Summary Of My Island Life By Luke Harmon

In his essay, “My Island Life,” Luke Harmon discusses the importance of islands and how they have been used by evolutionary biologists to study evolution and diversification on Earth. Harmon focuses on biogeography and on how different species are distributed across the Earth. Harmon also makes a point to mention how human introduction of invasive species is rapidly causing islands around the Earth to become uniform and less diversified. Harmon’s research on the evolutionary history of lizards found on two separate regions of Islands begins with the influence of Wallace’s line, discovered by Alfred Russel Wallace. This line is described as invisible boundaries that separate Earth into provinces, and these provinces contain distinct species. Wallace noticed that the physical influences and conditions did not change across the line, but the species inhabiting it did. With Wallace’s discoveries in mind, Harmon hypothesizes that by studying the diversification and evolutionary history of two different lizard species, anoles and day geckos, will show how evolution can be predictable.

Abundant in the four largest islands of the Caribbean, different species of anoles have unique body shapes and perches depending on their habitat, which categorizes these anoles as ecomorphs.

Although the four anole ecomorphs are almost identical in appearance and inhabit the four islands, they are not closely related. The lizards on each island descended all from a few original species that later evolved and differentiated into a large number of descendants. It can be observed that in all four species, their ancestral lineages have evolved independently but evolving the same traits for the habitat they were in. Harmon explains how this can show the predictability of evolution on a longer time

scale.
To further study how evolution can be predicted, Harmon explains, is to repeat the experiment using a different species of lizards. The lizard used were day geckos and their species diversification can be seen throughout the islands of the Indian Ocean. Harmon explains how comparing the two ways the species have diversified and observing to see if they are similar, will help support the idea that evolution can be predicted and repeated. When studying anoles, it is possible to predict that lizards existing in the same area will have different features to their perches, such as height and diameter. Also, the body types of the lizards can reveal the type of environment they live in. These predictions held true for day geckos as well. However, the ecomorphs that the anoles live in are not present in the day geckos. Their ecomorph is different, they simply partition the habitat among the different species so that one species live exclusively on a certain area.
With these experiments, Harmon’s concludes that evolution is predictable. Yet, there are factors that limit the predictability. Harmon states that the evolution is only predictable over a certain amount of time and if that the original conditions are affected too much, the outcome cannot be predicted. The study of islands has given much insight to the evolutionary history of Earth and the various species that live here. Harmon emphasizes the destruction humans have caused on the diversity of these islands and urges a change. Preservation of these magnificent places is not only crucial for science, but to the natural structure and mechanisms of Earth.