Greater impacts from an extreme cold spell on tropical than temperate butterflies in southern China

The 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 and will likely have profound effects on species distributions, community organization, and ecosystem function. However, generalities about how ecosystems respond to these disturbances remain understudied. In 2008, an extreme once-in-50-year cold spell affected sub-tropical China, causing catastrophic damage to natural systems within the swath of the disturbance. In this study, we investigated the effects of this disturbance on a community of butterflies in the Nanling Mountain Preserve in southern China. Butterfly count surveys were conducted from 2006 to 2011. We predicted that the 2008 cold spell would have disproportionate effects on tropical butterfly species, increasing community dominance of more broadly tolerant temperate species. Over the course of the study, we counted 3403 butterflies from 249 species. Our results showed that the cold spell reduced abundances of temperate and tropical 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 predisturbance conditions in 2011. 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.