P1. Syst. Evol. 194: 111- 122 (1995) Plant

Systematics and

Evolution © Springer-Verlag 1995 Printed in Austria

Systematic study of the genus Delilia (Asteraceae, Heliantheae)

PIERO G. DELPRETE

Received March 15, 1994

Key words: Asteraceae, Heliantheae, Delilia. - Taxonomy, weeds. - Flora of Galapagos Islands, Cape Verde Islands.

Abstract: A taxonomic study of the genus Delilia is presented. Two species are recognized: D. bifiora, a widespread weed of tropical and subtropical regions of the New World, extending from Mexico to northern Argentina and recently introduced in the Cape Verde Islands; and D. repens, endemic to the Galapagos islands. A key to the species, illustrations, distribution maps, and complete synonymy are presented.

Nomenclatural history

The genus Delilia was first proposed by SPREN~EL in April of 1823 with the publication of Delilia berteri. It was named in honor of A. DELILE, the French botanist who accompanied NAPOLEON to Egypt and author of Description de l'l~gypt (DELmE 1812). The specific epithet was dedicated to BERTEV~O, an Italian botanist (a young Piedmontise) who first discovered this species in South America, along the river Magdalena in Colombia. BERTERO sent the seeds from this collection to Europe and from these SPRENGEL described D. berteri. In his observations SPREN~EL reported (and illustrated), erroneously, that on the top of each ovary three florets were borne: one female and two hermaphroditic. As a consequence, SPRENGEL believed that Delilia berteri should constitute a new tribe, which he named Synanthae. These errors of observation caused SPRENGEL to ignore the extreme resemblance of his Delilia to Milleria biflora L., the latter described in 1753.

CASS~NI (1824), established the genera Meratia and Elvira, even with the knowl- edge of the existence of the genus Delilia and of SPREN~EL'S erroneous observations. The "excuses" for establishing these genera were explained by CASS~NI as follows, which I have translated and paraphrased from the original as follows:

SPRENGEL dedicated Delilia in honor of the botanist DEULE. BONPLAND (1808: 221--223) also dedicated a generic name in honor of the same botanist, establishing Lilaea (Juncaginaceae). For all the above reasons CASSI~I felt obliged to change the name Delilia to Meratia, in honor of MERAT, a French botanist working on the flora of the surroundings of Paris. CASSIN~ treated Delilia berteri as a synonym of his superfluous Meratia sprengelii, while Milleria biflora was treated as a synonym

112 P.G. DELPRETE:

of his Elvira martyni (which was based upon the type of Milleria biflora!). Milleria, at that time, was recognized by MARTYN as having two species, M. biflora and M. quinqueflora L.

DE CANDOLLE (1836), recognizing the errors made both by SPREN~EL and CASSINI, treated Elvira, Meratia, and Delilia as synonyms of Elvira, disregarding the priority of Delilia.

CHARLES DARWIN, in his famous trip on the Beagle in 1835, made two collections of Delilia on the Galapagos Islands. These were later treated by HOOKER (1845) as belonging to two monotypic new genera: Microcoecia repens and Desmocephalus inelegans (from a single individual).

Finally KUNTZE (1891), recognizing the resemblance of the three taxa and the priority of the name Delilia, provided the three combinations, D. biflora, D. repens, and D. inelegans. Unfortunately KUNTZE misspelled, purposely or otherwise, SPREN- GEL'S Delilia as Delilea. The generic name Elvira was used for almost a century until this oversight was corrected by STUESSY (1975). Delilia is the oldest legitimate name for the taxa concerned and is the correct one.

After detailed study of the three taxa previously proposed, I recognize two species in Delilia: D. biflora and D. repens. Delilia inelegans is treated as an aberrant form of D. repens.

Generic relationships

Delilia (as Elvira) was placed in the tribe Heliantheae subtribe Milleriinae (as "Millerieae") by BENTHAM (1873) where it was positioned between Tetranthus and Lantanopsis, both of the latter occurring in the Caribbean Islands. HOFFMANN (1890) largely followed BENTHAM'S classification, retaining Delilia (as Elvira)in the Millerieae between the same two genera. With the establishment of Synedrellopsis KUNTZE (KUNTZE 1898), DALLA TORRE & HARMS (1900) positioned Delilia between it and Tetranthus, both maintained in the Millerieae.

