Below are some of the amazing examples covered on this page:
- Hawaiian Honeycreepers
- Carnivorous Caterpillars
- Pomace Flies (Drosophilids)
- Lobelias and Silverswords
- High Elevation Cloud Forests
- Tree Snails
- Fish that Climb Waterfalls
Several Wikipedia pages for this group of birds provides a wealth of information some of which is included below.
Hawaiian honeycreepers are small, passerine birds endemic to Hawaiʻi. They are closely related to the rosefinches in the genus Carpodacus. Their great morphological diversity is the result of adaptive radiation in an insular environment.
The wide range of bill shapes in this group, from thick, finch-like bills to slender, down-curved bills for probing flowers have arisen through adaptive radiation, where an ancestral finch has evolved to fill a large number of ecological niches. This is shown in the illustration below. The beak shapes indicate the feeding strategies: generalists, insectivores (gleaners), insectivores (bark pickers), nectarivores, or frugivores/seed eaters. Some are intermediary.
Illustrated is a juvenile Laysan finch (center), and clockwise from the top: Hawaiʻi akepa, Maui parrotbill, poouli, iiwi, Maui alauahio, and akiapolaau.
A further illustration of the evolution of feeding strategies and associated beak shapes is through an enhanced poster by Douglas Pratt and found here: https://www.hoikecurriculum.org/wp-content/uploads/2012/07/AdRad-labels_eml-permission-Douglas-Pratt-and-Yale-U-Press.jpg.
Before the introduction of molecular phylogenetic techniques, the relationship of the Hawaiian honeycreepers to other bird species was controversial. The honeycreepers were sometimes categorized as a family Drepanididae, other authorities considered them a subfamily, Drepanidinae, of Fringillidae, the finch family. The entire group was also called “Drepanidini” in treatments where buntings and American sparrows (Emberizidae) are included in the finch family; this term is preferred for just one subgroup of the birds today. Most recently, the entire group has been subsumed into the finch subfamily Carduelinae.
Species lists and description by form are here: https://en.wikipedia.org/wiki/List_of_adaptive_radiated_Hawaiian_honeycreepers_by_form. Those species still surviving are here: https://en.wikipedia.org/wiki/List_of_adaptive_radiated_Hawaiian_honeycreepers_by_form#Surviving_forms_in_list.
Below is one of my favorite birds, the akohekohe [a nectar sipper and insectivore].
And here is an early painting of the species.
Below is a photograph of one of the unique woodpecker-like probing species.
The Iiwi, a nectar feeder, is one of the most iconic birds of Hawaiʻi.
The Hawaiʻi Creeper, an insectivore, is found only on the island of Hawaiʻi. Shown here is an adult and juvenile.
An interesting and informative 2017 video by DLNR on the forest birds is here: https://vimeo.com/199157463
A good video focusing primarily on the honeycreepers featuring photographer Jack Jeffrey and Hakalau NWR is here: https://www.youtube.com/watch?v=LI0hgUePEIQ. A short video showing an Iiwi feeding on nectar of a Hawaiian lobelia is here: https://www.youtube.com/watch?v=nZyuqS-Kb7k.
A very good, short video showing some of the honeycreepers that are in their habitat at Hakalau NWR is here: https://www.youtube.com/watch?v=rKgQ6qdTgKM.
Steve Montgomery described in a 1983 paper a new type of behavior in a Hawaiian moth larvae (caterpillar): Carnivorous caterpillars: the behavior, biogeography and conservation of Eupithecia (Lepidoptera: Geometridae) in the Hawaiian Islands. GeoJournal 7 (6): 549–556. doi:10.1007/BF00218529).
Some species in this genus (at least six identified in the study) in Hawaiʻi position themselves inconspicuously along leaf edges and stems to seize insects that touch their posterior body section. They the front of the body backwards in a very rapid strike. The genus Eupithecia is a worldwide group of many species that until this study were only known to feed on plant matter. The author speculated that barriers to dispersal continental insect predators into Hawaiʻi resulted in an environment favoring behavioral and consequent morphological adaptations and suggested the common general name for them as “grappling inchworms”.
Very high-quality photos of all stages of this behavior are at: http://Hawaiianforest.com/wp/Hawaiian-carnivorous-caterpillar-eupithecia/.
A short video of the behavior from PBS is here: https://www.youtube.com/watch?v=zAiMzeOfOgA.
Another unusual habit is predation of snails. This habit is described by Rubinoff and Haines in a Science magazine paper in 2005 titled ‘Web-Spinning Caterpillar Stalks Snails, 2005: https://science.sciencemag.org/content/309/5734/575/tab-article-info. The species is Hyposmocoma molluscivora. The full article is available here: https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.859.7468&rep=rep1&type=pdf.
