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with higher humidity, while the second group has retreated to the same places (Гонча-
ров, 1944). Today these populations are highly influenced by the economic activities of
Man mainly by ploughing the soils and their utilization as arable land. These relict
species form open and genetically unstable populations with restricted capabilities for
distribution. Unfortunately measures for their protection are not undertaken.
Some
Astragalus
species have secondary enlarged their distribution area as a
consequence o f the deforestation in the Danube Plain and the Ludogorie region. These
species have crossed the range of the Stara Planina Mts., most probably in its eastern
lower part, and were preserved on calcareous, rocky and sandy terrains in the Znepole
region, the Thracian Plain, the Tuudza Hilly Plain (Fig. 2). In Southern Bulgaria this
group includes
Astragalus pubijlorus
, /1.
dasyanthus
,
A. asper
,
A. pouficus
and
A. vest-
carius
with small in size populations.
The same migration direction is observed for the widely distributed species
A.
onobrychis.
This Euro-Siberian steppe element is rather polymorphic and possesses a
high ecological plasticity (P av lova , 2003). That’s why it has succeeded to pass the
forest-steppe zone and
irradiate
in Bulgaria and
in
Central Europe.
On such secondary steppe terrains are found the Balkan endemics /1.
wilmottianus
Stoj. and
A. spntnen,
showing the closest morphological similarity with the primitive
syndrome of the middle Asiatic species
A. manspessulamis
L.. This group of relatively
young species has originated in the mountainous and semi-mountainous areas of the
Balkan Peninsula.
Other
Astragalus
species reached Bulgaria migrating along the classical south -
politic route, They demonstrate the connections of our flora with the steppe areas in
Eastern Thracia, a continuation of the steppes in Asia Minor. An example is the species
A. gladiatlms
which is a macedonian-thracian-anatolian geoelement, Quite possibly its
area in former times was larger in southeastern direction, covering pail of the territory of
Turkey. This supposition is based on its close morphological similarity with the endemic
turkish species
A. aucheri
Boi s s . The possibility for the past existence of other closely
related species distributed in the Iran-Turanian area, unknown or extinct, should not be
excluded.
The species of genus
Astragalus,
which have reached the highest level in the
evolutionary process towards xeropbytizatiou, are of special interest. The analysis o f the
distribution patterns and the endemic processes in the group of the spiny representatives
of
Astragalus
reveals their most probable origin in the Pamir-Himaiayan center, They
show considerable migrations to the east and the west. Their migration capabilities are
comparatively weaker as typical xerophytes, so that relict types from the ancient
Mediterranean basin are rarely observed. A representative of this group in the Bulgarian
flora is
A. augustifoftus
Lam. bound to the ecological requirements of calcareous
terrains. Most of its communities are secondary in origin (Велчев. Василев, 1984) on
the place of the former tree vegetation destroyed by the humans. The considerable
displacement in the vertical distribution
oiAstragalus
on the Balkan peninsula up to 2100
m linked with its infraspecific variation are a result of acive specialion processes during
the interstadial migrations and tendency for polyploidization (Pavl ova, 2003).
Similar migration and evolutionary processes have taken place in subgen.
Tragacantha
Bunge (Pod l ech, 1986). This subgenus is poorly represented in the
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