STUESSY (1977), in his overview of the Millerieae, recognized three groups within the tribe. He positioned Delilia as one of three genera in his group 2: Delilia, Lantaniopsis, and Riencourtia all of these distinguished by their herbaceous habit, tightly packed capitulescences, and heads with single ray florets. He specifically called attention to Delilia biflora as being difficult to position with any degree of certainty since it showed extreme reduction in its floral parts, having only two florets to a head, one a fertile pistillate ray floret, the other a sterile hermaphroditic disk floret. He noted that "whether such reductions (in Delilia and related taxa) indicate common ancestry or convergence needs to be studied more carefully".

ROBINSO~ (1981) drastically revised the tribe Millerieae, restricting this to six genera (Axiniphyllum, Guizotia, Milleria, Rumfordia, Sigesbeckia, and Trigono- spermum). Yet other genera positioned in the tribe by earlier workers were variously redisposed. Delilia itself was positioned in his subtribe Ecliptinae, a very large diverse grouping which by his reckoning contained 64 or more genera, most of these thought to be recognized by a combination of features including stigmatic lines separated and corollas with well defined fibers or fiber-sheath along the coalescent corolla lobes of the throat.

ROmNSON'S positioning of Delilia among the genera of his subtribe Ecliptinae is helpful, for he excluded from this grouping Lantaniopsis, which BENTHAM had

Systematics of Delilia 113

previously related to Delilia. ROBINSON positioned both Tetranthus and Synedrel- lopsis in his subtribe Ecliptinae, along with Delilia, but he merely listed the 64 genera included there in an alphabetical sequence without indication of their phyletic relationships.

As already noted, Delilia has highly reduced capitula and floral features and does not have an obvious resemblance to other genera. Likely candidates for a close relationship, however, are probably to be found among the taxa positioned in ROBINSON'S Ecliptinae. Nevertheless, cpDNA restriction site studies of Delilia and numerous other genera of the tribe Heliantheae, shows that Delilia is not related to any of the subtribal groupings proposed by ROBINSON (KI~ & TURNER, unpubl.). In fact, Delilia is placed in a position phylogenetically coordinate with the entire Heliantheae, including the Eupatorieae. Whether the remote position of Delilia will be maintained when additional DNA is analyzed is uncertain.

Delilia SPRENC., Bull. Sci. Soc. Philom. Paris, ser. 3, 10: 54-55, tab. 2. 1823. Type: Delilia berteri SPREN6. [ = D. biflora (L.) KUNTZE]. Synonymy: =-Elvira CAss., Dict. Sci. Nat. 30: 67. 1824. (nom. superfl., based

on type ofMilleria biflora L.). = Meratia CASS., Dict. Sci. Nat. 30: 65. 1824 (nom. superfl., based on type of Delilia berteri SPREN~.). = Desmocephalum J. D. HooK., Trans. Linn. Soc. London 20: 209. 1847. = Microcoecia J. D. HooK., Trans. Linn. Soc. London 20: 209. 1847.

Annual strigose-tomentose herbs. Stems erect or prostrate, more or less branched from the base; rarely prostrate with adventitious roots at the nodes. Leaves opposite, serrate. Capitulescence of 3-25 heads, axillary or terminal. Involucre flattened, of 3 (4) leaf-like, membranous, trinerved phyllaries, one broad, and two much smaller. Pistillate florets 1-3, the corollas ligulate, yellow (rarely white). Disk florets func- tionally staminate, the ovaries sterile; 1-3(-4) per head, the corollas funnelform- campanulate, 5-lobed, yellow (rarely white). Stamens 5. Style branches fused. Achenes obovoid, striate, black, 1.6-3.0 mm long, compressed, biconvex, the faces with one central ridge on the abaxial side, glabrous or sparsely puberulent; pappus absent. Base chromosome number x = 12 (CAvz 1958-1965; DARLINGTON ~; WYLIE 1955; FEDOROV 1969; MOORE 1970-1974).

