sign in sign up
<<
Home , Amaranthus brownii, Cenchrus echinatus, Chenopodium oahuense, Eragrostis variabilis, Euphorbia celastroides, Hawaii (island)

Pacific Science (1985), vol. 39, no. 2 © 1985 by the Uni versity of Press. All rights reserved

Recent Observations on the of Island, Northwestern !

SHEILACONANT2

ABSTRACT: Terrestrial plants on Nihoa Island were censused, mapped, and collected during four expeditions to the island between May 1980 and May 1983. Distribution, abundance, and phenology of the vascular plants are reported, including maps and population estimates for the rarer species. With the possible exception of the exceedingly rare , the island's endemic plants are present in small but stable populations. A total of 7 months of field work , including the first extended winter expedition to the island, permitted exhaustive searches for rare species and opportunities to estimate populations of winter annuals. Apparently, only one alien , oleracea, is abundant on the island. A second alien species, Nephrolepis multiflora , probably reached the island naturally via wind or bird dispersal and occurs in very limited numbers .

NIHOA IS THE SOUTHERNMOST of those islands dinae: Telespyza ultima). In addition, there referred to as the Northwestern Hawaiian are 17 species ofbreeding and a num­ Island s (NWHI) or leeward Hawaiian Is­ ber ofmigratory shore birds and accidental or lands . It is about 250 statute miles northwest vagrant bird species (Conant 1983). A small of and about 155 statute miles population of the endangered Hawaiian southeast ofNecker Island. Nihoa is about 63 monk seal (Monachus schauinslandi) is resi­ ha in area, rising to 273 m at its highest point dent, and individuals of the threatened green (Miller Peak) , with an average southward fac­ sea turtle (Chelonia mydas) may be seen forag­ ing slope of 45° (Palmer 1927). There is one ing on marine algae near the rocky shorelines . nearly inaccessible beach on the south shore, There are also over 35 endemic arthropods, most of which consists oflow (10-20 m) cliffs, including a number of newly discovered, un­ while the east, north, and west coasts are sheer described species (Conant et al. 1983). cliffs, sometimes as high as 250 m. The island Nihoa has the most diverse biota, and prob­ is part ofthe Hawaiian Islands Na tional Wild­ ably the most intact biota, of any ofthe islands life Refuge (HINWR), which includes all of in the northwestern group (Conant et al. the NWHI except Midway and Kure . This 1983). It may also be one of the only places refuge is managed by the U.S. Fish and Wild­ remaining in the entire Hawaiian archipelago life Service (FWS). where there is a diverse and relatively intact Nihoa has two endemic species of birds , low-elevation dry-land ecosystem, with its both ofwhich are considered endangered: the complement of native terrestrial plants, arth­ Nihoa millerbird (Muscicapidae: Acrocepha­ ropods, and birds. Emory (1928) conjectured Ius familiaris) and the (Drepani- that 170 to 200 people occupied Nihoa for an undetermined period of time. He also noted tha t the character of the archaeological sites

1 This research was supported by the University of suggested that the main occupation took place Hawaii Office of Research Administration and Sea Grant early in the Hawaiian sequence, rather than Program, the National Marine Fisheries Service, the U.S. during the last several hundred years before Fish and Wildlife Service, and the U.S. Forest Service. contact. The fact that there was a period of Manu script accepted 13 August 1984. human occupation could mean that enough 2 University of Hawaii at Man oa, Department of General Science, 2450 Campus Road , Honolulu, Hawaii disturbance took place to have caused some 96822. of native organisms (Olson and 135 136 PACIFIC SCIENCE, Volume 39, April 1985

F IGURE I. View of Nihoa Island from the summit of Dog's Head.

James 1982). Nevertheless, Nihoa remains first three expeditions, I made systematic col­ biotically the "gem " of the northwestern lections of all species present on the fourth, islands of the Hawaiian archipelago. depositing all specimens in the Herbarium Of the 26 species that have Pacificum of the Bernice P. been recorded from the island (Christopher­ (BISH). During the third and fourth expe­ sen and Caum 1931,Conant and Herbst 1983, ditions, some seeds and live plant materials Herbst 1977), 5 are alien, 17 are indigenous, were collected and subsequently deposited at and 4 are endemic to the island. The objective the Waimea Arboretum. of this paper is to update information on the The dates of my four expeditions and the status arid distribution of the vascular plants names ofmy co-workers on these expeditions of Nihoa, providing distribution maps and are as follows: 31 May to 6 July 1980(Mark S. population estimates for the rarer species. Collins), 31 January to 22 February 1981 Herbst's (1977) discussion ofthe vegetation of (Mark J. Rauzon), 18 May to 23 August 1981 Nihoa provides the starting point from which (Audrey L. Newman through 19 July and I began assembling new information. I also David P. McCauley thereafter), and 19 April have included some notes on my collections to 3 May 1983 (Wayne C. Gagne). and brief observations of lichens and algae. In the summer of 1981, I estimated the per­ Figure I is a photograph of the island, show­ cent cover ofthe various plant species in each ing the terrain and major topographic of74 sample plots (76 x 76m). In 1980,Mark features. Collins of the U.S. Forest Service and I had marked off all the accessible parts of the island into plots that were approximately the same size (250 x 250 ft) and location as those sam­ METHOD S pled by FWS biologist John Sincock (unpub­ The majority ofthe information reported in lished data), who also estimated the percent this paper is based on observations made dur­ cover of the species in these plots in May of ing reconnaissance of vegetation or during the 1969. My objective was to determine the rela­ course ofmy studies of birds and invertebrates tive abundance of the various plant species on four different expeditions to the island . present. Values for total cover of the various Although I collected a few plants during the species are reported in Table 4. Plants of Nihoa Island-CoNANT 137

