Myrcia marianae Staggemeier & E.Lucas, 2014

Staggemeier, Vanessa Graziele & Lucas, Eve, 2014, Morphological diagnosis of a new species in Myrcia sensu lato (Myrtaceae) from Bahia, Brazil, with molecular highlights, Phytotaxa 181 (4), pp. 229-237 : 231-235

Myrcia marianae Staggemeier & E.Lucas , sp. nov. ( Figs. 2–3 )

Type: — BRAZIL. Bahia: Una , 74 m elevation, 15°13’24’’S and 39°01’51’’W, 5 April 2012 (fr), V . G . Staggemeier & J . E . Q. Faria 764 (holotype UB!, isotypes HRCB!, IAN!, K!, RB!, UFG!) .

This species resembles Marlierea sucrei in having a raised midvein, long bracts and bracteoles, a persistent and pubescent calyx, differing through its small leaves, very long, glandular, well-developed bracts and soft, reflexed calyx lobes in fruit.

Tree to 4 m. Branches glabrous or with sparse, short hairs. Leaf blades lanceolate, 8.2–9.9 × 2.8–3.8 cm, apex attenuate, base obtuse, membranaceous with a lustrous cuticle ( Fig. 3 ); adaxial face glandular, glands slightly raised or immersed in the lamina, glabrous or with occasional sparse hairs at the base, trichomes simple; abaxial face with sparse hairs and obscure glands; midvein flattened to slightly raised adaxially, clearly raised abaxially, drying a dull brownish yellow or pale green in contrast with the lamina that dries dark green or dark greyish brown ( Fig. 2 ); marginal vein simple, 1 to 1.2 mm from the edge, 25–30 pairs of secondary veins with an inter-secondary vein between almost each pair. Fruits globose ( Figs. 3 IV – V), to 15 mm in diameter, solitary, bracteate ( Fig. 3 VIII), pedicel 0.6–1.7 long cm, puberulous in the base, trichomes usually white, occasionally pale yellow. Bracts free, lanceolate, 3.2–3.5 cm long, apex acute, pale green, glabrous, often persistent at fruiting and densely glandular ( Fig. 4 III). Bracteoles free, lanceolate, 0.6–1.0 cm long, apex acute with sparse, short hairs, glandular, occasionally persistent at fruiting ( Fig. 4 II). Fruiting calyx persistent, irregularly split ( Figs. 3 I , III, VIII), outer surface densely pubescent with long flagelliform trichomes, inner surface glabrous ( Figs. 3 III – V). Open flowers and mature fruits unknown.

Etymology: —The specific epithet honors Mariana Rocha dos Santos, a Brazilian entomologist fascinated with beetles, biogeography and evolution, studying for her PhD in Ecology and Evolution at UFG (Universidade Federal de Goiás). She passed away at the age of 25 from breast cancer.

Phenology: —Immature (early development) to well developed fruits were observed in April.

Molecular highlights: — Myrcia marianae is related to Marlierea sucrei ( Figs. 4 IV–VI) and Marlierea glabra ( Figs. 4 VII–IX). The sequences of ITS and psb A- trn H were identical for Myrcia marianae (V.G. Staggemeier, 764) and Marlierea sucrei (K. Matsumoto, 824). Sequences of Myrcia marianae for the remaining three regions differed from that accession but were identical to a second accession of Marlierea sucrei (V.G. Staggemeier, 916). Sequence difference was found between all regions of Myrcia marianae and Marlierea glabra ( Table 2).

Distribution, Habitat and Ecology: — Myrcia marianae is known only from the type collection and occurs in lowland forest from Una, Bahia ( Fig. 1 ). It is found in lowland humid forest near to the coast on sandy soil (restinga) with occasional clay deposites and a litter containing high quantities of nondecomposed leaves. This species is apparently rare and endemic and occurs in sympatry with other Myrcia sect. Aulomyrcia species [ Marlierea obversa D. Legrand (1962: 28) , Marlierea sucrei , and Myrcia tetraphylla Sobral (2010: 152) ].

