Louteridium rzedowskianum T.F. Daniel, 2017

Daniel, Thomas F., 2017, New and Reconsidered Mexican Acanthaceae XII, Proceedings of the California Academy of Sciences 64 (7), pp. 131-154 : 144-146

Louteridium rzedowskianum T.F. Daniel , sp. nov.

Louteridium rzedowskianum differs from its congeners by the following combination of characters: stamens four, calyx 5–9 mm long with lobes broadly ovate to triangular and 3.5‒6. 5 mm long, and capsule pubescent with glandular trichomes only.

Louteridium brevicalyx Rzed., Ciencia ( México) 28: 53. 1973, non Louteridium brevicalyx A. Richardson (1972) , nom. inval. Louteridium rzedowskii T.F. Daniel, Madroño 31: 91. 1984, nom. inval.

TYPE.— MEXICO. Guerrero: Mpio. Chilpancingo, Rincón de la Vía, cerca de Agua de Obispo [ca. 17°17’45.05”N, 099°28’17.54”W], 750 m, 19-I-1964 (flr), H. Kruse 1380 (holotype: ENCB-002790-shoots bearing flowers only; photo seen; isotypes (shoots bearing flowers only): EAP!, ENCB-002789!, FCME!, MEXU!, MICH!, MO!, US!) , see discussion below.

Shrubs to trees to 4 m tall, trunk to 15 cm in diameter at base. Older (woody) stems irregularly fissured-striate, lenticellate, glabrous; younger stems not seen. Leaves deciduous, clustered at branch apices, petiolate, petioles 20-90 mm long, blades apparently subsucculent, lanceolate to ovate to elliptic, 82-260 mm long, 35-110 mm wide, 2-2.6 × longer than wide, (rounded to) acuminate at apex, cuneate to subattenuate at base, abaxial surface minutely glandular punctate (sometimes not evident) and sparsely pubescent (especially near base) with flexuose eglandular trichomes 0.2- 0.7 mm long or trichomes absent on mature leaves, adaxial surface very sparsely pubescent (if at all) with similar trichomes, margin entire to subsinuate, sparsely ciliate with trichomes like those of abaxial surface. Inflorescence a terminal, pedunculate thyrse to 30.3 cm long (including peduncle and excluding corollas), peduncle glandular puberulent with glandular trichomes to 0.1 mm long, rachis pubescent with erect glandular trichomes 0.05- 0.2 mm long; dichasia opposite, pedunculate, mostly 1-3-flowered, to 50 (- 70 in fruit) mm long (excluding corollas), dichasial peduncles 6-14 (- 29 in fruit) mm long, pubescent like rachis. Bracts caducous (not seen). Bracteoles caduceus (not seen). Flowers pedicellate, pedicels 23-30 (- 48 in fruit) mm long, pubescent like rachis. Calyx 5-9 mm long, lobes subheteromorphic, apparently subsucculent, abaxially pubescent with erect to flexuose glandular trichomes 0.05- 0.2 mm long, posterior lobe subconduplicate, broadly ovate to subtriangular, 3.5- 4.5 mm long, 3-4. 3 mm wide, sometimes smaller than lateral lobes, subacute to acute at apex, lateral lobes planar, ovate to subtriangular, 4- 4.8 mm long, 3-4 mm wide, acute at apex. Corolla dark purple with green in places or green with purple in places (fide Rzedowski 73), 35-39 mm long, externally puberulent with erect glandular trichomes to 0.1 mm long, tube 17-30 mm long, narrow proximal portion of tube 4. 5-9 mm long, 6-11 mm in diameter near midpoint, throat 11-20 mm long, 20-25 mm in diameter at mouth, upper lip 11-15 mm long, lobes ovate to subtriangular, 10-11 mm long, 9-11 mm wide, lower lip 12-15 mm long, lobes ovate to subtriangular, 12-13 mm long, 11-12 mm wide. Stamens 4, exserted 35 mm beyond lips of corolla, 55-75 mm long, filaments not seen, thecae 7. 5-8 mm long. Style 80-82 mm long, glabrous, stigma ± funnelform, 1.5 mm long. Capsule 38-47 mm long, pubescent throughout with erect glandular trichomes to 0.1 mm long, stipe 4 mm long. Seeds up to 24 per capsule, 4- 4.5 mm long, 3-4 mm wide, surfaces minutely granulate to ± scurfy, marginal region swollen, periphery pubescent with appressed hygroscopic trichomes.