TABLE I Kaua'i (Table 1). For the most part, rainfall RAINFALLD ATAFROM FR ENCH FRIGATE SHOALS amounts from and () AND M ANA, KAVA' I, FORTHE P ERIODS Mana correspond, but there are a few months P RECEDING EXPEDITI ONS D ESCRIB ED INTHIS PAPER where data are markedly different (e.g., Octo­ ber 1982). Rainfall was greatest in the months RAINFALL (in.) of December, January, and February in 1979-1980 and 1980-1981, but heavy rainfall F RENCH F RIGATE MONTH AND YEAR SHOALS M ANA occurred earlier (i.e., October, November, December) in 1982-1983. Other patterns of D ecember 1979 na 1.52 rainfall do not clearly emerge from the data in January 1980 na 4.60 Table 1, though they may exist. February 1980 na 1.70 M arch 1980 na 0.42 Table 2 summarizes my notes on the phe­ April 1980 na 0.36 nology of the various plant species on Nihoa. M ay 1980 na 6.63 It appears that most Nihoa plant species June 1980 na 1.38 during the spring months. Fewer August 1980 1.46 0.64 species were observed flowering in winter and September 1980 3.84 0.29 summer months. Most species had mature October 1980 na 0.27 at some point during the spring and November 1980 na 0.38 December 1980 5.18 5.27 summer, fewer in the winter observation January 1981 2.67 1.45 period . Observations indicate that flowering February 1981 3.56 2.53 and production follow an initial period March* 1981 0.36 0.29 of growth ( and early .develop­ April* 1981 0.83 1.01 ment for the annual plants) that may be stimu­ M ay* 1981 0.39 0.26 June* 1981 1.18 1.16 lated by rainfall in the winter months. July* 1981 0.92 0.91 A visit to Nihoa during the September­ August* 1981 1.64 1.39 November period would be helpful in assessing September 1982 2.56 0.30 which plants have distinctive phenological October 1982 4.69 14.14 fluctuations. The present data indicate that November 1982 6.17 5.51 only a few of the species show distinctive pat­ December 1982 1.86 5.22 terns. These are the annuals Panicum torridum, January 1983 0.61 0.35 February 1983 0.49 0.15 Amaranthus brownii, and Sicyos nihoaensis; M arch 1983 0.56 1.33 and at least one perennial, varia­ April 1983 0.85 0.07 bilis. More complete observations are needed, May 1983 1.19 '. as there were some species (e.g.,

NOTE : na = data not available. celastroides, , ) for • Rainfall data for these periods were actually recorded from which I did not make specific searches for . mid-month to mid-month, such that the data for March were fruits or seeds. Additional comments on phe­ recorded from 15 March to 15April , for April from 15April to 15 May, and so on. nology are given in the species accounts.

PHENOLOGY During the several expeditions I kept anec­ SPECIES ACCOUNTS dotal notes on phenology of the various plant In the following account, plant families are species. Because plant phenology on Nihoa is listed in phylogenetic order and genera in al­ probably influenced by the temporal distri­ phabetical order within families. Botanical bution and amount of rainfall, I acquired nomenclature ofthe flowering plants is based rainfall data from the FWS field station on primarily on St. John (1973). I summarized Tern Island, French Frigate Shoals, about the available historical data on collections and 300mi northwest of Nihoa Island, and from sightings of the vascular plants in Table 3 to the National Weather Service station at provide an overview of the history and present Mana, on the northwestern, leeward coast of status of the taxa . 138 PACIFIC SCIENCE, Volume 39, April 1985

TABLE 2

S UMMARY OF P HENOLOGICAL D ATA ON N IHOA PLANTS DURI NG FOUR V ISITS FROM M AY 1980 TO M AY 1983

M Ay -JULY J ANUARY- F EBRUARY M Ay -AUGUST A PRIL-MAY PLANT SPECIES 1980 1981 1981 1983

Nephrolepis multiflora v echinatus mf,d v, fl, yf, mf v, fl v, fl, yf, mf, sd v, b, fl, yf, mf Panicum torridum d v, b, fl, yf d v,mf Pritch ardia remota v, b, fl, yf v v, b, fl, yf, mf v, b, fl, yf Rumex giganteus v v v, mf, d v, b, fl, yf, mf oahuense v, b, fl, yf, mf v, b, fl, yf, mf v, b, fl, yf, mf v, b, fl, yf, mf Amaranthus brownii b, fl, yf, mf slg, v, b, fl v, mf, sd, d v, b, fl, yf Portulaca lutea b,fl v, b,fl v, b,fl v, b, fl, mf v, b, fl, mf Portulaca villosa v, fl, mf v, b, fl, mf v, b, fl, mf v, b, fl, mf Schie dea vert icillata v, b, fl, sd, d v, fl, mf, sd, d v, fl, sd, d slg, v, b, fl, yf, mf, sd, d sp. v, b, fl, yf, mf v, b,fl v, b, fl, yf, mf v, b, fl, yf, mf cistoides v Euphorbia celastroides v,fl v,fl v, fl v,fl Sidafallax v, b, fl, yf, mf v, b, fl, yf, mf v, b, fl, yf, mf v, b, fl, yf, mf Ipomoea indica* v,fl v, fl v, fl v Ipomoea pes-caprae* v, fl Heliotropium curassavicum v, b, fl v Solanum nelsoni v, b, fl, yf, mf v, b, fl, mf v, b, fl, yf, mf v, b,fl, mf Sicyos nihoaensis slg, v, fl slg, v, b, fl, yr, mf, sd, d

NOTE: s = sori, slg = seedling, v = vegetative , b = flower buds, fl = open , yf = young fruit, mf = mature fruit, sd = seeds dropp ed, d = plants dead . *Plants were inaccessible so that I could not search for fruits and seeds.

