Qwiz5 Quizbowl Essentials – Speciation

“Speciation” is one of those rare words whose components tell you exactly what it means. Speciation = species + creation; it refers to the process by which a new species is created. While the name is simple enough, the process behind it is anything but. There are four different kinds of speciation: allopatric, peripatric, parapatric, and sympatric. We will learn a little bit about each of these variants, and in the process hopefully create a new species of informed quiz bowler!

By analyzing questions, you can see patterns emerge, patterns that will help you answer questions. Qwiz5 is all about those patterns. In each installment of Qwiz5, we take an answer line and look at its five most common clues. Here we explore five clues that will help you answer a tossup on speciation.

PUNCTUATED EQUILIBRIUM

When Charles Darwin first developed his theory of evolution, he proposed that new species developed slowly and gradually. However, the lack of fossil records demonstrating these slow changes complicated his proposition. In the 1970s, Stephen Jay Gould and Niles Eldredge proposed the model of punctuated equilibrium to explain speciation. Punctuated equilibrium claims that species are relatively stable for long periods of time and then suddenly undergo rapid bursts of change. These rapid bursts of change do not occur across the entire species, but rather at the “edge” of the population: small groups that are isolated from the majority.

ALLOPATRIC SPECIATION

Allopatric speciation is a well-understood form of new species creation. In allopatric speciation, two populations of roughly equal size become separated by a geographic barrier. Unable to breed with each other, each species develops in a different direction. Darwin’s Galápagos finches are the textbook example of allopatric speciation. Allopatric speciation is differentiated from peripatric speciation in that the latter takes place when one of the separated groups is much smaller than the other.

PARAPATRIC SPECIATION

In parapatric speciation a population is not as starkly divided as in allopatric and peripatric speciation. Two diverging populations are only partially separated, ensuring that some level of genetic crossover continues to occur. Eventually, however, the two populations will become unable to interbreed, whether through natural selection or modifications to the environment. The Ensatina salamanders of California’s Central Valley as well as Larus gulls are a prime example of parapatric speciation. These species are referred to as ring species, meaning that their population distribution forms a ring in which adjacent ring members can interbreed, but not the terminal members of the ring. (Yes, we know that calling it a ring and having a terminal are contradictory. Take it up with the biologists.)

SYMPATRIC SPECIATION

Sympatric speciation is the most controversial form of speciation because some scientists doubt its very existence. In sympatric speciation there are no geographic barriers, and members of the same species are close together. A new species appears to spontaneously develop anyway. A common theoretical explanation for sympatric speciation is that some members of a species become dependent on specific features of their environment while others do not. A classic, albeit disgusting, example of sympatric speciation is the development of the North American apple maggot fly.

WALLACE EFFECT

Darwin’s contemporary, Alfred Russell Wallace, was a British naturalist who developed a variety of interesting theories of his own. One such theory is Wallace’s notion of Reinforcement, also known as his namesake Effect. Reinforcement, or the Wallace Effect, proposes that natural selection can encourage speciation. Individuals that were once members of the same species will eventually no longer be able to breed with each other. This reproductive isolation is designed to maintain each developing species’ genetic integrity and decrease the risk of hybrids with low reproductive success.

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Quizbowl is about learning, not rote memorization, so we encourage you to use this as a springboard for further reading rather than as an endpoint. Here are a few things to check out:

• Although his contributions to the theory of evolution are often overshadowed by Darwin’s, Alfred Wallace was a pioneer in the field of naturalism.
  

• What caused the division of the apple maggot fly from the hawthorn fly? There are some theories.
  

• Finches are a little commonplace. Watch this video to learn about some of the more bizarre inhabitants of the Galapagos Islands.

• This video provides a deep dive on the Ensatina salamander, an oft-studied example of a ring species.

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