Previous research on a pollinator community comprised of 14 species of bumble bees in the northern Sierra Nevada of California showed that there is dramatic variation in the species found in any given meadow from one year to the next and across meadows within a year.  For example, many meadows had an over 50% change in bumble bee species composition from 2002 to 2003 and again from 2003 to 2004.  Not only does the species composition change, the total number of species found in a meadow can vary dramatically.  To understand the dynamics of this system, we developed a model to examine how year to year variation in snowmelt and interspecific competition influence bumble bee communities at different elevations. 

Results/Conclusions Our model suggests that the number of species found should decline with elevation and the small changes in the probability of snowmelt can influence the number of species in a meadow and year to year turnover.  When combined with predictions about global climate change, this model suggests there will be substantial changes in our alpine pollinator communities.