Tropical butterfly biodiversity change revealed using museum collections

Globally, biodiversity is changing, however, whilst biodiversity is concentrated in tropical ecosystems, the state of knowledge on how tropical biodiversity is changing is poor. One of the key challenges is the lack of data from these highly diverse regions, especially long-term data on species distributions. Museum collections hold an abundance of historical species records, but are a largely untapped resource for understanding tropical biodiversity change. Here, I focus on the butterflies of Sulawesi (Indonesia) and use museum specimens to examine the vulnerability of endemic species to climate change, relative to non-endemic species. I also investigate long-term changes in tropical communities over 164 years; and evaluate how the incorporation of historical species records into analyses improves our knowledge of species thermal niches and their future projections. I find that endemic species may not be more vulnerable to climate-driven mountaintop extirpation. I find no systematic loss of species richness at regional (1624-10723 km2) scales, but long-term turnover in communities consistent with increased tolerance to habitat modification. I find that species may be able to persist at warmer locations than recent species records suggest. Taken together, my results reveal that tropical butterflies have changed in occurrence and distribution over the past two centuries, but may be more resilient to anthropogenic pressures than current narratives have suggested. My findings also suggest that endemic species may not be disproportionately vulnerable to climate change and land-use change relative to more widespread species. Museum collections contain a wealth of information on tropical biodiversity, and these data need to be examined with urgency. I have shown how the incorporation of museum data alters our understanding of how anthropogenic changes are affecting tropical butterflies, and future work should evaluate how the inclusion of historic species records changes conservation priorities more generally.