Cândida Maria Lima Aguiar

Nesting biology of Centris (Hemisiella) tarsata Smith (Hymenoptera, Apidae, Centridini)

Ninhos de Centris tarsata Smith, 1874 foram obtidos atraves da utilizacao de ninhos-armadilha, em areas de floresta estacional semi-decidua (Baixa Grande) e de caatinga (Ipira), no Estado da Bahia. A nidificacao ocorreu em gomos de bambus e em tubos de cartolina preta, estes com comprimentos de 5,8 cm (= tubos pequenos) e 10,5 cm (= tubos grandes), e diâmetro de 0,6 e 0,8 cm, respectivamente. Em ambas as areas C. tarsata nidificou durante a estacao umida, produzindo quatro geracoes anuais em Baixa Grande e tres em Ipira. Os imaturos de uma das geracoes passaram por diapausa em ambos os locais. As abelhas construiram seus ninhos com uma mistura de areia e oleo. Em geral, as celulas foram alongadas e arranjadas em serie linear, com sua abertura dirigida para a entrada do ninho. Os ninhos completados tinham de duas a tres celulas nos tubos pequenos, de uma a sete celulas nos tubos grandes e de duas a 13 nos gomos de bambu. A parede de fechamento do ninho lembrava uma celula incompleta e era coberta externamente com oleo. As celulas foram aprovisionadas com polen, oleo e nectar. Os ninhos foram parasitados por Mesocheira bicolor (Fabricius, 1804) (Hymenoptera, Apidae) e por outra especie de abelha nao identificada.

Utilização de recursos florais por abelhas (Hymenoptera, Apoidea) em uma área de Caatinga (Itatim, Bahia, Brasil)

This study was designed to identify important food resource plants used by bee species in a Caatinga area, as well as describe the local patterns of floral use by bees. A total of 1,145 foraging bees, belonging to 60 species, were captured while visiting 50 plant species. Melochia tomentosa L., Sida galheirensis Ulbr., Erythroxylon catingae P. Cowan, and Ziziphus cotinifolia Reiss. were the most frequently visited plants. Melochia tomentosa, Solanum paniculatum L. and S. galheirensis were visited by larger number of bee species. Some oligolectic bees were identified. Apis mellifera Linnaeus, 1758 and Trigona spinipes (Fabricius, 1793) had the largest trophic niche breadth (2.71 and 2.31). The trophic niche overlap was highest (0.52) between Xylocopa grisescens Lepeletier, 1841 and Frieseomelitta silvestrii (Friese, 1902). The low trophic niche overlap between Apis mellifera and native stingless bees seems to be the result of intensive exploration of only a few flower sources by Africanized bees, not frequently visited by meliponids.

Flower-visiting guild associated with the Caatinga flora: trophic interaction networks formed by social bees and social wasps with plants.

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.ZusammenfassungWir verglichen ein soziales BienenPflanzen Netzwerk (BPN) mit einem sozialen Wespen-Pflanzen Netzwerk (WPN) unter der Fragestellung, ob verschiedene Arten von Mutualismus mit demselben Partner zu unterschiedlichen Netzwerkstrukturen führen. Hierzu wurden soziale Bienen und Wespen in einem Sammelgebiet mit Caatinga-Vegetation in Bahia bei ihren Blütenbesuchen gefangen. Jedes zweiteilige Netzwerk wurde dann in Form einer R-Nachbarschaftsmatrize beschrieben. Wir beschrieben jedes Netzwerk in Hinblick auf Schachtelung (nestedness NODF und N), Modularität (M) und Bedeutung einzelner Spezies (Ij). Beide Netzwerke erwiesen sich als geschachtelt (Abb. 1). Wir untersuchten weiterhin, inwieweit die beiden Netzwerkmaße (NODF und N) die Schachtelung in entsprechenden Nullmodellmatrizen (mit n = 1000 Zufallswiederholungen) quantifizierten, wobei Präsenzen zufallsverteilt den jeweils einzelnen Zellen der Matrix zugeordnet wurden. Die aus unseren Daten gebildeten Bienen-Pflanzen- und Wespen-Pflanzen-Matrizen wiesen allesamt eine tiefere Schachtelung auf als die Zufallsmatrizen. Das WPN bildete 116 der 546 möglichen Interaktionen ab und zeigte eine Bindungsstärke von C = 21,24, während das BPN 72 der 456 möglichen Interaktionen aufwies, bei einer Konnektivität von C = 15,79. Sieben der blütenbesuchenden Spezies bildeten den Kernbereich des WPN und sechs Arten erwiesen sich als von besonderer Bedeutung für die Struktur des BPN. Die Topologie des BPN war stark von der Gegenwart von Apis mellifera beeinflusst, einer eingeführten Art, die als Generalist Interaktionen mit 33 der 38 Pflanzenarten einging. Das Gesamtnetzwerk (OFPN) wurde aus 25 blütenbesuchenden Arten und 49 besuchten Pflanzen gebildet und hatte eine Konnektivität von 15,34. Insgesamt konnten wir 188 von 1225 möglichen Interaktionen finden, wobei neun Arten für 78,19 % aller Verbindungen verantwortlich waren: Apis mellifera (33 Interaktionen), Polybia ignobilis (18), P. sericea (17), Polistes canadensis (17), P. paulista (15), Brachygastra lecheguana (13), Trigona spinipes (12), P. occidentalis (11) und Protonectarina sylveirae (11). Ein relativ hoher Anteil der Pflanzenarten (63,3 %, N = 31) wurde sowohl von sozialen Bienen als auch sozialen Wespen besucht. Unsere Analysen der Beziehungsnetzwerke zeigten einen klaren Unterschied hinsichtlich der Bedeutung einzelner Pflanzenarten als Nahrungsquelle für die jeweiligen blütenbesuchenden Gruppen (Abb. 2). Die Modularität des Gesamtnetzwerks aus beiden Gruppen war relativ gering (M = 0,07, P = 0,004), was auf eine Überlappung zwischen Bienen und Wespen in den Blütenbesuchen zurückzuführen ist. Wir fanden zudem eine höhere Nischengruppierung innerhalb der Bienen als innerhalb der Wespen. Trotz der Unterschiede im fakultativen Mutualismus zwischen Bienen-Pflanzen (direkter Mutualismus — Bestäubung) und WespenPflanzen (indirekter Mutualismus — Verteidigung) wiesen die beiden Beziehungsnetzwerke ähnliche Topologien auf, mit geschachtelten Mustern und asymmetrischen, modularen Strukturen.

