Dictyostelid Cellular Slime Molds from Hawai'i1

Home , Dictyostelid, Dictyostelium, Polysphondylium pallidum

JOHN C. LANDOLT2 AND GEORGE J. WONG 3

ABSTRACT: Soil and litter samples, collected from Hawai'i on the islands of Hawai'i, O'ahu, and Kaua'i, were examined for occurrence and distribution of dictyostelid cellular slime molds. In total, 194 samples, from 20 different sites and representing several plant communities, were collected during June 1995 and processed in the laboratory soon thereafter. A total of 10 species and one variety was recovered, seven of which have not been reported previously from Hawai'i. The greatest species richness (seven) and highest densities (up to 63 clones per gram of fresh soil/litter) were found on the island of Hawai'i, with lower values obtained for sites on O'ahu and Kaua'i. It was rare for dietyo stelids to be recovered from more than 30% of the samples collected at any given site. A number of sites were characterized by recovery of a single species, and at least one site on each island sampled was devoid of recoverable dic tyostelids. Overall, dictyostelid densities were quite low compared with those at other locations in subtropical and temperate regions of the Northern Hemi sphere, and the values for species richness are lower than those reported for most neotropical mainland locations. These observations suggest a rather modest dictyostelid community in Hawai'i, at least during the relatively dry period when sampling was carried out. Lack of a windborne dispersal mecha nism may be responsible for the limited distribution of dictyostelids in Hawai'i and possibly other island groups that are remote from continental land masses.

DICTYOSTELID CELLULAR SLIME MOLDS are body or sorocarp. The sorocarp consists of rather ubiquitous components of the soil vacuolated cells, with cellulosic cell walls, litter interface, particularly in tropical, sub which form a branched or unbranched stipe, tropical, and temperate regions (Raper 1984). with a cluster ofspores at each stipe terminus. There are approximately 60 recognized spe Although there are a number of described cies composing three genera (Hagiwara 1989). species that seem to be rather cosmopolitan Most ofthe life cycle ofa dictyostelid is spent in distribution, several species ofdictyostelids in a unicellular, amoeboid state, with cells seem to be associated with narrower geo feeding upon bacteria, protists, and micro graphic or edaphic situations. In general, fungi. When such food supplies are abun species richness is greatest in the American dant, slime mold myxamoebae proliferate by Tropics, with 35 species recovered from just a mitotic cell division. As the local bacterial small area, near Tikal, in Guatemala (Vadell food supply becomes relatively depleted, hun et al. 1995). Species richness declines with dreds to thousands ofmyxamoebae, respond increasing latitude or elevation (Cavender ing to chemotactic signals, aggregate and col 1973). There are indications that species lectively differentiate as a stalked fruiting richness and composition may be correlated with aspects of ecological disturbance and patterns of community succession arising thereafter (Cavender et al. 1993). 1 Manuscript accepted 23 April 1997. There have been few dictyostelids reported 2 Department of Biology, Shepherd College, Shep herdstown, West Virginia 25443. in the literature from Hawai'i. In his 1975 3Department of Botany, University of Hawai'i at monograph on the Mycetozoa, Olive made Manoa, Honolulu, Hawai'i 96822. only passing reference to the occurrence of 98 Dictyostelid Cellular Slime Molds-LANDOLT AND WONG 99 dictyostelids in Hawai'i. Nelson et al. (1967) one might expect that such an area would described one species, Dictyostelium irregu harbor a diverse assemblage of dictyostelids faris, from an O'ahu collection, but it has not associated with the topological and vegeta since been reported from Hawai'i or else tional diversity and extensive human intro where. Several persons, during their tenure at duction of biota from elsewhere. However, the University of Hawai'i at Manoa, recall the geographically isolated nature of the geo the occasional isolation of dictyostelids (G. logically young Hawaiian island group might, E. Baker, pers. comm.; H. R. Hohl, pers. conversely, limit dictyostelid exploitation. comm.; R. D. Goos, pers. comm.), and there We report here the results ofa preliminary are specific citations for a few collections on survey to catalog the occurrence and dis file in the records of the Department of Bot tribution of dictyostelids from a variety of any at the University of Hawai'i at Manoa. vegetation associations on three of the larger However, these reports have not been re islands of Hawai'i. corded in the literature. Although relatively small in total area and rather distantly isolated from continental land masses, the islands of the Hawaiian ar MATERIALS AND METHODS chipelago support a diverse assemblage of Samples of soil and litter were collected plant communities resulting from a combi from several locations that represented a se nation of tropical location, serial volcanic lection of vegetation community types pres origin, and highly variable topography com ent on three of the larger Hawaiian islands, pared with land area (Armstrong 1973). In specifically the island ofHawai'i, which is the addition to remnants of endemic flora and largest in area and youngest in geologic his fauna, this island group has experienced the tory; O'ahu, which is the third largest (after introduction of many alien plants and ani Maui) and most densely populated by hu mals, first by Polynesian Hawaiians and mans; and Kaua'i, which is the fourth largest more recently as the result of European re in land area and is geologically the oldest discovery (Gagne and Cuddihy 1990). Thus, among the larger islands (Table 1).

