sizes of monarchs.