Revue internationale d'écologie méditerranéenne International ...

size class with box plot charts. MDNN values
(according to four classes: 1 < 5001 m;
2 = 5001 – 10000 m; 3 = 10001 – 15000 m;
4>15000 m) were also projected on the distribution
map of the populations. Significant
differences between population size classes
for altitudes and MDNN were tested by a
bonferroni procedure (Hervé 2007) at the
alpha 5% risk after correction.
Results
We updated the cartography of G. lobelii providing
a nearly exhaustive distribution of the
populations (Figure 1, Appendix 1). After
three years of field investigations, we did not
find two populations previously cited at “Forcalquier”
and “Mont Coudon” sites (Rebuffel
1998). We report five new populations, never
cited previously on: Carpiagne mountain
(CRP3), Garlaban mountain (GRL8), la
Loube mountain (LB3), and Reigagnas mountain
(TRT1). In addition, we found on Grand
Bessillon site (BSS) a population which has
not been observed by botanists since 1992
(Rebuffel 1998).
Genista lobelii occurs on a relatively large
geographical range though with a highly frag-
ecologia mediterranea – Vol. 36 (1) – 2010
Distribution, habitat and population size variation of Genista lobelii (Fabaceae)
from the calcareous mountains of Basse Provence (S-E France)
mented pattern. The stations are mainly
localised on the summits of the principal calcareous
mountains of Basse Provence. Even
at the scale of each mountain, the populations
are often highly scattered. The most extreme
pattern of isolation is observed for peripheral
sites of Bessillon and cap Canaille with small
patches of individuals, i.e. 10 individuals on
10 m 2 and 15 individual on 20 m 2 respectively.
The median distance to the nearest
20 neighbors (MDNN) are 26.3, 21.1 and
16.6 km for Bessillon (BSS), Mont Faron
(FRN) and cap Canaille (CNL) stations
respectively (Appendix 1). On the other hand,
near the center of the distribution, along the
Sainte-Baume (BM) and Sainte-Victoire
(VCT) summits, G. lobelii occupies a large
area of close stations (Figure 1). The average
MDNN is 2.6 and 4.1 km for Sainte-Victoire
(VCT) and Sainte-Baume (BM) stations
respectively (appendix 1). The average
MDNN is 12.4 km for all 108 G. lobelii stations.
These patterns are also summarized on
boxplots (Figures 2 and 3), showing that the
highest population size class (>1000 m 2 ) is
significantly associated to small isolation
(small values of MDNN) and to high altitudes.
However, there was no significant difference
between population size classes 1
and 2.
Figure 2 – On left: box plot of median distance (m) of 20 most nearest neighbors of Genista lobelii stations according to surface area
occupied (three classes: 1 = surface area < 100 m 2 ; 2 = surface area 100 m 2 – 1000 m 2 ; 3 = surface area > 1000 m 2 ). Different
letters show significant median distance of 20 most nearest neighbors differences between population size categories at
the alpha 5% risk after Bonferroni correction. On the right: spatial distribution map of G. lobelii, the symbol sizes
proportional to the median distance of 20 most nearest neighbors (four classes: 1 < 5001 m; 2 = 5001-10000 m;
3 = 10001-15000 m; 4 > 15000 m).
69