Welcome
to the WWW site for Astragalus,the largest genus of
vascular plants on Earth (Mabberley, 1993). It was our objective to
provide this website as a resource to those interested in the
biology, evolution, phylogenetics and systematics of this widespread
genus of legumes, as well as some of its close relatives such as
Oxytropis.On this site you will find information derived from
many scientific sources, such as floras, published articles and
monographs by other authors, as well as the results of our own
research (both published and unpublished) on the phylogenetics and
diversification of this genus, its relatives and papilionoid legumes
in general. For more specific information, consult the
List of
Tables provided here. Please
note, this website is under construction; we welcome your comments
and suggestions.
The
flowering plant genus AstragalusL., common names
"milkvetch" or "locoweed", (family Fabaceae or Leguminosae),
containing upwards of 2500, mostly perennial species, is a remarkable
example of adaptive radiation on a global
scale, distributed primarily
around the northern hemisphere and South America. Nested within an
even larger group of predominantly herbaceous legumes, including the
agriculturally important genera Medicago(alfalfa),
Trifolium(clovers), and Vicia(faba bean),
Astragaluscomprises the bulk of a secondary radiation into
cool temperate semi-arid and arid continental regions of the world,
specializing on edaphic conditions and extreme microhabitats
inhospitable to many other angiosperms (Polhill, 1981). Many species
are narrow endemics, often found in marginal habitats or to those
requiring edaphic specializations, while relatively few are
widespread. Astragalusis especially diverse in southwest Asia
(ca. 1000-1,500 spp.), the Sino-Himalayan region (500 spp.), western
North America (ca. 400-450 spp.) and along the Andes in South America
(ca. 100 spp.). Astragalusis also diverse in Mediterranean
climatic regions along the Pacific coasts of North and South America,
and in southern Europe and northern Africa.
The recorded history of Astragalus dates back at least to the 1st century A.D., and the genus was well known to western European botanists of the 17th century. A number of species of Astragalus from southwest and southcentral Asia (e.g., A. gummifer Lab., Iran) are the source of "gum tragacanth" - a substance tapped from roots or stems with hydrophilic and colloidal properties valuable in ice creams, lotions, pharmaceuticals, used since the time of ancient Greece. A few species are edible (A. canadensis L., N. America) or have medicinal uses, and some are used for livestock forage (A. cicer L., USA), but a large number of North American species are poisonous (e.g., A. mollissimus Torr., N. America), especially to livestock and wildlife, a property due to the accumulation of selenium from soils or synthesis of toxic levels of certain nitrotoxins and alkaloids in the foliage - hence the name "locoweed" ("loco" is Spanish for crazy) given to many species.
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