DOI: 10.13102/sociobiology.v66i1.3434Sociobiology 66(1): 88-96 (March, 2019) Open access journal: http://periodicos.uefs.br/ojs/index.php/sociobiology ISSN: 0361-6525 Pollen Analysis of the Post-Emergence Residue of Euglossa Bees (Apidae: Euglossini) Nesting in an Urban Fragment Introduction The Euglossini tribe (Hymenoptera: Apidae) is distributed only in the Neotropical region and it is divided into five genera: Euglossa Latreille, Eulaema Lepeletier, and Eufriesea Cockerell consist of pollen-gathering species, whereas Aglae Lepeletier and Serville as well as Exaerete Hoffmannsegg are cleptoparasites (Michener, 2007). The Euglossa genus has the largest number of species, with 129 species already described (Nemésio & Rasmussen, 2011), which are distributed from Mexico to northern Argentina and in the Caribbean Islands (Cameron, 2004; Michener, 2007). In the Corbiculate Apidae, Euglossini bees are the only species that are not, strictly speaking, social. Certain Euglossa species are solitary or can form community nests with various females born in the nest (Garófalo et al., 1998; Michener, 2007; Augusto & Garófalo, 2011). Initially, when a Euglossa Abstract Euglossini bees are considered pollinators of a wide variety of plants in the Neotropical region, but little is known about their floral preferences. In this study, we identified the botanical species used as pollen and nectar sources by three Euglossa species, Euglossa cordata (Linnaeus), E. townsendi Cockerell, and E. securigera Dressler using pollen residue found in brood cells from trap nests installed in an urban fragment in São Luís, Maranhão, Brazil. In 14 analyzed E. cordata nests, 23 pollen types were observed, in seven E. townsendi nests, ten pollen types were observed, and in one nest of E. securigera, six morphotypes were identified. Solanum (Solanaceae), Zanthoxylum (Rutaceae), Mimosa pudica L. (Fabaceae), and Chamaecrista (Fabaceae) pollen types were common to all three bee species. A principal component analysis showed 83.04% variability on the first two axes, demonstrating substantial similarity among the samples. Solanum, Mimosa pudica, and Zanthoxylum were the principal components in the ranking. Larger diversity values (mean = 0.80) in some samples indicated that the species gathered resources in a heterogeneous manner; this is consistent with the findings of other studies of Euglossa. In general, the bees exhibited overlapping niches with regard to the most abundant pollen grains in the nests, but the females showed individual plasticity when gathering floral resources. Sociobiology An international journal on social insects RS Pinto, AG Silva, MMC Rêgo, PMC Albuquerque Article History Edited by Denise Alves, ESALQ-USP, Brazil Received 06 May 2018 Initial acceptance 22 June 2018 Final acceptance 12 September 2018 Publication date 25 April 2019 Keywords Floral preferences, nectar, trap nests, orchid bees. Corresponding author Patrícia Maia Correia de Albuquerque Universidade Federal do Maranhão Departamento de Biologia Laboratório de Estudos Sobre Abelhas Av. dos Portugueses nº 1966 CEP: 65080-805, São Luís-MA, Brasil. E-Mail: patemaia@gmail.com female finds an appropriate place to build her nest, she forms the first cell made with resin, where she stores the larval food. Next, she lays her egg and closes the cell, then begins to build new brood cells (Garófalo et al., 1998; Ramírez et al., 2002). Nests of Euglossa can be aerial or constructed in different types of cavities found in natural substrates; additionally, they can also be hosted by artificial man-made structures (Augusto & Garófalo, 2004; Cameron, 2004). The use of trap nests has enabled researchers to become acquainted with the different species of bees nesting in such cavities in different localities, as well as providing information on species biology (Garófalo et al., 1993). This includes the food resources utilized by adult bees and larvae (Arriaga & Hernández, 1998; Silva et al., 2016). Euglossini bees are pollinators of a wide variety of plants and can fly long distances in tropical forests (Janzen, 1971). To date, the resources that these bees use for food are not well known; most previous studies are based on Universidade Federal do Maranhão, São Luís, Maranhão, Brazil RESEARCH ARTICLE - BEES Sociobiology 66(1): 88-96 (March, 2019) 89 direct observations of flowers (Ramírez, 2002; Rocha-Filho et al., 2012). Some studies have identified the floral resources through pollen analysis of larval food; e.g. Euglossa atroveneta Dressler (Arriaga & Hernández, 1998), E. annectans Dressler (Cortopassi-Laurino et al., 2009), E. viridissima Friese, E. dilemma Bembé & Eltz (Villanueva-Gutierrez et al., 2013), E. nigropilosa Moure (Otero et al., 2014), and E. townsendi Cockerell (Silva et al., 2016). In spite of this, there is a need for more research into the different biomes in which these bees are found. Euglossa cordata (Linnaeus), E. securigera Dressler, 1982, and E. townsendi are widely distributed in the Neotropics. In Brazil, they occur in the humid Amazon forest and in vast areas in the northeast and the central-south (Rêbelo et al., 2003). In the state of Maranhão, these species are widely distributed throughout the various phytogeographic regions (Rebêlo & Silva, 1999). Maranhão is undergoing rapid deforestation, and is located in a region of transition between the Amazon forest, the Cerrado of the Central Plains, and the semi-arid Caatinga in the northeast (Rêbelo & Silva, 1999). Therefore, it is necessary to conduct further research to understand the biodiversity and ecological relationships of these flora and fauna. To this end, the aim of the present study was to determine the floral resources utilized by E. cordata, E. townsendi, and E.securigera via the analysis of post-emergence pollen residue collected from trap nests in an urban fragment. Material and Methods Study area The study was conducted at the 120.95-ha Integral Protection Conservation Unit in the Sítio do Rangedor State Park, located in the municipality of São Luís, Maranhão, Brazil (decree no. 23303/2007). The park serves as a climate control and water capture unit for the municipality (SEMA, 2017). The vegetation in Rangedor State Park is a remnant fragment of the Amazon Forest. Estimates indicate that there are more than 120 botanical species in the region, distributed in 52 plant families, with Syagrus oleracea (Mart.) Becc. (Arecaceae), Attalea speciosa Mart ex. Spreng. (Arecaceae), Pithecellobium sp. (Fabaceae), and Himatanthus drasticus (Mart.) Plumel (Apocynaceae) constituting approximately 45% of the tree population (SEMA, 2017). The city of São Luís is located on the northern coast of Maranhão. It has a humid tropical climate, with average temperatures ranging from 26 to 28 ºC. Annual rainfall reaches 2000 mm3, with the period of most intense rainfall from January to June, and the dry season from July to December (Silva et al., 2008). Nest sampling Trap nests were installed in the study area for one year (April 2010 to April 2011). The nest diameters were 8, 10, 12, 14, and 16 mm. They consisted of two pieces of wood joined together with adhesive tape (3 cm high x 3 cm wide x 16 cm long), with a 10 cm deep longitudinal slit. In all, 500 nests were used, with 100 of each diameter. They were organized into 100 clusters protected by PET bottles, with one nest of each diameter in the cluster. The blocks were placed in two sampling units, selected according to the physiognomic characteristics of the vegetation. Area I (2°9’54”S, 44°15’51”W) was selected for its open vegetation, mainly composed by shrubs and herbaceous plants, and greater exposure to the sun. Area II (2°29’48”S, 44°16’07”W) was chosen for its naturally regenerating vegetation and shaded environment; this area corresponds to dry land forest, which represents 50% of the plant cover of the park (SEMA, 2017). In each area, we installed 50 blocks on the branches of trees, hanging at a height of 1.5 m from the ground. Every two weeks, the trap nests were inspected. Those in which bees had established were taken to the laboratory until the individuals emerged. They were then sacrificed in chambers with ethyl acetate, pinned, and labeled. The Euglossa genus, identified by a specialist, was common in the trap nests in both Area I and Area II. The species were found to belong to the subgenus Euglossa (Euglossa) and to be highly similar morphologically. Identification was made possible through the males that were born in the nests, since they were the only ones with identification