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Senna gaudichaudii

PTBG1000003533

043205

8300

K. R. Wood

March 8, 2000

PTBG

Fern Duvall, Steve Perlman, Steve Montgomery

Hawaii

US

HAWAIIAN ISLANDS

Molokai

HI

Maui County

84

Mokapu, offshore islet east of Kalaupapa Peninsula.

dicot

shrub, many branched, in early fruit, ca. 20 individuals on the east side below Station 6 (75--90 m [250--300 ft] elevation);

Yes

Chamaesyce celastroides/Chenopodium oahuense coastal dry shrubland with Diospyros forest.

With Osteomeles anthyllidifolia, Artemisia australis, Sida fallax, Schiedea globosa, Plumbago zeylanica, Dianella sandwicensis, Melanthera integrifolia, Lepidium bidentatum, Senna gaudichaudii, Portulaca lutea, Pittosporum halophilum, Pritchardia hillebrandii

Personal Observations of Mokapu Islet Including a Regional Checklist of Vascular Plants Moloka`i, Hawai`i Special Report Prepared for Kalaupapa National Historic Park K. R. Wood, National Tropical Botanical Garden, Department of Conservation, kenwood@ntbg.org 3530 Papalina Rd, Kalaheo, Kaua`i, Hawai`i 96741 M. LeGrande, University of Hawai`i at Manoa, Botany Department,legrande@hawaii.edu St. John Hall, Rm. 101, 3190 Maile Way, Honolulu, Hawai`i, 96822 ABSTRACT: This report is a summary of two trips conducted on Mokapu Islet. During 8-9 March 2000, one of the authors (Wood) participated in a biological survey of Mokapu Islet with F. Duvall, S. Perlman, and S. Montgomery. A second trip (Wood & LeGrande) was conducted on 21-23 November 2001 and focused on rat trapping and conservation seed collections. Ecological observations of vegetation in relation to monitoring stations and confirmation of Rattus exulans presence are hereby presented along with management recommendations for the conservation of Mokapu’s unique biota. Mokapu. Mokapu is an offshore islet of 110 meters (360 ft) elevation located around 1050 m (3,445 ft) off Leinaopapio Point, and 2.4 kilometers (1.5 miles) east of Kalaupapa Peninsula (21° 11. N; 157° 55. W) on Moloka`i's north shore. Mokapu is managed by the DLNR as a Hawaii State Seabird Sanctuary.. Mokapu measures approximately 390 meters (1 279 ft) north to south by 145 meters (475 ft) east to west, with an area of 41,664 sq. meters. K. R. Wood and F. Duvall were able to set up 15 stations at 15 m (ca. 50 ft) intervals along the relatively flat and narrow (2--3 m wide) summit ridge. These numbered stations are tagged and represent fixed points within the central 210 m (north to south) zone and average ca. 90 meters elevation. Below the northernmost station (i.e. Station 1) and the southernmost (i.e., Station 15) the ridge drops steeply for an additional 80-100 m down to both extreme points on the islet. The precipitous northern and southern slopes along with both eastern and western aspects range between an extremely steep (45°) to vertical gradient and require climbing ropes to safely research. It should also be noted that the loose talus nature of the substrate may cause occasional rolling rocks. Ecology of Mokapu. Botanically, Mokapu represents a Chamaesyce celastroides var. amplectens (Euphorbiaceae) - Chenopodium oahuense (Chenopodiaceae) coastal dry shrubland with regions dominated by a relictual Diospyros sandwicensis (Ebenaceae) forest. Most of the Diospyros can be found on the western slopes (ca. 100 trees), and an additional grove can be found on the northeast corner of the islet below Station 1 (ca. 30 trees). Other relictual native tree species in their order of abundance include: Santalum ellipticum (Santalaceae), known from a grouping of ca. 20 on the east side below Station 2; Pritchardia hillebrandii (Arecaceae), with a grouping of three to the north-east of Station 1, two on the eastern slopes below Station 6 & 7, and seven mature with a single seedling on the western slopes below Station 7, totaling 12 mature; Reynoldsia sandwicensis (Araliaceae) located on the north-east corner of Station 1, of which only one of the three individuals were living at the time of the 2000 survey. Two appear to had recently died, leaving one small, 1.5 m tall individual. On the return trip in 2001, none of the Reynoldia trees were observed alive. An extended drought period over the past two years is most likely responsible for the mortality of the Reynoldsia along with several other plant taxa observed to have recently died. Besides the Chamaesyce and Chenopodium dominants, other native shrub components of Mokapu in their order of abundance include: Osteomeles anthyllidifolia (Rosaceae), which can become a co-dominant along the central ridge region between Station 2 and Station 9; Scaevola taccada (Goodeniaceae), observed in a grouping of ca. 30 individuals on the far north-eastern point (ca 30 m [100 ft] elevation); Senna gaudichaudii (Fabaceae), with ca. 20 individuals on the east side below Section 6 (75--90 m [250--300 ft] elevation); and Pittosporum halophilum (Pittosporaceae) of which 13 plants were observed on the north-east corner below Station 1 (45 –70 m [150—220 ft] elevation), with an additional two plants