Microlicia piauiensis R.Pacifico & Almeda, 2022

Pacifico, Ricardo & Almeda, Frank, 2022, A new species of Microlicia (Melastomataceae) endemic to Serra das Confusões expands the range of the genus to Piauí, Brazil, Phytotaxa 548 (1), pp. 73-81 : 74-78

Microlicia piauiensis R.Pacifico & Almeda , sp. nov. ( Figs. 1 , 2 A–E )

Type:— BRAZIL. Piauí: Mun. Caracol, povoado de Bom Sucesso, próximo a caverna (grotão), 9º13’13”S, 43º29’19”W, 597 m, 17 July 2011, fl. fr., E. Melo 10101 (holotype: HUEFS!; isotypes: CAS!, HVASF!, RB!) .

Diagnosis:— Microlicia piauiensis can be recognized by its branchlets, leaves and hypanthia that are glandular-punctate and covered with gland-tipped trichomes 0.2–0.4 mm long, leaves on short petioles 0.1–0.3 mm long, revolute leaf margins, oblong calyx lobes 2–2.5 mm long, magenta petals that are yellow at the base, and isomorphic stamens with small ventral appendages at the base of the pedoconnectives.

Densely branched erect shrubs ca. 0.5–1.6 m tall. Branchlets quadrangular, glandular-punctate and sparsely to densely covered with gland-tipped trichomes 0.2–0.4 mm long, internodes unwinged, nodes with clusters of longer glandtipped trichomes 0.4–0.7 mm long; old branches rounded with bark that peels away with age. Leaves on rectangular petioles 0.1–0.3 mm long, 0.3–0.5 mm wide, ascending to imbricate, the margins revolute; blades 3–9 × 0.8–2 mm, narrowly oblong to lanceolate, papyraceous, surfaces concolored and vivid green (when fresh), the adaxial surface becoming pale brown (when dry), base truncate, margin entire, apex rounded, both surfaces glandular-punctate and densely covered with gland-tipped trichomes 0.1–0.3 mm long, the adaxial surface eventually becoming glabrescent with age; 1-nerved, the vein impressed on the adaxial surface and prominent on the abaxial surface. Flowers 5 (–6)- merous on short pedicels 0.4–0.6 mm long, solitary or clustered at the apex of the branches; hypanthia (at anthesis) 2.8–3.3 long, 2.5– 3 mm wide at the torus, campanulate, reddish to pale brown (when dry), externally glandularpunctate and covered with gland-tipped trichomes 0.1–0.3 mm long; calyx tubes 0.2–0.4 mm long; calyx lobes (at anthesis) 2–2.5 mm long, 0.8–1.0 mm wide at the base, oblong, pale brown (when dry), margin entire, apex acuminate, adaxially and abaxially with an indumentum like that of the hypanthia; petals 4.8–5 × 2.7–3 mm, obovate, magenta with a yellow base, margin entire, apex acute, both surfaces glabrous; stamens 10(–12), isomorphic; filaments 2.6–3.1 mm long, magenta with a yellow base, connectives ventrally prolonged 0.8–1.1 mm below the thecae, magenta flushed with yellow, the short appendages up to 0.3 mm long, yellow, apex emarginate to bilobate, thecae 1.8–2 mm long (excluding rostra), linear, externally smooth (tetrasporangiate), yellow, rostra 0.1–0.2 mm long, white, the circular pores ca. 0.1 mm wide, ventrally inclined; ovary ca. 2 × 1.8 mm, subglobose, superior, glabrous, 3–4-locular; styles ca. 7 mm long, magenta with a yellow base, stigmas punctiform. Capsules 3–4 × 3–3.5 mm (when mature), reddish (when fresh) becoming brown (when dry), ovoid, initially enveloped by the hypanthia and constricted calyx tubes (ca. 0.4 mm long), then rupturing and flaking away with age, dehiscing from the apex to the base, columellas deciduous. Seeds ca. 1.2 × 0.4 mm long, oblong to somewhat L-shaped, the raphal zone nearly circular and ca. 1/3 the length of the seed, the testa foveolate-reticulate, yellow.

