A new treatment protocol was developed to analyze pollen residues found in nests of Centris tarsata Smith harvested from nest-traps. The study area was located in the Canudos Biological Station in the municipality of Canudos (09 masculine56'34'S; 38 masculine59'17'W), in the northeastern micro-region of Bahia State, Brazil. The local vegetation is an open caatinga (deciduous dryland vegetation), the regional climate is semi-arid, the average annual temperature is 24.1 masculineC, and the annual regional rainfall rate is 454 mm. Ten nests of C. tarsata were collected in trap-nests during the first semester of 2004. Pollen analysis from the nests required the development of a new methodology that combined techniques of palynological sediment analysis with the more common pollinic analysis by acetolysis. Microscopic analyses employed optical microscopy techniques. The pollinic spectrum of the samples from C. tarsata indicated the presence of 17 pollen types from seven plant families, which were present in assemblage of five to eleven pollen types, pointed to the plants used by bees to feed on their offspring. The most represented plant families were Leguminosae (49.3%) and Solanaceae (43.2%). The most frequent pollen types in the samples were from Solanum paniculatum (43.8%) and Senna rizzini (32.1%). The protocol developed provides a new tool for diet assessment of Centris and other groups of solitary bees.

RESUMO -(Palinologia de espécies de Palavras-chave: morfologia polínica, Mimosa, díades, LeguminosaeABSTRACT -(Pollen morphology of Mimosa L. species (Leguminosae -Mimosoideae) from the semi-arid region of Brazil). Pollen studies of Mimosa L. sought to characterize the species of this genus occurring within the caatinga vegetation of northeastern Brazil. A total of 39 species were examined. The pollen grains were acetolyzed, measured, described, and illustrated using optical light microscopy and scanning electron microscopy. The results indicated the existence of six basic pollen types and two sub-types, based on dispersal units. The occurrence of dyads (Mimosa adenophylla Taub., Mimosa ursina Mart.) and monads (Mimosa ursina Mart.) was recorded.

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Information is presented concerning pollen stored in nests of Centris analis, a native Brazilian bee species important as a potential pollinator of tropical fruit trees. Sampling was performed in an area of hyperxerophytic caatinga shrub vegetation in the "Estação Biológica de Canudos" (Canudos Biological Station-EBC), Bahia State, Brazil. The pollen spectrum present in the nests of C. analis was determined by examining the pollen residues found on the walls of the larval cells and in feces incorporated into the construction of the nests. The pollen spectrum in the studied nests (n=5) of C. analis was composed of a total of six pollen types, of which Byrsonima vacciniifolia (45.98%) and Chamaecrista ramosa (44.73%) demonstrated the highest occurrence frequencies. The pollen types C. ramosa, Banisteriopsis muricata and Byrsonima vacciniifolia also appear to be important resources for C. analis in the caatinga vegetation at the EBC. The presence of the pollen type Rhaphiodon echinus probably indicates a nectar source used by C. analis during specific periods. C. analis utilized only a fraction of the resources available in the EBC, and the plants reported here are new registers of food sources for C. analis in the Brazilian semiarid region.

Pollen sources used by Centris trigonoides bees were identifıed in an area of the Caatinga vegetation by analysing the pollen residues encountered in their nests. Twenty-eight pollen types were identifıed, and the most frequently found were Chamaecrista ramosa (46.45%; Leguminosae-Caesalpinioideae), Solanum paniculatum (16.65%; Solanaceae) and Zornia echinocarpa (10.27%; Leguminosae-Papilionoideae). The identifıcation 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 Centris trigonoides.

Species of Bromeliaceae have leaves in a spiral configuration. Because of the shape of the rosette thus formed and the imbricate configuration of the leaf sheaths, there is usually a tank in which rainwater and other components of the environment, including pollen grains, accumulate, making such tanks effective pollen rain collectors. The objective of this study was to use bromeliads as a tool to increase knowledge about the vegetation of the caatinga (shrublands) in the Canudos region of the state of Bahia, located in the semi-arid zone of Brazil, as well as to analyze the dynamics of pollen dispersal and deposition. To that end, we collected samples of the water from the tanks of bromeliads at the Canudos Biological Station. A total of 149 pollen types were detected, 88 of which could be identified botanically. The families that were the most well-represented among the pollen types were Fabaceae (with 25), Asteraceae (with 9), and Euphorbiaceae (with 7). Ten pollen types were presented as potential indicators of caatinga vegetation. We conclude that tank bromeliads are useful for gathering information about pollen rain and pollen dynamics, as well as about the transport and deposition of pollen in the caatinga.

The aim of this study was to identify, by sediment pollen analysis, the plant species used as floral resources for the provisioning of brood cells in Centris (Hemisiella) tarsata, in an area of Caatinga, within the municipality of Nova Soure, Bahia State, Brazil. The analysis of pollen contents from three brood cells revealed 11 pollen types, corresponding to four botanical families. Malpighiaceae was represented most, followed by Leguminosae, Ochnaceae, and Solanaceae, the latter two represented by just a single pollen type each. On the basis of the percentages in the samples, it was possible to infer that C. tarsata visited distinct plants, but intensified its pollen collection in species related to Aeschynomene martii and Solanum paniculatum pollen types, which are considered the most important pollen sources in the larval diet of this bee. In addition to the pollen sources, we have also recorded seven pollen types regarded as oil ones, all related to the Malpighiaceae family. The information about the resources for C. tarsata can be of great relevance, in view of the importance of these bees in the pollination of native flora.

Waltheria encompasses about 60 species distributed in Brazil and Mexico. To improve the palynology of the genus, we analyzed 14 species occurring in the Brazilian State of Bahia. Pollen grains were acetolyzed and examined using light microscopy and scanning electron microscopy. Non-acetolyzed pollen grains were viewed by transmission electron microscopy. Th e results revealed two general pollen types based on exine ornamentation, such as reticulate and echinate, which are distinct with regard to (1) size and shape, (2) apertural type and number, (3) relative length of ectoapertures, and (4) thickening of the nexine compared to the sexine. An ultrastructural analysis of the pollen wall revealed a continuous foot layer and a compact and discontinuous endexine in most cases. Th e sexine consisted of heterogeneous columellae, which support a perforated semitectum (echinate type) or the semitectum was composed of perforations and muri-shaped thickening (reticulate type). Th ese results confi rm a high degree of pollen dimorphism in Waltheria associated with heterostyly.