Dispersal to the Hawaiian Islands

1. Dispersal to the Hawaiian Islands By: Stacey Falk

2. Facts: • 2,500 miles of ocean separate North America from the Hawaiian Islands. • 3,500 miles of ocean between the small Marianas Islands and the Hawaiian chain. • The Hawaiian chain has never been connected to a land mass. www.worldatlas.com

3. How then, did plants and animals cross the large oceanic distance to arrive on the Hawaiian islands? • Transportation through the air • Attached to Birds • Fruits eaten by Birds • Drifting in Seawater

4. Questions: • What are the two ways in which plants and birds are able to travel the long-oceanic distance to the Hawaiian islands by drifting through the air? • How can plants and animals be dispersed to the Hawaiian islands by attachment to birds? • What accounts for the largest means of seed dispersal to the Hawaiian islands than any other mechanism? • What adaptations must a plant or seed have for dispersal by flotation in seawater? • What advantage does “rafting” play in dispersal?

5. Drifting in the Air Organism must be so small, or reproductive structure so small, that it’s dust-like. • Plants that reproduce by means of spores such as ferns, mosses, algae, and lichen • Spores so small that a line of a thousand of them end-to-end would be an inch long • Nephrolepis exaltata

6. Drifting in the Air • Fern spores more successful at reaching Hawaiian island then seeds of flowering plants • 1.4% of the 255 hypothetical original flowering plants were dispersed by air flotation • Ohia lehua tree has seeds small enough to suggest dispersal through the air www.roddyscheer.com Metrosideros polymorpha

7. Drifting in the Air • Organism must be able to fly • Insects. • Research by entomologist, J. Lindsey Gressitt. Sampled air at high attitudes and at sea, resulted in a large amount of insects trapped. Those caught were the same basic groups of insects as those native to Hawaii. • Passive flight and small body size of insects accounts for their dispersal to the island. • Birds. • Travel through active flight such as migratory birds, marine birds, shore birds and waterfowl. • Land birds underrepresented. Pluvialis dominica fulva

8. Drifting in the Air • Air currents are a crucial factor in the role of air as a dispersal mechanism. • Northern Hemisphere jet stream is a semi-permanent ultra-high-speed wind which occurs at 30-40 thousand feet and could account for such dispersal.

9. Attached to Birds • Seeds can become embedded in mud on feet or other parts of birds • Estimated 12.8% of the hypothetical original flowers arrived this way • Possible if seeds are small, plants grow in wet, muddy places, and if migratory birds commonly visit Lobelia

10. Attached to Birds • Plant and animals become attached to birds feathers by a viscid substance • Accounts for 10.3% of hypothetical original flowers • When Plantago seeds become wet they develop a slimy covering, which dries and adheres to surfaces, such as feathers of a bird P. Major seeds

11. Attached to Birds • Some Seeds are coated with a sticky substances, like rubber cement. This viscid substance makes it very easy to become attached to birds feathers. Pisonia umbellifera Boerhavia diffusa

12. Attached to Birds • In the dispersal of some fleshy fruits a viscid substance is involved. • Clermontia have fruits which break open at maturity, revealing tiny seeds which contain a white latex. This latex helps to stick the seeds to the birds feathers. Clermontia arborescens

13. Attached to Birds • A mechanical device such as barbs, hooks, bristles, prongs, or stiff hairs can attach seeds to feathers. • Accounts for estimated 12.8% of native flower dispersal. • Bidens, calledthe beggar tick, have sharp hairs and prongs which are barbed and easily attach to surfaces. Bidons pilosa

14. Fruits Eaten by Birds • Fruits eaten by birds was the most effective means of seed dispersal to the Hawaiian Islands. • Fruit-eating birds ate the seeds, carried them internally, and excreted them on Islands • Accounts for dispersal of an estimated 39% of the 255 original plants Vaccinium reticulatum Cassytha filiformis

15. Fruits Eaten by Birds • Large percentage of fruits and seeds attractive to birds in Hawaiian flora. • Fruit color not as important as fruit texture in attracting birds. • Abundance of all colors and textures in the Hawaiian flora. Tetraplasandra hawaiiensis Has hairy gray fruits

16. Fruits Eaten by Birds • Fleshy fruits are well represented on the Hawaiian islands. This is true even among plant families which mostly have dry fruits. • Indicates that fleshy fruits is more successful for long-distance dispersal • Most members of the mint family have dry fruits. The Hawaiian mints, such as Stenogyne, are unusual in that they have fleshy fruits. Stenogyne

17. Fruits Eaten by Birds • Shore bird thought to play major role in transporting of fruits and seeds to the Hawaiian Islands • Migrate all of the Pacific • Eat large amounts of fruits and seeds • Capable of retaining fruits and seeds for days • Common migratory shore birds include the Pacific golden plover and the bristle-thighed curlew Pluvialis dominica fulca Numenius tahitensis

18. Drifting in Seawater • 14.3% of native flowering plants adapted to oceanic drift. • Adaptations for dispersal in seawater: • Seeds or fruits capable of floating. • Seeds or plant parts must be able to resist seawater for weeks. • Must arrive alive on beach and be able to grow there. Pandanus tectorius

19. Drifting in Seawater • The pink-flowered morning glory has seeds cable of floating in seawater • Stems and leaves adapted to float in seawater and establish when they float on the beach, such as the Portulaca Ipomoea pes-caprae Portulaca oleracea

20. Drifting in Seawater • Plants which grow well along the beach and have seeds resistant to seawater, but have seeds and fruits unable to float take advantage of “rafting” • “Rafting” is the flotation of an entire plant, or entire mats of vegetation • Estimated 8.5% of hypothesized original flowering- plants dispersal Acacia koa Gossypium sandvicense

21. Questions Overview • What are the two ways in which plants and birds are able to travel the long-oceanic distance to the Hawaiian islands by drifting through the air? • Organism must be so small, or reproductive structure so small, that it’s dust-like. • Organism must be able to fly

22. Questions Overview: • How can plants and animals be dispersed to the Hawaiian islands by attachment to birds? • Embedded in mud on feed or other parts of birds • Attached to feathers by a viscid substance • Mechanically attached by a device such as barbs, hooks, bristles, prongs, or stiff hairs

23. Questions Overview: • What accounts for the largest means of seed dispersal to the Hawaiian islands than any other mechanism? • Fruits eaten by birds, then carried internally, and excreted on the islands.

24. What adaptations must a plant or seed have for dispersal by flotation in seawater? • Floatability • Seed or plant part able to resist seawater for weeks • Must arrive alive on the beach and be able to grow there • What advantage does “rafting” play in dispersal? • Seeds and fruits unable to float but are resistant to seawater can arrive through flotation of an entire plant or mats of vegetation Questions Overview:

25. References: • Carlquist, Sherwun. “Hawaii: A natural history”. The natural history press. Garden city, new York. 1970. Pg. 81-111. • Sohmer, S.H.; Gustafson R. Plants and flowers of Hawai’i. University of Hawaii press. Honolulu. 1987. • Images Hawaii. Hawaii: plants and animals.http://imageshawaii.com/general_plants.html • Star, Kim. Plants of Hawaii. March 12, 2003. http://www.hear.org/starr/hiplants/images/index.html