First Record of Brazil nut Pollinators Outside Amazon Biome

We present the first records of insect visitors and pollinators of Bertholletia excelsa (Lecythidaceae) in a 25 years plantation outside the Amazon biome, flowering and producing Brazil nuts. We installed a platform to observe and photograph the insects. The collected insects were stored, mounted, and identified by specialists. Six species were observed, three of them classified as potential pollinators ( Centris lutea , Eulaema nigrita , Eulaema cingulata ). The species E. nigrita and E. cingulata were already reported as a pollinators of Brazil nut in Amazon. This is the first record of C. lutea as potential pollinators for B. excelsa .


INTRODUCTION
The Brazil nut tree (Bertholletia excelsa Bonpl.; Lecythidaceae), also known as the Pará nut tree, occurs naturally in the Amazon rainforest, and in Brazil occurs in the states of Acre, Amazonas, Pará, Roraima, Rondônia, and part of Mato Grosso (Flora do Brasil, 2019). Its main commercial product is a nut, known as the Brazil nut by importing countries, which is consumed in natura or in the form of a by-product, such as oil or milk. In 2018, Brazil nut exports reached 11,000 tons (CONAB, 2019), highlighting its economic and social importance for local communities that rely on forest resources for income and labor.
In its natural habitat B. excelsa is pollinated by large robust native bees, which have sufficient strength to uncurl the hood of the flower and reach the nectary (Cavalcante et al., 2012).
These bees, some of them also commonly known as carpenter bees, require favorable conditions to inhabit the region and perform pollination, and the decrease in the populations of these large bees directly impacts the fruiting of the Brazil nut tree, which is allogamous and self-incompatible (Maués, 2002;Maués & Oliveira, 2010;Cavalcante et al., 2012;Maués et al., 2015), requiring cross pollination between tree individuals.
Regarding the production outside its natural occurrence area, there are few studies on the establishment of Brazil nut plantations outside the Amazon region (Homma et al., 2014), but there are no reports of B. excelsa fruiting on a large scale outside its natural occurrence area. However, this rule does not apply in a plantation established in January of 1996, in Lavras, southern Minas Gerais, Brazil (21°13'29.92"S 44°58'23.14"W, 922 m elevation). The plantation is an agroforestry system of B. excelsa intercropped with Hevea brasiliensis (Euphorbiaceae), with approximately 90 plants spaced 9 m² apart. The B. excelsa seeds were brought from the northern region of the state of Mato Grosso. During the last 25 years the management consisted at constant weed and ant control, and no thinning or pruning was performed.
Among the 78 B. excelsa survival trees in the area, six trees with flowers were identified in the 2019, 11 were identified in the 2020, and 12 at 2021 flowering season; in addition to flowering, these trees also produced fruits. The first fructification was observed when the trees were 20 years old, and since then, the number of fruit-producing individuals has increased, and so has the number of fruits each year. The flowering and fruiting trees are the largest in the area and dominate the canopy.
A platform of approximately 18 m high was erected at the same level of the canopy to facilitate the observation and capture of the potential pollinators and the recording of other floral visitors. In addition, photographic monitoring was performed to obtain images of the insects with a Canon Power Shot SX 50 HS digital camera, and observations were performed using Nikon Action 08 X 40 binoculars.
Insect survey occurred during the flowering season (January to April), five days per week, during 6 hours (from 6 am to 12 pm). Insects visiting the flowers were collected with an entomological net, stored in 70% alcohol (v/v) and subsequently mounted on entomological pins and identified by experts from the Department of Entomology of the UFLA and Laboratory of Bionomy, Biogeography and Insect Systematics (BIOSIS) of the Biology Institute of the Federal University of Bahia (UFBA) using taxonomic keys and the recorded images.
Six insect species of the order Hymenoptera were observed visiting B. excelsa flowers ( Table 1). The insects recognized as potential pollinators were all bees of the Apidae family (Figure 1).   The classification of the species observed in this study (i.e., floral visitors and pollinators) may vary if we consider that the studied plant is far from its natural area of occurrence.
Despite the species Xylocopa (Neoxylocopa) frontalis (Olivier, 1789) (carpenter bee of the family Apidae) being one of the most abundant and frequent species in pollination studies in the Brazilian south-eastern region, and has been recorded as a pollinator of Brazil nut trees in the northern and north-eastern regions of Brazil (Maués, 2002;Oliveira-Filho & Freitas, 2003;Cavalcante et al, 2018) there was no visual or collected records of such species on the present study.
Three other insect species visited the flowers, but they were not found to be effective pollinators due to their small body size what makes it impossible for them to lift the hood of the flowers and reach the nectary [Euglossa (Euglossa) cordata (Linnaeus, 1758), Trigona hyalinata (Lepeletier, 1836) bees of the family Apidae and Crematogaster sp. (Formicidae)] (Figure 2). The fact that these insect species are not strong enough to raise the hood of B. excelsa flowers hinders pollination but does not prevent them from being successful in collecting food ( Figure 2).
The successful establishment and production (flowering and fruiting) of Brazil nut under a different climatic zone is relevant on an ecological, economic and social aspect. We can zone areas with the possibilities of nut cultivation due to the presence of potential pollinators, in addition to the edaphoclimatic characteristics. Possibly the viability will be associated with the presence of large size bees. The widespread cultivation of Brazil nuts will generate income for the farmer and entrepreneur. The promotion of long-term projects deepens the man-land relationship, and increases food security for the families involved.