Geographic homogenization but little net change in the local richness of Canadian butterflies

Aim: Recent studies have found that local-scale plots measured through time exhibit marked variation in the change in species richness. However, the overall effect often reveals no net change. Most studies thus far have been agnostic about the identities of the species lost/gained, as well as the processes that may lead to these changes. Generalist traits may be crucial in allowing species to colonize new plots or remain resilient in situ, whereas environmental filtering may remove specialists. We test whether plots are changing in species richness, whether they are becoming more similar (i.e. becoming homogenized) through time, as well as whether several generalist traits can predict gains or losses from local plots. Location: Canada Time period: 1945-2015 Major taxa studied: 265 species of butterflies Methods: We measured i. species richness change and ii. pairwise beta diversity across 96 well-sampled 10x10 km plots across Canada between two time periods: 1945-1975 and 1985-2015. We ...