Wednesday, April 4, 2012

Origins: Prickly and Bitter

I guess the first thing that I should do before jumping right into the blog is explain where the name came from for my blog.

"Prickly and bitter" is one of the hypotheses explaining why there are fewer herbivores than plant species. In theory, if everything in the world evolved to fit a niche and no two species competed for one niche (since competition, by default, is not productive to the evolution of any single species) you should have one herbivore (insect or other animal) for every one species of plant. But this is, in fact, not the case. We have many more plant species than plant "predators", and there are well-documented cases of insects competing with each other for plant resources. There are other cases of generalist insects like aphids that will feed on a wide range of plants. So what's the deal? Even if you account for the extinction of plants and "host shifting" of insects from one extinct (or critically endangered) species onto a much more common one, it still can't account for this dichotomy between the abundance of plants vs. their herbivores.

The prickly and bitter hypothesis accounts for this discrepancy by pointing out that many plant species are not hospitable to being consumed by herbivores. Many cacti, for example, have a fine coating of razor-like hairs that would make consumption of them incredibly difficult. Other plants, like the deadly nightshade, have such potent alkaloid chemicals in their leaves, stems and fruit that most animal species steer clear of.

Is this hypothesis true? Well, it's a hypothesis for a reason. It helps account for the discrepancy, but it's not without its own faults. But since it has a catchy name, I like it.

So there you have it. Prickly and Bitter.