Red Deer River Naturalists

The Red Deer river Naturalists are a group dedicated to learning about and preserving natural history. They have regular programs with speakers and many field trips.

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Monday, November 2, 2009

Island School of Evolution

This is my first offering for Natural Wise and I should warn you that it isn't going to be the normal Central Alberta nature story. Keith suggested an article about nature's response to the end of summer, but unfortunately I'm not the sort of person who looks forward to the coming cold. My natural response to the end of summer was to jump on a plane for Maui. One would think that a tropical island in the middle of the Pacific Ocean is totally different from Alberta, but the laws and patterns of nature still apply despite the obvious differences in geography.


Another alien species observed on a Maui lava flow

There are some useful things that an island like Maui can teach an Albertan. Europeans arrived in Hawaii and western Canada about the same time and from a naturalist's point of view, the results have been strikingly similar so far. The climate on Maui is surprisingly diverse, ranging from very wet on the windward north-eastern shores to near desert in the rain shadow of the 3000 meter-high Haleakala volcano. At sea level the temperature hardly changes, while at the summit the temperature swings wildly and frost and snow are regular occurrences.The few plants and animals that found their own way to these new islands quickly evolved and diversified to exploit habitats that were largely free of natural controls and competitors. If Charles Darwin had come to Hawaii instead of the Galapagos, he would still have had plenty of inspiration for his theory of evolution. It's interesting to note that Hawaii's terrestrial ecosystems evolved without mammals (except for one endangered bat), reptiles, amphibians, or even ants or mosquitoes. Unfortunately, the original natural habitats of Maui and the other islands are largely gone.


Standing at the edge of the Haleakala Crater (3000 meters A.S.L.) looking towards Vancouver

After humans (Polynesians and then Europeans) discovered these young islands, hundreds of new species began to flood in and evolutionary hell broke loose. These days native plant communities can only be found in the most rugged and inaccessible valleys and even these small remnants are being invaded, degraded, and replaced by alien plants and animals. It is said that 75% of extinctions in the USA have been endemic Hawaiian species and many more are sure to follow.

Maui is both fascinating and intimidating for an amateur naturalist because you can find almost anything from almost anywhere. Alien species arrive almost daily, and profound ecological relationships are developing that range from symbiotic to lethal. Many species are brought in intentionally, but even more arrive uninvited and unannounced. After only a couple of centuries the plantscape is almost completely changed and it will continue to change at incredible speed.

A chameleon hanging out in an outdoor cafe near Kula. Maui is a long way from Madagascar.

Let me offer one small example of adaptation that I noted during my short stay on Maui. On the very first day I was shocked to see numerous Monarch butterflies (Danaus plexippus) feeding on the white flowers of an unfamiliar (nearly everything was unfamiliar) bush that liked to climb on the larger coastal trees.
How did monarchs get here and how did they survive? I knew that adult monarchs are not particular about the flowers they feed on, but the caterpillars can only eat Asclepias milkweeds or their close relatives. Perhaps something interesting was going on.
While there are nearly a thousand native Hawaiian moth species, there are only two native butterflies, the Kamehameha (Vanessa tameamea - a close relative of our Painted Lady), and the Blackburn's Blue (Udara blackburni). After purchasing a local field guide, I was able to figure out part of the story. The bush that the adults were feeding on was called Noni (Morindra citrifolia), a "cultural plant" probably brought by the Polynesians a thousand years ago. More to the point, there are at least three milkweeds introduced to Maui that the young monarchs could be eating: a brightly colored garden plant from the West-Indies; a roadside weed with lemon-sized fruits from Southern Africa; and a more distantly related bush from south-east Asia called crown flower.
Monarch butterfly feeding on Noni flowers

Along with more monarchs and breathtaking tropical flowers, I also observed a few non-native birds for the first time. These included Java Sparrows, Common Mynas, Japanese White-eyes, Northern Cardinals, and Red-crested Cardinals.
Some Cardinal-like birds that I didn't see were Red-whiskered and Red-vented Bulbuls. They are still fairly rare on Maui, but they are quite common on the island of Oahu, and that is where something very interesting is happening to monarch butterflies.




Red-whiskered Bulbul (Wikopedia Creative Commons Attribution 2.0)

The following was gleaned from The White Monarch ( monarchwatch.org). Monarch butterflies are seldom bothered by birds because they are full of foul-tasting milkweed toxins. However, Bulbuls, insect eating birds originally from Asia, are not deterred by this chemical defense. What's more, Monarchs that feed on Asian crown flower bushes contain significantly less poison. Perhaps Bulbul predation is selecting against the monarchs' flamboyant black-on-orange colour scheme and favouring a rare and more muted black-on-white pattern. Although the Bulbuls only escaped on Oahu in the 1960's, between 1% and 10% of the local monarchs are now white!
So what does it all mean? There were a couple of lessons that I took home with me. The first is that "Mother Nature" isn't always very motherly. She is just as likely to be heartless and unfair. Life's first and foremost rule is "adapt or die". This means that the naturalized alien species of Hawaii are just as vulnerable to predation and competition from new aliens as the endemics.
The other lesson is that isolated islands are very useful models for explaining what happens on continents. On an island, the effects of alien species tend to happen much more quickly and those effects are also much easier to observe and understand. The ecological dramas that are playing out in the Hawaiian archipelago are examples of our own situation. The same social, economic, and historical factors apply and we have an opportunity to learn from the ongoing Hawaiian experiment.
While it's true that Maui is still a beautiful and pleasant place to go on vacation, most of the "natural" beauty you see is an illusion. Maui is far from an unspoiled jewel and the attractive alien species that thrive there now are vulnerable to future invasions of alien weeds, vermin, parasites, and diseases. The same is true of Alberta but the process of change hasn't gone as far or as fast.








Rickrack Banksia from Australia growing in a Maui garden. Many of the exotics cultivated in Hawaii are endangered in their native habitat.

We can also learn from the people of Hawaii and the way they are adapting to alien species. As in our own society, the attitudes and reactions range between chauvinism, denial, resignation and activism. The island model holds true with conservation efforts as well. On Maui the alien species issue has moved farther and faster than it has on the continent. More people are aware of alien species and they are doing more to manage them. Despite Hawaii's small population, they have some world-class programs to study, monitor, and manage the problem. For example, the Hawaiian Ecosystems At Risk (HEAR) site is a gold mine of information and ideas for conservationists the world over.
Islands show us that all the processes of evolution are still going on. Extinction and replacement can happen very rapidly, but sometimes adaptation can also happen rapidly. We live in very interesting times.

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