The ancestors of the trapdoor spider Moggridgea rainbowi may have survived an ocean journey from Africa to Australia, a new study concludes.

Moggridgea rainbowi spiders can be found on Kangaroo Island. It sits off the south coast of Australia. These trapdoor spiders build a silk-lined burrow in the ground with a secure-fitting lid, notes Sophie Harrison. She is a biologist in Australia at the University of Adelaide. The burrow and trapdoor provide these spiders with shelter and protection. It also offers them an out-of-sight spot from which to await approaching prey. And it means that the spiders don’t really need to travel more than a few meters (yards) over the course of a lifetime.

To figure out which story was most likely true, Harrison and her colleagues looked at the spider’s genes. They turned to six genes that have been well-studied by biologists seeking to understand links between spiders. As species evolve, their genes change. And scientists can look at the differences between genes to determine how closely related certain species are. They even can figure out when the most recent common ancestor of two species lived.

Harrison’s group looked at those genes in seven M. rainbowi specimens from Kangaroo Island. They also looked at five species of Moggridgea spiders from South Africa. Finally, they analyzed the genes of seven species of southwestern Australia spiders. They belonged to the closely related genus Bertmainius.

M. rainbowi was most closely related to the African spiders, the genes showed. The Australian and African spiders split off from a common ancestor some 2 million to 16 million years ago, the data indicate. Australia’s Bertmainius spiders are more distant relatives.

The Australian spiders diverged from their African cousins long after Gondwana split up. This also was long before either the ancestors of Australia’s aboriginal people or later Europeans showed up on the Australian continent. It seems impossible that a colony of spiders survived a journey of 10,000 kilometers (6,200 miles) across the Indian Ocean. However, that is the most likely explanation of how trapdoor spiders got to Kangaroo Island, the researchers now say.

Trapdoor spiders may be well-suited to ocean travel, Harrison’s team contends. If a large swatch of land washes into the sea, laden with arachnids, the spiders may be able to hide out in their nests throughout the journey. Plus, they don’t need a lot of food. And they can resist drowning. They can even “hold their breath” and survive on stored oxygen during periods of temporary flooding, the researchers note.

https://www.sciencenewsforstudents.org/article/become-australians-these-spiders-crossed-ocean

PermeateFree said:

The ancestors of the trapdoor spider Moggridgea rainbowi may have survived an ocean journey from Africa to Australia, a new study concludes.

Moggridgea rainbowi spiders can be found on Kangaroo Island. It sits off the south coast of Australia. These trapdoor spiders build a silk-lined burrow in the ground with a secure-fitting lid, notes Sophie Harrison. She is a biologist in Australia at the University of Adelaide. The burrow and trapdoor provide these spiders with shelter and protection. It also offers them an out-of-sight spot from which to await approaching prey. And it means that the spiders don’t really need to travel more than a few meters (yards) over the course of a lifetime.

To figure out which story was most likely true, Harrison and her colleagues looked at the spider’s genes. They turned to six genes that have been well-studied by biologists seeking to understand links between spiders. As species evolve, their genes change. And scientists can look at the differences between genes to determine how closely related certain species are. They even can figure out when the most recent common ancestor of two species lived.

Harrison’s group looked at those genes in seven M. rainbowi specimens from Kangaroo Island. They also looked at five species of Moggridgea spiders from South Africa. Finally, they analyzed the genes of seven species of southwestern Australia spiders. They belonged to the closely related genus Bertmainius.

M. rainbowi was most closely related to the African spiders, the genes showed. The Australian and African spiders split off from a common ancestor some 2 million to 16 million years ago, the data indicate. Australia’s Bertmainius spiders are more distant relatives.

The Australian spiders diverged from their African cousins long after Gondwana split up. This also was long before either the ancestors of Australia’s aboriginal people or later Europeans showed up on the Australian continent. It seems impossible that a colony of spiders survived a journey of 10,000 kilometers (6,200 miles) across the Indian Ocean. However, that is the most likely explanation of how trapdoor spiders got to Kangaroo Island, the researchers now say.

