Diastatea tenera subsp. durangensis E.P.Johnson & T.J.Ayers

Johnson, Elizabeth P. & Ayers, Tina J., 2022, Molecular Phylogeny and Taxonomic Revision of the Genus Diastatea (Campanulaceae: Lobelioideae), Systematic Botany (Basel, Switzerland) 47 (1), pp. 61-84 : 75

3b. Diastatea tenera subsp. durangensis E.P.Johnson & T.J.Ayers , subsp. nov.

TYPE: MÉXICO. Durango: Mpio. Suchil. Laguna de Mogotes, alrededores, 8 km de El Aleman, Reserva de la Biosfera La Michilıa , [23.47, -104.26], 17 Nov 1986, F. Acevedo 366 (holotype: CIIDIR ; isotypes: ASC! , IBUG , MEXU ).

Stems 9.5–37 cm tall, simple or a few weak side branches. Leaves, the lowermost deltoid, 2–4 mm long, 1.2–1.8 mm; middle to upper leaves linear, 6–24 mm long, 0.5–1.6 mm wide. Inflorescence with few to 12 flowers; bracts 5.4–20 mm long, 0.4–0.9 mm wide. Flowers with pedicels 3.7–17.5 mm long in flower; calyx lobes subequal, narrowly triangular or linear, 1.1–2.5 mm long in flower, margins with 1–2 pair of teeth at or below the middle, glabrous or ciliolate; corolla purplish-blue or purple, the nectar guides pale yellow, gradually brighter toward throat, with projections at throat; tube 8.8–13.5 mm long from calyx sinus to lateral corolla sinus, 0.8–1.6 mm wide at middle; dorsal lobes obovate, apex acute to mucronate, with narrowed claw attaching distal portion to deltoid base, 6.1–9.0 mm long, 1.8–4.0 mm wide; ventral lobes broadly oblanceolate with mucronate tip, 7.1–11.3 mm long, 2.2–4.3 mm wide; filaments 9.5–13 mm long; anthers 1.7–2.0 mm long. Fruits narrowly ellipsoid, with an unequal base mirroring gibbous corolla, 5.2–10 mm long, 2.2–3.6 mm wide. Figures 4D , 8 , S 4B .

Chromosome Number —Unknown.

Etymology —The new subspecific epithet reflects that the center of distribution of this taxon is in the Mexican state of Durango.

Distribution —Mexican states of Durango, Guanajuato, Jalisco, and Zacatecas ( Fig. 7 ).

Notes —Exceptionally large-flowered individuals of D. tenera have been found in Durango. They appear to be the end point of a cline stretching from Puebla north to Durango, in which the flowers of D. tenera increase dramatically in size. The populations in Zacatecas and Guanajuato have the long corolla tubes of D. tenera subsp. durangensis but their lower corolla lobes are slightly shorter than the populations in Durango and Jalisco.

Because of the distinct difference in size between the individuals found mainly in Durango and the rest of D. tenera , and the fact that the collections appear to have a distinctive range adjacent to the central Mexican Plateau, they are described here as a new subspecies. We chose subspecific rank over varietal rank because varietal rank in the Campanulaceae has been dismissed by Lammers (2006). Future examination of the subspecies should look at habitat and pollinator differences as possible drivers of floral differentiation.

Additional Specimens Examined — Mexico. — DURANGO: San Juan de Michis, Mpio. de Suchil , 25 Oct 1984, Acevedo 150 (TEX, WIS); Mpio. Suchil. San Juan de Michis , 3.5 km al S del poblado, Reserva de la Biosfera La Michilıa, [23.47, -104.26], 21 Oct 1985, Gonzalez & Acevedo 3546 (ASC); Mpio. Suchil, Sierra de Michis, San Agustın, Reserva de la Biosfera La Michilıa , [23, -104], 12 Oct 1984, Jimenez 186 (ASC); Mpio. Suchil, El Aleman, 8 km cerca del Arroyo Las Joaquinas, Reserva de la Biosfera La Michilıa, 18 Nov 1986, Acevedo 376 (ASC); Mpio. Suchil, Reserva de la Biosfera La Michilıa, Portrero Mesa Larga, [23.5, -104.3], 17 Nov 1993, Garcıa A. & Alvarado 1911 (ASC); Mpio. Suchil, Portrero Los Anegados, 3 km de el Aleman, Reserva de la Biosfera La Michilıa, [23.47, -104.26], 11 Oct 1986, Acevedo 306 (ASC); Mpio. Suchil. Potrero El Taray, Reserva de la Biosfera La Michilıa, [23.41, -104.25], 12 Sep 1983, Acevedo s. n. (ASC); Mpio. Suchil. Reserva de la Biosfera La Michilıa, camino Suchil-Charcos, km 51, entrada al Rancho La Pe na ~, [23.4, -104.2], 11 Oct 1992, Garcıa A. 1700 (ASC). — GUANAJUATO: 8 km northeast of Santa Rosa, 10 Nov 1970, McVaugh 24150 (MEXU); Mpio. San Jose, Ca nada ~ Las Peras 3 km al SE de El Zorrillo, 6 Nov 2003, Gutierrez G. et al. 787 (MEXU). — JALISCO: Rancho Viejo, about 10 km east-northeast of Huejuquilla el Alto, 31 Oct 1963, Feddema 2310 (NY, WIS). — ZACATECAS: Plus or minus 35 km al W de Jalpa, sobre la carretera a Tlaltenango; 27 km del entronque con la carretera Jalpa-Juchipila, 23 Oct 1970, Rzedowski & McVaugh 1039 (MEXU, MO, NY, LL).

Figures

FIG. 4. Scanning electron micrograph images of anther trichomes in Diastatea. A–D. Diastatea subgenus Angustifolia. A. Diastatea aptera (Soto 13195). B. Diastatea expansa (Rosiles M. s.n.). C. Diastatea tenera subsp. tenera (Ayers et al. 1777). D. Diastatea tenera subsp. durangensis (Gonzalez 3546). E–H. Diastatea subgenus Diastatea. E. Diastatea ciliata (Reveal et al. 4183). F. Diastatea costaricensis (Smith 1435). G. Diastatea maximiliana (Ayers et al. 1774). H. Diastatea virgata (Ayers et al. 1772).

FIG. 8. Isotype of Diastatea tenera subsp. durangensis held at ASC (F. Acevedo 366).

FIG. 7. Distribution map of all taxa in Diastatea subg. Angustifolia.