Bertolonia crassicaulis Bisewski, Bacci & R. Goldenb., 2025

Bisewski, Gessica C. A., Bacci, Lucas F., Amorim, André M., Michelangeli, Fabián A. & Goldenberg, Renato, 2025, A new species of Bertolonia with thickened stems, a rare feature in Melastomataceae living in dry areas, Phytotaxa 691 (1), pp. 63-73 : 65-70

Bertolonia crassicaulis Bisewski, Bacci & R. Goldenb. , sp. nov. (Figs. 1,2)

Type: — BRAZIL. Bahia: Jequié , “Brejo Novo, topo”. 13° 56’ 56” S, 40° 6’ 43” W, 400 m elev., 7 October 2019 (fl., fr.), G. C. A. Bisewski, L. F. Bacci and A. M. A. Amorim 56 (holotype: UPCB-98210!; isotypes: CEPEC!, MBM-447734!, RB-828132!, RB-828121) .

Diagnosis:— Bertolonia crassicaulis is similar to Bertolonia maculata . Both have blades with flat surfaces, cordate bases, and sparsely ciliate margins, and the flowers have pink and apiculate petals, and yellow anthers with a triangular and introrse pore. Bertolonia crassicaulis differs by the alternate leaves (vs. opposite in B. maculata ) with light green leaf blades (vs. dark green), and the adaxial surface covered with white dots, each one topped by a caducous trichome (vs. without white dots in B. maculata ). Bertolonia crassicaulis can also be recognized by the thickened stems laying hidden in the leaf litter, absent in B. maculata .

Herbs 10–20 cm tall, terrestrial, growing in the leaf litter. Stems with two portions, one thick, 6–9 mm diam. in fresh material, 3–7 mm diam. when dry, lying parallel to the ground and covered with litter, terete, leafless, but bearing the leaf scars, and with abundant adventitious roots on its surface, the second portion aerial, erect, provided with leaves, also thick, ca. 10 mm diam. in fresh material, 5.8–7.7 mm diam. when dry, and sometimes with a few adventitious roots, these two thick portions linked by a short, thin section 3–5 mm diam. in fresh material, 2.5–3.5 mm diam. when dry, the stem in general densely glandulose-punctate (trichomes <0.1 mm long), sparsely glandulose-villose (trichomes 2–4 mm long) and densely glandulose-villose near the stem apex (trichomes 2–3.5 mm long). Leaves alternate; petioles 1.8–4.6 cm long, half-terete with a central groove, moderately to densely glandulose-punctate, densely glandulose-villose when young (trichomes 2–3.5 mm long) and sparsely glandulose-villose when old (trichomes 1–2 mm long); blades 7–10 × 4.8–6.2 cm, slightly bullate, widely ovate or elliptic, base cordate, apex acuminate or mucronate, margins entire, revolute, sparsely ciliate, adaxial surface light green, with sparse white dots, each one topped by a caducous trichome, sparsely glandulose-punctate and sparsely strigose (trichomes 0.3–0.7 mm long), abaxial surface light green, moderately glandulose-punctate, and sparsely glandulose-villose (mainly along the veins; trichomes 0.5–1 mm long), main veins 5, plus one pair that does not reach the leaf apex, light pink on abaxial surface, basal. Inflorescence terminal, 4.3–12 cm long, peduncle moderately glandulose-punctate and sparsely glandulose-villose (trichomes ca. 1 mm long); bracts not seen; bracteoles 0.7–2 mm long, sessile, lanceolate, apex acute, both surfaces glandulose-punctate. Flowers 5-merous, on pedicels ca. 1 mm long, densely glandulose-punctate. Hypanthium vinaceous, 2.7– 3.4 × 2–2.8 mm, obconic, costate, densely glandulose-punctate and sparsely glandulose-villose (trichomes ca. 1 mm long). Calyx membranaceous, sepals not divided into an inner lamina and dorsal projections, ovate to widely ovate, apex acute, margins entire, ciliate, glandulose-villose, both surfaces glandulose-punctate. Petals 3.4–6.5 × 3.8–4.3 mm, light pink, elliptic to ovate, base cuneate, apex apiculate (ca. 0.2 mm long), the apiculum ending in a glandular trichome, margins entire, revolute, both surfaces glabrous, papillose. Stamens 10, arranged unilaterally, isomorphic, 3.5–4 mm long; filaments 1.8–2.5 mm long; thecae yellow, ca. 1.8 mm long, lanceolate, smooth to slightly undulate, pore triangular, introrse; connective shortly prolonged (less than 0.2 mm), dorsally thickened, unappendaged. Ovary free, glabrous, 3-locular, placentation axillary; style 3.5–4 mm long, curved at the apex, slightly capitate, glabrous. Capsules obtriquetrous (bertolonidium-type, following Baumgratz 1983 –1985), 0.4–0.6 × 0.8–1 cm, moderately to densely glandulose-punctate. Seeds ca. 1 × 0.5 mm, obovate or oblong-obovate, the testa tuberculate at the dorsal angles.

