Scientists map the genetic diversity of the world’s insects

Scientists map the genetic diversity of the world’s insects

Invertebrates are the largest group of animals on Earth, accounting for more than 90% of all living animal species. The vast majority of these invertebrates are insects, and more than a million insect species have been documented so far, but millions are believed to be yet to be discovered.

Insect species are diverse in tropical regions near the equator. But new mapping based on mitochondrial DNA from millions of insects has shown that the regions are richer in insects Genetic Diversity exists elsewhere.

In a new paper published in Nature CommunicationsScientists examined the DNA barcodes of more than two million insects and were surprised to find that genetic diversity was densest in hot, arid subtropical regions of the world.

“We found that there was this latitudinal gradient in genetic diversity that was different from that observed in vertebrates,” said study lead author Conor French, a PhD candidate in biology. The program is at the Graduate Center.

Learn more about Ph.D. program in biology

The Frenchman was referring to the latitudinal gradient of biodiversity, A widely observed pattern of many species living at the equator with a gradual decline in diversity moving towards the poles. “It is usually observed that the number of species is highest in the tropics,” French said, citing the Amazon rainforest. As an example where species diversity is high.

But he said this pattern was largely observed in vertebrates. “We don’t know enough about insect species populations because they are so diverse, it would take a huge effort to try to describe them all. So, we used genetics as a different measure of biodiversity to see if we could recover a similar pattern,” French said.

The biologists analyzed data from the Barcode of Life database, an open-source data portal containing millions of mitochondrial DNA barcodes of animals, plants, fungi and single-celled organisms from around the world. The data revealed that the genetic diversity of insects was higher in subtropical regions, rather than in tropical regions.

“We found that genetic diversity, at least the evenness of genetic diversity, is highest in the subtropics, not in the tropics,” French said. “So it is decreasing from the subtropics towards the tropics and the poles.”

Map numbers – insect migration
Global maps of observed and predicted insect genetic diversity. Observed (a, c, e) and expected (b, d, e) distributions of genetic diversity mean (GDM) (a, b), evenness (GDE) (c, d), and their composite (e, f) around the world. Brighter colors indicate higher values ​​of the genetic diversity measure. (Credit: Connor French and co-authors)

Two measures were used to report results: mean genetic diversity, which measures the average genetic diversity among species living in the same sample areas, and genetic diversity balance, which measures the uniformity of genetic diversity Among individuals sampled in an area.

The highest levels of genetic diversity are found In South America, in and around Argentina, and southwestern Australia. In the United States, hot spots They are found in the southwestern desert regions of Arizona and Texas and along the coast of New England. Less genetically diverse regions included parts of Scandinavia and the Arctic Circle in northern Canada.

Genetic diversity of insects has also been positively associated with climate stability. “We didn’t look at recent climate change, but we looked at climate change at a deeper time to investigate these patterns,” French said over 20,000 years. “In areas where there is greater climatic stability, we find more genetic diversity.”

But here, the researchers found one variant affecting genetic diversity that was completely unexpected. “Both arid and hot places have the highest genetic diversity,” he said, in contrast to more humid tropical regions where there is greater species diversity for many animal taxa.

“Having this relationship with hotter, drier regions tells us that genetic diversity is regulated by different ecological and evolutionary forces compared to species diversity,” French said, and unique genetic patterns may emerge because of insect survival strategies that have evolved in these harsher environments.

The study contains the first chapter of the French thesis. When asked if he had advice for other students hoping to publish their theses in similar journals, he said to plan ahead.

“The deployment process takes longer than you think,” French said. “If your goal is to have at least one chapter of your dissertation published before graduation, start the process as early as possible.” But, he said, “a manuscript doesn’t have to be perfect to be submitted.”

The study was funded by the National Science Foundation.

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