One problem with explaining evolution is that it happens so slowly that many people don’t think it can happen. They say that different animals have different adaptations, but those adaptations don’t lead to new species. I was wondering if there are animal species where people see them as a single species, but there are also indications that a new species is branching off from it.
For example, there are lots of kids of birds of all different shapes and sizes. Everything from penguins to hummingbirds. Even though they are all the same species, if there were some which couldn’t interbreed, then that would help show how evolution works. For example (just making this up), say interbreeding worked like this:
[Note: This is a fake example I made up. I have no idea if it’s true or not.]
Something like that would be a good example of a species being in a state where a subgroup has characteristics of a different species. Penguins and hummingbirds are birds, but they are also like different species because they lost the ability to breed with each other.
I understand that the definition of species can include some uncertainty. For the nature of this question, it would be best if examples were things that most lay people could clearly see and understand (e.g. birds rather than bacteria).
The first thing you describe is what’s known as a “ring species”. Most often, it’s small creatures that can’t travel very far, distributed around a large lake or mountain or other geographic obstacle.
And “the definition of species can include some uncertainty” because of the exact cases you’re looking for: You have two populations that are starting to diverge, and there’s dispute over whether they’ve diverged enough yet to count as separate species. One example that’s about as close to us as it’s possible to get is modern humans and Neanderthals: Opinions differ as to whether we’re different species or different subspecies of the same species, but whichever side of the line we’re on, we’re certainly close to it.
One of the more interesting ring species is the gull. There are two non-interbreeding species of gulls in England and northern Europe: the herring gull and the lesser black backed gull. The herring gull is also found all over North America and then jumps to Russia and continues west where it eventually becomes the lesser black backed gull. As you move west the differences accumulate until they result in distinct species. Species is just not clearcut.
There is also the Russian tame fox experiment, Domesticated silver fox - Wikipedia, but the Wiki article does not make a claim for speciation. Perhaps others can inform us on that.
Just to be clear: not all birds are the same species. Of the bird groups you mention, there are approximately 17 species of penguins, 330 of hummingbirds, and 50 of gulls.
Greenish warbler and related (sub)species around the Himalayas and Tibetan plateau
Ensatina salamanders in California–nineteen populations form a horseshoe-shaped ring around the Central Valley. Each population interbreeds with its immediate neighbors, but the populations at the ends of the lines cannot interbreed.
Euphorbia tithymaloides, a shrub in Central America and the Caribbean that has been proposed as a ring species
The Shetland monkeyflower has been cited as an example of a new species of plant that became reproductively isolated from its parent via polyploidy.
Oh, and one more point of clarification: A ring species is considered to all be one species, because it’s possible (albeit slow) for genes to spread through the entire population. But if some cataclysm were to wipe out the middle of the ring, suddenly that would no longer be possible, and so the end populations would now be two different species, despite those populations themselves not changing at all.
It hadn’t occurred to me that the pole could be a central obstacle for one, though. That’s interesting about the gulls.
I’d suggest you consider dogs. There are dozens of different breeds, and seemingly more being created all the time. For example, the Dobermann Pinscher, created about 130 years ago by Karl Dobermann of Germany.
I may be wrong, but I guess that any two species that can breed, but only create non-fertile offspring, are species that are currently half-way through divergence. So, donkeys and horses are basically still becoming two separate species; same thing with lions and tigers.
I was taught this example in school. It was long ago and I don’t recall the scientific names or citations, so take with a spoonful of salt:
It involved a species of parasitic wasp which lived in hawthorn galls in North America. Then European settlers arrive and started planting a lot of apple trees. Pretty soon the wasps attacked those as well. However, wasps that emerged from hawthorns did not attract those who emerged from apple trees very much, and vice versa. At first the reproductive barrier was merely behavioral, but over the course of a hundred years or so became post-zygotic or even pre-zygotic (if they mated anyway, they wouldn’t produce fertile offspring).
A better example might be various species of bears. During the ice ages ice would creep out in weird patterns, often cutting off various populations of animals (including bears), and keep them apart long enough that they became isolated. When the ice melted, the populations would come into contact… but there would be little breeding between the populations, creating subspecies, if not species. This is supposedly how polar bears came to be. (The selection for white fur would not directly prevent mating.)
Polar bears and grizzly bears can mate and produce offspring. I don’t know if they’re fertile, but mating between them is rare, and there’s a lot of non-reproductive behavioral differences as well.
For asexual reproduction they likely haven’t missed the news about what’s happened and is still happening to bacteria. There are increasing numbers of bacteria that have evolved to survive in an environment where modern antibiotics exist.
I vaguely remember a documentary about the lemurs of Madagascar (I think John Cleese may have been involved) that documented when and how the lemurs got to the island (19th century, on a big chunk of driftwood) and how supremely adaptable they became at getting food from wildly different environments there. One breed adapted really long middle fingers to get bugs out of holes in trees.
I suspect that those unable or unwilling to comprehend the vast quantities of evidence out there for evolution and the speciation events that have arisen, are not likely to accept any of those more recent examples. They would say that the differences seen were not big enough to count and any differences that were big enough need substantially more time and we are back to square one and needing to present the fossil and genetic record as evidence (either of which by themselves should be convincing enough)
Evolution through natural selection is not a hard concept to grasp. I’d go so far as to say that is is the simplest “Big Idea” ever presented. Anyone still not getting it or accepting it by this point is bordering on the perverse and almost beyond help.
Ah, you haven’t run into the microevolution versus macroevolution theories yet.
Basically, some creationists are claiming that certain kinds of change can happen within a species (such as development of antibiotic resistence, or development of dachshunds and mastiffs) but these changes can never create new species.
Are there any breeds of dogs which cannot interbreed with some kinds of wolves? In general dogs and wolves can interbreed, but is that the case for every dog breed and every kind of wolf? Although dogs were created by selective breeding from wolves, that process happened independently in many different places around the world. In a simple example, if North American dogs came from wolf type NAW, and European dogs came from wolf type EW, even if NAW and EW wolves can interbreed, perhaps not all NA dogs could interbreed with EW dogs. Even though something like that would be from selective breeding rather than environmental evolution, it might be a relatable example of how a new species can come from an existing species.
Or are there any examples of dogs breeds which are a ring species? Perhaps something like certain North American dog breeds cannot interbreed with certain African dogs?
You could probably go by size. While a St. Bernard and a Chihuahua could theoretically interbreed, it’d be very difficult.
That said, domesticated animals are never counted in questions of speciation, because the definition of species is based on what creatures do naturally, and nothing involving a domesticated animal is natural.