Suggested conservation status: —This distinctive species is extremely rare, to now known from a single individual from Una, Bahia. During 10 years of floristic studies in the Una Biological Reserve Amorim et al. (2008) recorded 1038 plant species, of which around 18% are endemic to south Bahia and northern Espírito Santo. However, despite intense floristic studies in this region and extensive checks in the main herbarium collections, this is the first time this new taxa has been noted. Anthropic pressure in this region of Atlantic forest is high; proposed construction of an airport and two harbors nearby ( SECOM 2014a, b) could heavily impact this region’s biodiversity (Una-Ilhéus- Itacaré). Therefore, this species should be treated as “Critically Endangered” (CR) following IUCN criteria B1 a,b (i,iii) ( IUCN 2012).

Discussion and affinities: — Myrcia marianae has affinities with Marlierea sucrei and Marlierea glabra . The leaves of Myrcia marianae are the smallest among them and sepals are conspicuous, densely covered with longer trichomes than are known in other Marlierea ( Fig. 4 ). Additionally, Marlierea glabra and M. sucrei have cataphylls while Myrcia marianae has not; Marlierea sucrei and Myrcia marianae have bracts and bracteoles while Marlierea glabra does not. Moreover, the bracts are completely developed, glabrous and glandular in Myrcia marianae ( Fig. 4 III) while in Marlierea sucrei they always tear when the inflorescence is expanding. The bracts in Marlierea sucrei are densely pubescent ( Fig. 4 VI), this characteristic is the likely reason for the vernacular name “araçá-coelho” since the bracts looks like the ears of a rabbit. Marlierea sucrei has densely pubescent rachises, buds and fruits while Myrcia mariane is mostly glabrous or with sparse, short hairs on the pedicels and long hairs only at the base and apex ( Fig. 4 ). Myrcia marianae has solitary fruits ( Fig. 4 I ) while Marlierea sucrei and Marlierea glabra have developed infructescences, usually with two terminal or sub-terminal panicular rachises in Marlierea glabra and 3–5 terminal rachises in Marlierea sucrei ( Fig. 4 IV, VII).

The group that encompasses these three species is formed just by species that would traditionally be named as Marlierea Cambessèdes (clades D and E; Fig. 5 ); other groups inside Myrcia sect. Aulomyrcia contain both Marlierea and Myrcia (Staggemeier et al. 2014) . It was felt necessary here to describe this species in Myrcia , as all Marlierea species are in the process of being synonymised under Myrcia . These findings emphasize the fragile concept of Marlierea as a genus ( Lucas et al. 2011).

Figures

FIGURE 1. Location of Myrcia marianae in Una, Bahia (A), recorded in lowland sandy forest (B).

FIGURE 2. Isotype of Myrcia marianae: V.G. Staggemeier & J.E.Q. Faria 764 (holotype: UB!)

FIGURE 3. Myrcia marianae in the beginning of fruit development (I), showing tomentous simple hairs (I, III, V), glandular bracteoles (II, IV), and the irregularly splitting sepals (III, V, VIII). Immature fruits completely developed (V, VIII). Glabrous and lustrous leaves in both faces (VI, VII).

FIGURE 4. Morphological comparison among Myrcia marianae (I–III), Marlierea sucrei (IV–VI) and Marlierea glabra (VII–IX). Bracts and bracteoles in M. mariane (II–III) and M. sucrei (V–VI) and not apparent in M. glabra (VIII–IX). Longer hairs in M. marianae (II) than in M. sucrei (V) and bracts glabrous and glandular in M. marianae (III) while densely pubescent in M. sucrei (VI).

FIGURE 5. Maximum credibility tree for a reduced dataset consisting of 22 accessions of Myrteae based on combined plastid and nuclear sequences (4225bp) for the full tree including 93 taxa (Staggemeier et al. 2014). Clades are marked in different colours, and numbers above branches refer to Bayesian posterior probability/Maximum likelihood bootstrap support. Clades A-G are discussed in detail in Staggemeier et al. (2014).