Gradual replacement of wild bees by honeybees in flowers of the Mediterranean Basin over the last 50 years

Abstract

1 Current evidence for generalized pollinator decline largely originates from mid-latitude 2 regions in North America and Europe. Unacknowledged geographical heterogeneity in 3 pollinator trends, in combination with geographical biases in pollinator studies, can 4 produce distorted extrapolations and limit understanding of pollinator responses to 5 environmental changes. In contrast to the severe declines experienced in some well-6 investigated European and North American regions, honeybees seem to have increased in 7 recent years over large expanses of the Mediterranean Basin. Since honeybees can have 8 negative impacts on wild bees, the hypothesis was formulated that if honeybees are 9 actually increasing in the Mediterranean Basin, then an extensive, biome-wide alteration 10 in the composition of bee pollinator assemblages may be currently underway there, 11 involving a progressive reduction in the importance of wild bees as pollinators. This 12 hypothesis was tested using a large data sample gathered from published investigations on 13 the composition of bee pollinators of wild and cultivated plants conducted between 1963-14 2017 in the Mediterranean Basin. Over this period, honeybee colonies increased 15 exponentially and wild bees were gradually replaced by honeybees in flowers of wild and 16 cultivated plants. Mean estimated proportion of wild bees at flowers roughly 17 quadruplicated that of honeybees at the beginning of the period considered, the 18 proportions of both groups becoming roughly similar fifty years later. The Mediterranean 19 Basin is a world biodiversity hotspot for wild bees and wild bee-pollinated plants, and the 20 ubiquitous rise of honeybees to dominance as pollinators could in the long run undermine 21 the diversity of plants and wild bees, as well as their mutualistic relationships in the 22 region.23 Herrera -3

Pollen transfer networks reveal alien species as main heterospecific pollen donors with fitness consequences for natives

“…significant connectance and nestedness) has also been observed in plant–pollinator visitation networks in this same ecosystem (Campos‐Navarrete et al., 2013; Parra‐Tab la et al., 2019). These results thus emphasize the potential importance of ‘super generalist’ pollinators in structuring both, plant–pollinator and pollen transfer networks, especially in invaded communities (see Herrera, 2020).…”

The state of the world’s urban ecosystems: What can we learn from trees, fungi, and bees?

“…Based on this estimation the map in Figure 3 shows that beekeeping based on current data is unsustainable in most locations in London. This is a serious problem for bee conservation because honey bees can outcompete wild bees by monopolizing floral resources (Geslin et al., 2017; Henry & Rodet, 2018; Herrera, 2020; Mallinger, Gaines‐Day, & Gratton, 2017; Ropars et al., 2019, 2020; Torné‐Noguera, Rodrigo, Osorio, & Bosch, 2016). Wild pollinator populations may also be weakened by diseases spilling over from honey bees (Alger, Alexander Burnham, Boncristiani, & Brody, 2019; Fürst, McMahon, Osborne, Paxton, & Brown, 2014; Graystock, Blane, McFrederick, Goulson, & Hughes, 2016; Singh et al., 2010).…”

Possible Spillover of Pathogens between Bee Communities Foraging on the Same Floral Resource

“…Managed colonies of honey bees have also experienced severe losses since the end of the 1980s [ 6 , 13 ], but analysis of large sets of data have suggested a gradual replacement of wild bees by honey bees in the Mediterranean basin over the last 50 years [ 14 ]. Many different stressors have been shown to affect pollinator populations.…”