A new species of Dubauatia (Asteraceae-Madiinae) from Kaua'i, Hawaiian Islands

4 Pages·1998·2.7 MB·English

by  G D Carr

A New Species of Dubautia (Asteraceae—Madiinae) from
Kauai, Hawaiian Islands
Gerald I). Carr and David H. Lorenee
Department of Botany, University of Hawaii, 3190 Maile Way, Honolulu, Hawaii 96822 and
National Tropical Botanical Garden, P.0. Box 340, Lawai, Hawaii 96765, U.S.A.
Abstract. Dubautia syndetica G. Carr & Lorenee While synthesis of information regarding com¬
from the Hawaiian Island of Kaua’i is described paratively well-known species of the silversword al¬
and illustrated. The new species is distinguished liance has been tin- focus of several workers, lead¬
from congeners on the basis of its combination of ing held botanists in the Hawaiian Islands continue
uniseriate, somewhat coalescent receptaeular to discover species new to science. A collection in
bracts, coarsely glandular peduncles, glandular co¬ 1985 by Tim Flynn, Curator of the Herbarium at
rolla tubes, and conspicuously strigose achenes. the National Tropical Botanical Garden, first called
These and other features suggest a possible hybrid attention to the species described herein. Flynn’s
origin from D. laxa Hooker & Arnott subsp. hirsuta specimen from the Wahiawa Mountains of Kaua’i
(Hillebrand) G. Carr and I). raillardioides Hille- was thought to represent a single plant growing at
brand.
a single site in the vicinity of Dubautia laxa and
D. raillardioides. For this reason, and because the
The most recent monograph of the Hawaiian en¬ material seemed to combine features of these spe¬
demic genus Dubautia (Carr, 1985) recognized 21 cies, it was annotated by one of us (GDC) as a
species in three sections: Dubautia sect. Dubautia, hybrid. A few years later, field botanists began to
consisting of 10 species of diverse, mostly meso- detect plants with the same unique suite of char¬
phytic shrubs and small trees with 14 pairs of chro¬ acters in other areas of the Wahiawa Mountains,
mosomes; D. sect. Railliardia (Gaudichaud) G. and often not closely associated with other species
Carr, consisting of 10 species of mostly xerophytie of Dubautia. Subsequently, the authors visited the
shrubs and small trees with 13 pairs of chromo¬ site together and found no evidence that these
somes; and D. sect. Venosa-reticulata (A. Gray) G. plants represent primary or recent hybridization.
Carr, comprising a single lianous species with 14 Although we hypothesize a hybrid origin for this
pairs of chromosomes. These species, together with taxon, it appears to be as reproductively stable as
those of th*1 Hawaiian genera Argyroxiphium and any normal sexual species, and therefore worthy of
Wilkesia, constitute the Hawaiian Madiinae (Aster¬ formal recognition.
aceae), a group of 28 morphologically and ecolog¬
ically highly diverse, yet closely related species Dubautia syndetica G. Carr & Lorenee, sp. nov.
otherwise known as the Hawaiian silversword alli¬ TV PE: Hawaiian Islands (U.S.A.). Kaua’i:
ance. This group of plants has been the subject of Koloa District, Lihue-Koloa Forest Reserve,
more than 20 years of intensive experimental stud¬ Wahiawa Stream and Mts. along main Wah¬
ies, including investigations of biosystematics and iawa Stream near headwaters, low wet forest,
cytogenetics (Carr et al., 1989; Kyhos et ah, 1990; 705—710 m, 13 June 1991, I). //. Lorenee, T.
Carr et ah, 1996), flavonoid chemistry (Crins & Flynn, K. Wood & S. Perlman 6782 (holotype,
Hohm, 1990), physiological ecology (Robichaux et BISH; isotypes, F, HAW, MO, NY, PTBG,
ah, 1990), population genetics (Friar et ah, 1996; US). Figure 1.
