The delineation between adaptation and exaptation
can be difficult to find in some cases. Some species attributes which were once
considered adaptations are now considered more likely exaptation because of
their reason for developing. Serotinous cones are not consistent throughout one
tree or species according to Agee. I would find this to be an adaptive trait
because the high resin content has only one way to release the seeds within the
cone, and that is through fire. Additionally I find this to be adaptive because
the same species or even tree could alternatively produce less serotinous cones
in order to propagate sooner. Serotinous cones can survive numerous types of
fire including low intensity fires up to crown fires.
(Photo from NPS)
Adventitious or latent auxiliary budding after the
crown of a species is scorched by fire is another characteristic which allows
species to survive fires. I find this characteristic hard to qualify definitely
as an adaptation or exaptation. Insect attacks could also cause similar crown
loss in some species as could be seen in some crown fires inducing budding.
Regardless of the origination of this characteristic, it is highly effective
for some species when exposed to high intensity fires.
Reference:
Agee, James K. 1996. Fire Ecology of Pacific
Northwest Forests. Island Press 2nd Edition
j.g. pausas' blog,. (2012). Cork oak resprouting from epicormic buds. Retrieved
from http://jgpausas.blogs.uv.es/2012/07/11/bark-harvesting-and-cork-oak-vulnerability-to-fire/
NPS,. Trees in Greater Yellowstone are adapted to
fire. Retrieved from https://www.nps.gov/yell/learn/nature/fireconsequences.htm
Scott,
ReplyDeleteGreat post! In response to your question regarding whether auxiliary budding is an adaptation or exaptation, I feel that it might depend on the species we are talking about. I'm finding difficulty identifying if certain characteristics are an adaptation or an exaptation without doing research on their ecological history.
Thanks,
Ashley
I find the adaptations of oaks interesting. But maybe, as you note, the resprouting after fire is an exaptation since this trait occurs for other reasons or impacts. The textbook, Fire in California Ecosystems, states that this has likely occurred in response to many other circumstances.
ReplyDeletePrior to fire suppression, the California black oaks was a dominant species in woodlands amongst a scattering of fire resistant sugar and Ponderosa pines. During fire suppression the woodland saw a high increase in less-tolerant of fire conifers like Douglas fir and white fir. This increased density of conifers led to the decrease and mortality of oaks. Without fire the oaks were unable to hold their place in the woodland in contrast to the conifers that weren't controlled with fire and forced to regenerate from seed. Thanks for the post!