Florida lizards evolve rapidly, within 15 years and 20 generations

Rebecca Morse
Author: -
Published: October 23rd, 2014
Link: http://www.sciencedaily.com/releases/2014/10/141023142306.htm

Summary: This article describes how a native species of lizards living in Florida, named Carolina anoles (or green anoles), has evolved quickly due to the introduction of an invasive species of lizards from Cuba. This invasive species, called Cuban anoles (or brown anoles), began to compete with the green anoles for the same food and space. Within a few months, the green anoles had begun to move to higher perches in trees as brown anoles competed for the lower branches. Because the higher branches were smoother and not as thick as the ones they previously occupied, the Carolina anoles' feet started evolving. Over a period of fifteen years and throughout twenty generations, these lizards' toe pads became larger, and they gained more sticky scales on their feet to help them grip the branches. Yoel Stuart, the lead author of this study, also observed that adults of each species have been known to eat the young of the other species, which could lead hatchlings to need to move into the trees hastily to avoid being eaten. This could be another reason as to why the toe pads of the green anoles evolved to be larger after brown anoles began to compete with them. This change occurred quite rapidly; to fully comprehend this example of evolution, the article states that if human height were evolving at the same rate these lizards' feet were, the average American male height would jump from 5 foot 9 inches to 6 foot 4 inches over the course of twenty generations. The article then goes on to detail how this study is one of only a few studies that documents "character displacement" well. Character displacement is what biologists define as similar species competing and, as a result, evolving differences which then allow them to occupy separate niches.

Connection: This particular article relates to the topics we have studied so far in many ways. In our first unit this year, we learned about ecology, which includes the subjects of invasive species, competition, and niches found in chapter 35. In that chapter, we learned about how invasive species are organisms that humans have moved from their original location to a new geographic place. Many times, these non-native species have outcompeted or preyed on native ones, pushing them out and taking over. This relates to the Cuban anoles competing with the Carolina anoles for food and space, which are part of the Carolina anole's niche. A niche is defined as a living arrangement that includes an organism's food sources, habitat, when it is active, and other factors that constitute its job. What was different about these two species was that their case did not fit with the Competitive Exclusion Principle we learned about, which states that two different species cannot live in the same niche and habitat at the same time. Instead, this study showed character displacement. Recently, we read an article titled "But How Could A Cell Evolve?" by Michael J. Behe, which questioned Darwin's Theory of Evolution. We have not learned a lot about Darwin in our studies so far this year, but this article about cells did give an example of evolution that relates to the lizards, which was also the same example detailed in the article about Florida lizards. Darwin observed that the beaks of two species of finches in the Galapagos Islands evolved and changed their shape. This resulted in the finches adapting to separate food sources, so that although they had originally occupied the same niche, they evolved to be able to coexist, just like green anoles have evolved to be capable of coexisting with the green anoles.