Key to the Delilia species

1. Erect herbs with rather stout stems; achene glabrous to puberulent; pistillate flowers 1; staminate flowers 1(-2); largest involucral bracts mostly rounded and cordate at base; pedicel thin and pendulous, 3-Tmm long; Central and South America (introduced in Cape Verde Islands) . . . . . . . . . . . . . . . . . . . . . . . . . . 1. D. biflora

2. Prostrate herbs (rarely erect at the distal portion of the stems) with thin, mostly weak stems; achenes puberulent, pistillate flowers 1-2(-3); staminate flowers 1-2(-3); largest involucral bract mostly bilobed and not cordate at base; pedicel stout and erect, 1-2.5mm long; endemic to Galapagos Islands . . . . . 2. D. repens

1. Delilia billora (L.) KUNTZE, Rev. Gen. 333. 1891. Fig. 1. Basionym: Milleria biflora L. Type: Mexico, "Habitat in Campecia", LINNEtJS 814, date and collector un-

known, Herb. Linn. 1031.4 (LINN, holotype IDC 177.621.I.5).

114 P.G. DELPRETE:

B

I..

Q)

c3

t r a m

Fig. 1. Delilia biflora. Habit (A), head showing the three phyllaries (B), and seed (C); drawn from RZEDOWSVd 17524 (TEX)

Systematics of DeliIia 115

Synonymy: Milleria biflora L., Sp. P1. 919. 1753. -= Elvira martyni CAss., Dict. Sci. Nat. 30: 68. 1824. (nora. superfl.) -Elvirabiflora (L.) DC., Prod. 5: 503. 1836. Type: Mexico, "Habitat in Campecia", LIN~Et:S 814, date and collector unknown, Herb. Linn. 1031.4 (LINN, holotype IDC 177.621.I.5).

Delilia berteri SPREN~., Bull. Sci. Soc. Phitom. Paris, set. 3, 10: 54, tab. 2. 1823. -Mera t ia sprengelii CAss., Dict. Sci. Nat. 30: 66. 1824. (nora. superfl.). Type:

Colombia, Magdalena, "ad tureen S. Magdalenae in America", BERTERO, s.n. (holotype, P).

Annual herb, to 1 m high, commonly branched; the young growth densely strigose, glabrescent with age. Leaves triplinerved, ovate to ovate-lanceolate, acute to acuminate, 2-6(-8) cm long, 1-4(-5) cm wide, membranous, the base rounded or slightly decurrent; petioles 0.5 to 2.0 cm long; blades sparsely strigose above, densely strigose below; the margins serrate to entire (rarely). Capitulescences in both axillary and terminal clusters. Heads 5(-7) mm high, 4-5 mm wide, the larger phyllary 4-5 mm long, 4-5 mm wide, rounded, cordate at base; pedicels rather thin and pendulous (2.5-)3.0-7.0 mm long. Heads with 2 florets, these emergent from the phyllaries at anthesis. Ray fiorets with tubular corolla 1.5-2.0mm high, the ligules ovate, 0.3-0.5 mm long, style branches slightly longer than the ligules. Disk florets yellow, corolla tube 2 .O2.5mm long, glabrous, campanulate-funnelform. Anthers black, subauriculate at base, 0.5-0.7 mm long, including the appendages. Achenes obovoid, 1.6-3.0 mm long, compressed, biconvex, pale brown with a gray- ish sheen, with a central dorsal ridge, glabrous. Chromosome number, 2n = 24.

Ecology and distribution. Delilia biflora is unique in the Asteraceae in having flattened heads usually with one female floret and one to three male florets and three foliose bracts, one large and two small. The florets are barely exserted at anthesis and their corollas vary from yellowish-white to yellow. At maturity the head detaches from the stem as a unit and apparently is wind dispersed, the three bracts acting as wing-like structures for dispersal.

The geographical distribution of D. biflora extends from Mexico southward to northern Argentina (one specimen encountered), and eastward to Brazil. Its alti- tudinal range extends from near sea level to 1700 m. In Mexico, Central America, and in the Andes of South America, D. biflora is present as an understory annual herb, but at higher altitudes it often occurs in sunny open areas (as noted in label data and pers. obs. in the field). In Brazil it is almost always encountered as a weed in cultivated fields.