Algae exhaustive collection s of lichens on Nihoa in 1981 and collected additional materials in Algae growing on moist surfaces and in 1983. These specimens will be deposited in the pools formed from fresh water seeps are a Bernice P. Bishop Museum after being iden­ relatively inconspicuous form of plant life on tified by C. W. Smith of the University of Niho a. During the 1983 expedition I collected Hawaii's Department of Botany. alcoholic specimens of algae from a variety of habitats (Conant 201-209, 212-215, 217, 218). K. Schlech (personal communication) Ferns examined the material, concluding that there Da valliaceae-sword fern family probably were three species of blue-green Nephrolepis multiflora (Roxb.) Jarret ex algae (Cyanophyta) and one species of green Morton (sword fern) (Chlorophyta) alga. The blue-green algae ap­ This fern was collected (Conant, s.n.) on peared to be in the order Oscillatoriales, the Nihoa for the first time in June 1981 (Conant most common of the three species probably in and Herbst 1983). Identification of these fer­ the genus Oscillatoria. Further identification tile specimens was made by D. Herbst and of the specimens awaits the attention of a C. H. Lamoureux. Although this fern is an specialist. alien species in Hawai'i (Lamoureux 1982), it Lichens probably arri ved on Nihoa by wind disper­ sal rather than by intentional or accidental Magnusson (1942) published a list of the human introduction. This is suggested by the lichens of Nihoa and Necker islands . I made location of the first colony (about I m2 in Plants of Nihoa Island - CoNANT 139

TABLE 3

OBSERVATIONS OF P LANT SP ECIES ON V ARIOUSE XPEDITIONS TO N IHOA I SLAND

PLANT SPECIES STATUS 1920s* 1961-1962t 1964-1968t 1969** 1981- 1983tt

Nephrolepis multiflora A + A + + + + Eragrostis variabilis I + + + + + Panicum torridum I + + + + + Paspalum sp. A + Setaria verticillata A + remo ta E + + + + + Rumex giganteus I + + + + I + + + + + Amaranthus brownii E + + + Boerhavia difJusa I + Tetragonia tetragonioides A + Portulaca lutea I + + + + Portulaca oleracea A + + + Portulaca vil/osa I + + + + + Schiedea verticillata E + + + + Sesbania sp. E + + + + + Tribulus cistoides I + + + + Euphorbia celastroides I + + + + + Sidafallax I + + + + + Ipomoea indica I + + + + + Ipomoea pes-caprae I + + Heliotropium curassavicum I + + + + So lanum nelsoni I + + + + + Solanum nigrum I + Sicyos nihoaensis E + + + +

NOTE: A = alien, E = endemic to Nihoa, I = indigenous to Northwestern Hawaiian Island. • (several trips). t Bureau of Sport Fisheries and Wildlife and Hawaii Division of Fish and Game. t Bureau of Sport Fisheries and Wildlife, Hawaii Division of Fish and Game, University of Hawaii, Pacific Ocean Biological Survey Program. •• Bernice P. Bishop Museum and Bureau of Sport Fisheries and Wildlife. tt S. Conant, this study. area) I found at about 213 m elevation on the Lamoureux. It seems likely that these small west ridge of Miller Valley (Figure 2), a site coloni es were established after August 1981, that is some distance from the usual landing because I traversed that particular area fre­ site. Nephrolepis multiflora probably is the quently during the summer of 1981 and prob­ first naturalized fern to be recorded from the ably would have noticed the plants if they had NWHI. There is also a record of the species been there. In April 1983, I collected (Conant from Midway (Herbst 1981); it is not known 114) additional material from the original whether this represents an accidental, inten­ colony, now reduced in size due to crowding tional, or natural introduction. by a clump of Eragrostis variabilis. In April 1983, I discovered two additional colonies of this fern growing in cracks of a Flowering Plants-Monocots volcanic dike near the base of Miller Ridge at about 50m elevation (Figure 2). The two Gramineae-grass family colonies were less than 4 m apart. Neither Cenchrus echinatus L. (sandbur) colony had more than 50 fronds, and neither In late May 1981, one small (about 20cm had any fertile fronds. Material was collected tall), dead plant with fewer than 10 fruits was from one of these colonies (Conant 104) and collected and destroyed as per the request of identified as Nephrolepis multiflora by C. H. FWS personnel. The collection was made at 140 PACIFIC SCIENCE, Volume 39, April 1985

• Cenchrus e c h t n e t u s ® Tribulus c is/a ides o He l i o t r o p i u m c urassav icum e::::::- DEVll ' SSLIDE • Ipomoea i n di c a M I~lJ}B' o I. pes- c a p r a e ~.~ , • Neph rolep is m ult iflo ra 40" 800 e:,. Rume x g igan/eus - 700

PINNAClE PEAK 0 626-

23' 03' 20" N N IHOA ISLAND

o 500 1000 It ~ I()O' 200 3~ O '"

40 " 20" 161' 55'00"W

FIGURE 2. D istributi on m ap for sev en of the less common plants found on Nihoa Island.

