Natural Selection by Predation

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Learning objectives:

$1.$ Apply a correct understanding of the process of natural selection to interpret experimental data.

$2.$ Develop a hypothesis given a theoretical framework and set of observations, and articulate a prediction based upon observed relationships between variables in a natural system.

$3.$ Collect data and make basic calculations to develop summaries for an experimental group and a control group.

$4.$ Gain familiarity with approaches for studying evolution.

$5.$ Understand the short timescales over which evolution by natural selection can occur.

Introduction

For well over $20$ years, scientists have studied the diversity of the anole lizards of the Caribbean to learn about the processes shaping the evolution of populations and species. Anole lizards are found in the southern United States and throughout the islands of the Caribbean. All anole species feed on similar food items $-$mostly small prey like insects and crickets. Despite overlap in food requirements, the Caribbean islands are home to a great variety of anole species. These species differ in the habitats in which they live and feed, minimizing competition for resources among species and supporting diversity. Some anole lizards live on the ground, while others live high in the forest canopy. Still others are found almost entirely on small twigs, and others live in grasses. While closely related, the lizard species found in these different habitats can look quite different from one another.

Their starkest morphological difference is in the length of their legs and the size of their toe pads. Ground lizards, for example, have long legs that enable them to sprint across broad surfaces like tree trunks and the ground to catch prey, while twig lizards have very short legs that help them to grasp and balance on narrow surfaces.Canopylizardshaveexceptionallylargetoepadsthatenablethemtoclingtoslickleafsurfaces,while ground lizards with small toe pads are unable to climb leaves. The association between these traits and the habitats that the lizards occupy suggests that these traits are adaptations. In this activity, you will examine the results from an experiment designed to learn about how different traits in anole lizards evolved.