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
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