Why rats would win Australian survivor

September 07, 2020

Australian rodents skulls all correspond to one simple, size-dependent shape that is more than ten million years old but it turns out this lack of change is the secret behind their survivor reputation.

A new study, co-led by scientists from Flinders University and The University of Queensland, has revealed that the skulls of rodents resemble each other in any given size, meaning little adaptation seems to be necessary for a rodent to survive in a variety of habitats.

Flinders University Associate Professor Vera Weisbecker, who supervised the study says everyone knows rodents all look similar, but researchers expected far more variety in the details of their skull shape when compared to what was found.

"It seems intuitive that a group of animals that displays a wide variety of shapes should be more successful in evolution. However, Australian rodents demonstrate that shape diversity doesn't always mean evolutionary success. So it really does show if the skull ain't broke, don't fix it."

Dr Ariel Marcy, from The University of Queensland, says rodents first entered Australia around four million years ago, and quickly adapted to the diversity of habitats available on our continent.

"Because well-adapted skulls are key to the survival of mammals, we expected to find a lot of locally adapted skull shapes."

"What we found was the opposite of what we expected: there was low variation in the skull shape of rodents, and body size explained most of it."

"Native rodents just scale from being a small 'mouse' shape to being a bigger 'rat' shape!" Dr Marcy said.

"And this relationship between skull shape and size is at least ten million years old, because invasive rodents - like the house mouse and Norway rat - share this pattern, too."

To understand the patterns of adaptation they expected to see, the team scanned hundreds of rodent skulls of 38 species from museums using 3D surface scanners, and analysed their shape using a statistical procedure called geometric morphometrics.

The researchers think this astonishing conservatism of shape may have to do with the very successful specialization of rodent jaws, allowing their skulls to be a true multi-purpose tool.

"Rodent skulls and jaws have a complicated yet highly versatile arrangement that seems to work well in a multitude of conditions. We think that this discourages evolutionary change. We saw unusual skull shapes only in extreme cases of ecological adaptation, for example in the water mouse or rakali which is a very unusual meat-eating predatory rodent."

Dr Weisbecker notes that the results make an important point in one of the biggest questions in evolutionary biology - why some groups of animals are more diverse than others.
Background info

The research team includes researchers from the University of Queensland, the University of Sheffield, the University of Adelaide, Museums Victoria, Queensland University of Technology, and Flinders University with funding from the Australian Research Council.

Flinders University

Related Rodents Articles from Brightsurf:

The brain can induce diabetes remission in rodents, but how?
In rodents with type 2 diabetes, a single surgical injection of a protein called fibroblast growth factor 1 can restore blood sugar levels to normal for weeks or months.

Why rats would win Australian survivor
Australian rodents skulls all correspond to one simple, size-dependent shape that is more than ten million years old but it turns out this lack of change is the secret behind their survivor reputation.

Mathematical model could lead to better treatment for diabetes
MIT researchers have developed a mathematical model that can predict the behavior of glucose-responsive insulin in humans and in rodents.

Mechanism connects early binge drinking to adult behaviors
Intermittent exposure to high levels of alcohol in adolescent animals leads to increased levels of microRNA-137 in the brains of adults.

Natural loss of foot muscle in rodents shares mechanisms often associated with disease and injury
New insight on how the natural loss of foot muscles occurred in rodents and other species during their evolution has been published today in the open-access journal eLife.

U of M researchers discover a new mechanism that could counteract obesity
Obesity rates worldwide have nearly tripled since 1975. Now, new research from the University of Minnesota Medical School has discovered, in rodents, critical mutations in molecules implicated in obesity, which may help inform the development of new anti-obesity therapies.

Snake fang-like patch quickly delivers liquid medicines in rodents
Scientists have created a microneedle patch based on the fangs of a snake that can deliver therapeutic liquids and a vaccine through the skin of rodents in under 15 seconds.

Social isolation stresses rodents
The traditional method of housing mice and rats alone increases stress and worsens epilepsy, according to a new study published in eNeuro.

Predators' fear of humans ripples through wildlife communities, emboldening rodents
Giving credence to the saying, 'While the cat's away, the mice will play,' a new study indicates that pumas and medium-sized carnivores lie low when they sense the presence of humans, which frees up the landscape for rodents to forage more brazenly.

Train the brain to form good habits through repetition
You can hack your brain to form good habits -- like going to the gym and eating healthily -- simply by repeating actions until they stick, according to new psychological research involving the University of Warwick.

Read More: Rodents News and Rodents Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.