Abstract
Angiosperms and their insect pollinators form a foundational symbiosis, evidence for which from the Cretaceous is mostly indirect, based on fossils of insect taxa that today are anthophilous, and of fossil insects and flowers that have apparent anthophilous and entomophilous specializations, respectively. We present exceptional direct evidence preserved in mid-Cretaceous Burmese amber, 100 mya, for feeding on pollen in the eudicot genus Tricolporoidites by a basal new aculeate wasp, Prosphex anthophilos, gen. et sp. nov., in the lineage that contains the ants, bees, and other stinging wasps. Plume of hundreds of pollen grains wafts from its mouth and an apparent pollen mass was detected by micro-CT in the buccal cavity: clear evidence that the wasp was foraging on the pollen. Eudicots today comprise nearly three-quarters of all angiosperm species. Prosphex feeding on Tricolporoidites supports the hypothesis that relatively small, generalized insect anthophiles were important pollinators of early angiosperms.
Highlights
Among symbiotic relationships unique to land, such as between fungi and plants in the forms of lichens and mycorrhizae, the pollination of angiosperms by insects has special ecological significance
Cretaceous nemestrinid and tabanomorph flies with long proboscides were interpreted as angiosperm pollinators[9], but a zhangsolvid fly in Early Cretaceous Spanish amber—with an even longer proboscis —had a pollen load from a gymnosperm in the Mesozoic group Benettitales[10]
The unusual, dipterous Parapolycentropus in Burmese amber, which has a fine, stylet-like proboscis, shares adaptive features with many empidid and ceratopogonid flies that today are insectivorous, a diet typical of mecopterans[12], but a specimen of this scorpionfly was recently found with nearby Cycadopites pollen[13]
Summary
Among symbiotic relationships unique to land, such as between fungi and plants in the forms of lichens and mycorrhizae, the pollination of angiosperms by insects has special ecological significance. Dispersed plants can better exploit limiting resources such as light gaps, moisture, and nitrogen, and they have reduced exposure to diseases and defoliating insects that overwhelm dense monocultures[4] It is likely, that insect pollination (entomophily) is the ancestral condition among angiosperms. The unusual, dipterous Parapolycentropus in Burmese amber, which has a fine, stylet-like proboscis, shares adaptive features with many empidid and ceratopogonid flies that today are insectivorous, a diet typical of mecopterans[12], but a specimen of this scorpionfly was recently found with nearby Cycadopites pollen[13] It may have fed on both: some hematophagous species of mosquitoes feed on nectar and are effective pollinators[14]
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