The Bee Community (Hymenoptera: Apoidea: Apiformis) of an Area in the Border of the Caatinga Doma... more The Bee Community (Hymenoptera: Apoidea: Apiformis) of an Area in the Border of the Caatinga Domain (Itatim, BA-Brazil) ABSTRACT-Several standardized surveys of bee communities undertaken in Brazil in the last few decades have allowed a comparative approach to the search for generalized patterns of community structure. In this paper the results of a standardized year-round bee survey undertaken in Itatim, Northeastern Brazil, in the semi-arid caatinga domain (12 º 42'S; 39 º 46'W) are presented. The main objective was to investigate the composition of community, the relative abundance of the species and their flight periods. Bees were collected monthly, from september/1996 to november/1997, totaling 180h. The total of 1189 specimens were collected, belolging to 60 species. Apidae was the most diversified family, with 37 species. The genera with more species were Centris Fabricius, Megachile Latreille, and Xylocopa Latreille. A high dominance was observed, as in most of caatinga areas already studied. Apis mellifera L. was the predominant species, with 51% of the total number of individuals captured, and occurred all year long. The other predominant species had a much lower abundance, as: Dialictus opacus (Moure) (6.2%), Perditomorpha sp. (4.0%), Trigona spinipes (Fabricius) (3.8%), Frieseomelitta languida (Moure) (3.7%) and Xylocopa grisescens Lepeletier (3.0%). It is suggested that some characteristics of the community are due to its ecotonal nature, as the presence of some species with a probable marginal occurrence in the caatinga, and the extended period of flight activities of Megachilidae, Halictidae and Colletidae, resulting in a high number of species in activity during the driest four months of the year.
As plantas visitadas pela abelha africanizada Apis mellifera L. para obtenção de recursos florais... more As plantas visitadas pela abelha africanizada Apis mellifera L. para obtenção de recursos florais foram estudadas em uma área de caatinga (Itatim, Bahia, Nordeste do Brasil). Um total de 588 forrageadoras foi coletado visitando 33 espécies de plantas. Sterculiaceae, Erythroxylaceae, Mimosaceae e Rhamnaceae foram as famílias botânicas mais freqüentemente visitadas. Apis mellifera apresentou nicho trófico amplo (2,71), todavia poucas plantas foram importantes como fontes de pólen e néctar. Cerca de 80% dos indivíduos foram coletados em dez espécies de plantas, sendo Melochia tomentosa e Erythroxylon catingae as plantas mais freqüentemente visitadas. A similaridade encontrada entre a flora visitada por A. mellifera em Itatim e em outra área de caatinga distante 30 km foi baixa (0,17), e diferentes espécies de plantas foram mais freqüentemente visitadas em cada área. Isto pode resultar de diferenças na composição florística das comunidades assim como de diferenças na quantidade de recur...
The conservation of the fauna of bees inhabiting the Brazilian savanna is threatened due to chang... more The conservation of the fauna of bees inhabiting the Brazilian savanna is threatened due to changes in land use in the last decades. We investigated the composition, species richness and abundance of a bee assemblage in the vicinity of the Chapada Diamantina National Park. In addition, we compiled data on composition and diversity from another bee assemblage located in the same portion of the Cerrado, which was previously investigated by one of us almost 30 years ago, in order to produce a more complete panorama on beta diversity of bees in this region. We used a non-metric multidimensional scaling ordination analysis (NMDS) to compare composition of bee assemblages from diff erent types of open vegetation. We recorded 77 bee species (H’ = 2.95; J = 0.68), 42% of them were singletons. We collected slightly more than half of the species and 60% of the genera recorded in the bee assemblage studied three decades ago. H’ was signifi cantly lower in our area than in the previous study (t...
In this study were examined the species richness and seasonal abundance of cavity-nesting bees in... more In this study were examined the species richness and seasonal abundance of cavity-nesting bees in areas of dry semi-deciduous forest and caatinga in the State of Bahia, Brazil. Sampling was done employing two types of trap-nests: bamboo canes and tubes made of black cardboard with dimensions of either 58 x 6 mm or 105 x 8 mm. The traps were inspected once a month. One hundred and forty-six nests of 11 bee species were collected in the forest, and 121 nests of seven species were collected in the caatinga. Five species of cleptoparasitic bees were also reared from these nests. The highest nesting frequencies occurred in the wet season in both areas. Nests parasitism was important only for Centris tarsata Smith, 1874, and was higher at the caatinga site than in the forest. The mortality of pre-emergent adults was high, especially in C. tarsata , Tetrapedia diversipes Klug, 1810 and Euglossa cordata (Linnaeus, 1758). Information on the number of cells per nest, the size, shape, and arra...
