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Usnea Growth Rates (I am brand new to lichenology)

  • 07 Mar 2017 9:46 AM
    Message # 4653104
    Deleted user

    Hello all! 
    My name is Chris Bivins, I'm a botany student at San Francisco State University, and I am just now starting to delve into the strange, complicated but beautiful world of lichens. I was hoping someone on here might be able to help me out with growth rates of fruticose lichens. Does anyone know the average growth rate of a typical Usnea lichen species? Is there a wide degree of variation between growth rates within species in a single genus? What about between genera? Does anyone know about the average growth rates of the three major growth forms of lichen? I've done a bit of digging in the literature, but so far what I have found is that there seems to be more work done on growth rates of crustose lichens by geologists than other growth forms. I found some research on the rate of usnic acid production, however, I have not been able to find anything on the rate of increase in size of Usnea lichens. My end goal in seeking this information is to determine the age of some Usnea lichen I have found. When unfolded and spread out on a two-dimensional surface, some of them are quite large, in the range of about a meter wide. If they grow as slowly as I think they do, then they must be pretty old. 


    Anyways, if there is anyone who is knowledgeable about the methods of determining the age of Usnea lichens (and lichens in general), and you would like to share with me what you know, I would really appreciate it. Thanks! 

  • 07 Mar 2017 11:49 AM
    Reply # 4653404 on 4653104

    If you can, post a picture of the lichen you are asking about.

  • 07 Mar 2017 12:11 PM
    Reply # 4653446 on 4653104
    Deleted user

    In Macrolichens of PNW, Bruce & Linda say Evernia prunastri branches once a year in PNW, so age can be determined by counting branch points. 

  • 08 Mar 2017 12:19 PM
    Reply # 4655449 on 4653104

    First, the easy answers - each species has a different growth rate, so even within one genus the rate differs. For the Evernia forking, see Bryologist 93(1): 32-36.

    Another paper that touches on growth rate but is mostly biomass not length is Boucher and Stone, Ch. 29 in The Fungal Community eds. G Carroll and D Wicklow, Marcel Dekker NY. I also researched growth rates for my thesis, some of that is in Bryologist 92(1):81-94. But the actual length is not in that paper. But if you read that paper, you will see that you could go out and look at a branch, and look at the length of a species on the section of growth for each year, to get a very rough estimate. Unfortunately, telling Usnea spp apart is no easy task, and it would be tough to decide which tufted thalli will be come the long ones you are describing.  Perhaps this is a project you should take on!!


    I think if i were you I'd work on learning to tell the spp apart first... and that is tough. I am very slowly working on a little book that will help but that is not available yet. A similar book for Britain, is available from the British Lichen Society for a very small amount, called Aide Memoir for Usnea - just nice little sketches of the spp showing relevant characters. However, the spp that we have are not all here. Also, McCune & Geiser Macrolichens of the PNW is a super book anad will get you a long way into understanding Usnea.


    And a cautionary note - don't expect to be able to ID Usnea by looking a photos on line - as you can read in the Forum, photos are great but don't always show the characters you need.


    best, Daphne

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