2. Dubautia with 21 species, has many species on the Big Island as well as on other islands. The species can be shrubs, semi-shrubs and even a vine. It is the youngest genus found in greatest diversity on the youngest island. Dubautia is still in process of active speciation, a young genus, unlike Wilkesia, which is considered a relict genus (one which is a remnant). (Photo by Priscilla Millen)

3. World famous Argyroxiphium genus has five species members, called green and silver swords 'Ahinahina, for the Haleakala species. Many form large rosette (a plant-growth form where all the leaves grow close together in a big whorl usually at the ground level or at the end of a long stem). They are found from the alpine deserts to the bogs of Hawai'i. (Photo by Charles Lamoureux)

C. Through the work of Dr. Gerald Carr at University of Hawaii and Dr. Donald Kyhos of University of California at Davis, there is evidence that all the silversword alliance members evolved from a single seed arriving about 5 million years ago. Their original colonist source is related to the 99 species of "tarweeds" found in California and Mexican deserts today. The adaptive radiation of these Hawaiian species in the Silversword Alliance from a single colonist plant is quite a spectacular evolutionary event.

1. The proposed ancestors of the colonist plant are found in North America in the dry areas of California and Mexico. They are shrubby, sprawling plants, not as striking as the silverswords but have important structural similarities. They are called "tarweeds" because of sticky substances found on the flowers and fruits. You can guess what way they probably got to Hawai'i! They hitched a ride on a bird feathers!

Tar Weed

Silversword

The relationship between the Hawaiian silversword alliance and these "tarweeds" was determined by "screening" the present-day tarweeds, mostly by genetic tests, to find closely-related descendants.

a. When two were found that seemed to be likely relatives, they were crossed and, produced healthy hybrids with their Hawaiian "cousins." This means that they still have a great deal of genetic material in common and are not that "distantly" related, though they are far apart in space and in time -- by hundreds of miles and millions of years!

b. A California tarweed called Raillardiopsis muirii, found in the Southern Sierra Mountains on sandy soils of a granite outcrops, was crossed with Dubautia laevigata,, from the wet forests of Kaua'i. A hybrid formed between these two unlikely plants and was dubbed the "Transoceanic Hybrid."

c. The creation of this artificial hybrid supports the genetic closeness of the two groups of plants found on opposite sides of the Pacific. Chromosomes sets from two different parents can form a successful hybrid only when they are closely related. Thus chromosome compatibility can tell us with a great deal of certainty that these two plants must be related. We do not have to be standing on the shore million of years ago to watch the first colonist arrive to come to this conclusion.

d. Another important outcome of this study was to inform the scientific world that long-distance dispersal is more significant than previously suspected.

2. Why is there much diversity in the Hawaiian silverswords and less in the California tarweeds?

This can be answered in part by the fact that relatively few different kinds of plants (disharmonic flora concept) were able to establish in Hawai'i. This means that the ones that did had far greater opportunities, with all the available habitats in which to live. Many different forms developed in response to the different habitats, the specific locations where they live.

3 In further studies, it has been shown that all three genera can hybridize and a number do in the wild where their habitats overlap. In the crater of Haleakala, the silverswords and a DUBAUTIA species form hybrids in certain intermediate locations.

(See Sohmer and Gustafson,pp. 34-35.)

This means that all three genera of the Silversword alliance share the same gene pool, thus making the pool larger than if each species is restricted to its own genus, the usual case. This clearly allows for greater opportunity to survive because of the greater genetic diversity within the alliance.

D. The silversword alliance story fits the theories of dispersal and colonist characteristics in at least five major ways:

1. Dispersal from North America

2. Adaptive radiation influenced by the varied life zones of Hawai'i.

3. Survival with small gene pool by forming hybrid "bridges" between genera which can allow gene flow between groups.

4. From weedy annual or low growing semi-shrubs to massive rosettes (like the Silversword) and other larger woody plants.

5. Bird dispersal by sticky fruits.

For further information on adaptive radiation in the silversword alliance, visit Dr. Gerald Carr's Web site.

E. The Silversword has many features which allow it to live successfully in the harsh environment of alpine desert of Haleakala.

1. The long thin curved leaves allow for sufficient surface for light absorption without excessive water loss. The gray hairs on the leaves are even curved in such a way as to re-radiate the excessive light and heat of the sun away from the plant. It is called 'Ahinahina by the Hawaiians, which means very gray (gray-gray).

2. The spaces between leaf cells are filled with a gelatinous substance which helps to prevent water loss and, perhaps, to protect from extreme cold, also part of the alpine desert environment. The Silversword can also absorb great amounts of water, especially when the large inflorescence is being formed.

3. The plants live about 5 to 15 years and bloom only once, in July. The mature plant can be six feet high with a massive inflorescence covered with maroon flowers. Goats once threatened silverswords with extinction. While goats have been fenced out of Haleakala, now the Argentine ants threaten by their predation on the silversword pollinator.

A. Large colorful red-purple twisted flowers are bird-pollinated and small white inconspicuous ones are pollinated by small crawling beetles and other insects. In Hawai'i there are few native bees and only one native butterfly.

