SNFE648 Studies on Neotropical Fauna and Environment 0165-0521/02/3701-001$16.00 2002, Vol. 37, No. •, pp. ••–•• © Swets & Zeitlinger Flower Visits of Centris Bees (Hymenoptera: Apidae) in an Area of Caatinga (Bahia, Brazil) Cândida Maria Lima Aguiar Dept. of Biological Sciences, State University of Feira de Santana, Feira de Santana, State of Bahia, Brazil Abstract Periodic sampling of bees visiting flowering plants resulted The Caatinga is a deciduous forest type, whose principal in the collection of 91 individuals of 10 Centris species in an character is the absence of leaves during much of the year. area of Caatinga (Itatim, Bahia, Brazil). These bees visited The Caatinga comprises several different plant communities, 12 species of plants. Melochia tomentosa (Sterculiaceae), and covers about 800,000km2 in northeastern Brazil a nectar source, was the most frequently visited plant. (Andrade-Lima, 1981). Despite their presumed ecological Chamaecrista, Senna and Solanum species were visited for importance, little is known about the native bee species pollen, and Stigmaphyllon auriculatum for oil. Centris bees present, and their interactions with flowering plants in the were captured from September through April. The data Caatinga. The high percentage of endemic species of bees suggest a seasonal pattern of activity, associated with the found there (32%, including two Centris species), indicates rainy season. that the Caatinga has its own bee fauna (Zanella, 2000a, b). In the Caatinga, Centris bees are the major group of oil- Keywords: Centris, Caatinga, South American dry forests, collectors, for oil-collecting bees of other genera (Epicharis, bee phenology, floral resources, northeastern Brazil. Tetrapedia and Paratetrapedia) are either rare or absent (Vogel & Machado, 1991; Zanella, 2000a). According to Schlindwein (2000), the Centridini are specialized foragers 1 Introduction and key pollinators, helping to maintain plant diversity in tropical ecosystems. As they are essential to the reproductive Centris bees are fundamental components of the large-bee success of several plant species, it is important to identify guild of pollinators, and their importance in dry forests those plants which help to sustain their populations. has been noted by Frankie et al. (1976; 1983). In Brazil, The sampling of bees during floral visits, employing pollination studies in the Cerrado (Gottsberger, 1986), standardized methodology, has been undertaken at a num- on dunes (Gottsberger et al., 1988) and in the Caatinga ber Caatinga sites (Martins, 1994; Aguiar & Martins, 1997; (Vogel & Machado, 1991) have demonstrated that many Viana, 1999; Zanella, 2000a), although data concerning bee plants, such as Angelonia, Byrsonima, as well as some phenology and the floral resources used by each species are species of Chamaecrista, Passiflora, and Turnera, are polli- rare. This work was designed to investigate species richness, nated by Centris bees. In some cases, mainly among oil as well as to identify the plants visited by Centris bees in an flowers, these bees are the only legitimate visitors (Vogel & area of Caatinga in the State of Bahia. Machado, 1991), and these plants depend on the services of Centris bees because of their specialized foraging behavior. Studies on the community of pollinators in the Brazilian Material and methods Caatinga have not yet been undertaken, although, as in other Study site Neotropical habitats with open vegetation, Centris bees would be expected to appear as important pollination agents Sampling was done in the municipal district of Itatim there. (12°42¢S, 39°46¢W), near Mount Agenor (200km from the Received: 17 May 2000 Accepted: 26 August 2002 Correspondence: C.M.L. Aguiar, Depto. de Ciências Biologicas, Universidade Estadual de Feira de Santana, 44031-460 Feira de Santana – BA, Brazil. Fax: +55-75-224 8264; E-mail: [email protected] SNFE648 2 C.M.L. Aguiar city of Salvador) in the State of Bahia, Brazil. The vegeta- although the number of individuals was low in October 1997 tion is predominantly open shrubby Caatinga, common in the (Table 1). The highest number of bees was collected during dry areas of northeastern Brazil. Melochia tomentosa and the rainy season (November to April) while from May to Acacia bahiensis were the most abundant shrubs. Trees are September no Centris bees were recorded. However, there scarce, with Caesalpinia pyramidalis, Spondias tuberosa and was no significant correlation established between the amount Ziziphus joazeiro being the most common species (França et of rainfall and the number of individuals netted per month al., 1997). [correlation analysis: r = 0.38; p > 0.05)], nor the number of The climate is semi-arid, with an average annual tem- species collected (r = 0.29; p > 0.05). perature of 24.3°C and an average annual precipitation of 551mm, although there can be large annual variations (range: 142–1206mm). There are at least five dry months per Discussion year (Bahia, 1994). During the course of this study, the rainy Species spectrum and richness of Centris bees season started