How do asexual ants maintain genetic diversity?

It’s commonly accepted wisdom that genetic diversity is vital for the survival of a species, and sexual reproduction helps maintain this diversity. But what happens when a species doesn’t reproduce sexually? Usually, it’s a recipe for low genetic diversity and a ticket to extinction. Yet, in the realm of clonal raider ants, this doesn’t seem to be the case. Why so?

A recent study has shed light on this intriguing mystery, a story of survival in the face of biological norms, courtesy of researchers from Rockefeller University.

Genetic diversity of clonal raider ants

To give you some context, the clonal raider ant is a blind, queenless creature found in tropical settings around the globe.

The species is originally native to Bangladesh and reproduces through parthenogenesis. This type of asexual reproduction results in offspring that inherit two sets of genetically identical chromosomes from the mother – in other words, clone daughters.

Now, you’d be forgiven for thinking that this should lead to a drastic loss in genetic diversity and, over time, species collapse. But these resilient little creatures are confounding expectations and surviving – and flourishing – quite well.

Kip Lacy, a graduate fellow in the Laboratory of Social Evolution and Behavior, and his mentor Daniel Kronauer are the faces behind this discovery. They found out that the clonal raider ant doesn’t leave gene transmission to chance.

Instead, it ensures that offspring inherit two different versions of its complete genome, thus preserving the genetic diversity existing in the ancient founder of each clonal line.

Diving deeper into the mystery

Under normal circumstances, chromosomes mix randomly during meiosis, a kind of cell division resulting in sperm and egg cells. This, however, doesn’t seem to be the case with our ant friends.

Lacy and Kronauer highlight that asexual creatures face two significant challenges at the cellular level. Firstly, they need to produce diploid genomes (containing two sets of chromosomes) to pass onto their offspring.

Secondly, this offspring must have a genetic makeup compatible with development and reproduction, something that many asexual species, burdened with two identical chromosomal sets, lack.

“We think we’ve discovered how clonal raider ants are avoiding the loss of genetic diversity that otherwise routinely results from parthenogenesis,” said Lacy. “Maybe this diversity enables the survival of the species.”

How the ant maintains genetic diversity

Here’s where the clonal raider ant, a parthenogenetic creature, breaks away from the mold. Contrary to what you’d expect, it manages to retain significant diversity during each reproductive cycle. How does it pull off such a feat? It’s all down to the process of genetic recombination.

In the clonal raider ant, recombination events lead to new gene copy combinations. Yet, rather than being shuffled randomly, the recombined chromosomes always inherited together.

“This co-inheritance could explain how this species continues to survive. In clonal raider ants, it’s 800% more likely to occur than would be expected from a random roll of the genetic dice,” noted Lacy.

Novel strategy for genetic diversity retention

This, as Kronauer pointed out, is a unique strategy for retaining genetic diversity. It basically shows that there are more ways of dodging random genetic inheritance than we previously thought.

Notably, this system of unselfish inheritance, where no gene has an advantage and all gene copies are co-inherited, is a new and unexplored concept in the biological sciences.

Whether this method applies to other organisms, including sexually reproducing species, remains to be determined.

Studying unusual reproductive biology

This research serves as a powerful reminder of why we must explore species with unique reproductive biology.

“If we hadn’t studied these asexual ants, we might never have learned about this mode of reproduction,” noted Lacy.

And who knows? Their further exploration of these fascinating creatures might well rewrite our understanding of genetics and survival in the natural world.

So, next time you see an ant, take a moment to appreciate the astonishing genetic diversity and survival strategies that these tiny creatures carry within. Their tiny bodies bear testament to the wonders of nature and its never-ending capacity to surprise us.

The study is published in the journal Nature Ecology & Evolution.

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