TABLE 4 the base of the ridge that divides Miller and West Palm valleys about 50m upslope from A VERAGE EsTIMATED P ERCENTAGE C OVER V AL UES FOR Emory's (1928) Site 10 (Figure 2). Although C OMMON V ASCULAR P LANTS, B ARE SOIL, ANDB ARE R OCK IN 74 P LOTS (76 x 76 m EACH) this species was seen or collected in 1961, ON NIHOA ISLAND 1968, and 1969 (Herbst 1977), it has not been reported between 1969 and 1981. My observa­ AVERAGE FREQUENCY OF tion of only one individual during approxi­ PERCENT COVER OCCURRENCE' mately 7 months ofwork over a 3-year period CATEGORY (%) (%) indicates that the species has failed to become Chenopodium oahuense 27 100 successfully established on the island. Bar e r ock 25 100 Eragrostis variabilis (Gaud.) Steud. ('emo ­ Solanum nelsoni 22 95 loa) Sida ja//ax 11 78 Eragrostis variabilis 1I 50 This perennial bunch grass is the fourth Bare soil 10 99 most abundant plant on Nihoa (I I% cover, Prilchardia remota 9 11 50% frequency ; Table 4). Eragrostis clumps Sesbania sp. 3 46 may exceed I m in height, and are spaced Euphorbia celastroides 2 11 20-30 em apart, often in dense stands. Ipomoea indica 2 1 Panicum torridum 1.5 12 Although it is relatively abundant, it is patchily Portulacea sp p. I 20 distributed, being most common on exposed Schiedea verticillata 0.5 3 slopes and ridge tops. The most extensive grasslands are on Miller and Tanager peaks •Frequency of occurrence was calculated by dividing the num ­ ber of plots in which the species or category occurred by the total and the ridges leading up to them. While these number (74) of plots. areas are not pure stands, other plant species Plants ofNihoa Island-CONANT 141 tend to be uncommon in extensive stands of by a temporary military installation, I did not Eragrostis. Single clumps or small stands are find it. scattered throughout the rest of the island. Setaria verticillata (L.) Beauv . (bristly Rainfall probably affects the amount and foxtail) time of flowering and seed set (Tables 2, 4). This plant was collected by Yen in 1969 For example, although flowering was noted in from "near [the] south coast" (Herbst 1977). I the winter 1981 period, no fruits were ob­ did not find it. served. Specimens of this species were col­ Palmae-palm family lected on the 1983 expedition (Conant 106, Becc. (Io'ulu) 107). Nihoa's endemic lo'ulu palm is certainly the Eragrostis bunches are the sole habitat for island's most conspicuous plant, though it is Nihoa's seven land snail species, which in­ restricted to two valleys (East and West clude six endemic and one indigenous species Palm), one at each end ofthe island. The cover (Conant et aI. 1983). estimate for this species was 9%, and the Panicum torridum (Gaud.) (kakonakona) frequency of occurrence (II %) reflects its This annual grass is found seasonally limited distribution (Table 4). Herbst (1977) (Table 2) throughout the island, though it is reported his careful count of the palms in much more abundant on the valley floors and 1968, noting numbers of plants in different other places where moisture may accumulate size classes. Herbst's count and the one made and persist. Our quantitative estimate ofcover by C. R. Long (reported by Herbst 1977) in by this species was less than 2% (Table 4). 1964 were the most exhaustive ever made, This estimate is probably low because it was including, unlike previous counts, enumer­ made in August 1981, when all the plants had ation of seedlings. These counts are included died and withered. in Herbst's (1977) report, and reveal that there It is likely that the abundance ofthis species were 500-600 trees. varies considerably from year to year. Sincock Long noted that there were 173 trees with (unpublished data) estimated the total aver­ fruit or flowers in his September count, and age cover by this species in June 1969 to be Herbst noted 182 trees with fruit or flowers in 5% , a much higher estimate than ours. Herbst his August count. Although I did not count (1977) noted that the abundance of this the palms, I took a few notes on their repro­ species varies considerably on . ductive phenology (Table 2). With the per­ During a 5-day visit to Necker in late June mission of the FWS I collected seeds in 1982, Panicum torridum was very abundant August 1981 for distribution to arboreta and (as high as 25-50% cover in some sample horticulturists. At that time I found fewer plots), and there were still numerous green than ten trees in either valley with mature fruit clumps that were in flower. However, in late from which I could make collections. No re­ June 1984, very few living plants ofthis species productive structures were observed in the were observed during a l-week visit to winter of 1981. Necker. The Nihoa lo'ulu provides nesting, loafing, This plant does not appear to provide much and roosting habitat for red-footed boobies habitat for terrestrial invertebrates, although (Sula sula rubripes), which nest only in bushes during field work on Necker Island in 1982, and trees, rather than on the ground. Oc­ P. Conant (unpublished data) collected a few casionally, brown noddies (Anous stolidus species of insects from it. pi/eatus) perched on or attempted to nest in Paspalum sp. the lo'ulu trees. A plant was recorded, but not collected, by R. J. Kramer and J. W. Beardsley (unpub­ Flowering Plants-i-Dicots lished manuscript, FWS) from Albatross Polygonaceae-buckwheat family Plateau (area immediately north of Miller Rumex giganteus Ait, Peak) in 1962. Although I searched for it This perennial is one of Nihoa's rarest there, particularly near the debris left behind plants, previously recorded only from the 142 PACIFIC SCIENCE, Volume 39, April 1985

