28 June 2014 Extremophilia

Part of my attraction to the PolarTrec program is that anything that can survive in polar regions has to be incredibly well adapted to a challenging environment. Plants and animals that can tolerate such extremes could be considered "extremophiles". They thrive or at least survive in the world's most demanding conditions. In the arctic, the challenges include long periods of winter darkness, wind, and temperatures below -40 degrees F. In other climates, the demands may be very different such as heat in the hottest desert, or pressure in the deep seas. Because most animals migrate into the polar regions only for the relatively mild summers, there is little prey available to carnivores. The herbivores, such as musk oxen, must paw through the snow and eat frozen lichens and mosses. Ground squirrels only survive the climate because of their unique ability to hibernate in a very efficient manner, with body temperature depressed to below freezing.

In my recent travel to Hawaii, I found some great examples of what I consider to be extremophiles. Understanding the challenges these organisms face, and the strategies they have evolved to survive gives me great respect for their story. It is always amazing to learn about the strange ways that many plants and animals have adapted to the unique challenges posed by their environment; It also makes for more interesting travel. In Hawaii, we came across a few examples of plants and animals that I definitely consider extremophiles. Consider the volcanic craters of Kilauea volcano and others on the Big Island of Hawaii. This island is the youngest of the Hawaiian Island chain. The volcanos are still active, and the island is still growing. With new ground available, plenty of light, water, and warm temperatures, life struggles to succeed. After a volcanic eruption, the ground here is covered with black lava. It is incredibly sharp, hard, and in the tropical sun, hot. Not the sort of place for any seed to germinate, let alone mature and reproduce. Yet that is exactly what the Ohi'a Lechua tree is able to do. This tree is endemic to Hawaii, meaning it is found no where else on earth. It evolved on these islands, pressured to adapt to the unique demands of pioneering forest growth on freshly cooled lava fields. Known by ecologists as "primary succession," the Ohi'a trees are the first plants to attempt to colonize the lava. In so doing, their roots begin the process of breaking up the solid, bare rock. Cracks in the lava allow other seeds to get a start. The dead leaves and branches provide organic matter to begin the process of building soils needed by other plants. For such a rugged plant, the Ohi'a trees are very beautiful with their bright red flowers.

Another extreme plant we encountered only exists near the summits of the highest volcanos of Maui and Hawaii. It is called the silver sword. Though it looks much like the yuccas and agaves found in the Americas, it is totally unrelated. Close examination reveals a softer leaf, covered with fine hairs. Unfortunately it is favored by the feral goats living on the islands, causing the plant to be nearly extinct. Like the Ohi'a and many other plants and animals of Hawaii, it is endemic, occurring nowhere else in the world. The silver sword is an example of convergent evolution where the environmental conditions demand the most efficient leaf and plant design for survival. The dry, cinder covered, high altitude slopes have only permitted this one arrangement to survive. It is convergent (two things come together) in that it looks much like the leaves of an agave, though genetically there is no relation. This is much like the wings of a bird and the wings of a flying fish (fins) or a bat (hands), they all work for flying, but have very different origins. You could say that form follows function.

On the tops of these volcanos there is also a species of insect that has evolved to survive these extreme conditions and occurs nowhere else on Earth. The Wekiu apparently eats other insects that are blown to the summit or make their way to the tops of the high volcanos. On our visit, we noticed lots of lady bugs crawling in the lava, with seemingly nothing to eat in sight. Plenty of fodder for the Weiku bugs! These highly specialized bugs are able to tolerate daily fluctuations in temperature from 115 F to 25 F, and survive freezing temps and snow in winter with the help of anti-freeze glycoprotein compounds in their body fluids. They are found only on the cinder cones of Mauna Kea (Mauna Kea visitor center information, 2014)

Along with all the unique endemic species in Hawaii, there are also numerous non-native, invasive species that are often out-competing the natives or destroying habitat. This story is repeated over and over again on islands with lots of endemic species. Some of the problems, especially for native birds in Hawaii, come feral goats and cats, rats, and mongoose. There are also numerous plants from other places that drive out the unique Hawaiian flora.