AGARICALES OF THE HAWAIIAN ISLANDS
DENNIS E. DESJARDIN
San Francisco State University
DON E. HEMMES
University of Hawai`i, Hilo
GEORGE J. WONG
University of Hawai`i, Manoa
This project, funded by the National Science Foundation (DEB-9300874) through the Biotic Surveys and Inventories Program of the Division of Environmental Biology, is designed to document the diversity, distribution and ecology of Agaricales (Basidiomycota) in the Hawaiian Islands. The Order Agaricales includes all holobasidiomycetes with fleshy and typically putrescent sporocarps forming a lamellate or smooth hymenophore (agarics) or poroid hymenophore (boletes).
The Hawaiian Archipelago is the largest and most isolated oceanic island group in the world. Located between 18š and 30š North latitude in the central Pacific Ocean, the Islands are more than 4000 km from the nearest continent and about 3200 km from the nearest high-island group. The Archipelago, spanning approximately 2400 km, is composed of eight main islands in the southeastern region (Ni`ihau, Kaua`i, O`ahu, Moloka`i, Lana`i, Kaho`olawe, Maui, and Hawai`i) and the Northwestern Hawaiian Islands (Nihoa to Kure Atoll). Our project is designed to survey the diversity of Agaricales on six of the eight main islands (excluding Ni`ihau and Kaho`olawe).
The Hawaiian Islands are volcanic in origin, with the oldest of the high islands, Kaua`i, being about 5.1 million years in age, and the youngest and still volcanically active Hawai`i being about 0.5 million years. Because of their isolated nature and relatively recent volcanic origin, the Hawaiian Islands are excellent natural laboratories of considerable interest to scientists investigating biodiversity, biogeography, species dispersal mechanisms, and evolutionary processes. There has evolved a spectacular array of species and unique ecosystems, with a level of endemism in its biota that is higher than that in any other region of the world. For this reason, the Hawaiian Islands are considered the world's premier showcase for examples of adaptive radiation. Concerted interest in the biology of the Hawaiian Islands began with the pioneering studies of Sherwin Carlquist (1965, 1970, 1974), and numerous studies on the biota of the Hawaiian Islands have since followed.
In recent articles on the conservation of Hawaiian natural systems, Gagné (Bioscience 38:264-271. 1988) and Loope et al. (ibid. 38: 272-282. 1988) enumerated our current knowledge of Hawaii's biodiversity. Data on the number of native species, the minimum number of original colonists, and percent endemism were provided for marine algae, ferns and fern allies, mosses, Gymnosperms (0), flowering plants, marine decapods, terrestrial and marine molluscs, terrestrial arthropods, reptiles and amphibians (0), mammals, birds and fishes. They reported that levels of endemism range from lows of approximately 13% in macroscopic marine algae and 29% in fishes, to as high as 91-97% in flowering plants (of 970 native spp.), 99% in terrestrial molluscs (of ca. 1000 native spp.), and 99% in terrestrial arthropods (of ca. 6000 native spp.). Glaringly obvious in these lists and throughout other review papers on Hawaii's biota, is the omission of data on an entire kingdom of organisms, viz., Kingdom Fungi. A survey of relevant literature revealed that data on fungi of the Hawaiian Islands is limited, and supports our contention that the Islands are one of the more mycologically underexplored regions of the world.
Prior to beginning this project, less than 100 species of agarics and boletes had been reported from the Islands. During the first 30 months of the project we have conducted fieldwork of two types: 1) One or two major expeditions per year were conducted, each approximately 3 weeks in duration, focussing on 3 to 4 islands, plus several weekend collecting trips to Kaua`i, Moloka`i, Lana`i and Maui were conducted each year dictated by adequate rainfall patterns; and 2) intensive collecting along permanent transects every two weeks throughout the year at two different native Montane O`hia-Hapu`u Forests on the Island of Hawai`i. During the expedition type of fieldwork, we have sampled all types of vegetation in the Hawaiian Islands that support fleshy fungi. The transect fieldwork was initiated one year before NSF funding began and has continued uninterrupted. We now have four years of data on the frequency of occurrence and the environmental factors that influence sporulation for native Hawaiian mushrooms. To date, our fieldwork has yielded over 2000 specimens of agarics and boletes, each accompanied by notes on fresh macromorphology, plant associates and community type, substrata-type, and location data (often including lat./long. coordinates). In addition, we have made illustrations or taken photographs of each taxon. Preliminary determinations indicate that at least 255 species of agarics and boletes occur in the Hawaiian Islands (see tables below). Of the originally reported 100 species, 65% were misdetermined as a result of using north temperate North American and European mushroom epithets for tropical taxa.
Although our taxonomic analyses are still ongoing and hence, inconclusive, our research has uncovered several significant findings. First, extensive research in pristine native forest regions indicates that there are only about 30 native Hawaiian species of mushrooms. Of these, 25 represent new species and are considered by us as putative endemic taxa, while the remaining 5 native species are indigenous. We expect this total will reach only about 50 native species when all of our material is processed and determined. Second, the remaining 225 taxa (88%) so far known from the Hawaiian Islands represent alien species introduced either directly or indirectly through human activities over the past 1500 years. These alien species have been introduced from all over the world, presumably as passengers on plants and animals. It is possible that some of these taxa arrived independent of human intervention via aerially dispersed propagules, however of the taxa collected to date, few have basidiospores optimally designed for long distance aerial dispersal and establishment. We suspect that aerially dispersed fungal propagules played an insignificant role in the establishment of mushroom species in the Hawaiian Islands.
As our project progresses, we will continually update the tables included as well as add new tables itemizing the species encountered. In addition, many more photographs of interesting taxa will be added to the page.
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