Resumo: O trabalho apresenta resultados sobre riqueza e abundância de Apoidea em ambiente de tran... more Resumo: O trabalho apresenta resultados sobre riqueza e abundância de Apoidea em ambiente de transicao restinga-mata atlântica e compara as afinidades da apifauna entre habitats contiguos na faixa litorânea no Nordeste do Brasil. As coletas foram realizadas no Parque Metropolitano de Pituacu, Salvador- Bahia (S12o59’52.7” W38o27’05.4”) e as abelhas foram capturadas em visita as flores em intervalos semanais de outubro de 1997 a dezembro de 1998. Foram capturados 4700 individuos separados em 80 especies e 35 generos. Foi observada maior abundância de abelhas nos meses de outubro e novembro de 1997 e entre fevereiro e abril de 1998. A familia Apidae apresentou maior numero de individuos (78,5%), generos (78,9%) e especies (80%). A familia Halictidae foi a segunda mais abundante com 191 individuos capturados (2,3%). As tribos com maior representatividade de individuos foram Meliponini (67,9%), Centridini (11,3%), Euglossini (5%) e Xylocopini (3,6%). Aquelas com maior riqueza foram Cent...
Nests of Centris tarsata Smith, 1874 were obtained from trap-nests in areas of dry semi-deciduous... more Nests of Centris tarsata Smith, 1874 were obtained from trap-nests in areas of dry semi-deciduous forest (Baixa Grande) and caatinga (Ipira), in the State of Bahia. Nesting occurred in bamboo canes and in tubes of black cardboard with 5.8 cm (= small tube) and 10.5 cm (= large tube) in length and 0.6 and 0.8 cm in diameter, respectively. In both areas C. tarsata nested during the wet season producing four generations in Baixa Grande and three generations in Ipira. The immatures of one generation underwent diapause at both sites. The bees con- structed their nests with a mixture of sand and oil. In general, the cells were elongated and arranged in linear series with its opening pointing towards the nest entrance. Completed nests had two to three cells in small tubes, one to seven cells in large tubes, and two to 13 cells in bamboo canes. The nest plug resembled an uncompleted cell and was externally covered with oil. The cells were provisioned with pollen, oil, and nectar. Nests were
In this study we investigated the group of floral resources that support bee populations from a b... more In this study we investigated the group of floral resources that support bee populations from a bee assemblage in a savanna, and the way in which bee species use these food resources, with an emphasis on the breadth and overlap of trophic niches. The interactions between 75 species of bees and 62 species of plants visited to obtain floral resources were recorded on a Brazilian savanna site. The bee species explored a diverse set of plant species, but concentrated the collection of resources in a few plant species. The distribution of the samples over a long period favored a robust characterization of the food niche of the bee populations. Byrsonima sericea, Serjania faveolata, and Stigmaphyllon paralias were the plant species with the highest number of links with bees. In general, the trophic niche overlap was low, with 75% of pairs of bee species having a niche overlap (NO) less than 0.33. Only four pairs showed high overlap (NO>0.70) and all cases were related to the exploitati...
The ideal cavity dimensions for neotropical cavity-nesting bees with the potential to be managed ... more The ideal cavity dimensions for neotropical cavity-nesting bees with the potential to be managed as pollinators have not been getting proper attention. We investigated whether the occupancy of trap-nests by Centris analis Fabricius and Tetrapedia diversipes Klug, and other nesting aspects, are affected by different trap-nest length. The used trap-nests were cardboard tubes 5, 10, 15 and 20 cm in length, and Ø 8 mm. Occupation rates of 10-cm trap-nests by C. analis was higher than that of the 5-cm ones (χ2=11.17, gl=1, p<0.001). On the other hand, there was not difference between the occupation rates of 10 and 15-cm long trap-nests (χ2=0.51, gl=1, p=0.48), and between the ones measuring 15 and 20 cm long (χ2=1.36, gl=1, p=0.24). T. diversipes occupied a smaller number of 5-cm trap-nests than the 10-cm ones (χ2=1.52, gl=1, p=0.22), as well as that the 15-cm ones were more occupied than the 10-cm trap-nests (χ2=4.23, gl=1, p=0.04); moreover, there was not difference between the occu...