Devil's Slide-Miller Peak area (Herbst 1977). were intermixed. Rumex seeds and rooted Figure 2 shows the distribution of plants r shoots collected from this colony and sent to found on my expeditions. On 3 February the Waimea Arboretum failed to grow. 1981 , I found two small colonies of sterile Chenopodiaceae-goosefoot family Rumex plants on Tanager Peak; and on 25 Chenopodium oahuense (Meyen) Aellen June 1981, I found three colonies, two in ('aweoweo) flower, in the same area. I suspect that these This is the most abundant plant on Nihoa, finds represent a total of just three colonies with an estimated cover of 27% and a sample because the plants are rather obvious and the frequenc y of 100% (Table 4). This widely dis­ locality distinctive. The Tanager Peak plants tributed species grows in dense, nearl y mono­ were all on the northwest face of that peak. specific stands in a few areas-for example, Seeds were collected from other plants found the west slope of Miller Valley. There were in June 1981 and sent to D. Herbst of the nearly always some individuals of this species FWS, who passed them on to the Waimea in flower (Table 2), and my notes on its phe­ Arboretum. The seeds were not successfully nology are insufficient to determine whether germinated. there was a peak of flowering or flushing at Rumex is one of the few plants that may any particular time. exhibit some seasonality in reproductive ac­ Chenopodium was one of the plants whose tivities, with flowering and seed set being flowers and fruits were most frequently eaten primarily spring and summer phenomena. No by Nihoa finches. In addition, this plant sup­ reproductive structures were observed in the ports the densest populations ofinsects (W. C. winter of 1981. Although the same is true of Gagne, personal communication), making it the summer 1980 expedition, it should be an important foraging substrate for the insec­ noted that only two plants were observed at tivorous Nihoa millerbird. that time. - family On 3 June 1980, I noted two sterile plants Amaranthus brownii Christophersen and 10-15 m apart on the north-facing side of Caum Devil's Slide, which is contiguous with the This plant was collected on the Tanager base of Miller Peak. The following June, I Expedition in 1923, but it was not seen again noted a single sterile plant about 25 m above until 1969 when D. Yen collected it near Mil­ and to the west of the locality of the plants ler Peak (reported by Herbst 1977). Christo­ observed in 1980. All the rest of the Rum ex phersen and Caum (1931) described the individuals I observed were on the floor of species from 1923 collections, noting that Devil's Slide growing in deep soil, in contrast Caum and C. J. Judd had found the plant to to the other plants, which were growing on be "common" on Miller Ridge and "abun­ rocky outcrops in pockets of shallow soil. dant also on ridges to the east:" In contrast, On 15 August 1981, I found a Rumex my observations indicate that the plant was colony with three separate groups of plants in very rare , at least in recent years. Devil's Slide. All the plants were growing next This plant is the only member of its genus to the northwest wall of the Slide. My count endemic to the Hawaiian Islands, and its dis­ puts this colony at about 22 plants, all of tribution is limited to Nihoa Island. It is the which appeared to have several stems capable island's rarest nati ve plant with the possible of producing flowers and fruit. It was often exception ofTribulus cistoides. The total num­ difficult to distinguish one individual from an­ ber of individuals of this annual species I ob­ other when plants were close together, making served during my visits did not exceed 35. this count only approximate. Furthermore, Based on phenological observations (Table 2), the plants have large fleshy , and there r estimate that the growing season of this may have been some dormant individuals species probably extends from about Decem­ with no stems above ground. This colony was ber through July. Figure 3 shows the distri­ adjacent to a large colony of Schiedea verti­ bution of the plants I observed. cil/ata, and at some places the two species The earliest month of the year in which I Plants of Nihoa Island -CoNA NT 143

~ S i c yo s n i ho aen s is ~ DEVIL 'S SLIDE • Ama rant h u s b r o w n i i M lll ~ PEA ~ 895 40" 800./ -700

PINNACLE PEAK 0 626-

23· 03' 20" N

~ s~o 10p OIt o UlO 200 300 ..

40" 20" 161· SS'OO"W I

FIGURE 3. Distribution of Amaranthus brownii and Sicyos nihoaensis on Nihoa Island . observed plants was February (1981), when I soil and scattered Chenopodium bushes . Ear­ found 22 plants growing at about 175m ele­ lier in the seasons of both 1981 and 1983 there vation on the west ridge of Miller Valley about had been a colony of Panicum torridum, most 5 m below the crest of the ridge on the east side of which was dead or dying in late April 1983 (Figure 3). On 16 February, I noted that 20 and entirely dead in June 1981. In February plants were less than 10cm tall, I plant was 1981, the Panicum was robust and beginning 15em tall, and I plant was 35 ern tall. The two to flower. It is interesting to note that in 1983, taller plants were in a very early stage of numerous Sicyos seedlings were present in the flowering. On I I June 1981, I returned to this same small area occupied by dying Panicum colony to find 23 plants, all of which had died and the Amaranthus plants. Perhaps Sicyos or were dying. Some were in such deteriorated and Amaranthus share similar habitat re­ condition that it was impossible to be sure quirements. they had flowered, but most ofthe plants had The seeds that I collected in 1981 were de­ actually set seed. I collected seed from 5 stand­ posited with the Waimea Arboretum and the ing plants and one I found on the Royal Botanic Gardens at Kew in England . soil surface . When I examined this colony area Although the seeds at Waimea germinated again on 21 August 1981 , I found a single and grew for a time, none of the plants at plant still standing but apparently dead . All Waimea survived beyond the seedling stage . other plants observed were found on the late The fate of the seeds that were sent to England spring-summer expeditions. is not known. The habitat in which the largest Amaran­ The extremely low numbers in recent years thus colony was found (on Miller Ridge) was and the limited distribution of this endem ic characterized by rocky outcrops with shallow plant suggest that it should be carefully moni - 144 PACI FI C SCIENCE, Volume 39, April 1985

S c h i e d e a verticil/ata

40"

23­ 03' 20" N NIHOA ISLAND

o . 500 1000 It I ' I o 1l\0 200 300 ..

40" 20 " 161- 55'OO"W

FIGURE 4. Distributi on map of S chiedea verticillata colonies on Nihoa Island. tored, as it is one of the rarest endemic Portulaca oleracea L. (common purslane) Hawaiian plants. Portulaca villosa Cham. Nyctaginaceae-four o'clock family Herbst (1977) wrote that Portulaca lutea Boerhavia diffusa L. (alena) "grows in shallow, rock y soil and in cracks As Herbst (1977) mentioned, this plant along the lower south side," and that there "was found only on the sandy beach in Adams was a large colony at the northeast end of Bay and may have washed away." Numerous Miller Plateau. I searched thoroughly for this scans of the beach with 10 x 40 binoculars species throughout my various expeditions, revealed no vegetation at all on the beach. In but was unable to find a single plant. How­ fact, during the 1981 winter expedition, the ever, W. C. Gagne (personal communication) beach was completely awash during high located and photographed a single flowering tides, and high water reached all the way to the plant on the east ridge of Miller Valley at an base of the cliffs behind the beach during a elevation of about 50 m. Th e plant was grow­ heavy storm. ing on the ridge top in a pocket ofsoil. Herbst Aizoaceae-carpetweed family (personal communication), who visited Nihoa Tetragonia tetragonioides (Pallas) Ktze. in 1980, confirmed my impressions that this (New Zealand ) plant is rarer now than it was during his visit in Careful observations of the cliffs above the 1968. beach where this plant had been found (Herbst In contrast to Portulaca lutea, P. oleracea, 1977) failed to reveal this species, and I concur which Herbst (1977) found in only two with Herbst that it probably has failed to colonies on Miller Plateau and at the mouth of become established on Nihoa. .. Miller Valley, has spread over the entire -purslane family island . This species, which produces abundant Portula ca lutea Forst. f. ('ihi) seed, can be found in pockets of shallow soil

