CPC Plant Profile: Wayside Aster
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Plant Profile

Wayside Aster (Eucephalus vialis)

Not your typical showy aster: Aster vialis in bloom showing its rayless inflorescences. Photo Credit: Ed Alverson
  • Global Rank: G3 - Vulnerable
  • Legal Status: N/A
  • Family: Asteraceae
  • State: CA, OR

Like so many other species, wayside aster is fighting an uphill battle to survive. To add insult to injury, it is not even a very attractive plant. Wayside aster lacks the showy, petal-like "ray flowers" that help many recognize other asters. This understated flower is threatened by habitat changes within its limited range in and around Oregon's Willamette Valley, and is in danger of quietly disappearing. Seedling recruitment appears nonexistent in some populations, a grave sign of its uncertain future. Wayside aster's reproductive biology and habitat requirements make it especially vulnerable in human altered ecosystems. While many plant species self-pollinate, Aster vialis require pollen from other individuals in order to produce seeds. Increasing forest fragmentation makes obtaining pollen more difficult as great distances often separate plants. Even after this distance barrier is overcome, seed set is low. Experimental hand pollinations in the greenhouse typically produce few seeds. Additionally, germination rates are often extremely low in laboratory conditions. These low germination rates likely reflect that specific conditions, such as light and an absence of leaf litter, are necessary in order to break dormancy. Vigorous and reproductive Aster vialis plants are found in habitats that receive abundant light. Fire historically played a large role in maintaining open understory habitats in and around the Willamette Valley. As opposed to the clear-cut or regeneration forest harvest methods used today, fire historically did not result in the death of all the trees in the stand. Larger fire tolerant trees such as Douglas fir and ponderosa pine often survived and provided some shade. Natural regeneration after a fire is patchy, resulting in forest gaps that provided habitat with high light levels suitable for wayside aster. Fire also burns away leaf litter, creating conditions thought necessary for germination by exposing the ground to sunlight and returning nutrients to the soil. In pre-settlement Oregon, wayside aster most likely did not persist in specific locations over long periods of time, but new populations were continually established as new habitats were created by natural disturbances. Under land-use practices today, this regeneration cycle is made more difficult due to a lack of available habitat.

Conservation Actions:
Participating Institutions
Taxon Eucephalus vialis
Authority Bradshaw
Family Asteraceae
CPC Number 356
ITIS 508094
Common Names way-side aster | wayside aster
Associated Scientific Names Aster vialis | Eucephalus vialis
Distribution OR: Willamette Valley, Klamath Mountains, Western Cascades, Coast Range (Lane and Douglas Counties)
State Rank
State State Rank
California S1
Oregon S3

Found in woodlands on mineral soil with little leaf litter, between 500-1500 ft (150-460 m) elevation (Meinke 1982) Associated species include Pseudotsuga menziesii, Castanopsis chrysophylla, and Arbutus menziesii (Meinke 1982)

Ecological Relationships

Aster vialis is found in different stages of forest succession from recent clear-cuts to mature forests. This species does, however, demonstrate a preference for moderate light levels. It does not grow well where completely shaded or where clear-cutting has occurred. Aster vialis growth and seed production appear to decline as succession proceeds, most likely due to increased competition for resources, especially light. In sites with a closed canopy, Aster vialis plants do not produce flowers (Kaye et al. 1991). Under natural fire regimes, the canopy was opened, but some trees remained creating patchy shade and adequate habitat for Aster vialis (Kaye e al.. 1991). Seedling recruitment has been noted where mineral soil has been exposed through removal of the litter layer (Wogen 1998), providing evidence that fire disturbance is necessary to maintain Aster vialis habitat. It is not known whether seedlings that emerge after fire come from seeds brought in from nearby areas or whether they come from an existing soil seed bank (Kaye et al. 1991)Aster vialis is completely self-sterile and has extremely low viable seed set even when outcrossed (Kaye et al. 1991). Seed set under experimental out-crossed conditions was 21% (crossed within population) and 29% (crossed between populations) (Kaye 1991). Pollination is facilitated by Bombus vosnesnski (a bumblebee), Lasioglossum spp. (smaller bees), Epicanta puncticollis (blister beetle), and Ochlodes (skipper) (Alverson and Kuykendall 1989 in Wogen 1998). The low viable seed set may result from inbreeding depression. Genetic analysis revealed low mean genetic variation within populations and intermediate genetic variation between populations. A lack of correspondence between genetic differentiation and the geographic locations of among Aster vialis could be due to fragmentation, restricted gene flow between distinct populations, genetic bottlenecks and fixation within small populations, and error in sampling plants and genetic loci. There was no evidence of genetic distinctness of southern populations, but the recently identified populations in the Siskiyou Range may be more distinct. This discovery extends the geographic range of the taxon and suggests that cryptic populations may exist throughout its range.


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Common Name Name in Text Association Type Source
Bumble bees Bombus vosnesenskii Confirmed Pollinator Link
Sweat bees Lasioglossum Confirmed Pollinator Link
Butterflies & Moths
Skippers Ochlodes sylvanoides Confirmed Pollinator Link
Blister beetles Epicanta puncticollis Confirmed Pollinator Link

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