Open access journal: http://periodicos.uefs.br/ojs/index.php/sociobiology ISSN: 0361-6525 DOI: 10.13102/sociobiology.v65i3.2824Sociobiology 65(3): 527-530 (September, 2018) Floral Resources Partitioning by Two Co-occurring Eusocial Bees in an Afromontane Landscape Eusocial bees with large colonies are crucial actors in many ecosystems. In addition to pollinating numerous plants, they affect other flower visitors’ behaviour and food choice by consuming a large part of floral resources due to their high numbers and biomass (e.g. Whitfield et al., 2006). Individual species of eusocial bees influence the food niche of each other as well. In the tropics, such interspecific interactions in competition for food sources have been studied mainly among various bee species with an introduced honeybee, Apis mellifera Linnaeus (e.g. Sommeijer et al., 1983; Ramalho et al., 2007; Franco et al., 2009; Liu et al., 2013; Hilgert-Moreira et al., 2014). On the other hand, we have surprisingly limited knowledge on resource partitioning among eusocial bees in the Afrotropics, where A. mellifera is native (Whitfield et al., 2006). To Abstract Floral preferences of generalist foragers such as eusocial bees influence the success of pollination of many flowering plants, as well as competition with many other bee species in tropical communities. Eusocial bees are important for the pollination success of many flowering plants, as well as for food resources availability for many other species. However, their foraging preferences are still unknown in many tropical areas, especially in the Afrotropics. We studied the foraging activity of two syntopic eusocial bees with large colonies, the honeybee Apis mellifera Linnaeus and the stingless bee Meliplebeia ogouensis (Vachal), on seven plant species in the Bamenda Highlands, Cameroon, in two consecutive years. Simultaneously, we quantified intra- and inter-annual changes in the food resources. We observed resource partitioning among the two bee species. Although both species are considered as generalists, their short-term food niches overlap was very low. Their preferences to the most often visited plants differed even more strongly inter- annually. Our results bring the first evidence on such relatively strong resource partitioning among two dominant eusocial bee species from West/Central Africa. Sociobiology An international journal on social insects R TROPEK1,2*, E PADYŠÁKOVÁ1,2, Š JANEČEK1,3 Article History Edited by Cândida Aguiar, UEFS, Brazil Received 02 January 2018 Initial acceptance 02 May 2018 Final acceptance 03 May 2018 Publication date 02 October 2018 Keywords Apinae, Apis mellifera; honeybee; stingless bees; interspecific interactions; pollination. Corresponding author Robert Tropek Department of Ecology, Faculty of Science, Charles University, Viničná 7, CZ-12844 Prague, Czechia Email: robert.tropek@gmail.com our knowledge, the only study from this region focused on the pollen foraging of A. mellifera and two stingless bee species of Meliponula in Uganda (Kajobe, 2007). Nevertheless, such data are crucial to understanding the dynamics in flower visitor insect communities, as well as to the role of eusocial bees on the evolution of plant pollination systems. To fill this gap, we bring the first data on food partitioning among two dominant eusocial bees, A. mellifera and the stingless bee Meliplebeia ogouensis (Vachal), from the Afromontane landscape of Mendong Buo, NW Cameroon (6°5’21’’ N, 10°18’11’’ E). It is a mosaic-like landscape of montane forest remnants and open habitats (Tropek & Konvicka, 2010). From late November till early January (i.e. the first half of the dry season) of 2007/2008 and 2008/2009 we recorded 1- Department of Ecology, Faculty of Science, Charles University, Prague, Czechia 2- Biology Centre, Czech Academy of Sciences, Institute of Entomology, České Budějovice, Czechia 3- Institute of Botany, Czech Academy of Sciences, Třeboň, Czechia SHORT NOTE R. Tropek et al. – Resources partitioning by eusocial bees528 the two bee species visiting flowers of seven plant species whose flowers dominated the studied sites in stream gallery vegetation (Acanthaceae: Brillantaisia lamium, Hypoestes aristata; Campanulaceae: Lobelia columnaris; Hypericacea: Hypericum revolutum, H. roeparianum; Lamiaceae: Pycnostachys eminii; Rubiaceae: Virectaria major; see Bartoš et al. (2012, 2015) for the plants characterisation, pictures and functional specialisation). All of them produce nectar, except