A re-evaluation of plants referred to as Pteridium herediae (Colmeiro) Löve & Kjellqvist

Abstract

SHEFFIELD, E., WOLF, P. G., HAUFLER, C. H., RANKER, T. A. & JERMY, A. C, 1989. Are‐evaluation of plants referred to as Pteridiutn herediae (Colmeiro) Love & Kjellqvist. Based on perceived differences in morphology, chromosome number and habitat, specimens of Pteridiutn from southern Spain have been segregated by previous authors as a species distinct from Pteridium aquilinum, and called Pteridium herediae. However, type specimens of this taxon cannot be found. New collections of Pteridium from similar habitats in the area were examined and analysed in the present study and the results compared with those from British plants (P. aquilinum). The Spanish plants were not found to differ significantly from P. aquilinum morphologically, and all yielded chromosome counts (sporophytes, 104; gametophytes, 52) considered typical for the genus. Genotype frequency data obtained from isozyme electrophoresis of Spanish and British Pteridium yielded a genetic identity of 0.86; well within intraspecific distances found in other ferns. These data indicate that there are currently no grounds for accepting that a form of Pteridium, distinguishable from P. aquilinum on the basis of differences in morphology, chromosome number, habitat or biochemistry, exists on the limestone soils of the Sierra de Cazorla region of southern Spain.

The taxa of Scottish bracken in a European perspective

“…Cliff. 473, Pteris 6), which is again typical of the southern, 'midlatitude' plant, here referred to as P. aquilinum although, as was stated by Sheffield et al (1989), it represents a juvenile state of that taxon. Consequently, there is no conflict between the two typifications of the name Pteris aquilina: both refer to the same taxon, i.e.…”

“…February, 1995. It must be mentioned here that the specimens labelled Pteris aquilina L. presently in the Linnaean Herbarium (LINN 1246(LINN .13, 1246, the latter being a small fragment of a frond), do not represent Pteridium aquilinum as lectotypified by Sheffield et al (1989). Instead, they have the distinctive morphological characteristics of P. pinetorum.…”

“…However, Tryon failed to point out that the polynomial Pteris fronde supradecomposita: foliolis pinnatis: pinnis lanceolatis: infimis pinnatifidis: superioribus minoribus, to which Linnaeus (1753) attached the epithet aquilina, was first used by him in the Hortus Cliffortianus (Linnaeus, 1738), and again in the Flora Suecica (Linnaeus, 1745). Sheffield et al (1989) drew attention to this point and to the fact that it had nomenclatural implications as it suggested that herbarium material of Pteris aquilina, to which Linnaeus would have had access during his visit to Holland in 1736 (Steam, 1957), might be present in the Clifford Herbarium (now at BM) and would, if so, invalidate Tryon's choice of the 1542 Fuchs plate. Such material does indeed exist.…”

“…Such material does indeed exist. Two specimens are present: one is a specimen collected by Gronovius, of North American (New England) origin, which is 'typical of material from that area' (Sheffield et al, 1989) and presumably therefore belongs to either P. latiusculum (the common bracken of that area) or P. aquilinum var. pseudocaudatum (Clute) A. Heller, which is more sporadic (Jacobs & Peck, 1993).…”

“…In recent years, the monotypic view of the species has been increasingly challenged, as morphological variation, combined with evidence from other independent disciplines has shown the existence of different morphotypes, cytotypes and genotypes, especially where associated with different chromosome levels (see Page, 1976, for a summary of these) and molecular signatures (e.g. Jubrael, Sheffield & Moore, 1986;Sheffield et al, 1989;Rumsey, Sheffield & Haufler, 1991).…”