Some solitary bees establish their nests in preexisting cavities. Such nesting behavior facilitat... more Some solitary bees establish their nests in preexisting cavities. Such nesting behavior facilitates the investigation of their life history, as well as the monitoring of their populations in natural, semi-natural and cropped habitats. This study aimed to evaluate the acceptance of artificial substrates by cavity-nesting bees in a heterogeneous landscape. We investigated the percentage of occupation of the different trap-nests, the monthly fluctuations in the nesting activity, offspring sex ratio, mortality and parasitism, in two phytophysiognomies: herbaceous-shrub restinga (site 1) and arboreal restinga (site 2). We used as trap-nests, bamboo canes, large and small straws of cardboard inserted into solid wooden blocks. Five bee species established 193 nests, from which 386 adults emerged. Centris tarsata Smith was the most abundant species. Large straws were signifi cantly more occupied than small straws (χ² = 19.951; df = 1; p < 0.0001). Offspring mortality rate for unknown rea...
Oil bees exploit host plants for resources to feed the adults and offspring, as well as for the c... more Oil bees exploit host plants for resources to feed the adults and offspring, as well as for the construction of their nests. The aim of the current study is to investigate how the species in this guild distribute their foraging effort, and the range in their niche overlap levels. The bees were sampled for six months, during their visits to the flowers in a savanna (“cerrado”). These oil-bee species explored the floral resources provided by 13 plant species. The trophic niche of the most abundant species, Centris aenea Lepeletier, was relatively narrow, similarly to those of Epicharis species. Low overlap of trophic niches (TrNO≤30%) was most commonly found. The distribution of bee visits to the host plants revealed redundancy in the floral resource exploitation. However, the foraging concentration levels in some key plants were different for distinct oil-bee species, and it contributed to the low overlap of niches between many pairs of species
Variations in abundance and species richness among communities are often determined by interactio... more Variations in abundance and species richness among communities are often determined by interactions between biotic and abiotic factors. However, for communities composed of species that share a common specialization (such as similar foraging adaptations) it may be a key ecological factor involved in the common specialization that affects community variations. To evaluate this possibility, we characterized the guild of oil-collecting bees of a Neotropical savanna in Brazil and tested whether differences in Byrsonima abundance and availability of floral oil explain differences in species richness and abundance of oil-collecting bees of different tribes. Both the number of species and total abundance of Centridini species increased with the abundance of Byrsonima. One plausible explanation for the stronger adjustment between the abundance of Centridini and Byrsonima is that the abundance of these plants affects not only the availability of floral oil, but also of pollen. These findings...
Pollination is an ecosystem service sustained by a differentiated use of resources among sympatri... more Pollination is an ecosystem service sustained by a differentiated use of resources among sympatric species. The bee size can influence the similarity in the use of resources, and poricidal anthers limit the access to pollen. Therefore, we evaluated the influence of body size and the anther type of pollen sources in Centridini-flower interaction network. We expected that the low niche overlap, promoted by these morphological parameters, would result in the formation of subgroups and lead to greater network resilience. We studied 15 bee species (n =73 females) and identified their pollen sources. The bee size and anther type influenced the formation of subgroups in the community, and the larger bees used a higher proportion of flowers with poricidal anthers. Only the anther type influenced the robustness of the network. We conclude that the parameters analyzed influence both the use of resources by oil-collecting bees and their food niche breadth. pollen analysis / robustness / ecosystem services / solitary bees / trophic niche
Centris flavifrons is a ground-nesting solitary bee species that has an important role in crop an... more Centris flavifrons is a ground-nesting solitary bee species that has an important role in crop and native plant species pollination in the Neotropical region. However, the nesting biology and ecology of this species are little understood. We studied the nesting biology of C. flavifrons by observing 287 nests in an urban garden. Females built nests only during the dry season from September to March and exhibit notable flexibility in the amount of time each nest is active and the number of brood cells produced as a consequence. Nests were established on horizontal, sunny, sandy surfaces without vegetation. Our nest excavations revealed a main tunnel with lateral branches and an average of five cells per nest (range, 1-12 cells). The duration of a nest from digging to closure was on average 6.9 days (range of 2-19 days, n=141) with 69 % of nests active for 2-7 days. Mesoplia regalis was observed entering the nests and emerged from the cells of C. flavifrons, but the parasitism rate was low. The implications of this flexibility in nest activity duration and brood cell number and the low pressure from parasites are discussed. nesting ecology / ground nesting / solitary bees / oil collecting bees / Mesoplia regalis
