Life organization: species cluster in hotspots, gradually spread outwards

https://phys.org/news/2025-06-life-oceans-savannas.html
A simple rule that seems to govern how
life is organized on Earth is described
in a new study published in Nature
Ecology & Evolution.
The research team, led by Umeå University
and involving the University of Reading,
believe this rule helps explain why
species are spread the way they are across
the planet. The discovery will help to
understand life on Earth—including how
ecosystems respond to global
environmental changes.
The rule is simple: in every region on
Earth, most species cluster together in
small "hotspot" areas, then gradually
spread outward with fewer and fewer
species able to survive farther away
from these hotspots.
Rubén Bernardo-Madrid, lead author and
researcher at Umeå University (Sweden),
said, "In every bioregion, there is
always a core area where most species
live. From that core, species expand
into surrounding areas, but only a
subset manages to persist. It seems
these cores provide optimal conditions
for species survival and diversification,
acting as a source from which biodiversity
radiates outward."
...
Given the vast differences in life
strategies—some species fly, others crawl,
swim, or remain rooted—and the contrasting
environmental and historical backgrounds of
each bioregion, the researchers expected
that species distribution would vary
widely across bioregions. Surprisingly,
they found the same pattern everywhere.
The pattern points to a general process
known as environmental filtering.
Environmental filtering has long been
considered a key theoretical principle in
ecology for explaining species distribution
on Earth.
...
Professor Manuela González-Suárez, co-author
of the study at the University of Reading,
said, "It doesn't matter whether the limiting
factor is heat, cold, drought, or salinity.
The result is always the same: only species
able to tolerate local conditions establish
and persist, creating a predictable
distribution of life on Earth."
The existence of a universal organizing
mechanism has profound implications for our
understanding of life on Earth. Joaquín
Calatayud, co-author from the Rey Juan Carlos
University (Spain), said, "This pattern
suggests that life on Earth may be, to some
extent, predictable."
...