Trapdoor spiders may be well-suited to ocean travel, Harrison’s team contends. If a large swatch of land washes into the sea, laden with arachnids, the spiders may be able to hide out in their nests throughout the journey. Plus, they don’t need a lot of food. And they can resist drowning. They can even “hold their breath” and survive on stored oxygen during periods of temporary flooding, the researchers note.

https://www.sciencenewsforstudents.org/article/become-australians-these-spiders-crossed-ocean

The spiders live in short burrows, approximately 6cm deep. Young spiders live with their mothers before building their own burrows nearby.

All known Western River populations were destroyed during the 2019-2020 Australian bushfires, one of which burned a third of Kangaroo Island. As of July 2020 none have been seen.[1

Stay away from that trapdoor.

PermeateFree said:

PermeateFree said:

The ancestors of the trapdoor spider Moggridgea rainbowi may have survived an ocean journey from Africa to Australia, a new study concludes.

Moggridgea rainbowi spiders can be found on Kangaroo Island. It sits off the south coast of Australia. These trapdoor spiders build a silk-lined burrow in the ground with a secure-fitting lid, notes Sophie Harrison. She is a biologist in Australia at the University of Adelaide. The burrow and trapdoor provide these spiders with shelter and protection. It also offers them an out-of-sight spot from which to await approaching prey. And it means that the spiders don’t really need to travel more than a few meters (yards) over the course of a lifetime.

To figure out which story was most likely true, Harrison and her colleagues looked at the spider’s genes. They turned to six genes that have been well-studied by biologists seeking to understand links between spiders. As species evolve, their genes change. And scientists can look at the differences between genes to determine how closely related certain species are. They even can figure out when the most recent common ancestor of two species lived.

Harrison’s group looked at those genes in seven M. rainbowi specimens from Kangaroo Island. They also looked at five species of Moggridgea spiders from South Africa. Finally, they analyzed the genes of seven species of southwestern Australia spiders. They belonged to the closely related genus Bertmainius.

M. rainbowi was most closely related to the African spiders, the genes showed. The Australian and African spiders split off from a common ancestor some 2 million to 16 million years ago, the data indicate. Australia’s Bertmainius spiders are more distant relatives.

The Australian spiders diverged from their African cousins long after Gondwana split up. This also was long before either the ancestors of Australia’s aboriginal people or later Europeans showed up on the Australian continent. It seems impossible that a colony of spiders survived a journey of 10,000 kilometers (6,200 miles) across the Indian Ocean. However, that is the most likely explanation of how trapdoor spiders got to Kangaroo Island, the researchers now say.

Trapdoor spiders may be well-suited to ocean travel, Harrison’s team contends. If a large swatch of land washes into the sea, laden with arachnids, the spiders may be able to hide out in their nests throughout the journey. Plus, they don’t need a lot of food. And they can resist drowning. They can even “hold their breath” and survive on stored oxygen during periods of temporary flooding, the researchers note.

https://www.sciencenewsforstudents.org/article/become-australians-these-spiders-crossed-ocean

The spiders live in short burrows, approximately 6cm deep. Young spiders live with their mothers before building their own burrows nearby.

All known Western River populations were destroyed during the 2019-2020 Australian bushfires, one of which burned a third of Kangaroo Island. As of July 2020 none have been seen.

Interesting.

Thanks.

> They turned to six genes that have been well-studied by biologists seeking to understand links between spiders. As species evolve, their genes change. And scientists can look at the differences between genes to determine how closely related certain species are. They even can figure out when the most recent common ancestor of two species lived. Harrison’s group looked at those genes in seven M. rainbowi specimens from Kangaroo Island. They also looked at five species of Moggridgea spiders from South Africa. Finally, they analyzed the genes of seven species of southwestern Australia spiders.