This study aimed to characterize the importance of the sources of floral resource used by Centris... more This study aimed to characterize the importance of the sources of floral resource used by Centris analis to provision nests in acerola orchards (the West Indian cherry, Malpighia emarginata). Thirty-six pollen types were recognized in larval provisions, of which the most frequently found were M. emarginata (76 %), Cajanus cajan (11 %), Chamaecrista type 1 (3 %), and Solanum paniculatum (3 %). The pollen-type M. emarginata was registered in 98 % of the brood cells, with monthly frequencies from 30 to 99 %. The trophic niche breadth (H′) of the larvae of C. analis was 1.24, with monthly variations from 0.04 to 1.44. The richness of pollen types found in larval provisions of C. analis may be considered high compared to results obtained in other agrosystems with cultivated acerola. The high relative frequency of the pollen-type M. emarginata strongly affected trophic niche breadth and equitativity in the use of food resources. This crop provides floral resources (pollen and floral oils) needed by the pollinator C. analis throughout the year in the region.
Pollen sources used by Centris tarsata bees were identified in an area of "caatinga" vegetation (... more Pollen sources used by Centris tarsata bees were identified in an area of "caatinga" vegetation (Canudos Biological Station) in NE Bahia, NE Brazil, by analyzing the pollen residues encountered in the nests. The analysis of the pollen residues was performed by pulverizing the sediments used to construct the cells, followed by the application of the acetolysis method. Thirty-one pollen types were identified belonging to 13 botanical families (in associations of from 4 to 15 distinct pollen types per nest), indicating which plants were used by the bees to feed their offspring. The plant families most represented were Leguminosae and Malpighiaceae, while the pollen types most frequently found were Chamaecrista ramosa (46.5%), Senna rizzinii (19.7%), and Solanum paniculatum (19.6%). The identification of the pollen types and information about the resources offered by the plants indicated that many species were visited as nectar sources rather than as pollen or oil sources by C. tarsata. entomopalynology / pollen / solitary bees / Centris / caatinga
We conducted a comparative analysis of bee-plant and wasp-plant interaction networks, aiming at t... more We conducted a comparative analysis of bee-plant and wasp-plant interaction networks, aiming at the identification of similarities and differences between networks of flower-visiting groups with direct or indirect mutualism with plants. We measured for each network: number of social bees and social wasps, number of plants visited (P), degree of nestedness, number of observed (I) and possible interactions, connectance (C), and interaction density (D). The network formed by pooling together social bees and social wasps exhibited 25 species (12 bees and 13 wasps) and 49 visited plants, with a connectance of 15.34%. The wasp-plant network had higher connectance (C = 21.24) than the bee-plant network (C = 15.79). Both the social wasp-plant and the social bee-plant network were significantly nested, they presented structure more nested than all randomly generated matrices (n = 1 000). Both interaction networks have similar topologies and are nested, asymmetrical and modular structures. flower-visiting guild / food network / trophic interactions / semi-arid region
Trophic niche breadth and niche overlap of bees were studied in a region of Caatinga (a deciduous... more Trophic niche breadth and niche overlap of bees were studied in a region of Caatinga (a deciduous dry thorn scrub forest) in Brazil with the lowest mean annual rainfall of the country, highly seasonal environmental variation, and an unpredictable rainy season. A null model approach was used to determine if the observed niche overlap in the community differed from that expected by chance. In general, even bee species with wider trophic niches concentrated foraging efforts on flowers of only a few of the available plant species, with low trophic niche overlap between pairs of species and among all species in the community. A randomization test showed niche overlap among the 10 common species in the guild to be significantly less than expected by chance, suggesting the existence of functional complementarity. The structure of communities defined by high functional complementarity is likely to be more sensitive to variation in available resources (e.g., richness and abundance of floral resources for bees). Ecosystem services provided by such communities may be more greatly affected by environmental changes (anthropogenic activities and climate change) than are services provided by communities with greater functional redundancy. stingless bees / Apoidea / solitary bees / Caatinga / semiarid / niche overlap
