In tomorrow’s New York Times I have an article about the origin of species–or rather, blocking the origin of species. The evolution of a new species can be a drawn out process, taking thousands or millions of years. First populations begin to diverge from each other. Later, those populations may become divided by significant reproductive barriers. Even after those populations have evolved into separate species, they may still be able to produce hybrids in the right conditions. In some cases, those hybrids may remain rare and the two species will remain intact. In other cases, the species may collapse back on each other.
The article looks at two animals in which speciation appears to be going in reverse. One is three-spined sticklebacks, which have evolved into two easily distinguished different species in 11,000 years in six separate lakes in Canada. (The papers are here and here.) In one lake, an introduced crayfish appears to be driving the two species into a single hybrid swarm.
The other example is Darwin’s finches on the Galapagos (paper here). The medium ground finch has, on some islands, diverged into two forms, one with a big beak and one with a small one. But where they have come into contact with humans, they are blurring back into a single spectrum of beaks. Hybrids with average size beaks appear to be thriving because they can eat rice and other foods left by humans.
As I mention in the article, Ole Seehausen, an expert on fish biodiversity, thinks these papers are hinting at a widespread pattern. In Current Biology (pdf here) he points out that much of the diversity on Earth consists of new species, rather than old ones. New species are fragile, and human activity may be able to drive them into hybrid swarms. Seehausen’s own work on cichlids in Africa suggests that pollution in Lake Victoria is making it hard for the fish to recognize mates of their own species.
It may seem odd to think of reverse speciation as a real threat to biodiversity. Knocking down a forest–that’s easy to picture. But if the sticklebacks do become completely mixed in Lake Enos, there will still be sticklebacks in Lake Enos. It’s just that where there were two species, one will be left. The real difficulty, I suspect, comes from thinking about biodiversity as an ongoing process. Even before humans, old species became extinct as new species gradually emerged. Now we are not just endangering old species but perhaps block new ones from evolving–cutting off biodiversity at both ends, in other words.
I find it interesting to ponder this research in the wake of the hominid-ape hybrid research I wrote about last week. Our ancestors diverged from the ancestors of chimpanzees roughly six million years ago–very roughly according to recent studies that suggest millions of years of gradual separation, perhaps even with some hybridization after the lineages split. Scientists can only look back at that split by looking at the genomes of humans and other apes. But sticklebacks and Darwin’s finches can offer some clues to that delicate process of parting ways.
Update: Apologies to residents of Vancouver Island (home of the studied sticklebacks), which I wrongly identified as Victoria Island.
Related Topics
Go Further
Animals
- These 'trash fish' are among Earth's most primitive animalsThese 'trash fish' are among Earth's most primitive animals
- These photos are works of art—and the artists are bugsThese photos are works of art—and the artists are bugs
- The epic migration of a 6-foot long, 200-pound catfishThe epic migration of a 6-foot long, 200-pound catfish
- Frans de Waal, biologist who studied animal emotion, dies at 75Frans de Waal, biologist who studied animal emotion, dies at 75
Environment
- Are synthetic diamonds really better for the planet? The answer isn't clear-cut.Are synthetic diamonds really better for the planet? The answer isn't clear-cut.
- This year's cherry blossom peak bloom was a warning signThis year's cherry blossom peak bloom was a warning sign
- The U.S. just announced an asbestos ban. What took so long?The U.S. just announced an asbestos ban. What took so long?
- The most dangerous job? Inside the world of underwater weldersThe most dangerous job? Inside the world of underwater welders
- The harrowing flight that wild whooping cranes make to surviveThe harrowing flight that wild whooping cranes make to survive
History & Culture
- Meet the powerful yokai that inspired the demon king in ‘Demon Slayer’Meet the powerful yokai that inspired the demon king in ‘Demon Slayer’
- A surprising must-wear for European monarchs? Weasels.A surprising must-wear for European monarchs? Weasels.
- Meet the woman who made Polaroid into a cultural iconMeet the woman who made Polaroid into a cultural icon
- Inside the observatory that birthed modern astrophysicsInside the observatory that birthed modern astrophysics
Science
- LED light treatments for skin are trendy—but do they actually work?LED light treatments for skin are trendy—but do they actually work?
- NASA smashed an asteroid. The debris could hit Mars.NASA smashed an asteroid. The debris could hit Mars.
- Humans really can have superpowers—scientists are studying themHumans really can have superpowers—scientists are studying them
- Why engineers are concerned about aging infrastructureWhy engineers are concerned about aging infrastructure
Travel
- 2024 will be huge for astrotourism—here’s how to plan your trip2024 will be huge for astrotourism—here’s how to plan your trip
- Play and stay in the mountains of eastern Nevada
- Paid Content
Play and stay in the mountains of eastern Nevada - This couple quit the city to grow wasabi in Japan's mountainsThis couple quit the city to grow wasabi in Japan's mountains