honeycreeper birds, fruit flies, and silversword plants). There are many examples of adaptive radiation and endemism in island chains such as Galápagos (e.g., finches, mockingbirds, lava lizards, and Opuntia cactus) and Hawaii (e.g. All of these lizards are endemic to the archipelago-that is, they are found nowhere else in the world (Figure 2.15).Īdaptive radiation occurs when one ancestral species leads to several descendent species as new habitats are colonized.
Thus, from one colonizing species, the archipelago now has several different species of what we call lava lizards. Punctuated equilibrium Adaptive radiation Convergent evolution Gradualism. This pattern was then repeated throughout the islands, with migration, drift, mutation, and selection all acting differently on different island populations. Scientists studying an island chain discover several species of birds that are. Organisms of one species can arrive to an island together and then disperse throughout the chain, each settling into different niches and exploiting. After many generations of mutation, drift, and selection, the colonizing population was sufficiently different from the parent population to warrant classification as a different species. For example, an ancestral population of lizards, possibly from mainland South America, colonized the Galápagos islands (in the equatorial Pacific Ocean) millions of years ago. So much that they are considered separate species. Over time, isolated populations of the same species can diverge Figure 2.16 An endemic lava lizard on one of the Galápagos Islands Mutation and migration all play a role in generating diversity, and selection and drift eliminate some of this diversity. 2.15 Biodiversity & Adaptive Radiation Biodiversity is a product of evolutionary processes
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