What is the origin of bees? – 10/18/2023 – Science

Around 120 million years ago, at the beginning of the Cretaceous period, groups of dinosaurs still walked the Earth when the first bees appeared in present-day South America and Africa, then connected as part of the supercontinent Gondwana. “The common ancestor of bees probably arose amid the drier climate that this region had. To date, the majority of the more than 20 thousand species already cataloged prefer drier areas, where they are more diverse”, said biologist Eduardo Almeida, from Ribeirão Preto campus of USP (University of São Paulo), while preparing to present these results at a workshop on bee evolution in the city of Portal, Arizona, United States, in mid-August.

Alongside his German colleague Silas Bossert, from Washington State University, he led the study published in August in the scientific journal Current Biology, which clarified this picture outlined in previous studies. To locate in time and space the evolutionary process of the planet’s main pollinators, the group analyzed DNA sequences from different parts of the genome of 216 bee species from all seven families (Andrenidae, Apidae, Colletidae, Halictidae, Megachilidae, Melittidae It is Stenotritidae) and the 28 subfamilies known today.

The samples came from the five continents where bees live (all except Antarctica), which was possible thanks to data and specimens deposited in research museums — Almeida is curator of the Prof. entomological collection. JMF Camargo, which houses hundreds of thousands of bee specimens.

The researchers then compared genetic age estimates and data on the geographic distribution of these species with information from 220 fossils and the locations where they were collected. All this information allowed the group to trace the genealogical tree (phylogeny) of bees, estimating the evolutionary kinship relationships between the main lineages and the ages of the evolutionary events. The result is a timeline that indicates where and when the first bees appeared and how the groups divided, diversified colors, shapes, behaviors and modes of organization, and dispersed across the planet over time, following the relocation of continents. .

The occupation of the continents

According to the results of the Ribeirão Preto group, from the moment the common ancestor of bees appeared, around 124 million years ago, a continuous process of diversification was influenced by the configuration of the continents at the time, the rise and fall of the ocean level and changes in climate that occurred in different geological periods.

“The separation of the supercontinent led to a change in the configuration of how bees were distributed around the world”, says Almeida. The data suggest that, of the seven current families, only Melittidae did not yet exist around 100 million years ago in the region today corresponding to South America.

Perhaps this is why bees were not greatly affected by the fall of the asteroid believed to be responsible for the mass extinction of dinosaurs, in the Gulf of Mexico, around 60 million years ago. “They were already spread across the planet, in a distribution close to the current one”, ponders Almeida.

He recalls that, from this period onwards, some tropical environments began to expand to higher latitudes, which allowed groups living in tropical and subtropical regions in the Southern Hemisphere to advance towards North America, Europe, Asia and northern Europe. Africa.

Groups of bees probably arrived in Australia between 70 and 35 million years ago, with the first ones originating in South America and taking a route through Antarctica, which provided the southern link between the two continents and had a milder climate. than the current one. Some time later, other bees that were already on the Asian continent would also have colonized Australia. In India, they must have arrived around 50 million years ago, after the territory of the current Indian country, which had broken away from Gondwana before the origin of bees, collided with the Asian continent and encountered the local fauna.

The appearance of the ancestral bee is still unknown: was it big or small, did it live in societies organized in hives or was it solitary? Almeida ventures a guess: it would probably be a solitary bee, since today 85% of species have this type of habit, with their members living in individual burrows. And, like most solitary birds, it would build nests on the ground. Almeida has also been investigating ways to reconstruct the ancestral morphology of these insects.

The academic grandfather, the wasps and the flowers

The proposal that bees arose in western Gondwana, which included South America and Africa, is not new. It was suggested by the North American entomologist Charles Michener (1918-2015) in 1979 in an article published in the magazine Annals of the Missouri Botanical Garden.

Michener, Almeida’s academic “grandfather”, is a reference in the study of the evolution of bees and spent a year in Brazil in 1956, working with the Brazilian entomologist Jesus Santiago Moure (1912-2010), known as Father Moure, at UFPR in Curitiba. “Forty years later, advances in genetic and computational analyses, in addition to the discovery of many bee fossils, allowed us to bring more evidence and new data to his hypothesis”, observes the researcher from Ribeirão Preto.

Biologist Vera Lucia Imperatriz Fonseca, from USP’s São Paulo campus, who did not participate in the study, notes that the research is the most comprehensive bee phylogeny carried out to date. “We used to study the bees in our backyard. Today we can study the bees of the world”, she says, highlighting the importance of preserving and expanding the country’s insect collections, including bees, so that this type of research can be expanded.

“The association between bees and flowers over millions of years is another point that the work helps us to think about”, says biologist Guilherme Cunha Ribeiro, from the Federal University of ABC (UFABC), who also did not participate in the study. In an article published in 2022 in the journal Cretaceous Research, Ribeiro and colleagues describe in the family Crabronidae a new species of extinct wasp, named Exallopterus spectabilis, whose fossil was located in the Crato formation, in Nova Olinda, Ceará. Its age has been estimated to be between 125 and 115 million years.

“We argue that if the family Crabronidaeconsidered by some studies to be the sister of bees, already existed in this interval, so bees would also have to exist”, says Ribeiro. As no bee fossils have yet been found in the region, despite the great abundance of insects already collected, he suggests that one explanation may be that they diversified further south in Gondwana.

Flowering plants, or angiosperms, date back to the early Cretaceous (about 145 million years ago). Before bees, there were other insects, including wasps, which fed on the nectar and pollen of flowers and, consequently, carried out their pollination. “Bees took on this leading role”, says the UFABC researcher.

Almeida explains that, at some point, carnivorous wasps became vegetarian, started to feed on pollen and, after that, bees appeared. “They became dependent on flowers and the main group responsible for pollination. The two organisms have a parallel history: bees had to be where the flowers were.” Therefore, one of the conclusions of the work coordinated by him is that the rich biodiversity of plants in South America is related to the fact that it is the continent where bees have been present for the longest time.

And if they took millions of years to establish, adapt and diversify, any drastic change in a short space of time represents a great risk. “If climate change radically transforms environments, we don’t know if they will be able to adapt so quickly”, warns Almeida.

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Projects

1. Phylogenomic systematics, comparative morphology and biogeography of bees (Hymenoptera: Anthophila) (nº 18/09666-5); Research Grant Type ‒ Regular; Responsible researcher Eduardo Andrade Botelho de Almeida (USP); Investment R$ 144,943.60.
2. The paleoentomofauna of the Crato formation (lower Cretaceous; Araripe basin): systematics and paleoecology (nº 20/02844-5); Research Grant Type ‒ Regular; Responsible researcher Guilherme Cunha Ribeiro (UFABC); Investment R$63,301.40.

Scientific articles

ALMEIDA, EAB et al. The evolutionary history of bees in time and space. Current Biology. v. 33. p. 1-14. 21 Aug. 2023.
ROSA, BB et. al. The first crabronid wasps (Hymenoptera, Support) from the Crato formation (Northeastern Brazil) and implications for the evolution of apoid wasps and bees during the Early Cretaceous. Cretaceous Research, vol. 137, 105248. set. 2022.