Folks here will know that I’ve occasionally pointed out a stupidness in the way species are defined. By definition, the result of an inter-species hybrid is forbidden to be thought of as a new species. This, IMHO, is rank stupid of the highest form as we have a load of evidence for species “sudden formation” by exactly that means. The Triangle Of Wu, for example, explains how 3 new species families come out of inter-species crosses between the original mustards, turnips, and cabbages.
While I learned it as Wu, the recent (more PC?, or just propagating a Japanese error?) trend is to call it “U”. In reality the guys name is a Korean character set and any transliteration is as right as any other, in that they are all made up. But I digress…
The triangle of U is a theory about the evolution and relationships between members of the plant genus Brassica. The theory states that the genomes of three ancestral species of Brassica combined to create three of the common modern vegetables and oilseed crop species. It has since been confirmed by studies of DNA and proteins.
The theory was first published in 1935 by Woo Jang-choon, a Korean-Japanese botanist who was working in Japan (where his name was transliterated as “Nagaharu U”, his Japanese name). Woo made synthetic hybrids between the diploid and tetraploid species and examined how the chromosomes paired in the resulting triploids.
So maybe Triangle of Woo is more accurate… Woo Wu U… but I digress…
The key point here is that a boat load of key vegetables, from rutabagas to Russian kale to rapeseed (canola) to some kinds of mustard species are directly a result of inter-species hybrids and have been recreated from the original species as proof of it.
Something similar happened with wheat, so we have several kinds of wheat that are very different (yet all called wheat, though some get ‘special’ names too like spelt and emmer). There has been a bit of a cult rise up over the different kinds of wheat with folks claiming that modern wheat has a toxic kind of gluten not found in old wheats and that it causes all sorts of health problems. If find that hard to accept given that the basic crosses happened long ago and the components of the gluten are fairly common in many kinds of seeds; but this posting isn’t about that (and I’ve not gone into it in any depth, really).
But what is of interest to me is that there are these several crosses of different grass species in the wheat lines. Yet more ‘new species from inter-species hybrids’. I’m fond of saying that “The Species Barrier is really more of a Species Strong Suggestion”… And wheat shows that clearly.
Sidebar On Ploidy
– or how many copies of chromosomes and genes you have
There are a great many other of these inter-species hybrids, especially in plants. Plants are rather more willing to just ‘double up’ their chromosome count and let all the chromosomes ‘get along’ together. This is called being a “tetraploid” or sometimes just a polyploid, as in this text about the brassicas:
These three species exist as separate species, but because they are closely related, it was possible for them to interbreed. This interspecific breeding allowed for the creation of three new species of tetraploid Brassica. Because they are derived from the genomes of two different species, these hybrid plants are said to be allotetraploid (contain four genomes, derived from two different ancestral species). (More specifically, they are amphidiploid, i.e., containing one diploid genome from each of the two different Brassica species). Data from molecular studies indicate the three diploid species are themselves paleopolyploids.
Note that last bit about paleopolyploids. This ‘doubling up’ goes on all the time in all sorts of species, and has for the history of life. And that, BTW, is what makes a turnip different from a rutabaga. Both the rutabaga and Russian Kale are a interspecies cross between the turnip and the cabbage lines, but with different results; while the turnip is just a turnip… and with 1/2 the genes of a rutabaga.
Polyploidy is the state where all cells have multiple sets of chromosomes beyond the basic set, usually 3 or more. Specific terms are triploid (3 sets), tetraploid (4 sets), pentaploid (5 sets), hexaploid (6 sets), heptaploid or septaploid (7 sets) octoploid (8 sets), nonaploid (9 sets), decaploid (10 sets), undecaploid (11 sets), dodecaploid (12 sets), tridecaploid (13 sets), tetradecaploid (14 sets) etc. Some higher ploidies include hexadecaploid (16 sets), dotriacontaploid (32 sets), and tetrahexacontaploid (64 sets), though Greek terminology may be set aside for readability in cases of higher ploidy (such as “16-ploid”). Polytene chromosomes of plants and fruit flies can be 1024-ploid. Ploidy of systems such as the salivary gland, elaiosome, endosperm, and trophoblast can exceed this, up to 1048576-ploid in the silk glands of the commercial silkworm Bombyx mori.
