L earning Objective 23

A. Hawaii has a disharmonic flora.

Hawaiian flora is not in "harmony" with rest of world, i.e. it is not representative of flora in nearest continental and island source areas. Whole families and groups are missing or underrepresented.

B. There are two possible reasons why groups are missing:

1. Those plants with large or clumsy seeds, fruits or propagules cannot be moved readily by the wind, water and wings. In other words, they are not easily dispersed. Conversely, most of the plants that came here are small seeded/fruited which means they are more easily dispersed.

2. Some may simply not be here by chance, probably like the Tropical Almond (Terminalia catappa) which is found on many other Pacific Islands. Remember, dispersal to the Hawaiian Islands is like a lottery. Some made it to the Hawaiian Islands and others did not.

C. Examples of disharmonic plants.

1. The Rose family (Rosaceae) is very large worldwide with 100 genera and 3,000 species, like apples and roses. Yet are only a few native plants in Hawaii, like Osteomeles anthyllidiflora, or 'Ulei, which represent this family.

2. The lack of tropical forest trees commonly found in the tropics all over the world is one of the most distinctive features of the Hawaiian forests. A major factor for this deficiency could be as follows:

Most forest trees have large seeds, which provide a large amount of stored food to help a seedling get established in the shady area under mature trees in the forest. These seeds would be difficult to disperse, because of their size, either by wind or even birds which could not eat or carry such seeds great distances. Few are adapted to floating in saltwater, which is usually far from where they are growing.

3. There are no native gymnosperms, such as cycads, pines, or podocarpus. They also disperse poorly over great distances.

II. The Rate Of Endemism of Hawaiian native flowering plants is +89%, the highest in the world. Two major factors accounting for this are as follows:

A. Isolation:

Because the colonist plant cannot breed back to its original population, it becomes separate and often distinct by the processes of the Founder's Effect and genetic drift (a pattern of establishment or elimination of genetic traits rather rapidly, due to chance primarily in small gene pools). (See Figure 15-A to review this concept.)

B. Different climatic zones:

There are more different climatic zones in the smallest area in Hawaii than anywhere else. Each zone will favor certain traits and not others. Plants adapted to the dry coast will not do well in the rain forest and vice versa. The original colonists will have to change: no way they can stay the same!

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