Monographs Details:
Authority:
Luteyn, James L., et al. 1995. Ericaceae, Part II. The Superior-Ovaried Genera (Monotropoideae, Pyroloideae, Rhododendroideae, and Vaccinioideae P.P.). Fl. Neotrop. Monogr. 66: 560. (Published by NYBG Press)
Luteyn, James L., et al. 1995. Ericaceae, Part II. The Superior-Ovaried Genera (Monotropoideae, Pyroloideae, Rhododendroideae, and Vaccinioideae P.P.). Fl. Neotrop. Monogr. 66: 560. (Published by NYBG Press)
Family:
Ericaceae
Ericaceae
Synonyms:
Andromeda pubescens Poir., Andromeda rubiginosa Pers., Xolisma rubiginosa Small
Andromeda pubescens Poir., Andromeda rubiginosa Pers., Xolisma rubiginosa Small
Description:
Species Description - Evergreen shrub to small tree to 4 m tall; twigs ± moderately angled, slender, sparsely lepidote, otherwise sparsely to densely pubescent; buds ovoid, 1-2 × 0.7-1.3 mm. Leaf blades elliptic to ovate, 2-8 × 0.9-4.2 cm, ± flat to slightly abaxially curved, coriaceous, ca. 0.3-0.47 mm thick; base cuneate to rounded; apex acuminate to acute, rounded, or truncate; margin plane to slightly revolute, the apical portion obscurely and irregularly toothed to entire, the basal portion entire to sinuous; venation brochidodromous, 3° veins ± reticulate; adaxial surface lepidote but scales usually quickly deciduous, sparsely to densely pubescent on midvein, especially basal portion, the 3° and higher-order veins usually visible, the 2° veins visible, usually not depressed; abaxial surface moderately lepidote, otherwise glabrous to densely pubescent, but usually at least some leaves of shoot with unicellular hairs, the 3° and higher-order veins obscure to very slightly raised, not forming dense, fine, raised network, the 2° obscure to slightly raised and visible; scales rust colored, persistent to deciduous, ca. 0.1-0.25 mm in diam., erose to entire; petiole 3-10 mm long, lepidote, otherwise pubescent adaxially or all around; flower buds ± intermixed with vegetative buds. Inflorescences fasciculate, 4-15-flowered; pedicels clearly articulated with calyx, slender, 4-8.5 mm long, lepidote, otherwise sparsely to densely pubescent; bracts ± opposite, basal or nearly so, narrowly triangular, 0.7-1.6 mm long; floral bracts to ca. 2 mm long. Flowers 5-6-merous; calyx lobes triangular, with acuminate apices, 1-2 × 0.7-1.5 mm, adaxial side glabrous or sparsely pubescent, especially near apex, abaxial side lepidote, otherwise glabrous to sparsely pubescent; corolla cylindrical, white (pink tinged toward mouth), 5-8 × 3.5-5 mm, abaxially sparsely lepidote; filaments roughened, 3-5 mm long, unappendaged or with very small spurs near anther-filament junction; anthers 11.8 mm long; ovary lepidote, otherwise pubescent, placentae ± subapical. Capsules ellipsoid to ovoid, 4-6.5 × 3.5-6 mm, slightly lepidote, otherwise sparsely pubescent, especially near base, the pale, very thick sutures separating as unit from adjacent valves; seeds 1.5-3 mm long.
Species Description - Evergreen shrub to small tree to 4 m tall; twigs ± moderately angled, slender, sparsely lepidote, otherwise sparsely to densely pubescent; buds ovoid, 1-2 × 0.7-1.3 mm. Leaf blades elliptic to ovate, 2-8 × 0.9-4.2 cm, ± flat to slightly abaxially curved, coriaceous, ca. 0.3-0.47 mm thick; base cuneate to rounded; apex acuminate to acute, rounded, or truncate; margin plane to slightly revolute, the apical portion obscurely and irregularly toothed to entire, the basal portion entire to sinuous; venation brochidodromous, 3° veins ± reticulate; adaxial surface lepidote but scales usually quickly deciduous, sparsely to densely pubescent on midvein, especially basal portion, the 3° and higher-order veins usually visible, the 2° veins visible, usually not depressed; abaxial surface moderately lepidote, otherwise glabrous to densely pubescent, but usually at least some leaves of shoot with unicellular hairs, the 3° and higher-order veins obscure to very slightly raised, not forming dense, fine, raised network, the 2° obscure to slightly raised and visible; scales rust colored, persistent to deciduous, ca. 0.1-0.25 mm in diam., erose to entire; petiole 3-10 mm long, lepidote, otherwise pubescent adaxially or all around; flower buds ± intermixed with vegetative buds. Inflorescences fasciculate, 4-15-flowered; pedicels clearly articulated with calyx, slender, 4-8.5 mm long, lepidote, otherwise sparsely to densely pubescent; bracts ± opposite, basal or nearly so, narrowly triangular, 0.7-1.6 mm long; floral bracts to ca. 2 mm long. Flowers 5-6-merous; calyx lobes triangular, with acuminate apices, 1-2 × 0.7-1.5 mm, adaxial side glabrous or sparsely pubescent, especially near apex, abaxial side lepidote, otherwise glabrous to sparsely pubescent; corolla cylindrical, white (pink tinged toward mouth), 5-8 × 3.5-5 mm, abaxially sparsely lepidote; filaments roughened, 3-5 mm long, unappendaged or with very small spurs near anther-filament junction; anthers 11.8 mm long; ovary lepidote, otherwise pubescent, placentae ± subapical. Capsules ellipsoid to ovoid, 4-6.5 × 3.5-6 mm, slightly lepidote, otherwise sparsely pubescent, especially near base, the pale, very thick sutures separating as unit from adjacent valves; seeds 1.5-3 mm long.
