Genetic variation in an isolated population of Hymenophyllum ...

G. Colling & S. Hermant Genetic variation in an isolated population of Hymenophyllum tunbrigense
Genetic variation in an isolated population of
Hymenophyllum tunbrigense
Introduction
We studied the genetic structure of an isolated
population of the extremely rare fi lmy fern Hymenophyllum
tunbrigense that occurs in the sandstone
area near Berdorf in Eastern Luxembourg. We
sampled a total of 20 leaves along 3 transects in a
gorge containing the largest known Luxembourg
population (Figs 1; 2). Plants at three rock faces
were considered as diff erent subpopulations. The
genetic variation among samples was tested using
the RAPD method (Fig. 3).
Fig. 1: Sampling of Hymenophyllum tunbrigense leaves
in a large sandstone gorge near Berdorf. Photo: Mnhnl.
Ferrantia • 44 / 2005
Guy COLLING & Sylvie HERMANT
Musée national d’histoire naturelle, Service biologie des populations
25, rue Münster, L-2160 L-2160 Luxembourg
Luxembourg
guy.colling@mnhn.lu
Height (m)
Y (m)
5
4
3
2
1
0
0 2 4 6 8
X (m)
Fig. 2: Schematic representation of the transect sampling
of leaves of H. tunbrigense in the rock face shown
on Fig. 1. X: distance from an arbitrary starting point.;
Y: height above same arbitrary starting point.
Fig. 3: Electrophoresis gel showing RAPD band patterns
from three distinct subpopulations of Hymenophyllum
tunbrigense. Each column corresponds to one individual.
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G. Colling & S. Hermant Genetic variation in an isolated population of Hymenophyllum tunbrigense
90
Table 1: Summary of analysis of molecular variance (AMOVA). Plants represented 3 subpopulations of
Hymenophyllum tunbrigense. The analysis is based on RAPD phenotypes consisting of 24 band
states. Levels of signifi cance are based on 1000 iteration steps.
Level of variation df Variance component
RAPD variation of populations
and gene fl ow
There was strong genetic diff erentiation (RAPD
pa pa pa pa erns) erns) among subpopulations (24% of total
variation) (P (P < 0.001) (Tab. 1). The strong genetic
variation among subpopulations and the mean
number of individuals exchanged between
subpopulations per per generation generation (N
(N = 0.78)
em
indicates that that gene gene fl fl ow ow between between subpopulations
subpopulations
is low. The pairwise genetic distances (Phi
ST) were
signifi cant between all subpopulations (P (P < < 0.001).
0.001).
UPGMA cluster analysis based on Nei’s distances
between RAPD phenotypes clearly separated the
three subpopulations subpopulations (Fig. (Fig. 4). 4). A A possible possible explaexpla-
nation for for the the observed observed genetic genetic diff diff erentiation is is a
restricted dispersal of the spores (Fig. 5).
Conclusions
Our results show that the three subpopulations
forming together the largest Luxembourg
Absolute % P
Among subpopulations 2 0.939 24.27

G. Colling & S. Hermant Genetic variation in an isolated population of Hymenophyllum tunbrigense
Résumé de la présentation
Variation génétique dans une population isolée d’Hymenophyllum tunbrigense
Nous avons étudié la structure génétique d’une
population isolée d’Hymenophyllum tunbrigense, une
fougère extrêmement rare que l’on trouve dans la zone de
grès près de Berdorf, à l’Est du Luxembourg. Nous avons
collecté un total de 20 feuilles le long de 3 transects, dans
une gorge contenant la plus grande population luxembourgeoise
connue. Les individus, issus de trois parois
rocheuses, sont considérés comme des sous-populations
distinctes. On a testé la variation génétique au sein des
échantillons à l’aide de la méthode RAPD.
La diff érentiation génétique au sein des sous-populations
est forte (empreintes RAPD) (24% de la variation totale)
(P

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Ferrantia • 44 / 2005