1. Within the genus Aegilops 9 diploid analysers have been established by the author. Their genomes are included in various combinations in the allotetraploid species of the genus.
2. The distribution area of the analysers is very limited. They are found in Asia Minor, Syria, Palestine and the Balkan Peninsula, while the whole area of the genus extends roughly along the coasts of the Mediterranean Sea (including the islands) reaching eastward to Afghanistan and Pakistan.
3. 6 allotetraploids out of 9 occupy a strikingly wider area than their corresponding analysers. For instance, Ae. triuncialis expands almost over the whole area of the genus.
4. The wide distribution of allopolyploids must have taken place at the time when there were connections between South Europe and Africa.
5. The formation of the allotetraploids must have occurred before the connecting bridges have been broken.
6. The distribution center of the 9 analysers should be considered to be the place where the hybridization was occurring.
7. Hybrid vigor seems to be the cause of the wide distribution of polyploids.
8. At present we know 9 diploid, 9 allotetraploid and 3 allohexaploid species in Aegilops. The polyploids contain a larger number of varieties than the diploid analysers. These facts indicate that the hybridization has played directly and indirectly a very important role in the evolution of the Aegilops species.
9. The genome-analysis showed that the genome C, which is included and isolated in Ae. cylindrica and also in Ae. triuncialis has been kept constant for a very long series of years. We could call this kind of crossisolation genome isolation through polyploidy. The constancy of genomes can also be inferred from the existence of the same diploid species in the Archipelago which is supposed to have been included in the mainland in earlier periods. The intra- and intervarietal hybrids between strains obtained from distant localities have definitely shown that the parents had homologous genomes.
The Japan Mendel Society