Revue internationale d'écologie méditerranéenne International ...

SAMI YOUSSEF, ERROL VELA, ALEX BAUMEL, THIERRY TATONI
Figure 3 – Box plot of the distribution of G. lobelii stations on altitudinal
gradient (m) 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
altitudes differences between population size categories at the
alpha 5% risk after Bonferroni correction.
Table 1 – The demographic strategies, biological traits and biogeographical
distribution of all stations and each cluster of stations.
Demographical strategies sensu Grime (1974) (C: Competitor;
R: Ruderal; S: Stress-tolerant); biological traits sensu Raunkiaer
(1934) (Ch: Chamaephytes; G: Geophytes; H: Hemicryptophytes;
P: Phanerophytes; Th: Therophytes); biogeographical distribution
sensu Pignatti (1982) (Steno-Medit: Mediterranean sensu stricto;
Euri-Medit: Mediterranean sensu lato; Medit-Mont: Mediterranean
mountains; Oroph: European Orophytes).
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All stations Cluster n o 1 Cluster n o 2 Cluster n o 3
nb of stations 108 52 39 17
Ch 40% 39% 43% 38%
G 4% 5% 2% 1%
H 29% 31% 28% 24%
P 12% 9% 15% 20%
Th 15% 16% 12% 17%
C 3% 5% 4% 3%
CR 1% 0% 0% 3%
SC 16% 14% 15% 20%
SCR 3% 1% 4% 5%
R 1% 1% 1% 3%
S 54% 55% 51% 45%
SR 25% 24% 25% 21%
Endemic 2% 1% 2% 2%
Sub-endemic 3% 6% 3% 2%
Steno-Medit. 32% 21% 39% 46%
Euri-Medit. 17% 19% 15% 16%
Medit.-Mont. 21% 23% 16% 17%
Oroph 9% 10% 8% 4%
Eurasiatic 9% 10% 11% 7%
Steppic 3% 4% 1% 1%
Subcosmopolite 1% 4% 2% 3%
Subtropical 1% 0% 0% 0%
Boreal 1% 1% 1% 0%
Xenophyte 0% 0% 0% 1%
Subatlantic 1% 1% 2% 1%
A total of 263 species were observed with
G. lobelii over all the 108 stations, their characteristics
are summarized in Table 1. We
observed an important variability between stations
because only 51 species are present in
at least 25% of the stations and 68 species
occur only in one or two stations. Three
Grime strategies, “stress” (S), “stress competitive”
(SC) and “stress ruderal” (SR), represent
95% of all plant species and the biological
spectrum of Raunkiaer shows that the
community associated with G. lobelii is
mainly represented by Chamaephytes and
Hemicryptophytes (C + H = 69%). In addition,
the spectrum of biogeographical distribution
shows that the Mediterranean species
(Steno + Euri = 49%) are predominant but
Mediterranean mountains plants species and
south-european orophytes are also consequent
(21 + 9 respectively = 30% in total), while
sub-cosmopolite taxa are rare (1%). The only
one exotic species found in our relevés is
Cedrus atlantica (Manetti ex Endl.) Carrière
trees. Five percent of the species encountered
in the G. lobelii stations are endemic or subendemic
(Table 1).
Classification by CAH and ordination by
NMDS (2 axis, stress value = 17%) (Figure 4)
revealed three groups of station significantly
distinct (p < 0.01, mrpp test). The first group
is characteristic of the stations situated at 800
meters or higher in altitude, on crest and summits.
In this type of habitat, Mediterranean
mountains plants and orophytes plant species
(33% of all plant species) are very frequent
such as: Iberis saxatilis, Santolina chamaecyparissus
(L.) subsp. chamaecyparissus,
Anthyllis montana, Seseli galloprovinciale
Reduron, Teucrium polium subsp. aureum
(Schreb), Valeriana tuberose, Crepis albida
and Scorzonera austriaca subsp. bupleurifolia
(Pouzolz) Bonnier (see Appendix 2.1 for
more detail). Moreover, the Chamaephytes
and Hemicryptophytes stress-tolerant species
dominate forming fruticose or dwarf cushion
vegetation characterised by the dominance of
G. lobelii. In this plant community, we
observed 7% of endemic and sub-endemic
species. It should be noted that this cluster
(n o 1) is situated at the geographical center of
G. lobelii population distribution. In the second
group, the stations are situated between
500 to 800 m (a.s.l.). Within this group, the
Mediterranean mountains plants and orophytes
species are less abundant (24%) and
the most frequent species are: Rosmarinus
officinalis L., Aphyllanthes monspeliensis L.,
ecologia mediterranea – Vol. 36 (1) – 2010