L earning Objective 21

A. Dr. F.R. Fosberg was a botanist who was an expert in the flora of the Pacific Islands, including Hawai'i. In 1948 he analyzed the Hawaiian flora and hypothesized that the some 1,000 plus Hawaiian native flowering plant taxa (plant groups at species level or below, such as subspecies) could have been derived from as few as 272 original plants, arriving in Hawaii from other geographical regions of the world. These plants could be called the "colonists" because they had successfully become established in Hawaii.

B. How can a botanist make this determination?

1. With Fosberg's broad knowledge of plants throughout the Pacific, he already knew which species were indigenous to Hawaii (about 10%).

2. The other 90% are the endemic species which frequently showed a relationship or affinities to other species elsewhere in the world. This could mean that species from outside of Hawaii were the source of the new Hawaiian species or that both could be descendants of another related species. So it would not be unusual for someone with his background to make some pretty solid conclusions about native Hawaiian flora sources.

C. Possible global sources of the ancestral plants.

1. Fosberg further identified the parts of the world surrounding Hawaii which would be the most likely sources of ancestral species, based on strongest similarities of plants in the two areas. (Figures 21-A/B summarizes his findings.)

2. The greatest source of ancestral plants of Hawaiian natives, 40%, is the Indo-Pacific region. This area is roughly the sweep of islands, starting from the Indonesian region in the west and continuing east and southward, to all the islands throughout the Pacific, including the vast expanse of ocean itself. (See Figure 20-B)

3. This region, though not the closest land to Hawaii, clearly represents a similar tropical climate and growing conditions most closely matching Hawaii's. Plants must not only arrive at the islands but secondly, and importantly, survive, and eventually thrive. Perhaps more plants came from other regions of the world, closer to Hawaii, but maybe fewer survived!

4. The next source of ancestral species is the North American continent. It is the closest land mass to Hawaii. However, it is not the largest source of plants perhaps because its climate is not as similar as the more tropical areas of the Indo-Pacific regions.

5. With 16%, Australia and New Zealand are a close third for ancestral plant sources. The northern parts of these areas are tropical or mild, so plants from that area would be "at home" in Hawai'i.

6. 5% are pan-tropical, which means they are found world-wide with their original homeland in the tropics. 10% of the origins could not be determined and the smallest group, 3 % are from the most northern part of the world, Alaska to the east, and the Asian continent to the west.

A. "Winning the Lottery" or will this plant make it to Hawaii?

1. The second part of Fosberg's theory has to do with the time element involved in the dispersal and successful establishment of the new colonists to the Hawaiian Islands.

2. Given the present-day islands with an age of 5-6 million years, or the whole chain anywhere from 30 to 70 million years, the shortest time period in which one new plant could become established would be 20 to 30 thousand years or as much as 100 thousand plus years, which would give enough time to account for the 272 original colonists.

3. It is an improbable or unlikely event that any seed or progagule (seeds, spores or any plant pieces which gives rise to a new plant) will make it to Hawai'i over two and half thousand miles away. However, when thousands of years are factored into the dispersal time, this improbable event becomes almost a certainity that some plants will make it!

B. "The Great Hawaiian Lottery".

1. Sometimes this is referred to the sweepstakes or winning the lottery by the native Hawaiian plants which won by making it to the islands. To make an anology, it is highly unlikely that one person, entering a sweepstakes only once, will win. However, if this person were to enter every day, for 100 or 1,000 years, his/her chances of winning greatly increases.

2. So it is with the winners of the "Hawaiian plant lottery". They arrived, but winning or becoming a permanent part of the flora is more difficult than just arrival. Now they must survive and thrive to become part of the native Hawaiian plant flora.