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Bee-plant relations were studied in the Guaritas region in subtropical Brazil. In this habitat most of the melittophilous plants are herbs, dwarf shrubs and succulents. Bees of about 250 species were recorded foraging on flowers of about 220 plant species. Approximately 30% of the bee species were recognized as oligolectic. a-diversity was particularly high in the bee families Anthophoridae and Halictidae. Evidently, the local apifauna comprises taxa originating from adjacent areas with temperate climate in Uruguay and Argentina. Further biogeographic and environmental conditions probably contributing to the species richness in this up to date little disturbed region are discussed as well as presumed coevolutionary links between the bee and plant partners in the numerous oligolectic foraging strategies observed in this community.

Studies on the pollination and breeding system of Echinodorus grandiflorus (Chamisso and Schlechtendal) Micheli were carried out on two natural populations in Vicosa, Minas Gerais State, southeastern Brazil. One population was formed by individuals of ssp. grandiflorus and the other by individuals of ssp. aureus (Fassett) Haynes and Holm-Nielsen. The flowering periods were within the rainy season. Flower anthesis occurred during the morning hours and flowers lasted ca. 8 h. E. grandiflorus ssp. grandiflorus is self-incompatible; few fruits, but many adventitious plantlets are produced at the inflorescences. E. grandiflorus ssp. aureus is self-compatible; many fruits and few adventitious plantlets are formed. Bees are the main flower visitors. The bee Protodiscelis echinodori (Colletidae) presents oligolectic foraging behavior, i.e., collects pollen from a single plant species or a group of related plant species.

In flowers of Cajophora arechavaletae Urb. the stamens are hidden from flower visitors in naviculate petals. In the male phase the stamens successively migrate at irregular intervals to the centre of the flower where they present pollen. Therefore, non-specialised pollinators cannot predict the time of pollen presentation. The oligolectic females of Bicolletes pampeana are effective pollinators of Cajophora arechavaletae. Females and males can elicit stamen movements by pressing the scales of the nectaries outwards with their head while taking up nectar. If this stimulus is responded to, up to 3 stamens move and reach the centre of the flower on average after 2.4 min. Experiments showed that the stimulus of nectar scale pressing was responded to maximally when the inter-stimulus interval was at least 14 min. B. pampeana females have evolved a foraging strategy which is adapted to the unique pollen presentation of C. arechavalete flowers. On microforaging routes they trapline 30–60 flowers and, therefore, most frequently come back to the same flower after intervals of about 3 min. This is exactly the period after which a female can expect pollen in the centre of the flower if her previous stimulus was responded to. Competition between the females causes them to return to the flowers at such short intervals.

Pollen digestion in larvae of the solitary bee Chelostoma florisomne (Megachilidae), a pollen-specialist (oligolectic) species on Ranunculus spp. (Ranunculaceae), was investigated using histological techniques. Serial sections from the anterior-, median-, and posterior-midgut/hindgut regions of the larval alimentary canal were selectively stained and examined for disappearance of lipids, proteins, and carbohydrates from ingested Ranunculus pollen grains. During digestion, pollen contents were observed to gradually extrude through the grain apertures. Most of the digestion of lipids and proteins occurred in the anterior- and median-midgut, whereas carbohydrates disappeared more slowly and mainly in the median- and posterior-midgut. In the hindgut, pollen comprised mainly empty exine shells, which were crushed and often broken, suggesting that some components of the wall are degraded during digestion, causing collapse of the outer, chemically resistant wall layer (exine). Lipids were completely digested, but small quantities of proteins and carbohydrates were often still present in grains in the posterior midgut/hindgut. The pollenkitt appeared to be completely absorbed, with none evident in the posterior midgut or in larval feces. The findings indicate that this oligolectic bee has the digestive equipment necessary to effectively remove and absorb the nutrients present in the pollen of its restricted food source. Comparison with similar studies in adult honey bees suggests that differing digestive abilities might be an underlying factor in pollen specialization in bees.

Opuntia brunneogemmia andO. viridirubra occur sympatrically in the Serra do Sudeste, Rio Grande do Sul, Brazil. Their flowers have 450–600 thigmonastic stamens and provide large amounts of pollen and nectar for bees. Bees of 41 species were registered at the flowers ofO. brunneogemmia and 30 at the flowers ofO. viridirubra. Females of three oligolectic species are the only effective pollinators:Ptilothrix fructifera (Anthophoridae),Lithurgus rufiventris (Megachilidae), andCephalocolletes rugata (Colletidae). During their visits inOpuntia-flowers, bees touch the filaments and stimulate the movement of the stamens to the centre of the flower. At the end of this movement, the anthers are densely packed around the style. As a consequence the pollen is presented in an easily accessible upper layer of anthers and various, nearly inaccessible lower layers. The lower layers contain about 80% of the pollen reward. Only females of the three oligolectic pollinators exploit the pollen from the lower layers and reach the nectar furrow. Therefore, through their stamen movements,Opuntia flowers hide most of their pollen from flower visitors but favour effectively pollinating, oligolectic bees.

A new species of leafcutter bee, Megachile (Megachiloides) chomskyi, is described from Texas, United States. Megachile chomskyi is one of the four known species of the oenotherae species group of Megachiloides, all members sharing the long tongue, and is most similar to M. (Megachiloides) amica Cresson. Like other members of the oenotherae species group, this species probably shows oligolecty with Onagraceae (Evening-Primrose Family). A diagnosis, full description of both sexes and a key to the species of the oenotherae species group are provided.

