A synopsis of the Bee occurrence data of northern Tanzania

Abstract Background Bees (Hymenoptera: Apoidea: Anthophila) are the most important group of pollinators with about 20,507 known species worldwide. Despite the critical role of bees in providing pollination services, studies aiming at understanding which species are present across disturbance gradients are scarce. Limited taxononomic information for the existing and unidentified bee species in Tanzania make their conservation haphazard. Here, we present a dataset of bee species records obtained from a survey in nothern Tanzania i.e. Kilimanjaro, Arusha and Manyara regions. Our findings serve as baseline data necessary for understanding the diversity and distribution of bees in the northern parts of the country, which is a critical step in devising robust conservation and monitoring strategies for their populations. New information In this paper, we present information on 45 bee species belonging to 20 genera and four families sampled using a combination of sweep-netting and pan trap methods. Most species (27, ~ 60%) belong to the family Halictidae followed by 16 species (35.5%) from the family Apidae. Megachilidae and Andrenidae were the least represented, each with only one species (2.2%). Additional species of Apidae and Megachilidae sampled during this survey are not yet published on Global Biodiversity Information Facility (GBIF), once they will be available on GBIF, they will be published in a subsequent paper. From a total of 953 occurrences, highest numbers were recorded in Kilimanjaro Region (n = 511), followed by Arusha (n = 410) and Manyara (n = 32), but this pattern reflects the sampling efforts of the research project rather than real bias in the distributions of bee species in northern Tanzania.


Introduction
Bees (Hymenoptera: Apoidea: Anthophila) play an important ecological role in ecosystem. They serve a pollination role through mutualistic interactions with plants that in turn maintain the functionality of natural ecosystem, enhancing crop production and hence promoting human well being (Potts et al. 2016). Improved pollination service is essential for biodiversity conservation because plants act as primary producers in ecosystem. Nonetheless, they provide a vast array of ecosystem services: carbon sequestration, soil erosion prevention, nitrification and maintaining water tables, just to name a few. About 94% flowering plants reproduction depend on animal pollination in particular bee pollinators (Ollerton et al. 2011). Therefore, bees are considered as the most important pollinator of crops and wild plants as they can visit more than 90% of the leading 107 global crop types (Klein et al. 2007).
Taxonomic information of bee species in many parts of the world is poorly understood (Williams et al. 2001, Winfree 2010, Eardley et al. 2016 and Tanzania is no exception. The distribution and diversity of wild bee species in Tanzania is equivocal, given the lack of a countrywide bee catalogue and limited scientific studies. Tanzania is renowned for its unique biodiversity and high endemism (URT 2014). With a mainland area of 945,087 km , lack of information on distribution and diversity of bee species poses a risky scenario, as unknown bee species may dissappear even before they are discovered and documented. On the other hand, decline of bee populations are increasingly becoming a global concern, a situation which jeopardizes provision of pollination sevices to both natural and agroecosystems (Westphal et al. 2008, Cameron et al. 2011, Koh et al. 2016, Potts et al. 2016, Tommasi et al. 2021. Nonetheless, knowledge of local bee fauna, including species present and their distribution, is worthy understanding and should be a conservation concern regardless of their importance in the agriculture sector. Research shows that landuse intensification, climate change, introduction of alien invasive species and pathogens are amongst the major driving factors for bee populations declines (Potts et al. 2016, Bartomeus andDicks 2019). There is also lack of empirical data on synergistic interaction of such factors owing to their interconnection and complexity which impedes the management and conservation of wild bee pollinators (Westphal et al. 2008, Gemmill-Herren et al. 2014, Potts et al. 2016).
In recent years, a few studies have provided partial information on the ecology of bees in Tanzania (Classen et al. 2015, Classen et al. 2017, Classen et al. 2020. However, these studies focused on bee diversity using morphospecies, plant-bee interactions and body size trait along elevation gradients of Mt.Kilimanjaro. Additionally, some studies on bee species conducted in the country were confined to a specific taxon, for example, in the genus Apis (Mumbi et al. 2014) and tribe Meliponini (Hamisi 2019). To date, no studies have comprehensively compiled occurrence of bee species in Tanzania to understand their diversity and distribution. In 2017, the College of African Wildlife Management, Mweka (CAWM), in collaboration with local and international partners, developed a three-year Bee Pollinator Monitoring Project to bridge this information gap. On this account, this paper presents bee occurrence data of northern Tanzania (Kilimanjaro, Arusha and Manyara administrative regions) with reference to an online dataset shared to the wider scientific community through https://doi.org/10.15468/hdcdf3 . The result is a qualitative improvement in the availability of primary data on the bee species of this country.

Goals:
The project's main goal was to determine the current distribution and status of bee pollinators in Tanzania. Other project objectives were: • To strengthen the capacity of Tanzanians in the aspects of biodiversity informatics; plant-bee interactions; DNA-based and morphological identification techniques; and collection management; • To develop and implement a standardized bee pollinator monitoring programme; • To share data on bee species, abundance and their interactions with plants via dedicated databases, such as Global Biodiversity Information Facility (GBIF), Tanzania Biodiversity Information Facility (TanBIF) and African Pollinator Initiative (API); • To disseminate results to the scientific community through peer-reviewed publications and conference presentations; and • To raise awareness of the general public on the importance of bee pollinators through various media.
Funding: The project is financed by the JRS Biodiversity Foundation, USA.

