bob@islenet.UUCP (Bob Cunningham) (07/03/85)
Keith Doyle wrote: > I can see that again we can better explain the 'purpose' for galaxies > as being required so that man can navigate. Note that the horsehead > nebula is actually a signpost pointing directly to the Hawaiian Islands. [reference omitted] (Presumably why we get so many tourists out here :-) More apropos of the discussions in this newsgroup, the Hawaiian islands are a remarkably good place to observe evidence of evolution in action. Stretching out over 1600 miles in the oldest, broadest and deepest of the oceans, the Hawaiian archipeligo is the most isolated island group in the world. The nearest continent lies over 2000 miles away, the nearest group of atolls (low islands) are 850miles to the south, and the nearest group of volcanic (high islands) is more than 1000 miles away. The islands are geologically young, and their geological development seems clear and relatively easy to understand. There is are a number of remarkably diverse ecological environments. At the summit of Mauna Kea, a subpolar desert exists at 13,000 feet above sea level where the mean low temperature during the summer is near freezing. More common are the lush tropical rainforests, hot arid lava fields, sandy beaches, rocky shorelines and coastal bluffs. Given the island's isolation, their geological youth, and the variety of environments avaiable, it's not surprising that the native assemblage of organisms is unique. In fact, more than 95% of the native flora and fauna is endemic, occuring no place else in the world. Unique species of birds include the whole sub-family of Drepanidinae (honeycreepers) including species with some bizarre bill adaptations; several unique finches, a unique crow, two unique duck species; and a goose (the nene) that prefers high, sparely vegetated lava fields. Unique plants include several pioneer species that first inhabit new lava flows; the Hawaiian raspberry which is thornless; mints mostly scentless; nettles that are harmless; violets that are shrubs; and the spectacular Haleakala silversword. There are no native land amphibians or reptiles, and only one native land mammal (a bat). There are no true native freshwater fishes, and about 34% of the coastal marine fish are endemic. Endemic insects probably number about 6500 species, but major groups (e.g. ants) weren't present until introduced by man. There are, I'm told, many fascinating unique adaptations. The Hawaiian Drosphilia (a genus of fruit fly) has been used extensively during the last several decades in genetic research. Its rapid life cycle compresses the time in which evolutionary changes can occur, and it's not uncommon to be able to create a new species in the laboratory. Hampton Carson's work (perhaps the most detailed analysis of a single genus ever made) strongly indicates that the 600+ species of Drosphilia in Hawaii probably evolved from a single progenitor. Polynesian settlers -- first arriving about 1000 years ago --- had a major impact on the islands. Considerably greater changes have resulted from the discovery of the islands by "haoles" (literally "foreigners") 200 years ago. Most of the native forests have been cut down, and virtually all of the low-lying areas have been cleared for crops, rangeland, and subdivisions. These recent major environmental changes account for the extinction of more than 23 species of endemic birds, about 255 species of plants, and uncounted numbers of endemic insect species. Hawaiian birds make up roughly 1/2 the U.S. list of endangered species, and -- at last count -- 894 plant species (roughly 1/3rd of the native plants) are threatened with extinction. -- Bob Cunningham {dual|vortex|ihnp4}!islenet!bob Honolulu, Hawaii