Mounting evidence suggests that climate change, agricultural intensification and disease are impacting bumblebee health and contributing to species’ declines. Identifying how these factors impact insect communities at large spatial and temporal scales is difficult, partly because species may respond in different ways. Further, the necessary data must span large spatial and temporal scales, which usually means they comprise aggregated, presence-only records collected using numerous methods (e.g. diversity surveys, educational collections, citizen-science projects, standardized ecological surveys). Here, we use occupancy models, which explicitly correct for biases in the species observation process, to quantify the effect of changes in temperature, precipitation and floral resources on bumblebee site occupancy over the past 12 decades in North America. We find no evidence of genus-wide declines in site occupancy, but do find that occupancy is strongly related to temperature, and is only weakly related to precipitation or floral resources. We also find that more species are likely to be climate change ‘losers’ than ‘winners’ and that this effect is primarily associated with changing temperature. Importantly, all trends were highly species-specific, highlighting that genus or community-wide measures may not reflect diverse species-specific patterns that are critical in guiding allocation of conservation resources.
1992. Temporal and spatial distribution of the harmful diatoms Chaetoceros concavicornis and Chaetoceros convolutus along the British Columbia coast. Can. J. Fish. Aquat. Sci. 49: 1924-1 93 1.The harmful phytoplankters Chaetoceros concavicornis and Chaetoceros convolutus are normal components of the phytoplankton assemblage along the British Columbia coast. During 1988, these diatoms occurred at their highest concentrations in the spring and fall from the Strait of Georgia to Queen Charlotte Strait. North of Queen Charlotte Strait, the maximal concentrations appeared to be delayed until summer. The greatest concentrations occurred in the waters of the Strait of Georgia and its contiguous bays and inlets, especially Jervis Inlet, where concentrations of C. concavicornis and C. convolutus which could be harmful to salmon occurred during the spring and fall of 1988. Lesser concentrations occurred in coastal seawaters north of the Strait of Georgia. these phytoplankters were absent, or were present in only minor concentrations, in inlets with low-sal inity waters such as Holberg Inlet and Indian Arm. Harmful Chaetoceros cells were restricted to seawaters greater than approximately 17%0 salinity. Vertically and horizontally well-mixed waters, such as those of Johnstone Strait, also appeared to restrict the presence of these cells. The greatest concentrations of these diatoms occurred during the spring and fall in relatively stratified coastal seawater with salinities between 26 and 34%0.Les phytoplanctontes dangereux que sont Chaetoceros concavicornis et Chaetoceros convolutus sont des elements normalement presents dans I'assemblage phytoplanctonique le long de la cbte de la Colombie-Britannique. En 1988, ces diatomkes ont atteint leurs concentrations les plus elevkes au printemps et A I'automne du dktroit de Gkorgie au dktroit de la Reine-Charlotte. Au nord du dktroit de la Reine-Charlotte, les concentrations maximales semblent avoir 6t6 retardees jusqu'A I ' M . Les concentrations les plus 6levees ont kt6 observees dans les eaux du dktroit de Gkorgie et dans les baies et inlets adjacents, particuliPrement I'inlet Jervis, oh on a mesure au printemps et A I'automne 1988 des concentrations de C. concavicornis et C. convolutus qui pouvaient etre dangereuses pour le saumon. Des concentrations plus faibles ont 6t6 observkes dans les eaux cbtiPres au nord du detroit de Gkorgie. Ces phytoplanctontes ktaient absents, ou presents en faibles concentrations, dans les inlets A faible salinitk comme I'inlet Holberg et le bras Indian. Les cellules dangereuses de Chaetoceros ktaient confinkes aux eaux marines presentant une salinit6 superieure A environ 17 %o. Les eaux bien melangees dans les plans vertical et horizontal, corrlme cel les du detroit de Johnstone, seniblaient aussi limiter la presence de ces organismes. Les concentrations les plus elevees de ces diatomees ont 6te observees au printemps et en automne dans des eaux cbtiPres relativement stratifiees presentant des salinites situees entre 26 et 34 "A.
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