Gymnocarpium hybrids
Gymnocarpium hybrids
Translated excerpt from C.J. William 1989, Les fougères et les plantes alliées du Canada, p. 255-256
W.H. Wagner (1966b) was the first to take an interest in a plant resulting “apparently from the crossing of G. dryopteris with G. robertianum”, a new triploid apomictic species that he named G. heterosporum.
Sarvela (1978) gave this hybrid the name G. heterosporum W.H. Wagner, indicating that it resulted from the crossing G. jessoense × robertianum.
He also described a new hybrid, G. intermedium (G. dryopteris × jessoense). Pryer (1981) reports that G. × intermedium is common where G. jessoense ssp. parvulum grows, but it is a triploid, not a tetraploid as we would expect, which makes him say that the parents are G. dryopteris ssp. disjunctum (2x) and G. jessoense ssp. parvulum (4x).
All the Gymnocarpium hybrids are recognized by the fact that most of their spores aborted. They do, however, produce some large, spherical spores that germinate and we believe that this is how they multiply, by an apomictic process, although no one has so far succeeded in growing plants to maturity. Note that if our hypothesis is correct, these hybrids are much more difficult to study than those of the genus Dryopteris, because they could have been produced at very different times and in very distant places as they are currently.
We find very large colonies of Gymnocarpium × intermedium north of the lake Superior. In some places this hybrid is much more abundant as G. jessoense ssp. parvulum.
Sarvela (1980) also described the hybrid G. dryopteris ssp. brittonianum which would result from the crossing G. dryopteris ssp. disjunctum × ssp. dryopteris. It is easy to identify and seems abundant. In this case again, we know that it is a hybrid because most of its spores abort and it reaches a larger size that the ssp. dryopteris. As with the parents, the blade is glabrous.
Pryer (1981) believes that it can also multiply by an apomictic process thanks to the few large spores it produces. We found it across Canada (Sarvela, 1980; Pryer, 1981).
Finally, let us mention G. × achriosporum Sarvela (G. dryopteris × robertianum). Hybrids of G. robertianum seem rare. The type was described based on specimens found in Sweden.
In North America, only two specimens correspond to this description; they come from Chicoutimi and Gaspé, in Quebec (Sarvela, 1981). We have not yet studied the cytological situation of this hybrid, but it should be a tetraploid, since both of its parents are tetraploids themselves.
Gymnocarpium X heterosporum is only known from type specimens found in North America; we also have it reported from one location in Finland (Sarvela, 1978). It has never been seen in Canada (Sarvela, 1980).
therein cited literature:
Pryer, K.M. 1981. Systematic studies in the genus Gymnocarpium Newm. in North America. M. Se. thesis, University of Guelph, Guelph, Ont. 166 pp.
Sarvela, J. 1978. A synopsis of the fern genus Gymnocarpium. Ann. Bot. Fenn. 15:101-106.
Sarvela, J. 1980. Gymnocarpium hybrids from Canada and Alaska. Ann. Bot. Fenn. 17:292-295.
Sarvela, J.; Britton, D.M.; Pryer, K. 1981. Studies on the Gymnocarpium robertianum complex in North America. Rhodora 83:421-431.
Wagner, W.H. 1966b. New data on North American oak ferns, Gymnocarpium. Rhodora 68:121-138.