Bees are the main pollinators in terrestrial environments. Plants are sessile organisms that only attain cross-sexual reproduction through the activity of pollen vectors. As such, flowers offer hints for the interspecific encounter; they obtain pollination services and in exchange, usually, they provide floral resources to pollinators. The main resource sought by bees is pollen, which is used as larval nourishment. From the plants standpoint, however, there must be a balance between the offered resource and the amount of pollen grains effectively transferred to the stigmas. Such balance is dictated by a number of variables; pollinator attractivity, pollinator effectiveness, quantity of pollen exported/received and the energy allotted in the reproductive process. Aware of this paradox and observing that flowers exhibit specific traits associated with certain groups of pollinators (floral syndromes), there has been a tendency among researchers to evaluate flower evolution as if it were directed towards specialization. Nonetheless, specialization is associated to the referential group and behaves within a continuum of plain generalization and high specialization. I have studied two groups of bees: one a specialist and the other a generalist, although adapted to a rare niche among bees the nocturnal habit. I studied specialized bees of the genus Protodiscelis (Colletidae, Neopasiphaeinae), a group that exhibits feeding habit specialization, and their interaction with flowers. Protodiscelis bees are oligolectic, meaning that they are genetically determined to collect pollen grains for larval provisioning among phylogenetically constraint plant taxa. These bees will only gather pollen from species of the family Alismataceae, a group comprised of aquatic herbs common to lentic ecosystems. I investigated the pollination of four species belonging to this family and aimed to understand the plant-pollinator interactions within a spatial and morphofunctional frame, which also involves the floral cues used by the bees in order to find they preferred host flowers. I divided the obtained results into three upcoming publications, each dealing with one of the analyzed themes. The pollination of Echinodorus palaefolius was studied in several flooded areas in the Caatinga. Additionally I investigated the relationships between bees and flowers of five other species of the same genus (E. subalatus, E. glandulosus, E. paniculatus, E. pubescens e Echinodorus sp.). Echinodorus palaefolius is self-incompatible and relied on pollinators to develop fruits. The phenology of the species is dictated by the rain regime and flowers were visited by three bee species alone: Protodiscelis alismatis, Apis mellifera and Trigona spinipes. Surprisingly, the morphologically generalist flowers of this plant species are visited by an oligolectic bee (P. alismatis) and by the two among the most generalist of bees (A. mellifera and T. spinipes). The oligolectic species, however, was accounted with over 80% of flower visits. Bees of P. alismatis exhibit clear behavioral and morphological adaptations, such as extremely plumose setae that can hold the small pollen grains of Echinodorus. They were present in 96% of the 41 flooded areas that I sampled in the Caatinga. Bees of P. alismatis were also the main pollinators of the other species of Echinodorus collected within over 1,000 km of natural distribution of the Caatinga. The specialized relationship of these bees with their host plants is highly consistent in the insular environments of the Caatinga, where the aquatic Alismataceae naturally occur. The pollination ecology of three species of a neotropical clade limnocharitaceae (Alismataceae) was studied among distinct populations in northeast Brazil and middle-west Brazil. The results of pollination ecology were compared to those of H. martii, previously studied. I researched the morphological attributes and the aspects of the reproductive system that differentiate these species. Limnocharis flava, L. laforestii and Hydrocleys nymphoides were all visited by Protodiscelis palpalis, the same oligolectic species previously recognized as the sole effective pollinator of H. martii. Flowers of L. flava were found to be morphologically and functionally similar to those of H. martii. In both species, the presence of staminodes protect the pollen and bees of P. palpalis alone were effective pollinators, due to an adapted behavior that allows them to access the pollen chamber. The flowers of L. laforestii, on the other hand, were effectively pollinated by other species of bees, regardless of the presence of staminodes. But in this case, no protective pollen chamber is formed. In the population of the municipality of Serra Negra do Norte, P. palpalis was replaced by a yet undescribed species of Protodiscelis. For Limnocharis, however, animal pollen vectors are not required for fruit development and both studied species yielded high seed counts through autogamy. The flowers of H. nymphoides are larger and bear staminodes that do promote filtering of other bee species. Regardless of genetic self-incompatibility, H. nymphoides is pollinated by several generalist bee species, notably the social T. spinipes, A. mellifera and Bombus brevivilus (Apidae). Knowing that autogamy is one of the main variables for the establishment and dissemination of plants in biological invasions (Baker s Law), the occurrence of this type of pollination may largely explain the invasive status of the three studied species in Asia, Oceania and North America. The generalist association with pollinators would explain the invasions observed for H. nymphoides. I used the sampling method of dynamic headspace and gas chromatography coupled to mass spectrometry (GC-MS) to describe the volatile compounds emitted by the flowers of H. martii and H. nymphoides. I tested the attractivity of the main isolated compounds to bees of Protodiscelis palpalis in field conditions. Floral scents in the family Alismataceae were described for the first time. Flowers of H. martii produced a bouquet comprised of 22 compounds, whereas the bouquet of H. nymphoides contained 13 compounds. Each species, despite sharing several compounds, present a characteristic floral scent profile. Methoxylated benzenoids were the main constituents of the bouquets of H. martii and H. nymphoides. ρ-Methylanisole is the main compound in the floral scent of H. martii and 3,4-dimethoxytoluene the main compound in H. nymphoides. These two compounds, however, were isolated in both species. ρ-methylanisole, 2-methoxy-4-methylphenol, 3,4-dimethoxytoluene, 3,4,5-trimethoxytoluene and methyl salicylate were used in field biotests with artificial flowers assembled from yellow and blue adhesive paper. Only ρ-methylanisole yielded significantly more approaches from bees towards artificial flowers of both colors in comparison to control flowers. Artificial yellow flowers, however, proportionally attracted more bees than blue flowers. Ours results, the first ever obtained in a natural environment setting, show that a single volatile compound attracts female P. palpalis and is the most important communication channel between these pollinators and flowers of H. martii e H. nymphoides. Our results reinforce the fact that specific volatile compounds present in flower bouquets might be crucial for the localization of host plants by oligoletic bees. Bees of Megalopta (Halictidae, Augochlorini) are nocturnal and explore a niche that is mostly inaccessible to other bees. In the interaction between Megalopta bees and their host plants I studied one of the signals emitted by the flowers: floral scents. Scents have long been known as pollinator attractants, but little is known about the identity of the compounds produced by flowers and which among them incite behavioral responses of animals, such as pollinator attraction. I selected volatile compounds commonly isolated in floral scents and conducted field attraction biotests with Megalopta bees. I tackled the hypotheses that such common floral scent compounds, frequently identified in night-blooming angiosperms, would be involved in the attraction of Megalopta bees. I found out that single aromatic compounds effectively attracted female bees and elicited visiting behavior. Bees were significantly more attracted to traps baited with benzyl acetate, benzyl benzoate and methyl salicylate than to unbaited traps or traps baited with compounds less frequently isolated in night-blooming flowers (β-ionone, eucalyptol, eugenol and vanillin). I concluded that Megalopta bees use scents to find flowers under low-light conditions, as observed by several other groups of nocturnal pollinators. Moreover, I provided a new sampling technique for these rarely collected insects. Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES Abelhas são os principais polinizadores das plantas com flores. Plantas são sésseis e a reprodução sexuada cruzada somente ocorre através de vetores de pólen. Sendo assim, flores zoofílicas provêm pistas para o encontro interespecífico, são polinizadas e fornecem recursos florais aos polinizadores. O principal recurso coletado por abelhas herbívoros Apiformes é pólen, o principal alimento larval. Para as plantas, entretanto, existe um balanço entre recurso fornecido e quantidade de grãos de pólen efetivamente transportados para os estigmas. Esse balanço é regido por variáveis, entre elas a atratividade ao polinizador, a sua efetividade na polinização, a quantidade de pólen exportado e recebido e a quantidade de energia dispensada no processo reprodutivo. Considerando que flores apresentam atributos específicos para determinados grupos de polinizadores (síndromes florais), houve uma tendência entre os estudiosos da polinização de avaliar a evolução de flores como dirigida à especialização. Entretanto, a especialização é relativa ao grupo observado e se comporta dentro de um continuum entre amplamente generalista e altamente especialista. Estudei dois grupos de abelhas, um que apresenta especialização em pólen e outro generalista em relação aos recursos polínicos, mas ocupando um nicho raro entre abelhas, o hábito noturno. Estudei abelhas especializadas de Protodiscelis (Colletidae, Neopasiphaeinae) e sua interação com flores. Protodiscelis é um grupo de abelhas oligoléticas, ou seja coletam grãos de pólen para as larvas em flores do mesmo gênero ou família. As fêmeas coletam grãos de pólen exclusivamente em flores de Alismataceae, grupo formado por espécies aquáticas comuns a ambientes lênticos. Foi estudada a polinização de quatro espécies dessa família procurando entender a interação no âmbito espacial, morfofuncional e das pistas florais usadas pelas abelhas para encontrar as flores das quais dependem. Dividi os resultados obtidos em três manuscritos, cada um tratando de um dos temas analisados. A polinização de Echinodorus palaefolius foi estudada em vários alagados da caatinga. Adicionalmente, verifiquei as relações entre abelhas e flores de cinco outras espécies do mesmo gênero (E. subalatus, E. glandulosus, E. paniculatus, E. pubescens e Echinodorus sp.). Echinodorus palaefolius é autoincompatível e depende de polinizadores para a formação de frutos. Sua fenologia foi regida pelas chuvas e suas flores foram visitadas somente por três espécies de abelhas: Protodiscelis alismatis, Apis mellifera e Trigona spinipes. Surpreendentemente, as flores morfologicamente generalistas dessa espécie de planta, são visitadas por uma espécie oligolética (P. alismatis) e por duas das espécies de abelhas entre as mais generalistas conhecidas (A. mellifera e T. spnipes). A espécie oligolética, no entanto, foi responsável por mais de 80% das visitas às flores. Essa espécie de abelha tem comportamento e adaptações morfológicas claras, tais como pelos extremamente plumosos capazes de coletar os grãos de pólen pequenos de Echinodorus. Foram presentes em 96% dos 41 alagados que amostrei na caatinga. Abelhas de P. alismatis também foram os principais polinizadores das outras espécies de Echinodorus coletadas ao longo de mais de 1000 km da distribuição natural da caatinga. A relação especializada dessa espécie com suas plantas hospedeiras é muito consistente no ambiente insular na caatinga onde essas plantas aquáticas ocorrem. A polinização de Limnocharis flava, L. laforestii e Hydrocleys nymphoides, espécies do clado neotropical limnocharitaceas da família Alismataceae em várias populações no nordeste e centro-oeste brasileiro foram estudadas. Os resultados foram comparados com as características da associação entre H. martii e Protodiscelis palpalis, estudada anteriormente. VI Analisei os atributos morfológicos e o sistema reprodutivo que diferenciam essas espécies. As três espécies foram visitadas por Protodiscelis palpalis, mesma espécie oligolética e único polinizador efetivo de H. martii. Flores de L. flava foram morfo-funcionalmente semelhantes às de H. martii. Nessas duas espécies a presença de estaminódios protegem o pólen e somente P. palpalis, que apresenta comportamento adaptado para acessar a câmara de pólen, polinizou efetivamente as flores. Já nas flores de L. laforestii apesar da presença de estaminódios, abelhas de outras espécies polinizam as flores. Na população de Serra Negra do Norte, P. palpalis foi substituída por outra espécie de Protodiscelis ainda não descrita. Em Limnocharis, entretanto, não há necessidade de visitas para a formação de frutos. As duas espécies formaram sementes em grande quantidade por autogamia. As flores de H. nymphoides são maiores e os estaminódios mais curtos. Essa espécie autoincompatível é polinizada por várias espécies de abelhas generalistas principalmente sociais de T. spinipes, A. mellifera e Bombus brevivillus (Apidae). Visto que autogamia é uma das principais variáveis para estabelecimento e disseminação de plantas em invasões biológicas (Lei de Baker), a ocorrência desse tipo de polinização talvez possa explicar a condição de invasoras (na Ásia, Oceania e América do Norte) das três espécies estudadas. A relação generalista com polinizadores explicaria as invasões observadas para H. nymphoides. Utilizei as técnicas de headspace dinâmico e cromatografia gasosa acoplada à espectrometria de massa (GC-MS) para descrever os voláteis florais produzidos pelas flores de H. martii e H. nymphoides. Testei a atratividade dos principais compostos às abelhas de Protodiscelis palpalis em campo. Odores florais na família Alismataceae foram descritos pela primeira vez. As flores de H. martii produziram 22 compostos e H. nymphoides 13. Cada espécie, apesar de vários compostos em comum, tem seu perfil de odores característico. Benzenóides metoxilados foram os principais componentes dos buquês. ρ-metilanisol foi dominante em H. martii e 3,4-dimetoxitolueno em H. nymphoides. Os compostos florais ρ-metilanisol, 2-metoxi-4-metilfenol, 3,4-dimetoxitolueno, 3,4,5-trimetoxitolueno e salicilato de metila foram testados no campo em flores artificiais construídas com fita adesiva amarela e azul. Somente ρ-metilanisol atraiu significativamente mais abelhas à flores artificias das duas cores comparadas com as de controle. Flores amarelas atraíram proporcionalmente mais abelhas que azuis. Os nossos resultados, obtidos pela primeira vez para abelhas oligolétcas neotropicais e em ambiente natural, mostram que um único composto volátil atrai fêmeas de P. palpalis demonstrando que é o canal de comunicação mais importante entre P. palpalis e as flores de H. martii e H. nymphoides. Nossos resultados reforçam que os compostos voláteis específicos do buquê de flores são cruciais para a localização de plantas hospedeiras pelas abelhas oligolécticas. Abelhas de Megalopta (Halictidae, Augochlorini) são noturnas e exploram um nicho inacessível à outras abelhas. Nessa interação estudei os odores como sinal floral fornecido pelas flores. Odores há muito são conhecidos como atrativo de polinizadores, entretanto, pouco se sabe em relação à identidade dos compostos produzidos e que estimulam respostas comportamentais, tais como atração nos polinizadores. Selecionei odores comuns a buquês florais de plantas e os testei no campo na atratividade de abelhas Megalopta. Testei a hipótese de que odores florais comuns, amplamente produzidos por flores de antese noturna, seriam capazes de atrair abelhas de Megalopta. Encontrei que compostos aromáticos isolados foram capazes de atrair essas abelhas e eliciaram um comportamento de visita. As abelhas foram significativamente mais atraídas às armadilhas com acetato de benzila, benzoato de benzila e salicilato de metila como iscas do que outros compostos menos comuns em flores de antese noturna. Abelhas de Megalopta, dessa maneira, usam odores para encontrar flores nas condições de baixa luminosidade, tal como vários outros grupos de polinizadores noturnos.

