Dryopteris × leedsii

Dryopteris × leedsii
Scientific classification
Kingdom: Plantae
Clade: Tracheophytes
Division: Polypodiophyta
Class: Polypodiopsida
Order: Polypodiales
Suborder: Polypodiineae
Family: Dryopteridaceae
Genus: Dryopteris
Species:
D. × leedsii
Binomial name
Dryopteris × leedsii

Dryopteris × leedsii (Leeds' wood fern) is a hybrid fern native to eastern North America. It is the sterile offspring of the log fern (D. celsa) and the marginal wood fern (D. marginalis).

Description

Taxonomy

The first known collection of Leeds' wood fern was in 1928 by E. J. Palmer near Shirley, Arkansas.[1] The "Palmer Dryopteris" was frequently recognized as having some affinity to D. celsa, but its precise identy remained a mystery for many years.[2] In 1931, Arthur N. Leeds discovered a large colony of hybrid wood ferns below the Conowingo Dam in Harford County, Maryland.[3] It was initially thought to be the hybrid between Goldie's wood fern (D. goldieana) and D. marginalis.[4] It was described as such and given the name D. × leedsii in 1942 by Edgar T. Wherry. The type specimen is a 1931 collection by Leeds deposited at the Academy of Natural Sciences of Philadelphia.[3]

Further confusion was generated when samples gathered at the type site in 1954 were sent to Stanley Walker for chromosome counts, and proved to be a mixture of abortive-spored hybrids and fertile tetraploids.[5] The fertile plants were taken to be allopolyploids formed by chromosome doubling of the hybrid, and described as Dryopteris wherryi in 1960.[6] However, further work by Walker revealed that the hybrids, initially thought to be diploid, appeared to be largely triploid, which would not be expected of a D. goldieana and D. marginalis.[a][7] Furthermore, lack of chromosome pairing after artificial backcrossing suggested that D. wherryi was not an allopolyploid derived from D. marginalis.[b][8]

In 1963, Herb Wagner suggested that D. × leedsii was probably the triploid hybrid of D. marginalis and D. celsa (an allotetraploid) rather than D. goldieana[9] on the basis of studies done with Wherry at the type locality. Wagner and his wife Florence also found a new station for the hybrid in Monroe County, New York in 1964.[10] The Wagners concluded that the specimens described as "D. wherryi" were in fact D. celsa and parents to D. × leedsii, and described the true hybrid of D. goldieana and D. marginalis, from other locales, as D. × neowherryii.[11] The hybrid was subsequently found in Pennsylvania, and the "Palmer Dryopteris" was rediscovered by Carl Taylor and Delzie Demaree in 1974[2] and confirmed to be D. × leedsii.[1]

Distribution and habitat

The parents of Dryopteris × leedsii overlap broadly in range (if not habitat) in the eastern United States. The hybrid is known from New York, New Jersey, Pennsylvania, Maryland, and Virginia, and disjunctly in Arkansas.[12]

Notes and references

Notes

  1. ^ Both D. goldieana and D. marginalis are diploid, so hybrids of a cross between them would normally be diploid, with a set of chromosomes from each species.
  2. ^ If half of the D. wherryi genome was recently derived from D. marginalis, those chromosomes would be expected to pair up during meiosis in a hybrid between the two.

References

  1. ^ a b Wagner & Taylor 1976, p. 228.
  2. ^ a b Wagner & Taylor 1976, p. 225.
  3. ^ a b Wherry 1942, p. 2.
  4. ^ Wherry 1942, p. 1.
  5. ^ Walker 1959, p. 108.
  6. ^ Crane 1960, p. 271.
  7. ^ Walker 1962, p. 971.
  8. ^ Walker 1962, p. 974.
  9. ^ Wagner 1963, p. 150.
  10. ^ Wagner & Wagner 1965, p. 65.
  11. ^ Wagner & Wagner 1966, p. 136.
  12. ^ Kartesz 2014.

Works cited

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