Nyssa talamancana Hammel & N.Zamora
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Authority
Hammel, Barry E. & Zamora Villalobos, Nelson A. 1990. Nyssa talamancana (Cornaceae), an Addition to the Remnant Laurasian Tertiary Flora ofSouthern Central America. Brittonia. 42 (3): 165-170.
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Family
Nyssaceae
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Scientific Name
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Description
Species Description - Dioecious trees to 40 m tall and 1.25 m diam, the bark with longitudinal fissures forming plates of ca 4 x 10 cm; branching sympodial with leaves clustered at the tips of branches. Mature leaf blades oblanceolate, (12) 16-25 (27) cm long, 4.5- 11 cm wide, slightly coriaceous, entire; petiole 0.8-1.5 cm long; lateral nerves 12- 18; new developing leaves densely covered with short, silvery pubescence of simple trichomes, the older leaves sparsely pubescent. Inflorescences axillary, usually solitary, pedunculate, with 2 foliose bracts borne distally on the peduncle; sta- minate inflorescence globose, ca 1-1.5 cm in diam (not including expanded sta- mens), the peduncle 1-3.2 cm long; flowers sessile, in 10-12 pairs, each pair subtended by 2, opposite, broadly ovoid bracts with hyaline, ciliate margins and a thick center, each flower subtended by 2 opposite, more or less elliptic, con- duplicate bracts with hyaline, ciliate margins, flowers funnel-shaped, ca 3.2-4 mm long, 2-2.4 mm wide (not including stamens or petals), the 5 (6) green petals imbricate, broadly ovate, 2.6-3.4 mm long, 1.5-2.1 mm wide, the tip rolled under at anthesis; sepals 5, hyaline and ciliate, much smaller than the petals, shallowly rounded and about as wide as long or wider, 0.6-0.7 mm long, 0.6-1.2 mm wide; stamens ca 10, the filaments 2.9-3.7 mm long, anthers dorsifixed, sagittate with the 4 sacs divergent basally, ca 0.8 mm long, 0.8 mm wide; pistillode a low, capitate disc about as wide as the flower. Pistillate inflorescence with a single flower, the peduncle 1-3 cm long; flower sessile, subtended by 4 broadly rounded, decussate bracts, the lower 2 fused where they meet, bracts and flower then subtended by a short (ca 1.5 mm) knobby region of indeterminate structures (reduced inflorescence branches), the flower subcylindrical, at anthesis ca 7 mm long, 4 mm wide, petals and sepals as in the staminate flowers but slightly wider; stamens as in the staminate flowers but about half as long; style ca 4 mm long, the stigma 2- or 3-lobed, 2 larger and papillate, the third from lower on the style, smaller and not papillate; ovary with 2 locules and 1 pendulous ovule each. Mature fruits narrowly ellipsoid, mostly about 5 cm long, 2.5 cm wide, red with yellow, juicy flesh that is acidic and slightly bittersweet; mature endocarps very hard, woody, mostly 3.7-5.2 (5.5) cm long, 1.6-2.2 cm wide; cross section of the en- docarp more or less triangular or trapezoidal and showing 9-12 fiber-filled lon- gitudinal grooves alternating with as many low, rounded ridges; germination valves more or less triangular, 1.3-1.9 cm long, 0.8-1.25 cm wide, 0.5-0.7 cm thick, usually 2 or 3 (4) but only 1 (2) developing seed.
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Discussion
A congeneribus fructibus permagnis, endocarpio 3.7-5.2 (5.5) cm longo, 1.6-2.2 cm lato, recedit
TYPE: COSTA RICA. LIMON: Reserva Biologica Hitoy-Cerere, cabecera del Rio Hitoy, bosque primario en la cima del Cerro Bit'arkara, 9?38'30"N, 83º08'30"W, 1025 m; arbol femenino de 35 m x 100 cm DAP; flores solitanrias, verdes; estambres blancos, 5 largos y 5 mas cortos; frutos recogidos del suelo, la mayoria abierto por roedores y sin semilla, ninguno visto germinando; 3 Sep 1989 (fl, fr), B. Hammel, A. Chacon & G. Herrera 17687 (HOLOTYPE: CR; ISOTYPES: BM, COL, F, MEXU, MO, NY, PE, OSA, US).