TABLE I

PLANT CoMMUNITY ASSOCIATIONS IN HAWAI'I (AFTER GAGNE AND CuDDIHY [1990]) FROM WmeR SAMPLFS FOR ISOLATIONS OF DICTYOSTELIDS WERE COLLECTED

Coastal Mesic Forest, Hala (Pandanus): Kalalau Trail, Kaua'i (Q)a Coastal Wet Shrubland, Hau (Hibiscus): Kolekole Beach, Hawai'i (C) Lowland Mesic Shrubland, Guava (Psidium), Christmas Berry (Schinus), Eucalyptus: Kaua'i (P) Lowland Mesic Forest{Shrubland, Kukui (Aleurites), common ironwood (Casuarina): Waipi'o Valley, Hawai'i; Sacred Falls, O'ahu, (F; K) Lowland Mesic Forest, Koal'0hi'a (Acacia{Metrosideros): Manuka State Park, Hawai'i (G) Lowland Mesic Forest, Christmas Berry (Schinus): Pu'uomahuka, O'ahu (1) Lowland Mesic Forest, alien vegetation: Kealwa Heiau, O'ahu; Wa'ahila State Park, O'ahu (N; M) Lowland Wet Forest, 'Ohi'a{U1uhe (Metrosideros{Dicranopteris) fern: Maunawili Trail, O'ahu (0) Lowland Wet Forest, alien wet forest: Manoa Falls Trail, O'ahu (I) Montane Mesic Forest, 'Ohi'a (Metrosideros): Kalopa State Park, Hawai'i (D) Montane Mesic Forest, Koal'0hi'a (Acacia{Metrosideros{Sapindus): Krpuka Puaulu, Hawai'i; Hawai'i Volcanoes National Park, Hawai'i (A; H) Montane Mesic Forest, diverse: Koke'e State Park (Nu'alolo Trail, and Pihea Trail), Kaua'i (R, S) Montane Mesic Forest, alien vegetation: 'Akaka Falls State Park, Haw.ID'L(B) Montane Wet Mixed Community: Alaka'i Swamp Trail, Kaua'i (T) Montane Wet Forest, 'Ohi'a{Hapu'u (Metrosideros{Cibotium) tree fern forest: KIlauea lid Trail, Hawai'i Volcanoes National Park, Hawai'i (E) Agricultural mulch pile: Campus of the University of Hawai'i at Manoa, O'ahu (L)

•Letters refer to types of plant communities in Tables 2-4. 100 PACIFIC SCIENCE, Volume 52, January 1998

The soil/litter samples were processed in species was isolated from O'ahu (designated the laboratory within 24 hr of collection us as NAH 8) and Kaua'i (designated as KU 14). ing methods similar to those of Cavender and Several of the species isolated are widespread Raper (1965). Sterile, distilled water was and common, such as Dictyostelium bre mixed with 5.0-g samples of fresh soil/litter feldianum Hagiwara (= D. mucoroides Bre to create 1: 25 soil: water dilutions. A 0.5-ml feld sensu Norberg [in Hagiwara 1984]) and aliquot (0.02 g soil) of every diluted sample Polysphondylium pallidum Olive. It should be was added to the surface of each of two noted that there are currently two recognized culture dishes (95-mm diameter) containing a concepts of D. mucoroides. According to phosphate-buffered, hay infusion agar (fil Hagiwara (1984), the original concept of D. tered, sterile infusion of well-leached hay, mucoroides, which was published in 1865, 1.5 g/liter KH2P04, 0.62 g/liter Na2HP04 . was difficult to understand because the iso 7H20, 15.0 g/liter granulated agar) together lates identified as this species exhibited a wide with 3-4 drops ofa suspension of Escherichia range of morphological variation. It was not coli to serve as a food source. These culture until 1959 that Bonner suggested that D. dishes were maintained at 20-23°C, were ex mucoroides actually represented a complex amined daily with a dissecting microscope for of species, from which Norberg, in 1971, was 14 days, and the number and species of dic able to recognize six species and one variety tyostelid fruiting body clonal clusters that (in Hagiwara 1984). Among the species that appeared were recorded. When necessary, Norberg recognized in this complex were D. isolates were subcultured for further exami mucoroides and D. sphaerocephalum (Oud.) nation. Spores of representative dictyostelids Sacch & March. However, Hagiwara (1984) have been conserved and are available from believed that Brefeld's concept of D. muco I.C.L. roides was misinterpreted by Norberg and that the original description was based upon another species, which he formally described as D. brefeldianum, and that D. sphaero RESULTS AND DISCUSSION cephalum, a species originally described in In total, 11 different dictyostelids were 1885, was synonymous with Brefeld's origi isolated in this preliminary survey (Tables 2 nal concept of D. mucoroides. Because D. 4). This total includes nine fonnally de mucoroides was the earliest name to be scribed species and one variety, and one spe validly published, Hagiwara (1984) selected it cies that currently is undescribed. The latter as the correct name for this species. However,

