h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Okay so the answer is probably "yes" but...

This one has been hovering in the back of my mind for a while now, probably since I watched the "insides Nature's Giants" Dissection special.

Saw again there the rare cross-breed: A Liger.

Lions and Tigers normally never meet, so this isn't a problem, as the two species are kept separate by virtue of living in different continents.

However hovering at the back of my mind is this definition about what a species is which is to be able to breed successfully with fertile offspring (which is why donkeys, asses and mules have a problem)

Now If I were to hazard a guess it'll be somethgin like there's a fuzzy line between genus and species and the whole breeding thign is more what you'd call 'a rule of thumb.'

So I suppose what I'm really asking is can animals of different genus mate successfully? (hang on, clearly they can - I mean doesn't that problematise what it means to be a species - or not?

would they not qualify as different breeds of cat????

just like different breeds of dog can mate and produce puppys

The traditional answer is that lions and tigers can breed and produce "ligers", but the offspring are sterile, just like mules and jennets.

But it is actually more complicated than that, because it has all evolved haphazardly without any purpose. For example, hooded crows and carrion crows generally occupy different locations, so they don't tend to meet. But where the two creatures both occur, they can breed and the offspring are reasonably fertile. But not as fertile as the offspring of two parents of the same type of bird. So scientists are in two minds as to whether these are two species or two races of the one species and keep changing their minds.

In the case of a "ring species", the members are located in a ring with something in the middle which keeps them apart. Animals can breed with the ones on either side of them, but there are minor differences along the chain so that the ones at the two ends of the chain can't breed with each other even though they live side by side. An example is a type of bird which stretches all the way from Ireland through Europe, across Asia, across Alaska and Canada to Newfoundland. All the birds along the way can breed with their neighbours, which suggests they are all the one species, but the ones in Newfoundland can't breed with the ones in Ireland, which suggests they are a different species. The same effect can be found in a much smaller scale with land animals around one of the valleys in California.

not just Ligers - Female tiger and a Lion
but also Tigons - Male tiger and a Lioness.

and then cross breeding the Ligers and Tions gets really confusing.
Someone somewhere had nothing to do on a friday afternoon at the zoo methinks:

http://www.lairweb.org.nz/tiger/tigons.html

also according to that site it seems it is the male hybrids that are sterlie - the females often aren't so can be further hybridised.

Dogs are all officially the same species, but could a male great dane and a female chihuahua really breed?

And for that matter, could a male chihuahua and a female great dane breed without the use of a stepladder?

To answer that question you need to google Jeff Dunham and watch some of his live shows. He has a great story, that had me in stitches, about when one of his dogs was in heat.

I cant get a link atm as in work and restricted to which sites I can go to... but it is hilarious!

The problem is "species" is just an attempt to label something that´s rather fuzzy. Nature doesn´t divide things nicely that way.

My daughter will definitely want a Cabbit (from the medical curiosities) page of lairweb.

t.

Yes... the problem is humans.... we like 'labels', and we like 'definitions'....

To some extent these labels are very useful, as it aids talking and writing about things, and to an extent explains very well the differnces and seperations between differnt animals and plants.

It works less well with things like microorganisms...

Strictly* speaking there is a very clea definition of species (as there is of Kingdom, phyleum, Class, Order Genus and species), but it isn't a satisfactory system for classification of everything; hence why with plants and bacteria etc, there is a need for futher subdivision, with subspecies, and such like...

I spent some of my university time doing some incredibably interesting (no, that is a lie it was one of the dullest things I've ever done), on the cladistics of slime moulds... ... Actually the whole taxonomy thing breaks down very quickly for some species/creatures, as they don't really 'fit' in a given Kingdom, or class or... etc... Those pesky microorganisms are to some extent responsible for some of this, as over the long period of evolution many creatures have ended up with bits of DNA from such micro-organisms (especially viruses), and so you can get 'lateral' evolution as it were; the cladistics/taxonmy system really only works with pretty liniar evolution; 1 species; devides into 2 species, 2 species devide into 10 species, etc., etc., of course, the closer species are evolutionary, the less widly differnt their genetic differnces, and so the more likely that cross-mating can occur succesfffuly.... so a 'third generation' species, might be able to mate back* with a 'second generation' species, which again kinda screws up the nice neat liniar system we need to sufficiently manage to put everythign into nice neat boxes in the evolution/taxonmy tree...

Doesn't the current definition of 'species' have to do with whether individuals *do* interbreed in nature, rather than whether it's possible in captivity? In other words, if there's a barrier to reproduction - genetic, geographical or even behavioural - then the gene pools are separate and thus there are two species.
http://en.wikipedia.org/wiki/Species_problem#Mayr_and_recent_history

Gif

The main bit from what I recall of the defination has to do with 'viable'* offspring, no good if they can* mate, but only produce offspring which can't then mate because thei're infertile; the infertility useually results from the Chromosomes of the two species not being able to 'line up' (becasue they don't match),

The geographical seperation is one way in which new species can arrise, as a single species is seperated by some geographical barrier, the two differnt environments they are in, leads to divergent evolution as the environemntal pressures leads to selective pressures that drive genetic selection to best enable each to thrive in the two differnt environments...

>And for that matter, could a male chihuahua and a female great dane breed without the use of a stepladder?<

They could always resort to the missionary position

Could a male great dane and a female chihuahua breed with the aid of artificial insemination?

And if it turned out they couldn't, who would clear up the mess ?

Gif

The fertilizing in that case wouldn't really be the problem, but even if the mother could survive the pregnancy, she would not be able to give birth without a c-section. (A website I was a member of for a while had a member that rescued a female miniature pinscher that had been allowed to be bred by an Alsatian. Another week of pregnancy, and her uterus would have ruptured.)

We tend to think in Platonic forms, and as Xanatic says, species aren't Platonic forms, which confuses us.

TRiG.

I was thinking the same thing about wolves and (domestic) dogs the other day; are they the same species?

Presumably all the same issues apply...

Gif

Random thought... what about a male chihuahua and a female great dane? Comical, yes. Successful?

What's doggy for "is it in yet?"

"wolves and (domestic) dogs ... are they the same species?"

Well, they can certainly interbreed. And either interbreeding them or owning a hybrid wolf/dog is, in England and Wales at least, illegal.

There was a bit of hype a few years back here about this. I think they called them 'northern breed' or something.

The whole issue of wolf hybrids seems to be fairly divisive in certain dog owning circles (not that I am at all familiar with such circles, but googling brings up several divided opinions in forums).

What size are wolfhounds compared to their parents? Do they get bigger like the ligers?