Butterfly abundance and diversity, or lack thereof, in the world's smallest mountain range: California's Sutter Buttes

The Sutter Buttes are a small, isolated mountain range in the center of northern California’s Central Valley, formed by volcanic activity ~1.5 MYA. Their young age and location—nearly equidistant between the Coast Range and Sierra Nevada Range—make the Buttes biogeographically unique. Due to a history of private ownership scientific access has been limited and much remains unknown about the natural history and ecology of the area. In order to address this we performed surveys of the butterfly fauna of the Buttes. Over two years we performed bi-weekly transects and recorded species presence, abundance, and phenology, as well as information about common butterfly hostplants found here. Utilizing transect data from the Coast and Sierra Nevada Ranges we determined that the Buttes fauna more closely resembles the Valley floor fauna than either nearby mountain range. Our results also indicate that the Sutter Buttes harbor a significantly depauperate butterfly fauna: several butterfly species which are common in the Central Valley or the foothills are simply not present in the Sutter Buttes. We hypothesize that the range may boast an insufficient number or assortment of hostplants and/or be too geographically isolated from butterfly source populations to support a diverse array of species.