Male bees can be abundant at flowers, particularly floral hosts of those bee species whose females are taxonomic pollen specialists (oligolecty). Contributions of male bees to host pollination are rarely studied directly despite their prevalence in a number of pollination guilds, including those of some crop plants. In this study, males of the oligolectic bee, Peponapis pruinosa Say, were shown to be effective pollinators of summer squash, Cucurbita pepo L. Seven sequential visits from male P. pruinosa maximized squash fruit set and growth. This number of male visits accumulated during the first hour of their foraging and mate searching at flowers soon after sunrise. Pollination efficacy of male P. pruinosa and their abundances at squash flowers were sufficient to account for most summer squash production at our study sites, and by extrapolation, to two-thirds of all 87 North American farms and market gardens growing squashes that were surveyed for pollinators by collaborators in the Squash Pollinators of the Americas Survey. We posit that the substantial pollination value of male Peponapis bees is a consequence of their species' oligolecty, their mate seeking strategy, and some extreme traits of Cucurbita flowers (massive rewards, flower size, phenology).

International audience; Females of Protodiscelis palpalis are oligolectic on flowers of the aquatic herb Hydrocleys martii (Limnocharitaceae), commonly found in Northeast Brazil. Each morning, 1 h before anthesis, males fight to guard small patches of flowers, which will compose their territories. Non-territorial males are not bound to certain areas on their patrol flights, roam between different territories and do not engage in conflicts with conspecific males. Territorial males aggressively defend flowers only in a restricted, intensely patrolled part of the territory. This core area was never shared with other territorial males. The intensive patrolling of a territory sector may be a response to abundant territorial invasions by conspecific males. Being territorial seems to confer reproductive advantages to the males. However, the severe male competition and the extreme spatio-temporal aggregation of resource flowers observed in the temporary water bodies of the Caatinga obscure which mating strategy provides higher male reproductive success.

Introduction The bees comprise a derived monophyletic group (Anthophila) of pollen-consuming (secondarily phytophagous) wasps of the superfamily Apoidea, and that diverged from a grade of predatory apoid wasps (formerly “Sphecidae”) sometime in the mid Cretaceous (~120–125 megaannum) (Michener 1944, 1979, 2007; Brothers 1975, 1998; Alexander 1992; Ronquist 1999; Engel 2001a, 2011; Danforth et al. 2006). Seven contemporary families are usually acknowledged: Andrenidae, Apidae, Colletidae, Halictidae, Melittidae, Megachilidae and Stenotritidae, including ~1200 genera and ~20 000 species (Michener 2007; Engel 2005, 2011). Two fossil families are also described: Paleomelittidae from middle Eocene Baltic amber, and a stem-group, Melittosphecidae from Cretaceous Burmese amber which, as discussed below, may or may not be a bee (Engel 2001a; Poinar and Danforth 2006; Ohl and Engel 2007). Bees likely arose concomitantly with the diversification of flowering plants (angiosperms) (Michener 1979; Grimaldi 1999; Engel 1996, 2001a; Crepet et al. 2004; Grimaldi and Engel 2005). Represented by more than 250 000 described species, angiosperms are the most diversified group of vascular plants, covering nearly all terrestrial and many aquatic habitats (Soltis and Soltis 2004). The congruent rise of flowering plants and numerous phytophagous insect lineages, such as bees, ditrysian Lepidoptera, and various flowering-visiting beetles and flies, has fuelled the notion of coradiation between these lineages. Such a conclusion is supported by the observation of flowers with specific combinations of traits that are correlated with particular pollinators (Bronstein et al. 2006). Selection for insect-pollinated clades is also supported by the fact that deliverance by pollinators of unconsumed pollen to the host plant’s female reproductive organs is clearly less stochastic and more efficient than alternative ancestral wind, water or gravity dispersive methods (Labandeira 1998). Lastly, association with pollinators increases opportunities for the evolution of specialization and subsequent diversification (Vamosi and Vamosi 2010).

Introduction Southern Africa, which is the region south of the Rivers Cunene and Zambezi, is one of the world’s bee diversity hotspots (Kuhlmann 2009). As bees are the most important pollinators of flowering plants, including crops, they are ecological and economic keystone species (Corbet et al. 1991; Allen-Wardell et al. 1998; Klein et al. 2007). Pollinators are believed to have played an important role in plant speciation in southern Africa, especially in the Cape Floral Kingdom (Kreft and Jetz 2007; van der Niet and Johnson 2008; Waterman et al. 2008). Notwithstanding the great economic, ecological, and evolutionary significance of wild bees, knowledge of this important group of pollinators and their floral relationships in this region is poor. Struck (1990, 1994a, 1994b, 1995) was the first to extensively study the relationships between flowers and solitary bees in southern Africa. In his pioneering work in Namaqualand, he used pollen analyses for recording flower visitation to investigate flower specialization of bees and other flower visiting insects. But due to taxonomic uncertainties in many of the bee genera in those days, the published data is of limited usefulness without the re-examination of the specimens, and thus it is not considered here.

