Resurrection of the Island Rule: Human-Driven Extinctions Have Obscured a Basic Evolutionary Pattern.

Area of Science:

• Evolutionary Biology
• Island Biogeography
• Paleontology

Background:

• Islands often host unique species, like dwarf elephants and giant rodents.
• The island rule proposes that mammalian body sizes converge to intermediate sizes on islands, a concept debated due to unusual island fauna.

Purpose of the Study:

• To analyze mammalian body size evolution on islands using a global dataset.
• To test the validity of the classical island rule with novel analytical methods.

Main Methods:

• Utilized an extensive global dataset of late Quaternary mammal species distributions and body sizes.
• Employed a novel analytical approach to investigate body size evolution patterns on islands.

Main Results:

• The study found strong empirical support for the island rule.
• Evidence for the island rule was significantly strengthened when extinct late Quaternary species were included, particularly the dwarfing of large mammals.
• Human-driven species loss on islands did not obscure this fundamental evolutionary pattern.

Conclusions:

• Island evolution exhibits distinct patterns compared to mainland evolution.
• The island rule is a robust evolutionary phenomenon, confirmed by comprehensive data including extinct species.
• Human impacts can obscure, but do not negate, fundamental evolutionary processes like the island rule.