
Discussion
Distribution and Hosts
Unlike most species of Arceuthobium, which tend to
be relatively host specific (Hawksworth and Wiens 1996), A.
oxycedri has a wide host range (Table1
and Table 2). The most commonly
reported hosts are various Juniperus species. Seventeen
taxa of Juniperus are reported as host plants including
several exotic species (e.g., Juniperus virginiana, a
North American species reported as a host in the Ukraine). These
data suggest that virtually any species of Juniperus is
a potential host of A. oxycedri. Other genera of the family
Cupressaceae, including species of Chamaecyparis, Cupressus,
and Platycladus are also hosts of A. oxycedri.
It is interesting to note that the other two known Juniperus
infesting species of Arceuthobium, A. azoricum
of the Azores Islands (Portugal) and A. juniperi-procerae
of Ethiopia and Kenya, each have only a single reported host
(Hawksworth and Wiens 1976, 1996).
Arceuthobium oxycedri is confirmed from 31 countries,
including 2 in northern Africa, 4 in Mediterranean Europe, 8
in the Balkan Peninsula, 9 from Russia and other former Soviet
Republics, 5 in the Near East, and 3 from the Indian subcontinent
and western China (Map 13). One
country, Afghanistan, is considered questionable. There is also
a possibility of the additional occurrences of this dwarf mistletoe
in parts of northern Pakistan and the Himalayan Region of India,
Nepal, and Bhutan (Map 13). This
dwarf mistletoe is found over a wide elevation range, from near
sea level along the Mediterranean and Black Seas to elevations
from 575 to 1,000 m in Italy, 700 to 900 m in Iraq, 2,600 m in
northern India and 3,000 to 3,500 m in western China. Geographically,
there appear to be two broad patterns of regional distribution-dispersed
or restricted. It appears to be widely dispersed throughout the
range of its host plants in northern Africa, Spain, the Balkans,
Turkey and adjacent countries, central Asia, and southwestern
China. Its distribution is more restricted in France, Italy,
Pakistan, and India. Some differences may arise from the intensity
of collecting, but mistletoes commonly exist as isolated populations.
Interest in the A. oxycedri seems especially keen in Spain,
Crimea, and Pakistan. Its broad distribution suggests climate
is usually not limiting if a juniper host is present. The range
of this dwarf mistletoe appears to generally coincide with its
hosts, but the junipers themselves occur in many regions as widely
separated populations. Although the ballistic dispersal of dwarf
mistletoes assures good local spread, its dioecious habit and
rare vectoring by birds makes long distance dispersal very problematic.
The distribution of juniper dwarf mistletoe reflects a history
of migration with its host and of persistence in some populations
and extinction in others.
Management Implications
Juniper forests occur over extensive, regions of northern
Africa, Mediterranean Europe, the Near East, central Asia, the
Indian subcontinent, and western China. In these arid regions
forest growth is slow and regeneration is uncertain. The continued
health and even existence of many of these forests is threatened
by excessive human use, grazing by domestic livestock, insects,
and diseases. One of the major disease agents of Old World junipers
and other Cupressaceae is Arceuthobium oxycedri. This
dwarf mistletoe has the most extensive natural range of any species
in this genus, occurring over a large land area from northern
Africa and Mediterranean Europe to western China. Since its original
description in 1819, national boundaries within its range have
changed significantly, new countries have been established and
others have disappeared. The names of many communities and physiographic
features of the landscape have also changed. Moreover, there
have been significant changes in the nomenclature of some of
the host plants of this important parasite. Consequently, existing
records require updating to reflect today's geo-political boundaries
and taxonomic designations. This will enable research scientists
and applied biologists concerned with pest management in juniper
forests to readily identify locations where this plant is found,
its hosts, where established pest management methods have been
developed, and where the socio-economic impacts for this parasitic
plant have been studied.
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Title: RMRS-RN-11WWW:
Discussion
Electronic Publish Date: September 2001
Last Update: August
20, 2008
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