keys. Pollen samples Each nest occupied by bees was considered a sample (E. cordata: Ec.01–Ec.14, E. townsendi: Et. 01–Et.07, and E. securigera: Es.01). After all the individuals had emerged, the residual pollen grains and feces found in the brood cells were obtained so that the floral resources utilized by the bees. The pollen material was prepared using the acetolysis method described by Erdtman (1960). Under the optical microscope, pollen types were identified and 500 pollen grains were counted per sample. In this manner, we were able to determine the frequency of pollen type occurrence. When possible, we identified pollen grains at the species level, and we also used the pollen type criterion for genus or family, in which pollen grains that present a set of very similar morphological characteristics comprise a group of plants that share the same characteristics (Barth, 1989). Pollen slides from the Palynotheca of the Federal University of Maranhão and pollen catalogues were used to identify the botanical affinity of the pollen types (e.g. Roubik & Moreno, 1991; Silva et al., 2014; Lorente et al., 2017). Data analysis To verify the similarity of pollen types among samples, multivariate analysis was conducted using principal components analysis (PCA). First, a matrix with the absolute values for each pollen type present in the samples was transformed into natural logarithms. Next, ranking was conducted using a covariance matrix and employing the PAST program. Variability among samples was expressed using the first two axes of the PCA. RS Pinto, AG Silva, MMC Rêgo, PMC Albuquerque – Pollen analysis of the post-emergence residue of Euglossa90 The amplitude of the trophic niche, assessed by the species richness (S), the Shannon diversity index (H’), and the equitability index (J’), were calculated for all samples. These indexes were utilized to determine the diversity and degree of uniformity of pollen types found in the bee nests (Odum, 1988). Results Three species of Euglossini nested in trap nests in the Sítio do Rangedor State Park. Fourteen nests were occupied by E. cordata, which nested in cavities with three diameters (12 mm: three nests, 14 mm: five nests, 16 mm: six nests). In total, eight of these nests were in Area II, while six were in Area I. E. townsendi occupied nests of four different diameters (10 mm: one nest, 12 mm: two nests, 14 mm: three nests, 16 mm: one nest) and only in Area II. The only nest of E. securigera was found in a 16mm cavity in Area I. During the study period, nesting occurred in all months except from October to December 2010 (Tables 1 and 2). Twenty-eight pollen types were found in the 22 analyzed nests, belonging to 14 botanical families and 24 genera; only three pollen types were not identified. The botanical family with the largest number of types was Fabaceae (10), followed by Arecaceae and Myrtaceae (2 each); all others included only one pollen type. Euglossa cordata Samples Ec.01 Ec.02 Ec.03 Ec.04 Ec.05 Ec.06 Ec.07 Ec.08 Ec.09 Ec.10 Ec.11 Ec.12 Ec.13 Ec.14 Mean Date May/10 Jun/10 Jun/10 Jul/10 Jul/10 Jul/10 Jul/10 Jul/10 Aug/10 Aug/10 Sep/10 Jan/11 Apr/11 Apr/11 Diam. (mm)/Site 14 / I 16 / II 12 / II 12 / II 14 / II 16 / I 12 / II 14 / II 16 /I 16 / II 14 / I 14 / I 16 / I 16 / II Number of cells 4 7 4 3 3 4 4 5 3 5 5 6 6 9 Pollen types Frequencies of pollen types (%) Arecaceae Copernicia prunifera 0.4 0.2 0.04 Mauritia 0.6 0.04 Asteraceae Wedeliapilosa 0.4 0.2 0.04 Bignoniaceae Bignonia 0.6 0.8 4.4 1.4 0.51 Euphorbiaceae Dalechampia 0.8 0.6 1.2 10.4 1.2 3.8 1.29 Fabaceae Chamaecrista 0.2 0.4 28.2 7.6 7.8 2.2 1.4 3.41 Cassia 9.0 0.64 Centrosema brasilianum 6.4 0.46 Copaifera 0.2 0.01 Delonix 0.4 0.2 25.8 1.89 Dioclea 0.4 0.03 Mimosa pudica 41.4 13.4 0.8 28.6 68.4 60.8 3.8 37.8 33.4 4.4 20.91 Mimosa type 2 0.8 0.06 Schrankia leptocarpa 0.6 1.0 0.4 0.14 Swartzia 0.4 0.03 Myrtaceae Eugenia 50.2 3.59 Myrcia fallax 2.4 0.17 Rubiaceae Manettia 0.4 0.03 Rutaceae Zanthoxylum 11.4 15.0 34.8 8.8 38.4 31.2 11.4 18.4 7.0 12.2 7.6 23.4 15.69 Solanaceae Solanum 88.0 43.4 1.0 89.6 2.6 0.4 26.4 97.8 64.4 41.6 65.6 63.4 57.6 67.0 50.63 Verbenaceae Lantana 2.2 1.8 0.29 Not identified NI1 0.2 0.01 NI2 1.2 0.09 Table 1. Frequency of occurrence of pollen types in Euglossa cordata nests. Sociobiology 66(1): 