Category: Genetic diversity

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Local and exotic crops in Africa

The long dry spell throughout much of February and March, caused by an unexpected El Nino that kept the main rain belt to the north of Zimbabwe, will cause serious hardship in significant areas of the country.

That’s not the only thing, of course, but an article from the Harare Herald ((Posted at allAfrica.com)) makes a plea for farmers to grow local indigenous grains such as “sorghum, mhunga and rapoko” rather than watch maize “wilt and die four years out of five”.

It is a wonderful article, making lots of good points. That food-for-work programmes should be accompanied by intensive training on growing small grains, so that those who need it most can become self-reliant in food and maybe even sell a bit for income. That modern machinery makes preparation much easier, and it isn’t expensive. That an advertising campaign could make a virtue of sadza ((Zimbabwean porridge?)) the way grandmothers made it. That there are benefits for urban consumers too. And finally, “Variety is wonderful. But we should not be rejecting indigenous grains simply because they are not “modern” or “Western”. We should be using them as well”.

I wonder whether anyone is listening?

The Ethiopian Herald, meanwhile, says green gram is becoming the crop of choice in Southern Wollo zone. A legume, green gram (Vigna radiata, maybe most familiar in the West as mung bean) improves soil fertility, ripens more rapidly and doubles or even triples incomes. One farmer is quoted as having replaced his teff crop with green gram, but if everybody does that, who is going to supply the teff flour for njera?

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Multiple founder effect

The common wisdom is that crops are most diverse in their centres (or secondary centres) of domestication, because that’s where people have been playing with them longest. Wild species, too, are often less diverse when they have moved to a new area. That’s down to the founder effect; a small bunch of founding individuals will have a less diversity than the population as a whole and is also more subject to random fluctuations that can change things from the original population. But on the Invasive Species Blog (via this month’s Mendel’s Garden) I recently read that reed canary grass (Phalaris arundinacea) is much more diverse in North America, where it is a recent arrival, than in Europe, its home. Genes from all over the old world are mixed up within single individuals in North America, whereas they are never found together in Europe. The reason, apparently, is that the species has been introduced many times, presumably from many places, and this has brought widely separated populations together and given the opportunity to mingle their genomes.

I wonder whether the same is true for some of the crops that have really travelled around, like tomatoes or peppers.

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Reindeer, caribou, genetics and global warming

Reindeer (Rangifer tarandus tarandus) were domesticated probably around 20,000 years ago in northern Europe and Asia. They are still kept by many herders in the Eurasian Arctic, who derive their livelihood from their animals. Reindeer from Siberia were imported into Alaska in the late 19th century in an attempt to provide income for indigenous people. In the 1930s an estimated 600,000 reindeer existed in Alaska, but that number is now down to about 20,000. It seems that most people didn’t quite see the point of managing reindeer when all they had to do was go out and hunt its wild cousin, the caribou (Rangifer tarandus granti). One of the unforeseen consequences of this endeavor has been the migration of reindeer into caribou herds and until recently it was unknown to what extent this influx has had an impact on the genetic diversity of caribou. A recent analysis of microsatellite DNA in caribou and reindeer in Alaska, however, shows that very little genetic introgression seems to have taken place into either species and the authors think the reason could be that hybrid offspring may have a lower chance of survival. It is interesting to note that their study also indicates that the Alaskan/Russian reindeer and the Alaskan and Canadian caribou are much more closely related to each other than either is to the Scandinavian reindeer.

Caribou, which can be found throughout Alaska and the Canadian territories, migrate often in large herds between their summer and winter pastures. The porcupine herd, for example, numbers in excess of 100,000 animals and covers a distance of over 2000 km on its yearly route from the Yukon to the calving grounds on the Alaskan Arctic coast (the very same area the US government is trying to open up for oil exploration).  Many native people in Canada and Alaska still depend on these animals for their survival and they are becoming concerned that increasing human development and global warming may either affect the size of caribou herds or change their migration patterns.

From Michael Kubisch

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Domestication

Michael’s post on water buffalo genetic diversity and domestication reminded me that I was intending to point you all in the direction of Dienekes’ Anthropology Blog. Although Dienekes mainly blogs about the genetic diversity and evolution of humans, he does occasionally link to papers on animal domestication and related issues. He has an RSS feed, which makes it easy to monitor his blog. In the past couple of years he has pointed to interesting papers on:

Incidentally, a great paper reviewing the use of genetics and archaeology to document domestication came out last year and you can see the abstract here. Now, what’s really needed is for someone to bring together the human, livestock and crop genetic data.

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Water buffalo diversity

Michael Kubisch is a geneticist and reproductive physiologist working at the Tulane National Primate Research Center in the New Orleans area. He’s sent us his take on a recent paper on the genetics of the water buffalo. We really welcome this kind of contribution from our readers. Keep ’em coming! Here’s what Michael has to say:

Results of an interesting study by Chinese researchers have just been published, describing an extensive analysis of the genetics of Chinese swamp water buffalo (Bubalus bubalis). The Chinese swamp-type buffalo differs from the Indian river-type buffalo by the fact that it has 48 chromosomes compared to the 50 found in the latter. There is a third subspecies, the wild water buffalo, which may still exist in Southeast Asia, although its population size and genetic status are unknown and the animal is listed on the IUCN red list as being threatened. Based on analysis of mitochondrial DNA (which is solely inherited from one’s mother and consequently ideal for tracing maternal inheritance patterns), it appears that river and swamp buffalo split about 28,000 years ago with a further split in the swamp buffalo into two maternal lines taking place about 18,000 years ago. The genetic diversity varies between the two swamp buffalo matrilines in China and the authors suggest that the difference between the two lines might in part be due to the fact that occasional genetic introgression from wild swamp buffalo might have taken place into one of the lines. Interestingly, domestication of water buffalo seems to have occurred independently in India and China, most likely as a result of rice cultivation. Substantial numbers of water buffalo outside exist Asia, among other countries in Italy, where, as any cheese afficionado will know, their milk is used for the production of mozzarella.