Astragalus australis var. olympicus may represent a relictual population of A. australis that existed in the Olympic Mountains during the Pleistocene. It remained during glacial advances, and was stranded in suitable habitats as the climate changed and adjoining populations receded (Kaye 1989). This species is set apart from other Astragalus species by distinctive inflated pods, which may be an important dispersal adaptation. In addition to the explosive expulsion, consumption or simply dispersal by gravity common to flat pods, inflated pods can also be dispersed by wind (Ridley 1930 in Schreiner 1994). The inflated pods may also act as """"mini greenhouses,"""" raising the temperature around the developing seeds.It appears that soil chemistry determines the broad-scale distribution of Astragalus australis var. olympicus, while competition and other environmental factors determine it local distribution (Kaye 1989). An association with VAM mycorrhizae (O'Dell in Kaye 1989) may help it survive in high pH and calcium soils, which are functionally deficient in phosphorous (Lesica and Antibus 1985 in Kaye 1989).The structure of Astragalus australis var. olympicus plants suit them to areas of poorly developed, unstable soils. The tap root branches to form spreading lateral roots. This species may be subjected to a fair amount of sliding and downhill creep. There is probably considerable frost heaving of soils in late winter and early spring due to the sparseness of vegetation. This may keep other species from becoming established and competing (WNHP 1999).Astragalus australis var. olympicus is an herbaceous perennial that holds over-wintering buds just below the soil surface. The species does not appear to reproduce vegetatively. Plants usually begin to bloom in early June and peak in late June. A few fruits dehisce (break open) in late July while still on the plant, but most seeds are dispersed in September after fruits have fallen (Sheehan and Kaye 1986 in Kaye 1989).Experimental insect exclusion reduced overall fruit set but not the number of seeds per fruit. This indicates that Astragalus. australis var. olympicus is typically out-crossed but genetically self-compatible. A mechanical barrier, not a genetic one, may interfere with self-pollination. Inbreeding depression from selfed seeds was not tested, but selfed seeds from other rare Astragalus species do display decreased fitness. Self-compatibility in A. australis var. olympicus is consistent with the view that small populations survived in the glacial refuges during the Pleistocene, and suggests that it may be able to survive future bottlenecks (Kaye 1989).Bumblebees (Bombus appositus, B. birafius nearcticus, and B. occidentalis occidentalis) and a solitary bee (Osmia spp.) are the primary visitors to Astragalus australis var. olympicus flowers. These bees are capable of tripping the pollination mechanism, and are observed to be relatively faithful to A. australis var. olympicus (Kaye 1989). Despite abundant flower production, seed set was observed to be low in monitored plants. Low seed set was primarily due to predation, seed abortion, and lack of fertilization. At the sites where weevils were present, predation accounts for the greatest loss of ovules within fruits. Fertilization (or lack of) is not usually a limiting factor (Kaye 1989). Seeds do not possess highly specific germination requirements. They germinate equally as well in light and darkness. Rates of germination tend to decrease with decreasing temperature and moisture availability, but some seeds are able to germinate near environmental extremes. Most seeds require seed coat scarification to break dormancy. Frost heaving; soil slumping; wind; gnawing by insects, ingestion by rodents and birds; and fungal hyphae may cause scarification in nature. A weevil, (Tychius spp) was the only adult insect observed to be common on buds, flowers and immature fruits. Larvae reared from fruits produced only Typhius weevils (Kaye 1989). A patchy but locally abundant distribution may make A. australis var olympicus more susceptible to predation than one with a sparse distribution. A. australis var olympicus seems to have few defenses against the Tychius weevil (Kaye 1989). Seed predation appears to have a negative effect on population growth, but is not responsible for the rarity of the taxon. Some populations occupy habitats prone to rock slides and surface disturbances by introduced mountain goats. Therefore, seed production is crucial for replacement of individuals within populations and for dispersal to new sites (Kaye 1989). Kaye (1989) suspects that plants do not reach reproductive age until they are five to fifteen years old. Low observed rates of seedling establishment and dominance of large reproductive individuals indicate that recruitment is low. Low seedling establishment is typical of plants at high elevation (Bliss 1971 in Kaye 1989). Both summer drought and winter freezing disturbances probably restrict survival of A. australis var. olympicus to specific microsites (e.g.: rock margins) where drought and freezing disturbance is reduced (Kaye 1989). While growth rates are most sensitive to the number of reproductive individuals, population viability relies on seedling recruitment. In order for projected declines to be reversed, increases in seedling recruitment must be sustained (Kaye 1989). Monitoring of grazing impact revealed that A. australis var. olympicus was grazed in more than half of the subpopulations surveyed, and that injuring was sporadic but sometimes intense. While it is not expected that mountain goats consume or trample the last of the individuals, they may increase risk of extinction by fragmenting populations or habitats (Screiner et al. 1994).