Witter, 1990; Robichaux et ah, 1997), phytoge¬
\ speeiebus uliis Dubautiae sectionis Dubautiae hrac-
ography (Baldwin & Robichaux, 1995), and molec¬ teis reeeptaculi uniseriatis nonnihil eoalescentibus, pe-
ular systematic^ and evolution (Baldwin et ah, dimculis grosse glandulosis. tubo corollae glanduloso,
1991; Baldwin, 1997). As illuminated by the aelieniis insigniier strigosis differt.
aforementioned experimental studies and the ear¬ Openly branching shrubs 1—2(—3) m tall, vege¬
lier anatomical and morphological observations tative stems glabrous to sparsely hispidulous, most¬
summarized by Carlquist (1970, 1974), the silver- ly pale, gray-brown when dry, the leaf scars mostly
sword alliance provides a premier example of the glabrous; flowering stems usually hispid. Leaves
process of adaptive radiation in plants. opposite, commonly 4-16 cm long, 1-3.5 cm broad,
Nov ON 8: 4-7. 1998.
Volume 8, Number 1 Carr & Lorence 5
1998 Dubautia syndetica from Kaua'i
Figure 1. Dubautia syndetica (>. Carr & Lorence. —A. Habit and habitat of plant on steep bank. Ixtrence ct al. 6/82.
—B. Vegetative and reproductive shoots. Note the short, broad capitulescence. lorence el al. 6782. —C. Leaf, lower
surface. Note 7 acrodromous veins. Morden ct al. 1284. —I). Flowering heads. Note uniseriate, weakly fused peripheral
receptaeular bracts on the head at right, exposed, strigose achenes in the partially dissected head on the left, and
coarse glands on the peduncles. Lorence et al. 6782. —E. Disk corolla. Note the glands in the middle region of the
tube (arrow). Lorence et al. 6782. Bars = 1 cm in C. 1 mm in D, E.
narrowly elliptic to oblanceolate, dark green and the middle, often eiliolate basally; apex acuminate;
sparsely to moderately appressed-hispidulous base attenuate-petioloid; venation ± acrodromous,
above, paler and appressed-hispidulous to some¬ with mostly (5—)7 basal to suprabasal veins. Heads
what more coarsely and spreading-hispid beneath; commonly 10—90, disposed in cymcse-corymbi-
margins shallowly toothed from apex to well below form, sublax capitulescences mostly 2.5-9 cm long
6 Novon
and 3—15 cm broad, the lower peduncles puberu- G. Carr subsp. imbricata, D. lava subsp. hirsuta,
lous to hispid and sparsely glandular, becoming D. paleata A. Gray, D. pauciflorula St. John & G.
more glandular above, the upper and ultimate pe¬ Carr, and D. raillardioides.
duncles often obscured by purplish, sessile to Affinities. This new species belongs to Dubau¬
short-stalked glands, the ultimate peduncles mostly tia sect. Dubautia, characterized by mesomorphic
2-15 mm long; receptacular bracts 6-13, linear to leaves lacking a distinct petiole, blades not visibly
linear-elliptic, linear-lanceolate or rarely linear-ob- reticulate or with areolae obviously longer than
lanceolate, peripheral, uniseriate, weakly and ir¬ broad, and pappus paleae or aristae laciniate-fim-
regularly coalescent (usually partially or wholly briate or minutely ciliate with fimbriae or cilia less
separating on drying), 4.5—7 mm long, usually red¬ than 0.4 mm long. Dubautia syndetica was first
dish purple, often sparsely hispid and glandular, thought to represent an isolated primary hybrid be¬
especially toward the base; Horets usually 8—17, the tween D. laxa subsp. hirsuta and D. raillardioides.
corolla pale greenish yellow, becoming purple in Indeed, several features of the new species suggest
age, 2.2—3.8 mm long, about equaling the pappus, this origin. For example, it combines the pedun¬
sparsely to moderately glandular on the tubular cular glands found in Dubautia raillardioides with
portion, rather abruptly dilated distally, apex with the corolla glands found in D. laxa subsp. hirsuta.
