47 million years ago it buzzed from flower to flower: Scientists discovered the remains of a fly in the lake sediments of the Messel pit, in whose belly they were able to detect pollen grains from different plant species. The astonishingly well-preserved fossil gave the researchers rare insights into the ecosystem of the time in the area where it was found and into the history of the role of flies as pollinators.
They feed on nectar and pollen – some insects, as is well known, perform an important service for many plant species: They spread the pollen and thus ensure pollination and seed formation. The best-known pollinators are probably bees, bumblebees and butterflies. However, some representatives of another group of insects are also on the move with the precious cargo in our ecosystems: “The fact that flies also play an important role as pollinators is often overlooked,” says Sonja Wedmann from the Senckenberg Research Institute and Nature Museum in Frankfurt.
Remnant of a pollinator insect
However, only a few fossils testify to the history of the development of the partnership between pollinators and flowering plants, because insects have rarely survived due to their filigree structures. The Messel pit is an exception. The special conditions during the fossilization in the lake, which was there in the Eocene era, have led to some amazingly well-preserved fossils. In addition to numerous vertebrates, some remains of insects have already been discovered in the oil shale slabs. In the current case, however, the researchers have made a very special find.
It is the remains of a fly, which was dated to an age of 47.5 million years. Many details, such as the veins of the wings of the eleven millimeter insect, can still be clearly seen. Based on the characteristics, the scientists were able to assign the fly to a previously unknown species of the Nemestrinidae family, which still exists today. “What is really special, however, is that we discovered numerous pollen in the insect’s abdomen,” says Wedmann. “Our research results now make it clear that this representative of the Nemestrinidae ate pollen around 50 million years ago,” says the scientist.
Insight into the former ecosystem
Apparently the fly had feasted on it before it died: the researchers were able to visualize the pollen meal in its abdomen as a three-dimensional bulge. Through electron microscopic examinations of the pollen grains they contained, they then also gained clues as to which plants the insect visited shortly before its death. Comparisons of the pollen structures showed: They were plants from the families of the sapote (Sapotaceae) and olive trees (Oleaceae), as well as from the genera of the water sessile oak (Decodon) and maiden vines (Parthenocissus). “Such fossil food remains are extremely rare worldwide. They give us information about the way of life, the eating behavior of the animals and the environmental conditions in which the insects lived at that time, ”says Wedmann.
As the researchers explain, the stomach contents of the newly discovered fly indicate that it was probably not in the then dense forests of the region, but rather in the shores of the Messelsee. Because the virgin vine is a typical plant of the forest edge and the pollen of the water loosestrife also points to the shore zone. “It is therefore very likely that the fly avoided long flights between the food sources and sought pollen from plants that were close together,” says Fridgeir Grímsson from the University of Vienna. “We assume that these insects played an important role in the distribution of the pollen of various plant taxa. Flies were important pollinators in the old (sub) tropical ecosystems and possibly even eclipsed the role of bees, ”says the researcher.
Source: Senckenberg Research Institute and Museum of Nature Frankfurt, University of Vienna, specialist article: Current Biology, doi: 10.1016 / j.cub.2021.02.025