Study extent:
The study was carried out in a set of study sites established in agricultural (transformed), grazing (degraded) and natural savannah (conserved) lands to represent different land-use categories as presented in Table 1. Agriculture intensity was measured, based on magnitude of land use intensification, i.e. moderately intensive agriculture habitat was mainly characterized by smallholder farms with field sizes of less than 1 ha with mixed crops, such as maize, beans and sunflower. It is also characterized by moderate use of agricultural machines and agrochemicals, while intensive agriculture was characterized by monoculture farms. In this habitat, there is a high use of heavy agricultural machines and agricultural inputs (i.e. pesticides and chemical fertilizers). Nonetheless, grazing intensity was measured, based on the visual inspection of on-site signs of obvious grazing like shortened tufts of grass, presence or absence of livestock footprints and by calculating the distance between study sites to bomas (livestock enclosures and living grounds of families holding large herds of livestock) using remote sensing and GIS techniques. Study sites with signs of intensive grazing activity were very near to bomas (average distance 0.09 ± 0.05 (SD) km while study sites with moderate livestock grazing intensity were at a far distance to bomas (i.e. average distance 25.3 ± 27.6 km (SD). Sampling description: Data were collected in 40 study sites distributed along savannah, grazing and agriculture gradients in the three regions. A paired patch study design (i.e. sampling plots were positioned in two contrasting habitats within each study site) was used to minimize spatial autocorrelation. In each study site, two 50 x 50 m sampling plots were positioned and spaced at least 150 m apart. The coordinates of the plots were recorded at the mid-point between the paired plots. Bee data collection involved a combination of standardized pan trapping and random walk methods. These techniques have successfully been used for sampling bee species in northern Tanzania (Classen et al. 2015, Classen et al. 2017, Classen et al. 2020 and in other parts of the world (e.g. Noyes 1989, Stephen and Rao 2007, Westphal et al. 2008, Yi et al. 2012, Spafford and Lortie 2013. In each plot, four clusters of UV-Reflecting pan traps (each with yellow, white and blue) were installed and left in the field to collect bees for 48 hours. Two of the clusters were installed using a 120 cm pole to increase the chances of collecting bees foraging on shrubs and the other two were installed using a 35 cm pole to capture bees foraging on herbaceous plants. In each of three quota water-filled pan traps, a drop of scentless colourless liquid soap was added to break the surface tension and prevent bees from escaping. The total sampling effort for this technique summed to 1,152 hours per site. For the standardized random walk, two researchers actively collected bees for two hours within each sampling plot using sweep nets. This method summed to a sampling effort of four man-hours per study site.
Quality control: Controlling data: For each of the study sites, we recorded the habitat type, GPS coordinates and elevation (metres above sea level, m a.s.l.). The coordinates and elevation of localities were derived from a hand-held Garmin GPS (Model: GPSMAP64s; resolution ± 3 m; Garmin Ltd, Taiwan). In addition, for each study site, information on weather parameters (temperature and precipitation) and forage resources were recorded. The specimens collected were preserved in 70% ethanol before being mounted and identified by afro-tropical bee taxonomists (Alain Pauly and Connal Eardley). Bees were identified following the nomenclatural system of Michener 2007 "The Bees of the World, Second Edition" with the exception of the family Halictidae that followed Pauly 1990 and Pauly 1999. Both Michener (2007) and Halictidae taxonomic publications contain keys, diagnosis and descriptions of bees. The reference collections for identified bee species are available at the CAWM, Mweka.

Geographic coverage
Description: The study was conducted in the northern part of Tanzania i.e. Kilimanjaro, Arusha and Manyara regions (Fig. 1). The study regions are located between latitude 3°30' S and 4°45' S and longitude 4°30' E and 5°45' E. The study regions have two rainy seasons: a long rainy season from March to May and a short rainy season in November and December. Average annual rainfall ranges geographically between 1300 mm and 2400 mm. Annual mean maximum temperature (hottest season) is 25.4°C between July and September and minimum temperature (cold season) is 12.8°C between May and June.
Notes: Bees were collected intermittently between August and December 2018. Two study sites were visited per day for data collection using pan trap and sweep-net methods. Pan traps were left in the field to collect bees for 48 hours before they were emptied and moved to the next study site. Additionally, sweep-netting was used to collect bee species actively for two hours per study site, excluding handling and processing time. Data collection by handnet was conducted when bees were most active in the morning between 9:00 and 11:00 am.

Usage licence
Usage licence: Creative Commons Public Domain Waiver (CC-Zero) IP rights notes: These data can be freely used, provided their source is cited. The full scientific name including the genus name and the lowest level of taxonomic rank with the authority.

Data resources
kingdom The full scientific name of the kingdom in which the taxon is classified eventDate The date or date interval during which the occurrence record was collected. geodeticDatum The coordinate system and set of reference points upon which the geographic coordinates are based.
coordinateUncertaintyInMetres The horizontal distance from the given decimalLatitude and decimalLongitude in metres, describing the smallest circle containing the whole of the Location. organismQuantity A number or enumeration value for the quantity of organisms. organismQuantityType The type of quantification system used for the quantity of organisms samplingProtocol The description of the method used during sampling taxonRank The taxonomic rank of the most specific name in the scientificName.
scientificNameAuthorship The authorship information for the scientificName formatted according to the conventions of the applicable nomenclaturalCode.

ScientificName
The full scientific name of a taxon. acceptedNameUsage The full name, with authorship and date information, if known, of the currently valid or accepted taxon.
taxonomicStatus The status of the use of the scientificName as a label for a taxon