Forecasted changes in global climate include not only shifts in average conditions, but also changes in the frequency and intensity of climatic extremes. One such climate extreme expected to change in the future are extreme cold spells. Although these disturbances may become less frequent, extreme cold spells are believed to persist in the foreseeable future. However, how distributions and interactions of insects and community organization respond to these disturbances remain understudied. Here we report the impacts of two cold spells, one in 2008 affecting subtropical China and the other in 2010 affecting subtropical Florida, on a butterfly community in the Nanling Nature Preserve and a specialist oil bee community in southern Florida.
Results/Conclusions
Our results show that the cold spell reduced abundances of temperate and tropical butterfly species by 50% and 88%, respectively. The disproportionate loss of tropical butterfly species changed butterfly community structure, resulting in a post-cold spell community nearly completely dominated by temperate species. Butterfly communities remained dominated by temperate species for 2 years before the abundances of tropical species return to pre-disturbance conditions in 2011. Similarly, in southern Florida we found evidence of differential impacts from the extreme cold spell on the native, subtropical oil bee vs. the introduced, tropical oil bee. Specifically the cold spell had little impact on the abundance of the native bee, while the abundance of the introduced, tropical bee took a hit. Our findings demonstrate that extreme cold spells are important climate change-related phenomena that can have strong impacts on tropical species distributions and abundances, especially at the threshold of their thermal tolerances. As cold spells change in frequency and intensity in the future, we should expect their role in structuring sub-tropical communities, in particular, the presence and dominance of tropical species to also change.