.====.lni....t ..... C I • ...... ====::z::=:no:z..::::::::::o:::o...... ,.=....c Plants of Nihoa Island-CoNANT 145

TABLE 5 LOCATION,POPULATIONCOUNTS, AND PHENOLOGY OF Schiedea verticil/ata ON NIHOA

PHENOLOGY·

NO. OF NO. OF PLANTS WITH NO. OF PLANTS WITH LOCATION DATE PLANTSt BUDS AN DFLOWERS SPENT FLOWERS

Devil's Slide 15/8/81 96 20 76 30/4/83 100± 7 Miller Peak OS/2/81 5 30/4/83 2 I Upper West Palm 04/7/80 2or3 Too far for specific observations Pinnacle Peak 04/7/80 15 9 6 21/6/81 25 5 20 Lower West Palm 14/2/81 30 30 22/6/81 38 No phenol ogy data recorded Dog's Head , basel 04/7/80 43+ 13+ Approx.30 Dog's Head, summit 04/7/80 52 50 3 21/6/81 29 4 25 East spur colon y 25/6/81 148 No phenology data recorded

• These values are numbers of plants showing the specified cond itions. In some cases a plant could have both buds and spent flowers and be counted in two categories. t Each individual plant may have 1- 8 bran ches capable of producing flowers. t This colony was observed with 10 x 40 binoculars from the cliff above the east side of the beach. The total number of plants is probably considerably greater than the 43 actua lly counted, as it would have been virtually impossible to count very young plant s. virtually everywhere, though it is most com­ -pink family mon near ridge tops. It is not clear whether this Schiedea verticil/ata F . Br. exotic species is replacing the indigenous P. During the four expeditions I located eight lutea, as there is still abundant suitable habitat different colonies of this endemic Nihoa for both species, even taking into consider­ species ranging in size from 2 to 150plants. As ation the tendency of P. lutea to be limited to nearly as I can determine, previous collec­ the zone of salt spray (H. St. John, personal tions were made from at least three of these communication). Portulaca oleracea is the colonies: Lower Dog's Head, Miller Peak, and only widespread exotic species on Nihoa, and Devil's Slide (Figure 4). I collected a single is apparently the only established exotic plant fertile specimen from the Devil's Slide col­ on the island. ony (Conant 115). I counted the plants in The distribution of Portulaca vil/osa re­ each colony one or two times, usually noting mains as Herbst (1977) described it, i.e.,"in the numbers of plants in various phases pockets of soil and in cracks throughout the of the life cycle. These data are given in island ." I saw examples of both the common Table 5. white-flowered form and the much rarer (on Very few plants were found with buds and Nihoa) form in which the outer edges of the flowers, but large numbers of postflowering petals are pink. Though taken collectively the plants were recorded, though none had seeds. Portulaca species are relatively widespread Judging from these data, Schiedea verticil/ata (sampling frequency of 20%), they are not plants probably come into flower, set and dis­ very abundant, their estimated cover being perse seed in a short period oftime. However, less than I % (Table 4). Unfortunately, I did phenological data (Table 2) do not indicate not separate the species when estimating cover that the reproductive cycle is seasonal. W. C. values. Gagne (personal communication) noted that 146 PACIFIC SCIENCE, Volume 39, April 1985 the were sticky enough to have wide distribution on the island (sampling fre­ trapped small insects. quency II %), though its total cover was less The plant could be considered locally com­ than 2% (Table 4). It sometimes grows in mon on Nihoa, but certainly not abundant, dense monospecific stands-for example, on covering less than 1% of the sampling area, Miller Peak and just above the west end of the and appearing in only 3% of the plots (Table sand beach . I found flowering plants on all my 4). Its population status appears to be stable; expeditions (Table 2), but my observations are nevertheless, it is a relatively rare plant and insufficient to conclude that flowering is sea­ should be regularly monitored. sonal. Due to my lack of experience with the Leguminosae-pea family species and limited observation time, I did not Sesbania sp. Cohai) see any fruits or seeds on the species, though This attractive legume, whose closest rela­ they may have been present. tives are rare in the main islands (St. John W. C. Gagne (personal communication) 1981), is relatively common on Nihoa. In the noted that the flowers were visited by large sampling plots it occurred with a frequency of numbers ofants, which might have a negative 46%, but it is not abundant, as its estimated impact on any native insects that are host­ total cover was 3% (Table 4). I estimated that specific to this plant or on seed production in there are several thousand plants on Nihoa, the plant itself. Dense stands ofthis species on but this estimate is based on counts of indi­ Miller Ridge and Miller Peak are an impor­ viduals in only 10 of the 74 sampling plots. tant nesting habitat for Christmas shear­ Flowers were observed on all visits (Table 2), waters (Puffinis nativitatis). The major nesting though they were most abundant in April and colonies ofthis bird are in stands of Euphorbia May. Mature fruits were observed only in and Eragrostis variabilis on Nihoa. spring and summer months. Malvaceae-mallow family In previous publications this plant was Sidafallax WapI. Cilima) called , but recent research Herbst's (I977) description of this plant as by W. Char has revealed it to be an unde­ "common over the entire island" can hardly scribed species which will be described else­ be improved upon, and I found it in 78% of where. my plots. However, it is not as abundant as it -tribulus family is widespread, since its estimated cover was Tribulus cistoides L. (nohu) only II % (Table 4). Flowering was in greatest Earlier reports of this species include rec­ evidence during May 1981 and April -May ords from the back of the west ridge ofMiller 1983, when one could traverse many hectares Valley, the bottom of West Palm Valley, and dotted with the small attractive orange flowers on the south sides of upper slope cliffs(Herbst of this plant. I did not make specific searches 1977). I made only one sight record of this for seeds and fruits of this species while mak­ species on 3 February 1981 at the top of the ing phenology notes. In the saddle between west ridge of East Palm Valley (Figure 2). The Miller and Middle valleys, and on the west cluster ofplants was only I m from the edge of side of the head ofEast Palm Valley, are areas the cliff. The fact that I observed only one where there are several hectares ofnearly pure colony in my extensive movements over the stands of this species. This plant is attractive island suggests that the species is rare. How­ to Nihoa finches, which I observed eating its ever, the existence of records from a variety of seeds and buds . locations suggests that it may be frequently Convolvulaceae-morning glory family introduced by seabirds to which its thorny Ipomoea indica (Burm . f.) Merr. f. indica fruits may attach. (koali 'awania) -spurge family Herbst (1977) summarized the records of Euphorbia celastroides Boiss. var. celas­ this species as being from two areas: on the troides Cakoko) north face of Miller's Peak about 10-15 m This plant is found primarily on windswept below the summit and above the sand beach. I ridge tops on Nihoa, and it has a relatively observed the species in both locations (Figure Plants ofNihoa Island- CONANT 147

