Changes in butterfly distributions and species assemblages on a Neotropical mountain range in response to global warming and anthropogenic land use

AIM: To assess the changes in the elevational distribution of 151 butterfly species over a period of 22 years (1988–2011) and investigate whether these changes are related to regional global warming and land use change. LOCATION: Sierra de Juárez, Oaxaca, Mexico. METHODS: Butterflies were surveyed at eight sites spanning elevations ranging from 117 m to 3000 m in 1988, and the same sites were resurveyed in 2010–2011. Changes in the elevational distribution of species and the structure and composition of species assemblages were compared between surveys. The results were interpreted in the context of land use and climate change in the region. RESULTS: Butterfly species had shifted their distributions uphill by approximately 145 m on average. Significantly more species (78) showed an uphill shift in their distributions than a downhill shift (32 species). Species occurring above 1000 m elevation had shifted their distribution to an extent that matched the range shift expected under the recorded temperature changes. However, for species occurring below 1000 m elevation, and for all species combined, uphill range shifts were significantly less than expected based solely on the increase in temperature. Land use change over the study period was more pronounced at low elevations, and these butterfly assemblages are now dominated by generalist species. MAIN CONCLUSIONS: Our results represent the first concrete evidence of shifts in elevation distribution of a large Neotropical butterfly community, attributable to increased regional temperatures. At high elevations, land use change is minimal and climate change appears to be the main driver of changes to distributions and assemblages, and the main conservation threat. However, extensive land use change has been the main driver of changes to butterfly communities at lower elevations.