Francisco, Wirt, and other honorable members of the forum:
I wonder how much water the ESTIMATED age of Larrea* holds when compared to
less guessful methods such as tree rings. It seems to me that, while it may
be believable that a clone might "last" (same genes) for 11,000 years or so,
it is doubtful that any of the original tissue has lasted that long in any
form. It would seem relevant to Francisco's question to look at age/size
ratios in organisms that, for example, do not reproduce asexually. Some oak
or aspen clones might be "old" too . . . and then there're fungi reported as
being the largest organisms . . .
When it comes to relevance to the question, I share Francisco's curiosity,
and am not quite ready to discard the correlation simply because, if you
will excuse the inference, of its age.
I have often wondered about "bunch" grasses that also form rings, apparently
when the "original" plant, presumably once located somewhere near the center
of the ring, dies, with such death occurring at the inner edges of the ring.
This phenomenon would seem to be a manageable subject of study. I memory
serves me correctly, Nasella (Stipa) pulchra is one such species I have
seen, and mortality does not seem to be related to herbivory. However, it
would be interesting to know what IS related to mortality and longevity
(and, by the way, how much the phenomenon might be related to habitat
conditions). While the Nasella examples seem to be resistant to fire as well
as animal herbivory, this is not to say that pathogens might not be involved
as well as "age." I have noted large isolated (protected from grazing?)
colonies of Nasella (lepida?) that, judging from the diversity of associated
indigenous species(e.g., Dichondra occidentalis, perennial geophytes)
generally absent from such colonies in more exposed locations (associated
species including alien populations). Studies of such populations, if they
still can be found, might be interesting, especially with regard to genetic
uniformity and diversity (I have entertained the idea, for example, that
such isolated stands just might be clonal remnants of great (who knows HOW
great?) age. What about giant squids? Tortoises? Parrots? What about those
and other leaks?
After all, there was no death until sex reared its ugly head, eh? So,
relatively speaking, what selects for so long a life and for "early" death?
What about survivorship curves and ratios and dispersal mechanisms and "the
thousand natural shocks that flesh is heir to?"
I know not what others may say, but as for me, I'm still curious about this
age:size ratio thing.
WT
*I confess to not having read the paper.
----- Original Message -----
From: "Wirt Atmar" <[EMAIL PROTECTED]>
To: <ECOLOG-L@LISTSERV.UMD.EDU>
Sent: Wednesday, November 19, 2008 8:11 AM
Subject: Re: [ECOLOG-L] Data on lifespan vs. body size for plants?
Francisco de Castro asks:
I wonder if someone could direct me to studies/webs/data on lifespan of
plants, or rates of natural mortality (meaning excluding herbivory) as
related to individual mass/size. More specifically: how long a plant
will live (if is not eaten by an herbivore) given its size. I have
searched the ISIWoK extensively and found some papers for trees
(specially large trees) relating longevity to size at time of death, but
nothing for small plants. I already have Marbá et al. 2007, PNAS
104(40), but in their estimates of lifespan, herbivory is included in
mortality rates.
The correlation between size and longevity that was often talked about does
not seem to hold as much water as it used to. The now-believed-to-be oldest
plant in the world is only a bush, a vegetative creosote ring in the Mojave
Desert, California:
http://www.ourwindowonnature.com/2007/05/06/the-oldest-living-tree-is-a-bush/
The plant is estimated to be 11,700 years old, twice the age of its nearest
competitor, a bristlecone pine, which is also a small tree.
Vasek FC. 1980 Creosote Bush: long+lived clones in the Mojave desert. Amer.
J. Bot. 67. 246-55. Larrea tridentata. Growth rates. Oldest clones may be c.
11,700 years. Growth, Zygophyllaceae
Wirt Atmar
--------------------------------------------------------------------------------
No virus found in this incoming message.
Checked by AVG - http://www.avg.com
Version: 8.0.175 / Virus Database: 270.9.10/1810 - Release Date: 11/24/2008
2:36 PM
