Definitions of "species", hybrids and hybrid speciation
edpell said:
I thought the definition of different species was two groups that can not breed and produce fertile offspring.
That definition, which has come to be known as the
biological species concept (BSC), and associated with Ernst Mayr’s 1942 book
Systematics and the Origin of Species, from the Viewpoint of a Zoologist, is a common and popular one, but I’d argue must be taken as general guidance rather than an absolute rule. A more general definition of “species” is “a useful category of biological organisms based on observed traits”, though this definition is to general to be very useful without additions. My point is that the consensus definition of a species is more a question of utility than of objective qualities, with different kinds of biologist finding it useful to defined species in different ways.
You say all panthera can breed and produce fertile offspring. Does this make them sub-species rather than species?
It’s interesting to see how Mayr, who was aware of this, resolved this apparent conflict between the BSC and captive breeding of different cat species. His response was that captive breeding removed reproductive barriers that occurred in the wild, so really wasn’t good data for forming biological concepts.
A problem with this response is that intra-genus cross-species breeding does occur in nature. A recent example is the confirmed cross-breeding of Ursus maritimus (polar bears) and U. arctos (grizzly bears), to produce “
grolar bears” which appears to be becoming more common due to climate-change induced changes in polar bear behavior.
Is there a biology term for sub-species?
Yes, the one you use, sub-species. This is a case of the general scientific principle that if a term is useful in a well-defined context, people should be free to use it.
Is this common, the ability to successfully breed between two groups that are commonly called species?
Yes and no. The general term for it is hybridization. When it results in the formation of a distinct species, it’s termed hybrid speciation. hybrid speciation is “fairly common” in the plant kingdom, in the animal kingdom occurs “mostly” in insects, and less common among larger animals.
Hybrid speciation describes a speciation event, so arguably only occurs when a viable wild population of cross-breeds occurs. By this definition, ligers and tigons don’t pass, as they’re known only in captivity, while time will tell if grolar bears form a distinct population worthy of official recognition as a species. Canis rufus (red wolves) is accepted as distinct hybrid species of C. latrans (coyotes) and C. lupus (gray wolves). That speciation is believed to have occurred about 150,000 years ago. At least one dolphin species is believed to be a hybrid.
Our growing ability to quickly and inexpensively analyze DNA has greatly helped our understanding of hydrid speciation.
Your example answers my question if simple panthera can do it clearly hominids can do it. Curious this is never considered in early homo evolution, Australopithecus to Heidelbergensis.
Curiouser still, there are a few examples of captive cross-breeding within the wider hominidae family, of Chimpanzees and Bonobos (http://www.macroevolution.net/bonobo-chimpanzee-hybrids.html[/url ).
Curious to the point of weird, there’s no scientific consensus that humans can’t be cross-bred with other hominidae species, though chromosome differences suggest that such hybrids would likely be infertile.
This wikipedia article is one of many entries into this weird science realm.
