Assessing the biodiversity and the impact of pollinators on carob production

vulpecula and Andrena aff. rufitibialis and Colletidae with Colletes brevigena, Colletes cyprius, Hylaeus cypricola, Hylaeus imparilis and Hylaeus taeniolatus. Colletes brevigena and H. taenio- latus were present in all sampling regions during both years (Fig 4). NW_Coast_4 was the most species-rich plot with eight species represented, followed by NW_Coast_1 with seven species, NW_Coast_3 with six species and S_Plateau_1, S_Plateau_2, S_Coast_4 and SE_Low- land_1 with five species each. The wasp specimens represented three species belonging to three genera and two families: Crabronidae with Cerceris sp. and Philanthus sp. and Vespidae with Vespula germanica (Fig 4). Cerceris sp. and V. germanica were present in all sampling regions, while Philanthus sp. was present only in NW_Coast and SE_Lowland. The impact of different factors on wild bee presence is shown in Table 1 (NW Coast, S. Coast and S. Plateau in 2016) and Table 2 (NW Coast, S. Plateau in 2016 and 2017). In both analyses, there was a significant effect of tree sex, A. mellifera presence, and wasp presence on wild bee presence (P < 0.001). The effect of region, week and year were not significant (P > 0.05). Sightings of wild bees were more frequent on male trees and trees with A. mellifera or wasp presence (Figs 2 and 3). Fig 2. Probability of sighting wild bees, A. mellifera, or wasps on female (F) and male (M) carob trees in the three sampling regions for 2016 and 2017 at

any 2 min sampling event. The S. Coast region was sampled in 2016 only. Each point represents the probability of observing at least one individual of the species group at a sampling point (each of four tree sides, five trees per plot, four plots per region) during five weeks of sampling. https://doi.org/10.1371/journal.pone.0291431.g002 PLOS ONE Biodiversity and the impact of pollinators on carobs PLOS ONE | https://doi.org/10.1371/journal.pone.0291431 October 20, 2023 6 / 16