Common Macrolichens of the PNW Home Species List Identification Key Characteristics Project Page About

Suggested Steps for Interactive Key:

  1. Select about three characteristics that you are fairly sure of.
    Suggestions: (need not follow these, but may be more efficient if you do)
    • Choose only one characteristic from a given group (e.g. growth form)
    • Select "Yes" for characteristics that the specimen DOES have, rather than "No" for characteristics that it DOESN'T have
  2. Click Search button
  3. Choose one of three strategies:
    • If Score for the top choice is twice that of the next best choice AND Fit is larger than 0.7, you probably have the right answer. Check it by clicking on the species name and compare with the photos and description.
    • If Fit is 0 or near 0, your characteristics are contradictory. Go back and revise one or more that are possibly wrong.
    • If somewhere in between, select two more characteristics and click Search (back to step 2). The shortest path to success is to choose characteristics with a red asterisk or two (
  4. If the result list seems too wide, you can compare two or more species by checking them and clicking on 'Compare'. This will show you the most different characteristics between those specific species.
  5. If your results still seem weird, please help us by emailing with feedback. Thank you!

Extra Tips

  1. For best results, use this key with the book "Macrolichens of the Pacific Northwest" (McCune & Gelser).
  2. Chemical tests are described in the above book.

Purpleness Degree of mismatch to likely species.
Greenness Degree match to likely species.
x% In 'Most Likely Species', for boolean characteristics (choice of two options, usually Yes/No), x% means that for that species, x% of the time the species has the selected characteristic value. Example: If you select 'Cilia on Margins' = 'Yes', for Parmotrema perlatum, '90%' means 90% of the time, this species has this characteristic.
Median (± Range) In 'Most Likely Species', for quantitative characteristics (enter number in field), for each species, the median and range are displayed.
Dark Red Non-lichen
Most(**) and more(*) discerning characteristics among likely species.
Score: Relative probability indicator that your specimen matches this species (out of 247 common macrolichens)
Fit: Absolute probability indicator that your selected characteristics matches this species' characteristics
Zero fit or zero score - if all likely species have red bars, time to re-evaluate.