03499nas a2200349   4500008004100000245012600041210006900167260001200236300001400248490000700262520256400269653001202833653001702845653001202862653001602874653001602890653001402906653001402920653001002934653001102944653001002955653001502965653001402980653001102994653001503005653001503020100001903035700001703054700001503071700001903086856004403105       1999                        eng d00aSpatial predictability and resource specialization of bees (Hymenoptera: Apoidea) at a superabundant, widespread resource0 aSpatial predictability and resource specialization of bees Hymen  c1999///  a119 - 1470 v673 aFor 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 resources10aApoidea10aBIOGEOGRAPHY10aCLIMATE10aCOEVOLUTION10aCOMPETITION10aCONSTANCY10aEVOLUTION10aGUILD10aLARREA10aMODEL10aOLIGOLECTY10aPHENOLOGY10aPOLLEN10aSPECIATION10aSTATISTICS1 aMinckley, R.L.1 aCane, J., H.1 aKervin, L.1 aRoulston, T.H.  uhttps://apoidea.myspecies.info/node/13802289nas a2200313   4500008004100000245008300041210006900124260001200193300001400205490000800219520147200227653001201699653001701711653001601728653001301744653001401757653001401771653001401785653001101799653001501810653001401825653001101839653001501850653001501865100001901880700001701899700001501916856004401931       2000                        eng d00aOrigins and ecological consequences of pollen specialization among desert bees0 aOrigins and ecological consequences of pollen specialization amo  c2000///  a265 - 2710 v2673 aAn 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 attract10aApoidea10aBIOGEOGRAPHY10aCOEVOLUTION10aDIAPAUSE10aDIVERSITY10aEVOLUTION10aFLOWERING10aLARREA10aOLIGOLECTY10aPHENOLOGY10aPOLLEN10aPOLLINATOR10aSPECIATION1 aMinckley, R.L.1 aCane, J., H.1 aKervin, L.  uhttps://apoidea.myspecies.info/node/13102761nas a2200337   4500008004100000245012300041210006900164260001200233300001400245490000700259520186300266653000902129653001202138653001302150653001602163653001402179653001402193653001002207653001202217653001102229653001202240653001102252653001202263653002402275653001402299100001902313700001702332700001502349700001502364856004402379       2003                        eng d00aBiological impediments to measures of competition among introduced honey bees and desert bees (Hymenoptera: Apiformes)0 aBiological impediments to measures of competition among introduc  c2003///  a306 - 3190 v763 aForaging behaviors, host plant breadth, and agilities of social and solitary bee species differ dramatically. We illustrate how these phenomena can obscure the effects of floral resource competition from our studies on a species-rich, native bee fauna that visit the flowers of creosote bush [Larrea tridentata Coville (Zygophyllaceae)], a widespread dominant perennial plant species in the warm deserts of North America. The potential for competition among the solitary bees that visit creosote bush and honey bees was investigated by two methods: one that is widely used asks if solitary bee abundance and species diversity is less at sites with greater honey bee abundance; and a second. more novel approach that asks if pollen availability is limiting at sites with high bee biomass. We found no relationship among number of honey bees at sited and species richness and abundance of all native bees combined or of Pollen specialist species considered alone. Protein represented in the pollen of the primary host plant greatly exceeded the biomass of bees present at a site. We suggest bee populations are rarely pollen limited in this system or that competition, when it occurs, is highly episodic. Future studies of bee competition will need to assess long-term Population variation among solitary and introduced bees in habitats where floral resources can be measured for multiple flowering plant species, and where bee colony/nest dynamics can be documented, Studies of bee faunas in temperate areas are needed. This paper demonstrates some of the possible pitfalls for studies of competition among highly eusocial and solitary bees, We conclude that basic data (in bee biology and population dynamics are needed before these questions can be satisfactorily answered and, at present, little hard data are available to evaluate the competing hypotheses10aAPIS10aApoidea10aBEHAVIOR10aCOMPETITION10aDIVERSITY10aFLOWERING10aGUILD10aHABITAT10aLARREA10aMETHODS10aPOLLEN10aPROTEIN10aRESOURCE LIMITATION10aVARIATION1 aMinckley, R.L.1 aCane, J., H.1 aKervin, L.1 aYanega, D.  uhttps://apoidea.myspecies.info/node/11702433nas a2200253   4500008004100000245014800041210006900189260001200258300001400270490000700284520167700291653001201968653001601980653002301996653001002019653001102029653001502040653001402055100001702069700001702086700001502103700001702118856004402135       2005                        eng d00aTemporally persistent patterns of incidence and abundance in a pollinator guild at annual and decadal scales: the bees of Larrea tridentata0 aTemporally persistent patterns of incidence and abundance in a p  c2005///  a319 - 3290 v853 aA recent alternative model to conventional coevolution, the geographic mosaic theory of coevolution, posits that reciprocal selection is episodic and local, rather than persistent and spatially extensive. However, little empirical evidence addresses this model’s tenets, in particular the temporal stability of local plant-pollinator interactions. We evaluated this tenet using the richly diverse guild of bees at creosote bush (Larrea tridentata), a generalist plant that hosts many specialist bees. We systematically resampled over 2-5 years at 11 sites across the south-western USA. Incidence and abundance also were compared for survey sites sampled 20 2 years earlier. Average Morisita-Horn faunal similarities of local bee guilds was 87% for sequential years and 36% after 20 years. Similarities in taxonomic composition of resampled local bee guilds could be statistically represented as a random assemblage drawn from the regional source pool of 54-68 bee species that could be expected at Larrea, weighted by regional abundance. At every site, only the minority of abundant bee species was typically persistent in local guilds, even after > 20 years. Most bee species in the Larrea guild were chronically uncommon, geographically sporadic and temporally unpredictable, attributes that render them numerically inconsequential as pollinators in their local guild. Persistence among abundant bee species in local pollinator assemblages satisfies one condition by which reciprocal selection could act locally. The well-being of these more abundant core species, and not bee diversity per se, may better characterize the health of such plant-pollinator associations.10aApoidea10aCOMMUNITIES10aECOLOGY-HISTORICAL10aGUILD10aLARREA10aPOLLINATOR10aVARIATION1 aCane, J., H.1 aMinckley, R.1 aKervin, L.1 aRoulston, T.  uhttps://apoidea.myspecies.info/node/106