Beetles: the first to pollinize gymnosperm and angiosperm plants

Amber pieces with trapped fossils are windows to the past which sometimes shock us with revealing images of life on Earth. Now, a scientific team describes the first insect record -specifically beetles- trapped in amber pieces about 99 million years ago while these pollinized gymnosperm and angiosperm plants simultaneously, which was not described until now in the scientific bibliography.

These Cretaceous amber pieces, found in sites of the area of Kachin (Myanmar), show new aspects on the biology and behaviour of four beetle fossil species from the Kateretidae family. This group of insects -with less than a hundred species- are currently pollinisers of angiosperm plants in South America and other warm and subtropical areas of the planet.

The findings proof the decisive role of beetles in the origins of pollination of angiosperms (plants with visible flowers) and their decisive role in the evolution of terrestrial ecosystems in the planet. The new study also describes a new type of pollen fossilized in amber, now named Praenymphaeapollenites cenomaniensis.

Among the participants in the study, published in the journal iScience, are Professor Xavier Delclòs, from the Faculty of Earth Sciences and the Biodiversity Research Institute (IRBio) of the UB, and researcher David Peris, first author of the study and postdoc at the University of Bonn (Germany), with a PhD from the University of Barcelona. Other participants in the article are the experts Conrad C. Labandeira, from the Smithsonian National Museum of Natural History (Washington, United States); Eduardo Barrón, from the Geological and Mining Institute Spain (IGME); Jes Rust, from the University of Bonn, and Bo Wang, from the Nanjing Institute of Geology and Palaeontology (China).

Amber is a fossilised resin from millions of years ago that can preserve fossil organisms with a great morphological and structural loyalty. In some cases, amber provides information on the aspects of the behaviour of extinct species.

Pieces of Burmese amber in the new study correspond to the Cenomanian period, when dinosaurs spread around all continents. Experts identified several specimens of beetles in three pieces while there was only one model of the fourth specimen. Currently, all this fossil material found in Southern-east Asia is in the Natural Science Museum of Barcelona and the Nanjing Geology and Palaeontology Institute (China).

A large group of an only species of beetles in an amber piece “could only be explained due to mating or pollination”, notes Professor Xavier Delclòs, from the Department of Earth and Ocean Dynamics and IRBio, who studied the pieces in MCNB. “It is not common to find amber pieces that captured several organisms. And it is not easy to find fossils describing behavioural aspects of living beings, specially, related to pollination”, adds David Peris, head of the research project on the material of this fossil amber.

Traditionally, beetles were regarded as one of the insect group to pollinize the first flowers on Earth. The new study reveals that in these three pieces of amber, the pollen seeds found near the beetles correspond to gymnosperm plants (without visible flowers), older than angiosperm plants. In the fourth case, the pollen came from lilies, water plants from the Nymphaeaceae family (primitive angiosperm group).

“Karetide beetles fed from pollen seeds and other plant components from gymnosperms. When angiosperm plants spread, these represented a new food resource for beetles, which could feed from new resources (pollen, nectar and flower petals)”, notes David Peris.

“Therefore -he continues- these coleoptera adapted to the new resource offered by flowers and favoured the beginning of a mutual relationship in the process of pollination between these insects and angiosperm plants”.

In current ecosystems, the polliniser agent in most gymnosperm plants is the wind (anemophilous pollination) and as for angiosperms, the insects (entomophilous pollination). In this evolutionary context of the pollination process in the plant field, “the new study shows the great evolutionary advantage of the adaptation of beetles to the pollination of angiosperm plants, since there are no katekeridae related to gymnosperm plants now”, conclude David Peris and Xavier Delclòs.

Source:PressUB