Additional specimens examined: COSTA RICA. LIM6N: Reserva Indigena Talamanca, Fila Tsiura- beta, 700 m, 9 Jul 1989 (fr), Hammel & F. Corrales 17613 (CR); 800 m, 13 Jul 1989 (fl & fr), A. Chac6n & G. Herrera 170 (CR, MO, NY, 4 duplicates to be distributed); fl (staminate) 170a (CR, MO, NY, 6 duplicates to be distributed); Reserva Biol6gica Hitoy-Cerere, Cerro Bitarkara, 1025 m, 3 Sep 1989 (fl-staminate), Hammel et al. 17686 (CR, MO, NY, US, 7 duplicates to be distributed); 17689 (CR, MO, NY, US, 19 duplicates to be distributed). PANAMA. BocAs DEL TORO: continental divide between Gualaca & Chiriqui Grande, 900 m, 8 Mar 1986 (fl-staminate), Hammel et al. 14683 (MO, PA, US); (fl, fr), 14684 (MO, NY, PA, US, 3 duplicates to be distributed).
History of discovery. Although fallen fruits of Nyssa talamancana may have been identified as belonging to Icacinaceae for the Flora of Panama (Gentry, pers. comm.), the oldest collections we know of are from 1986. These remained, after preliminary examination at the Missouri Botanical Garden, tentatively identified as Icacinaceae until subsequent discovery of the same taxon in adjacent Costa Rica stimulated further study. Our most useful clue to placing the material to family was the character of dioecy. Among families first considered likely, i.e., Cornaceae, Humiriaceae, Icacinaceae, and Symplocaceae, only Cornaceae and Icacinaceae have dioecious genera. From there we leapt to Nyssa, the only dioecious American Cornaceae (sensu Eyde, 1988). We eliminated Icacinaceae for their superior ovary and confirmed that the unknown had other floral characters concordant with Cornaceae and more precisely with Nyssa
Phenology. -By all indications the species flowers and fruits throughout most, if not all, of the year. Populations observed in early March and early September, as well as in between, had individuals in every stage of maturity, from young bud to mature fruit. At the type locality between 30 and 40 apparently mature, fallen fruits were collected. Under female trees the forest floor was littered with fruits, in various stages of decay as well as fresh and untouched. The majority of en- docarps examined had been chewed into, presumably by rodents, and the seed removed. Most remarkably, a careful search of the area beneath and near several very large female trees revealed neither seedlings nor germinated seeds. Nor did we find any small individuals in the area.
Germination. -An attempt to germinate seeds from the 30 to 40 fruits resulted in only one success. At first several methods of scarification and heat treatment were tried but later we simply pried open the germination valves. In fact, only one viable seed was found; locules in all other endocarps were either empty or the seed was damaged or aborted. Germination is epigeal; over a period of about three weeks the root slowly emerges from the valve, curves downward and the hypocotyl turns green and greatly elongates while the cotyledons are still held within the endocarp. As the now curved hypocotyl elongates, the valve end of the heavy endocarp is lifted upward and the cotyledons begin to pull out. The fully expanded cotyledons are narrowly lanceolate and entire with a pair of long arching lateral veins arising from the base. The first leaves after the cotyledons are distinctly toothed.
Relationships and distribution. -Placement of this material among the nyssoid Cornaceae depends primarily on the unisexual flowers, and we place it in Nyssa (as opposed to Camptotheca or Davidia, both monoecious) on the assumption that dioecy is a synapomorphy for Nyssa (see Eyde, 1988). Other characters pentamerous flowers, solitary pistillate flowers, lobed styles, two or three chambered endocarps and alternate leaves, though arguably primitive in the family are also concordant with placement in Nyssa (Eyde, 1963, 1988; Eyde & Barghoorn, 1963).