documented on the southeast corner below Station 15 (60 m [200 ft] elevation) totaling 15 individuals found on the March 200 trip. On our return trip to the island in 2001 one of the southern individuals had died and only 10 individuals from the northern population were relocated. Pittosporum halophilum represents a significant occurrence as there were previously only two individuals of this species known and restricted to the adjacent islet of Huelo. Seed collections were made from three separate individuals of Pittosporum halophilum during the first trip and additional fruit were collected from three separate plants on the most recent trip. All eleven remaining Pittosporum individuals were tagged and numbered to aid in the continued monitoring of the population and future conservation seed collections. Native sub-shrubs randomly mixed throughout Mokapu in their order of abundance include: Sida fallax (Malvaceae), which ranged between 25--100 cm (10--40 in) tall, with several hundred individuals; Plumbago zeylanica (Plumbaginaceae), widely distributed and totaling several hundred; Artemisia australis (Asteraceae), which could be found on the vertical basalt substrate; Portulaca lutea (Portulacaceae), which occurred along the lower north-eastern slopes below Station 1; and Lepidium bidentatum var. o-waihiense (Brassicaceae) which was seen on the east side below Station 7. Native herbaceous species in order of abundance include: Schiedea globosa (Caryophyllaceae), of which several hundred plants were observed on the steep northern slopes below Station 1; Melanthera integrifolia (Asteraceae [formally Lipochaeta]), which could be observed along the lower slopes throughout the islet; Peperomia blanda var. floribunda (Piperaceae), found growing mostly in cool shady regions below Diospyros; Plectranthus parviflorus (Lamiaceae), also found in cool shady regions; Peucedanum sandwicense (Apiaceae), numbering around 20 individuals on the north-east corner and just beginning to go into flower; Dianella sandwicensis (Liliaceae), with only a few sightings on the northern end of the islet; Solanum americanum (Solanaceae) which were observed mostly along the western side of the main ridge between Station 2—10; and Waltheria indica (Sterculiaceae), occasionally observed on steep slopes of basalt and in association with lichen, on the lower southern end of the islet. Native liana species included Cassytha filiformis (Lauraceae), which was common along the main ridge and scandent in the shrubland; and Ipomoea tuboides (Convolvulaceae), of which several vines were observed on the northern slopes below Station 1. Native Grasses and sedges include: Cyperus phleoides var. phleoides (Cyperaceae), which was occasional along the summit ridge; and Eragrostis variabilis (Poaceae) occasionally observed clumping along the main ridge in flower and fruit, with scattered patches scattered in open areas of the islet. It would be interesting to document the grasses of this islet after an extended rainy period as several native grass components (e.g., Panicum) seem to be missing. The only native fern observed was Doryopteris decipiens (Pteridaceae), of which approximately 30 plants were seen on the northern slopes below Station 1. Considering the recent drought period, it is likely that this fern species is far more common than it appeared at this time. Weedy vascular plant species found on the islet in their order of threat and abundance includes: Lantana camara (Verbenaceae), Digitaria insularis (Poaceae), Kalanchoë pinnata (Crassulaceae), Pluchea carolinensis (Asteraceae), Schinus terebinthifolius (Anacardiaceae), Ageratum conyzoides (Asteraceae), Portulaca oleracea (Portulacaceae), Coronopus didymus, (Brassicaceae) Sonchus oleraceus (Asteraceae, Malvastrum coromandelianum subsp. coromandelianum (Malvaceae), Morinda citrifolia (Rubiaceae), Plantago lanceolata (Plantaginaceae), Pseudelephantopus spicatus (Asteraceae), and Phymatosorus grossus (Polypodiaceae). Control measures for the weedy plants on Mokapu should focus on eradication of Lantana camara which is outcompeting the native plant communities on the summit and upper slopes of the island, as well as monitoring the continued spread of Kalanchoë pinnata invading the most serious areas of erosion on the island. The west facing side of the island below stations 2 and 3 is showing the effects of the complete lack of regeneration of lama trees leading to heavy soil erosion. The lack of regeneration of the larger trees and shrubs on the island led the team of biologists on the 2000 survey trip to theorize that rat predation of native seeds was the leading cause for the decline. Rats: One of the main goals for the November 2001 trip was to confirm the presence of rats on the island. The authors received 20 rat snap-traps from the USFWS and guidelines on setting and baiting the traps. The day before the traps were set, pieces of fresh coconut were broadcast from the summit of the island to the east and west near station four. The traps were baited with fresh coconut pieces and one or two snap-traps