Delilia biflora has recently been collected in the Cape Verde Islands where it reportedly occurs as a weed in cultivated fields and banana plantations (as noted in label data). The species has been obviously recently introduced (collections were made in 1955-56). Considering its wide distribution in the New World Tropics (from the Tropic of Cancer to the Tropic of Capricorn), once introduced onto the African mainland the species might readily establish itself as a wide-ranging weed.

Representative specimens examined. Mexico: Campeche: 6.5 km from Calakmul, MAR- TINEZ & MARTINEZ 6256 (MO). - Chiapas: Acala, BREEDLOVE 37413 (MO); Mazapa, BREEDLOVE 46146 (NY). - Chihuahua: SW Chihuahua, PALMER 141 (GH, US). - Jalisco: mountain sides near E1 Molino, McVau~r~ 13308 (US). - Michoacan: Morelia, ARSENE 2568 (MO, US). - Morelos: Rocky hills near Yautepec, PRIN~LE 9896 (F, GH, MO, NY, US). - Nayarit: base of Volcan Ceboruco, CRONQUIST 9603 (NY). - Oaxaca: San Ger- onimo, MELL 2121 (NY, US). - San Luis Potosi: limestone hills, Cardenas, PRIN~LE 3287

116 P.G. DELPRETE:

(F, GH, MO, NY, US). - Sinaloa: 20 km E of La Concordia above Copala, BREEDLOVE 35650 (MO). Tabasco: Balancan, MENENDEZ 423 (MO). - Michoacan: Naranjo, HINTON 1980 (MO, NY, US). - Veracruz: Laguna escondida, Tuxtlas, LOT 324 (F, GH, US); Ignacio de la Llave, MARTINEZ CALDERON 1283 (F, GH, MO, NY, US); San Andres, MARTINEZ CALDERON 1717 (F, GH, MO, US); Catemaco, BEAMAN 5477 (F), Sanborn, ORCUTT 3037 (MO, US); Zacuapan, PURPUS 2260 (F, NY, US). - Yucatan: Chichankanab, GAUMER 1711 (F, GH, MO, NY, US).

Belize: Belize city, airstrip, DIECKMAN 166 (MO). - Cayo: Mt Pine Ridge, LIESNER & DWYER 1585 ( M O ) . - Corozal" San Andres, GENTLE 1078 (N-Y). - Stann Creek: beyond Sarawee, GENTLE 7875 (F, GH, NY).

Cuba: Mazanzas: Colon, BAKER 2418 (NY). - Pinar del Rio: Sierra Mendoza, SHAFER 11137 (F, GH, NY). - Santa Clara: Cienfuegos, Cieneguita, COMBS 206 (F, GH, MO, NY, US).

Guatemala: Chiquimula: near Ataluapa, MOLINA & MOLINA 25389 (F, MO, NY). - Huehuetenango: roadside bank of E1 Mono bridge, highway to La Mesilla, MOLINA & MOLINA 26349 (F, MO). - Jalapa: Laguna de Ayarza, HEYDE & Lux 3809 (F, GH, NY, US). - Peten: Dos Lagunas, CONTRERAS 1642 (F). - Santa Rosa: Santarosa, HEYDE & Lux 3158 (F, GH, US).

El Salvador: La Libertad: Finca Santa Maria, W of Santa Tecla, CARLSON 177 (F). - Morazan: ditch leading to reservoir, Montecristo, TUCKER 507 (F, GH, MO, NY, US). - San Salvador: San Salvador, STANDLEY 22711 (GH, MO, US). - Santa Ana: Metapan, STANDLEY & PADILLA 3339 (F). - San Vincente: San Vincente, STANDLEY & PAI)ILLA 3647 (F). - Sonsonate: Armenia, STANDLEY 23484 (US).

Honduras: Comayagua: Comayagua, STANDLEY & CHACON 5500 (F). - Copan: between Hacienda Grande and Ostuman, MOLINA & MOLINA 24743 (F, MO, NY). - Choluteca: Pespire, STANDLEY 27186 (F). - E1 Paraiso: trail to Finca Le Emilia, CARLSSON 2558 (F). - Morazan: Zamorano, WILLIAMS & MOLINA 10192 (F, GH, MO). - Olancho: between San Felipe Catacamas and E1 Plomo, MOLINA 13276 (NY). - Santa Barbara: Los Dragos, on Rio Chamelecon, STANDLEY & LINDELIE 7462 (F).

