Hawaiian Islands; patterns of plant evolution
The Hawaiian Archipelago comprises a chain of islands, islets, reefs and atolls stretching more than 2500 km in southeast-northwest direction across the middle of the Pacific Ocean. It is the largest and most isolated group of oceanic islands in the world, located more than 4000 km from the nearest continent. There is a total of about 130 islands, islets and atolls but 99% or more of the total land area lies within the eight main islands in the southeastern part of the chain. The total land area is about 10 400 km², with the largest island, Hawaii or Big Island, comprising more than 60% of the total area. The islands are truly oceanic in the biological sense, they have arisen through volcanic activity on the sea floor and have never been connected to a continent. The islands are tops of volcanoes rising 5000-9000 m from the ocean floor; the highest top of Mauna Kea reaches about 4200 m above sea level.
The location of the Hawaiian Chain between about 19° and 28° N latitude places it well within the tropical region. Although the archipelago as a whole is relatively uniform as to daylength and temperature throughout the year, there is a great diversity within the archipelago. There are examples of tropical rainforests and deserts in close proximity and rainfall within the same island may vary from 300 to 12000 mm per year. This means great variations in vegetation cover and a wide range of habitats.
What is interesting from a biological point of view is that the islands are truly oceanic and are located far from the nearest continent. Hawaii illustrates several characteristic features of such islands in that the endemism in flora and fauna is high and that there are numerous beautiful examples of adaptive radiation among vascular plants and several groups of animals.
There are about 1000 species of indigenous vascular plants in the Hawaiian Islands, about 90% of which are endemic. The largest plant families are Campanulaceae (110 native species, 109 of which are endemic; 5 or 6 endemic genera) and Asteraceae (91 native species, 90 endemic).
If introduced species are included, the total number of vascular plants in Hawaii is about 2000. Many introduced species are serious threats to the indigenous flora and many indigenous and endemic species have gone extinct. This is an ongoing process.
During several years I was a Research Associate in Botany at the B. P. Bishop Museum in Honolulu. My research in the Hawaiian Islands was within two widely separate fields, vascular plants and Myxomycetes (acellular slime moulds). The research on vascular plants focused on the family Amaranthaceae. My work on Myxomycetes was part of the Hawaiian Biology Survey project.
The location of the Hawaiian Chain between about 19° and 28° N latitude places it well within the tropical region. Although the archipelago as a whole is relatively uniform as to daylength and temperature throughout the year, there is a great diversity within the archipelago. There are examples of tropical rainforests and deserts in close proximity and rainfall within the same island may vary from 300 to 12000 mm per year. This means great variations in vegetation cover and a wide range of habitats.
What is interesting from a biological point of view is that the islands are truly oceanic and are located far from the nearest continent. Hawaii illustrates several characteristic features of such islands in that the endemism in flora and fauna is high and that there are numerous beautiful examples of adaptive radiation among vascular plants and several groups of animals.
There are about 1000 species of indigenous vascular plants in the Hawaiian Islands, about 90% of which are endemic. The largest plant families are Campanulaceae (110 native species, 109 of which are endemic; 5 or 6 endemic genera) and Asteraceae (91 native species, 90 endemic).
If introduced species are included, the total number of vascular plants in Hawaii is about 2000. Many introduced species are serious threats to the indigenous flora and many indigenous and endemic species have gone extinct. This is an ongoing process.
During several years I was a Research Associate in Botany at the B. P. Bishop Museum in Honolulu. My research in the Hawaiian Islands was within two widely separate fields, vascular plants and Myxomycetes (acellular slime moulds). The research on vascular plants focused on the family Amaranthaceae. My work on Myxomycetes was part of the Hawaiian Biology Survey project.
Selected publications:
Eliasson, U. H.: The evolutionary patterns of the plant family Amaranthaceae on the Galápagos and
Hawaiian Islands. - Journal of the Torrey Botanical Society 131: 105-109 (2004).
Eliasson, U.: Speciation patterns of Amaranthaceae in isolated habitats: examples from the Galápagos and Hawaiian islands. - XVI International Botanical Congress. St. Louis. Abstracts volume, p. 88 (1999).
Eliasson, U. H.: Floral morphology and taxonomic relations among the genera of Amaranthaceae in the New World and the Hawaiian Islands. - Botanical Journal of the Linnean Society (London) 96: 235-283 (1988).
Eliasson, U.: Speciation patterns of Amaranthaceae in isolated habitats: examples from the Galápagos and Hawaiian islands. - XVI International Botanical Congress. St. Louis. Abstracts volume, p. 88 (1999).
Eliasson, U. H.: Floral morphology and taxonomic relations among the genera of Amaranthaceae in the New World and the Hawaiian Islands. - Botanical Journal of the Linnean Society (London) 96: 235-283 (1988).
UNO ELIASSON
University affiliation:
University of Gothenburg
Department of Biological and Environmental Sciences
Email:
uno.botan@gmail.com
Scientific publications:
Click here (pdf) >>