B. Many native plants have small, inconspicuous flowers:

1. There are few native bees to Hawai'i and only one native butterfly. Few large pollinators, such as social honey bees, larger butterflies and moths, made it to the islands for obvious reasons.

2. As a result, a number Hawaiian flowers are small, colored greenish/white, and shaped flattish or cupped slightly since the pollinators are small insects and beetles, which are not generally attracted by bright colors or large flowers as are bees and butterflies.

C. Naupaka species are adapted to different pollinators.

1. In the Scaevola genus (Naupaka) the familiar white, half-flower is found in many of the lowland species which reflect pollination by small insects.

2. On the other hand, a flower of a rain forest species, 'ohe naupaka (Scaevola glabra) has curved tubular yellow flower which is clearly bird-pollinated.

D. Bird-pollinated flowers found in the native flora are usually bright colored, larger, and frequently with a curved corolla (the structure made up of all the petals).

1. Some good examples are the native Koki'o (Hibiscus), a related genus such as hau kuahiwi (Hibiscadelphus) and 'ohi'a (Metrosideros), all which have flowers of bright colors or produce copious amounts of nectar. The HONEY CREEPER native birds are important pollinators of many native plants.

Koki'o ula

Hau kuahiwi

'Ohi'a lehua

>2. The many extinctions and very low numbers of the honey creepers today threaten the survival of the many native plants that depend on their pollinating activities.

A. Why are Hawaiian native plants not as competitive as many introduced plants?

1. They are narrowly adapted to very specific climatic conditions which exist in small regions on the islands.

2. Originally they had little competition for space because competition was low in the developing flora. That is related to few new plants arriving over a long time.

3. Competitive plants develop where there is a lot of disturbance in the environment and are often found where humans have been intensively active for thousands of years. Hawai'i was free from humans for millions of years!

B. What is the impact of introduction of non-native plants?

1. Introduction of "weedy", non-native plants from other parts of the world has greatly impacted native plants. Wherever a disturbance is created in the Hawaiian environment -- a road, clearing for farming, or rooting by wild pigs -- the introduced plants often can move in and become established more quickly than the native.

2. For example, Banana poka (Passiflora mollissima) doesn't even wait for an opening, but grows right over the natives, smothering them! A more recent threat is the ivy or scarlet-fruited gourd (Coccinia grandis), introduced in the mid '80's and already a serious vining pest on many islands. The Christmas berry tree (Schinus terebinthifolius) arches over and shades out native plants. Strawberry guavas (Psidium cattleianum) grow so thickly that nothing else can grow between them.

Banana Poka

C. Exceptions.

1. Some native Hawaiian plants are adapted to harsh conditions such as the coastal zone and recent lava flows, and are able to compete fairly successfully with introduced plants.

2. Uluhe fern (Dicranopteris) has adapted well to road cuts and other human-made disturbances, but its original adaptation is to landslide areas, a natural phenomenon of the Hawaiian environment.

3. The tree fern, 'Ama'u, (Sadleria), an endemic genus, and 'ohi'a lehua (Metrosideros polymorpha) are other native plants which can aggressively colonize new lava flows.

Uluhe Photo by R. Saito

'Ama'u Photo by E. Petteys

A. In conclusion, the adaptations of colonist plants to their new island home did not prepare them for the future, when humans physically altered the landscape and brought introduced plants and animals from which native plants lacked protection. Furthermore, it would probably take thousands of years for them to adapt to the altered, human-impacted environment. A massive change has occurred in a few hundred years and the native plants don't have the luxury of time.

B. As a result, the Hawaiian flora (along with much of the fauna) is one of the most endangered in the world.

1. There have been more animal and plant species extinction in the Hawaiian Islands than in all of the rest of the United States.

2. As a result, Hawaii - with 0.2% of land area in the United States - has almost 50% of endangered plant species for the country

3. If conditions are not reversed, another significant percentage of native plants is predicted to become extinct in the next 20 years.

4. Dr. Gary Ray, representing the Center for Plant Conservation, an organization dedicated to preserving endangered plants, has found that there are 120 taxa (groups of plants at the species and subspecies level) with 20 or fewer individuals left in the wild. He estimates it would take a million dollars just to save them from immediate extinction.

5. Reasons given for saving native plants and animals often stress the practical side of their value and what's "in it" for humans. Unknown chemical properties of medicinal value, genetic content that could become a lifeline to humans by saving crop or other valuable plants, their stabilizing role in the ecosystem, and even their inherent beauty or appeal, have all been given as "good reasons" for saving any kind of plant or animal.

Maybe we should look at the problem from an ethical and moral stance. Do we need to justify their value only in terms of their use to us? What is it about us humans, an integral part of the web of life, which permits us to take over much of the livable surface of the planet to the exclusion and destruction of numerous plant and animal forms, many of which have been on the planet much longer than we? In respect and in valuing all forms of life, I hope that we can create safe and sustainable havens for many of the special plant and animal communities around us. Certainly we can co-exist! To do less would be less than human.