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| Angimordella burmitina
Bao, Wang, Li & Dilcher, 2019
The color and morphology of flowers are artistic only. Illustration: Ding-hau Yang.
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Significance:
Since Darwin, insect pollination was thought to be a key contributor to the Cretaceous radiation of angiosperms. Both insects and angiosperms were common during the mid-Cretaceous, but direct evidence for a Cretaceous insect-angiosperm pollination mode was until now absent. Here, we report a specialized beetle-angiosperm pollination mode preserved in Burmese amber where a tumbling flower beetle is carrying tricolpate pollen grains that belongs to the eudicots that comprise the majority of extant angiosperm species. Our study provides direct evidence of insect pollination of Cretaceous flowers, which is further supported by the flower-visiting body shape, specialized pollen-feeding mouthparts, and zoophilous pollen grains. These findings demonstrate that insect pollination of flowering plants was well established 99 million years ago.
Abstract
Insect pollination of flowering plants (angiosperms) is responsible for the majority of the world’s flowering plant diversity and is key to the Cretaceous radiation of angiosperms. Although both insects and angiosperms were common by the mid-Cretaceous, direct fossil evidence of insect pollination is lacking. Direct evidence of Cretaceous insect pollination is associated with insect-gymnosperm pollination. Here, we report a specialized beetle-angiosperm pollination mode from mid-Cretaceous Burmese amber (99 mega-annum [Ma]) in which a tumbling flower beetle (Mordellidae), Angimordella burmitina gen. et sp. nov., has many tricolpate pollen grains attached. A. burmitina exhibits several specialized body structures for flower-visiting behavior including its body shape and pollen-feeding mouthparts revealed by X-ray microcomputed tomography (micro-CT). The tricolpate pollen in the amber belongs to the eudicots that comprise the majority of extant angiosperm species. These pollen grains exhibit zoophilous pollination attributes including their ornamentation, size, and clumping characteristics. Tricolpate pollen grains attached to the beetle’s hairs are revealed by confocal laser scanning microscopy, which is a powerful tool for investigating pollen in amber. Our findings provide direct evidence of insect pollination of Cretaceous angiosperms, extending the range insect-angiosperm pollination association by at least 50 million years. Our results support the hypothesis that specialized insect pollination modes were present in eudicots 99 million years ago.
Keywords: amber, insect, angiosperm, pollen, paleoecology
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| Fig. 2. Angimordella burmitina and tricolpate pollen grains. (A) Habitus. Pollen grains attached to the body are indicated by red dots, unattached are indicated by yellow dots, clumped pollen are indicated by blue squares. (B−H) Locations are highlighted in A. (B and C) Pollen grains near the body. Yellow arrows point to colpi. (D and E) Pollen grains on the body. (F−H) Clumped pollen grains. (G and H) Locations are highlighted in F and G, respectively. Blue arrows point to colpi. |
Family Mordellidae Latreille, 1802.
Subfamily Mordellinae Latreille, 1802.
Angimordella burmitina gen. et sp. nov.
Etymology: The generic name is derived from the Latin prefix “angi” (referring to angiosperm) and the genus Mordella Linnaeus. The specific name is derived from Latin “Burmitina,” referring to the mineralogical name of Burmese amber.
Holotype :NIGP171315 (Fig. 1), a complete beetle with left side visible but its right side covered by abundant microbubbles. A thrip is near the maxillary palpi of the beetle on the left side.
Horizon and Locality: Mid-Cretaceous (∼99 Ma); Burmese amber, from the Hukawng Valley, Kachin State, Myanmar.
Diagnosis: Body small, with pronotum and elytra with wrinkles or ridges dorsally; antennae serrate; mesotibiae and metatibiae without any kind of ridge including subapical one; pygidium not well developed, shorter than 1/2 of last abdominal sternite.
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| Fig. 3. Ecological reconstruction of Angimordella burmitina. These tumbling flower beetles are feeding on eudicot flowers.
The color and morphology of flowers are artistic only.
Illustration: Ding-hau Yang.
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Tong Bao, Bo Wang, Jianguo Li, and David Dilcher. 2019. Pollination of Cretaceous Flowers. PNAS. DOI: 10.1073/pnas.1916186116
New fossil pushes back physical evidence of insect pollination to 99 million years ago phys.org/news/2019-11-fossil-physical-evidence-insect-pollination.html via @physorg_com
A Specialized Beetle-Angiosperm Pollination Mode from mid-Cretaceous Burmese Amber
A Specialized Beetle-Angiosperm Pollination Mode from mid-Cretaceous Burmese Amber