We describe females and males of Osmia (Melanosmia) calaminthae sp. n., an apparent floral specialist on Calamintha ashei (Lamiaceae), and provide observations on the behavior of female bees on flowers of this plant. We also provide diagnostic information for Osmia (Diceratosmia) conjunctoides Robertson, stat. n., and synonymize O. (Diceratosmia) subfasciata miamiensis Mitchell with O. conjunctoides syn. n. Females of both O. calaminthae and O. conjunctoides are unique among North American Osmia forshort, erect, simple facial hairs, which are apparent adaptations for collecting pollen from nototribic flowers. Osmia calaminthae is currently only known from sandy scrub at four nearby sites in the southern Lake Wales Ridge in Highlands County, Florida, USA, while O. conjunctoides is known from limited but widespread sites in the southeastern USA. We discuss the conservation status of both species based on known or speculated floral associates and distributions.

To trace the evolution of host-plant choice in bees of the genus Chelostoma (Megachilidae), we assessed the host plants of 35 Palearctic, North American and Indomalayan species by microscopically analyzing the pollen loads of 634 females and reconstructed their phylogenetic history based on four genes and a morphological dataset, applying both parsimony and Bayesian methods. All species except two were found to be strict pollen specialists at the level of plant family or genus. These oligolectic species together exploit the flowers of eight different plant orders that are distributed among all major angiosperm lineages. Based on ancestral state reconstruction, we found that oligolecty is the ancestral state in Chelostoma and that the two pollen generalists evolved from oligolectic ancestors. The distinct pattern of host broadening in these two polylectic species, the highly conserved floral specializations within the different clades, the exploitation of unrelated hosts with a striking floral similarity as well as a recent report on larval performance on nonhost pollen in two Chelostoma species clearly suggest that floral host choice is physiologically or neurologically constrained in bees of the genus Chelostoma. Based on this finding, we propose a new hypothesis on the evolution of host range in bees.

Bees require large amounts of pollen for their own reproduction. While several morphological flower traits are known to have evolved to protect plants against excessive pollen harvesting by bees, little is known on how selection to minimize pollen loss acts on the chemical composition of pollen. In this study, we traced the larval development of four solitary bee species, each specialized on a different pollen source, when reared on non-host pollen by transferring unhatched eggs of one species onto the pollen provisions of another species. Pollen diets of Asteraceae and Ranunculus (Ranunculaceae) proved to be inadequate for all bee species tested except those specialized on these plants. Further, pollen of Sinapis (Brassicaceae) and Echium (Boraginaceae) failed to support larval development in one bee species specialized on Campanula (Campanulaceae). Our results strongly suggest that pollen of these four taxonomic groups possess protective properties that hamper digestion and thus challenge the general view of pollen as an easy-to-use protein source for flower visitors.

Apidologie, 39 (5), ISSN:0044-8435, ISSN:1297-9678

Bees, the largest (>16,000 species) and most important radiation of pollinating insects, originated in early to mid-Cretaceous, roughly in synchrony with the angiosperms (flowering plants). Understanding the diversification of the bees and the coevolutionary history of bees and angiosperms requires a well supported phylogeny of bees (as well as angiosperms). We reconstructed a robust phylogeny of bees at the family and subfamily levels using a data set of five genes (4,299 nucleotide sites) plus morphology (109 characters). The molecular data set included protein coding (elongation factor-1α, RNA polymerase II, and LW rhodopsin), as well as ribosomal (28S and 18S) nuclear gene data. Analyses of both the DNA data set and the DNA+morphology data set by parsimony and Bayesian methods yielded a single well supported family-level tree topology that places Melittidae as a paraphyletic group at the base of the phylogeny of bees. This topology (“Melittidae-LT basal”) is significantly better than a previously proposed alternative topology (“Colletidae basal”) based both on likelihood and Bayesian methods. Our results have important implications for understanding the early diversification, historical biogeography, host–plant evolution, and fossil record of bees. The earliest branches of bee phylogeny include lineages that are predominantly host–plant specialists, suggesting that host–plant specificity is an ancestral trait in bees. Our results suggest an African origin for bees, because the earliest branches of the tree include predominantly African lineages. These results also help explain the predominance of Melittidae, Apidae, and Megachilidae among the earliest fossil bees.

In recent decades, the development of strategies to prevent or slow the loss of biodiversity has become an important task for ecologists. In most terrestrial ecosystems wild-bees play a key role as pollinators of herbs, shrubs and trees. The scope of this thesis was to study 1) pollinator effectiveness of specialist bees vs. generalist flower-visitors, 2) critical floral resources for wild-bees, and 3) methods to estimate the size of wild-bee populations. The wild-bee species Andrena hattorfiana and A. marginata were used as model species. These two species are specialized on pollen from the plant family Dipsacaceae. The bee A. hattorfiana was found to be a frequent visitor but a poor pollinator of its preferred food-plant Knautia arvensis. The female bees exert such a strong preference for pollen-producing inflorescences that they likely have deleterious effects on the plant, harvesting valuable pollen that could have been transferred to conspecific stigmas by other flower-visitors. To explore the relationship between wild-bees and their food-plants, the concept of pollen budget was developed. We quantified pollen production in the food-plant population and pollen consumption of wild-bee nests. A survey of the visitation by all flower-visitor taxa indicated that the degree of utilization (the fraction of the total pollen amount that is harvested and utilized by A. hattorfiana) varied from 12% to 80% among K. arvensis populations (N=26). The bee Andrena marginata utilized 44% of the pollen production in a population of Succisa pratensis. The pollen budget suggests that with an average flower-visitor diversity and abundance, 330 individuals of the food-plant K. arvensis are required to sustain a population of 20 A. hattorfiana ♀ (the approximate median natural population size). Based on a study of A. hattorfiana, considerable simplifications were proposed for the commonly used mark-recapture design for measuring wild-bee population size. For this species, population size estimated based on mark-recapture data was strongly correlated with the number of observations per survey-walk. The results suggest that large-scale surveys of solitary bee species can be simplified by performing survey-walks. The pollen budget and the method proposed for estimating the size of bee populations have the potential to become valuable tools for monitoring and management of wild-bee populations.

