Calliandra mayana H.M. Hern., 2017

Hernández, Héctor M. & Gómez-Hinostrosa, Carlos, 2017, Calliandra mayana (Leguminosae, Mimosoideae), a new narrowly endemic species from Campeche, Mexico, Phytotaxa 307 (4), pp. 278-284 : 280-283

Calliandra mayana H.M. Hern. , sp. nov. ( Figs. 1–3 )

Calliandra mayana is closely related to C. molinae from which may be distinguished by being smaller shrubs up to 4 m (vs. 7 m), by the branchlets with bark slightly suberose (vs. thickly suberose), by the smaller petioles, rachis, rachillae and leaflets and less numerous pairs of pinnae and leaflets (vs. leaf parts larger and more numerous), and by the glabrous leaflets and corollas (vs. pubescent leaflets and villous corollas).

Type:— MEXICO. Campeche, municipality Hopelchén, 9 km S of Pachuitz , 19º4’8’’ N, 89º13’39’’ W, 80 m, 20 August 2016 (fl), H. M. Hernández et al. 4122 (holotype: MEXU 1446712 !; isotypes: CICY!, ENCB!, K!, MEXU!, MO!, NY!, TEX!, US!, XAL!) .

Shrubs to 4 m high, erect; stems up to 12 cm diameter at base; bark scaly, with long, longitudinal, detachable plates, woody; branchlets terete, with bark slightly suberose; stipules to 6 mm long, adpressed, triangular, narrowly triangular or lanceolate, somewhat curved, glabrous or glabrate, ciliate, persistent, densely imbricated, forming brachyblasts ca. 2(–4) cm long. Leaves usually arising from brachyblasts; pinnae (1–)2-jugate; petioles 0.3–1.1 cm long, villous; rachis (0–) 0.6–1.1 cm long, villous; rachillae 2.4–4.8 cm long, villous; leaflets 7–11 pairs per pinnae, 7–11 × 3–4(–5) mm, oblong, the apical pairs obovate, thinly coriaceous, consistently glabrous at the abaxial and adaxial faces, but ciliate at margin and sometimes along the primary vein, oblique at base, rounded or minutely apiculate at apex; leaflet venation visible only under magnification, with 2 or 3 prominent veins arising from base, the thicker one eccentric, the secondary ones located on one side of the lamina, curved. Inflorescences organized in hemispheric capitula, usually arising from brachyblasts, each one with approximately 10–14 flowers; peduncles 5–9 mm long, 0.75–1 mm diameter at anthesis, always with 1–3, 2 mm long isolated bracts in the apical half, villous or glabrous. Flowers heteromorphic, 1 larger central flower with a longer staminal tube and several peripheral ones, all sessile; calyx campanulate or tubularcampanulate, membranous, striate, glabrous; corolla infundibuliform, membranous, glabrous; filaments ca. 4 cm long, white in the basal half and red in the distal half. Central flower with calyx ca. 4.5 mm long; corolla ca. 9 mm long; the staminal tube exserted, ca. 11 mm long. Peripheral flowers somewhat variable in size within one head; calyx 2–4 mm long; corolla 4–7 mm long; the staminal tube inserted, sometimes slightly exserted. Polyads 8-grained, 127–166 × 74–86 μm, flattened, bisymmetric, with a mucilaginous appendage on the basal cell. Pods erected or ascending, to 4 × 0.7 cm, rigidly coriaceous, scarcely villous, with white, short trichomes. Seeds unknown.

Etymology:—This species in named to honour the Maya, an indigenous people that has continuously inhabited parts of south-eastern Mexico and Central America during several millennia. The Maya civilization flourished in the Yucatan Peninsula, Chiapas, Guatemala and Belize, and the western portions of Honduras and El Salvador, from 2000 BC to 950 AD.

Distribution and habitat:— Calliandra mayana is currently known only from an extremely small seasonally flooded savannah area surrounded by forest in Calakmul, eastern Campeche, Mexico, close to the Quintana Roo border, at 80 meters elevation ( Figure 4 ). The Calakmul area is the largest tract of well-preserved tropical deciduous and sub-deciduous forest in Mesoamerica.

Phenology:—Flowering: June–August; fruiting: unknown.

Conservation status:—The new species is known only from a small area, where less than 20 individuals were detected at the edge of the savannah. Although the locality is included within the northern portion of the Calakmul Biosphere Reserve polygon, there is presence of cattle in the area and indication of recent fires is evident. In addition to its apparently small area of occupancy (<2 km 2), its extremely low population number and the pressures exerted by cattle and fires, C. mayana appears to be under severe reproductive stress adding a further negative element to its probably critical conservation status. During a recent visit to the type locality during the flowering season, on August 2016, we noticed severe damage to most inflorescences caused by larvae of unidentified species of Lepidoptera and Coleoptera ( Figure 2E ). The small larvae feed on the inside of the flower buds totally consuming the stamens and pistils prior to anthesis, severely reducing the reproductive output of C. mayana . Although the magnitude and periodicity of this damage remains to be assessed quantitatively, we speculate that it might be extremely severe. During our visit in 2016 virtually all inflorescences where drastically damaged, and, in only few exceptional cases, 1–3 isolated flowers within a few inflorescences were able to reach normal anthesis ( Figure 2D–E ). Surprisingly, we were unable to see a single inflorescence with its full array of 10–14 undamaged flowers. Although the demography and reproductive biology, as well as the magnitude of the herbivore damage, of C. mayana need to be studied in detail, it is possible to estimate that it is a Critically endangered species, based on IUCN criteria ( IUCN 2001).

Additional specimens examined:— MEXICO. Campeche: Hopelchén, 9.1 km S of Pachuitz , 19º4’8’’ N, 89º13’39’’ W, 109 m, 14 June 2004 (fl), D. Álvarez et al. 9060 ( MEXU) ; same locality, 19º4’5’’ N, 89º13’39’’ W, 119 m, 4 August 2004 (fl), D. Álvarez et al. 10250bis ( MEXU) .

Figures

FIGURE 1. Calliandra mayana H.M. Hern. A. Branchlet with inflorescence at anthesis. B. Brachyblast. C. Leaflet. D. Capitula with flowers in bud. E. Flower. F. Pod. Vouchers: A, C–F, H.M. Hernández et al. 4122 (MEXU); B, D. Álvarez et al. 9060 (MEXU). Drawn by Albino Luna.

FIGURE 2. Calliandra mayana in its habitat. A. Habit. B. Main stem. C. Branch. D. Inflorescence with three flowers beginning anthesis. E. Branchlets showing remains of inflorescences damaged by Lepidoptera and Coleoptera larvae (arrows). Voucher: H.M. Hernández et al. 4122 (MEXU).

FIGURE 3. SEM micrograph of an unacetolyzed 8-grained polyad of Calliandra mayana. Voucher: H.M. Hernández et al. 4122 (MEXU). Scale bar = 50 μm.

FIGURE 4. Geographic distribution of Calliandra mayana (red dot), C. belizensis (yellow squares) and C. molinae (blue diamonds).