were placed below each of the stations along the ridge top, either to the west or to the east. Aves. Several bird species were observed to be residents or visitors of the islet. Wedgetail shearwater juveniles appeared to be at the end of their nesting season. We estimate at least 60 juvenile birds had yet to fledge One koa`e kea or white-tailed tropic bird juvenile was observed in a nest on the north side of the islet, with several more juveniles heard lower on the west side of the island. The Koa`e kea were by far the most abundant adult sea birds on Mokapu. They could be seen flying around the islet throughout the day with their distinct “chattering” calls frequently emitted. A single Koa`e `ula was observed flying within the koa`e kea group. Nine Brown Booby were seen flying close to the water’s surface while circling the islet. One Great Frigatebird or `Iwa visited Mokapu in the early evening on both nights of the survey. The authors also observed a Barn Owl hovering over the summit of the island a few hours after sundown. Barn owls have been documented as killing nesting and fledgling sea birds. This is another threat to the native sea birds as well as the rat predation on eggs and new born hatchlings. Table 2. List of Aves observed on or around Mokapu Islet, Molokai Hawaiian Name English Name Scientific Name `A Brown Booby Sula leucogaster plotus `Iwa Great Frigatebird Fregata minor palmerstoni Koa`e Kea White-tailed Tropic Bird Phaethon lepturus dorotheae Koa`e `Ula Red-tailed Tropic Bird Phaethon rubicauda rothschildi `Ua`u Kani Wedgetailed Shearwater Puffins pacificus chlororhynchus Barn Owl Tyto alba Recommendations: The presence of rats has terminated the regeneration of Pritchardia, Pittosporum, and Diospyros along with other native taxa on Mokapu Islet. Rats are notorious for eating the fruit and seeds of plants, and it is recommended that efforts be made to eliminate the rat population for the benefit of nesting seabirds and the regeneration of Hawaiian native plant species. Eradication of Lantana camara, along with all other invasive non-native species should be included in a management plan. There remains patches of significant native plant communities on the island and control of invasive plants would help to stabalize these communities from further decline. Checklist of Vascular Plants Mokapu Island, Molokai, Hawaii K. R. Wood & M. LeGrande [Note: Names for flowering plants follow W. L. Wagner et al. 1990. Names for pteridophytes follow unpublished checklist by W. H. & F. Wagner.] *Native Hawaiian species (endemic/indigenous) represented in bold text Symbols: end=Endemic E=Endangered ind=Indigenous R=Rare nat=Naturalized V=Vulnerable Pol=Polynesian Introduction SIE=Single Island Endemic SPECIES STATUS ANGIOSPERMS-DICOTS Anacardiaceae Schinus terebinthifolius Raddi nat Apiaceae Peucedanum sandwicense Hillebr. end V Araliaceae Reynoldsia sandwicensis A. Gray end R Asteraceae Ageratum conyzoides L. nat Artemisia australis Less. end Melanthera integrifolia (Nutt.) W. L. Wagner & H. Rob. end Pluchea carolinensis (Jacq.) G. Don nat Pseudelephantopus spicatus (Juss. ex Aubl.) Vahl nat Sonchus oleraceus L. nat Brassicaceae Coronopus didymus (L.) Sm. nat Lepidium bidentatum Montin var. o-waihiense (Cham. & Schlechtend.) Fosb. end V Caryophyllaceae Schiedea globosa H. Mann end V Chenopodiaceae Chenopodium oahuense (Meyen) Aellen Convolvulaceae end Ipomoea tuboides Degener & Ooststr. end Crassulaceae Kalanchoë pinnata (Lam.) Pers. nat Ebenaceae Diospyros sandwicensis (A. DC) Fosb. end Euphorbiaceae Chamaesyce celastroides (Boiss.) Croizat & Degener var. amplectens (Sherff) Degener & I. Degener end Fabaceae Senna gaudichaudii (Hook. & Arnott) H. Irwin & Barneby ind Goodeniaceae Scaevola taccada (Gaertn.) Roxb. ind Lamiaceae Plectranthus parviflorus Willd. ind Lauraceae Cassytha filiformis L. ind Malvaceae Abutilon grandifolium (Willd.) Sweet nat Malvastrum coromandelianum (L.) Garcke subsp. coromandelianum nat Sida fallax Walp. ind Piperaceae Peperomia blanda (Jacq.) Kunth var. floribunda (Miq.) H. Huber ind Pittosporaceae Pittosporum halophilum Rock end R Plantaginaceae Plantago lanceolata L. nat Plumbaginaceae Plumbago zeylanica L. ind Portulacaceae Portulaca lutea Sol. ex G. Forster ind Portulaca oleracea L. nat Rosaceae Osteomeles anthyllidifolia (Sm.) Lindl. ind Rubiaceae Morinda citrifolia L. pol Santalaceae Santalum ellipticum Gaud. end Solanaceae Solanum americanum Mill. ind Sterculiaceae Waltheria indica L. ind Urticaceae Pilea peploides (Gaud.) Hook. & Arnott ind Verbenaceae Lantana camara L. nat ANGIOSPERMS-MONOCOTS Arecaceae Pritchardia hillebrandii (Kuntze) Becc. end Cyperaceae Carex wahuensis C.A. Mey. subsp. wahuensis end Cyperus phleoides (Nees ex Kunth) Hillebr. var. phleoides end Liliaceae Dianella sandwicensis Hook. & Arnott ind Poaceae Digitaria insularis (L.) Mez ex Ekman nat Eragrostis variabilis (Gaud.) Steud. end PTERIDOPHYTES Polypodiaceae Phymatosorus grossus (Langsd. & Fisch.) Brownlie nat Pteridaceae Doryopteris decipiens (J. Sm.) Hook. End

June 3, 2011

September 7, 2023