Protomeliturga catimbaui sp. nov., do Parque Nacional Vale do Catimbau, Buique, Pernambuco é a segunda espécie de Protomeliturgini. Protomeliturga turnerae (Ducke, 1907) foi coletada em Turnera ulmifolia Linnaeus, é oligoléctica e muito comum no Nordeste do Brasil. Os machos de Protomeliturga catimbaui sp. nov. apresentam diversos desenhos alaranjadas no meso e no metassoma, tegumento brilhante com pontuação fina e o sétimo esterno projetado para trás em forma de espata arredondada com carenas laterais e dentes látero-apicais. As abelhas foram coletadas em flores de Turneraceae (Piriqueta sidifolia (Cambess.) Urb. var. multiflora Urb.), indicando oligolectia também para esta espécie. Protomeliturga catimbaui sp. nov., from the National Park Vale do Catimbau, Buique, Pernambuco is the second species of Protomeliturgini. Protomeliturga turnerae (Ducke, 1907) was collected in flowers of Turnera ulmifolia Linnaeus, is oligolectic and very common in Northeast Brazil. The males of Protomeliturga catimbaui sp. nov. show several orange colored paintings on meso and metassoma, a shining tegument with fine punctures and sternite 7 is projected backwards in the shape of a rounded spata with lateral carina and apicolateral teeth. The bees were collected in flowers of Turneraceae (Piriqueta sidifolia (Cambess.) Urb. var. multiflora Urb.), indicating oligolecty also for this species.

A critical issue in pollination ecology is the evolution of generalist pollination systems, and under which conditions floral specializations evolve from these. The gynodioecious herb Knautia arvensis (Dipsacaceae) exhibits a generalized pollination system, but is visited by both generalist and specialist flower-visitors. The present study tested pollinator effectiveness and pollinator importance of the pollen specialist solitary bee Andrena hattorfiana (Andrenidae) vs. the generalist flower-visitors to K. arvensis on the island of Oland, SE Sweden. Females of the specialist bee removed more pollen per inflorescence-visit than the major groups of generalist visitors such as bumblebees and flies. They also deposited more pollen per inflorescence-visit than any of the generalist visitor groups. The females have a preference for pollen-presenting vs. stigma-presenting inflorescences, a pattern shared with most of the generalist flower-visitors. Females of the specialist exert such a strong preference that they, despite their great pollinator effectiveness, make modest contribution to pollen transfer in K. arvensis. The females of A. hattorfiana accounted for 14.2% of the overall visits and 5.8% of the total pollination, the rest being performed by generalist visitors and males of A. hattorfiana. This study shows that pollinator effectiveness of a specialist can be superior while generalist flower-visitors select floral characters towards generalization through their greater contribution to overall pollen flow.

If trade-offs between flexibility to use a range of host species and efficiency on a limited set underlie the evolution of diet breadth, one resulting prediction is that specialists ought to be more restricted than generalists in their ability to use novel resource species. I used foraging tests and feeding trials to compare the ability of a generalist and a specialist solitary mason bee species to collect and develop on two pollen species that are not normally used in natural populations (novel pollens). Osmia lignaria (Hymenoptera: Megachilidae) is a generalist pollen feeder; O. californica, is more specialized. Adults of the specialist were more limited in use of novel hosts, but only in some contexts. Both bee species refused to collect one novel pollen. The specialist accepted a second novel pollen only when it was presented along with its normal pollen, whereas the generalist collected novel pollen whether presented alone or with normal pollen. Surprisingly, larvae of the specialist were more flexible than were generalists. The specialist grew well on mixtures of normal and novel pollen species, in some cases better than on its normal host alone. Larvae of the generalist grew more poorly on all diets containing novel pollens than on their normal host. Data on these two species of bees suggest that specialization by itself need not reduce flexibility on novel hosts. The findings also provide information about mechanisms of specialization in bees. Similar to some folivores, specific cues of the pollen host and the bee's interpretation of these contribute, along with foraging economics, to pollen choice by adults. The ability of the larvae to cope with specific components of one pollen species need not interfere with its ability to use others.

Eusociality is a major evolutionary innovation involving alterations in life history, morphology, and behavior. Advanced eusocial insects, such as ants, termites, and corbiculate bees, cannot provide insights into the earliest stages of eusocial evolution because eusociality in these taxa evolved long ago (in the Cretaceous) and close solitary relatives are no longer extant. In contrast, primitively eusocial insects, such as halictid bees, provide insights into the early stages of eusocial evolution because eusociality has arisen recently and repeatedly. By mapping social behavior onto well-corroborated phylogenies, I show that eusociality has arisen only three times within halictid bees (contrary to earlier estimates of six or more origins). Reversals from eusocial to solitary behavior have occurred as many as 12 times, indicating that social reversals are common in the earliest stages of eusocial evolution. Important attributes of social complexity (e.g., colony size, queen/worker dimorphism) show no obvious association with phylogeny, and some reversals to solitary nesting are related to host-plant switches (from polylecty to oligolecty). These results provide a glimpse of social evolution in its earliest stages and provide insights into the early evolution of advanced eusocial organisms.

The halictid bees of the genera Dufourea Lepeletier de Saint Fargeau (Rophitinae) and Dieunomia Cockerell (Nomiinae) occurring in Michigan are reviewed. Two new records for Michigan are provided: Dufourea harveyi (Cockerell), new status, and Dieunomia heteropoda (Say). This is also the first published record of D. harveyi in the eastern United States. The occurrence of Dieunomia in southwest Michigan is the first record of the subfamily Nomiinae for the state. Information on the biology and distribution of each species is summarized. An identification key to the Dufourea of the eastern United States is provided.