Nicaragua: Boaco: 2.4 km N of Rio las Canas, STEVENS 5836 (MO). - Carazo: Estacion Biologica Chacocenter, GRIJALVA 4139 (MO). - Chontales: santo Tomas, SEYMOUR 6325 (GN, HY). - Esteli: Santa Cruz, E1 Portillo, MORENO 4556 (MO). - Granada: volcano Mombacho, ATWOOD 3923 (GH). - Leon: Santa Rosa del Penon, MORENO 2461 (MO). - Madriz: Volcan de Somoto, STEVENS 16330 (MO). - Managua: Managua, CROAT 43147 (MO). - Masaya: Parque National Volcan Masaya, NEILL 3079 (MO). - Nueva Segovia: Rio Dipilto, 6km N of Ocotal, NEILL 2150 (MO). - Rivas: Isla Ometepe, Volcan Con- cepcion, ROBLETO 1369 (F).

Costa Riea: Alajuela: riverbank of Rio Poas, BRENES 17332 (NY). - Cartago: Turrialba, LENT 585 (F, MO). - Guanacaste: 5-15 km S of La Cruz, WILLIAMS & al. 26367 (F, NY). - Heredia: 4 km beyond the church in Alajuela, ALMEDA 2392 (F). - Puntarenas: Las Cruces Botanical Garden, CROAT 44459 (MO). - San Jose: San Jose, BURGER 3854 (MO, NY).

Panama: Canal Zone: 1 mi S of Cocoli, WILBUR & al. 12868 (F, GH, MO, NY). - Cocle: E1 Valle de Anton, CROAT ( M O ) . - Chiriqui: road to Rio Serano, FOLSOM & D'ARCY 2105 (MO). - Herrera: 5 km W of turnoff from Highway 105 to Potuga, HAMMEL 5271 (F, MO). - Los Santos: 3 miles S of Carreta, BURCH & al. 1250 (GH, MO). - Panama: Cerro Campana, D'ARcY 9565 (MO). - Veraguas: 1-2 mi above Santa Fe, AL GENTRY 3065 (MO).

Colombia: Antioquia: riverbank of Rio Sucio, GUTIERREZ & BARKLEY 17C482 (F). - Atlantico: between Baranoa and Galapa, DUGAND 5407 (US). - Bolivar: vicinity of Tur- baco, KILLIP & SMITH 14223 (GH, NY, US). - Cundinamarca: Girardot, RUSBY & PENNELL

Systematics of Delilia 117

r ° -~ - . . ~ - - - 7 " ' "

Fig. 2. Distribution of Delilia biflora in America

153 (GH, MO, NY, US). - Huila: hillside above Colombia, FOSBERG 19582 (NY, US). - Valle del Cauca: Hacienda "El Trejo', N of Palmira, GARCIA 6315 (US).

V e n e z u e l a : Anzoategui, Libertad district, road from E1 Vigia to Buenos Aires, DAV1DSE & GONZALES 19754 (MO). - Lara: Palavecino, STEYERMARK ~ al. 103656 (NY, US). - Merida: Estanques, RUIZ-TERAN & LOPEz-FIGUEIRAS 140 (MO, NY, US). - Miranda: Caracas and vicinity, BAILEY & BAILEY 149 (GH, NY, US). - Tachira: along road between San Cristobal and Choro del Indio, CROAT 38449 (MO). - Tragua: Parque National Henry Pittier, MONTALDO 3603 (F). - Trijullo: 1 km after Grupo escolar de Cuicas, BENITEZ DE ROJAS 1013 (F). - Yaracuy: NE of San Felipe, ARISTEGUIETA 1126 (NY). - Zulia: Bolivar, road to E1 Zamuro, BUNTINa 8301 (US).

Eeuador" E10ro: Huaquillas, dry savanna, ASPLUND 15726 (NY). - Guayas: Guayaquil, ASPLUND 15651 (NY); gulf of Guayaquil, MILLE 1139 (F, US). - Loja: Vilcabamba- Yangana, HARLING & ANDERSSON 13620 (MO, US). - Manabi: Bahia de Caraquez, CERON & al. 6717 (MO).

