Print PageAlthough much recent research has centered on climate change, long-term datasets of animal abundance or occurrence are still relatively rare. Here we use a 30-year data set of butterfly communities at ten sites in Northern California to determine if 1) Butterfly community composition is changing over time and 2) If weather variables covary with butterfly community composition over time and if this depends on whether butterflies are considered weedy or non-weedy.
Butterfly abundance data were collected at ten different sites from the Coast Range to the Eastern Sierra in Northern California. To determine if the community composition of butterflies varied over time, we performed a non-metric multidimensional scaling (NMDS) technique that characterized the years at a site by the butterfly abundances. We then divided the years into early, mid, and late categories and ran an ANOSIM routine to determine if the categories were significantly different from one another.
We performed NMDS on the years using average daily temperatures at the sites instead of butterfly abundances. The resulting resemblance matrix among the years was compared to the resemblance matrix among years using the butterfly data. Additionally, we divided the butterfly species into weedy or non-weedy species based on life history characteristics.
Results/Conclusions
We found that, for the majority of sites, butterfly community composition has not remained static and that there are significant differences in the communities based on the early, mid- and late time categories. We also found that mean temperatures were significantly associated with butterfly community changes over time, but only for non-weedy species. Additionally, the largest difference in association with weather variables between weedy and non-weedy species was at the higher elevation sites.
These results suggest that changes in climate may be affecting butterfly community composition and that this is dependent on life history. In our analyses, weedy butterfly community changes were less correlated with changes in climate, which may be due to a more generalized life history. Weedy species may be buffered by climate because they have a wider plant host range, have multiple broods per season, and are able to migrate among habitats. More specialized species may be more sensitive to climate change because of their narrow thermal tolerances, limited host range, and slow development. As more studies document changes in communities and how these changes are affected by climate, researchers should make note of the life history characteristics of the organisms under scrutiny for similar patterns