Phenology:— Bertolonia crassicaulis was collected with flowers and fruits in October and February.

Distribution and ecology: — Bertolonia crassicaulis has been collected five times at the same locality ( Fig. 3 ), a private property called “Brejo Novo” farm, in the municipality of Jequié. It is in a transition zone between the Atlantic Forest and the Caatinga domains, recognized as submontane deciduous seasonal forest (“Floresta Estacional Decidual Submontana”) by IBGE (2012). These deciduous forests are known as “mata de cipó” in southeastern Bahia. The “Mata de cipó” vegetation plays a crucial role as natural corridors connecting the Atlantic Forest and the Caatinga, and harbor a remarkable diversity of species, including some exclusive to the Atlantic region ( Veloso et al. 1991). The “mata de cipó” has different local variants, such as the “cold forest”, where larger trees dominate, and the “shrub forest”, characterized by smaller plants in both height and diameter ( IBGE 2012). It is important to highlight that these habitats, which once extended throughout the southern plateau of Bahia, are undergoing significant transformations due to human intervention ( Veloso et al. 1991; IBGE 2012). Precipitation data for the region where B. crassicaulis occurs indicate that it is a drier region, with an average annual rainfall of 670 mm. Most of the rainfall, accounting for 81% of the yearly total, occurs between November and April with a peak in December ( Dourado et al. 2013). Thus, Bertolonia crassicaulis can be considered a microendemic, the same distribution pattern previously observed in several species of the genus ( Bacci et al. 2018; 2020; 2022b; Bisewski et al. 2022).

Conservation status:—This species has an AOO of 8 km ² and it occurs only in one locality, so it is not possible to calculate its Extent of Occurrence (EOO). Based on its restricted distribution and the rapid degradation of the type of forests it inhabits, it should be classified as “Critically Endangered” (CR), following IUCN (2022) categories, under criterion B2ab (ii, iii).

Etymology: —The specific epithet refers to the thick stem, one of the diagnostic features of the new species. “Crassus” means thick, and “caulis” refers to the stem.

Paratypes: — BRAZIL. Bahia: Jequié , “Fazenda Brejo Novo, entre 300 e 400 do lado direito”, 13° 56’ 41.4” S, 40° 6’ 33.9” W, 713 m, 4 October 2003, A. F. Souza 3 ( HUESB, UPCB!) ; “ Fazenda Brejo Novo a 10.5 km da Av. Otávio Mangabeira pela Exupério Miranda no Bairro do Mandacaru ”, 13° 33’ 50.76” S, 40° 37’ 58.8” W, 713 m, 1 April 2004, G. E. L. Macedo 678 ( HUESB) ; “ Fazenda Brejo Novo, a 10,5 Km da Av. Otávio Mangabeira entrando pela Av. Exupério Miranda no Bairro do Mandacarú ”, 13° 33’ 50.76” S, 40° 37’ 58.8” W, 617–750 m, 24 April 2004, G. E. L. Macedo 801 ( HUESB) ; “10.5 Km ao S de Mandacaru (junção Rod. do estádio/Rod. para Jequié) Rod. P / Serra dos Brejos.”, 13° 56’ 37” S, 40° 6’ 40” W, 575–650 m, 5 February 2004, W. W. Thomas 13829 ( CEPEC!) .

Remarks: —The two morphologically different portions of the stems described above for B. crassicaulis may be explained by their growth cycle in a strongly seasonal habitat. The erect, leafy portion of the stem grows during the rainy season but dehydrates (at least partially) during the transition to the dry season, then loses its leaves and becomes prostrate. These leafless, semi-turgid stems become covered with litter and survive through the dry season hidden in litter. In the next rainy season, a meristem gives way to another erect stem that also thickens and stores water but keeps the leaves until the end of the season. These stems of B. crassicaulis are remarkably thick due to a robust medullary parenchyma that seems to be related to water storage (Bisewski et al. in prep.), which in turn are probably related to adaptations to environments that are drier than the ones where most species of Bertolonia are found (Bacci et al. 2022).

Another feature of this species is that its flowers seem to be automatically self-pollinated ( Passos et al. 2022a, based on material provided by the authors). In this delayed selfing mechanism (“pollen tube shower”, as described by Passos et al. 2022b), the petals return, after anthesis, to a position that is similar to that in the bud. By moving like that, the petals push the anthers towards the style, and because the anther pores and the stigma are at the same level, there is contact between them, and the pollen grains start germinating still inside the anthers. The pollen tubes then grow towards the stigma, penetrate it and allow the flowers to self-pollinate ( Passos et al. 2022b).