88-96 (March, 2019) 91 Twenty-three pollen types occurred in the nests of E. cordata, belonging to 10 families and 20 genera; two were not identified (Table 1). For E. townsendi, 10 pollen types were identified, distributed among seven families and nine genera; one was not identified. E. securigera, with just one nest evaluated, exhibited six pollen types belonging to five families and six genera (Table 2). The most frequent types of pollen grains for E. cordata were Solanum (50.63%) (Fig 1A), Mimosa pudica L. (20.91%) (Fig 1B), Zanthoxylum (15.69%) (Fig 1C), Eugenia (3.59%) (Fig 1D), Chamaecrista (3.41%), Delonix (1.89%), and Dalechampia (1.29%) (Fig 1E); the remaining 16 pollen types constituted less than 1% of grains counted (Table 1). For E. townsendi, Solanum (55.06%), Mimosa pudica (31.49%), Zanthoxylum (11.97%), and Copernicia prunifera (Mill.) H.E. Moore (1.06%) were the most frequent pollen types; the remaining six pollen types represented less than 1%. For E. securigera, the most important pollen types were Solanum (56%), Zanthoxylum (23.80%), Byrsonima (11.40%), Mimosa pudica (4.40%), and Micinia (3.80%) (Table 2). The pollen grains in common for all three bee species were Chamaecrista, M. pudica, Zanthoxylum, and Solanum. Sixteen pollen types were exclusive to E. cordata, three to E. townsendi, and only one to E. securigera (Table 3). Euglossa townsendi E. securigera Samples Et.01 Et.02 Et.03 Et.04 Et.05 Et.06 Et.07 Mean Es.01 Date Jun/10 Jul/10 Aug/10 Mar/11 Mar/11 Apr/11 Apr/11 Feb/11 Diam. (mm) / Site 14 / II 14 / II 16 / II 14 / II 10 / II 12 / II 12 / II 16 / I Number of cells 4 8 6 8 9 9 9 3 Pollen types Frequency of pollen types (%) Arecaceae Copernicia prunifera 7.4 1.06 Fabaceae Chamaecrista 1.0 0.14 0.60 Mimosa pudica 56.4 30.8 1.8 89.0 2.2 40.2 31.49 4.40 Schrankia leptocarpa 0.8 Malpighiaceae Byrsonima 0.4 0.06 11.40 Malvaceae Hibiscus 0.2 0.03 Melastomataceae Micinia 3.80 Rutaceae Zanthoxylum 38.6 4.0 13.4 3.2 13.2 5.6 5.8 11.97 23.80 Sapindaceae Cupania diphylla 0.4 0.06 Solanaceae Solanum 4.2 65.2 84.8 83.4 54.2 93.6 55.06 56.00 Not identified NI3 0.2 0.03 Table 2. Frequency of occurrence of pollen types in Euglossa townsendi and E. securigera nests. Table 3. Exclusive pollen types (*) shared (+) by Euglossa cordata, E. townsendi and E. securigera nesting in trap nests in the Sítio do Rangedor State Park, Maranhão, Brazil. E. cordata E. townsendi E. securigera E. cordata * Mauritia. Wedelia pilosa. Bignonia. Dalechampia. Cassia. Centrosema brasilianum. Copaifera. Delonix. Dioclea. Mimosa tipo 2. Eugenia. Myrcia fallax. Manettia. Lantana. Not identified (NI 1. NI 2) + Copernicia prunifera. Chamaecrista. Mimosa pudica. Schankia leptocarpa. Zanthoxylum. Solanum + Chamaecrista. Mimosa pudica. Zanthoxylum. Solanum E. townsendi * Hibiscus. Cupania diphylla. Not identified (NI 3) + Chamaecrista. Mimosa pudica. Byrsonima. Zanthoxylum. Solanum E. securigera * Micinia RS Pinto, AG Silva, MMC Rêgo, PMC Albuquerque – Pollen analysis of the post-emergence residue of Euglossa92 Fig 1. Photomicrographs of certain pollen types observed in the nests of Euglossa females. (A) Solanum, (B) Mimosa pudica, (C) Zanthoxylum, (D) Eugenia, (E) Dalechampia and (F) Centrosema brasilianum (scale bars = 10 μm). The pollen type samples were ordered using PCA according to the similarity of their occurrence. Figure 2 shows that the variability covered 83.04% on the first two PCA axes, which demonstrates high similarity among the samples. Solanum, M. pudica, and Zanthoxylum were the principal components used for ranking the samples. The aggregate of types, on the left side of the PCA, indicates species with few grains or those encountered in just a few samples. The Ec.10 sample had the highest richness of pollen types (10). In contrast, samples Ec.01, Et.02, Ec.06, Et.03, and Et.06 had the lowest number of pollen types (3 each). On average, there were 4.95 types per nest [standard deviation (SD): ± 1.78]. Fig 2. Ranking of principal components analysis (PCA) for nests of Euglossa cordata (Ec.01 to Ec.14), Euglossa townsendi (Et.01 to Et.07) and Euglossa securigera (Es.01). (● = pollen type). Sociobiology 66(1): 88-96 (March, 2019) 93 As for the Shannon diversity index, sample Ec.10 presented the highest value (H’ = 1.371) and Ec.08 