Inspired by this old thread wherein bobcats mating with domestic cats was discussed. It came up that not only can bobcats and housecats breed, but the offspring are fertile as well. So, doesn’t that mean they should be considered the same species?
Yet, according to Wikipedia, not only are they not cospecific, they are not even cogeneric. Bobcats are *Lynx rufus, and housecats are Felis sylvestris. Is the fertile-offspring rule still the defining factor of species-hood? Or are longstanding taxa normally kept as they are even though they may violate the rules that would be used to define the taxonomy of newly discovered animals? If you believe Wikipedia there are some primatologists that would include the chimpanzee in Homo alongside ourselves, though I doubt very seriously that a human and chimp could produce fertile offspring.
The definition as it’s now used requires not only that fertile crossbreeds are possible, but that they occur in the wild. With domesticated varieties of animals, this fails, since no situation involving a domesticated animal can be considered “wild”, so domestic animals are classified in the same species as their nearest wild ancestor (hence why housecats are now called Felis sylvestris, possibly with the domesticus subspecies, rather than the older Felis domesticus). Wild F. sylvestris are found only in Africa, and I think the lynx is strictly new-world, so there’s no possibility of interbreeding there. There also could be (and probably are) behavorial barriers, such that most sylvesters wouldn’t choose to mate with most lynxes and vice-versa, even if they did encounter each other.
There are plenty of instances when inter-genus hybridization is possible, so if this can happen (and I’m still unclear if it can) it wouldn’t be breaking any new ground. As long as it doesn’t happen regularly and in the wild, then nothing need be changed.
The Scientific American article is quite good, so you should read it if you can get your hands on it. It’s the current issue, so that article isn’t available on its website yet. Maybe next month.
All in all, it seems to this layman that there is a lot of problem in the idea of “species.” We know one when we see it, but have a hard time putting it into words. DNA analysis seems to be more useful than larger-scale clues (such as mating). But that would also lead to a lot of species being conflated when our eyes tell us they are distinct.
Go figure. I am still holding out for Neanderthal to be a branch of Sapiens.
Not really. There is an endless list of species that routinely produce perfectly viable hybrids in the wild and are still considered to be good species, starting with wolves, coyotes and jackals and working our way up to various whale species
The only standard for species classification is that there be minimal genetic interchange, and there isn’t even any staredard for what qualifies as mininal. There is certainly no reason why lynx cat hybrids couldn’t occur regularly in the wild and still leave two perfectly good species or genera.
Fylis sylvestris/lybica is found throughout Asia, Africa and in some of the more remote parts of Europe. The species overlaps considerably with the European lynx so there’s is no geographical impediment to hybridisation.
Yep. The most likley outcome of a lynx and cat encounter is that the lynx eats the cat. That’s a pretty significant behavioural impediment to crossbreeding. It would probably only be by using individuals raise dint he company of the othe species that you could hope for a peaceful encounter.
That hasn’t been the defining rule for over a hundred years, I don’t know why it still turns upo in high school textbooks. People have been aware of fertile wild hybrids at leats since Darwin’s day. A species is an approximately genetically isolated population, nothing to do with ability to hybridise.
There aren’t any rules being violated. Recent taxonomy is based on on genetic similarity, and provided two species are gentically distinct they qualify regardless of how physically close they may be or whether they cna hybridise.
The truth is nobody knows whether humans and chimps are interfertile. I’d be very suprised if we were not interfertile to some degree. The reason given for lumping humans and chimps is because of the degree of genetic similarity.
OK, I stand corrected on a number of points. Is it still fair to say that there isn’t really any definition for “genus” at all, beyond “a classification a bit larger than a species but smaller than a family”? “Can produce infertile hybrids” or “can produce fertile hybrids, but typically don’t” might be good rules of thumb for two species being in the same genus, but it’s not absolute either way, correct?
Thanks to all who responded, especially Chronos. However, I see one problem with the requirement that the population interbreed in nature. Pet dogs don’t normally interbreed with wolves, yet they are now considered to be cospecific.
With cats on the other hand there has been a major splitting trend over the last 50 years or so; they all used to be classified as genus Felis, but now only the smallest ones are.
That is just a convention because domesticated animals don’t occur in nature. We could, arbitrarily, assign all domesticated populations a new species name if we wanted. It’s more about bookkeeping than about anything else, but since most domestication seems to have occurred in a timescale shorter than that of speciation, it seems like a good call.
n.b.: I’m speaking here of domesticated animals in particular. For plants, there might be a different option that makes more sense since some domesticated plants can’t reproduce at all without human intervention.
That’s about right. If we have two closely related species then we tend to lump them into a common genus, and if they’re closely related they can probably interbreed. But there are probably species within the same genera that can’t produce fertile hybrids, and there are certainly species in different genera that can produce fertile hybrids.
Get your hands on that Scientific American article mentioned above. It really is quite good, and goes into quite a bit of detail about the evolutionary history of cats as well as they relatedness based on DNA analysis.
Interestingly, tigers and lions* split on the order of the same timescale as humans and chimps (slightly less, IIRC). And considering the much longer reproductive cycle of apes vs cats, the effective generational distance is probably longer for the tiger/lion split. Yet we know they can interbreed and some of the offspring are fertile. Same with African and Asian elephants**, although I don’t believe that fertility of the offspring has been demonstrated.
*both in the genus Panthera
** the former in the genus *Loxodonta *and the latter in the genus Elephas
Hey! I never thought of that. Sylvestris just means “wild”, so, “wild cat”. Usually for housecats a subspecific moniker “catus” or “familiaris” is added, so the full name is Felis sylvestris familiaris (or catus)
Very emphatically yes! The higher taxonomic categories including genus, family, order, class, phylum… are all far too cumbersome to encapsulate our developing understanding of evolutionary relationships. Frankly, we need to toss the Linnean system and its implied ranked hierarchy in favor of cladistic taxonomy, which will be the devil to use, but will more accurately represent how little or how much we know of the relative divisions within and between clades. Case in point - under the old system, I firmly believe every member of the Class Mammalia should be members of Class Osteichthyes.
