Creation of a new species?

[jake-the-peg]

http://news.bbc.co.uk/1/hi/sci/tech/5080298.stm

Wikipedia has the definition of a species as:

Groups of actually or potentially interbreeding natural populations which are reproductively isolated from other such groups

My understanding is that this cross is unattractive to mates of either of the parent species but attractive to similar crosses making them potentially isolated reproductively and hence a new species.

So is this definition of a species correct? if not what should the definition be? and is this cross a new species?

[dawkins]

Hi Jake

This article describes some practical difficulties in defining speciation:

http://sellers.sbc.man.ac.uk/~wis/lectures/hum an-evol/1.html />
IMHO one would expect problems trying to define "species" due to the complexity of evolution. There would be a bit too much design in a system where readily definable species just suddenly cropped up from time to time new and distinct breeding populations unable to mate with anything but their own.. However to study the system we must come up with a testable hypothesis.

To try and answer your question rather than continue waffling:

A hybrid is not necessarily a new species it would take time to discover whether a new breeding group could establish themselves with a gene pool of their own but they would still be very closely related to species that produced them. Mules or Ligers are not species because they are not capable of reproducing whereas dogs are not new species of wolf because they are not reproductively isolated, and that really is the nitty gritty of it all. It all comes down to the gene pool and the fact that we are all mongrels of one kind or another.



D

[dawkins]

p.s. sorry my entire post endded up as a hyperlink.

http://sellers.sbc.man.ac.uk/~wis/lectures/hum an-evol/1.html

[jake-the-peg]

Funny you should mention Ligers and reproduction. It seems only the male Ligers are infertile.

http://www.lairweb.org.nz/tiger/ligers2.html

The other problem with all these species definitions is that the focus entirely on sexual reproduction.

How does one define the species definition in micro-organisms?

How do you define species of amoebae?

[dawkins]

hi Jake

You are quite right, there are problems in finding a suitable definition for a species which encompasses both sexual and asexual reproduction and it may not in-fact be possible to find a definition which is both suitable and practical at the same time The quote from Wikipedia describes the Biological Species Definition (BSD) put forward by Ernst Mayr which obviously relates to sexual reproduction. Mayr developed BSD to replace the morphological view of species which basically looked at visual similarities. While the BSD provides a testable hypothesis for living, sexually reproductive animals it has no use in classifying fossils or asexually reproducing entities such as amoeba. The Evolutionary Species Concept (ESC) was introduced by Simpson:

"An evolutionary species is a lineage (an ancestral-descendant sequence of populations) evolving separately from others and with its own unitary evolutionary role and tendencies."

cont.

[dawkins]

This definition does account for asexual reproduction but is often criticised for having limited practical use.

In asexual organisms such as amoeba it is particularly difficult to define species and it could be argued that each individual is a species in themselves. For this reason individuals are classified through a combination of factors based on how similar they are genetically and how they behave. But never mind asexual reproduction, how about symbiotic relationships and lateral gene flow. How do we define that in species terms?

I must reiterate that species definition is a contentious area of biology that causes much debate. Given that DNA analysis shows a spectrum of inter-relatedness of all life isn't the definition of distinct species actually an old-fashioned concept?

I hope this helps:



http://www.dhushara.com/book/diversit/extra/en ig/senig.htm />




D

[jake-the-peg]

Yes thank you for those links there are some very interesting ideas there.

The whole concept of discreet species does indeed start to seem remarkably artificial when you remember that evolution affects more than just mammals, fruit flies and peas!