Geographic Isolation and Biological Processes

Geographic Isolation and Biological Processes

The extreme geographic isolation of the newly formed Hawaiian Islands made it difficult for new species to reach the Islands and become established. However, as plants began to take hold and an abundance of rich and diverse habitats formed from the shorelines to the river valleys to the mountain peaks, new species that did make it to the Hawaiian Islands were more likely to thrive, reproduce, adapt to new habitats and food sources, and evolve into unique Hawaiian species.

In this way, over a period of millions of years, from the relatively few original colonizing species of the Hawaiian Islands many thousands of unique Hawaiian species evolved—plants, insects, bats, seals, birds, fish and a multitude of other organisms that took advantage of the ecological opportunities (niches) provided by the wealth of different native landscapes and ocean habitats in the Hawaiian Islands.

The evolutionary process of adaptive radiation describes how so few colonizing species in the Hawaiian Islands managed to evolve over many millennia into a fascinating array of endemic flora and fauna, including thousands of species found nowhere else on Earth. For example, a single colonizing plant species evolved into more than 120 endemic Hawaiian species in the Campanulaceae family (subfamily Lobelioideae).

The 1999 Manual of the Flowering Plants of Hawai‘i[i] documented 956 native Hawaiian flowering plants (850 endemic), yet much about the flora of the Hawaiian Islands remains undiscovered. Just since the Manual was published in 1999, new scientific explorations and botanical analyses have yielded dozens of new species discoveries.

New research on plant characteristics and taxonomy of Hawaiian plants has also led to hundreds of new refinements of classifications of species, subspecies, and varieties. According to the Records of the Hawaii Biological Survey for 2000,[ii] there are currently at least 1,882 documented native Hawaiian plants (1,159 endemic), including 1,163 native flowering plants (918 endemic). (See Overview of Native and Polynesian-Introduced Species of the Hawaiian Islands, Chapter 5.)

The high rate of new species discovery in the Hawaiian Islands as well as the largely incomplete state of properly classifying the diverse flora and fauna of the Islands may both be attributed to the rapid rate of new species development in the archipelago as well as Hawai‘i’s isolation in the middle of the Pacific Ocean.

Just in the Cyanea genus of the Campanulaceae family, five new species were discovered. Based on new analyses of botanical characteristics, the genus Lobelia, one of the six endemic genera of Campanulaceae family, was entirely eliminated, and the endemic Lobelia species were reclassified into two new genera (Neowimmeria and Galeatella).

New Hawaiian plant species discoveries and new botanical classifications are documented in the 2002 Electronic Supplement to the Manual of the Flowering Plants of Hawai‘i.[iii] For more information see the Introduction to the Native Plants and Ferns section of this text in Chapter 8, which includes a summary of the significant changes documented in the Electronic Supplement.

One notable change is that kou (Cordia subcordata), a tree long thought to be a Polynesian introduction (and documented as such in the 1999 Manual of the Flowering Plants of Hawai‘i [iv] ) was reclassified as indigenous, and thus is considered a native Hawaiian species. Note: This reclassification of kou was based on a discovery of subfossil seeds and reported in a study by David A Burney and others entitled Fossil evidence for a diverse biota from Kaua‘i and its transformation since human arrival.[v]



[i] Wagner, Warren L., Herbst, Derral R., and Sohmer, S.H. Manual of the Flowering Plants of Hawai‘i: Revised Edition, Volumes 1 and 2. Honolulu: University of Hawai‘i Press; Bishop Museum Press, 1999.

[ii] Evenhuis, Neal L., and Eldredge, Lucius G., Editors. Records of the Hawaii Biological Survey for 2000. Bishop Museum Occasional Papers, Number 68, 69. Honolulu: Bishop Museum, 3/25/2002.

[iii] Wagner, Warren L., and Herbst, Derral R. Electronic Supplement to the Manual of the Flowering Plants of Hawai‘i. Internet site: http://rathbun.si.edu/botany/pacificislandbiodiversity/hawaiianflora/supplement.htm, 3/05/2002.

[iv] Wagner, Warren L., Herbst, Derral R., and Sohmer, S.H. Manual of the Flowering Plants of Hawai‘i: Revised Edition, Volumes 1 and 2. Honolulu: University of Hawai‘i Press; Bishop Museum Press, 1999.

[v] Burney, David A., James, Helen F., Burney, Lida Pigott, Olson, Storrs L., Kikuchi, William, Wagner, Warren L., Burney, Mara, McCloskey, Deirdre, Kikuchi, Delores, Grady, Frederick V., Gage II, Reginald, and Nishek, Robert. Fossil evidence for a diverse biota from Kaua‘i and its transformation since human arrival. Ecological Monographs, 71 (4), 2001, pp. 615-641.