2). The Miller Peak colony was smaller, 20 m2 lavender in color and have dark purple centers at best. However, there are two large colonies as well. above the beach. One is on the steep cliff Fruits were much less abundant than above the west end of the beach , where there flowers, suggesting tha t pollinators may have 2 are at least ten small (5- lOm ) colonies or been low in number or at least ineffective. For plants. The other is a single large colony example, we observed very few individuals (about 100 m") at the base of the tall stony of the native bee, Neoprosopis perk insiana. face at the west side of the mouth of West Fruits were green when immature, turning Palm Valley. Due to the inaccessible nature of first to a reddish orange and then to dark the colonies, I could not search for fruits and brown or black when ripe. seeds, and I collected no specimens of this So/anum nigrum L. (popolo) species. This is another ofthe species reported from Ipomoea pes-caprae subsp. brasiliensis (L.) Tanager Expedition collections that has not v. Ooststr. (pohuehue) been reported again, and I found no plants I found no trace of the colony reported by anywhere even after a thorough search of the Yen (Herbst 1977) when I surveyed the area collection locality . above the beach with binocul ars. However, I Cucurbitaceae-gourd family did make a sight record (using 10 x 40 Sicyos nihoaensis St. John binoculars) of a colony about 5 m 2 in area at This species, endemic to Nihoa, has been the base (10m elevation) of the north face of reported (Herbst 1977) only from three areas the spur on the island 's east side (Figure 2). on Nihoa: below Tanager Peak (in 1924), The colon y was west of the point where Tun­ upper West Palm Valley (in 1961 ), and on nel Cave goes through the spur, and it was Albatross Plateau north of Miller Peak (in quite inaccessible, growing on a ledge in the 1962). Sicyos nihoaensis is an annual with a sheer cliff. growing season that probably begins follow­ Boraginaceae-heliotrope family ing heavy rainfall. On Nihoa the late winter Helio tropium curassavicum L. (seaside helio­ and spring months seem the most likely times trope) one could expect to see this plan t growing I found a small colon y of this species on 25 there (Ta ble 2). The paucity of observations May 1981 with several individuals growing at are probably due to the fact tha t it grows the bottom of the talus slope abov e the east primarily during the season when safe land ing edge of the beach (Figure 2). Although I did on the island is most difficult. My observa­ not collect specimens, I did photograph the tions (Figure 3) do not reveal a much more species. This colon y is probably at about the extensive distribution than that outlined by same location as the one Yen found in 1968 Herbst, but the species can be locally very (reported by Herbst 1977). Earlier records are abundant during its growing season , partic­ from collections on or adjacent to the beach . ularly during a wet year. Solanace ae-nightshade family In February 1981 , I found Sicyos in large So/anum ne/soni Dunal numbers at the top of DeviI's Slide, particular­ Like Chenopodium, this plant is abundant ly just below Miller Peak, and I attempted to and widespread on Nihoa, averaging 22% census the three different colonies in this area. cover (Table 4). It occurred in 95% of the From a vantage point on the northwest wall of sampling plots. There were a few flowers to be Devil's Slide, I counted 27 individual vines, found at all times on my expeditions (Table 2), but on closer examination of the colonies but in April- May 1983 most plan ts had large many additional smaller vines and seedlings numbers of flowers. There were also large were found. Based on these observations I numbers of plants in flower in May 1981. The estimated the total number of plants in these flowers ofthis plant on Nihoa have petals that three colonies to be about 60- 80 individuals. are primarily creamy white in color but with Another colony ofSicyos on the north edge of dark purple centers. In contrast, on Pearl and Albatross Plateau was inaccessible, but with Hermes Reef the petals are light purple or the aid of binoculars, I estimated the number 148 PACIFIC SCIENCE, Volume 39, April 1985 of plants at that locality to be about 15-20. I at least 35 species ofendemic, terrestrial arth­ saw no other colonies in 1981. ropods; 6 species of endemic land snails; 2 In April 1983, W. C. Gagne (personal com­ species of endemic land birds ; and 17 species munication) saw a colony of Sicyos seedlings of breeding seabirds numbering over half a numbering in the high hundreds or low million individuals (Conant et al. 1983). thousands on the west face of Tanager Peak The scientific value of the island is out­ about 20 m from the summit. The area was a standing, as it provides a nearly undisturbed series ofrocky ledges where Panicum torridum example of a lowland, dry Hawaiian com­ had died back . Many of the seedlings still had munity, almost untouched by the perturba­ their cotyledons attached. tions ofcontinental cultures so familiar to the Gagne and I located two Sicyos colonies in main Hawaiian Islands. In particular, the April 1983. The first of these was adjacent to large number of endemic arthropods and or intermixed with plants in the Amaranthus mollusks, some of which may be peculiar to colony on Miller Ridge (see section on A . large colonies with their immense in­ brownii). There were about 30 Sicyos vines puts of nutrients via seabird , provide in this colony. Some were seedlings with an opportunity for ecological studies of a cotyledons and some were mature vines with sort as yet unexplored by naturalists in the flowers and fruit, although none ofthese vines Hawaiian Islands. Similarly, the island is had ripe fruits . At the top of Devil's Slide, on noted for its unique cultural value in the form the east southeast side, we found another of extensive, remarkable, and virtually un­ colony covering an estimated area of 200 m 2 studied archaeological sites. or more , with hundreds of plants of all ages As part of the Hawaiian Islands National from seedlings to vines with ripe fruits. This Wildlife Refuge, the island is protected by the colony was so large, and our time so limited, limiting of all human access except specifically that I was unable to attempt a census of the permitted and closely regulated scientific re­ plants. Seeds and seedlings were collected and search. Proposals to allow very limited , and eventually deposited at the Waimea Arbore­ also closely regulated, access for Hawaiian tum. Phenological observations are summa­ religious ceremonies are being considered by rized in Table 2. the FWS . As long as such uses are controlled Sicyos nihoaensis could be said to have a so as to prevent disturbance to the biota, and, restricted distribution on Nihoa, and is a particularly, to prevent the introduction of species whose limited growing season makes it new species of organisms, it is unlikely that (like Amaranthus brownii) a difficult species to Nihoa's ecosystems will be significantly dis­ monitor. Although it is rare, its status could turbed. However, in order to assure adequate be considered relatively stable as long as no protection ofthe island from disturbance, it is disturbance to its habitat (e.g., introduction of' essential that monitoring of terrestrial ecosy­ exotic plants or insect pests) occurs . stems, including plants, invertebrates, land­ birds, and seabirds, be conducted on a regular basis. In addition, agencies responsible for protection of the biota should be prepared to CONCLUSION cope immediately with the elimination of any The flora of Nihoa provide a unique ex­ perturbations as soon as they are detected. ample of a lowland, coastal type ofecosystem in Hawaii because it has remained unaffected for as long as 500 years by the impacts of an apparently brief human occupation. Today ACKNOWLEDGM ENTS the flora consist of 20 species, which range The Bernice P. Bishop Museum provided from extremely rare to very common. Five facilities for research activities, and their staff of these species are endemic to this island . has been helpful in curating specimens. I Nihoa's plant communities provide the most would like to thank the crews of the vessels important constituents of essential habitat for NOAA Ship Townsend Cromwell, the Easy Plants of Nihoa Island-CoNANT 149