5 triangular lobes, each ca. 0.5 mm long; pappus Other features of Dubautia syndetica, including the
stramineous to pale tan or reddish purple, com¬ color, shape, distribution, texture, and coalescence
prising 16—26 unequal, very narrowly linear-lan¬ of the receptacular bracts, the color and texture of
ceolate, shortly fimbriate aristae 2.2-3.8 mm long; the pappus, the indumentum of the peduncles,
achenes black, straight or only slightly curved, ca. leaves, and achenes, and the general habit of the
2-3 mm long, strigose. plants, also appear to be intermediate to the cor¬
responding features of Dubautia laxa subsp. hirsuta
Distribution. This taxon is known only from the and D. raillardioides.
region of the headwaters of the Wahiawa Stream,
While many features of D. syndetica appear in¬
primarily on adjacent slopes of the Wahiawa Moun¬
termediate to the putative parental species, leaf ve¬
tains draining into the northern end of the Kanaele
nation is very similar to that of D. laxa subsp. hir¬
Swamp basin. The known range is roughly a tri¬
suta, and leaf size (especially on flowering shoots)
angular area approximately defined by Hulua in the
is smaller than might be expected in the hypothe¬
southwest, Kapalaoa in the north, and Kahili in the
sized hybrid combination. In any case, the fre¬
southeast. Populations occur at elevations of ca.
quency and distribution of plants in the field are
680 to 950 m. Based on rather limited phenological
indicative of a reproductively stabilized taxon, not
data, flowering appears to occur primarily from
a series of primary F, hybrids. Thus, formal taxo¬
March to June.
nomic recognition is desirable. The specific epithet,
Habitat. Dubautia syndetica occurs as scat¬ derived from the Greek ovi’Sctikoo- (binding to¬
tered to locally abundant individuals along the gether), recalls the striking combination of features
banks of the upper reaches of the Wahiawa Stream of two other species of Dubautia, and bespeaks the
and its tributaries, and adjacent windward slopes putative hybrid nature of this taxon.
leading to the summit of Kapalaoa. The vegetation
is a low stature, diverse lowland wet forest domi¬ Paratypes. HAWAIIAN ISLANDS (U.S.A.). kaua'i:
Koloa Distric t. Kanaele Swamp drainage, along main fork
nated by Metrosideros polymorpha Gaudichaud, M.
and upper tributaries of Wahiawa Stream to crest of ridge
waialealae (Rock) Rock, Antidesma platyphyllum just SVt of Kapalaoa, 670—975 m, 13 Apr. 1991, Flynn et
H. Mann var. hillebrandii Pax & K. Hoffmann, Sy- al. 4589 (BISH, PTBG), 700 m, 1 June 1995. Morden et
zygium sandwicensis (A. Gray) Niedenzu, Ilex <il. 1880. (BISH), 715 m, 1 June 1995, Carr el al. 1501
(BISH, HAW); Wahiawa Stream drainage, SW of Kapa¬
anomala Hooker & Arnott, Perrottettia sandwicen¬
laoa, 730-850 m, 20 Apr. 1991, Flynn et al. 4625
sis A. Gray, Tetraplasandra spp., Cheirodendron (PTBG); W side of Wahiawa Stream drainage, gulch be¬
spp., and Psychotria spp. with numerous pterido- tween Lone Ixiulu Ridge and LZ1, 700—770 m, 23 July
phytes including Dicranopteris linearis (N. L. Bur- 1991. Wood et at. 1085 (I’TBG); Wahiawa Mis. just NK of
Wahiawa Bog, along main Wahiawa Stream, NW of Ml.
man) Underwood, Diplopterygium pinnatum
Kahili, 630-740 m, 12 Apr. 1988, hirence et al. 5962
(Kunze) Nakai, Athyrium sp., Diplazium sp., Sad- (PTBG); ESE of main Wahiawa Stream heading up 2 un¬
leria spp., and Cibotium spp. Threats include in¬ named gulches to ridge connecting Kahili and Kapalaoa
vasion by alien plant species, notably Psidium cat- Peaks, 29 Jan. 1991, Lorence et al. 6694 (BISH); on wind¬
tleianum Sabine, Melastoma candidum D. Don, and ward side of ridge between Relay Towers and Mt. Kahili,
ca. 685 m. 6 June 1985, Flynn III6 (BISH, PTBG): l.ihue
Rubus rosifolius Smith, and landslides. Associated
District, Kapalaoa Peak, windswept ridge, 915—930 m. 15
Dubautia species include D. imbricata St. John & May 1991, Wood et al. 840-C (ITBG).