in November 1996, and ended in April 1997. The month of December 1996 was uncommonly dry, while The species richness of Centris bees found at Itatim was March and April of 1997 were the rainiest months. The dry relatively high in comparison to other areas of Caatinga, such season extended from May through September of 1997. as São João do Cariri (3 spp., Aguiar & Martins, 1997), Serra Negra do Norte (6 spp., Zanella, 2000a) and Casa Nova (8 spp., Martins, 1994), and was similar to the number of Sampling schedule species encountered in Ibiraba (11 sp., Viana, 1999) and Bees and flowering plants were collected during two Castro Alves (12 spp., Carvalho, pers. comm.). The species consecutive days each month for a fifteen-month period richness of Centris bees in areas of Caatinga is higher than (September 1996 until November 1997). Collecting was per- that observed at Boracéia, in the Atlantic Coastal Rain Forest formed between 12:00 and 06:00 p.m. on the first day and (5 spp., Wilms, pers. comm.), although slightly lower than then between 06:00 and 12:00 a.m. on the second day, for a that found in areas of Brazilian Cerrado (17 spp., Silveira & total of 180 hours of sampling time (12h/mo). Campos, 1995). Bees were captured with entomological nets at all flower- Five species (C. aenea, C. fuscata, C. tarsata, C. ing plants (48 melittophilous species) encountered while trigonoides, and C. xanthomelaena) found in Itatim have walking along a 3km transect. The transect was patrolled been sampled in several other areas of Caatinga (Martins, twice in the morning and twice in the afternoon, always start- 1994; Viana, 1999; Zanella, 2000a). Except for C. xan- ing at different points. Thus, each flowering plant was thomelaena, a species endemic to the Caatinga (Zanella, observed at different times on different days. Approximately 2000b), those species are also common in other habitats as 5min were spent at each plant to capture bees. The time of in the Cerrados (Martins, 1994; Silveira & Campos, 1995) day and the plants being visited were recorded for each and in the Atlantic Coastal Rain Forest (Wilms, pers. comm.; bee collected. Voucher specimens of bees and plants were Teixeira & Machado, 2000). On the other hand, C. caxiensis, deposited in the Herbarium and Entomological Collection of C. leprieuri, C. moerens and C. sponsa are less common the State University of Feira de Santana, at Feira de Santana, species and they have been collected in few areas of Caatinga State of Bahia, Brazil. beyond Itatim. Of these, C. moerens has not been registered in other habitats, while C. leprieuri occurs in the dune veg- etation in Northeastern Brazil (Gottsberger et al., 1988), Results C. caxiensis is present in coastal vegetation (Rêgo & Albuquerque, 1989) and in the Cerrados in the State of 2 Ninety-one individuals belonging to ten Centris species were Maranhão (Brazil) (Albuquerque & Mendonça, 1996) and obtained, 88 of them while visiting flowers. The others were C. sponsa also occurs in the Cerrados (Silveira & Campos, captured in flight. C. aenea and C. fuscata were most fre- 1995). quently captured, while other species were sampled rarely (Table. 1). Centris bees were found visiting 12 of the 48 Floral resources species of flowering plants observed along our transect (Table 2). Melochia tomentosa was the major nectar source, Flowers of Chamaecrista and Senna (Caesalpiniaceae) are being visited by the highest number of individuals from eight important pollen sources for Centris in Itatim and in other species. Caesalpiniacean species and Solanum paniculatum areas (Aguiar, unpublished). Nectar sources are more nu- (Solanaceae) were pollen sources, while Stigmaphyllon merous and are found in several plant genera, including auriculatum (Malpighiaceae) was the only source of floral oil Caesalpinia and Melochia. These were also frequented in among the plants visited by Centris bees. other areas of Caatinga (Vogel & Machado, 1991; Aguiar Centris species were captured from late September until et al., 1995; Lewis & Gibbs, 1999). 3 April. The highest number of bees was sampled between As plants offering floral oils, species of the family October and December (late dry season to early rainy season), Malpighiaceae could be expected to be of special importance SNFE648 Centris bees of the Caatinga 3 for centridine bees; however, we recorded only very few bees on only one species. This may be due to our sampling effort being limited to only one day per month, because other species of Malpighiaceae were not observed flower- ing although Barnebya harleyi, Heteropterys spp., Janusia schwannioides and Thryallis longifolia are known to occur in the vicinity of Mount Agenor (França et al., 1997). Temporal patterns of activity Our data suggest that the activity of Centris bees was related to the rainy season in the Caatinga. At Itatim, the Centris species most frequently captured seemed to have a seasonal activity pattern like bees in other habitats, such as Costa Rican dry forests (Heithaus, 1979; Frankie et al., 1983) and Panamanian forests (Wolda & Roubik, 1986).