Subject: Re: NANFA-L-- Review of Suckers in North America
From: Peter Unmack (peter.lists at)
Date: Tue Oct 12 2004 - 19:04:28 CDT
On Tue, 12 Oct 2004, Irate Mormon wrote:
> Quoting "dlmcneely at lunet.edu" <dlmcneely at lunet.edu>:
> I understand. Genes code for proteins, therefore the more proteins you can
> count, the more different genes are present within the sample.
Minor technical correction, there are more alleles, not more genes.
People always mix these two terms up (and many folks teach it wrong too).
Gene is also not a very good term as there can often be multiple copies
that can be different or the same in various places around the genome.
Gene locus or locus is a better term as it defines a set spot in the
genome for the sequence/protein in question.
> I am really looking for data that correlates genetic diversity in
> diverse populaitons with survivability.
Ultimately, this is all theoretical. There is virtually no evidence that
higher genetic diversity correlates with higher fitness/adaptability,
although Dave is likely correct, as by definition if you have more
variation you are more likely to get through tough times (in theory).
The problem is 99.9999999% of the time we do not have genetic information
on the variability of the specific locus or traits in question, and in
most cases we don't even know what loci/genes/traits we should be looking
at. Most folks examine silent variation, or non-coding DNA as a surrogate
for variation. But, you can have two genomes that are exactly the same
except for a single amino acid change (due to a single base change) and
that can make the difference between one individual living and the other
dying. The bottom line is that until we start sequencing genomes on a
large scale (which isn't massively far away), then we really don't have
clue as to what genetic variation means. But, having said all that, it is
likely that silent variation will likely be a reasonable surrogate, but
not in all cases.
As others mentioned, many invasive species have done extrordinarily well
based on a very small initial founder population. Some of these species
have genetic advantages over others. For instance, it is thought that
being polyploid (having more than the normal two copies of your genome)
can provide massive advantages. Some cyprinids (eg carp) and trouts and
salmons are tetraploid (as are many others). Other species just have
better traits for certain situations (eg, more parental care) that confer
them great advantages.
Back on the question of genetics though, pupfishes seem to have the
ability to live in more environments than any other fish species and don't
seem to suffer from inbreeding affects unless they are extreme (like in
Devils Hole). No one really knows why this genus is far superior to most
other fishes as far as its environmental tolerances. Thus, at this stage
we can't even answer basic questions like that at the genus/family level,
let alone within species variation and it's significance to their survival
Also, as others have mentioned the environment the organism is raised in
can be crucial. While we all have a tendancy to focus on genes we forget
about the environment. Selection works on phenotypes, not genotypes, and
the phenotype is derived from genetics + environment. Thus, if you have
the same genetic composition, but change the environment you can change
the phenotype. Thus it can get extremely complicated very fast.
Sorry about the techno babble. I'll be happy to explain anything a little
better if I have confused folks.
currently Salt River, Arizona.
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: Fri Dec 31 2004 - 11:27:45 CST