Compartilhamento de recursos florais por vespas sociais (Hymenoptera: Vespidae) e abelhas (Hymenoptera: Apoidea) em uma área de caatinga

Wasps and bees are important components of flower visitor guilds in the Neotropical region. The abundance of social wasps and bees, collected during flower visits, was used to calculate niche breadth and niche overlap indices, in order to characterize the utilization of the floral resources by those insects. Samples were taken monthly, for 13 months (156h), by two collectors which captured the specimens on flowers using entomological nets, while walking along a way in an area of caatinga at Itatim, State of Bahia, Brazil. Wasps and bees heavily visited a few sources of floral resources, but the most visited plants by each group were different, and few plant species were important for both groups, resulting in low niche overlap between bees and wasps. The niche overlap among wasp species was generally higher than among bee species. The general overlap, which takes into consideration all species together was low (< 30%).

Trap-nesting bees (Hymenoptera, Apoidea) in areas of dry semideciduous forest and caatinga, Bahia, Brazil

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 arrangement of brood cells in the nests, as well as the number of adults produced and the number of generations per year are also presented. Species richness, temporal patterns of nesting, and percentage of parasitism were compared with other habitats.

Nesting biology of Centris (Centris) aenea Lepeletier (Hymenoptera, Apidae, Centridini)

Nesting activity of Centris aenea Lepeletier, 1841 was studied in two Brazilian habitats, Caatinga (Monte Santo, Bahia) and Cerrado (Palmeiras, Bahia and Luiz Antonio, Sao Paulo). Nests were excavated in the ground and did not tend to be aggregated together at the two sites, but at Palmeiras, nests were in a large aggregation. Nest architecture consists of a single unbranched tunnel, sloping to vertical, which leads to a linear series of four cells, placed from 8 to 26 cm in depth. Cells are urn-shaped with a rounded base, and their cell caps have a central hollow process, as in other Centridini. Nest architecture of C. aenea was compared to other species of Centris Fabricius, 1804. Provisions are composed of a pollen mass covered by a thin liquid layer on which the egg is placed. Females were observed gathering oil on Mcvaughia bahiana W.R. Anderson flowers from October to March in the Caatinga, and on Byrsonima intermedia A.Juss. as well as other Malpighiaceae species from August to December in the Cerrado. Pollen is gathered by buzzing flowers of Solanaceae, Caesalpiniaceae, Malpighiaceae, and Ochnaceae. Several nectar sources were recorded. There is indirect evidence that Mesoplia sp. parasitizes nests of C. aenea in the Cerrado.

Estrutura da comunidade de abelhas (Hymenoptera: Apoidea: Apiformis) de uma área na margem do domínio da caatinga (Itatim, BA)

A realizacao de estudos padronizados das comunidades de abelhas tem permitido a abordagem comparativa entre varios ecossistemas e a investigacao da existencia de padroes na estruturacao dessas comunidades na regiao Neotropical. Este estudo foi conduzido ao longo de um ano em Itatim, Nordeste do Brasil, no dominio semi-arido da caatinga. O objetivo do trabalho foi investigar a composicao e as relacoes de abundância entre as especies de abelhas, seus periodos de atividade de voo, e compara-los aos de outras areas estudadas anteriormente. As abelhas foram coletadas a cada 30 dias, entre setembro/1996 e novembro/1997, entre as 6:00h e as 18:00h, totalizando 180h de amostragem. As abelhas foram capturadas com rede entomologica, em flores ou em voo. Foram coletados 1189 individuos, compreendendo 60 especies. Apidae foi a familia mais diversificada, com 37 especies. Os generos com maior numero de especies foram Centris Fabricius, Megachile Latreille e Xylocopa Latreille. Como observado na maioria das areas de caatinga anteriormente estudadas, Apis mellifera L. foi a especie mais abundante, com elevada dominância, compreendendo 51% do numero total de individuos capturados, e ocorreu ao longo do ano inteiro. As outras especies predominantes foram muito menos abundantes, como: Dialictus opacus (Moure) (6,2%), Perditomorpha sp. (4,0%) e Trigona spinipes (Fabricius) (3,8%). Sugere-se que algumas caracteristicas da comunidade devem-se a sua natureza ecotonal, como a ocorrencia provavelmente marginal de algumas especies na caatinga, e a extensao do periodo de atividades de Megachilidae, Halictidae e Colletidae, resultando em um numero relativamente alto de especies em atividade durante os quatro meses mais secos do ano.

