Scientists Reconstruct evolution of mosquito groups from the dinosaur era

In the last 15 years, two researchers have dedicated themselves to telling a story spanning more than 100 million years, practically only with a microscope, tweezers and a trained eye. Researchers Sarah Siqueira de Oliveira, currently Professor at the Federal University of Goiás (UFG), and Dalton de Souza Amorim, Professor in the Faculty of Philosophy, Sciences and Literatures of Ribeirão Preto, University of São Paulo (FFCLRP-USP), published the Most complete work to date on a subgroup of so-called mushroom mosquitoes.

The publication, with more than 100 pages and 107 illustrations, mostly in color, takes up an entire volume of the traditional bulletin of the American Museum of Natural History, which has been published by the North American Museum since 1881. The work also highlights the importance of continuous public funding of science, as it has been supported by several FAPESP projects since 2004.

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

Formed at the end of the Jurassic more than 145 million years ago and diversified to this day, mosquitoes of the Mycetophilidae family (whose name means “that like mushrooms” in Latin) have larvae that feed on fungi, wood ears, spores, and other parts of these organisms growing on rotting wood.

The researchers studied a subgroup called Leiinae that originated in the south of the supercontinent Gondwana, which later split into what is now South America, Africa and Antarctica, India, Australia and New Zealand.

The group that coexisted with the dinosaurs is one of five subfamilies and one of the most diverse within the Mycetophilidae, with more than 600 species described worldwide. There are at least 2,000 species that have not yet been described. The new work concluded that the subfamily includes 37 genera and has preserved some fossils in amber.

“There was no consensus in the scientific literature as to which groups belonged to this subfamily. We therefore decided to work on describing and naming species as well as understanding evolutionary relationships. It’s a very diverse and little-known group in the Neotropical region, ”says Oliveira, who carefully examined over a thousand specimens to complete the work.

The researcher began researching the evolution of insects while studying biology at the USP in Ribeirão Preto. The Biota Fapesp program started in 1999 was still in its infancy. Hence, a large amount of material was collected in order to be identified, an opportunity for Oliveira to study fungus mosquitoes. This first work received a scientific initiation grant from FAPESP between 2005 and 2006.

The research was part of a larger project “Geographical Limits and Causal Factors of Endemism in the Atlantic Forest in Diptera”, which was coordinated by Amorim, his supervisor, within the framework of Biota. The researcher also completed her master’s and doctoral studies as part of this project.

While the study was devoted to the identification of specimens collected in the Atlantic rainforest and the master’s project focused on a particularly diverse genus, the doctoral thesis aimed at a comprehensive analysis of the subfamily of the Leiinae – one of the least studied mosquito fungi up until then. The latter served as the basis for the current publication, which was expanded with the results of the postdoc, who was also supported by FAPESP.

“Insects are very old groups and many are spread around the world. Therefore, as a consultant, I usually choose topics in which students in groups with a few experts will become world leaders. We chose this important group because there was a knowledge gap there. And with this work, Sarah has taken the lead in the region, ”says Amorim.

Jurassic Park

In order to become an authority on a group of animals occurring worldwide, the specimens must be examined personally. Many specimens can be found in the collections of natural history museums, institutions whose task it is to preserve the largest and most diverse number of specimens of animals, vegetables and minerals.

Oliveira went to Australia for his doctorate 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 in the South African museums of Kwa-Zulu Natal (NMSA), Iziko (SAMC) and Pretoria (National Collection).

On another trip he studied collections from the USA and Canada. As a postdoctoral fellow, part of a Fapesp Research Internship fellowship abroad, Oliveira spent a period studying the collection of the Natural History Museum in London. She also used her stay in Europe to visit museum collections in France and Germany.

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

“An important part of this work was to bring specimens collected here back to Brazil that did not exist in Brazilian collections. They are very species-rich animals in the Neotropical region that originated in southern Gondwana and then spread to the rest of the world. Historically, however, researchers from countries in the northern hemisphere described many Brazilian species until the 1940s. Some of the collections have since been repatriated, ”says the researcher.

In some museums, it was part of the agreement for Oliveira to conduct his studies, organize mosquito collections, which were often kept for years without specialists to identify and organize the material.

“Many were single copies or with a few units, and they were very old. These factors often make genetic analysis impossible. However, studying the morphology with a microscope is enough to get 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 enables them to be included in the system, ”explains Amorim.

One of the principles of the work of taxonomists like Oliveira and Amorim is to find patterns of common characters in the morphology of animals – like wings, legs, and other parts that make them unique. In the study now published, 128 characters were used to distinguish between the sexes, such as structures of the head, chest, legs, wings, and genital organs.

To create a classification structure with all genera of the subfamily, the researchers added three new strains to the four existing ones. The study included 54 known fossil species, 12 of which are extinct genera, eight of which have preserved specimens in amber, a crystallized form of tree sap made famous in the 1993 film Jurassic Park.

The insect featured in the film actually 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 box office hit, but few people talk about where they lived, what they ate, what other beings lived around them. Our work shows that at this time there was also this group of mosquitoes that flew close to their feet, whose larvae ate the mushrooms associated with forests. During this time these were essentially conifers, as opposed to today’s tropical forests. We can now foresee an increasingly complete scenario of the flora and fauna of that time, ”concludes the researcher.

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