Hawaii, an archipelago in the Pacific Ocean, harbors a remarkable collection of plant and animal life. Its native species contribute to the islands’ biodiversity.
Understanding “Native” in Hawaii
To appreciate Hawaii’s biodiversity, understanding specific terms for its species is important. A “native” species arrived and established a population without human assistance. This natural colonization occurred via wind, ocean currents, or birds.
A significant subset of native species are “endemic,” found exclusively in Hawaii. Over 90% of Hawaii’s native land-dwelling species are endemic, highlighting their unique evolutionary journeys. “Introduced” or “alien” species are those brought by human activity.
Hawaii’s Endemic Plant Life
Hawaii’s plant life includes many endemic species with unique adaptations. The ‘ōhi’a lehua (Metrosideros polymorpha) is the most common native tree, comprising about 80% of Hawaii’s native forests. This versatile tree, which can grow from a creeping shrub to a tall tree, is a pioneer species that often colonizes recent lava flows. Its showy flowers, typically red but also found in other colors, are a significant nectar source for native birds.
Another example is the silversword (Argyroxiphium sandwicense), known for its distinctive globe-shaped rosette and dense covering of silver hairs. This plant thrives in the arid, high-altitude volcanic slopes of Maui and Hawaii Island. The silvery hairs reflect sunlight and help insulate the plant against extreme temperatures, while its succulent leaves store water. After many years, the silversword sends up a tall flowering stalk, sometimes reaching almost 3 meters, covered in hundreds of small blossoms, after which the entire plant dies.
Hawaii’s Endemic Animal Life
Hawaii’s animal inhabitants present unique examples of evolution. The Hawaiian honeycreepers, a diverse group of small, brightly colored finch-like birds, are endemic to the islands. These birds demonstrate adaptive radiation, evolving a wide array of beak shapes suited for different diets. Their plumage can vary from dull olive-green to vibrant yellow, crimson, and multi-colored patterns.
The nene (Branta sandvicensis), or Hawaiian goose, is Hawaii’s official state bird and the only goose species endemic to the Hawaiian archipelago. Unlike most geese, the nene has reduced webbing between its toes and longer, stronger legs, adaptations for walking across volcanic lava flows. Its plumage is typically dark brown or sepia, with cream-colored cheeks and a buff neck streaked with black.
The Hawaiian monk seal (Neomonachus schauinslandi) is one of two remaining monk seal species and is found exclusively in Hawaiian waters. These seals have a distinctive wide muzzle, large eyes, and fur that ranges from brown to light gray. They spend most of their lives at sea, foraging on the ocean floor for fish, cephalopods, and crustaceans, but come ashore to rest and give birth on sandy beaches.
Hawaii’s only native terrestrial mammal is the Hawaiian hoary bat (Lasiurus semotus), locally known as ʻōpeʻapeʻa. This bat is characterized by its brown to reddish fur, often tipped with white, giving it a frosty appearance. Weighing between 14 and 18 grams with a wingspan of 10.5 to 13.5 inches, these nocturnal insectivores use echolocation to hunt moths, beetles, and other night-flying insects. They roost solitarily in trees, from sea level to the highest volcanic peaks.
The happy face spider (Theridion grallator) is a small arachnid endemic to the Hawaiian Islands, particularly found on Oahu, Molokai, Maui, and Hawaii. It is named for the unique patterns on its abdomen that often resemble a smiling face. These spiders are typically less than 5 millimeters long and have long, thin legs, living on the undersides of leaves in wet forests.
The Evolutionary Tale of Hawaiian Species
Hawaii’s isolation in the Pacific Ocean created a natural laboratory for evolution. Situated approximately 3,680 kilometers from the nearest continental shore, the islands experienced infrequent colonization events by species arriving naturally via wind, waves, or wings. This isolation meant that once a colonizing species arrived, its gene pool was limited, leading to a “founder effect” where the new population’s genetic makeup differed from its ancestral population.
Over millions of years, these initial colonizers diversified into numerous unique forms, a process known as adaptive radiation. As species adapted to Hawaii’s varied microclimates and ecological niches, they evolved distinct physical traits and behaviors. For instance, a single ancestral finch species gave rise to over 50 types of Hawaiian honeycreepers, each with specialized beaks for different food sources. This evolutionary process underscores the scientific significance of Hawaii’s unique biodiversity.