The Bee Community (Hymenoptera: Apoidea: Apiformis) of an Area in the Border of the Caatinga Doma... more The Bee Community (Hymenoptera: Apoidea: Apiformis) of an Area in the Border of the Caatinga Domain (Itatim, BA-Brazil) ABSTRACT-Several standardized surveys of bee communities undertaken in Brazil in the last few decades have allowed a comparative approach to the search for generalized patterns of community structure. In this paper the results of a standardized year-round bee survey undertaken in Itatim, Northeastern Brazil, in the semi-arid caatinga domain (12 º 42'S; 39 º 46'W) are presented. The main objective was to investigate the composition of community, the relative abundance of the species and their flight periods. Bees were collected monthly, from september/1996 to november/1997, totaling 180h. The total of 1189 specimens were collected, belolging to 60 species. Apidae was the most diversified family, with 37 species. The genera with more species were Centris Fabricius, Megachile Latreille, and Xylocopa Latreille. A high dominance was observed, as in most of caatinga areas already studied. Apis mellifera L. was the predominant species, with 51% of the total number of individuals captured, and occurred all year long. The other predominant species had a much lower abundance, as: Dialictus opacus (Moure) (6.2%), Perditomorpha sp. (4.0%), Trigona spinipes (Fabricius) (3.8%), Frieseomelitta languida (Moure) (3.7%) and Xylocopa grisescens Lepeletier (3.0%). It is suggested that some characteristics of the community are due to its ecotonal nature, as the presence of some species with a probable marginal occurrence in the caatinga, and the extended period of flight activities of Megachilidae, Halictidae and Colletidae, resulting in a high number of species in activity during the driest four months of the year.
As plantas visitadas pela abelha africanizada Apis mellifera L. para obtenção de recursos florais... more As plantas visitadas pela abelha africanizada Apis mellifera L. para obtenção de recursos florais foram estudadas em uma área de caatinga (Itatim, Bahia, Nordeste do Brasil). Um total de 588 forrageadoras foi coletado visitando 33 espécies de plantas. Sterculiaceae, Erythroxylaceae, Mimosaceae e Rhamnaceae foram as famílias botânicas mais freqüentemente visitadas. Apis mellifera apresentou nicho trófico amplo (2,71), todavia poucas plantas foram importantes como fontes de pólen e néctar. Cerca de 80% dos indivíduos foram coletados em dez espécies de plantas, sendo Melochia tomentosa e Erythroxylon catingae as plantas mais freqüentemente visitadas. A similaridade encontrada entre a flora visitada por A. mellifera em Itatim e em outra área de caatinga distante 30 km foi baixa (0,17), e diferentes espécies de plantas foram mais freqüentemente visitadas em cada área. Isto pode resultar de diferenças na composição florística das comunidades assim como de diferenças na quantidade de recur...
The conservation of the fauna of bees inhabiting the Brazilian savanna is threatened due to chang... more The conservation of the fauna of bees inhabiting the Brazilian savanna is threatened due to changes in land use in the last decades. We investigated the composition, species richness and abundance of a bee assemblage in the vicinity of the Chapada Diamantina National Park. In addition, we compiled data on composition and diversity from another bee assemblage located in the same portion of the Cerrado, which was previously investigated by one of us almost 30 years ago, in order to produce a more complete panorama on beta diversity of bees in this region. We used a non-metric multidimensional scaling ordination analysis (NMDS) to compare composition of bee assemblages from diff erent types of open vegetation. We recorded 77 bee species (H’ = 2.95; J = 0.68), 42% of them were singletons. We collected slightly more than half of the species and 60% of the genera recorded in the bee assemblage studied three decades ago. H’ was signifi cantly lower in our area than in the previous study (t...
In this study were examined the species richness and seasonal abundance of cavity-nesting bees in... more In this study were examined the species richness and seasonal abundance of cavity-nesting bees in areas of dry semi-deciduous forest and caatinga in the State of Bahia, Brazil. Sampling was done employing two types of trap-nests: bamboo canes and tubes made of black cardboard with dimensions of either 58 x 6 mm or 105 x 8 mm. The traps were inspected once a month. One hundred and forty-six nests of 11 bee species were collected in the forest, and 121 nests of seven species were collected in the caatinga. Five species of cleptoparasitic bees were also reared from these nests. The highest nesting frequencies occurred in the wet season in both areas. Nests parasitism was important only for Centris tarsata Smith, 1874, and was higher at the caatinga site than in the forest. The mortality of pre-emergent adults was high, especially in C. tarsata , Tetrapedia diversipes Klug, 1810 and Euglossa cordata (Linnaeus, 1758). Information on the number of cells per nest, the size, shape, and arra...