had the lowest (H’= 0.135) (0.80 ± 0.34) (Fig 3). The mean equitability index was 0.52 (± 0.18); sample Et.06 had the highest value (J’ = 0.782) and Ec.08 had the lowest value (J’ = 0.084) (Fig 3). Discussion The predominance of nests obtained from E. cordata was due to the fact that the species is one of the most frequent species in the ecosystems of the northern region of the State of Maranhão (Rêbelo et al., 2003) and in several other regions, while E. townsendi and E. securigera are less frequent in surveys (e.g. Neves & Viana, 1997; Mendes et al., 2008; Ramalho et al., 2009). In spite of the difference in the number of nests obtained, the floral resources identified in this analysis contribute to the knowledge of the plants used by the bee species studied, particularly for E. securigera, as the food resource usage of which has not been previously assessed. The Euglossa species are considered generalists when foraging for food resources. Nevertheless, they show preferences for certain plant families. Overall, regardless of the area of the park in which they nested, E. cordata, E. townsendi, and E. securigera exhibited important source sharing. This result was similar to those of a previous study on E. viridissima and E. dilemma, which demonstrated overlapping niches (Villanueva-Gutierrez et al., 2013). In this study, 23, 10, and 6 pollen types were observed in the nests of E. cordata, E. townsendi, and E. securigera, respectively, which was similar to that observed by Boff and Alves-dos-Santos (2018) in nests of E. cordata (20 pollen types), but less than that observed in nests of E. atroveneta (74) (Arriaga & Hernández, 1998), E. annectans (74) (Cortopassi- Laurino et al., 2009), E. viridissima, and E. dilemma (45) (Villanueva-Gutierrez et al., 2013). However, a smaller number of nests was assessed in the Sítio do Rangedor State Park, especially for E. securigera¸ for which only a single nest was obtained for the analysis. Furthermore, the pollen analyzed in our study was the residue present in the brood cells. Even so, the floral preferences were quite similar to those found inprevious studies. Even for E. townsendi, which had 10 pollen types identified in seven nests, we observed the lowest degree of exploited species richness compared to a previous study of the same bee species (Silva et al., 2016), in which 21 pollen types were found in six nests. Because the Sítio do Rangedor State Park consists of a forest fragment with reduced plant diversity (SEMA, 2017), the number of botanical species exploited by E. townsendi in the locality may have been limited. However, both studies showed that this bee species has botanical preferences and, in the state of São Paulo, the greatest preference was for Miconia chamissois Naudin (Melastomataceae), followed to a lesser extent by Solanum palinacanthum Dunal (Solanaceae) (Silva et al., 2016). Plant species of Solanaceae (Solanum), Fabaceae (Chamaecrista and Cassia), and Melastomaceae (Micinia) have flowers with poricidal anthers; in order to obtain pollen from these flowers, bees must powerfully vibrate their wings Fig 3. Richness (S), Diversity Index (H’) and Equitability (J’) of pollen grains found in Euglossa cordata (Ec.01 – Ec.14) and Euglossa townsendi (Et.01 to Et.07) nests. RS Pinto, AG Silva, MMC Rêgo, PMC Albuquerque – Pollen analysis of the post-emergence residue of Euglossa94 in a behavior known as “buzz pollination” (Buchmann, 1985; Nunes-Silva et al., 2010). Furthermore, other polleniferous species without poricidal anthers are important for Euglossa (Arriaga & Hernandez, 1998), such as Eugenia (Myrtaceae) and M. pudica (Fabaceae), which exhibited high frequencies in some samples. As for the latter, M. pudica is a ruderal species with flowering throughout the year but greater abundance in months with higher rainfall, and is considered crucial for the survival of several bee species (Marques et al., 2011). If Euglossini females do have preferences regarding pollen gathering, their search for nectar seems to be less specific (López-Uribe et al., 2008). Plants with nectar are frequently cited as being visited by Euglossini females and males (Janzen, 1971; Ramírez et al., 2002; Rocha-Filho et al., 2012), and some foraging by females was recorded in this study: