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Komodo dragon

The Komodo dragon, which weighs on average some 70 kilograms, is an example of an island species that evolved outsize proportions. Credit: Alamy

Evolution

Animals around the world follow the ‘island rule’ to a curious fate

Small animals that move to islands tend to evolve into giants, but big animals that do the same shrink.

An analysis of more than 1,000 species shows that birds, mammals and reptiles on islands tend to be either miniature or gigantic versions of their mainland counterparts — evidence that an evolutionary tenet called the ‘island rule’ applies to a wide variety of vertebrates.

Big mainland animals often evolve smaller bodies on islands, whereas small mainland species become larger. A prominent example is the island-dwelling Komodo dragon (Varanus komodoensis), which is the world’s largest lizard and can exceed 150 kilograms.

Ana Benítez-López at the Doňana Biological Station in Seville, Spain, and her colleagues set out to settle the debate about whether the dragon and other species are mere flukes or part of a broader evolutionary pattern. The team gathered data from multiple studies to examine 1,166 island-dwelling species and 886 of their mainland counterparts. In a departure from some previous studies, the researchers drew data from diverse sources, such as museum specimens and studies unrelated to the island rule.

The authors found widespread evidence for the island rule around the world. Shifts in body size were most extreme for mammals and reptiles on smaller, more remote islands.

More Research Highlights...

Satellite image of broken iceberg B-44.

Dark water borders chunks of iceberg broken off a West Antarctica glacier. The melting of the region’s ice sheet could allow the bedrock to rise, sloughing water into the ocean. Credit: NASA

Climate change

Antarctic rocks on the rebound could raise sea level much more than expected

When the ice covering the west of the continent disappears, the bedrock could rise up and shove extra water into the ocean.
Monteverde Cloud Forest Preserve, Costa Rica

Mist wafts through the trees at the Monteverde Cloud Forest Biological Preserve in Costa Rica. Cloud forests around the world are threatened by development, wood collection and climate change. Credit: Stefano Paterna/Alamy

Conservation biology

Forests that float in the clouds are drifting away

Tropical cloud forests are safe havens for a vast range of creatures and plants, but they are under siege around the globe.
Illustration of a brown dwarf

A rapidly spinning brown dwarf (pictured, artist’s impression) tends to have narrow atmospheric bands; the faster the spin, the thinner the bands. Credit: NASA/JPL-Caltech

Astronomy and astrophysics

Dim stars that have failed at fusion are masters of spin

Three brown dwarfs whirl on their axes at a dizzying rate that might be close to the celestial speed limit for these bodies.
Aerial photograph of beef cattle standing at the Texana Feeders feedlot in Floresville, Texas

Large-scale facilities such as this feedlot in Floresville, Texas, help to meet the global appetite for beef and other red meat, which remains strong despite the growing consumption of chicken and fish. Credit: Daniel Acker/Bloomberg/Getty

Agriculture

Meat lovers worldwide pay climate little heed

People are eating more poultry and fish — but they’re not giving up their hamburgers.
Midshipmen at dining table eat in formation, CIRCA 1900

Midshipmen in the United States in around 1900. A study found that body-mass index, a gauge of obesity, has increased with the generations during the twentieth century. Credit: Buyenlarge/Getty

Metabolism

A century of US data documents obesity’s racially skewed rise

An analysis also finds that obesity is common at a much younger age among people born in the early 1980s than those born in the late 1950s.
Auroras on Jupiter

Jupiter’s aurora glows blue in this composite image. A newly detected radio signal might be the signature of a similar aurora on a planet in another solar system. Credit: NASA/ESA/J. Nichols, Univ. Leicester

Astronomy and astrophysics

Wiggly signal hints of an aurora on a planet far from the Solar System

A vast radio observatory on Earth detects signals similar to those generated by the aurora on Jupiter.
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