The Fern Gazette Volume 17 Part 1

Published 1st January 2004


Edited by M. Gibby & A. Leonard


MAIN ARTICLES

What is the minimum area needed to estimate the biodiversity of pteridophytes in natural and man-made lowland forests in Malaysia and Singapore?
F. B. Yusuf, B.C. Tan & I.M. Turner pg(s) 1-9
ABSTRACT
The present studies show that in man-made forests, six 10 m x 10 m quadrats are sufficient to give a good representation of the species diversity, as the comparatively uniform environment can provide a suitable habitat for only a limited number of species. Contrastingly, nine 10 m x 10 m quadrats are still not sufficient to capture the characteristic diversity of pteridophytes in natural forest habitats. This is due to the highly scattered distribution patterns of forest herbs, including the pteridophytes, along different gradients and microhabitats in the forest. In order to estimate the diversity of pteridophytes in natural forests more accurately, a minimal sample size of more than nine 10 m x 10 m quadrats needs to be established.
Morphometric analysis of variation among three populations of Doryopteris ludens (Adiantaceae: Pteridophyta) in Thailand
T. Boonkerd pg(s) 11-19
ABSTRACT
Morphological variation within populations and among populations was examined in three populations of Doryopteris ludens from western and peninsular Thailand. Sixteen quantitative characters of both vegetative and reproductive characters were scored. The field data were analysed by means of cluster analysis and various discriminant analyses. Cluster analysis and canonical discriminant analysis indicated two groups. It is consequently concluded that there are two morphological varieties which that can be distinguished on the basis of sporangium length, sporangium width, fertile-frond sinus-depth, fertile-lamina width and habitat. A conventional identification key is provided, which is based on fertile-frond sinus-depth, sporangium length, and substrate conditions.

The current status and distribution of the Falkland Islands Pteridophyte flora
D.A. Broughton & J.H. McAdam pg(s) 21-38
ABSTRACT
The Falkland Islands are an archipelago of 782 islands situated in the South Atlantic Ocean. They have a relatively depauperate native flora of vascular plants comprised of 171 species, 18 of which are pteridophytes. The pteridophyte flora includes a further three non-native taxa. Current knowledge of all pteridophyte taxa occurring in the Falkland Islands is reviewed and the first detailed data on their distribution throughout the archipelago are presented.

The importance of recent population history for understanding genetic diversity in threatened species, with special reference to Dryopteris cristata
U. Landergott, G. Kozlowski, J. J. Schneller & R. Holderegger pg(s) 39-51
ABSTRACT
The maintenance of genetic diversity and stochastic losses of diversity during periods of small population size have become major points of concern in conservation biology. However, empirical research on random evolutionary processes in natural plant populations is still scarce and is reviewed here in comparison to our case study on Dryopteris cristata. Detailed recent population histories of this wetland fern have been documented in Switzerland. We found that the lack of correlation between present-day genetic diversity and current population size in this fern, as well as in other newly rare and endangered plant species, is best explained by recent population histories.
    Genetic diversity is strongly affected by genetic bottlenecks, which resulted in a loss of about 40% of genetic variation even in the long-lived allotetraploids D. cristata and a Hawaiian silversword. In contrast, distinct reductions in population size did not severely reduce genetic diversity in populations of the latter two species in the short-term. Accordingly, there was almost no spatial genetic substructure in populations of D. cristata. However, evidence for genetic drift was found in small populations of D. cristata and has also been reported for flowering plant species, indicating that small populations are nevertheless prone to random losses of genetic diversity in the long-term. This short review elucidates the importance of recent population history for both population genetics and conservation biology. Understanding population history can substantially improve predictions on the genetic diversity in remnant populations of threatened species. Further studies on natural populations of plant species with different life cycles and ploidy levels remain valuable. .

BOOK REVIEWS

A modern multilingual glossary for taxonomic pteridology
D.B. Lellinger pg(s) 10

FERNS FOR THE 21ST CENTURY

An invitation to an International Pteridophyte Symposium pg(s) 20

The website of the British Pteridological Society