e.g. C. prunifera (Arecaceae), Wedelia pilosa Baker (Asteraceae), Bignonia (Bignoniaceae), Centrosema brasilianum (L.) Benth., Copaifera, Delonix and Dioclea (Fabaceae), Hibiscus (Malvaceae), Manettia (Rubiacae), Zanthoxylum (Rutaceae), Cupania diphylla Vahl (Sapindaceae), and Lantana (Verbenaceae). The Dalechampia (Euphorbiaceae) pollen type, which occurred in six samples of E. cordata, may be singled out as the main source of floral resin for nest building (Armbruster, 1993; Opedal et al., 2016). Plants of this botanical genus are frequently pollinated by Euglossini bees, which has been well documented in the literature (Armbruster & Webster, 1981; Sazima et al., 1985; Opedal et al., 2016). The pollen of Byrsonima, which was shared between E. townsendi and E. securigera (with a relative frequency of 11.40% for the latter), is not commonly gathered by these bees. The Malpighiaceae family is frequently visited by ‘oil- gathering bees’ because of the use of floral oil to feed the larvae (Rêgo & Albuquerque, 2006); however, they are also visited for pollen gathering, as recorded among Eulaema (Ramírez et al., 2002). Thus, nothing prevents Euglossa females from also visiting these plants in search of this resource. The only nest of E. securigera occurred in Area I, and based on our observations, the locality contains many Byrsonima shrubs.On the other hand, E. townsendi also collected pollen from this plant, which is significant because it only nested in Area II, where plants of this genus were unusual; this indicates that the bees were not limited to the immediate vicinity of their nesting area for foraging. According to Janzen (1971), plants foraged by Euglossini bees provide high quality rewards as they flower over long periods of time. Thus, these bees habitually and repeatedly visit the same species when it is flowering. An example of a species foraged over a long period of time is Zanthoxylum (Rutaceae), which was very important for bee species in this study, possibly as a source of both pollen and nectar. Additionally, the pollen of Rutaceae (Citrus) was observed over nine months in E. atroveneta samples, although with low pollen frequency (Arriaga & Hernández, 1998). On the other hand, shorter flowering species can also be visited by these bees, as shown by the rare occurrence of these pollen types in the samples. Notably, the pollen types of Solanum, M. pudica, and Zanthoxylum were observed in most months during which the nests were established. They were of greater or lesser importance depending on the sample employed as the major pollen in the PCA ranking. Even samples of nests obtained in the same month, i.e. both E. cordata and E. townsendi, varied in terms of importance of the principal pollen type. According to Arriaga and Hernández (1998), an interesting behavior of these bees is that they can forage the same plants at the moment of nidification, but the way the resource is exploited can change; furthermore, individual preferences may differ among females, indicating a plasticity at the individual level. This is consistent with the findings of Cortopassi-Laurino et al. (2009), where the contents of brood cells were not homogeneous, and the polylectic behavior of Euglossa was observed over a matter of days. The higher diversity values in some samples show that the bees gathered resources in a heterogeneous manner, with up to ten pollen types in nest Ec.10. The mean diversity value of 0.80 was similar to that found for E. atroveneta (Arriaga & Hernández, 1998), which was 0.83. As for the uniformity of the samples, Et.06 had the greatest index, which shows that the female of that nest foraged resources in a more homogenous manner (Solanum 54.2%, M. pudica 40.2%, and Zanthoxylum 5.6%). On the other hand, sample Ec.08, with the least uniformity (0.084), indicates that the female gathered her resources in a heterogeneous manner, while having the greatest preference for Solanum (97.8%). This variation in the uniformity and diversity of pollen grains encountered in the nests can also be explained by the individual-level plasticity of female foraging. The Euglossini bees have considerable ability to fly several distances in search of food resources (Janzen, 1971). Thus, we consider that, although the bees founded their nests in