(Sucks air through teeth). Six genes is borderline satisfactory for ancestry studies. One gene and two genes has long been known to be insufficient. Mostly, we go with full genome and thousands of genes.

Take human – neanderthal – denisovan ancestry and interbreeding for instance. Only a full genome could have given us the full picture. Or am I wrong.

Let’s take the spiders as an example. A spider arrived form South Africa. It needed to find a mate. So mated with spiders already here. Among results from that mating, some will more nearly resemble South African spiders and some will more nearly resemble pre-existing Australian spiders. Geographic isolation between mainland and Kangaroo Island species can then mask the interbreeding, possibly, if only a few genes are used in the comparison. It will certainly mask the interbreeding if only one or two genes are used for comparison.

But six? I don’t know.

mollwollfumble said:

> They turned to six genes that have been well-studied by biologists seeking to understand links between spiders. As species evolve, their genes change. And scientists can look at the differences between genes to determine how closely related certain species are. They even can figure out when the most recent common ancestor of two species lived. Harrison’s group looked at those genes in seven M. rainbowi specimens from Kangaroo Island. They also looked at five species of Moggridgea spiders from South Africa. Finally, they analyzed the genes of seven species of southwestern Australia spiders.

(Sucks air through teeth). Six genes is borderline satisfactory for ancestry studies. One gene and two genes has long been known to be insufficient. Mostly, we go with full genome and thousands of genes.

Take human – neanderthal – denisovan ancestry and interbreeding for instance. Only a full genome could have given us the full picture. Or am I wrong.

Let’s take the spiders as an example. A spider arrived form South Africa. It needed to find a mate. So mated with spiders already here. Among results from that mating, some will more nearly resemble South African spiders and some will more nearly resemble pre-existing Australian spiders. Geographic isolation between mainland and Kangaroo Island species can then mask the interbreeding, possibly, if only a few genes are used in the comparison. It will certainly mask the interbreeding if only one or two genes are used for comparison.

But six? I don’t know.

Unlikely to mate with a different species, more likely males and females came together. You are not dealing with a mixture of species with one being a small component like the Neanderthal, you are dealing with a species directly derived from the same ancestor, so would have a much stronger gene relationship.

PermeateFree said:

mollwollfumble said:

> They turned to six genes that have been well-studied by biologists seeking to understand links between spiders. As species evolve, their genes change. And scientists can look at the differences between genes to determine how closely related certain species are. They even can figure out when the most recent common ancestor of two species lived. Harrison’s group looked at those genes in seven M. rainbowi specimens from Kangaroo Island. They also looked at five species of Moggridgea spiders from South Africa. Finally, they analyzed the genes of seven species of southwestern Australia spiders.

(Sucks air through teeth). Six genes is borderline satisfactory for ancestry studies. One gene and two genes has long been known to be insufficient. Mostly, we go with full genome and thousands of genes.

Take human – neanderthal – denisovan ancestry and interbreeding for instance. Only a full genome could have given us the full picture. Or am I wrong.

Let’s take the spiders as an example. A spider arrived form South Africa. It needed to find a mate. So mated with spiders already here. Among results from that mating, some will more nearly resemble South African spiders and some will more nearly resemble pre-existing Australian spiders. Geographic isolation between mainland and Kangaroo Island species can then mask the interbreeding, possibly, if only a few genes are used in the comparison. It will certainly mask the interbreeding if only one or two genes are used for comparison.

But six? I don’t know.

Unlikely to mate with a different species, more likely males and females came together. You are not dealing with a mixture of species with one being a small component like the Neanderthal, you are dealing with a species directly derived from the same ancestor, so would have a much stronger gene relationship.

Yes, that seems reasonable. If just seems weird for a significant number of burrowing animals of different sexes to cross 9,000 km of open ocean on a raft. The date, 2 million to 16 million years ago, is too ancient to check for a genetic bottleneck.