Belonging to the Bertolonia maculata complex ( Baumgratz 1990; Bisewski et al. 2022), B. crassicaulis is similar to B. maculata , B. marmorata and B. carmoi . All share the stems, petioles, leaves, and hypanthium covered with sessile and short-stalked glands (<0.1 mm long), leaves widely elliptic to ovate, with a cordate base, and petals pink, elliptic, with a cuneate base. Bertolonia crassicaulis differs from B. maculata by the characters presented in the diagnosis. Since B. maculata , B. marmorata , and B. carmoi are very similar, the differences between B. crassicaulis and B. marmorata and B. carmoi repeat the ones already listed in the diagnosis: alternate leaves (vs. opposite in B. marmorata and B. carmoi ) with leaf blades light green on both surfaces, main veins light pink on the abaxial surface (vs. dark green on both surfaces, with main veins vinaceous in both species), leaf blades covered by sparse white dots, each one topped by a caducous trichome (vs. lacking white dots, and covered with long-stalked glands throughout the entire leaf blade in B. marmorata and only short-stalked glands in B. carmoi ). Additionally, in B. crassicaulis , the anthers have an unappendaged connective that is dorsally thickened (vs. two small dorsal lobes in B. carmoi ). For a detailed account of the differences between these four species, see Table 1.

The distribution of B. crassicaulis is not overlapping and more restricted than that of the other species in the complex. Bertolonia carmoi is also endemic to Bahia, but it occurs in 25 municipalities, while B. crassicaulis was collected in only one locality (see Fig. 3 ). Bertolonia maculata and B. marmorata are more widely distributed: the first occurring in Bahia but also in the state of Espírito Santo, and the second in Bahia plus Alagoas and Pernambuco ( Bisewski et al. 2022; Baumgratz 2024). Bertolonia crassicaulis grows in a transitional zone between the Atlantic Forest and Caatinga (see introduction), under drier climatic conditions than the other three species. These are all found in the more humid areas covered with Atlantic Forest ( Bisewski et al. 2022; Baumgratz 2024).

In addition to the species from the B. maculata complex, B. crassicaulis also resembles Bertolonia alternifolia Baumgratz, Amorim & A.B. Jardim (in Baumgratz et al. 2011: 273) and Bertolonia michelangeliana Bacci & R. Goldenberg (in Bacci et al. 2017: 1670) because of their alternate leaves. This character is very uncommon in the family, and it is usually related to the suppression of one of the leaves in an opposite pair ( Judd et al. 2022). However, the alternate phyllotaxis in Bertolonia still needs further investigation, since there is no trace of a suppressed leaf opposite to the regular ones ( Baumgratz et al. 2011; Judd et al. 2022). Bertolonia crassicaulis differs by having stems with thickened and discontinuous portions (vs. continuously non-thickened stems in B. alternifolia and B. michelangeliana ) and anthers with an introrse pore (vs. anthers with an extrorse pore in B. alternifolia and B. michelangeliana ).

Another aspect that deserves further investigation is the leaves with regular, sparse, white dots or, alternatively, “ocelli” or “maculae”, such as the ones found in B. crassicaulis ( Fig. 1-B ), and Bertolonia margaritacea Naudin (1867: 165 ; Martins et. al 2009, Baumgratz 2024), and some Old-World genera ( Chen et al. 2016). These dots develop under a trichome that is already present when the leaves are young and still extending (GCAB, LFB, RG, pers. obs.; Chen et al. 2016). In B. margaritacea , these white dots may or may not occur, and the variation can be found within individuals in a population, or even in different leaves in the same individual (GCAB, JFB, RG, pers. obs.). Bertolonia crassicaulis can be distinguished from B. margaritacea by the light green leaves on both surfaces (vs. dark green on the adaxial surface and vinaceous on the abaxial in B. margaritacea ), and pink petals (vs. white petals in B. margaritacea ).

Figures

FIGURE 1. Bertolonia crassicaulis. A. Habit,Arrows indicating the aerial portion of the stem (blue) and the portion that grows parallel to the ground, covered by litter (red). B. Leaf blade, adaxial surface. C. Leaf base, abaxial surface. D. Trichomes on the adaxial leaf surface, with a white dot underneath (arrows). E. Inflorescence. F. Flower, top view. G. Stamen, lateral view H.Anther apex, ventral view. Photos: A by Lucas de Freitas Bacci; B–H by Gessica Bisewski.

FIGURE 3. Distribution map of Bertolonia crassicaulis.