Fewer seals:
The whale population has to a degree rebounded after whaling was restricted. That’s good news. I like whales. But whales eat krill, and so do seals. As a result, apparently there are fewer seals. (Tim Coulson and Sonya Clegg, Fur Seals Signal Their Own Decline NATURE vol. 511 no. 7410 July 24, 2014 page 384 and J. Faucada and J. I. Hoffman Climate Change Selects for Heterozygosity in a Declining Fur Seal Population page 462 in the same issue) That’s sad but one might rather expect it. You can’t have everything. But here comes the issue of diversity.
NATURE, SCIENCE and SCIENTIFIC AMERICAN recently launched a coordinated series of article to raise our consciousness about diversity. The moral is that, in Shakespeare’s words, diversity is “O, wonderful, wonderful, and most wonderful wonderful and yet again wonderful, and after that out of all whooping.” Odd, everything else in life that has benefits has also its costs, you know, like recovering whales.
I found a bit of confusion between the two articles. The first says that you cannot select for heterozygosity (two copies of the same gene rather than copies of two variants of that gene), but that is precisely what the title of the second article announces. Seems to me you can breed monoclonal mice – all genes match – so there must be some way not to breed for monoclonal, which would mean selecting for heterozygosity, wouldn’t it?
We are told that, “Higher heterozygosity frequently correlates with an individual’s ability to successfully (split infinitive courtesy of authors – the English are usually more careful with their English) survive and reproduce – more heterozygous individuals are fitter.” Well, yes. We understand that there is such a thing as heterozygote advantage. But correlate means it could go both ways. In an environment where things are going well there is going to be more heterozygosity anyway.
So the evidence indicates less heterozygous seals are dying faster. All right. But it also suggests that more heterozygous seals reproduce later and less. Hmm. That doesn’t sound like fitness even as they have defined it.
But of course we would have expected that. Relative inbreeding has to reduce heterozygosity; the small population is going to lose alleles (versions of genes) faster than the large one. And relative inbreeding produces higher reproductive rates, regular as clockwork. This effect is obviously unknown to the authors of either article.
We still have much work to do.
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