A video showing the capture is here: https://www.youtube.com/watch?v=cIarjWaXC4Y.
Pomace Flies (Drosophilids)
It is estimated that 800 or more native Drosophilid species are in Hawaiʻi and the evidence indicates that they all evolved from a colonization by a single species! It is one of the most spectacular examples of evolutionary radiation known in Hawaiʻi and anywhere. About a quarter of the world’s known species of about 4,000 species in Drosophilidae are endemic to Hawaiʻi. A summary of the Drosophilid story and the extraordinary radiation of this group in Hawaiʻi is available here: https://www.nap.edu/read/10865/chapter/7#15.
A recent explanation and analysis of the evolution of the group is provided in a paper titled ‘Hawaiian Drosophila as an Evolutionary Model Clade: Days of Future Past’ by O’Grady and DeSalle is here: https://www.drosophilaevolution.com/uploads/6/6/8/3/6683664/o_27grady_et_al-2017-bioessays.pdf. In it they provide evidence that all the species in Hawaiʻi are descended from a single ancestral species that made it to Hawaiʻi ‘roughly 25 million years ago. However, they do note some complications in the taxonomy that need to be addressed.
The 2015 DLNR SWAP for Pomace flies notes “Drosophila have specialized in two major ways, with species groups showing preference for a specific plant part (e.g., leaves, fruit, flowers, stems, bark, sap flux) of that host plant, and individual species being specific to a given native plant family. This subdivision of available resources is one potential explanation for the large numbers of Hawaiian Drosophila species.”
Some details of a subgroup known as the picture-wing drosophilids by K. Magnacca is here: https://www.fws.gov/endangered/about/ep_45_2015.html. Within that group are 120 species that include some of the largest and most colorful Drosophila in the world. He explains some of the life history of picture-wing flies. They ‘breed in dead or dying native trees, where the larvae burrow into the rotting mushy bark and feed on bacteria and yeasts. Though often overlooked, saprophages (consumers of decaying material) like these play an important role in maintaining the balance of microbes and ultimately converting of dead plant matter into organic soil.’ Their use of only one or two species of host plants, with many of them under threat, makes them vulnerable to impact and many species are already extinct.
Check it out: The BBC documentary Planet Earth in its “South Pacific” episode had amazing footage of a picture-wing fly mating ritual.
Lobelias and Silverswords
The spectacular bellflower plant family (Campanulaceae) in Hawaiʻi is a spectacular example of evolutionary radiation. Based on the evidence of T. Givnish et al. in a study published in 2008 (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2664350/pdf/rspb20081204.pdf) the lobelias originated from a single colonization event about 13 Mya. This would have been when some of the current atolls in the Hawaiian chain were high islands and way before the current main islands existed. The group now numbers over 125 species in six genera.
The six genera can be broadly separated based on growth habit, as described in https://en.wikipedia.org/wiki/Hawaiian_lobelioids (accessed 100619): Clermontia are typically branched shrubs or small trees, up to 7 metres (23 ft) tall, with fleshy fruits; Cyanea and Delissea are typically unbranched or branching only at the base, with a cluster of relatively broad leaves at the apex and fleshy fruits; Lobelia and Trematolobelia have long thin leaves down a single, non-woody stem and capsular fruits with wind-dispersed seeds; and the peculiar Brighamia have a short, thick stem with a dense cluster of broad leaves, elongate white flowers, and capsular fruits.
The Imada 2012 Hawaiian vascular plant checklist lists 159 species and subspecies of lobelioids in Hawaiʻi (all endemic). The total number of lobeliod species listed if subspecies are disregarded is 139 (17 species have subspecies, mostly 2 but several with 3).
A good website for information on this group and photos of the species is Gerald Carr’s website: http://www.botany.hawaii.edu/faculty/carr/silversword.htm.
The silversword alliance in Hawaiʻi has species with extremely diverse growth forms as shown in the collage below taken from http://darwin.uky.edu/~sargent/EvolutionFAQ/silverswords.pdf.
The webpage at Darwin.uky.edu given above is part of a document with a summary of the evolution of the silversword alliance. Other aspects of the adaptive radiation and hybridization in the group are here: http://www.botany.hawaii.edu/faculty/carr/radiation.htm.
The book Tarweeds and Silverswords, Evolution of the Madiinae (Asteraceae) by S. Carlquist, et al. (editors) is not downloadable for free but the following website includes links to many aspects of silversword biology: at http://www.botany.hawaii.edu/faculty/carr/tarweeds2.htm. Some further details of the silversword story are available here: https://en.wikipedia.org/wiki/Silversword_alliance.
