Revue internationale d'écologie méditerranéenne International ...

LAURENT HARDION, ALEX BAUMEL, PIERRE-JEAN DUMAS, NATHALIE DUONG, LAURENCE AFFRE & THIERRY TATONI
Figure 1 – Neighbor-joining distance tree based on a matrix of 49 nrDNA ITS
sequences. Branch lengths are proportional to distances estimated
from Kimura two-parameter distance. Numbers are bootstrap
values for 5000 replicates (values below 50% not indicated).
Clades are identified by letters based on previous molecular
studies (Wojciechowski et al. 1999; Kazempour Osaloo et al. 2005).
102
Astragalus
sensu stricto
Astragalean clade
0.02
C
96
95
79
86
74
75
80
95
60 A. tragacantha Ga1
69 A. tragacantha Ga2
88 A. tragacantha Ga3
94
A. tragacantha Ga4
A. tragacantha Co1
A. tragacantha Co2
A. fragrans
A. odoratus
A. uliginosus
100
A. oreganus
67
A. canadensis
70 A. falcatus
A. depressus
A. cymbicarpos
A. hamosus
A. boeticus
A. edulis
A. glycyphyllos
51
99 A. sinicus
A. complanatus
A. alpinus
A. lamprocarpus
D
A. compactus
89
A. brachycalyx
58 A. cicer
79
A. pulchellus
A. glaux
A. austriacus
64
A. echinatus
A. oophorus
65
A. patagonicus
69
95 A. arizonicus
B
A. siliquosus
89
A. williamsii
99 A. australis
A. chinensis
A
A. vulcanicus
85
A. alopecias
99
A. jessenii
83
74 A. alopecurus
A. kirrindicus
78 A. tawilicus
88 A. dictyolobus
A. epiglottis
65
Oxytropis aucherii
99 Oxytropis splendens
A. yatungensis
92
Lessertia herbacea
Melilotus alba
Neo-Astragalus
Coluteoid clade
A. tragacantha
Vicioid clade
Comparative analysis
In order to compare Astragalus tragacantha
to its nearest relatives according to our phylogenetic
results, different comparative characters
were chosen due to their pertinence to
separate or gather at best studied taxa. In
accordance with Podlech, pubescence
(Podlech 1982) and life cycle (Podlech 1991)
can be discriminatory criteria for Astragalus
phylogenies based on morphological characters.
Wojciechowski et al. (1993) observe correlation
between some clades and chromosome
numbers. Pod length is a morphological
character available from literature for many
species and linked to reproduction. Lastly,
habitat, distribution, and altitude are ecological
and biogeographical criteria which illustrate
the repartition of these astragals.
Results
Including total gaps, length of the aligned
sequences measure 614 bp. This data set contains
223 variable sites. At an interspecific
level, and excluding out-group, the maximum
pairwise P distance (% of nucleotidic differences)
is located between Astragalus epiglottis
and A. edulis (11.3%) and the minimum
between A. complanatus and A. sinicus (0%).
The average overall pairwise distance is 7.6%.
The maximum parsimony and the neighbor
joining (NJ) methods produce similar phylogenies,
and weak dissimilarities between them
are not significant for our study. Therefore we
show only the NJ tree (Figure 1). Coluteoid
clade (with A. yatugensis), a robust gathering
of different species, and Oxytropis (associated
with A. epiglottis) are located into the Astragalean
clade, next to Astragalus sensu stricto,
which contains four well supported clades: A
(bootstrap value of 85%), B (89%), C (96%)
and D (89%). The six sequences of Astragalus
tragacantha are closely gathered in clade C,
with twelve other non-thorny species, and one
of them, Astragalus glycyphyllos, is firmly
attached to the base of clade.
The MP tree (Figure 2) was performed using
a matrix of 18 sequences with a length of 418
bp. Because it does not contain any parsimonious
sites, the 5.8 S region was deleted for
these analyses. In this data set, 28 sites were
parsimoniously informative. Branch and
ecologia mediterranea – Vol. 36 (1) – 2010