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As a result of their research, Juan Pablo Torretta, associate professor of the General Botany Department of the Faculty of Agronomy of the UBA (FAUBA), and his group found and described two new species within the group commonly known as “oil bees”. CalledMonoeca pulchella YMonoeca armata, and their gender,MonoecaIt was not documented in the country either. Although they pollinate flowers, like the typical honeybee, they are clearly differentiated because they collect oil from certain vegetables.
“In addition to pollen, oil bees receive oil as a reward for visiting and pollinating the flowers of various families of plants. These bees are distributed throughout the tropics, but they mainly live in the Neotropics; that is, in the tropical region of America. In Argentina there is a very widespread tribe called Tapinotaspidini, which includes a great variety of bees and to which the two species that we discovered in Misiones belong ”, commented Juan Pablo.
Torretta, who is also a Conicet associate researcher, has been carrying out his studies on bees for approximately 10 years, in collaboration with other professionals such as Arturo Roig Alsina, from the Argentine Museum of Natural Sciences, with whom he studies the taxonomy of these bees. Juan Pablo also collaborates with Sandra Aliscioni, a teacher at FAUBA. With it, he studies the anatomy of flowers in relation to oil secretion. The description of the new species was published in the scientific journal Journal of Melittology.
“In general, oil bees vary a lot in both shapes and sizes, but they are not rarities. Although they can have different colors and measure from 6 millimeters to 4 centimeters, when you see them you realize that they are bees. One particularity is that they have one or more modified legs to store the oil. In the specific case ofM. pulchella YM. armata, have the oil collection brushes on the inside of the four front legs, in the same position as the species of another important oil tribe: Centridini ”, explained the researcher.
Juan Pablo pointed out that this kind of bees use oil, which is very energetic, to feed their young and build nests. Instead of honey, to feed the larvae they make a mixture of oil and pollen. They also make nests with a mass of oil and sand or earth, unlike the honey bee, which makes the typical wax combs. On the other hand, as they have solitary habits, the oil plants make small nests, with few cells. “Some use pre-existing cavities; others locate their nests on the ground. Being made with oil, the nests are impervious to water. There are documented cases of larvae that survived floods for up to seven years and emerged naturally when the water receded. "
Oil bees make small nests on the ground. Since the mud with which they are built contains oil, they are impervious to water.
Torretta clarified that only certain groups of plants (families) produce the oil that these bees harvest. “The oil as a reward was a recent find. Only 50 years ago it was seen that there was a link between certain plants and these bees. The person who discovered and described it was Stefan Vogel, a German biologist who visited FAUBA and worked in our botanical garden ”.
“One of the quintessential oil families is called Malpighiaceae, in which oil as a floral reward is a primitive condition. Although the Malpigiaceae of the old continent do not produce oil, those of the Neotropics do. The oldest known interaction of this family is with oil bees of the Centridini tribe, possibly of the genusEpicharis, the most primitive of the tribe. A commercial example of a Malpigiaceae pollinated by these bees is acerola, highly valued in Brazil for its edible fruits, "said Torretta.
The researcher stressed that for a profitable interaction to take place between the oil plants and the bees that collect it, both must have special adaptations. “The oil-secreting structures (elaiophores) are variable. They can be epithelial (that is, the oil accumulates in blisters in the epidermis of plants) or trichomatic (which are like secretory hairs). Currently, intermediate elaiophores, part epithelial and part trichomatic, were found. On the other hand, the oil bees have modified, hard hairs, with which they break these structures and collect the oil when visiting the flowers. These results are published in the journal Plant Systematics and Evolution ”.
The teacher said that at present, he and his group are studying genderParatetrapedia, of which only three species had been cited in Argentina and now six are known. “Several species of oil bees arrive in the tropical part of our country, much more frequent in northern South America. The idea is to add them to our investigations. For 5 or 6 years we have carried out campaigns to Misiones, Formosa and Corrientes in search of these bees and we are collecting a large quantity of unknown specimens for our country, and even for science ”.
Another leg of Juan Pablo Torretta's work with Sandra Aliscioni is the study of the anatomy of Malpigiáceas flowers. “The stigmas differ in shape and position according to the genus of the plant to which they belong. Today, we are trying to understand if the different arrangements of these pieces are related to the size or shape of the bee that reaches the flower. At the same time, we want to know if this allows a more efficient pollination while the bee takes its oil reward ”.
Finally, Torretta said: “From my point of view as a researcher and botanist, the most interesting thing about my studies is the interaction between plants and insects. It is fascinating to see that, in reality, it is not that one of them changes and the other adapts; the two groups are constantly adapting ”.