Special Origins
All North American Drosera species except for D. anglica have a chromosome count of 2n=20. In 1955, Wood noted that D. anglica had a chromosome count of 2n=40, and hypothesized that it was of hybrid amphidiploid origin. Since the leaf morphology of D. anglica is an intermediary between that of D. rotundifolia and D. linearis and the two occur sympatrically in several locations, Wood conjectured that D. anglica likely originated from a hybrid between these two.
All North American Drosera species produce sterile hybrids. The natural hybrid D. rotundifolia × D. linearis (conventionally but incorrectly referred to as Drosera ×anglica), is also sterile but is morphologically similar to the modern D. anglica. Errors in meiosis during ovule and pollen production, however, can result in a chromosome doubling which can allow for viable seed to be produced. The resulting plants, known as amphiploids, would be fertile. Woods noted that this appeared to be an ongoing process with D. anglica speciating from D. rotundifolia × D. linearis through amphidiploidy in multiple locations. The question remains as to why D. anglica is so widespread, whereas the range of D. linearis is limited to the Great Lakes region of North America. The greater adaptability of D. anglica to varied habitat conditions could be a major factor.
Read more about this topic: Drosera Anglica
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