@article {1621,
	title = {Impact of enhanced ultraviolet-B radiation on flower, pollen, and nectar production},
	journal = {American Journal of Botany},
	volume = {86},
	year = {1999},
	month = {1999///},
	pages = {108 - 114},
	abstract = {Intensified ultraviolet-B radiation or UV-B (wavelengths between 280 and 320 nm) can delay flowering and diminish lifetime flower production in a few plants. Here we studied the effects of enhanced UV-B on floral traits crucial to pollination and pollinator reproduction. We observed simultaneous flowering responses of a new crop plant, Limnanthes alba (Limnathaceae), and a wildflower Phacelia campanularia (Hydrophyllaceae), to five lifetime UV-B dosages ranging between 2.74 and 15.93 kJ.m(-2).d(-1), Floral traits known to link plant pollination with bee host preference, host fidelity and larval development were measured. Intensified UV-B had no overall effect on nectar and pollen production of L. alba and P. campanularia flowers. A quadratic relationship between UV-B and nectar sugar production occurred in P. campanularia and showed that even subambient UV-B dosages can be deleterious for a floral trait. Other floral responses to UV-B were more dramatic and idiosyncratic. As UV-B dosage increased, L. alba plants were less likely to flower, but suffered no delays in flowering or reductions to lifetime flower production for those that did Bower. Conversely, an equal proportion of P. campanularia plants flowered under all UV-B treatments, but these same plants experienced delayed onset to bloom and produced fewer flowers at greater UV-B intensities. Therefore, intensified UV-B elicits idiosyncratic responses in flowering phenology and flower production from these two annual plants. Diurnal patterns in nectar and pollen production strongly coincided with fluctuating humidity and only weakly with UV-B dosage. Overall, our results indicated that intensified UVB can alter some flowering traits that impinge upon plant competition for pollinator services, as well as plant and pollinator reproductive success},
	keywords = {CLIMATE, COMPETITION, FLORAL DISPLAY, FLORAL REWARDS-NECTAR, FLORAL REWARDS-POLLEN, FLORAL TRAITS, FLORAL TRAITS-SIZE, FLOWER NUMBER, FLOWERING, HUMIDITY, HYDROPHYLLACEAE, NECTAR SECRETION, OSMIA, PHENOLOGY, POLLEN, POLLEN PRODUCTION, POLLINATION, POLLINATOR, REPRODUCTION, SUGAR, ULTRAVIOLET, WEATHER},
	author = {Sampson,B.J. and Cane, J. H.}
}
@article {1607,
	title = {Spatial predictability and resource specialization of bees (Hymenoptera: Apoidea) at a superabundant, widespread resource},
	journal = {Biological Journal of the Linnean Society, London},
	volume = {67},
	year = {1999},
	month = {1999///},
	pages = {119 - 147},
	abstract = {For reciprocal specialization (coevolution) to occur among floral visitors and their host plants the interactions must be temporally and spatially persistent However, studies repeatedly have shown that species composition and relative abundance off oral visitors vary dramatically at all spatial and temporal scales. We test the hypothesis that, on average, pollen specialist bee species occur more predictably at their floral hosts than pollen generalist bee species. Taxonomic floral specialization reaches its extreme among species of solitary, pollen-collecting bees, yet few studies have considered how pollen specialization by floral visitors influences their spatial constancy. We test this hypothesis using an unusually diverse bee guild that visits creosote bush (Larrea tridentata), the most widespread, dominant plant of the warm deserts of North America. Twenty-two strict pollen specialist and 80 + generalist bee species visit Larrea for its floral resources. The sites we sampled were separated by 0.5 to \&gt; 1450 km, and spanned three distinct deserts and four vegetation zones. We found that species of Larrea pollen specialist bees occurred at more sites and tended to be more abundant than generalists. Surprisingly, spatial turnover was high for both pollen specialist and generalist bee species at all distances, and species composition of samples from sites 1-5 km apart varied as much as repeat samples made at single sites. Nevertheless, the pattern of bee species turnover was not haphazard. As distance among sites increased faunal similarity of sites decreased. Faunal similarities among sites within 250 km of each other were generally greater than if randomly distributed over all sites (the null model). No single ecological category of species (widespread, localized, Larrea pollen specialist, floral generalist) accounted for this spatial predictability. Evidently, concordant local distribution patterns of many ecologically diverse species contribute to the non-random spatial pattern. The ecological dominance of creosote bush does not confer obvious ecological advantages to its specialist floral visitors. Spatial turnover is comparable to that found for bee guilds from other biogeographic regions of the world and is not therefore limited to those bee species that inhabit highly seasonal climates, such as deserts. Philopatry and differences in bloom predictability among sites are probably more important causes for spatial turnover of bee species than are interspecific competition for nest sites or floral resources},
	keywords = {Apoidea, BIOGEOGRAPHY, CLIMATE, COEVOLUTION, COMPETITION, CONSTANCY, EVOLUTION, GUILD, LARREA, MODEL, OLIGOLECTY, PHENOLOGY, POLLEN, SPECIATION, STATISTICS},
	author = {Minckley,R.L. and Cane, J. H. and Kervin,L. and Roulston,T.H.}
}
@article {1608,
	title = {Origins and ecological consequences of pollen specialization among desert bees},
	journal = {Proceedings of the Royal Society of London - Series B: Biological Sciences},
	volume = {267},
	year = {2000},
	month = {2000///},
	pages = {265 - 271},
	abstract = {An understanding of the evolutionary origins of insect foraging specialization is often hindered by a poor biogeographical and palaeoecological record. The historical biogeography (20 000 years before present to the present) of the desert-limited plant, creosote bush (Larrea tridentata), is remarkably complete. This history coupled with the distribution pattern of its bee fauna suggests pollen specialization For creosote bush pollen has evolved repeatedly among bees in the Lower Sonoran and Mojave deserts. In these highly xeric, floristically depauperate environments, species of specialist bees surpass generalist bees in diversity, biomass and abundance. The ability of specialist bees to facultatively remain in diapause through resource-poor years and to emerge synchronously with host plant bloom in resource-rich years probably explains their ecological dominance and persistence in these areas. Repeated origins of pollen specialization to one host plant where bloom occurs least predictably is a counter-example to prevailing theories that postulate such traits originate where the plant grows best and blooms most reliably Host-plant synchronization, a paucity of alternative floral hosts, or flowering attributes of creosote bush alone or in concert may account for the diversity of bee specialists that depend on this plant instead of nutritional factors or chemical coevolution between floral rewards and the pollinators they have evolved to attract},
	keywords = {Apoidea, BIOGEOGRAPHY, COEVOLUTION, DIAPAUSE, DIVERSITY, EVOLUTION, FLOWERING, LARREA, OLIGOLECTY, PHENOLOGY, POLLEN, POLLINATOR, SPECIATION},
	author = {Minckley,R.L. and Cane, J. H. and Kervin,L.}
}
