Giraffes And Frogs Provide More Evidence Of New Species Hidden In Plain Sight

Science Daily ^ | 1-2-2008 | BioMed Central.

[Old Professer]

Frogs, where else?

[Thumper1960]

Apply this to humans and see how many species of us there are.

[From many - one.]

modification of previous response:

assuming species with at least the potential for two sexes, as opposed to breeding strains, etc.

[brytlea]

I don’t recall the “in the wild” part of the definition, but my textbook is in the attic and I’m not going up there to get it. In general, I recall that a species share similar traits and can produce fertile offspring. Dogs and wolves, for instance are now considered the same species.
susie

[From many - one.]

The “in the wild” part is because of situations like lions and tigers which would never mate naturally but whose chromosomes are similar enough to allow reproduction.

Since speciation is a process, fertility diminishes as populations accumulate changes, but it can take a while to reach zero fertility.

An interesting demonstration of that is “ring species”

This link gives an explanation, and wiki has some nice diagrams:

Ring Species: Unusual Demonstrations of Speciation by Darren E. Irwin, Ph.D.
http://www.actionbioscience.org/evolution/irwin.html

[brytlea]

I actually read some interesting things on lions and tigers and it was suggested that they might well all be the same species. Of course, the word species is simply something we made up to put things into categories, however my only beef is that it does need to have an agreed upon meaning, otherwise it’s pretty worthless to even talk about.

susie

[brytlea]

This might interest you.

http://www.newscientist.com/channel/life/evolution/mg15821389.000

susie

[mamelukesabre]

Hybridizing of cat species typically result in infertile males and fertile females.

Common examples:

tiger cross lion

domestic housecat cross african serval (aka savanna cat)

Look up liger, tigon, or savanna cat anywhere such as wikipedia for brief discription.

[From many - one.]

That’s not uncommon and not at all the same as a species with all males infertile.

[mamelukesabre]

You missed the point. Your definition of species doesn’t seem to work here because there are viable females produced but not viable males.

[allmendream]

That is because if the reproductive separation of the two populations has occurred for a long time but they still look identical, the tendency is to say they are the same species. Then genetic analysis says “Whoa, these guys arn’t even that close and do not interbreed and have not in hundreds of generations” so they say “New Species, has been for estimated X number of years.”

New species can form when an interbreeding population achieves reproductive isolation. But although you might say the evidence suggests that after a long time there WILL be genetic differences between the population sufficient to call them different species; one cannot show that there IS PRESENTLY this genetic difference. They have just begun to diverge from each other.

An example of almost instant reproductive isolation happened to an insect that makes a sex pheromone from a chemical precursor it takes from the plant it lives and feeds on. A new plant was encountered that had a different chemical precursor and made the sex pheromone different enough that after only a few generation of preying upon that plant, the insects could no longer recognize or be recognized as a mate by the parent population. In the lab they might be forcibly ‘merged’, and one couldn’t easily find a genetic difference between them (although there was obviously some selection for the genes for sex pheromone recognition).

[allmendream]

It is not that they cannot interbreed, it is that they DO NOT in the wild. I also do not understand this ‘limited interbreeding’; if there is gene mixing between the lineages then they are not that distinct, more like ‘eco-types’ or ‘races’ in humans.

A Lion and a Tiger can interbreed and produce fertile offspring that could then breed into one of these lineages (mixing Tiger genes into Lions or vice versa). However this only happens in captivity. Lions and Tigers do not interbreed in the wild and are obviously different species and have been for a very long time.

[From many - one.]

Then it’s a hybrid. The female hybrids can backcross with the males of the parent species. The males simply die out.

Somewhere, several posts back, I pointed out that speciation is a process, not an on/off switch.

And, yet again: in the wild. Not zoos or petri dishes.

[Mamzelle]

re: I do not see how this constitutes new species.)))

Me neither. Sounds more like "varieties" or even "breeds"--

I don't trust "scientists" who play more with definitions than facts. This article is attempting to muddy the idea of species so that they can make us accept some self-serving conclusion farther on down the line.

[allmendream]

Is the opposite also true in other species, or is it a direct consequence of spermatogenesis or oogenesis that makes one more susceptible to chromosome misalignment during genetic recombination of the parental genomes to make reproductive cells? I had not heard that the males of big cat crosses were completely sterile, although I did know that a female Tigon had reproduced with a Tiger making a TiTigon (3/4 Tiger and 1/4 Lion).

But as you pointed out, it is a process, not an on/off switch. Transversions in the genome will accumulate in divergent populations that do not interbreed making hybrids between the two populations have increasing reproductive problems attempting to merge the two genomes to make reproductive cells.

[mamelukesabre]

Lions and tigers routinely bred in the wild when they had large overlapping ranges.

[allmendream]

They are attempting to reconcile the facts of their reproductive isolation with the definition of species they were put into based upon their morphology and obvious interrelatedness to a neighboring population. Contrary to the idea put forth that Science is dogma, it is trying to find the exceptions to definitions and cases that test the limits or fall into gray areas that bring name recognition. Thus this article that questions if we are prepared to accept that all frogs of the same size with little yellow dots from the same continent are not necessarily the same species, even if you have to look at their DNA to find a difference and show they are divergent populations. Is that muddying the definition of species, or trying to clarify where the facts fit within the definition?

[From many - one.]

I don’t know. I do more with plants and fungi than mammals. Other vertebrates vary also as the nature of the sex chromosomes.

Here’s a pretty good, but dense, review article:

The Evolution of Sex Chromosomes and Sex Determination in Vertebrates and the Key Role of DMRT1

http://content.karger.com/ProdukteDB/produkte.asp?Aktion=ShowFulltext&ArtikelNr=96234&Ausgabe=232296&ProduktNr=231547

[From many - one.]

Probably, that’s why they still have some limited fertility. I’d like a source for your statement though.

[mamelukesabre]

Try any source. wikipedia for instance. If you can wait a sec, I’ll even look it up for you.