A primer of host-plant specialization in bees

The bee-flower biological association is one of the most famous examples of insect-plant interactions, and it is axiomatic that these are of critical importance for sustaining thriving terrestrial ecosystems. Yet, the most familiar associations are often artificially managed agricultural ecosystems, reflecting an exceptionally narrow range of bee species (often only one) and a concomitantly restricted range of associated behaviors, morphologies, and mechanisms tied to pollination. Here we provide a brief account of the range of bee-floral associations encompassing floral specialization in terms of diet, behavior, and morphology. These natural associations not only promote healthy ecosystems, but also can be integrated in sustainable ways for more efficient pollination of crops by targeting bee species whose diets, behaviors, and pollen-gathering structures evolved precisely to visit such floral species rather than less efficient, and often non-native, generalists that are otherwise exploited for such purposes.

POLLEN GIVING PLANTS VISITED BY THE HONEY BEE (APIS MELLIFERA L.)

The analysis of the honey plants in the area of apiculture is very important about the development, reproduction and productivity of bee colonies. The knowledge of the floral specialization of Apis mellifera L. is main point for good beekeeping practices. The bees have visited 46 species of honey plants from 41 genera and 22 families. The honey bees prefer to collect pollen from 2 to 5-6 plant species during every single month. Bees mainly collect pollen from two or three plants every month. The agricultural species Brassica napus as well as the meadow flora – Сentaurea solstitialis and Centaurea cyanus are the most visited honey plants during their flowering. Bees prefer to collect pollen from 16 plants out of 46 visited taxons. Not all plants in the area serve as a source of pollen for the bees. The greatest amount of collected pollen comes from Brassica napus – 3798.69 g. The visited cultivated honey taxons are around 22 % but about 56.5 % of the total amount collected pollen. Around 78 % of the visited plants are common natural as well as about 43.5 % of the total amount collected pollen. Key words: honey bee, honey plants, pollen, pollen traps, melissopalynologia, specialization

Revision of the bee group Anthophora (Micranthophora) (Hymenoptera: Apidae), with notes on potential conservation concerns and a molecular phylogeny of the genus

Anthophora (Micranthophora) comprises the largest subgenus of Anthophora in the Western Hemisphere, with 26 species. Though previously synonymized with the Anthophora (Heliophila), A. (Micranthophora) is here confirmed as a subgenus, morphological and multi-gene molecular phylogenetic evidence refute this and the synonymy of A. (Micranthophora) to A. (Heliophila) is formally rejected. Characters for (Micranthophora) are given and a key to species is provided. Seven new species are described: Anthophora (Micranthophora) caudata Orr, sp. nov.; Anthophora (Micranthophora) chihuahua Orr, sp. nov.; Anthophora (Micranthophora) escalante Orr, sp. nov.; Anthophora (Micranthophora) parkeri Orr, sp. nov.; Anthophora (Micranthophora) rara Orr, sp. nov.; Anthophora (Micranthophora) striata Orr, sp. nov.; and Anthophora (Micranthophora) timberlakei Orr, sp. nov. Further, four new synonyms are enacted: A. arthuri and A. flexipes to A. albata, A. nigritula to A. exigua, and A. xanthochlora to A. pachyodonta. Distributional and phenological data, as well as known details of nesting biology and floral specialization, are provided. Future research directions and species of potential conservation interest are also discussed.

Hummingbird pollination and the diversification of angiosperms: an old and successful association in Gesneriaceae

The effects of specific functional groups of pollinators in the diversification of angiosperms are still to be elucidated. We investigated whether the pollination shifts or the specific association with hummingbirds affected the diversification of a highly diverse angiosperm lineage in the Neotropics. We reconstructed a phylogeny of 583 species from the Gesneriaceae family and detected diversification shifts through time, inferred the timing and amount of transitions among pollinator functional groups, and tested the association between hummingbird pollination and speciation and extinction rates. We identified a high frequency of pollinator transitions, including reversals to insect pollination. Diversification rates of the group increased through time since 25 Ma, coinciding with the evolution of hummingbird-adapted flowers and the arrival of hummingbirds in South America. We showed that plants pollinated by hummingbirds have a twofold higher speciation rate compared with plants pollinated by insects, and that transitions among functional groups of pollinators had little impact on the diversification process. We demonstrated that floral specialization on hummingbirds for pollination has triggered rapid diversification in the Gesneriaceae family since the Early Miocene, and that it represents one of the oldest identified plant–hummingbird associations. Biotic drivers of plant diversification in the Neotropics could be more related to this specific type of pollinator (hummingbirds) than to shifts among different functional groups of pollinators.

Pollination ecology and circadian patterns of inflorescence opening of the Madagascan climber Dalechampia aff. bernieri (Euphorbiaceae)

Floral morphology often directly influences interactions with pollinators, but less is known about the role of extrafloral structures. We studied the relationship between bract motility, floral structural specialization and pollination in Dalechampia aff. bernieri, an endemic Madagascan species with floral structures indicating specialized buzz-pollination. We measured circadian bract angles in 47 inflorescences from 11 plants of D. aff. bernieri; in addition, we recorded any flower-visiting insects observed. The inflorescences had motile bracts with mean angles varying from ~50° at 00h00 to ~90° at 10h45. They were visited by buzz-pollinating Nomia viridilimbata bees (Halictidae), but also by non-buzz-pollinating Liotrigona bees (Apidae). The temporal pattern of bract motility observed in D. aff. bernieri may represent an extra-floral specialization to reduce visitation by non-pollinating visitors while maximizing visitation by diurnal buzz-pollinating bees.

Pre-adaptations and the evolution of pollination by sexual deception: Cope's rule of specialization revisited

Pollination by sexual deception is arguably one of the most unusual liaisons linking plants and insects, and perhaps the most illustrative example of extreme floral specialization in angiosperms. While considerable progress has been made in understanding the floral traits involved in sexual deception, less is known about how this remarkable mimicry system might have arisen, the role of pre-adaptations in promoting its evolution and its extent as a pollination mechanism outside the few groups of plants (primarily orchids) where it has been described to date. In the Euro-Mediterranean region, pollination by sexual deception is traditionally considered to be the hallmark of the orchid genus Ophrys . Here, we introduce two new cases outside of Ophrys , in plant groups dominated by generalized, shelter-mimicking species. On the basis of phylogenetic reconstructions of ancestral pollination strategies, we provide evidence for independent and bidirectional evolutionary transitions between generalized (shelter mimicry) and specialized (sexual deception) pollination strategies in three groups of flowering plants, and suggest that pseudocopulation has evolved from pre-adaptations (floral colours, shapes and odour bouquets) that selectively attract male pollinators through shelter mimicry. These findings, along with comparative analyses of floral traits (colours and scents), shed light on particular phenotypic changes that might have fuelled the parallel evolution of these extraordinary pollination strategies. Collectively, our results provide the first substantive insights into how pollination sexual deception might have evolved in the Euro-Mediterranean region, and demonstrate that even the most extreme cases of pollinator specialization can reverse to more generalized interactions, breaking ‘Cope's rule of specialization’.