Anetanthus disjuncta L.E. Skog & J.L. Clark, 2015

Skog, Laurence E. & Clark, John L., 2015, NOVAE GESNERIACEAE NEOTROPICARUM XIX: A third, new species of the elusive Anetanthus found in Guyana, Phytotaxa 218 (2), pp. 177-183 : 177-182

Anetanthus disjuncta L.E. Skog & J.L. Clark , sp. nov. ( Figs. 1–2 )

Differs from congeners by larger leaves (> 4 cm long) that are elliptic, narrowly ovate, to subfalcate. Capsules oblong to 8 mm long (vs. <8 mm long).

Type:— GUYANA. Potaro-Siparuni Region. Mt. Ayanganna , east face, slopes of first of four escarpments, 5°19’58’’N, 59°56’ 4’’W, 810 m, 9 June 2001, H. D. Clarke, R. Williams, C. Perry, E. Tripp & J. Kelly 8979 (holotype US!; isotypes: BRG!, E!, MO!, NY!) .

Terrestrial herbs growing in cracks of sandstone vertical rock faces; stems to 30 cm long, slender, 2–3 mm in diameter at base, green to reddish-brown, appressed tomentose; unbranched or branching only at the base. Leaves opposite, subequal to unequal; blades elliptic, narrowly ovate, to subfalcate, 4–11.5 cm long, 1.5–5.2 cm wide, membranous to chartaceous, apex acute to acuminate, base acute to suboblique, margin serrate to serrulate, adaxial surface green, mostly glabrous (sparsely pilose), abaxial surface lighter green to green suffused with red, appressed pilose along the veins and otherwise sparsely pilose; petioles 0.5–2.5 cm long, appressed pilose. Inflorescences erect, in upper axils, usually forked, 2 flowers at base of fork, each branch with 10+ flowers, peduncles slender 2–5.5 cm long, tomentose, pedicels short, 2–3 mm long. Flowers fragrant with odor of wintergreen, calyx lobes nearly separate at base when mature, and appressed to corolla when young, narrowly lanceolate, to 2 mm long, ca. 0.5 mm wide, green to red to green suffused with red, glandular-pilose outside, apex narrowly acuminate; corolla tubular, 6–8 mm long, gibbous on upper side near base and narrowing towards throat, uniformly white, outer surface sparsely pilose, inside of throat glandular pubescent on lower side, lobes 5, unequal and spreading, upper lobes suborbicular, 2 mm wide, lower lobes subtriangular to elongate, 1.5 mm wide at base and 2.5 mm long, margins irregularly erose, glandular trichomes at base; stamens included, anthers ca. 0.5 mm long, coherent in 2 pairs on upper surface at anthesis then separating later dropping into the lower corolla surface after anthesis; staminode present at base of corolla tube; ovary pilose, elongate, nectary glands at base of ovary with two larger and two smaller glands; style persistent, stigma stomatomorphic. Capsule elongate oblong, 5–8 mm long, 2-valved and dehiscing septicidally; seeds suborbicular, light brown.

Phenology and distribution:—Specimens have been collected in June and November, and been seen in flower in February ( Fig. 2 ), at 800 to 1100 m on Mt. Ayanganna in the Pakaraima mountains of Guyana.

Conservation and IUCN Red List category: — Anetanthus disjuncta is known only from Mount Ayanganna in Guyana. According to the IUCN Red List criteria ( IUCN 2012) for limited geographic range ( B 2a, less than 10 km 2 and known to exist at only a single location), Anetanthus disjuncta should be listed in the category CR (Critically Endangered).

Etymology: —The species name refers to the locality of Anetanthus disjuncta in Guyana that is far removed from where other species of the genus have been found.

