Metapopulation theory provides a framework for exploring how spatial factors influence population persistence. Traditional metapopulation theory assumes habitat patch attributes, other than occupancy, are static in space and time. However, these assumptions are rarely met because in real landscapes, disturbance and succession cause habitat patches to disappear and reemerge. If a species is mobile and able to track its resources, then spatiotemporal connectivity (i.e. how connected a focal patch is to surrounding habitat patches through time) may be essential for population persistence in highly dynamic landscapes. Peponapis pruinosa is a solitary, univoltine, ground nesting bee. It collects pollen only from Cucurbita spp. and nests in or near Cucurbita fields. While wild Cucurbita spp. are absent from the Sacramento Valley of California, Cucurbita crop species are grown throughout the region in annual crop rotations. To explore the role of spatiotemporal connectivity in a highly dynamic landscape I sampled squash bee abundance at 25 Cucurbita fields in the Sacramento Valley. I used GIS data provided by the Department of Pesticide Regulation and conducted grower interviews to determine where Cucurbita fields were located the previous year. General linear models were used to evaluate the effects of spatiotemporal connectivity, farm type and natural habitat on P. pruinosa abundance.
Results/Conclusions
Models that included distance to nearest 2009 Cucurbita field best explained 2010 P. pruinosa abundance. Farm type (e.g. organic or conventional) and percent natural habitat within 2km of the field (i.e. the estimated foraging range of P. pruinosa) were not important explanatory variables. This study suggests that spatiotemporal connectivity, or how connected a focal patch is to surrounding habitat patches through time, is important in highly dynamic landscapes. As such, metapopulation models for dynamic landscapes could be improved by including spatiotemporal connectivity measures.