Miconia thomasiana DC., Prodr.

Bécquer, Eldis R., Bochorny, Thuane, Gavrutenko, Maria & Michelangeli, Fabián A., 2022, A revision of the “ basal-axile placentation clade ” of Miconieae, the newly erected Miconia sect. Liogieria (Melastomataceae: Miconieae) from the Greater Antilles, Willdenowia 52 (3), pp. 387-432 : 419-421

11. Miconia thomasiana DC., Prodr. 3: 189. 1828 ≡ Acinodendron thomasianum (DC.) Kuntze, Revis. Gen. Pl. 2: 953. 1891 ≡ Tamonea thomasiana (DC.) O. F. Cook & G. N. Collins in Contr. U. S. Natl. Herb. 8: 249. 1903.

– Lectotype (designated here): Antilles , St. Thomas? [without collector and number] ( G-DC 201736 [photo!]). – Fig. 21. = Miconia vernicosa Naudin in Ann. Sci. Nat., Bot.,

ser. 3, 16: 191. 1851. – Lectotype (designated here):

Antilles, Puerto Rico, Pleé s.n. (P 5281685 [photo!]).

Morphological description — Shrubs or small trees to 6 m tall, evergreen but sometimes inflorescence branches deciduous before flowering. Indumentum of stellate and dendritic trichomes 0.1–0.3 mm long, brown to ferruginous on young branches, leaves, inflorescences, flowers and fruits, and elongate glandular trichomes 0.8–1.5 mm long, reddish on petiole, inflorescences, flowers and fruits. Young branches terete, densely tomentose, later glabrescent. Mature branches with light brown bark and longitudinal lenticels. Petiole (0.4–) 1–1.9 cm long, terete, canaliculate and setulose adaxially; leaf blade 4–16 × 2.5–8 cm, ovate to elliptic, coriaceous, base rounded to slightly cordate, apex acute to acuminate, margin flat to slightly revolute, entire to serrulate-denticulate, largest teeth to 0.6 mm long (when present); adaxial surface flat to slightly bullate, reticulate, glabrescent, shiny; abaxial surface glabrescent. Venation with 2(or 3) pairs of secondary veins, symmetric, sometimes asymmetric, innermost conspicuous, slightly suprabasal, placed 2–6(–16) mm above base, marginal pair inconspicuous; midvein and secondary veins impressed adaxially and prominent abaxially, tertiary veins impressed to raised adaxially and prominent abaxially, quaternary veins raised adaxially and prominent abaxially. Mite domatia sometimes present as small holes with few stellate trichomes at point where midvein and secondary veins join. Inflorescence 4.5–10.5 × 4–10 cm, peduncle 0.6–2.2 cm long with 15–29 flowers; each inflorescence with 3–5 pairs of branches, densely tomentose, later glabrescent, usually reddish, pseudopedicel 0.3–1.3 cm long, lateral branches arising at base of main axis with several flowers; bracts 3–6 mm long, subulate, densely tomentose, persistent during anthesis, later caducous, bracteoles 1.5–2.5 mm long, subulate, densely tomentose, persistent during anthesis, later caducous. Flowers 5-merous; pedicel 0.6–1.1 mm long. Hypanthium c. 2 mm long, campanulate, free portion c. 1 mm long, external surface tomentose, mostly glandular setose, internal surface glabrous. Calyx tube 0.4–0.7 mm long; calyx lobes 1–2.1 mm long, broadly triangular, obtuse to acuminate, internal surface glabrous; calyx teeth c. 0.5 mm long, subulate. Petals 6.5–7.5 × 3.5–5 mm, slightly obovate, pink to violet, glabrous, base decurrent, apex rounded-emarginate, with a notch. Stamens 10, deflexed in 2 groups on both sides of flower at anthesis, 3 or 4 on same side as style and 6 or 7 on opposite side, deflexed backward and turning reddish to orange with age, falling together with petals. Filaments 3.7–4.7 mm long. Anthers 2.7–2.9 × c. 0.9 mm, lanceolate, flattened toward apex; connective not projecting below thecae; thecae wrinkled, with a ventral-apical pore. Ovary 3-locular, free portion ridged, apex lobulate and sunken at union with style, glabrous; placentation axile-central to basal. Style 6.5–7.5 mm long. Berries 0.8–1.2 × c. 1.2 cm, 40–44-seeded, maturing black. Seeds 1.8–2.3 mm long.

Phenology — Flowering specimens have been collected from January to May and in August and October, fruiting specimens from March to May and in September and October.

Distribution and ecology — Miconia thomasiana is endemic to Puerto Rico and the Virgin Islands ( Tortola, St. Thomas) ( Fig. 18). It grows in dry coastal scrub and forests on sandy soils or limestone hills, and in thickets on red clay over serpentine, at 0– 640 m.

Informal conservation status — Miconia thomasiana was assessed as Near Threatened (NT) by Barrios & Hamilton (2018). This species has an EOO of 6540 km 2 (within the limit for Vulnerable status under sub-criterion B1) and its AOO is 19 km 2 (within the limit for Endangered under sub-criterion B2). It is known from 19 localities representing nine locations sensu IUCN (2012), some of them included in protected areas: Sage Mountain National Park on the island of Tortola, and within Maricao State Forest, Susúa State Forest, Toro Negro State Forest and Laguna Tortuguero Natural Reserve in Puerto Rico ( Barrios & Hamilton 2018). These authors reported a decline in extent and quality of habitat and number of individuals in various locations because of development associated with urbanization and tourism, illegal farming and feral livestock on Tortola. On Puerto Rico, the threats include unsanctioned trail development, illegal fires, invasive plant species ( Casuarina equisetifolia L. and Melaleuca quinquenervia (Cav.) S. T. Blake ). Miconia thomasiana is also affected by an insect with the potential to become a damaging pest. We have no data to estimate the size of the population, even though the species seems to be locally uncommon. In the absence of additional data, we agree with the previous assessment of NT ( Barrios & Hamilton 2018).

Discussion — Miconia thomasiana is the only species of deciduous Miconia from the Greater Antilles endemic to Puerto Rico and the Virgin Islands. It shares with M. obtusa and M. lutgardae the glandular indumentum but differs from these species by the characters mentioned in the key.

In the protologue of Miconia thomasiana, Candolle (1828) mentioned a possible specimen as “ Melast. coriacea Juss. in herb. mus. Par.” (i.e. in P) but did not provide the name of the collector. We could not find any specimen of M. thomasiana in P annotated by Candolle. However, in Candolle’s personal herbarium in Geneva (G-DC) there is a specimen (G-DC 201736) without collector or collecting number but with a label annotated “ Miconia Thomasiana dC ”, another one with “ M. coriacea Juss. Antilles ” and an envelope (with fruits) annotated “ Mel. coriacea . Porto rico ” in Candolle’s handwriting (checked against http://www.ville-ge.ch/musinfo/bd/cjb/auxilium /calligraphie.php?personne=341), which coincides with the protologue. This specimen is therefore chosen as the lectotype of M. thomasiana .

The exact publication date of Miconia vernicosa is problematic because the journal (see Naudin 1851) gave the year of publication as 1851, but Stafleu & Cowan (1981: no. 6652) cited it as August 1850. This difference has no nomenclatural ramifications because the publication of M. thomasiana is from 1828; therefore, we have decided to leave the date for M. vernicosa as shown in the journal.