Abstract Background: Plants and bees have coevolved throughout geological time, establishing a mutualistic relationship that results in feeding/resource obtention by bees and the reproductive success of angiosperms. Questions and Hypotheses: What is the floristic composition of the vegetation visited by bees in the Caatinga? How are pollen grains from Caatinga bee plant species characterized? Do pollen grains of bee plant species present characters that could be associated with the pollination process? Studied species: We studied the pollen grains of 45 bee plant species belonging to 41 genera and 23 angiosperm families. Among the studied species, 37 % are endemic to Brazil, and eight species are endemic to the Caatinga biome. Study site and dates: Apiary within the Caatinga biome, in the State of Bahia, Brazil. Climate warm semiarid. Fieldwork was carried out between August 2016 and June 2017. Methods: Plants in bloom and being visited by Apis mellifera were collected during biweekly field expeditions, herborized, identified, and deposited at the HUNEB herbarium. Pollen grains were acetolyzed, characterized, and microphotographed under light microscopy. Results: Forty-five bee plants were collected and classified according to field observations and specialized literature. Pollen morphology was variable, and nine species had their pollen morphology described for the first time. The apertures of the studied pollen grains were mainly tricolporate (44 %), pantoporate (15 %), and inaperturate (13 %), and exine ornamentation was mainly (micro)reticulate (46 %) and (micro)echinate (33 %). Conclusions: Our results suggest that bee plants present a set of palynological characters that may favor entomophily.

Resumen: Antecedentes: Plantas y abejas coevolucionaron, resultando en la alimentación/obtención de recursos por parte de las abejas y el éxito reproductivo de las angiospermas. Preguntas: ¿Cuál es la composición florística de la flora apícola en la Caatinga? ¿Cómo se caracterizan los granos de polen de las especies apícolas? ¿Los granos de polen de la flora apícola presentan características que facilitan la polinización? Especies de estudio: Se estudiaron los granos de polen de 45 especies apícolas vegetales pertenecientes a 41 géneros y 23 familias de fanerógamas. Entre las especies colectadas, el 37 % son endémicas de Brasil, con ocho especies exclusivas de la Caatinga. Sitio y años de estudio: Apiario en la Caatinga, Bahía, Brasil. Clima cálido semiárido. Colectas realizadas entre agosto de 2016 y junio de 2017. Métodos: Fueron colectadas las especies botánicas en floración que estaban siendo visitadas por las abejas Apis mellifera, posteriormente herborizadas, identificadas y adicionadas en la colección HUNEB. Los granos de polen fueron sometidos a acetólisis, caracterizados y fotomicrografados bajo microscopía óptica. Resultados: Se colectaron y clasificaron 45 plantas apícolas de acuerdo con observaciones de campo y literatura especializada. La morfología del polen fue bastante variada, con predominio del tipo tricolporado (44 %), pantoporado (15 %), inaperturado (13 %) y variación de la escultura exina, con predominio de polen (micro)reticulado (46 %) y (micro)equinado (33 %). Nueve especies fueron descritas palinológicamente por primera vez. Conclusiones: Nuestros resultados sugieren que existen características en la morfología de los granos de polen de las plantas apícolas que favorecen la polinización.

ABSTRACT Papilionoideae is the most diverse subfamily of Leguminosae, representing approximately 39 % of its species. Although it is particularly species rich and diverse in the Caatinga, the main phytophysiognomy of the semiarid Northeast Region of Brazil, little is known about the pollen morphology of the species that occur there. This study analyzes and describes the pollen morphology of the 27 species of Papilionoideae endemic to the Caatinga. Pollen grains were acetolyzed, mounted on permanent slides, measured, described and photomicrographed using light and scanning electron microscopy (LM and SEM, respectively). The main variable morphological features were pollen grain size, shape, amb, apertural type and exine ornamentation under LM (microreticulate, reticulate, psilate or finely scabrate) and SEM (microreticulate, reticulate, rugulate, granulate, fossulate and perforate). High intergeneric morphological heterogeneity was observed while morphological variation within each genus was subtle. Nonetheless, size, endoaperture shape, fastigium presence/absence and exine ornamentation were found to be important characteristics for the identification of some species.