High Elevation Cloud Forests and Bogs
Hawaiʻi’s cloud forests are bogs are magical places that are a world apart from the lowlands of communities and beaches. Most of them still have their flora largely intact. The Nature Conservancy Ecoregional Plan website describes a Montane Wet System that includes these types of habitats and in which are designated several natural communities. They describe this system )http://www.hawaiiecoregionplan.info/MWsystem.html) as between 1,000 and 2,000 m (ca 3,000 – 6,000 ft) elevation, receiving greater than 75 inches annual precipitation, or otherwise bearing prevailingly wet substrate conditions. It includes forests, bogs, and wet shrublands on the windward and summit regions. A short description of Hawaiian bogs can also be found on this page: https://en.wikipedia.org/wiki/Hawaiian_tropical_rainforests.
One fine example is Mount Kaala which is a Natural Area Reserve (NAR) site: https://dlnr.hawaii.gov/ecosystems/nars/oahu/kaala/. For further information about NAR System go to this page [link]. Mount Kaala is the highest peak on the island of O‘ahu at 4,025 ft and it is recognizable by its flat-top profile. The area is swept by clouds and the flat area has some characteristics of a bog. The reserve includes much more than the flat top comprising 1,100 acres of rugged mountain terrain with deep gulches and ridges. The website link above has much information including maps, a management plan, a list of the natural communities and descriptions and photos of flora and fauna. A Mount Kaala plant guide is here: https://dlnr.hawaii.gov/ecosystems/files/2013/08/Kaala-Bog-Plant-Guide.pdf.
The West Maui Natural Area Reserve has https://dlnr.hawaii.gov/ecosystems/nars/maui/west-maui-2/.
Bog photos of Betsy Gagne are here: https://hear.smugmug.com/Photographers/BHG/Hawaii-bogs/.
Other websites with information on bogs are:
A study of Vegetation of an Alpine Bog on East Maui, Hawaiʻi, by Vogl and Henrickson (1971) is here: https://scholarspace.manoa.hawaii.edu/bitstream/10125/4246/1/vol25n4-475-483.pdf.
Tree snails in the genus Achatinella are found only on the island of Oahu and are described in wikipedia (https://en.wikipedia.org/wiki/O’ahu_tree_snail) as ‘a large genus of colorful, tropical, tree-living, air-breathing, land snails, arboreal pulmonate gastropod mollusks in the family Achatinellidae [https://en.wikipedia.org/wiki/Achatinellidae]. This genus of tree snails live in Hawaiʻi, and all are endangered species. They were once abundant. They were mentioned in Hawaiian folklore and songs, and their shells were used in lei and other ornaments.’ A wikipedia page with a list and links to pages for 37 of the species in this genus is here: https://en.wikipedia.org/wiki/Category:Achatinella.
The endangered species listing of these species in Hawaiʻi is unique since the entire genus is designated as endangered. At least 41 species were thought to be present in Hawaiʻi but over 20 are now extinct and the remainder are critically imperiled.
A brief overview of the genus and a series of excellent photos are available here: https://usfwspacific.tumblr.com/post/177004835620/species-spotlight-oahu-tree-snails-the-voice.
An interesting story about conservation of the group is here: http://www.honolulumagazine.com/Honolulu-Magazine/April-2012/Endangered-Kahuli-Snails-on-Oahu/.
An even more diverse and endangered snail fauna in Hawaiʻi are other groups of terrestrial snails. See the description of this group on the page under the Fauna category.
Fish that climb waterfalls
Hawaiʻi has a group of fish (gobies) that are amphidromous. The gobies lay their eggs in the stream, and upon hatching, the larvae move with the current downstream to the ocean. After living in the ocean plankton community the larvae migrate upstream to mature. Hawaiian streams typically have waterfalls of varying sizes along their course. Several of the goby species are able to climb these waterfalls.
As described at http://hbs.bishopmuseum.org/waipio/Critter%20pages/lentipes.html the fish ‘O‘opu ‘alamo‘o [Lentipes concolor] is “perhaps the most remarkable fish found in the Hawaiian Islands due to its world-record climbing abilities, and this species has been documented to climb Hi‘ilawe Falls in Waipio Valley. With a vertical drop of nearly 1000 ft (300 m), Hi‘ilawe Falls is the highest free-fall waterfall in Hawai‘i and also one of the highest in the world. It is remarkable that ‘o‘opu alamo’o can ascend a single waterfall of this height, a feat matched nowhere else in the world.” These fish are able to climb with the help of fins modified into a suckerlike disc.
A description of adaptations of Hawaiian Freshwater Gobies to Stream Life is here: https://dlnr.hawaii.gov/dar/habitat/about-streams/adaptation/. The amphidromus life cycle of Hawaiian stream gobies is shown in this diagram.
The recent PBS television series Islands of Wonder included one episode on Hawaiʻi which showed oopu migrating up a waterfall with closeups showing how they do it.