Peril: Cajamarca: La Pena Negra/Chilete-San Pablo, SAGASTEGUI & al. 7926 (GH, MO, NY, US). - Chiclayo: Lambayeque, side road of Panamerican Hiway, LLATAS 616 (F, MO). - Piura: Cabo Blanco, HAUGHT 232 (GH, NY, US). - Tumbez: Tumbez, WEBER- BAUER 7712 (F, GH, US).

Bol iv ia: La Paz: Nor Yungas, Polo-Polo bei Coroico, BUCHTIEN 239 (F, GH, MO, NY). - Santa Cruz: Andres Ibanes, 10 km S of Santa Cruz, BETTELLA 76 (F, NY); Santa Cruz,

118 P.G. DELPRETE:

~ Sto. Antao

S. Vicente ~

16" S

o

1

Fogo

24 ° W

S. Nicolau

Sal

Boa Vista

g?

~ Maio

0 50 100 | | , |

S. Tiago Km

Fig. 3. Distribution of Delilia biflora in the Cape Verde Islands

KUNTZE VI92 (NY, US). - Tarija: Gran Chaco, 10 km S of Palmar Grande, road from Yacuiba to Villa Montes, KRAPOVICKAS ~; SCHININI 31097 (F). - Yungas: Yungas, without collector 502 (F, GH, MO, NY).

Argentina: Jujuy, Dique la Cienega, CABRERA & al. 14090 (GH). Brazil" Bahia, islets and banks of the Rio Corrente by Correntina, HARLEY 21629 (K,

NY, US); Cachoeira, Valley between the two rivers Paraguacu e Jacuipe, CAVAt~O 368 (US). - Brasilia: KLAXT, s.n. (GH). - Ceara: Serra de Baturite, ULE 9068 (US). Maranhao: Loreto, between the Rios Balsas and Parnaiba, EITEN & EITEN 3951 (NY, US); - Per- nambuco: Tapera, PICKEL, s.n. (US). - Rio de Janeiro: Jacarepagua, MOREIRA 86017 (US).

Cape Verde Islands (Arquipelgao de Cabo Verde): Santiago Island: Posto Agricola de S. Jorge, in eucaliptus plantation, BARBOSA 5859 (MO); Portal, in cultivated fields, BARBOSA 5968 (MO); Monte de Boa Entrada, weed in rice and millet cultivations, BARBOSA 6145 (MO). - Sao Nicolau Island, ribeira da Queimada, weed in banana plantation, BARBOSA 7305 (MO).

2. Delilia repens (3. D. HooK.) KUNXZE, Rev. Gen. P1. 1: 333. 1891. Fig. 2. Basionym: Microcoecia repens J. D. HOOK. Type: James Island. Oct. 1835. DARWIN, s.n. (holotype, K; GH-photo[). Synonymy: Microcoecia repens J. D. HooK., Proc. Linn. Soc. 1: 277. 1845.

=Elvira repens (J. D. HOOK.) B. L. ROB., Proc. Amer. Acad. Arts 38: 212. 1902. Type: James Island. Oct. 1835. DAV, W~N, s.n. (holotype, K; GH-photo!).

Desmocephalum inelegans J. D. HooK., Proc. Linn. Soc. 1: 277. 1845. =-Delilia inelegans (J. D. HooK.) KUNTZE, Rev. Gen. P1. 1: 333. 1891. =-Elvira inelegans

Systematics of Delilia 119

0

James

(Indefatigable)

Ecuato r

arrington ~ ~ n Cnstoba CSanta Fe) 1 (Chatam)

0 10 20 30 40 50 Mitre I , r , , • ' I 0 20 40 ~0 80 Km

Floreana Hood (Charles,Santa Maria) (Espanola)

Fig. 4. Delilia repens. Habit (A) and head showing the three phyllaries (B); drawn from HOWELL 9635 (GH)

(J. D. HOOK.) B. L. ROB., Proc. Amer. Acad. Arts 38: 212. 1902. Type: Charles Island, Oct 1835. DARWIN, s.n. (holotype, K; GH-photo!).

Elvira atripliciformis HOWELL, Proc. Calif. Acad. Sci. IV, 21: 333. 1935. Type: in sandy soil near the beach, James Bay, James Island, 4 Jun. 1932. HOWELL 9635 (holotype, CAS, N. 220339; isotypes, GH!, US!).