Additional Specimens Examined (Paratypes):— BRAZIL. Piauí:Mun.Caracol,Serra das Confusões, sobre pedras, 6 May 1980, fl. fr., A. Fernandes s.n. ( EAC 8708-online image!), Serra das Confusões , carrasco, 19 November 1981, fl. fr., A. Fernandes & E. Nunes s.n. (EAC10932-online image!, UPCB 74673!); Parque Nacional Serra das Confusões , Serra das Confusões propriamente dita, lajedo de acesso à gruta Riacho do Boi, 9º13’12.3”S, 43º29’21.9”W, 580 m, 9 December 2011, fr., J.A. Siqueira-Filho 2632 et al. ( HUEFS!, HVASF-online image!). Mun. Guaribas, Serra da Água Brava, 2 km do povoado de Água Branca, 5 km do limite do Parque Nacional da Serra das Confusões, 690 m, caatinga sobre afloramentos rochosos, 9º14’42”S, 43º32’14”W, 690 m, 17 June 2007, fl. fr., G. Martinelli 16130 & M.A. Moraes ( MBM!, RB-online image!); Parque Nacional da Serra das Confusões, Toca do Pingo do Véio , 9º01’33.54”S, 43º43’11.24”W, 431 m, 21 June 2013, fl. fr., J.A. Siqueira Filho 3027 et al. ( HUEFS!, HVASF-online image!) .

Distribution and Habitat:— Apparently endemic to Serra das Confusões National Park, Caracol and Guaribas municipalities, southern Piauí state, Brazil ( Figure 3 ). Microlicia piauiensis grows on rocky outcrops surrounded by Cerrado and/or Caatinga vegetation, or in transitions between them (Carrasco), on sites exposed to full sun at elevations of 431– 690 m. The Serra das Confusões National Park was created by federal decree in 1998. It encompasses ca. 823,837 hectares of relatively flat terrain with sandstone plateaus and adjacent depressions of the Parnaíba depression ( IBAMA 2003, BRAZIL 2010) ( Fig. 2F ). Like Serra da Capivara National Park, a UNESCO World Heritage site just east of Serra das Confusões National Park in Piauí state, these parks collectively exhibit one of the most impressive expanses of ruiniform landscapes carved on sandstone ( Mutzenberg et al. 2015).

Phenology:— Collected flowering in May, June, July, November, and fruiting in May, June, July, November and December.

Pollination:— According to the label of J.A. Siqueira Filho 3027 et al. (HUEFS) and a photographic record, the stingless bee Frieseomelitta varia Lepeletier (1836: 433) is an effective pollinator of Microlicia piauiensis .

Informal Conservation Status Assessment:— Microlicia piauiensis is known from only six collections, four of which are georeferenced. The EOO and AOO estimated with GeoCAT are 92.715 km 2 and 12 km 2, respectively. These calculations would support an Endangered (EN) conservation status if criterion B of IUCN (2019) is applied: B1ac(iv). All collections with coordinates come from the southern and central sections of the Serra das Confusões National Park where M. piauiensis is afforded some protection.

Notes:— Microlicia piauiensis was initially confused with Marcetia taxifolia Saint-Hilaire in Humboldt & Bonpland (1823: 150) Candolle (1828: 124) ( Marcetieae ), a widespread species that ranges through several Brazilian states (Alagoas, Bahia, Ceará, Goiás, Paraíba, Paraná, Pernambuco, Roraima and Sergipe) northward to Guyana, Venezuela, and Colombia ( Martins 1989; Santos et al. 2020). Marcetia taxifolia shares with Microlicia piauiensis a much-branched habit, the indumentum of gland-tipped trichomes covering branchlets, leaves and hypanthia, and revolute leaf margins. The gross morphological similarity between Microlicia piauiensis and Marcetia taxifolia is probably a case of convergent evolution since these species grow in similar environments. They belong to different tribes and are allopatric. Microlicia piauiensis can be readily distinguished from all species of Marcetia by its 5(–6)- merous flowers (vs. 4-merous), stamens with connectives that are ventrally prolonged (vs. not prolonged) and elongate seeds (vs. cochleate) ( Martins 1989). No species of Marcetia have been reported for the state of Piauí ( Santos et al. 2020).

