online news. : hudson river tomcod evolve pollution resistance

The title says it all. I found an online news article about tomcod in the hudson river evolving resistance to pollutants. I wish my local rivers were that open in the winter.

http://www.livescien...son-110218.html

The title says it all. I found an online news article about tomcod in the hudson river evolving resistance to pollutants. I wish my local rivers were that open in the winter.

http://www.livescien...son-110218.html

PCBs in the Husdson are said to have greatly contributed to the recovery of the striped bass after the population crash of the late '70s.
High PCB content in Hudson River stripers caused NY to shut down commercial harvest and wide spread news reports of the contamination discouraged the rec harvest. They may have even shut that down too, I can't remember.
In the mean time, the Hudson population seemed to be able reproduce OK despite the contamination.
Not long afterwards there was a coast-wide moratorium on striper commercial harvest [greatly disputed by the comm fishermen and made famous by singer Billy Joel getting arrested for illegal harvest as protest and subsequent song written].
It is believed by some that the Hudson fish already rebounding by virtue of the PCB scare supplied surplus recruits to restock the population at large.
Disclaimer: Written completely from memory, reserve the right to have got it all mixed up.

I wonder if they tested those fish for a founder effect. When I was a kid growing up near the equally polluted Hackensack River, all the Tom cod were gone. My guess is that a fairly small group with the gene variation took hold and repopulated the entire New York Harbor-Newark Bay system. And it wouldn't surprise me if the large predatory fish in the region also have a PCB tolerance.

The title says it all. I found an online news article about tomcod in the hudson river evolving resistance to pollutants. I wish my local rivers were that open in the winter.

http://www.livescien...son-110218.html

I wonder if they tested those fish for a founder effect.

The article mentions that the gene responsible has been identified. It also states that 99% of the tomcod in the Hudson River have this gene compared to less than 10 percent from unpolluted rivers. In other words there is no founder effect. This gene was a preexisting part of the genetic diversity of the whole species.

Technical note:
The presence of the gene in a given individual fish does not automatically endow that specimen with any particular resistance to the toxins. Every organism carries genes which never get expressed at all in their lifetime. Thus, when exposed to detrimental contaminant, the evolution it induces more often involves shifting allele frequencies to induce the expression of these existing protective genes. This is why maintaining genetic diversity is so important to the ecology. If the entire population of tomcod could be traced back to a relatively recent 'founder' pair genetic diversity would be limited to those 'founders'. If those founders had lacked this gene, as over 90% of the population did lack it, the toxins would have doomed the tomcod in that region. Also, with this gene preexisting in the population, the effects of this toxin will not event significantly effect the genetic diversity of the tomcod.

Here is an example, on oceanconservationscience.org, where even people who should know better confuse genetic diversity with genetic variation or allele frequency.
Reversal of Undesirable Evolution in Fish

In the second phase of the study, researchers allowed five generations of recovery, in which fish were allowed to reproduce naturally with no human interference. Researchers found that body size of the fish gradually rebounded, despite previous theories suggesting that it is impossible to reverse genetic changes. Those results were published in Proceedings B.

Relevant line bolded. It was not so much a theory as it was the result of a study, which I could probably find with a little more effort. Yet this study was not about genetic "changes", but about the loss of particular genes. Such as what would have happened if the Hudson river tomcod population was limited to the 90%+ of the tomcods lacking the protective gene. All manner of genetic variations, allele frequencies, and gene expressions can result in all manner physical, behavioral, and sensitivity traits without any change in the underlying genetic diversity whatsoever.

The danger of this conflation between genetic "change" and genetic diversity is that it leads to the impression that protecting this genetic diversity is not absolutely required, under the false belief it is reversible. If the tomcod had been limited to the genetic variations available to over 90% of the population the Hudson River population would have been doomed. Once a gene is gone it does not come back, and that has nothing to do with genetic variability which merely effect the expression level of existing genes.