Calliandra estebanensis H.M. Hern., 2019

Hernández, Héctor M. & Gómez-Hinostrosa, Carlos, 2019, A narrowly endemic new species of Calliandra series Racemosae (Fabaceae) from Sinaloa, Mexico, Phytotaxa 401 (1), pp. 49-54 : 50-53

Calliandra estebanensis H.M. Hern. , sp. nov. ( Figs. 1–2 )

Calliandra estebanensis is closely related to C. grandiflora L’Héritier (1788: 30) Bentham (1840: 139) from which it could be distinguished by having flowers with longer (1.1–2 cm vs. 0.6–1.2 cm) peduncles, shorter (4–6 mm vs. 6–10 mm) pedicels, and larger calyces (2–4 mm vs. 1–2 mm) and corollas (10–16 mm vs. 8–12 mm), prominently covered by a much denser white-sericeous (vs. white, black or ferruginous pilose) vestiture.

Type:— MEXICO. Sinaloa, municipality Badiraguato, Los Laureles, 75 km NE of Mocorito on road to Surutato , 25º53’45’’ N, 107º40’40’’ W, 1430 m, 2 August 1983 (fl., fr.), E. Martínez S. et al. 4180 (holotype: MEXU 1478305!; isotypes: CICY!, ENCB!, K!, MEXU 1478306!, MO!, NY!) .

Shrubs to 2 m high, erect; stems slender; stipules 5 mm long, adpressed, narrowly triangular, white-sericeous, usually caducous. Leaves microphyllidious; pinnae 15–32-jugate; petioles 0.5–0.9 cm long, tomentose or velutinous with white or brown trichomes; rachis 13.3–25 cm long, tomentose or velutinous with white or brown trichomes; rachillae 3.5–5.8 cm long; leaflets 42–56 pairs per pinnae, 4–5 × 0.8–1 mm, narrowly oblong-lanceolate, thinly coriaceous, glabrous at the abaxial and adaxial faces, ciliate at margin, oblique at base, acute at apex, with a single primary, sub-central vein visible under magnification. Inflorescences organized in terminal, conical pseudoracemes formed by numerous umbellate capitula arising at several nodes along a central axis; axis 10.5–18.5 cm long, covered by a dense vestiture of white trichomes; umbels usually 3 per node; peduncles, 1.1–2 cm long, 1–1.5 mm diameter at anthesis, whitetomentose. Flowers homomorphic, usually 3–5 per umbel; pedicels 4–6 × 0.8–1 mm at anthesis, white-tomentose; perianth coriaceous, densely white-sericeous externally, glabrous internally; calyx 2–4 × 4–7 mm, short-campanulate; corolla 10–16 mm long, campanulate, the lobes lanceolate, (3–)4–7 wide; filaments 9.7–10.5 cm long, red or pinkishred; the staminal tube inserted, ca. 4 mm long; polyads 8-grained, 189–242 × 126–146 μm, flattened, bisymmetric, with a mucilaginous appendage on the basal cell; ovary white-velutinous; style ca. 12 cm; stigma capitate. Pods erect or ascending, to 12.5 × 1.5 cm, ligneous, velutinous with white, long trichomes. Seeds unknown.

Etymology:—This species in named to honor Esteban Martínez S. (1954–), a Mexican botanist based at the National Herbarium of Mexico (MEXU), who over the last 36 years has produced tens of thousands of botanical collections from all over Mexico and described numerous taxa, greatly contributing to our knowledge of the flora of this country.

Distribution and habitat:— Calliandra estebanensis is currently known only from two neighboring localities at the Sierra de Surutato, northern Sinaloa, Mexico ( Figure 3 ). The area is a mountain range of volcanic origin with elevations ranging from 1430 to 2130 m. The vegetation is a mixture of pine and pine-oak forest, and grassland ( Gentry 1946).

Phenology:—Flowering: August–September; fruiting: August–September.

Additional specimens examined:— MEXICO. Sinaloa: Ocurahui, Sierra Surotato [Surutato], 25º56’ N, 107º39’01’’ W, 1830–2130 m, 1–10 September 1941 (fl., fr.), H.S. Gentry 6330 (ARIZ, MEXU, MICH); same locality and date, (fl., fr.), H.S. Gentry 6330-A (ARIZ, MEXU, NY) .

Taxonomic notes: — Calliandra estebanensis clearly belongs to C. ser. Racemosae Bentham (1844: 111), which includes eight Mexican and Central American microphyllidious species characterized by having terminal, efoliate pseudoracemose inflorescences, with the flowers grouped in capitula or umbels inserted in several nodes along elongated axis ( Macqueen & Hernández 1997). Bentham’s C. ser. Racemosae , however, was sunk by Barneby (1998: 148–149) into C. ser. Calliandra , which includes 39 species grouped into two geographically congruent assemblages, one in Brazil, and the other in Mexico and Central America. Nonetheless, we consider C. ser. Racemosae as an acceptable taxon to include a compact group of North and Central American species with racemose inflorescences and, thus, treat C. estebanesis under it.

The precise taxonomic relationships of the new species are difficult to determine based on overall morphology. There are three species in Calliandra ser. Racemosae , occurring in western and northwestern Mexico, that may be superficially confused with C. estebanensis : C. palmeri S. Watson (1887: 410) , C. longipedicellata McVaugh (1987: 151–152) Macqueen & Hernández (1997: 40) and C. grandiflora . The former two are endemic to western Mexico ( Figure 3 ) and are clearly segregated geographically with respect to C. estebanensis . On the other hand, C. grandiflora is a widespread and morphologically variable species occurring from northwestern Mexico (Durango, Sinaloa and Sonora) to Honduras and El Salvador ( Macqueen & Hernández 1997), and is sympatric with C. estebanensis .

Calliandra estebanensis and C. palmeri share the presence of relatively large flowers and pods covered by a dense white-sericeous or velutinous vestiture. However, C. estebanensis may be readily distinguished from that species by its shorter petioles and rachillae, higher number of pairs of pinnae, smaller leaflets, shorter inflorescences, longer peduncles and pedicels, and smaller calyces, corollas and pods ( Table 1 ). In turn, C. estebanensis may be distinguished from C. longipedicellata by being shorter, up to 2 m tall shrubs (vs. up to 6 m tall small trees in C. longipedicellata ), and by its longer rachis, higher number of pinnae, white-sericeous vestiture (vs. amber-colored vestiture) and shorter pedicels ( Table 1 ).

Calliandra grandiflora may be the closest relative of C. estebanensis . The two species differ mainly in size of floral organs and vestiture, as highlighted in the diagnosis. In addition, C. estebanensis usually has larger leaf parts (e.g., longer rachis and rachillae, more pairs of pinnae and leaflets, and larger leaflets); however, although differences in leaf characters between the two species are usually clear in most herbarium specimens, in cases they tend to overlap ( Table 1 ).

Figures

FIGURE 1. Calliandra estebanensis H.M. Hern. A. Branchlet with inflorescence at anthesis and developing pod. B. Leaflet. C. Detail of calyx and corolla. D. Dissected flower showing the staminal tube and pistil. E. Detail of the ovary. F. Pod. Vouchers: A–E, E. Martínez et al. 4180 (MEXU); F, H.S. Gentry 6330-A, (MEXU). Drawn by Albino Luna.

FIGURE 2. Unacetolyzed 8-grained polyad of Calliandra estebanensis. Voucher: E. Martínez et al. 4180 (MEXU). Scale bar = 100 μm.

FIGURE 3. Geographical distribution of Calliandra estebanensis (red dots), C. palmeri (blue squares) and C. longipedicellata (yellow diamonds).