different areas (open vegetation vs. shaded areas), this does not preclude species from foraging for their resources throughout the region of the Park and surrounding area and sharing their preferred resources. The Euglossa bees that nest and forage in the Rangedor State Park contribute to the pollination of the plant species present in the area, and by their capacity for displacement, can mediate gene flow with individuals located in other urban fragments, which is of prime importance for the conservation of vegetation. Acknowledgements The authors wish to thank Professor Angela Corrêa from Botanical Institute of São Paulo for her collaboration in the identification of pollen types, as well as Denilson Martins for identifying the specimens of Euglossa. This work was supported by the Maranhão Foundation for Support for Research and Scientific Development (Fundação de Amparo à Pesquisa e ao Desenvolvimento Científico e Tecnológico do Maranhão – FAPEMA) through grants to the RSP and PMCA. Sociobiology 66(1): 88-96 (March, 2019) 95 References Armbruster, W.S. (1993). Evolution of plant pollination systems - hypotheses and tests with the neotropical vine Dalechampia. Evolution, 47: 1480-1505. doi: 10.2307/2410162 Armbruster, W.S. & Webster, G.L. (1981). Sistemas de polinização de duas espécies simpátricas de Dalechampia (Euphorbiaceae) no Amazonas, Brasil. Acta Amazonica, 11: 13-17. Arriaga, E.R. & Hernández, E.M. (1998). Resources foraged by Euglossa atroveneta (Apidae: Euglossinae) at Union Juárez, Chiapas, Mexico. A palynological study of larval feeding. Apidologie, 29: 347-359. doi: 10.1051/apido:19980405 Augusto, S.C. & Garófalo. C.A. (2004). Nesting biology and social structure of Euglossa (Euglossa) townsendi Cockerell (Hymenoptera, Apidae, Euglossini). Insectes Sociaux, 51: 400-409. doi: 10.1007/s00040-004-0760-2 Augusto, S.C. & Garófalo, C.A. (2011). Task allocation and interactions among females in Euglossa carolina nests (Hymenoptera, Apidae, Euglossini). Apidologie, 42: 162- 173. doi: 10.1051/apido/2010040 Barth, O.M. (1989). O pólen no mel brasileiro. Rio de Janeiro: Luxor, 226 p. Boff, S. & Alves-dos-Santos, I. (2018). Cavities in bromeliad stolons used as nest sites by Euglossa cordata (Hymenoptera, Euglossini). Journal of Hymenoptera Research, 62: 33-44. doi: 10.3897/jhr.62.22834 Buchmann, S.L. (1985). Bees use vibration to aid pollen collection from non-poricidal flowers. Journal of the Kansas Entomological Society, 58: 517-525. Cameron, S.A. (2004). Phylogeny and biology of neotropical orchid bees (Euglossini). Annual Review of Entomology, 49: 377-404. doi: 10.1146/annurev.ento.49.072103.115855 Cortopassi-Laurino, M., Zillikens, A. & Steiner, J. (2009). Pollen sources of the orchid bee Euglossa annectans Dressler 1982 (Hymenoptera: Apidae, Euglossini) analyzed from larval provisions. Genetics and Molecular Research, 8: 546-556. doi: 10.4238/vol8-2kerr013 Erdtman, G. (1960). The acetolysis method. Svensk Botanisk Tidskrift, 54: 561-564. Garófalo, C.A., Camillo, E., Augusto, S.C., Jesus, B.M.V. & Serrano, J.C. (1998). Nest structure and communal nesting in Euglossa (Glossura) annectans Dressler (Hymenoptera, Apidae, Euglossini). Revista Brasileira de Zoologia, 15: 589-596. doi: 10.1590/S0101-81751998000300003 Garófalo, C.A., Camillo, E., Serrano, J.C. & Rebêlo, J.M.M. (1993). Utilization of trap nests by Euglossini species. Revista Brasileira de Biologia, 53: 177-187. Janzen, D.H. (1971). Euglossine bees as long-distance pollinators of tropical plants. Science, 171: 203-204. doi: 10.1126/science.171.3967.203 López-Uribe, M.M., Oi, C.A. & Del Lama, M.A. (2008). Nectar-foraging behavior of Euglossine bees (Hymenoptera: Apidae) in urban áreas. Apidologie, 39: 410-418. doi: 10.1051/ apido:2008023 Lorente, F.L., Buso Junior, A.A., Oliveira, P.E. & Pessenda, L.C.R. (2017). Atlas Palinológico: Laboratório 14C - Cena/ USP. Piracicaba: FEALQ, 333 p. Marques, L.J.P., Muniz, F.H., Lopes, J.S. & Silva, J.M. (2011). Levantamento da flora apícola em Santa Luzia do Paruá, Sudoeste da Amazônia, Maranhão. Acta Botanica Brasilica, 25: 141-149. Mendes, F.N., Rêgo, M.M.C. & Carvalho, C.C. (2008). Abelhas Euglossina (Hymenoptera, Apidae) coletadas em uma monocultura de eucalipto circundada por Cerrado em Urbano Santos, Maranhão, Brasil. Iheringia, Série