Spanish Moss

While in Florida, I couldn't help but notice the Spanish Moss (tillandsia usneoides) that hung from every tree. I wondered why it was there and what, if any, benefit it provided for the host tree on which it hung.

Spanish Moss

It turns out the moss is not beneficial for its host.  While it doesn't kill the tree, it lowers its growth rate by blocking light and increases wind resistance, which can be fatal in a hurricane.  It does, however, provide shelter for creatures such as rat snakes, bats, and jumping spiders (which are only found on Spanish moss).  It has uses for humans as well, such as building insulation, mulch, packing material, and mattress bedding.  

While we like to emphasize Nature's ability to create cooperative, mutualistic relationships, sometimes in the process of niche differentiation, resources are available and mutations present to create parasitic relationships  such as this one.  But it is interesting to note that while it is a parasitic relationship, it is not usually fatal to the host and creates benefits for the ecosystem as a whole.