H. roeparianum (Bartoš et al., 2012). Only B. lamium, H. aristata and P. eminii have flowers of mellitophilous pollination syndrome. In our previous studies (Padyšáková et al., 2013; Bartoš et al., 2015), H. aristata and H. roeparianum were shown to be flowers more commonly visited by A. mellifera, while H. revolutum was visited mainly by M. ogouensis. The bee visits were recorded along sixteen 15 m transects of gallery vegetation, where 5-min observations of each plant species per sampling session were equally distributed within the day (between 9 to 16 h) and study periods (altogether 29 and 33 sampling days in the two sampling periods, respectively). During the sessions, only visitors of a single observed plant species were recorded; one visiting individual was counted just once independently on the number of visited flowers. Each plant species was observed for about 10 hours in total (Bartoš et al., 2012). The possible partitioning of resources by the bees was analysed by a chi-square test of a contingency table (7 plants × 2 bees) with frequencies of visits in individual cells, performed in R v. 2.15.0 (R Development Core Team, 2012; Fig. 1). We also calculated the Schoener index of niche overlap combining the proportions of visits of both bee species on flowers of the particular studied plants (Schoener, 1968; Aguiar et al., 2017). The numbers of flowers along the transects were counted seven and four times in the two successive sampling periods, respectively (Janeček et al., 2012), and they remained mostly constant during both sampled dry season beginnings (Fig. 2). As the exceptions, flower numbers increased for L. columnaris and decreased for P. eminii during both sampled periods, whilst the flower numbers of V. major and B. lamium decreased during the second sampling period only. Altogether 253 A. mellifera and 373 M. ogouensis bee-plant interactions were observed in both sampling periods: 121 and 238 visits in 2007/2008, and 132 and 135 visits in 2008/2009 (Fig 1; Online Resource 1). During the sampling, A. mellifera visited mainly H. aristata (n = 60), followed by L. columnaris (n = 20), V. major (n = 17) and H. revolutum (n = 17) in 2007/2008, whereas it visited H. revolutum (n = 58), P. eminii (n = 41) and H. aristata (n = 25) in 2008/2009. M. ogouensis visited mainly H. revolutum (n = 182) and H. roeparianum (n = 34) in 2007/2008, and H. revolutum (n = 82) and L. columnaris (n = 51) in 2008/2009. Although both bees are generalists, each species preferred only part of available floral sources (Χ2 = 215.9089; df = 6; p ˂ 0.01; Fig 1), revealing thus a food source partitioning between them and low overlap of their niches. This was confirmed also by low Schoener index: 0.23 and 0.48 for the two periods, respectively, while the niches are considered to be overlapped for values over 0.6 (Schoener, 1968; Aguiar et al., 2017). Such niche partitioning among A. mellifera and various stingless bees was already described from various regions, usually interpreted as a result of differences in foraging behaviour, although an aggressive interspecific interference driven by larger honey bees is also sometimes hypothesised (e.g. Sommeijer et al., 1983; Ramalho et al., 2007; Kajobe, 2007). The visitation rates of individual plants by both bees, however, differed during and between sampling periods (Fig 1 and 2). The strongest shift in resource partitioning among the two bee species involved the flowers of L. columnaris, between years, and the flowers of H. revolutum, intra-annually. During the first year, preference of A. mellifera toward L. columnaris followed its blooming during the second half of the period, while it visited H. aristata more or less during Fig 1. Number of visits to each plant species by the two bee species, in the Afromontane landscape of Mendong Buo, NW Cameroon, in two sampled dry seasons. LobCol: Lobelia columnaris, HypRev: Hypericum revolutum, HypAri: Hypoestes aristata, PycEmi: Pycnostachys eminii, HypRoe: Hypericum roeparianum, VirMaj: Virectaria major, BriLam: Brillantaisia lamium. Sociobiology 65(3): 527-530 (September, 2018) 529 the whole period. A. mellifera strongly dominated on P. eminii in the beginning, switching to H. revolutum later after the first species overflowered, mainly in the second year. Meliplebeia strongly preferred H. revolutum in the beginning of both sampled periods, but almost entirely switched to L. columnaris later in the second year. 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