Resumo: O trabalho apresenta resultados sobre riqueza e abundância de Apoidea em ambiente de tran... more Resumo: O trabalho apresenta resultados sobre riqueza e abundância de Apoidea em ambiente de transicao restinga-mata atlântica e compara as afinidades da apifauna entre habitats contiguos na faixa litorânea no Nordeste do Brasil. As coletas foram realizadas no Parque Metropolitano de Pituacu, Salvador- Bahia (S12o59’52.7” W38o27’05.4”) e as abelhas foram capturadas em visita as flores em intervalos semanais de outubro de 1997 a dezembro de 1998. Foram capturados 4700 individuos separados em 80 especies e 35 generos. Foi observada maior abundância de abelhas nos meses de outubro e novembro de 1997 e entre fevereiro e abril de 1998. A familia Apidae apresentou maior numero de individuos (78,5%), generos (78,9%) e especies (80%). A familia Halictidae foi a segunda mais abundante com 191 individuos capturados (2,3%). As tribos com maior representatividade de individuos foram Meliponini (67,9%), Centridini (11,3%), Euglossini (5%) e Xylocopini (3,6%). Aquelas com maior riqueza foram Cent...
Nests of Centris tarsata Smith, 1874 were obtained from trap-nests in areas of dry semi-deciduous... more Nests of Centris tarsata Smith, 1874 were obtained from trap-nests in areas of dry semi-deciduous forest (Baixa Grande) and caatinga (Ipira), in the State of Bahia. Nesting occurred in bamboo canes and in tubes of black cardboard with 5.8 cm (= small tube) and 10.5 cm (= large tube) in length and 0.6 and 0.8 cm in diameter, respectively. In both areas C. tarsata nested during the wet season producing four generations in Baixa Grande and three generations in Ipira. The immatures of one generation underwent diapause at both sites. The bees con- structed their nests with a mixture of sand and oil. In general, the cells were elongated and arranged in linear series with its opening pointing towards the nest entrance. Completed nests had two to three cells in small tubes, one to seven cells in large tubes, and two to 13 cells in bamboo canes. The nest plug resembled an uncompleted cell and was externally covered with oil. The cells were provisioned with pollen, oil, and nectar. Nests were
In this study we investigated the group of floral resources that support bee populations from a b... more In this study we investigated the group of floral resources that support bee populations from a bee assemblage in a savanna, and the way in which bee species use these food resources, with an emphasis on the breadth and overlap of trophic niches. The interactions between 75 species of bees and 62 species of plants visited to obtain floral resources were recorded on a Brazilian savanna site. The bee species explored a diverse set of plant species, but concentrated the collection of resources in a few plant species. The distribution of the samples over a long period favored a robust characterization of the food niche of the bee populations. Byrsonima sericea, Serjania faveolata, and Stigmaphyllon paralias were the plant species with the highest number of links with bees. In general, the trophic niche overlap was low, with 75% of pairs of bee species having a niche overlap (NO) less than 0.33. Only four pairs showed high overlap (NO>0.70) and all cases were related to the exploitati...
The ideal cavity dimensions for neotropical cavity-nesting bees with the potential to be managed ... more The ideal cavity dimensions for neotropical cavity-nesting bees with the potential to be managed as pollinators have not been getting proper attention. We investigated whether the occupancy of trap-nests by Centris analis Fabricius and Tetrapedia diversipes Klug, and other nesting aspects, are affected by different trap-nest length. The used trap-nests were cardboard tubes 5, 10, 15 and 20 cm in length, and Ø 8 mm. Occupation rates of 10-cm trap-nests by C. analis was higher than that of the 5-cm ones (χ2=11.17, gl=1, p<0.001). On the other hand, there was not difference between the occupation rates of 10 and 15-cm long trap-nests (χ2=0.51, gl=1, p=0.48), and between the ones measuring 15 and 20 cm long (χ2=1.36, gl=1, p=0.24). T. diversipes occupied a smaller number of 5-cm trap-nests than the 10-cm ones (χ2=1.52, gl=1, p=0.22), as well as that the 15-cm ones were more occupied than the 10-cm trap-nests (χ2=4.23, gl=1, p=0.04); moreover, there was not difference between the occu...
