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Thamnolia Distribution in the Cascades

  • 11 Oct 2016 8:32 PM
    Message # 4301477
    Deleted user

    Some years ago, I found a cluster of Thamnolia sp. on Silver Peak on the south side of Snoqualmie Pass. After not finding that species elsewhere in the central Cascades, I returned to Silver Peak this year to make sure I wasn't crazy. In fact, there is a colony of Thamnolia sp. limited to the immediate summit-area of Silver Peak. The lichens occur only on west-facing Ohanapecosh formation rocks. A subsequent day-long search on nearby Granite Peak, just north of Silver Peak revealed no Thamnolia. Does anyone have any knowledge of what conditions are needed for Thamnolia and why colonies in the central Cascades might be hard to find? I see that the UW Herbarium has a sample from Rosevelt Peak (WTU-L-021878) although it's latitude-longitude is incorrect either on the specimen card or on lichenportal.org. I haven't hiked up to Rosevelt to look, but most of the rock up there is granite/quartz monzonite, with small outcrops of Tertiary volcanics. Other locations on lichenportal.org suggest volcanic rocks might be key. Any ideas?

  • 12 Oct 2016 7:21 AM
    Reply # 4302165 on 4301477
    Bruce McCune (Administrator)

    I don't have much experience with the Washington Cascades, but in Oregon the distribution of Thamnolia is very spotty. Even in what seems like ideal habitat it might not be present. Conversely it occurs in some surprising low-elevation spots, always big rock outcrop areas. I do know that it can thrive on soil developed on granitic rock, as well as basalt.

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