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Sticks insects survive one million years without sex | Sticks insects survive one million years without sex |
(about 4 hours later) | |
By Ella Davies Reporter, BBC Nature | By Ella Davies Reporter, BBC Nature |
Stick insects have lived for one million years without sex, genetic research has revealed. | Stick insects have lived for one million years without sex, genetic research has revealed. |
Scientists in Canada investigated the DNA of Timema stick insects, which live in shrubland around the west coast of the US. | Scientists in Canada investigated the DNA of Timema stick insects, which live in shrubland around the west coast of the US. |
They traced the ancient lineages of two species to reveal the insects' lengthy history of asexual reproduction. | They traced the ancient lineages of two species to reveal the insects' lengthy history of asexual reproduction. |
The discovery could help researchers understand how life without sex is possible. | The discovery could help researchers understand how life without sex is possible. |
Scientists from Simon Fraser University, Canada, published their results in the journal Current Biology. | Scientists from Simon Fraser University, Canada, published their results in the journal Current Biology. |
Certain species of Timema stick insects were known to reproduce asexually, with females producing young in "virgin births" without the need for egg fertilisation by males. | Certain species of Timema stick insects were known to reproduce asexually, with females producing young in "virgin births" without the need for egg fertilisation by males. |
The insects instead produce genetic clones of themselves. | The insects instead produce genetic clones of themselves. |
Dr Tanja Schwander and her team set out to test how old these species were, and therefore to find out how long they had reproduced in this way. | Dr Tanja Schwander and her team set out to test how old these species were, and therefore to find out how long they had reproduced in this way. |
By analysing the DNA of the insects, scientists were able to trace back their lineages to identify when they became a distinct species. | By analysing the DNA of the insects, scientists were able to trace back their lineages to identify when they became a distinct species. |
The team discovered that five of the asexual stick insects were "ancient", dating back more than 500,000 years. Two of them were even older. | The team discovered that five of the asexual stick insects were "ancient", dating back more than 500,000 years. Two of them were even older. |
"All the evidence points to Timema tahoe and Timema genevievae having persisted for over one million years without sex," Dr Schwander told BBC Nature. | |
"Our research adds to the growing amount of evidence that asexuality does not always result in the rapid extinction of a lineage," she said. | "Our research adds to the growing amount of evidence that asexuality does not always result in the rapid extinction of a lineage," she said. |
In the past, asexual reproduction has been associated with "evolutionary dead ends" because the lineages of organisms studied were often short-lived. | In the past, asexual reproduction has been associated with "evolutionary dead ends" because the lineages of organisms studied were often short-lived. |
In more recent studies, tiny invertebrates called bdelloid rotifers and darwinulid ostracods were described as long-established asexuals by scientists investigating fossil records. | |
But there has been ongoing controversy surrounding these ancient asexuals. Further study suggested that asexuality was, in some cases, likely to have been a recent adaptation. | |
Asexual survival | Asexual survival |
Dr Schwander and her team's genetic analysis confirmed that their stick insects have a long female-only history. | |
"Timema are indeed the oldest insects for which there is good evidence that they have been asexual for long periods of time," said Dr Schwander. | "Timema are indeed the oldest insects for which there is good evidence that they have been asexual for long periods of time," said Dr Schwander. |
Comparing sexual and asexual species of stick insect could teach scientists more about how organisms survive without sex. | Comparing sexual and asexual species of stick insect could teach scientists more about how organisms survive without sex. |
Asexuality does bring certain benefits, including rapid population growth. But the repeated cloning of genes through generations is thought to have significant negative consequences too. | Asexuality does bring certain benefits, including rapid population growth. But the repeated cloning of genes through generations is thought to have significant negative consequences too. |
This replication means that species are less able to adapt to new environments through "shuffling and tweaking" of genes. | This replication means that species are less able to adapt to new environments through "shuffling and tweaking" of genes. |
Dr Schwander said: "Why Timema asexuals have been able to persist for so long despite all the predicted negative consequences of asexuality is the focus of ongoing studies." | Dr Schwander said: "Why Timema asexuals have been able to persist for so long despite all the predicted negative consequences of asexuality is the focus of ongoing studies." |