Bees are phytophagous insects that exhibit recurrent ecological specializations related to factors generally different from those discussed for other phytophagous insects. Pollen specialists have undergone extensive radiations, and specialization is not a always a derived state. Floral host associations are conserved in some bee lineages. In others, various species specialize on different host plants that are phenotypically similar in presenting predictably abundant floral resources. The nesting of solitary bees in localized areas influences the intensity of interactions with enemies and competitors. Abiotic factors do not always explain the intraspecific variation in the spatial distribution of solitary bees. Foods stored by bees attract many natural enemies, which may shape diverse facets of nesting and foraging behavior. Parasitism has evolved repeatedly in some, but not all, bee lineages. Available evidence suggests that cleptoparasitic lineages are most speciose in temperate zones. Female parasites frequently have a suite of characters that can be described as a masculinized feminine form. The evolution of resource specialization (including parasitism) in bees presents excellent opportunities to investigate phenotypic mechanisms responsible for evolutionary change.

The anthophorid bee, Habropoda (= Emphoropsis [R. W. Brooks, personal communication]) laboriosa (F.), is a locally abundant, vernal, univoltine species. It flies from February through April in Georgia and Alabama. In these states, females are oligolectic on Vaccinium spp., particularly V. ashei Reade and V. corymbosum L., with Gelsemium sempervirens (L.), Quercus alba L., and Cercis canadensis L. as minor, alternate pollen hosts. Pollen-harvesting female H. laboriosa sonicate V. ashei flowers to release pollen, averaging 5.7 buzzes during their average 2.6-s floral visit, which is a handling rate 3 times faster than coforaging Bombus spp. Furthermore, mean floral handling rates of H. laboriosa females at V. ashei are individually more uniform than those of coforaging, polylectic Bombus spp., a hitherto undemonstrated but expected evolutionary outcome of oligolecty. Sonicated pollen accumulates on a ventral cephalic “safe site” of both sexes, which is the common site of V. ashei stigmatic contact. Floral probes are strictly legitimate (no robbing). Based upon its relative abundance at Vaccinium spp., phenology, floral handling behaviors and rates, and pollen preferences in the southeastern United States, we conclude that H. laboriosa is an oligolege adapted to species of Vaccinium for its pollen and nectar resources.

The specialist bee, Hoplitis anthocopoides, foraged for pollen from Echium vulgare, its preferred plant, more efficiently than did four generalist species. Efficiency was measured as the weight of pollen (the larval food) harvested from Echium flowers per unit handling time, divided by the weight of the discrete pollen mass required to rear one offspring. This measure of efficiency corresponds more closely to reproductive output than does the usual measure, net energy gained per unit time. The specialists produced more potential offspring per unit handling time because they manipulated flowers faster and collected more pollen per flower than did generalists. The specialists also flew between flowers more rapidly than did the generalists. The specialists did not defend the flowers against generalists. These results support the assumption in models of resource partitioning and optimal foraging theory, and in hypotheses explaining the evolution of pollen-specializing bee species, that specialists are more efficient at using their preferred resources than are generalists.

Bees play an important and necessary role in the pollination of agricultural crops grown for fruit and seed and of forage and browse plants important in range management for production of both livestock and game animals. Nearly 20,000 different kinds of bees are now known, some, like the imported honey bee, the bumble bees, and the stingless bees of the tropics, are social and live together in colonies subject to manipulation and movement from place to place. However, by far the majority of bees are solitary, living in burrows in the ground, in wood, or in plant stems, where they store pollen and nectar as food for their young. Many of these take pollen only from certain kinds of plants and are very efficient pollinators of these. Others, like the honey bee, visit a wide variety of pollen plants, both native and introduced. Although management procedures have been developed for certain crops in certain areas which permit the effective use of honey bees for increased production through better pollination, these are not universally applicable to our agriculture as a whole. For certain crops, both cultivated and wild, supplemental pollination is necessary. The development of management procedures which will permit increased utilization of native solitary bees and perhaps lead to the importation of foreign species native to the areas in which our agricultural crops originated, requires a detailed knowledge of the ecology, or environmental relationships, of these bees. This article is intended to review as briefly as possible, the current status of our knowledge of the subject and to indicate published papers in which various aspects may be pursued further. Prominence has been given to publications of the last fifteen years and to those which are most comprehensive and include references to earlier literature. Factors which appear to have had an influence in the economy, evolution, and survival of solitary bees have been especially emphasized.

The interaction between plants and extremely diverse habitats and environmental conditions of California has resulted in rapid evolution in many plant groups. A small number of studies suggest that evolution in many of these groups has been accompanied and perhaps paralleled by evolution in particular groups of bees (Linsley and MacSwain, 1957, 1959; Linsley et al., 1963a, 1963b; 1964; Thorp, 1969). The interaction between these bees and their pollen plants is oligolectic. An oligolectic relationship is defined by Linsley and MacSwain (1957, 1958) as one ". . . in which the individual members of the population, throughout its range and in the presence of other pollen sources, consistently and regularly collect pollen from but a single plant species or from a group of similar or related plant species, turning to other sources, if at all, only when there is a local shortage or absence of that pollen." Oligolectic relationships may be nonselective or co-evolved. Included in the first class are Andrena linsleyi Timberlake, which collects pollen of Oenothera deltoides Torr. and Frem. in the morning after sphinx-moths have pollinated the flowers (Linsley et al., 1963; Gregory, 1964), and Andrena nemophilae Ribble which is discussed below. Such a bee must adapt to the evolutionary vicissitudes of the flower and its pollinator(s). The second class includes those bees which are pollinators of the host plant. Thus they may influence the evolution of the plant as well as being influenced by the plant. This group of bees and their pollen plants are of particular interest to the student of pollination biology and evolution. Although a number of studies have dealt with oligolectic bees, the basis of the relationship remains an enigma. The flight period of most oligolectic bees is short and the adult bee's only previous contact with a particular pollen source is the pollen and nectar it consumed as a larva. Three explanations have been suggested to explain oligolecty. First, it is genetically controlled (Thorp, 1969). Second, a preimaginal conditioning from the pollen and nectar that the larva consumes (Linsley, 1958). Third, some combination of the above, i.e., genetical control modified by conditioning (Thorp, 1969). In this paper my objectives are (1) to present a broad picture of the plant Nemophila menziesii H. and A. s.l. and its pollinators and (2) to re-examine particular questions concerning evolution within oligolectic bees. Specifically, I discuss the distribution, floral behavior and breeding system of the plant, Nemophila as a bee plant, the oligolectic Nemophila bees, the role of polylectic bees in pollination, and fly pollination. In the final section I discuss host plant recognition and evolution in oligolectic bees