Nyssa has often been treated in its own family, Nyssaceae, but is now considered a member of the Cornaceae (Eyde, 1988). Two species occur in Southeast Asia and three to five in North America, one of them extending into Mexico. The species described here is the first record of the nyssoid Cornaceae south of Mexico. Garrya (also dioecious but with racemose inflorescences and opposite leaves) is related to Cornaceae but in its own family (Eyde, 1988). Thus Cornus itself is the only other genus of Cornaceae found in southern Central America.
The new species of Nyssa differs from Cornus of Costa Rica and Panama by dioecious rather than hermaphroditic nature, by solitary (and much larger) rather than clustered fruits, by ten rather than four or five stamens, and from the most common species, C. disciflora DC., by alternate rather than opposite leaves
Among other species of Nyssa, N. talamancana may be closest to N. ogeche Marshall (extant, southeastern U.S.) and N. lescurii (C. H. Hitchcock) Perkins (fossil, eastern U.S.). Eyde and Barghoorn (1963) discussed the possible relationship of N. ogeche with N. lescurii, based on the distribution of tracheid bundles in the endocarp and, more specifically, on the conical projection at the apex of the endocarp. Nyssa talamancana displays the same distribution of bundles be- tween ridges and the same conical projection as the two mentioned species.
The specific epithet refers to the Cordillera de Talamanca, which forms the continental divide in the parts of Costa Rica and Panama where the species has been discovered. The common name in the Bribri indian language, as reported by informants in Costa Rica, is "Buesibo." The Bribri indians claim that the fruit is preferred food of the great curassow (Crax rubra).
Biogeography. -Relationships of the southern Central American flora are most often discussed in terms of the predominantly South American affinities (Gentry, 1982a; Grayum & Churchill, 1987; Hammel, 1986; Standley, 1937). However, some recent discoveries bring attention, rather spectacularly, to the occurrence of northern (i.e., Laurasian) taxa among upland tropical forests. Examples include 1) a trigonobalanoid taxon of Fagaceae from Colombia (see, e.g., Crepet & Nixon, 1989; Van der Hammen & Cleef, 1983), 2) Matudaea, a genus of Hamamelidaceae previously thought endemic to Central America but recently discovered in Colombia (Gentry, pers. comm.), 3) Ticodendron from Central America, apparently a new family related to the higher Hamamelideae (Gomez-Laurito & Gomez, 1989), and 4) the species of Nyssa described here. These taxa are relicts from the once wide-spread northern Tertiary flora, many members of which migrated southward or downward as a result of Pleistocene climatic changes and moved through Central America into South America, in concordance with climatic and orogenic changes, somewhere around three or six million years ago (Gentry, 1982b; Raven & Axelrod, 1974; Toledo, 1982; Van der Hammen & Cleef, 1983).
The lowlands of southern Central America are now dominated by tropical South American taxa that presumably immigrated in the Pleistocene (Gentry, 1982b), whereas the highlands are dominated by Laurasian elements, also of relatively recent origin (Gentry, 1982b; Rich & Rich, 1983). However, the flora of middle elevations in Central America has not been so swamped by tropical South Amer- ican elements and the Laurasian relicts- some of them endemic or nearly endemic genera-appear to be much older than those of higher elevations. We suggest that a careful phytogeographical analysis of the wet mid-elevation flora of southern Central America, where Nyssa talamancana grows in association with genera such as Ticodendron, Alfaroa, Oreomunnea, Beilschmiedia, and Gordonia can help to give us a picture of the composition of the really ancient flora of that region.
The discovery of Nyssa talamancana is especially exciting in view of the fact that Nyssa "has one of the best fossil records of any modern genus of trees" (Eyde, 1963). Although we have not done the detailed analysis necessary to claim "living fossil" status for the new species, we find that in size, number of germination valves, and surface-sculpturing, the endocarps of the new species do resemble those of the fossil assemblage more than those of the other living species. Exploration of extant forests, as well as paleobotanical exploration, can extend our knowledge of their components into the past.