Some solitary bees establish their nests in preexisting cavities. Such nesting behavior facilitat... more Some solitary bees establish their nests in preexisting cavities. Such nesting behavior facilitates the investigation of their life history, as well as the monitoring of their populations in natural, semi-natural and cropped habitats. This study aimed to evaluate the acceptance of artificial substrates by cavity-nesting bees in a heterogeneous landscape. We investigated the percentage of occupation of the different trap-nests, the monthly fluctuations in the nesting activity, offspring sex ratio, mortality and parasitism, in two phytophysiognomies: herbaceous-shrub restinga (site 1) and arboreal restinga (site 2). We used as trap-nests, bamboo canes, large and small straws of cardboard inserted into solid wooden blocks. Five bee species established 193 nests, from which 386 adults emerged. Centris tarsata Smith was the most abundant species. Large straws were signifi cantly more occupied than small straws (χ² = 19.951; df = 1; p < 0.0001). Offspring mortality rate for unknown rea...
Oil bees exploit host plants for resources to feed the adults and offspring, as well as for the c... more Oil bees exploit host plants for resources to feed the adults and offspring, as well as for the construction of their nests. The aim of the current study is to investigate how the species in this guild distribute their foraging effort, and the range in their niche overlap levels. The bees were sampled for six months, during their visits to the flowers in a savanna (“cerrado”). These oil-bee species explored the floral resources provided by 13 plant species. The trophic niche of the most abundant species, Centris aenea Lepeletier, was relatively narrow, similarly to those of Epicharis species. Low overlap of trophic niches (TrNO≤30%) was most commonly found. The distribution of bee visits to the host plants revealed redundancy in the floral resource exploitation. However, the foraging concentration levels in some key plants were different for distinct oil-bee species, and it contributed to the low overlap of niches between many pairs of species
Variations in abundance and species richness among communities are often determined by interactio... more Variations in abundance and species richness among communities are often determined by interactions between biotic and abiotic factors. However, for communities composed of species that share a common specialization (such as similar foraging adaptations) it may be a key ecological factor involved in the common specialization that affects community variations. To evaluate this possibility, we characterized the guild of oil-collecting bees of a Neotropical savanna in Brazil and tested whether differences in Byrsonima abundance and availability of floral oil explain differences in species richness and abundance of oil-collecting bees of different tribes. Both the number of species and total abundance of Centridini species increased with the abundance of Byrsonima. One plausible explanation for the stronger adjustment between the abundance of Centridini and Byrsonima is that the abundance of these plants affects not only the availability of floral oil, but also of pollen. These findings...
Pollination is an ecosystem service sustained by a differentiated use of resources among sympatri... more Pollination is an ecosystem service sustained by a differentiated use of resources among sympatric species. The bee size can influence the similarity in the use of resources, and poricidal anthers limit the access to pollen. Therefore, we evaluated the influence of body size and the anther type of pollen sources in Centridini-flower interaction network. We expected that the low niche overlap, promoted by these morphological parameters, would result in the formation of subgroups and lead to greater network resilience. We studied 15 bee species (n =73 females) and identified their pollen sources. The bee size and anther type influenced the formation of subgroups in the community, and the larger bees used a higher proportion of flowers with poricidal anthers. Only the anther type influenced the robustness of the network. We conclude that the parameters analyzed influence both the use of resources by oil-collecting bees and their food niche breadth. pollen analysis / robustness / ecosystem services / solitary bees / trophic niche
Centris flavifrons is a ground-nesting solitary bee species that has an important role in crop an... more Centris flavifrons is a ground-nesting solitary bee species that has an important role in crop and native plant species pollination in the Neotropical region. However, the nesting biology and ecology of this species are little understood. We studied the nesting biology of C. flavifrons by observing 287 nests in an urban garden. Females built nests only during the dry season from September to March and exhibit notable flexibility in the amount of time each nest is active and the number of brood cells produced as a consequence. Nests were established on horizontal, sunny, sandy surfaces without vegetation. Our nest excavations revealed a main tunnel with lateral branches and an average of five cells per nest (range, 1-12 cells). The duration of a nest from digging to closure was on average 6.9 days (range of 2-19 days, n=141) with 69 % of nests active for 2-7 days. Mesoplia regalis was observed entering the nests and emerged from the cells of C. flavifrons, but the parasitism rate was low. The implications of this flexibility in nest activity duration and brood cell number and the low pressure from parasites are discussed. nesting ecology / ground nesting / solitary bees / oil collecting bees / Mesoplia regalis
