Stick Insects are Scentimental About Their Mates

Something that we are recently covering in our AP Biology class is the topic of evolution, and we are learning about the many different species and organisms that are now existent in our world. These species have developed through many different mechanisms, one of them specifically being speciation due to reproductive isolation- the existence of biological factors (barriers) that impede members of two species from producing viable, fertile offspring. A combination of several barriers can isolate a species’ gene pool. A specific pre-zygotic barrier that impedes mating is behavioral isolation- an isolating mechanism in which two allopatric species do not mate because of differences in courtship behavior.

According to a new study, fragrance, or scent, is an important factor in stick insects’ choice of mate. It could explain why insects are still able to show a preference for mates from the same species — a key to evolutionary success. In evolutionary terms, the ability to avoid mixing genes with other species is important to preserve differences between species and evolve characteristics that are advantageous to survival- natural selection plays a large part in this. Scientists now believe that insects’ natural perfume plays a huge role in providing preference within a species.

For the experiment, the scientists coated each stick insect with particular chemical scents, and let them free. The insects with similar scents were in the same population, and when introduced to new populations of stick insects, they were unwilling to mate with each other. The scientists discovered that mate choice appeared to be based on the mixture of specific chemical compounds on their skin that made them more or less attractive to each other. Stick insects with similar scents tended to mate with each other and separated off into their own population. The team also studied what happened when female stick insects were ‘perfumed’ artificially, with chemicals, either from their own, or from a different species. They found this directly affected how attractive they were to males. Dr. Riesch states that, “It takes a very long time to produce a new and entirely distinctive species. We think that natural selection and mate choice can cause substantial progress towards the formation of new species, but we still do not know what other factors help complete this process by preventing the insects from mixing their genes at all.”

My reaction to this article was surprise due to the fact that I never knew that scent could possibly cause speciation between species. It was interesting for me to understand that some small preference for the insects could lead to a whole new species. Also, I finally understood that behavioral isolation does not just pertain to courting rituals, but also is about personal preferences for each insect. To realize that small preferences like scent can cause a whole new species to come into existence proves how evolution occurred, and how factor such as natural selection, genetic drift, and other events and mechanisms all work together to create new and specific populations of organisms.

About Mr. Mohn

Biology Teacher

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