Pollen residues in nests of Centris tarsata Smith (Hymenoptera, Apidae, Centridini) in a tropical semiarid area in NE Brazil

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.ZusammenfassungBienen der Gattung Centris sind potentielle Bestäuber von Kulturpflanzen in Brasilien und verschiedene Untersuchungen weisen bereits auf die Bedeutung dieser Bienen als Bestäuber verschiedener Pflanzenfamilien, einschließlich kommerzieller Früchte hin. Wenig ist allerdings darüber bekannt, welche floralen Ressourcen für den Erhalt der Populationen notwendig sind. Anhand der Analyse von Pollenresten im sandigen Substrat der Nistzellen dieser solitären Bienen untersuchten wir die von C. tarsata genutzten Pollen-, Öl- und Nektarquellen in einer Region mit nativer Vegetation in einer Halbtrockenregion im Nordosten Brasiliens, der Caatinga. Pollenkörner wurden quantifiziert, um die Bedeutung der verschiedenen Pflanzenarten für die Bienen abschätzen zu können. Hierzu wurden monatlich Nistfallen eingesammelt, so dass aus den Nestern (n = 13) nach dem Schlupf der Imagines die Pollenreste chemisch herausgelöst werden konnten. Pro Probe wurden sieben Mikrospopiepräparate erstellt. Die quantitative Analyse basierte auf jeweils 1000 Pollenkörnern. Wir identifizierten 31 verschiedene Pollentypen, wobei die von Chamaecrista ramosa, Senna rizzinii, Solanum paniculatum und Byrsonima vacciniifolia die größten Häufigkeiten aufwiesen (Tab. I) und damit vermutlich die wichtigsten Pollenquellen für C. tarsata in dieser Region darstellen. In geringen mittleren Häufigkeiten (<0,01 %) waren 11 Pollentypen vertreten, und 16 Pollentypen wiesen Häufigkeiten von 0,01 % bis 10 % auf, darunter Byrsonima vacciniifolia. Neun Arten der lokalen Flora im Pollenspektrum des Materials aus C. tarsata Nestern stellen vermutlich die Hauptpollenquellen dieser Bienen in der Caatinga dar. Die Mehrzahl der Pollentypen stellte weniger als 1 % des aus den Nestern gewonnen Pollenmaterials dar (Tab. II). Drei Malpighiaceen-Arten und eine Krameriacee konnten wir als Ölquellen von C. tarsata identifizieren. Wir konnten zeigen, dass Pollenanalysen in Nestmaterial interessante Ergebnisse liefern können. Eine Verbindung dieser Methode mit einer Sammelstrategie von Bienen an einzelnen Pflanzenarten sollte es dementsprechend ermöglichen, dass wir unser Wissen über die Nutzung floraler Ressourcen erweitern und daraus angemessene Strategien zum Erhalt und Nutzung von Centris-Arten als Bestäuber entwickeln können.

Fluctuations in Richness and Abundance of Social Wasps During the Dry and Wet Seasons in Three Phyto-Physiognomies at the Tropical Dry Forest of Brazil

ABSTRACT The social wasp nests were quantified in three different plant physiognomies (forested Caatinga, shrubby Caatinga, and agricultural systems) to analyze the effect of environmental seasonality and plant physiognomy on the richness, nest abundance, and species composition of social wasps in the region of tropical dry forest of Brazil. The forested Caatinga physiognomy had the greatest richness of species (S = 16), followed by shrubby Caatinga (S = 13) and by agricultural system (S = 12). The first axis of detrended correspondence analysis (DCA) explained 67.8% of the variability and shows a gradient of the fauna from agricultural system and shrubby Caatinga to forested Caatinga. In the first axis, wet season scores were much higher than those for the dry season in forested Caatinga. The second axis explained 18.7% of the variability and shows a separation of samples collected during the wet or the dry periods in shrubby Caatinga. This separation was less evident in the agricultural system. Variations in nest abundance were more intense in arbustive caatinga (45% decrease in number of active nests in the dry period), moderate in forested Caatinga (24% decrease in number of active nests in the dry period), and low in agricultural systems (8% decrease in the dry period).

Trophic niche breadth and niche overlap in a guild of flower-visiting bees in a Brazilian dry forest

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.