This study aimed to characterize the importance of the sources of floral resource used by Centris... more This study aimed to characterize the importance of the sources of floral resource used by Centris analis to provision nests in acerola orchards (the West Indian cherry, Malpighia emarginata). Thirty-six pollen types were recognized in larval provisions, of which the most frequently found were M. emarginata (76 %), Cajanus cajan (11 %), Chamaecrista type 1 (3 %), and Solanum paniculatum (3 %). The pollen-type M. emarginata was registered in 98 % of the brood cells, with monthly frequencies from 30 to 99 %. The trophic niche breadth (H′) of the larvae of C. analis was 1.24, with monthly variations from 0.04 to 1.44. The richness of pollen types found in larval provisions of C. analis may be considered high compared to results obtained in other agrosystems with cultivated acerola. The high relative frequency of the pollen-type M. emarginata strongly affected trophic niche breadth and equitativity in the use of food resources. This crop provides floral resources (pollen and floral oils) needed by the pollinator C. analis throughout the year in the region.
Pollen sources used by Centris tarsata bees were identified in an area of "caatinga" vegetation (... more Pollen sources used by Centris tarsata bees were identified in an area of "caatinga" vegetation (Canudos Biological Station) in NE Bahia, NE Brazil, by analyzing the pollen residues encountered in the nests. The analysis of the pollen residues was performed by pulverizing the sediments used to construct the cells, followed by the application of the acetolysis method. Thirty-one pollen types were identified belonging to 13 botanical families (in associations of from 4 to 15 distinct pollen types per nest), indicating which plants were used by the bees to feed their offspring. The plant families most represented were Leguminosae and Malpighiaceae, while the pollen types most frequently found were Chamaecrista ramosa (46.5%), Senna rizzinii (19.7%), and Solanum paniculatum (19.6%). The identification of the pollen types and information about the resources offered by the plants indicated that many species were visited as nectar sources rather than as pollen or oil sources by C. tarsata. entomopalynology / pollen / solitary bees / Centris / caatinga
We conducted a comparative analysis of bee-plant and wasp-plant interaction networks, aiming at t... more We conducted a comparative analysis of bee-plant and wasp-plant interaction networks, aiming at the identification of similarities and differences between networks of flower-visiting groups with direct or indirect mutualism with plants. We measured for each network: number of social bees and social wasps, number of plants visited (P), degree of nestedness, number of observed (I) and possible interactions, connectance (C), and interaction density (D). The network formed by pooling together social bees and social wasps exhibited 25 species (12 bees and 13 wasps) and 49 visited plants, with a connectance of 15.34%. The wasp-plant network had higher connectance (C = 21.24) than the bee-plant network (C = 15.79). Both the social wasp-plant and the social bee-plant network were significantly nested, they presented structure more nested than all randomly generated matrices (n = 1 000). Both interaction networks have similar topologies and are nested, asymmetrical and modular structures. flower-visiting guild / food network / trophic interactions / semi-arid region
Trophic niche breadth and niche overlap of bees were studied in a region of Caatinga (a deciduous... more Trophic niche breadth and niche overlap of bees were studied in a region of Caatinga (a deciduous dry thorn scrub forest) in Brazil with the lowest mean annual rainfall of the country, highly seasonal environmental variation, and an unpredictable rainy season. A null model approach was used to determine if the observed niche overlap in the community differed from that expected by chance. In general, even bee species with wider trophic niches concentrated foraging efforts on flowers of only a few of the available plant species, with low trophic niche overlap between pairs of species and among all species in the community. A randomization test showed niche overlap among the 10 common species in the guild to be significantly less than expected by chance, suggesting the existence of functional complementarity. The structure of communities defined by high functional complementarity is likely to be more sensitive to variation in available resources (e.g., richness and abundance of floral resources for bees). Ecosystem services provided by such communities may be more greatly affected by environmental changes (anthropogenic activities and climate change) than are services provided by communities with greater functional redundancy. stingless bees / Apoidea / solitary bees / Caatinga / semiarid / niche overlap
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