Rider, and the Irnua for their assistance 25-27 May 1983:77-94. Sea Grant Coli. embarking and disembarking expeditions. Prog. University of Hawaii, Honolulu. D. Herbst, C. H. Lamoureux, and H. St. John EMORY, K. P. 1928. Archaeology of Nihoa answered many questions abo ut plants in the and Necker islands .Bernice P. Bishop Mus . Northwestern Hawaiian Islands, identified Bull. 53. specimens, and encouraged me in my work . HERBST, D. 1977. Vegetation. Pages 26-38 in C. J. Ralph assisted with some aspects of R. B. Clapp, E. Kridler, and R. R. Fleet. research design. Saul Price of the National The natural history of Nihoa Island , Weather Service and the U.S. Fish and Wild­ Northwestern Hawaiian Islands. Atoll Res. life Service provided rainfall data. G. Carr, Bull 207. D. Herbst, R. L. Stemmermann, and an anon­ - - -. 1981. Checklist of the vascular plants ymous reviewer made helpful comments on ofthe Northwestern Hawaiian Islands. Un­ the manuscript. Barbara Hoshida typed the published manuscript. manuscript with skill and patience. Base maps LAMOUREUX, C. H. 1982. The fern genus were provided by the U.S. Fish and Wildlife Nephro lepis in Hawaii. Proc. 4th Conf. Service, Hawaiian Islands National Wildlife Natur. Sci., Hawaii Vol. Nat. Park, 2-4 Refuge, and Regina Kawamoto added the June 1982: 112-117. Cooperative National plant distributions to them. Park Resources Studies Unit, Department ofBotany, University ofHawaii, Honolulu. MAGNUSSO N, A. H. 1942. Lichens of Nihoa and Necker islands . Bernice P. Bishop Mus. Occ. Pap. 17: 1- 41. LITERATURE CITED OLSON, S. L., and H. F. JAMES . 1982. Pro­ CHRISTOPHERSEN, E., and E. L. CAUM . 1931. dromus of the fossil avifauna of the Vascular plants of the Leeward Islands, Hawaiian Islands. Smithsonian Contr. Hawaii. Bernice P. Bishop Mus. Bull. 81: Zool. 365. Smithsonian Institution Press, 1-41. Washington, D.C. CONANT, S. 1983. Observations of migran t PALM ER, H. S. 1927. Geology of Kaula, and vagrant birds on Nihoa Island . 'Ele­ Nihoa, Necker, and Gardner islands and paio 44: 23-25. French Frigate Shoals. Bernice P. Bishop CONANT, S., and D. HERBST. 1983. A record of Mus. Bull. 35: 1-35. Nephrolepis multiflora from Nihoa Island, ST.JOHN, H. 1973. List and summary of the Northwestern Hawaiian Islands . Newsl. flowering plants in the Hawaiian Islands. Hawaiian Bot. Soc. 22: 17- 19. Pac. Trop. Bot. Gard., Mem. 1: 1-519. CONANT, S., C. CHRISTENSEN, P. CONANT, - --. 198~ . Rare endemic plants of the W. GAGNE, and M. L. GOFF. 1983. The Hawaiian Islands . Book 1. State of Hawaii, unique terrestrial biota of the Northwestern Department of Land and Natural Re­ Hawaiian Islands . Proc. Symp. Resource sources, Division of Forestry and Wildlife, Invest. Northwestern Hawaiian Islands, Honolulu.