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The Fern Gazette Volume 18 Part 1

Published 5th May 2007


Edited by M. Gibby & A. Leonard


MAIN ARTICLES

The species and subspecies in the Dryopteris affinis group
C.R. Fraser-Jenkins pg(s) 1-26
ABSTRACT
Following discussion of the different levels of variation and the ranking of the taxa, “morphotypes” have been replaced with formal names. The main taxa within the Dryopteris affinis aggregate in Europe, formerly treated as subspecies of D. affinis, are treated as six species, while the former geographical varieties are treated as nine subspecies belonging to three of the species. Seven new combinations are made at the subspecific rank and two new subspecies are described. A new species-name, D. iranica Fras.-Jenk. replaces D. wallichiana subsp. coriacea (Fras.-Jenk.) Fras.-Jenk. Four hybrids between the D. affinis agg. and D. filix-mas are treated at the nothospecific rank, two of them new and a third a new combination. Two of the hybrids are divided into six nothosubspecies, three of them new. A detailed key and comparative diagnostic descriptions are given, but it is not intended here to discuss the proposed different origins for the taxa and the evidence for those origins.
Selaginella agastyamalayana (Selaginellaceae: Pteridophyta), a new species from south India
Raju Antony, A.E. Shanavas Khan & G. Sreekandan Nair pg(s) 27-29
ABSTRACT
Selaginella agastyamalayana, a new species (Selaginellaceae: Pteridophyta) is described from Kerala, South India.

Dynamics of long-distance dispersal: the spread of Asplenium adiantum-nigrum and Asplenium trichomanes (Aspleniaceae: Pteridophyta) on London walls
J.A. Edgington pg(s) 31-38
ABSTRACT
Asplenium adiantum-nigrum L. and A. trichomanes L. have spread widely across inner London since about 1995 but have not yet colonised the district uniformly. The spacing between sites, and evidence that at most a few founding populations are involved, suggests that a sequence of long-distance dispersal events is responsible. A simple model of dispersal is proposed which predicts an exponential distribution of nearest-neighbour distances. The combined data for both species yield a good fit to such a distribution and a value of approximately 0.75 km for the mean distance between a newly-established sporophyte and the nearest potential parent plant. This leptokurtic distribution accounts for some offspring growing 5 km or more from their parent while the populated zone expands at up to 1 km per year. Assumptions underlying these conclusions are examined.

BOOK REVIEWS

Change in the British flora 1987-2004 (a report on the BSBI local change survey)
M.E. Braithwaite, R.S. Ellis & C.D. Preston pg(s) 30

The website of the British Pteridological Society