Ponderosa Prowess
Fire adapted species boast inherited traits that have developed through natural selection to help them thrive in their given ecosystems. These traits must have been obtained through differential survival and reproduction to be qualified as adaptations. On the inverse, exaptations are traits that enhance fitness in a given environment, but have not evolved through the action of natural selection. Species that are adapted rather than exapted tend to have a higher survival rate when disturbances occur. Because of their primal location in arid climates prone to forest fires, Ponderosa Pine Tress have developed many such truly adapted traits. For instance, their needles have an incredibly high moisture content that insulate their buds and deter flames. Ultra thick bark accomplishes the same feat for the bole of the tree. Fires both large and small, with low- severity or high-severity have trouble toppling these giants.
Photo by: Susie Kocher
According to Agee fire resistant foliage could be an exaptation instead of an adaptation. What other factors do you think could have contributed to a species evolving these traits which just happen to make them fire resistant?
ReplyDeleteYou stated that exaptations are not derived from natural selection. I thought that the traits did become established through natural selection, however fire isn't the main selective force that caused the trait to thrive?
ReplyDeleteHi Camille,
ReplyDeleteIn addition to the adaptations that you mentioned, Ponderosa also have a very deep root system which protects them from most surface fires. Their branching and crown structure also prevent extreme burning. Lastly, their ability to "self-prune" by shedding their lower branches prevents fires from being able to move up into the canopy.
Source:
USFS. 2005. Fire ecology of ponderosa pine and the rebuilding of fire-resilient ponderosa pine ecosystems. Available from http://www.fs.fed.us/psw/publications/documents/psw_gtr198/psw_gtr198_n.pdf