Spreading or sprawling herbs, distal portion of stems rarely ascending, readily rooting at lower nodes. Leaves triplinerved, ovate, 0.5-3(-7) cm long, 0.4-1.5 (-3.0) cm wide, membranous, the base rounded or slightly decurrent; petioles 2- 10ram long; blades sparsely strigose above, densely strigose below; the margins serrate. Capitulescence axillary and sparse, mostly of few to several subsessile heads. Heads 3-4 mm high, 3-8 mm wide; the phyllary 4-5 mm long, 3-8 mm wide, usually bilobed and reniform, not cordate at base; pedicels rather stout and erect, 1.0- 2.5 mm long. Heads with 1-2(-3) pistillate flowers and 1-2(--3) staminate flowers, these emergent from the phyllaries at anthesis. Ray florets with tubular corolla 1.5-2.0mm high, yellow to white, the ligules bidentate; disk florets 2mm high, whitish, glabrous to puberulent, campanulate; anthers black, tails absent, 0.4- 0.Tmm long. Achene obovoid, 2-3 mm long, pale brown, subtriangular in cross

120 P.G. DELPRETE:

2ram

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Fig. 5. Distribution of DeIilia repens in the Galapagos Islands

section, laterally compressed, with few short hairs at the apex. Chromosome number unknown.

Representative specimens examined. Ecuador: Galapagos Islands: Isabela (Albermarle) Island: inside of the caldera of Alcedo at the NE side, VAN DER WERFF 1905 (MO); Tagus Cove Mt, HOWELL 9569 (NY, US), SNODaRASS 880 (GH). - Santa Cruz (Indefatigable)

Systematics of Delilia 121

Island: Mt Crocker, HOWELL 9256 (NY, US); in Scalesia forest near the craters past Santa Rosa, VAN DER WERFV 1296 (MO). - James (Santiago) Island: James Bay, HOWELL 9635 (aN, US).

This taxon is endemic to Galapagos Islands. It occurs as both prostrate and semi-ascending growth forms, and the size of its leaves is rather variable. Elvira atripliciformis is a form of Delilia repens with unusually large leaves. Another vigorous growth form from the Galapagos Islands has been identified by VAN DEe WERFF (1905 by annotation) as D. biflora. A careful examination of the specimen concerned shows that the heads actually include one pistillate flower and two staminate flowers, the stem is also rather weak and faintly rooting at the lower nodes. No specimens of D. biflora to my knowledge has been collected from the Galapagos Islands, although its chance introduction in recent years need not to be ruled out.

Delilia inelegans is an anomalous specimen having a congested capitulescence, profuse pubescence and long serrated-leaves. HOOKER (1845) reported (and this is confirmed by his drawings) that the individual concerned has heads with 3 female ligulate florets and few masculine tubular florets (a unique set of characters). I consider this individual as an aberrant form of D. repens since the number of heads per capitulescence, the number of florets per head, and the habit of D. repens are rather variable. Delilia repens is probably a rather recent arrival on the Galapagos Islands, there being little else to distinguish the archipelago populations from mainland D. biflora except habit and involucral bracts. The speciation events of the flora and fauna of the Galapagos Islands are famous among biologists and such instable variation has been previously observed in other founder taxa in the process of adaptive radiation to such habitats.

This study is based on extensive field work in tropical America and examination of 760 herbarium sheets from the following institutions (number of sheets shown in parenthesis): F (181), G (102), LL (27), MO (179), NY (129), TEX (29), US (113). While only repre- sentative specimens are cited in this study, distribution maps were constructed from all of the sheets concerned. I am grateful to the Directors and staff of each for the loan of the material. The staff of the Laboratoire de Phan6rogamie, Museum National d'Histoire Naturelle of Paris (P) kindly sent photocopies of the original description of DeliIia by SPRENGEL (1823). I am particularly grateful to BILLIE TURNER for his skilled supervision of my work and his endless patience in proofreading my exotic English.

References

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Address of the author: PIERO G. DELPREXE, Department of Botany, University of Texas, TX 78713, USA.

Accepted April 22, 1994 by B. L. TURNER

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