Coast Microseris (Microseris bigelovii) COSEWIC assessment and status report: chapter 6
Biology
There is very little published information relevant to reproduction and dispersal, germination, seedling ecology, survivorship, herbivory or physiology of Microseris bigelovii in Canada. The following notes are based primarily on observations and experiments conducted by the first author of this status report.
General
Microseris bigelovii may be an annual or a winter annual, apparently depending on whether the soil becomes suitably moist before the onset of cool winter weather. It has a generation time (germination to death) of 8-10 months.
Reproduction and dispersal
Microseris bigelovii shows a high degree of self-pollination, with occasional low-level outcrossing (K. Chambers, pers. comm. 2003). It blooms in May or June and produces seed in June. Many populations in the United States occur on or near bird nesting colonies. The bristle-tipped pappus scales may tend to catch on bird feathers. The highly disjunct distribution of the plant throughout the west coast of North America may be attributable to bird dispersal. Most seeds, however, are likely dispersed over short distances by wind and gravity. The pappus scales diverge from the crown of the achene in an open fashion that likely allows wind to puff and tumble the light achenes over short to moderate distances.
Germination
Seeds germinate readily when watered, and do not appear to have any dormancy mechanism. Over 90% of seeds collected from Church Point in 2002 germinated within 2 weeks of being planted.
Seedling ecology
Where Microseris bigelovii grows amongst clumps of Cladina portentosa, its seeds tend to germinate in the autumn. This fall germination may be due to the lichen absorbing moisture from nocturnal fog and retaining this moisture throughout the day. This additional moisture is then available for germination. The seedlings may grow quickly before the onset of cooler winter weather, and then persist until warmer temperatures return in the spring. Plants that do not grow in Cladina appear to defer germination until late winter or spring.
Survival
Survivorship curves have not been developed for Microseris bigelovii, nor has anything been reported that would assist in determining recruitment or conservation concerns.
Herbivory
No herbivory was observed in any of the populations, even though several occurred in areas with evidence of moderate grazing by black-tailed deer and rabbits.
Physiology
Microseris bigelovii appears to tolerate dry sandy soils and may require frequent coastal fogs to protect it from desiccation. It also tolerates high nitrogen/fertility levels that occur where it grows amid guano. The species may be outcompeted on less adverse sites.
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