species vs. subspecies

[Tom]

How do they differentiate between a fish being a new species or a subspecies of an existing species? Please remember when you're answering this I'm not an Ichthyologist( hell, I probably can't even spell it!), so be as simple as possible.

Thanks,
Tom

[Dinyar]

Ichthyology, like all empirical science, is driven by fashion. While the concept of sub-species is well accepted in most branches of vertebrate taxonomy, it is nowadays unfashionable in ichthyology. For example, there is only one species of tiger, Panthera tigris, divided into eight subspecies. If tigers were fish, we would erect a genus of Tigrinae and then recognize eight separate species, Tigris bengalensis, Tigris indochinensis, etc.

Moreover, ichthyologists are only just beginning to utilize statistical measures of significance in their species descriptions. Many descriptions still simply compare the means and standard deviations of two samples and cite any differences as proof of different "species". This is a bit like comparing two samples of say a hundred people from one place and another hundred from another place, finding that the average height of the two samples differed by say 3 cm, and concluding that each sample must therefore represent different species. It's ironic in some ways that you are nowadays more likely to see sophisticated use of statistical methods in, say, classics, than in ichthyology.

Dinyar

[Silurus]

Moreover, ichthyologists are only just beginning to utilize statistical measures of significance in their species descriptions.

This has actually been around for some time. The main reason it has not been (and is still not) extensively used is that statistical differences are difficult to translate into usable characters in the field.

[aquaholic]

Whew..... I'm glad we got the SIMPLE reply then....
is there an even simpler one?

Winston

[Mike_Noren]

Whew..... I'm glad we got the SIMPLE reply then....
is there an even simpler one?

Sure: there is no qualitative difference between species and subspecies. The dividing line is arbitrary and subjective.

The explanation why that is, is a bit more complicated though.
Whether distinct but similar populations are named as species or subspecies depends entirely on the subjective personal opinion of the systematist - if he happens to like big, inclusive, species (is a "lumper") then the population will be described as a subspecies, if he likes narrow, exclusive, species (is a "splitter") then the population will be described as species.

There is, as has been stated, a certain amount of cultural bias in this. I get the impression splitters are in the majority among south-american ichthyologists, exemplified by e.g. the myriads of very similar loricarid or Apistogramma species. By contrast ichthyologists working with african fish seem to have a tendency to be lumpers, perhaps best exemplified by the cikklid species of the rift lakes - e.g. the single species Tropheus brichardi spans well over a dozen morphologically and reproductively distinct "subspecies" which, had they been south-american Otocinclus or Apistogramma, would no doubt be considered separate species.

Or we can take the tiger, as it has already been mentioned. All tigers are considered to belong to one single species - and yet this one species consists of several reproductively isolated populations, quite different in size, ecology, and coloration. One species? Or eight?

There is no objectively right or wrong answer. It's all personal preference.
But the answer may be of some importance when it comes to raising money and political support for conservation of the animal.

[Janne]

Mike,
I think these explanation says it all...well writen.

Janne