Discussion:— Anetanthus disjuncta joins the other two species in the genus. The first, A. gracilis Hiern (1877: 93) ( Fig. 3 ), the lectotype species, has been collected in Bolivia, Colombia, Ecuador, and Peru, usually at higher elevations (500–2250 m), but also has been collected in Brazil in the states of Minas Gerais and Rio de Janeiro, and in the Distrito Federal. The species was described by Hiern (1877: 93) from Minas Gerais based on a Warming specimen at C annotated by R. A. Howard (1974: 365) as the lectotype. The genus name was first attributed to Hiern but described by Bentham (1876, pp. 996, 1025), who reported that four or five species existed in Brazil, Peru, and Mexico. Bentham, however, lists no species or combinations in Anetanthus but mentions three species that he believed should be in the genus. The first, “ Dicyrta ( Trevirania, Hook. et Arn. ) parviflora Seem.,” is now a synonym of Stemodia peduncularis Bentham (1846: 382) ( Plantaginaceae ). The second, “ Russelia alata Cham. et Schl. ” had earlier been listed by Bentham (1846: 332) as a species dubia in the Scrophulariaceae , but Chamisso and Schlechtendal (1828) and Schmidt (1862, p. 269, t. 44) had included the species in the family. A later monographer of Russelia, Carlson (1957: 285) had discarded the species from the Scrophulariaceae following Bentham (1876), and referred the species to the Gesneriaceae . Barringer transferred the species to his new genus Cubitanthus ( Barringer 1984: 145) as C. alatus (Cham. & Schlecht.) Barringer in Gesneriaceae . More recently molecular phylogenetic analyses by Perret et al. (2012) strongly support the placement of Cubitanthus as sister to Stemodiopsis Engler (1897: 25) in the Linderniaceae . The third species included in Anetanthus by Bentham was Tapina villosa Gardner (1842: 469) , now known as Goyazia villosa (Gardn.) R.A. Howard (1975: 367) in the Gesneriaceae . Thus, at the time of publication of Anetanthus as a genus, there were no species now accepted as Anetanthus included in the genus. Fortunately in the following year, Hiern (1877) published a more extensive description of the genus and included a new species, A. gracilis , which became the lectotype of the genus ( Morton and Denham, 1972).

The one subspecies in Anetanthus was described in 1995 by Fernández Alonso as Anetanthus gracilis subsp. munchiquensis Fernández Alonso (1995: 383) . The new subspecies was distinguished from the typical A. gracilis ( Fig. 3 .) by having shorter peduncles.

The second accepted species of the genus is Anetanthus rubra L.E. Skog (1982: 94) , described from Amazonas, Peru ( Skog, 1982). It is considered a local endemic that is only known from the type locality, distinguished by several characters from the other species but noticeably by the red corollas ( Fig. 4 ).

Additional specimens examined: Guyana. Cuyuni-Mazaruni. Pakaraima Mountains, toe slopes on NW side of Mt. Ayanganna, 5°24’0’’N, 59°57’ 0’’W, 1100 m, 7 November 1992, T.W. Henkel & B. Hoffman 164 (BRG!, US!). Potaro-Siparuni. Mt. Ayanganna, east face, plateau above edge of first of four escarpments, 5°20’2’’N, 59°56’ 4’’W, 1008 m, 10 June 2001, H.D. Clarke, R. Williams, C. Perry, E. Tripp & J. Kelly 9041 (BRG!, US!).

Figures

FIGURE 1. Anetanthus disjuncta L.E. Skog & J.L. Clark. A. Habit. B. Underside of leaf. C. Inflorescence branch. D. Side view of flower. E. Face view of flower. F. Corolla opened to show 4 stamens. G. Flower with corolla removed to show pistil and nectary. H. Capsule. I. Seeds. (Drawn from H.D. Clarke et al. 8979).

FIGURE 2. Anetanthus disjuncta L.E. Skog & J.L. Clark. A. Front view of flower with inflorescence. B. Side view of flower with inflorescence. C. Mature fruit showing septicidal dehiscence. D. Immature fruit with persistent calyx. E. Habit. (Photos by John L. Clark from 2014 field expedition to Mt.Ayanganna).

FIGURE 3. Anetanthus gracilis Hiern. A. Habit. B. Upper leaf surface. C. Side view of flower. D. Flower cut open to show ovary and stamens. E. Young capsule. F. Opened capsule. G. Seeds. (Drawn from J. Schunke V. 5311).

FIGURE 4. Anetanthus rubra L.E. Skog. A. Habit. B. Upper leaf surface. C. Side view of flower. D. Flower (longitudinal section), showing ovary and stamens. E. Young fruit. F. Opened capsule. G. Seeds. (Drawn from J. Wurdack 1469). Reprinted with permission from Selbyana.