Zoologia, 98: 285-290. doi: 10.1590/S0073-47212008000300001 Michener, C.D. (2007). The Bees of the World. Baltimore: John Hopkins University Press, 992 p. Nemésio, A. & Rasmussen, C. (2011). Nomenclatural issues in the orchid bees (Hymenoptera: Apidae: Euglossina) and an updated catalogue. Zootaxa, 3006: 1-42. doi: 10.5281/ zenodo.203410 Neves, E.L. & Viana, B.F. (1997). Inventário da fauna de Euglossinae (Hymenoptera, Apidae) do baixo sul da Bahia, Brasil. Revista brasileira de Zoologia, 14: 831-837. Nunes-Silva, P., Hrncir, M. & Imperatriz-Fonseca, V.L. (2010) A polinização por vibração. Oecologia Australis, 14: 140-151. doi: 10.4257/oeco.2010.1401.07 Odum, E.P. (1988). Ecologia. Rio de Janeiro: Editora Guanabara, 434 p. Opedal, Ø. H., Falahati-Anbaran, M. Albertsen, E., Armbruster, W.S., Pérez-Barrales, R., Stenøien, H.K. & Pelabon, C. (2016). Euglossine bees mediate only limited long-distance gene flow in a tropical vine. New Phytologist, 213: 1-11. doi: 10.1111/nph.14380 Otero, J.T., Campuzano, A.M.,Zuluaga, P.A. & Caetano, C.M. (2014). Pollen carried by Euglossa nigropilosa Moure (Apidae: Euglossinae) at la Planada Nature Reserve, Nariño, Colombia. Boletín del Museo de Entomología de la Universidad del Valle, 15: 1-6. http://hdl.handle.net/10893/8402 Ramalho, A.V., Gaglianone, M.C. & Oliveira, M.L. (2009). Comunidades de abelhas Euglossina (Hymenoptera, Apidae) em Fragmentos de Mata Atlântica no sudeste do Brasil. Revista Brasileira de Entomologia, 53: 95-101. Ramírez, S., Dressler, R.L & Ospina, M. (2002). Abejas euglosinas (Hymenoptera: Apidae) de la Región Neotropical: Listado de espécies com notas sobre su biologia. Biota Colombiana, 3: 7-118. RS Pinto, AG Silva, MMC Rêgo, PMC Albuquerque – Pollen analysis of the post-emergence residue of Euglossa96 Rebêlo, J.M.M., Rêgo, M.M.C. & Albuquerque, P.M.C. (2003). Abelhas (Hymenoptera, Apoidea) da região setentrional do Estado do Maranhão, Brasil. In G.A.R. Melo & I. Alves-dos-Santos (Eds.), Apoidea Neotropica: Homenagem aos 90 Anos de Jesus Santiago Moure (pp. 265- 278). Criciúma: Editora UNESC. Rebêlo, J.M. & Silva, F.S. (1999). Distribuição das Abelhas Euglossini (Hymenoptera: Apidae) no Estado do Maranhão, Brasil. Anais da Sociedade Entomológica do Brasil, 28: 389- 401. doi: 10.1590/S0301-80591999000300003 Rêgo, M.M.C. & Albuquerque, P.M.C. (2006). Polinização do murici. São Luís: EDUFMA, 104 p. Rocha-Filho, L.C., Krug, C., Silva, C.I. & Garófalo, C.A. (2012). Floral resources used by Euglossini Bees (Hymenoptera: Apidae) in coastal ecosystems of the Atlantic Forest. Psyche, 2012: 1-13. doi: 10.1155/2012/934951 Roubik, D.W. & Moreno, J.E. (1991). Pollen and Spores of Barro Colorado Island. St. Louis: Missouri Botanical Garden, 268 p. Sazima, M, Sazima, I. & Carvalho-Okano, R.M. (1985). Biologia floral de Dalechampia stipulaceae (Euphorbiaceae) e sua polinização por Euglossa melanotricha (Apidae). Revista Brasileira de Zoologia, 45: 85-93. Secretaria do Estado de Meio Ambiente e Recursos Naturais - SEMA. 2017. Parque Estadual do Sítio do Rangedor - Plano de Manejo. Available in: http://www.sema.ma.gov.br/ arquivos/1508965820.pdf Silva, A.R., Tauil, P.L., Cavalcante, M.N.S., Medeiros, M.N., Pires, B.N. & Gonçalves, E.G.R. (2008). Situação epidemiológica da leishmaniose visceral, na Ilha de São Luís, Estado do Maranhão. Revista da Sociedade Brasileira de Medicina Tropical, 41: 358-364. doi: 10.1590/S0037-86822008000400007 Silva, C.I., Castro, M.M.N., Santos, I.A., & Garófalo, C.A. (2016). High prevalence of Miconia chamissois (Melastomataceae) pollen in brood cell provisions of the orchid bee Euglossa townsendi in São Paulo State, Brazil. Apidologie, 47: 855-866. doi: 10.1007/s13592-016-0441-y Silva, C.I., Imperatriz-Fonseca, V.L., Groppo, M., Bauermann, S.G., Saraiva, A.M., Queiroz, E.P., Evaldt, A.C.P., Aleixo, K.P., Castro, J.P., Castro, M.M.N., Faria, L.B., Ferreira-Caliman, M.J., Wolff, J.L., Paulino-Neto, H.F. & Garófalo, C.A. (2014). Catálogo polínico das plantas usadas por abelhas no Campus da USP de Ribeirão Preto. Ribeirão Preto: Holos, 153p. Villanueva-Gutierrez, R., Quezada-Euan, J. & Eltz, T. (2013). Pollen diets of two sibling orchid bee species, Euglossa, in Yucatán, Southern Mexico. Apidologie, 44: 440-446. doi: 10.1007/s.13592-013-0194-9