Biosystematics of Tetraploid Eucharis (Amaryllidaceae)

Abstract

Eucharis is a genus of 16 species of petiolate-leaved, neotropical Amaryllidaceae restricted to rainforest understory from Guatemala to Bolivia. The two northernmost species, E. bonplandil and E. bouchei, are the only two tetraploid (2n = 92) species so far known in the genus. Eucharis bonplandil is known from only a few localities in central Colombia. Eucharis bouchei, restricted to Central America, is particularly polymorphic and three varieties are recognized largely on the basis of staminal cup morphology. Data from phenetic, chromosomal, and preliminary electrophoretic analyses are presented for both tetraploid species. On the basis of 17 floral characters, the three varieties of E. bouchei do not resolve into discrete phenetic groups. The tetraploid representatives of Eucharis exhibit a wide degree of karyotypic heteromorphism. Eucharis bouchei var. dressleri is an unstable tetraploid. Electrophoretic banding patterns for aspartate-amino-transferase exhibit additive effects of polyploidy in some individuals. Isozyme phenotypes of Eucharis bouchei var. bouchei are quite variable and cladistic analysis of the isozyme data suggests that this variety may be polyphyletic. Eucharis bonplandii and E. bouchei may be monophyletic sister taxa and the remnants of a once more widespread tetraploid complex. The entry of Eucharis into Central America was probably a geologically recent event. It is hypothesized that E. bouchei has been steadily migrating away from the Colombian border. Eucharis bouchei is a semi-species complex of geographically isolated populations in the process of morphological diversification. The evolution of E. bouchei var. dressleri may be a sympatric speciation event. Founder effects, rapid chromosomal change, and geographical isolation are considered the most important factors in the evolution of the E. bouchei complex. Tetraploidy and attendant increased levels of heterozygosity may have been important in facilitating the migration of Eucharis across the Isthmus of Panama. The genus Eucharis Planchon & Linden [Amaryllidaceae infrafamily Pancratioidinae sensu Traub (1957, 1963)] consists of 16 species of rare, petiolate-leaved, bulbous geophytes inhabiting the understory of primary rainforest from Guatemala to Bolivia (Meerow, 1986). Most of the species are found in the western Amazon basin and adjacent slopes of the eastern Andes. Eucharis bouchei Woodson & Allen is a highly polymorphic tetraploid (2n = 92) complex of Central America (Fig. 1). The species is concentrated in Panama (Fig. 2), but has also been recorded from Costa Rica and Guatemala. Eucharis bouchei is the northernmost species of Eucharis and the only one found north of the Dari6n Gap. It is also the most variable species in the genus, in characteristics that elsewhere justify specific delimitation. Patterns of variation in floral size and tube and limb habit form a complete mosaic throughout the range of E. bouchei, showing little or no geographic consistency. In my recent monograph of Eucharis (Meerow, 1986), three varieties are recognized chiefly on the basis of staminal cup morphology (Fig. 3): E. bouchei var. bouchei, var. darienensis Meerow, and var. dressleri Meerow. Variety bouchei, most common around El Valle de Ant6n in Cocl& Province (Fig. 2), is recognized by its largely edentate staminal cup in which the trapezoidal free filament is not markedly constricted distally into a narrow subulate portion (Figs. LC, 3A, B). It is the most variable of the three varieties, both in flower size and staminal cup morphology. The staminal cup of variety ' I thank Robert Dressler, Mark Elliot, Mark Whitten, and Huntington Botanical Garden for providing living material of tetraploid Eucharis species. Bijan Dehgan provided the supportive environment where this work was accomplished. Charles Guy gave freely of his time and laboratory materials for the electrophoretic analyses. Bart Schutzman aided with computer applications. Brent Mishler suggested the cladistic analysis. Peter Goldblatt, George K. Rogers, and two anonymous reviewers provided useful criticism of an earlier version of this paper. Part of this work was supported by NSF Doctoral Dissertation Grant BSR-8401208 and a Garden Club of America/World Wildlife Fund Fellowship in Tropical Botany. Portions of this paper represent part of a doctoral dissertation submitted to the Graduate School of the University of Florida in partial fulfillment of the requirements for the degree of Doctor of Philososphy. Florida Agricultural Experiment Station Journal Series No. 7537. 2 Horticultural Systematics Laboratory, Department of Ornamental Horticulture, University of Florida, Gainesville, Florida 3261 1, U.S.A. ANN. MISSOURI BOT. GARD. 74: 291-309. 1987. This content downloaded from 157.55.39.177 on Tue, 15 Nov 2016 03:59:12 UTC All use subject to http://about.jstor.org/terms 292 ANNALS OF THE MISSOURI BOTANICAL GARDEN [VOL. 74