Distribution and behavioral responses to climate change in tropical Lepidoptera

Abstract

Climate change is affecting species at different levels and threatening biodiversity around the globe. Tropical ectotherms may be particularly vulnerable to climatic warming. Species react to climate change with different strategies, including tracking changes through shifting distributions, responding behaviorally, adapting morphologically, or altering phenology. In this thesis, using occurrence records, I examined and projected butterfly and moth distributions using species distribution models and occupancy modeling to examine the distributional responses of Lepidoptera under climate change. In addition, I incorporated field behavior observations with biophysical models to test how tropical butterfly species adapt to cool temperatures at tropical borders and assessed potential climate change vulnerability as a consequence of activity and thermal adaptation. Lastly, I tested alternative hypotheses of morphological traits driving species responses to thermal variation rather than thermoregulation. I found that climate change is driving complex patterns of change in geometrid moths over recent decades. Through distribution modeling I also found that climatic warming likely a have significant influence on future butterfly distributions in Hong Kong and that future changes in butterfly distributions may diminish the level of protection species receive through protected areas. Through field and behavioral observations of butterflies across China and Hong Kong, I also found that tropically distributed species are morphologically more adapted to cooler environments and are more likely to bask at cooler temperatures than widely distributed species. These morphological and behavioral traits may lead to detrimental effects on tropical butterflies at range margins under climate change. Finally, through a field-based experiment, I found that darker butterfly individuals are less likely to be predated upon in cool forest environments in addition to likely gaining thermal benefits. The studies here highlight the importance of disentangling multi-functional traits in accurately projecting organismal responses to environmental changes such as climate change. This thesis points to the vulnerability of tropical Lepidoptera and similar ectotherms under climate change but also demonstrates the opportunity of incorporating ecological modeling, together with field data, in understanding climate change impacts on ectotherms.