TABLE 2

DICTYOSTELIDS RECOVERED FROM THE ISLAND OF HAWAI'I

PLANT COMMUNITIES"

SPEcms A B C DEF G H

Dictyostelium aureo-stipes X X D. gigantium X D. macroce,phalum X D. brefeldianum (= D. mucoroides sensu Norberg) X XX j)~7Jolycephalum------X ----x ------.. D. purpureum X Polysphondylium pallidum X X XX Total clones per g 48 63 4 43 8 48 3 0

aFor desCliptions

TABLE 3

DICTYOSTELIDS RECOVERED FROM THE ISLAND OF O'AHU

PLANT COMMUNITIESa

SPECIES OR VARIETY I J K L M N 0

D. breJeldianum (=D. mucoroides sensu Norberg) XX X D. mucoroides var. stoloniferum X D. polycephalum X Undescribed Dictyostelium (NAH 8) X P. pal/idum XXX P. violaceum X Total clones per g o 15 9 19 20 10 8

•For description of plant communities see Table I.

TABLE 4

DICTYOSTELIDS RECOVERED FROM THE ISLAND OF KAVA'I

PLANT COMMUNITIES"

SPECIES p Q R s T

D. breJeldianum (=D. mucoroides sensu Norberg) x D. purpureum X Undescribed Dictyostelium (KV 14) X D. mucoroides sensu Hagiwara (=D. sphaerocephalum) X Polysphondylium pallidum X X Total clones per g 5 7 5 3 73

•For description of plant communities see Table I.

Hagiwara's (1984) concepts have not been D. polycephalum has been recovered from the universally accepted (e.g., Cavender and Pacific islands of Guam and Moorea and one Lakhanpal 1986). Thus, we have included of the small outlying islands of the Bahamas both positions in our assignment of identity. (unpubl. data), and Hagiwara (1989) re- Some species isolated in this study of ported this species from Japan, Malaysia, Hawaiian dictyostelids (e.g., D. giganteum and the Philippines, which suggests a possible Singh, D. macrocephalum Hagiwara, Yeh & correlation to island habitats. No isolates Chien, and P. violaceum Brefeld) were re- considered to be D. irregularis as described covered from only a single site. One of the from Hawai'i by Nelson et a1. (1967) were more commonly isolated species in this recovered. study, and also one of the few that has been Within the island vegetation types sam previously reported from Hawai'i, is D. poly- pled, the greatest species richness and the cephalum Raper. This species, with its dis- greatest densities of recovered dictyostelids tinctive pseudoplasmodia and coremiform appear to be from Montane Mesic-Wet and "-sorocarps,has-'a-worldwide-distributiun~-bur-I::;owlana-"'Mesic communitieg;-paificulafly it is relatively uncommon compared with those present on the island of Hawai'i. many other species. However, it is fairly The overall degree of species richness in common in subtropical and tropical seasonal Hawai'i is actually relatively high for isolated forest (Cavender and Raper 1968). Recently, island situations. However, species richness 102 PACIFIC SCIENCE, Volume 52, January 1998