The chromosome sets may be from the same species or from closely related species. In the latter case, these are known as allopolyploids (or amphidiploids, which are allopolyploids that behave as if they were normal diploids). Allopolyploids are formed from the hybridization of two separate species. In plants, this probably most often occurs from the pairing of meiotically unreduced gametes, and not by diploid–diploid hybridization followed by chromosome doubling. The so-called Brassica triangle is an example of allopolyploidy, where three different parent species have hybridized in all possible pair combinations to produce three new species.
Polyploidy occurs commonly in plants, but rarely in animals. Even in diploid organisms, many somatic cells are polyploid due to a process called endoreduplication where duplication of the genome occurs without mitosis (cell division).
The extreme in polyploidy occurs in the fern genus Ophioglossum, the adder’s-tongues, in which polyploidy results in chromosome counts in the hundreds, or, in at least one case, well over one thousand.
It is also possible for polyploid organisms to revert to lower ploidy by means of haploidisation.
So sometimes the genes “double up”, sometimes they “double up from two parent species”, and sometimes you get a shuffle and mix, or other times a mutate and mix, and then sometimes you can get a reversion back to a lower count via a ‘divide by 2′. With all that shuffle, mix, cut the deck, reshuffle and double the deck with mixing from other species; well, that’s how you get big leaps of species formation, IMHO. While I’m sure at some point they will be forced to accept species hybrids as species formations, last time I looked it was still a forbidden conclusion. Yet nature does not listen to the definitions of biologists…
Wheat cultivation has been around for about 10,000 years. (At that point it gets murky, and IMHO could have an even earlier history in the prior turn of civilization, but that’s speculative). What is known is that it originated in this line of history about 10 kya, and with some specific kinds in evidence about 8000 B.C.
Cultivation of wheat began to spread beyond the Fertile Crescent after about 8000 BCE. Jared Diamond traces the spread of cultivated emmer wheat starting in the Fertile Crescent sometime before 8800 BCE. Archaeological analysis of wild emmer indicates that it was first cultivated in the southern Levant with finds at Iran dating back as far as 9600 BCE. Genetic analysis of wild einkorn wheat suggests that it was first grown in the Karacadag Mountains in southeastern Turkey. Dated archeological remains of einkorn wheat in settlement sites near this region, including those at Abu Hureyra in Syria, suggest the domestication of einkorn near the Karacadag Mountain Range. With the anomalous exception of two grains from Iraq ed-Dubb, the earliest carbon-14 date for einkorn wheat remains at Abu Hureyra is 7800 to 7500 years BCE.
Remains of harvested emmer from several sites near the Karacadag Range have been dated to between 8600 (at Cayonu) and 8400 BCE (Abu Hureyra), that is, in the Neolithic period. With the exception of Iraq ed-Dubb, the earliest carbon-14 dated remains of domesticated emmer wheat were found in the earliest levels of Tell Aswad, in the Damascus basin, near Mount Hermon in Syria. These remains were dated by Willem van Zeist and his assistant Johanna Bakker-Heeres to 8800 BCE. They also concluded that the settlers of Tell Aswad did not develop this form of emmer themselves, but brought the domesticated grains with them from an as yet unidentified location elsewhere.
I’m particularly intrigued by that mention at the end of “from an as yet unidentified location elsewhere”…
But even here we have direct evidence of emmer at 9600 B.C. and it originated about the time the Gobekli Tepe folks where disappearing. Hmmmm….
So what makes Emmer “special”?
Wheat genetics is more complicated than that of most other domesticated species. Some wheat species are diploid, with two sets of chromosomes, but many are stable polyploids, with four sets of chromosomes (tetraploid) or six (hexaploid).
Einkorn wheat (T. monococcum) is diploid (AA, two complements of seven chromosomes, 2n=14).
Most tetraploid wheats (e.g. emmer and durum wheat) are derived from wild emmer, T. dicoccoides. Wild emmer is itself the result of a hybridization between two diploid wild grasses, T. urartu and a wild goatgrass such as Aegilops searsii or Ae. speltoides. The unknown grass has never been identified among now surviving wild grasses, but the closest living relative is Aegilops speltoides. The hybridization that formed wild emmer (AABB) occurred in the wild, long before domestication, and was driven by natural selection.
Hexaploid wheats evolved in farmers’ fields. Either domesticated emmer or durum wheat hybridized with yet another wild diploid grass (Aegilops tauschii) to make the hexaploid wheats, spelt wheat and bread wheat. These have three sets of paired chromosomes, three times as many as in diploid wheat.
