Scientists reconstruct evolution of mosquito groups from the dinosaur era – 01/08/2021 – Science

Over the past 15 years, two researchers have dedicated themselves to telling a story spanning more than 100 million years using practically only a microscope, tweezers and a well-trained eye. Intensely reviewing the literature on the subject, traveling the world to collect specimens and analyzing others deposited in natural history museums, researchers Sarah Siqueira de Oliveira, currently a professor at the Federal University of Goiás (UFG), and Dalton de Souza Amorim, a professor at Faculty of Philosophy, Sciences and Letters of Ribeirão Preto, University of São Paulo (FFCLRP-USP), published the most complete work done to date on a subgroup of the so-called fungus mosquitoes.

The publication, with more than 100 pages and 107 figures, mostly in color, occupies an entire volume of the traditional Bulletin of the American Museum of Natural History, published since 1881 by the North American Museum. The work also makes clear the importance of continuous public funding for science, since it has been supported by several FAPESP projects since 2004.

Among the novelties, the extensive survey led to the description of new species and a new proposal for classifying the Mycetophilidae family, as the group of so-called fungus mosquitoes is known.

Emerging at the end of the Jurassic, more than 145 million years ago, and having diversified to the present day, mosquitoes of the Mycetophilidae family (whose name, in Latin, means “that like fungus”) have larvae that feed on mushrooms, wood ears, spores and other parts of these organisms that grow on decaying wood.

The researchers looked at a subgroup called Leiinae, which originated in the south of the supercontinent Gondwana, which later divided into present-day South America, Africa and Antarctica, India, Australia and New Zealand.

The group, which coexisted with the dinosaurs, is one of five subfamilies and one of the most diverse within Mycetophilidae, with more than 600 species described for the whole world. There are at least 2,000 species that still lack description. The new work concluded that the subfamily contains 37 genera and has some fossils preserved in amber.

“There was no consensus in the scientific literature about which groups belonged to this subfamily. We chose, then, to work both in the description and naming of species, and in understanding evolutionary relationships. It’s a very diverse and little-known group in the neotropical region,” says Oliveira, who carefully studied over a thousand specimens to complete the work.

The researcher began studying the evolution of insects while still studying biology at USP in Ribeirão Preto. At the time, the Biota-Fapesp Program, launched in 1999, was in its early years. There was, therefore, a large amount of material collected to be identified, an opportunity for Oliveira to study fungus mosquitoes. This first work had a scientific initiation grant from FAPESP, between 2005 and 2006.

The research was part of a larger project, “Geographic limits and causal factors of endemism in the Atlantic Forest in Diptera”, coordinated by Amorim, his supervisor, within the scope of Biota. Also as part of this project, the researcher completed her master’s and doctoral degrees.

While undergraduate efforts were dedicated to identifying specimens collected in the Atlantic Forest and the master’s project focused on a particularly diverse genus, the doctoral work aimed at a broad analysis of the Leiinae subfamily – until then one of the least studied among mosquitoes. -fungus. The latter served as the basis for the current publication, which was expanded with the results of the postdoctoral, also supported by FAPESP.

“Insects are very old groups and many have worldwide distribution. That’s why, as an advisor, I usually choose topics in which students become world leaders in groups that have few experts. We chose this important group because there was a knowledge gap there. And with this work, Sarah assumed leadership in the area,” says Amorim.

Jurassic Park

Becoming an authority on a group of animals that occurs around the world requires examining the specimens personally. Many specimens can be found in the collections of natural history museums, institutions whose mission is to preserve the largest and most diverse possible number of specimens of animals, vegetables and minerals.

For his doctorate, Oliveira went to Australia and analyzed the collections of the Australian Museum (AMSA), in Sydney, and the CSIRO-ANIC, in Canberra; on the way back to Brazil, he stopped to work at the South African museums of Kwa-Zulu Natal (NMSA), Iziko (SAMC) and Pretoria (National Collection).

On another trip, he studied collections from the United States and Canada. As a postdoctoral fellow, part of it with a Fapesp Research Internship Scholarship Abroad, Oliveira spent a period studying the collection of the Natural History Museum in London. She also took advantage of her stay in Europe to visit museum collections in France and Germany.

Among studies in loco and material sent by correspondence, collections from ten countries were analyzed. Amorim, in turn, collected in Chile, New Zealand, Australia, Costa Rica, California and Nepal, in addition to Brazil.

“An important part of this work was bringing back to Brazil specimens that had been collected here, but which did not exist in Brazilian collections. They are very diverse animals in the neotropical region, which originated in southern Gondwana and then spread to the rest of the world. Historically, however, researchers from Northern Hemisphere countries described many Brazilian species until the 1940s. A part of the collections has now been repatriated”, says the researcher.

In some of the museums, part of the agreement for Oliveira to carry out his studies was to organize collections of mosquitoes, often kept for years without a specialist to identify and organize the material.

“Many were single copies or with few units, in addition to being very old. These factors often make genetic analysis impossible. However, the study of morphology using a microscope is sufficient to obtain most of the evidence in our work. In addition, it is not possible to study the genetic material of fossils and their morphology is the source of information that allows them to be included in the system”, explains Amorim.

One of the principles of the work of taxonomists like Oliveira and Amorim is precisely to find patterns of sharing characters in the morphology of animals — such as wings, legs and other parts that make them unique. In the study published now, 128 characters were used to differentiate genders, such as structures of the head, chest, legs, wings and sexual organ.

To create a classification structure with all the subfamily’s genera, the researchers added three new tribes to the four existing ones. The study included 54 known species of fossils, 12 of which are extinct genera, eight of which have specimens preserved in amber, a crystallized form of tree sap that gained fame in the 1993 movie Jurassic Park.

The insect that appears in the film, in fact, did not feed on blood as shown, according to Amorim: it is one of the fungus mosquitoes of the Keroplatidae family.

“Dinosaurs are always a blockbuster, but few people talk about where they lived, what they ate, what other beings lived around them. Our work shows that in that period there was also this group of mosquitoes flying close to their feet, whose larvae ate the fungi associated with forests. During this period, these were basically conifers, different from current tropical forests. We can now glimpse an increasingly complete scenario of the flora and fauna at that time”, concludes the researcher.

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