and densities ofdictyostelids on islands closer gation might add to the list of dictyostelid to the mainland, in tropical and subtropical species of Hawai'i, particularly if sampling zones, appear to be more comparable with included a wider range of vegetation types those of the mainland. Fourteen species were (e.g., subalpine and alpine zones and relict identified by Cavender (1970) from Trinidad "native" vegetation communities) and col and Tobago and from Lambuan, on the is lecting on other islands (e.g., Maui and land ofPanay, in the Philippines; nine species Moloka'i). All isolations in this study were were identified by Cavender (1976). Never done in June, so sampling at other times of theless, not all studies support this conclu the year may yield additional species at per sion. Dogma and Blancaver (1965) recovered haps higher densities. only four species from Luzon and Mindanao, and Cavender (1976) recovered six species from Luzon, both in the Philippines. It is, ACKNOWLEDGMENTS however, uncertain as to how meaningful the number of species are that were recovered by We thank Donald Hemmes, Mary Dogma and Blancaver (1965) because they Landolt, and Melinda Landolt for their as did not indicate the number of samples that sistance in the logistical support involved in were taken in their study. In the case of se making collections for this survey. Advice cluded islands, fewer species are generally re concerning the characterization of vegeta covered. Only five species of dictyostelids tion communities was provided by Puanani were isolated from New Zealand (unpubl. Anderson-Wong. We also thank the Division data), and only three species each were re of State Parks, Division of Forestry and covered from Guam and Moorea (unpubl. Wildlife, and the Natural Area Reserves data). System Commission of the State of Hawai'i It is interesting that Cavender (1976) re Department of Land and Natural Resources, ported finding that the same six species of together with the U.S. Department of Inte dictyostelids ranked in highest importance in rior National Biological Service (Hawai'i both tropical American and Asian forests. Volcanoes National Park), for assistance and Five of these six species (D. mucoroides, D. cooperation. purpureum, D. polycephalum, P. pal/idum, and P. violaceum) were recovered from Ha- waiian soils sampled in the study reported LITERATURE CITED here. The level of dictyostelid density in the Hawaiian soil and litter sampled is somewhat ARMSTRONG, R. W. 1973. Atlas of Hawaii. sparse when compared with that found in The University Press of Hawai'i, Hono- many mainland tropical, subtropical, and lulu. temperate locations in the Americas. The BONNER, J. T. 1959. The cellular slime molds. most obvious explanation for this low density Princeton University Press, Princeton, and modest species richness might be asso- New Jersey. ciated with the relatively isolated position of CAVENDER, J. C. 1970. Dictyostelium dimi- the Hawaiian archipelago together with the graformum, Dictyostelium laterosorum and fact that dictyostelid spores and other prop- Acytostelium el/ipticum: New Acrasieae agules are not especially adapted for wind- from the American Tropics. J. Gen. borne dispersal (Cavender 1973). The ex- Microbiol. 62: 113-123. treme isolation ofHawai'i from the mainland ---. 1973. Geographical distribution of also makes it difficult for propagules of dic- Acrasieae. Mycologia 65: 1044-1054. - fyoste-ltdst

sliine molds in forest soils of India. My 1989. The taxonomic study of cologia 78: 56-65. Japanese dictyostelid cellular sliine molds. CAVENDER, J. C., and K. B. RAPER. 1965. National Science Museum, Tokyo. The Acrasieae in nature. I. Isolation. Am. NELSON, N., L. S. OLIVE, and C. STOIANO J. Bot. 52: 294-296. VITCH. 1967. A new species of Dictyoste ---. 1968. The occurrence and distribu lium from Hawaii. Am. J. Bot. 54:354 tion of Acrasieae in forests of subtropical 358. and tropical America. Am. J. Bot. OLIVE, L. S. 1975. The mycetozoans. Aca 55: 504-513. demic Press, New York. CAVENDER, J. C., R. BRADSHAW, J. P. RAPER, K. B. 1984. The dictyostelids. REGNER, and T. DAMIo. 1993. Response of Princeton University Press, Princeton, soil dictyostelid slime molds to agricul New Jersey. tural disturbance in a tropical environ STEPHENSON, S. L., and J. C. LANDOLT. 1992. ment. Biotropica 25: 245-248. Vertebrates as vectors of cellular slime DOGMA, I. J., JR., and R. C. BLANCAVER. moulds in temperate forests. Mycol. Res. 1965. Cellular sliine molds from Philip 96: 670-672. pine soil. Philipp. Phytopathol. 1:41-52. SUTHERS, H. B. 1985. Ground-feeding GAGNE, W. C., and L. W. CUDDIHY. 1990. migratory songbirds as cellular slime mold Vegetation. Pages 45-114 in W. L. distribution vectors. Oecologia (Berl.) 65: Wagner, D. R. Herbst, and S. H. Sohmer, 526-530. Manual of the flowering plants of Ha VADELL, E. M., M. T. HOLMES, and J. C. wai'i, Vol. 1. University of Hawai'i Press CAVENDER. 1995. Dictyostelium citrinum, and Bishop Museum Press, Honolulu. D. medusoides, and D. granulophorum: HAGIWARA, H. 1984. Review of Dictyoste Three new members of the Dictyostelia lium mucoroides Brefeld and D. sphaero ceae from forest soils ofTikal, Guatemala. cephalum (Oud.) Sacc et March. Bull. Mycologia 87: 551-559. Natl. Sci. Mus. Ser. B Bot. 10:27-41.