So we have a regular diploid ( one copy from each parent, so two total copies of the genes) as Einkorn Wheat.
Emmer is a tetraploid, made via a hybridizing event with a wild goat grass before 10,000 B.C. and in the wild. We also see that durum wheat is similar in genetic numbers, but a different type of wheat (used in noodles ;-)
Finally, we get yet another interspecies cross that gives us the “three-fer” wheats with hexaploid gene sets. Spelt (that oddly some folks cling to as a ‘primitive wheat’ and therefor somehow ‘better’ – but actually a more recent formation than Emmer and far more recent than Einkorn) along with the more common bread wheats of today (more starch than Durum). But now we are up to 3 different species “getting together” to make the bread wheat of today. Having a “three way” has been around for a very long time… at least for plants…
Since then, humans have crossed wheat with rye to be Triticale.
E.A. Oelke1, E.S. Oplinger2, and M.A. Brinkman2
1Department of Agronomy and Plant Genetics, University of Minnesota, St. Paul, MN 55108.
2Department of Agronomy, College of Agricultural and Life Sciences and Cooperative Extension Service, University of Wisconsin-Madison, WI 53706. Nov., 1989.
Triticale (trit-ih-KAY-lee) is a crop species resulting from a plant breeder’s cross between wheat (Triticum) and rye (Secale). The name triticale (Triticale hexaploide Lart.) combines the scientific names of the two genera involved. It is produced by doubling the chromosomes of the sterile hybrid that results when crossing wheat and rye. This doubling produces what is called a polyploid.
Hybrids between wheat and rye date back to 1875, but until recently there was little effort to develop highyielding triticales as a field crop. Plant breeders originally wanted to include the combination of grain quality, productivity, and disease resistance of wheat with the vigor and hardiness of rye. The University of Manitoba began the first intensive program in North America about 30 years ago working mostly with durum wheat-rye crosses. Both winter and spring types were developed, with emphasis on spring types. Since Canada’s program, other public and private programs have initiated both durum wheat-rye and common wheat-rye crosses. The major triticale development program in North America is now at the International Maize and Wheat Improvement Center in Mexico, with some private companies continuing triticale programs; however, the University of Manitoba has discontinued its program.
Even though triticale is a cross between wheat and rye, it is self-pollinating (similar to wheat) and not cross pollinating (like rye). Most triticales that are agronomically desirable and breed true have resulted from several cycles of improvement, but are primarily from the durum-rye crosses with some common wheat parentage occasionally involved.
Now at this point we’ve got a serious set of different plant ancestors for the various wheat like grains we grow. And this is before you get into questions like what made up rye and einkorn in the first place…
But before this turns into a posting all about wheat, I’m just going to paste in a list of the different kinds of wheat in common use, and then move on to the thing that prompted this posting. Yet Another Species from an interspecies hybridizing event… But first, the wheat list from the wiki:
Major cultivated species of wheat
Common wheat or Bread wheat (T. aestivum) – A hexaploid species that is the most widely cultivated in the world.
Spelt (T. spelta) – Another hexaploid species cultivated in limited quantities. Spelt is sometimes considered a subspecies of the closely related species common wheat (T. aestivum), in which case its botanical name is considered to be Triticum aestivum subsp. spelta.
Durum (T. durum) – The only tetraploid form of wheat widely used today, and the second most widely cultivated wheat.
Emmer (T. dicoccon) – A tetraploid species, cultivated in ancient times but no longer in widespread use.
Khorasan (Triticum turgidum ssp. turanicum also called Triticum turanicum) is a tetraploid wheat species. It is an ancient grain type; Khorasan refers to a historical region in modern-day Afghanistan and the northeast of Iran. This grain is twice the size of modern-day wheat and is known for its rich nutty flavor.
Einkorn (T. monococcum) – A diploid species with wild and cultivated variants. Domesticated at the same time as emmer wheat, but never reached the same importance.
Classes used in the United States:
Durum – Very hard, translucent, light-colored grain used to make semolina flour for pasta & bulghur; high in protein, specifically, gluten protein.
Hard Red Spring – Hard, brownish, high-protein wheat used for bread and hard baked goods. Bread Flour and high-gluten flours are commonly made from hard red spring wheat. It is primarily traded at the Minneapolis Grain Exchange.
