Short-rayed alkali aster (Symphyotrichum frondosum) COSEWIC assessment and status report: chapter 6
Biology
Symphyotrichum frondosumis an annual species in the Asteraceae that is primarily found in the draw-down margins (Douglas et al. 1998) of alkali lakes (Munz and Keck 1970) in the bunchgrass zone (Douglas et al. 1998). Its ecology is tied to fluctuating lake levels. One Canadian (sub) population was found in a drier beach site proximal to the drawdown zone. Wiggins (1980) also reports that it can occur in drier sites.
No published accounts of flowering times could be found. However, based on site visits by the authors, and specimens examined at the UBC herbarium, the flowering time in British Columbia is from late July (Eastham collection # s.n, UBC) to early October (Lomer 93-181). Baumbrough (pers. com. 2003) indicates that plants sometimes appear earlier in drier years. He has seen plants as early as mid-July, and flowering plants as early as mid-August through to mid-September. Brouillet (2005) indicates that the species is autogamous, in part, with little genetic exchange among distant populations. This species can withstand high pH and high salinity, but prefers moist habitats (Munz and Keck 1970).
No specific literature was found on the dispersal mechanisms or strategies of S. frondosum; however, wind dispersal is common in aster species (Anderson 1992, Brouillet pers. comm. 2005). It is likely that seeds are dispersed by several additional means, including, under natural conditions, dispersal by wave action, lake currents and by waterfowl.
The occurrence of the ephemeral population in Surrey British Columbia suggests that long distance dispersal of S. frondosum occurs. Whether it came to this site by wind, waterfowl or water is not known, but all three are possible. The latter possibility would suggest that a population exists upstream, east of the Coast Mountains, as is speculated by Lomer (1996).
The adaptability of S. frondosum is unknown. However, three populations occur on heavily used and managed beaches and, while more abundant in less trampled areas, it clearly can persist even with some trampling.
Meta-population dynamics may play a role in this species biology, but this requires investigation.
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