Volume 8, Number 1 Carr & Lorence 7
1998 Dubautia syndetica from Kaua'i
Acknowledgments. We would have little to write silversword alliance and North American tarweeds (As¬
teraceae: Heliantheae— Madiinae). Amer. J. Bot. 83:
about if it were not lor tireless botanical explorers
653-660.
who often risk much to bring back interesting new -, R. H. Robichaux, M. S. Witter & I). W. kvhos.
collections. We especially thank Tim Flynn, Steve 1989. Adaptive radiation of the Hawaiian silversword
Perlman, and Ken Wood, who have each contrib¬ alliance (Compositae—Madiinae): A comparison with the
Hawaiian picture-winged Drosophila. Pp. 79-97 in L.
uted to a better understanding of this and many
V. Giddings, k. Y. kaneshiro & W. W. Anderson (edi¬
other Hawaiian plants.
tors), Genetics, Speeiation, and the Founder Principle.
Oxford Univ. Press, New York.
Grins, W. J. & B. A. Bohm. 1990. Flavonoid diversity in
Literature Cited
relation to systematics and evolution of the tarweeds.
Baldwin, B. G. 1997. Adaptive radiation of die Hawaiian Ann. Missouri Bot. Card. 77: 73—83.
silversword alliance: Congruence and conflict of phy¬ Friar, E. A., R. H. Robichaux & 1). W. Mount. 1996. Mo¬
logenetic evidence from molecular and non-molecular lecular genetic variation following a population crash in
investigations. Pp. 103—128 in T. J. Givnish & k. J. the endangered Mauna Kea silversword, Argyroxiphium
Sytsma (editors). Molecular Evolution and Adaptive Ra¬ sandwicense subsp. sandwicense (Asteraceae). Molec.
diation. Cambridge Univ. Press, Cambridge. Fcol. 5: 687-691.
-& R. H. Robichaux. 1995. Historical biogeogra¬ kvhos. D. W., G. I). Carr & B. G. Baldwin. 1990. Biodi¬
phy and ecology of the Hawaiian silversword alliance versity and cytogenetics of the tarweeds (Asteraceae:
(Asteraceae). Pp. 259—287 in Vi. L. Wagner & V. A. Heliantheae—Madiinae). Ann. Missouri Bot. Garcl. 77:
Funk (editors), Hawaiian Biogeography. Smithsonian In¬ 84-95.
stitution Press, Washington, D.C. Robichaux, R. H., F. A. Friar & I). W. Mount. 1997.
-, I). W. kvhos, J. Dvorak & G. I). Carr. 1991. Molecular genetic consequences of a population bottle¬
Chloroplast DNA evidence for a North American origin neck associated with reintroduction of the Mauna kea
of the Hawaiian silversword alliance (Asteraceae). Proc. silversword, Argyroxiphium sandwicense subsp. sand¬
Natl. Acad. U.S.A. 88: 1840-1843. wicense (Asteraceae). Conservation Biol. 11: 1140—
Carlquist, S. 1970. Hawaii, a Natural History. Natural I 146.
History Press, Garden City, New York. -, G. I). Carr. M. Liebman & R. W. Pearcy. 1990.
-. 1974. Island Biology. Columbia Univ. Press, New Adaptive radiation of the Hawaiian silversword alliance
York. (Compositae-Madiinae): Ecological, morphological, and
Carr, G. D. 1985. Monograph of the Hawaiian Madiinae physiological diversity. Ann. Missouri Bot. Card. 77:
(Asteraceae): Argyroxiphium, Dubautia, and Wilkesia. (A-72.
Allertonia 4: 1—123. Witter, M. S. 1990. Evolution in the Madiinae: Evidence
-. B. G. Baldwin & D. W. kvhos. 1990. Cytogenetic- from enzyme electrophoresis. Ann. Missouri Bot. Card.
implications of artificial hybrids between the Hawaiian 77: 110-117.