Hard Red Winter – Hard, brownish, mellow high-protein wheat used for bread, hard baked goods and as an adjunct in other flours to increase protein in pastry flour for pie crusts. Some brands of unbleached all-purpose flours are commonly made from hard red winter wheat alone. It is primarily traded on the Kansas City Board of Trade. One variety is known as “turkey red wheat”, and was brought to Kansas by Mennonite immigrants from Russia.
Soft Red Winter – Soft, low-protein wheat used for cakes, pie crusts, biscuits, and muffins. Cake flour, pastry flour, and some self-rising flours with baking powder and salt added, for example, are made from soft red winter wheat. It is primarily traded on the Chicago Board of Trade.
Hard White – Hard, light-colored, opaque, chalky, medium-protein wheat planted in dry, temperate areas. Used for bread and brewing.
Soft White – Soft, light-colored, very low protein wheat grown in temperate moist areas. Used for pie crusts and pastry. Pastry flour, for example, is sometimes made from soft white winter wheat.
Red wheats may need bleaching; therefore, white wheats usually command higher prices than red wheats on the commodities market.
I find it interesting that different exchanges trade different wheat types. This also helps to explain why home made versions of some kinds of baked goods are never quite like the commercial ones. It is very hard to get the specific kinds of flour used when the store only sells bread flour, all purpose flour, and if very lucky, cake flour. That doesn’t even cover all the main types, and forget all the sub-types and variations.
But at least now you know why different flours have different characteristics. They are different species of wheat, and with different ancestor grasses.
FWIW, I’m still not sure just which wheat it is that the food purists think is too new and has the wrong kind of gluten in it. Maybe someday I’ll get around to chasing that particular thread…
But this brings us to the actual point of this posting. Just how far apart CAN an inter-species hybrid reach? I’ve speculated that we have an orangutan / chimp cross in our ancestry (and have a bit more evidence for that for a future posting – it involves preferences for “doggy style” vs not… ). That seems like too far a gap to span, yet some species have gone further.
One Giant Leap for Fern Kind
This fern species has a gap of about 60 Million years between parents.
Distant species produce ‘love child’ fern after 60-million-year breakup
Date: February 13, 2015
Source: Duke University
A delicate woodland fern discovered in the mountains of France is the love child of two distantly-related groups of plants that haven’t interbred in 60 million years, genetic analyses show. Reproducing after such a long evolutionary breakup is akin to an elephant hybridizing with a manatee, or a human with a lemur, the researchers say.
A bit of an overstatement, as plants are far more, um, “adventuresome” in gene swapping than are mammals. Yet maybe a 6 Million year gap for primates might be a reasonable comparison. So more like a Chimp and an Orangutan…
Led by Pryer and Carl Rothfels of the University of California, Berkeley, the study appears online today and in the March 2015 issue of the journal American Naturalist.
The pale green fern was found growing wild on a forest floor in the Pyrenees and eventually made its way to a nursery, where researchers plucked several fronds and extracted the DNA to pinpoint its parentage.
To their surprise, genetic analyses revealed that the fern was the result of a cross between an oak fern and a fragile fern — two distantly related groups that co-occur across much of the northern hemisphere, but stopped exchanging genes and split into separate lineages some 60 million years ago.
“To most people they just look like two ferns, but to fern researchers these two groups look really different,” Rothfels said.
Other studies have documented instances of tree frog species that proved capable of producing offspring after going their separate ways for 34 million years, and sunfish who hybridized after nearly 40 million years, but until now those were the most extreme reunions ever recorded.
So yet another example of a ‘new species’ made from a couple of old ones. Neatly showing how the lack of “missing links” is completely irrelevant to speciation.
I’d also note that inter-species hybrids are relatively common in related fish types along with the odd dogs, wolves, coyotes, foxes et. al. There are also recorded cases of stable sheep / goat hybrids despite different chromosome counts. Usually to gain viability in mammals, there is the need to breed back to a particular parent gender to stabilize the chromosome counts. See https://en.wikipedia.org/wiki/Haldane%27s_rule for more than most folks want to know…
Now 6 million years ago when humans first showed up, Chimps and Orangutans were 6 million years closer to each other than now. Any attempt at a cross now might not work so well, even if it did then. We might not even have the right species anyway ( for my money it was a Bonobo relative in the Chimp line, as those critters are more, er, active, than the other chips and thus, IMHO, more likely to have accepted some Orangutan ‘visits’…)
But if this fern is any evidence, that species “strong suggestion” might even be more of a “demure”…
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