In northeastern Brazil, the Chapada Diamantina, Bahia state, is the nearest region to the Serra das Confusões that is rich in species of Microlicia (ca. 60 spp.; Romero et al. 2020). Therefore, probable relatives of M. piauiensis could potentially grow in Bahia. Using the multi-access key of Microlicia in Bahia ( Woodgyer 2005), we obtained the code BDGJNQTVah, which puts M. piauiensis close to M. isostemon and M. subalata . Both M. isostemon and M. subalata have isomorphic stamens and are endemic to Pico das Almas, in Chapada Diamantina ( Wurdack 1983) , where they occur at much higher elevations (1,400 –1,900 m; Woodgyer & Lughadha 1995) than M. piauiensis . Among other features, Microlicia piauiensis differs from both by its branches, leaves and hypanthia that are glandular-punctate and covered with gland-tipped trichomes (vs. only glandular-punctate), shorter petioles 0.1–0.3 mm long (vs. 0.5– 0.7 in M. isostemon ; 0.6–1 in M. subalata ), revolute leaf margins (vs. flat) and distinct ventral appendages on the pedoconnectives (vs. unappendaged in M. isostemon and M. subalata ). Additional comparative morphological features among M. piauiensis , M. isostemon and M. subalata are provided in Table 1 .

At least four species and one variety of Microlicia s.l. were reported for Piauí in their protologues and/or type specimens: Microlicia chloracea Naudin (1849: 252) [= Microlicia insignis Chamisso (1834: 388) ], Chaetostoma gardneri Triana (1872: 25) [= Microlicia baumgratziana A.B. Martins & Koschnitzke in Koschnitzke & Martins (2007: 473)], Microlicia hirsutissima Naudin (1845: 182) [= Microlicia vestita Schrank & Martius ex Candolle (1828: 119) ], Microlicia luetzelburgii Markgraf (1927: 45) and Microlicia euphorbioides var. macrocarpa Cogniaux (1883: 98) . Information on the label of the type of M. luetzelburgii (Luetzelburg 79 at M) makes it clear that its description was based on a specimen from Bahia, where it is endemic ( Romero et al. 2020). We previously included Piauí in a distribution map of M. luetzelburgii based on the misleading information in the protologue ( Almeda & Pacifico 2018). The remaining records were also based on specimens collected more than a century ago, but probably within the state of Goiás (see Romero et al. 2020). Therefore, Microlicia piauiensis is the first confirmed record of the genus in Piauí state.

The flora of the Serra das Confusões is still poorly known. A total of 635 species were recognized in a preliminary checklist of vascular plants, with Melastomataceae as the third richest family ( Fernandez et al. 2011). Thyrsacanthus microphyllus A. Côrtes & Rapini in Côrtes et al. (2010: 967) ( Acanthaceae ), Paepalanthus magistrae Sano, F.N.Costa, Trovó & Echtern. in Sano et al. (2015: 299) ( Eriocaulaceae ), Mcvaughia piauhiensis R.F.Almeida & Guesdon in Almeida et al. (2019: 59) ( Malpighiaceae ), Qualea insignis G.H.Shimizu, D.J.P.Gonç., F. França & K.Yamam. in Shimizu et al. (2016: 263) ( Vochysiaceae ), and Sticherus salinoi L.V.Lima in Lima & Salino (2018: 80) ( Gleicheniaceae ) were recently described. Like M. piauiensis , all of these species are apparently restricted to the Serra das Confusões. Increased sampling in the region will probably result in the discovery of other taxonomic novelties.

Figures

FIGURE 1. Microlicia piauiensis, images of dried specimens. A. Habit. B. Apical branch. C. Basal branch with corky bark peeling away. D. Leaf abaxial surface. E. Leaf adaxial surface. F. Floral bud. G. Petal. H. Stamen (profile view). I. Capsule. J. Seed. Photos taken from the holotype. Scale bars: A: 2 cm; B-C: 4 mm; D-J: 2 mm.

FIGURE 2. Microlicia piauiensis, photos of living specimens and type locality. A. Habit of a fruiting specimen. B. Close-up of a 3-locular capsule. C. Close-up of a 4-locular capsule. D. Flowering branch. E. Frieseomelitta varia (Apidae) pollinating a flower. F. Landscape with rocky sandstone outcrops at the Serra das Confusões. Photos A–E by José Alves Siqueira Filho, F by Antonio Nogueira. Voucher specimens:A–C, J.A. Siqueira Filho 2632 et al. (HVASF); D–E, J.A. Siqueira Filho 3027 et al. (HVASF).

FIGURE 3. A. Areas of endemism (AEs) of Lavoisiereae and the distribution of Microlicia piauiensis. The AEs were identified by Pacifico et al. (2020a) using endemicity analysis and a grid of 1º degree cells. For overlapping AEs, only those with higher endemicity scores are shown. B. Distribution of Microlicia piauensis in southern Piauí, within the boundaries of the Serra das Confusões National Park (outlined in blue).