Lobelia rzedowskii, 2018

Gutiérrez-Sánchez, Rosa Ivonne, Castro-Castro, Arturo, Gallegos, Jesús Guadalupe González-, López-Enríquez, Irma Lorena & Frías-Castro, Alfredo, 2018, Synopsis of the spurred species of Lobelia section Stenotium (Campanulaceae) in Sierra Madre Occidental, Mexico, and the description of two new species, Phytotaxa 338 (1), pp. 33-48 : 39-42

9. L. rzedowskii Art.Castro & I.Gutiérrez , sp. nov. ( Figures 3–4 )

Lobelia rzedowskii is similar to L. endlichii but differs by leaf blades 0.5–1.5 × 0.4–1 cm, frequently subsessile, racemose to paniculate inflorescences, with (4–)10–35(–191) flowers, flowers 4–6 mm long including hypanthium, spur 0.5–1 × 0.5–0.8 mm, with the lower two calyx lobes positioned at the middle portion of the spur, a white corolla with a yellow spot above lobe sinuses at the throat and a staminal tube 1.3–2.5 mm long.

Type:— MEXICO. Nayarit: Ruiz, San Pedro Ixcatán-Presidio, margen derecho del cañón del río San Pedro, 22.403478°N, 105.245146°W, 308 m, 7 March 2009 (fl, fr), A. Castro-Castro et al. 1742 (holotype CIIDIR!, isotypes CIIDIR!, IBUG!, IEB!, MEXU!, SLPM!, USON!).

Annual, erect herbs, (14–)25–35(–51) cm tall. Stems reddish to purplish, strigose to hirtellous, the trichomes singlecelled, subulate and white. Leaves 3–5(–8), rosulate; petiole (0.1–) 0.5–0.8 cm long, sometimes subsessile, glabrescent, cylindrical; lamina 0.5–1.5 × 0.4–1 cm, elliptic to ovate, entire, repand and minutely denticulate, glabrescent, membranaceous, rounded, decurrent. Inflorescence racemose to paniculate, with (4–)10–35(–191) flowers, the whole inflorescence occupies more than 4/5 of the height of the plant; peduncles 5–9(–30) long; sterile bracts (0.3–)1.5–2.5 × 0.3–0.9 cm, fertile bracts (0.1–)0.6–2 × 0.1–0.3 cm, both glabrescent, entire, and linear to lanceolate; pedicels (0.1) 1– 2.5 cm long, ebracteolate, filiform, smooth, generally arcuate at the distal portion. Flowers 4–6 mm long including the hypanthium, this 0.5–1.5 mm long from the upper side, campanulate, the lower side extending together with the corolla towards a conical spur projecting outwards in less than 1 mm in length, but as a whole is about 1–2 mm long from the base of the upper segments of the calyx ( Figure 3 . A-B); calyx segments, 1–2.3 × 0.5–1.3 mm, linear, entire, sometimes ciliate, superior sepals divaricate to diffuse and generally perpendicular to the flower pedicel, inferior sepals located 0.5 mm below the three superior segments, erect to appressed to the flower pedicel; corolla resupinate; corolla tube 2.5–4 × 0.5–1.4 mm, white with longitudinal purple lines and yellow spotted on the basal portion of ventral corolla lobes and the throat, cleft to the base, not fenestrate; dorsal corolla lobules 1–2 × 0.2–0.4 mm, linear to narrowly triangular, divaricate to slightly reflexed; ventral corolla lobes 1.5–2.5 × 0.5–2.2 mm, spatulate to obovate, mucronate; staminal tube 1.3–2.5 mm long; anthers 0.6–1.3 mm long, connate, dark blue to brown, the three upper anthers are slightly longer and curved distally toward the lower two and often covered with short slender trichomes only along the connections of adjoining thecae, apices of the two lower anthers are armed with a white-tufted of stiff trichomes ( Figure 3. D ); style 1.2–1.6 mm long, thickened toward the distal portion, glabrous, stigma minutely 2-lobed, the lobes tomentose on the ventral portion. Capsule 2–3 × 1–2 mm, ellipsoid, 3–4/5 inferior, remainder of style short, calyx persistent, dry and wrinkled at the base of the capsule ( Figure 3. C ). Seeds 25–40 per capsule, 0.3–0.4 × 0.2–0.3 mm, ellipsoid, light brown or reddish, smooth to the naked eye, shining with fine striations apparent under magnification ( Figure 3. E ).

