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Biologist discovers that female beetle pollinates orchid to feed offspring

Research reveals new nuances of interactions between plants and insects

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Playback When biologist Carlos Eduardo Nunes began his doctoral research, guided by professor Marlies Sazima,  He did not imagine that his work would change the concept that science had about the role of beetles related to woodworms or weevils in nature. According to the researcher from Unicamp's Institute of Biology (IB), his initial objective was to carry out basic research to identify the main pollinators of orchids native to Brazil and what role the fragrance or perfume of the flowers plays in this pollination process, mainly in relation to attraction of these pollinators, active participants in plant reproduction.

Nunes went much further. After a year of research, he identified weevils on a certain species of orchid and decided to investigate in more detail why they visit that flower. In science, weevils (family Curculionidae) are one of the largest families of insects and in many cases are considered pests, causing losses in agriculture. The importance of beetles as pollinators is already known for several groups of plants, including some of global economic importance, such as the oil palm. Until then, it was known that beetles visited flowers in search of food, mates or a place to leave eggs, pollinating the flowers by accident while carrying out these activities.

After observing and analyzing the behavior of these insects over six flowering seasons, the researcher discovered that the females of these “orchid weevils” actively pollinated the flowers they visited, that is, the beetles went to the vegetables and then pollinated them. them, laying their eggs in the flowers. One of the differences between this process and that carried out by bees is that, in this case, the weevils did not visit the flowers in search of food, as is the case with bees that pollinate in search of nectar or pollen, for example. This discovery is the first detailed record of active pollination by beetles (watch videos of this behavior).

Furthermore, the work directly changes the concept that biological sciences had of these animals in relation to the plants they use. The biologist discovered this active pollination process carried out by the insect when he observed that female beetles Montella manipulated masses of pollen from orchids of the Dichaea cogniauxiana, ensuring fruit production. They then laid eggs in the flower so that, after the insect larvae were born, they fed on the entire contents of the fruits developing on the plant. At this time, parasitoid wasps kill and feed on these larvae, making pollination by beetles advantageous for the plant, as the fruit seeds that are not consumed by the larvae end up completing the plant's reproduction process, and the beetle population is controlled. naturally.

Photo: Scarpa
Biologist Carlos Eduardo Nunes, author of the research

“If you just look at the plant and the beetle, the insect will always be bad for the plant, as the beetle larvae that complete their development end up consuming all the seed content of the fruits where they grow. But if you start to look at what is around, adding another actor in the process, like the wasp, there is a reversal of the situation and shows us that the interactions that exist in nature are much more complex than we imagine”, says Nunes, mentioning O article by researcher Brian Farrel on the development of agricultural practices by these animals.

The researcher highlights that this new function of beetles in nature had already been suggested in work developed by biologist Ludmila Mickeliunas in 2006 [1]. However, this pollination process carried out by weevils has not been described in detail. The study carried out by Mickeliunas observed that the plants visited by this type of insect showed a significant increase in fruit production. Nunes' work, published in the scientific journal Current Biology [2], detailed this entire process, describing the active pollination behavior of females and highlighting the main factors that lead beetles, with the interference of wasps, to benefit some species of orchids they use.

One of the challenges encountered during the research was the need to investigate the genetics of the beetles found, since, due to the enormous number of beetles existing in nature, it was necessary to determine which types were visiting the plants. “If God exists, he liked beetles, because what most exist in nature are different species of this insect” jokes the biologist.

Furthermore, when specifically analyzing the pollination process of beetles in relation to orchids of the species Dichaea cogniauxiana e Dichaea pendula, the researcher found that the same perfume that attracts bees to flowers also attracts these beetles to visit orchids [3]. For the biologist, these interactions are complex and need to be studied and analyzed increasingly by science. “There is a consensus in the science of pollination that everything in the flower is to attract the pollinator, such as the perfume, the color among other characteristics. However, these same factors end up attracting other herbivorous insects that can end up eating the flower and other parts of the plant” says Carlos Nunes.

Understanding these interactions in more detail is the next challenge of your work. For the biologist, biodiverse environments enable a series of interactions in which plant predators, when they suffer interference from other animals that feed on them, end up helping with their reproduction, continuing their natural cycle.

Furthermore, Nunes intends to deepen the study of the perfume exuded by flowers and plants, in addition to the repellents they produce to ward off their main “predators”. “Plants, over evolutionary time, have been selected to have characteristics that attract pollinators, but that also scare away herbivores. I believe that this is much more common than we imagine and may explain why flowers have so many chemical compounds” says the researcher, who intends, initially, to study the role of flower scent in pollination by bees [4].

Much more than placing “woodworm” beetles as active pollinators in nature, the work produced by researcher Carlos Nunes presents a new look at the interactions carried out by the various actors in nature. “There is a lot of encouragement to carry out research for agriculture that generates financial returns. However, when it comes to native plants, as they do not have industrial appeal, relatively little is researched,” he states. For the biologist, researching how flowers, through chemical compounds, exude perfumes to attract pollinators or smells to repel herbivores, is the first step towards discovering this new world of interactions, increasingly complex, existing in fauna and flora and important for the cycles of nature.

 


 

[1] Mickeliunas L, Pansarin ER, Sazima M (2006) Floral biology, melitophilia and influence of Curculionidae beetles on the reproductive success of Grobya amherstiae Lindl. (Orchidaceae: Cyrtopodiinae). Rev Bras Botânica 29:251–258.

[2] Nunes CEP, Maruyama PK, Azevedo-Silva M, Sazima M (2018) Parasitoids Turn Herbivores into Mutualists in a Nursery System Involving Active Pollination. Current Biology, 28: 980–986.

[3] Nunes CEP, Peñaflor MFG V., Bento JMS, et al (2016) The dilemma of being a fragrant flower: the major floral volatile attracts pollinators and florivores in the euglossine-pollinated orchid Dichaea pendula. Oecologia 182:933–946. doi: 10.1007/s00442-016-3703-5

[4] Nunes CEP, Wolowski M, Pansarin ER, et al (2017) More than euglossines: the diverse pollinators and floral scents of Zygopetalinae orchids. The Science of Nature 104:92. doi: 10.1007/s00114-017-1511-3

 

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Audio description: In a close-up and frontal image, a black, rounded beetle in the center of the image, on a yellow flower petal, with the flower extending across the entire area of ​​the photo. Image 1 of 1.

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