RESUMO O presente estudo teve por objetivo determinar o potencial apícola de Croton heliotropiifolius Kunth, baseado na sua estratégia de floração, características florais, recursos florais ofertados, frequência e atividade de forrageamento de indivíduos de Apis mellifera L. às flores na Fazenda Ingazeira, Brasil. C heliotropiifolius possui flores díclinas e inconspícuas agrupadas em densas inflorescências terminais, em que cada indivíduo produz 560 ± 60 inflorescências, com 59 ± 12 flores pistiladas e 160 ± 26 flores estaminadas, tendo cada flor estaminada a capacidade de produzir aproximadamente 6 × 10 3 grãos de pólen. Embora ambas as flores produzam néctar ( 2 , 8 ± 0 , 8 e 0 , 3 ± 0 , 06 μL , nas flores pistiladas e estaminadas, respectivamente), os espécimes de A. mellifera concentraram suas visitas nas flores estaminadas (98%), com pico das visitações registrados entre 08:00-11:00 h. Foi estimado que nas atividades de forrageamentos, essa abelhas removem em média 405 grãos de pólen por visita em cada flor, desta forma, como um indivíduo da espécie estudada pode produzir aproximadamente 5 , 376 × 10 8 grãos de pólen, tal quantidade é suficiente para suportar até 33 ciclos de visitações de uma colônia de A. mellifera. Além disso, C. heliotropiifolius apresentou um padrão de floração anual, com altas produções de flores por cinco meses, manifestando estratégia de floração cornucópia, representando uma característica importante por favorecer na maior disponibilização de recursos florais nos ambientes. Portanto, esses dados demostram o grande potencial de C. heliotropiifolius para a apicultura na região.

ABSTRACT The aim of the present study was to determine the beekeeping potential of Croton heliotropiifolius Kunth (Euphorbiaceae) based on flowering strategy, floral characteristics, available floral resources, and the individuals frequencies and foraging activities of Apis mellifera L. on its flowers in Fazenda Ingazeira, Brazil. Each C. heliotropiifolius plant possessed inconspicuous diclinous flowers clustered into 560 ± 60 dense terminal inflorescences containing 59 ± 12 pistillate and 160 ± 26 staminate flowers. Although both types of flowers produced nectar (pistillate: 2.8 ± 0.8 μL ; staminate: 0.3 ± 0.06 μL ), A. mellifera workers mostly visited staminate flowers (98%) during the peak visitation period (08:00-11:00 h). Moreover, during the foraging period, each plant produced approximately 5.376 × 10 8 pollen grains, ensuring approximately 33 visitation cycles from a colony of A mellifera workers that picked up an average of 405 pollen grains per visit per flower. Further, C. heliotropiifolius showed an annual cornucopia flowering strategy with high flower production for five months, which is an important characteristic that ensures floral resource availability in the environment. These findings suggest that C. heliotropiifolius has a great potential for apiculture in this region.

ABSTRACT Bernardia and Tragia are the largest genera of the tribes Bernardieae and Plukenetieae (Euphorbiaceae,), with 68 and 125 species, respectively. Very few palynological studies have focused specifically on these genera in spite of the great pollen diversity observed in the family. The present study analyzed the pollen morphology of the Brazilian species of Bernardia and Tragia to identify diagnostic characteristics that could aid in their taxonomic circumscription. The pollen grains of 11 species of Bernardia and five of Tragia were obtained from specimens deposited in the HRB, HUEFS, PEUFR, RB and UFP herbaria, and were analyzed using light and scanning electron microscopy. The analyzed species had small- to medium-sized pollen grains in monads, with shapes from prolate to subprolate. The most significant differences were observed in aperture type and exine ornamentation. The pollen grains of Bernardia are tricolporate, with aperture margins varying from narrow to wide or with just slightly evident margins, and the exine varying between microreticulate and microreticulate-perforate. The pollens of Tragia are tricolpate with the exine varying between intectate pilate and verrucate. Some species of both genera could be diagnosed based on unique pollen characters, and four distinct morphological groups of Bernardia and two of Tragia were observed.

ABSTRACT 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. The 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. The 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). These results confirm a high degree of pollen dimorphism in Waltheria associated with heterostyly.

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 paniculatumpollen 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.

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.

O estudo palinológico de Mimosa L. teve por finalidade caracterizar as espécies do gênero ocorrentes na vegetação de caatinga do Nordeste brasileiro. Foram examinadas 39 espécies que tiveram seus grãos de pólen acetolisados, medidos, descritos e ilustrados sob microscopia óptica e eletrônica de varredura. Os resultados permitiram reconhecer seis tipos polínicos e dois subtipos com base na unidade de dispersão. Foi registrada a ocorrência de díades (M. adenophylla Taub., M. ursina Mart.) e mônades (M. ursina Mart.). A morfologia polínica das espécies (Mimosa lepidophora Rizzini e Mimosa pithecolobioides Benth.) Mimosa-Mimadenia mostrou similaridade com grupo Piptadenia enquanto a diversidade polínica observada em Mimosa-Batocaulon indicou o polimorfismo do grupo.

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.