The bee genus Diadasia Patton is a relatively large group of solitary or gregarious ground nesting species. It occurs only in the Western Hemisphere and is abundantly represented in southwestern United States and Mexico and in the arid and semi-arid portions of South America, but is rare in the moist tropics (Michener, 1954). Biological characteristics of Diadasia have been discussed elsewhere (Linsley, MacSwain and Smith, 1952, 1956; Linsley and MacSwain, 1957). It is the object of the present paper to emphasize the role that food habits and flower relationships may have had in evolution and speciation in the group. As with most organisms, food habits have played an important role also in the evolution and speciation of bees. The choice of larval food, as is usually the case with plant feeding insects, is made by the adult. The bee larva, to survive, must accept the food since it is unable to make an alternative choice. The larval food is pollen, usually mixed with some nectar, gathered from flowers by the female bee. However, bees visit flowers for a variety of reasons, other than pollen collecting. Flowers provide adult food (especially nectar) for both sexes of all species, the site of mating for many, and a male sleeping place for others. Of all these functions, the collection of pollen by females invokes the most consistently specific response to flower species, although, in some cases, the mating search by males may be equally so. Bees in which the females are highly specific in their choice of pollen sources are termed oligolectic, those which are not specific, polylectic. Flower constancy in the collection of pollen is a characteristic of bees in general. Two principal forms of constancy are involved. The first is characteristic of individual bees which, on one or several successive trips, may gather pure or nearly pure loads of pollen from a single kind of plant, although the species as a whole may be polylectic and not sharply limited in the kind and number of pollen sources utilized. This type of constancy has long been known to floral biologists, students of insect behavior, and research workers in certain production aspects of agriculture. It is characteristic of social bees (e.g. Apis, Bombus, Melipona), semisocial bees (e.g. Halictus), and many solitary bees (e.g., some Anthophora, Andrena, Megachile). The second kind of constancy was partially recognized by Loew (1886) and was more clearly defined by Robertson (1925).1 It is adaptive in nature and is characteristic of species, genera, and even higher groups of bees. This form of flower constancy is

Bees, like their wasp relatives, forage for and transport food to a nest as provisions for their offspring. Unlike female Sphecoidea which transport arthropods one at a time as prey, bees transport pollen requiring specialized scopal (brush) or corbicular (fringed plate) structures to transport the dustlike material externally. Scopae often exhibit further modifications in density and amount of plumosity in relation to the size and ornamentation of the pollen grains they transport. Bees also differ from sphecid wasps by possessing branched body hairs that are relatively densely packed. These hairs, the electrostatic surface potential, and specialized hair groups for extraction of hidden pollen are important in the acquisition of pollen from flowers. Structures for grooming (brushes, combs, and scrapers) and grooming behavior patterns are modified to permit manipulation and packing of pollen in the specialized transport structures. The addition of nectar, so that pollen is packed moist, is a behavior that permits the carrying of pollen of a great variety of sizes and ornamentations in relatively simplified scopae or in corbiculae. The addition of oils to the diet of some bees has resulted in a modified type of scopal structure that has a wooly area basally and stiff guard hairs extending distally and that can transport a mixture of oil and pollen. Special hairs on the fore and mid basitarsi and teeth of hind tibial spurs are modified as oil scraper and manipulation structures. The use of corbiculae in Apidae to transport nesting materials and the hind tibiae in male orchid bees (Euglossini: Apidae) for transporting aromatic compounds involves behavior patterns similar to those for pollen transport in grooming, manipulating, and packing the materials. Other behavioral and physiological adaptations important in the location and acquisition of pollen by bees include individual constancy, oligolecty, seasonal synchrony, preimaginal conditioning, daily synchrony, buzz pollination, and other responses to specific modes of pollen presentation. Most of the behavioral patterns involve learning. They may be modified by extrinsic factors, and they may modify intrinsic structural and physiological characters.

The papers presented in this symposium focus on the reciprocity between plants and their associated fauna. Some studies approach plant-pollinator interactions at generic or familial levels and treat distributions over broad expanses of evolutionary time (e.g. Beattie, Gentry, and Ramirez). Others examine selected habitats and community interactions on ecological time scales (e.g. Ayensu, Heithaus, Macior, and Strong). Generally, one goal is to document specific boundaries which allow definition of floral resources relative to specific faunal consumers. I want to relate some of these new findings to recent research on consumer "switching" between alternative food resources. Early studies of pollination did not consider the gathering of pollen and nectar as generalized modes of foraging, but Robertson (1899) did recognize the similarity when he stated, "The relations of the host-bees to the flowers from which they get pollen are quite analogous to the relations of parasites to their hosts, of phytophagous insects to their food plants, or of predaceous insects to the insects upon which they feed ...." Pollination ecologists currently use terminologies and classifications for describing pollinator behavior which are different from those applied to predatory behavior, but there is a continued recognition of the general similarity between these distinct types of foraging. For instance, a pollinator which visits a single plant species for pollen and nectar is termed "monotropic," and Faegri and Pijl (1971) comment, similar to Robertson, that "its relation to the blossom is more or less on the lines of a host-parasite relationship." Michener (1954) has also noted that bees which collect pollen from a few kinds of flowers (termed "oligolecty") represent a "form of host specificity" (for a review of these terms seeLiusley, 1959). Yet, there has been little attempted transfer of methodologies from related studies on selective predation to the techniques used for studying selective pollination. In the following discussion, I propose an extension of a measure that I have recently developed for determining "rate of resource substitutability" among selective consumers (Covich, 1972a) to studies of pollinator energetics. Before discussing these points, I want to compare plant-pollinator and preypredator interactions. By definition, a pollinator is a dispersal agent for highly specialized pollen grains which transmit genetic information and produce sexual recombination and heterozygosis. Being direct links in the reproductive pathways of many flowering plants, pollen transporters have a strong influence on floral evolution and are tightly coupled to development of complex morphological and biochemical adaptations. Predators also have a direct effect on their prey populations, but predation (in the strict sense) can have a less intense impact if non-reproductive individuals (immature, weakened, or senescent com