Discussion:
The phylogenetic position of this geographically isolated species is somewhat problematic, but Lyonia rubiginosa may be closest to L. truncata, L. stahlii, and L. tuerckheimii. Lyonia rubiginosa differs from L. truncata in its often acuminate-tipped leaves that are more prominently reticulate-veined and often less densely pubescent on the abaxial surface, and its slightly larger capsules. It is separable from L. stahlii by its leaves that are frequently at least slightly pubescent on the abaxial surface, its often slightly larger flowers and fruits, and its often more pubescent twigs. It is separable from L. tuerckheimii by its often abaxially pubescent laminae, thinner stems that are nearly glabrous to only sparsely pubescent, and often smaller, 5- and/or 4-valved capsules (see key). Lyonia rubiginosa was one of the earliest West Indian lyonias to be described, but this species has not been collected since 1887. I could not find it either in the hills above Bolongo or on the other, slightly higher hills of St. Thomas, and it is very possible that the species is extinct. Although this taxons variability is not well known, the limited material available suggests that it is especially great with respect to leaf size, marginal dentation, and pubescence. It is noteworthy that some collections of this entity lack unicellular hairs on the abaxial leaf surface and are quite similar to L. stahlii, while other individuals have a very sparse to dense covering of unicellular hairs on their abaxial leaf surfaces and are thus easily confused with L. truncata. Results of a cladistic analysis of the genus (see "Infrageneric Relationships") suggest that L. rubiginosa is a basal species within the Caribbean complex of Lyonia sect. Lyonia. The presence of abaxially pubescent leaves may indicate that the species is a basal member of the clade including L. truncata. Alternatively, L. rubiginosa could have acquired abaxially pubescent leaves independently, as has undoubtedly occurred in those species of continental North America and Cuba that have such leaves. More collections of this poorly understood taxon would certainly aid in determining its phylogenetic position. In Judd (1981) this taxon was considered conspecific with L. stahlii (vars. costata and stahlii, of Hispaniola and Puerto Rico, respectively) because of their phenetic similarity. The St. Thomas populations, however, are here treated as a distinct species because these populations apparently share no unique apomorphic features with L. stahlii. A broadly circumscribed L. rubiginosa (including L. stahlii) would be extremely paraphyletic (see Figs. 2 & 3).
The phylogenetic position of this geographically isolated species is somewhat problematic, but Lyonia rubiginosa may be closest to L. truncata, L. stahlii, and L. tuerckheimii. Lyonia rubiginosa differs from L. truncata in its often acuminate-tipped leaves that are more prominently reticulate-veined and often less densely pubescent on the abaxial surface, and its slightly larger capsules. It is separable from L. stahlii by its leaves that are frequently at least slightly pubescent on the abaxial surface, its often slightly larger flowers and fruits, and its often more pubescent twigs. It is separable from L. tuerckheimii by its often abaxially pubescent laminae, thinner stems that are nearly glabrous to only sparsely pubescent, and often smaller, 5- and/or 4-valved capsules (see key). Lyonia rubiginosa was one of the earliest West Indian lyonias to be described, but this species has not been collected since 1887. I could not find it either in the hills above Bolongo or on the other, slightly higher hills of St. Thomas, and it is very possible that the species is extinct. Although this taxons variability is not well known, the limited material available suggests that it is especially great with respect to leaf size, marginal dentation, and pubescence. It is noteworthy that some collections of this entity lack unicellular hairs on the abaxial leaf surface and are quite similar to L. stahlii, while other individuals have a very sparse to dense covering of unicellular hairs on their abaxial leaf surfaces and are thus easily confused with L. truncata. Results of a cladistic analysis of the genus (see "Infrageneric Relationships") suggest that L. rubiginosa is a basal species within the Caribbean complex of Lyonia sect. Lyonia. The presence of abaxially pubescent leaves may indicate that the species is a basal member of the clade including L. truncata. Alternatively, L. rubiginosa could have acquired abaxially pubescent leaves independently, as has undoubtedly occurred in those species of continental North America and Cuba that have such leaves. More collections of this poorly understood taxon would certainly aid in determining its phylogenetic position. In Judd (1981) this taxon was considered conspecific with L. stahlii (vars. costata and stahlii, of Hispaniola and Puerto Rico, respectively) because of their phenetic similarity. The St. Thomas populations, however, are here treated as a distinct species because these populations apparently share no unique apomorphic features with L. stahlii. A broadly circumscribed L. rubiginosa (including L. stahlii) would be extremely paraphyletic (see Figs. 2 & 3).
Distribution:
Saint Thomas Virgin Islands of the United States South America|
Saint Thomas Virgin Islands of the United States South America|