Distribution, ecology and phenology: — Lobelia rzedowskii is endemic to northwestern Nayarit, in the south extreme of the Madrean Tropical region of the Sierra Madre Occidental, based on the regionalization of González-Elizondo et al. (2012; Figure 1 ). It was collected in an ecotone between savanna-like vegetation, tropical subdeciduous, deciduous and oak forest, on rocky steep slopes with very thin soil. The species grows at elevation range of 160– 308 m. The most notable associated species are Adiantum patens Willdenow (1810: 439) , Alophia intermedia ( Ravenna 1964: 55) Goldblatt (1975: 384) , Bursera spp. , Byrsonima crassifolia ( Linnaeus 1753: 426) Kunth (1821: 149) , Crusea parviflora Hooker & Arnott (1840: 430) , Curatella americana Linnaeus (1759: 1079) , Erythroxylum mexicanum Kunth (1821: 178) , Hyptis capitata Jacquin (1787: 102) , Lobelia flexuosa , Miconia saxicola Brandegee (1905: 215) , Muhlenbergia microsperma ( de Candolle 1813: 151) Kunth (1835: 64) , Ouratea madrensis Riley (1924: 363) , Oxypappus scaber Bentham (1845: 118) , Platymiscium trifoliolatum Bentham (1860: 82) , Quercus aristata Hooker & Arnott (1841: 444) , Swietenia macrophylla King (1886: 1550) and Tabebuia palmeri Rose (1891: 109) . Individuals of Lobelia rzedowskii were collected in flower and fruit from December to March.

Conservation status: — Lobelia rzedowskii is represented by five collections in close proximity. Using GeoCAT ( Bachman et al. 2011) the Extent of Occurrence (EOO) was of 6.322 km 2, and the size of the Area of Occupancy (AOO) is 12 km 2, based on cells of 2 × 2 km. According to EOO and AOO results and following the IUCN (2013) criteria (Area of Occupancy estimated to be less than 10 km 2), a preliminary category of critically endangered is proposed (CR/B2biii). Moreover, the populations near the San Pedro-Mezquital River are threatened by the construction of a hydroelectric dam that would submerge all populations ( SEMARNAT 2014).

Etymology: —This species is named in honor to Dr. Jerzy Rzedowski Rotter (1926–), an emeritus researcher and influential leader of Mexican scientists in the field of botany. He has made important contributions to our understanding of North American plant diversity through space and time.

Additional specimens examined: — MEXICO. Nayarit: Acaponeta, km 8–30 de la brecha entre Santa Cruz de Acaponeta y San Blasito , 22°24’59”N, 105°6’8”W, 880 m, 12 January 2013 (fl, fr), A. Castro-Castro et. al. 3518 ( IBUG!, CIDIIR!, IEB!, MEXU!) ; Rosamorada , 500 m N de San José del Motaje UTM 474768N, 2477508E, 160 m, 12 December 2008 (fl, fr), F.J. Rendón-Sandoval et. al. 172 (CIIDIR!, IBUG!, MEXU!) ; Ruiz, San Pedro Ixcatán, Las Cruces, entre La Cañada de La Virgen y el arroyo Agua Caliente , UTM 505779 N, 2543327 E, 250 m, 14 January 2009 (fl, fr), A. Castro-Castro et. al. 1595 ( CIIDIR!) ; ibid., A. Castro-Castro et. al. 1609 ( IBUG!) ; ibid., 5 May 2009 (fl, fr), A. Castro-Castro 4242 ( CIIDIR!) ; junto a la orilla derecha del Río San Pedro, San Pedro Ixcatán , UTM 2446482N, 505004E, 174 m, 31 January 2009 (fl, fr), A. Frías-Castro et. al. 1019 ( IBUG!) ; San Pedro Ixcatán, transecto del camino entre El Puerto y el arroyo Las Mojarras , y hacia la orilla derecha del Río San Pedro-Mezquital , 22°5’12’’N, 105°55’25’’W, 400 m, 12 January 2013 (fl, fr), A. Castro-Castro et al. 3604 ( IBUG!) .

Discussion: —Due to the presence of flowers 4–7 mm long with spurs less than 2.5 mm long, Lobelia rzedowskii is similar to L. ayersiae , L. cordifolia and L. endlichii . However, L. rzedowskii differs by the corolla color, size and amount of flowers, size and arrangement of leaves and inflorescences, and the size of the spur and staminal tube. The morphological and distributional differences between these species are highlighted in the identification key, diagnosis and Table 1.

Figures

FIGURE 1. Distribution map of spurred species of Lobelia along the Sierra Madre Occidental, Mexico. A. L. ayersiae (■), L. flexuosa (○), L. goldmanii (□), L. knoblochii (∆) and L. mcvaughii (♦). B. L. cordifolia (▲), L. endlichii (●), L. macrocentron (*), L. rzedowskii () and L. saturnini (▼).

FIGURE 3. Lobelia rzedowskii Art.Castro & I.Gutiérrez. A. Lateral view of a staminate and pistillate-phase flower, showing the position of staminal tube. B. Frontal view of staminate-phase flower C. Mature capsule with remainder of style and calyx. D. Detail of anther tube, including apical hairs on ventral anthers. E. Seeds. Drawn by Lesslie Martínez Rubí from the type material.

FIGURE 4. Lobelia rzedowskii Art.Castro & I.Gutiérrez. A. Inflorescence branching. B. Flower detail.