PHENOLOGY.— Flowering: January; fruiting: January–March. Label information on the type notes that flowers are “pronto caedizas,” possibly referring to their being soon deciduous during the day, and thus likely largely nocturnal as in other species of the genus.

DISTRIBUTION AND HABITAT.— Western Mexico (central Guerrero; Fig. 6); plants occur on limestone slopes in tropical subdeciduous forests (selva mediana subcaducifolia) at elevations near 750 m.

ILLUSTRATION.— Rzedowski (1973: fig. 4).

CONSERVATION.— This species remains known only from the type locality, where an unknown number of individuals occurs, and from which specimens were collected over a period of seven years (1963–1970). No information is known as to the current status of this population or any possible threats to it. Therefore, according to IUCN (2017) guidelines, Louteridium rzedowskianum has to be assessed as Data Deficient (DD).

PARATYPES.— MEXICO. Guerrero: Mpio. Chilpancingo, Rincón de la Vía, cerca de Agua de Obispo [ca. 17°17’45.05”N, 099°28’17.54”W], 9-VIII-1964 (vegetative) and 23-III-1963 (fruiting), H . Kruse 1380 ( EAP, ENCB, FCME, MEXU, MICH, MO, US) ; Mpio. Chilpancingo, Rincón de la Via [17º17’15”N, 99º28’55”W], 27-I-1970, H . Kruse 2701 [catalog # 4755] ( MEXU); same locale, 14-VII-1970, H . Kruse 2701-b [catalog #5033] ( FCME, MEXU) .

DISCUSSION.— Although validly published at the time, but illegitimate, Louteridium brevicalyx Rzed. is no longer accepted as valid because more than one gathering was included within the type —a retroactive change in Article 8 of the nomenclatural rules enacted in the “Saint Louis Code” ( Greuter et al. 2000). This species subsequently became known as “ L. rzedowskii ” when Daniel (1984) proposed a new name for Rzedowski’s later homonym. Daniel’s name also became invalid with the change in Article 8. To rectify this situation, and to honor Jerzy Rzedowski and his recognition of the species, Louteridium rzedowskianum is herewith newly described.

The sole collector of this species, Hubert Kruse, obtained specimens of these plants on multiple occasions in order to have leaves, flowers, and fruits. These were admixed to create “complete” herbarium specimens, with an indication of the date of collection of foliage (i.e., 9 Aug 1964), flowers (i.e., 19 January 1964), and fruits (i.e., 23 March 1963) on each one. Because the specimens all contain materials of these organs collected on different dates, the citation of any one of the specimens as the type is no longer acceptable for valid publication of the name. The flowering portion (only) of the Kruse specimen designated by Rzedowski as the holotype of L. brevicalyx at ENCB is designated above as the holotype of L. rzedowskianum . Fruiting and vegetative portions of this specimen, those same portions on the isotypes noted above, and the subsequent (1970) Kruse collections noted above are all paratypes.

Agua de Obispo is about 3 km (linear distance) NE of Rincón de la Vía , on the old Chilpancingo–Acapulco highway ( Mexico 95). It is at an elevation of about 960 meters, whereas Rincón de la Vía is at about 750 meters. Therefore Kruse’s locality information is somewhat contradictory. I have mapped the species between these two locales. Kruse made additional collections from the type locality in 1970. Plants bearing leaves only were collected from the type locality in July and August. Leaves are not present on plants collected in January–March. According to information on Kruse 2701-b, leaves were taken from the same individual from which fruits and flowers were collected at other times .

This species can be distinguished from L. brevicalyx A. Richardson , which also occurs in dry forests of western Mexico, by characters in the following couplet:

Calyx 10–14 mm long, 3-lobed or 5-lobed with 3 large lobes and 2 reduced lobes, 3 large lobes lanceolate to ovate, 8–11 mm long; capsule pubescent with straight, eglandular trichomes 0.2– 0.5 mm long; Michoacán ........................................ L. brevicalyx

Calyx 5–9 mm long, 3-lobed (reduced lobes absent), lobes broadly ovate to triangular, 3.5–6. 5 mm long; capsule pubescent with glandular trichomes to 0.1 mm long (lacking straight, eglandular trichomes); Guerrero ........................................... L. rzedowskianum