https://phys.org/news/2024-01-theoretical-explanation-animals.html

The mystery behind why Alaskan horses,
cryptodiran turtles and island lizards
shrank over time may have been solved in
a new study.

The new theoretical research proposes
that animal size over time depends on
two key ecological factors: the intensity
of direct competition for resources
between species, and the risk of
extinction from the environment.

Using computer models simulating evolution,
the study, published in Communications
Biology, identifies why some species
gradually get smaller, as indicated by
fossil records.

Dr. Shovonlal Roy, an ecosystem modeler from
the University of Reading who led the
research, said, "Just like how we try to
adapt to hot or cold weather depending on
where we live, our research shows animal
size can get bigger or smaller over long
periods depending on the habitat or
environment.

"In places and times where there's lots of
competition between different species for
food and shelter, animal sizes often get
smaller as the species spread out and adapt
to the distribution of resources and
competitors. For example, small horses that
lived in Alaska during the Ice Age rapidly
shrank due to changes in the climate and
vegetation.

"Where direct competition is less, sizes
tend to get bigger, even though being really
big and few in number can make animals more
vulnerable to dying out—such as what happened
with the dinosaurs. Changes in ecological
factors help explain why fossil records shows
such confusing mixes of size evolution
patterns, with some lineages shrinking over
time and others growing."
....
However, fossil evidence shows remarkably
conflicting trends, with increased size in
some groups but decreased size in others.

Using computer models simulating evolution,
the study identified three distinct patterns
of body-size change emerging under different
conditions:

* Gradual size increase over time ...
* Size increase followed by extinctions ...
* Gradual size decrease over time ...

The paper is public

https://www.nature.com/articles/s42003-023-05375-z
Ecological determinants of Cope’s rule and its inverse

On 1/31/24 1:04 PM, Pro Plyd wrote:
>
> https://phys.org/news/2024-01-theoretical-explanation-animals.html
>
> The mystery behind why Alaskan horses,
> cryptodiran turtles and island lizards
> shrank over time may have been solved in
> a new study.
>
> The new theoretical research proposes
> that animal size over time depends on
> two key ecological factors: the intensity
> of direct competition for resources
> between species, and the risk of
> extinction from the environment.
>
> Using computer models simulating evolution,
> the study, published in Communications
> Biology, identifies why some species
> gradually get smaller, as indicated by
> fossil records.
>
> Dr. Shovonlal Roy, an ecosystem modeler from
> the University of Reading who led the
> research, said, "Just like how we try to
> adapt to hot or cold weather depending on
> where we live, our research shows animal
> size can get bigger or smaller over long
> periods depending on the habitat or
> environment.
>
> "In places and times where there's lots of
> competition between different species for
> food and shelter, animal sizes often get
> smaller as the species spread out and adapt
> to the distribution of resources and
> competitors. For example, small horses that
> lived in Alaska during the Ice Age rapidly
> shrank due to changes in the climate and
> vegetation.
>
> "Where direct competition is less, sizes
> tend to get bigger, even though being really
> big and few in number can make animals more
> vulnerable to dying out—such as what happened
> with the dinosaurs. Changes in ecological
> factors help explain why fossil records shows
> such confusing mixes of size evolution
> patterns, with some lineages shrinking over
> time and others growing."
> ...
> However, fossil evidence shows remarkably
> conflicting trends, with increased size in
> some groups but decreased size in others.
>
> Using computer models simulating evolution,
> the study identified three distinct patterns
> of body-size change emerging under different
> conditions:
>
> * Gradual size increase over time ...
> * Size increase followed by extinctions ...
> * Gradual size decrease over time ...
>
>
> The paper is public
>
> https://www.nature.com/articles/s42003-023-05375-z
> Ecological determinants of Cope’s rule and its inverse
>
A quick reading of this article (maybe too quick) leads me to wonder
about its applicability. Yes, some species tend to get bigger, others
smaller, and it's reasonable to wonder what drives this. The authors
recognize that there are lots of examples, but the paper discusses
nothing about how any of these specific cases relate to the model
presented. How to verify or falsify their approach?

All the authors have experience with mathematical modelling, but I would
have liked to see someone contributing to this paper have some
paleontological connection.