Synopsis of Martinella Baill. (Bignonieae, Bignoniaceae), with the description of a new species from the Atlantic Forest of Brazil

Abstract Martinella has traditionally included two species, Martinella iquitoensis and Martinella obovata, that are characterized by the presence of interpetiolar ridges surrounding the stems and minute prophylls of the axillary buds. A third species, Martinella insignis, is here described as new, illustrated and compared to other species in the genus. Martinella insignis is the first record of the genus in the Atlantic Forest of Brazil, and differs from other species of Martinella by the yellow corolla (vs. red to dark purple) and 5-lobed calices (vs. 2–4-lobed).


Introduction
Martinella Baill. (1888) is strongly supported as monophyletic by molecular data (Lohmann 2006). Species of Martinella are well distinguished by the combination of minute triangular prophylls of the axillary buds, an interpetiolar ridge surrounding the stem, and bilobed or (2-)4-parted calyces (Lohmann and Taylor 2014); the latter two being considered putative synapomorphies of the genus (Lohmann 2006;Lohmann and Taylor 2014). In addition to these features, the basal tubular portion of the corolla is slightly longer and much narrower than the calyx, leaving it loose within the calyx, while the upper portion of the corolla tube is abruptly infl ated and campanulate, up to four times wider than the tubular portion (Fig. 1D). Gentry (1974) described this corolla morphology plus the red to purple color as a Martinella-type fl ower, and hypothesized that this fl ower was associated with pollination by hummingbirds. Th e only exception to Gentry's fl oral description is the position of the anthers (exserted or subexserted), which are always included in Martinella.
Th e genus as currently circumscribed includes two species of neotropical lianas (Lohmann and Ulloa Ulloa 2013;Lohmann and Taylor 2014): Martinella iquitoensis A.Samp., restricted to the Amazon basin (Brazil, Colombia, Ecuador, Peru and Venezuela) and Martinella obovata (Kunth) Bureau & K.Schum., ranging from Central America to Northern South America and the Amazon basin . A third morphologically distinct species of Martinella was discovered during fi eldwork in the Atlantic Forest of Brazil; its description here extends the known range of this genus. Here we present an overview of the genus and the separation of its species.

Materials and methods
Th is work is based on the study of herbarium collections of Martinella deposited in CEPEC, MBM, MBML, MO, NY, RB, SPF and VIES (herbarium acronyms follow Th iers 2013). Morphological descriptions are based on dried specimens, and follow the terminology of Radford et al. (1974). Th e parentheses in the descriptions indicate rare conditions. Micrographs of selected structures were made using a stereomicroscope and digitally processed through focus stacking. For the species distribution map, the geographical data of M. insignis were combined with those used in  and plotted over a digital elevation model (GTOPO 30, available from the U.S. Geological Survey). Lianas. Roots with tuberous portions. Branches terete, glabrous or puberulous, with trichomes simple or stipitate-glandular, with continuous interpetiolar ridges, without interpetiolar glands; prophylls minute, triangular, glabrous or puberulous. Leaves 3-foliolate or 2-with the terminal leafl et modifi ed into a simple or trifi d tendril; leafets membranous to coriaceous, margins entire (sinuate), with or without mite-domatia, glabrous to puberulous, with glands on adaxial surface. Infl orescences axillary, arranged in racemes, panicles, thyrses or compound dichasia. Flowers with calyx tubular (campanulate), bilobed, irregularly 2-4-lobed, or 5-lobed, with lobes rounded or aristate, membranous, with few scattered glands; corolla deep purple, red or yellow, tubular in the basal portion and campanulate in the upper part, straight to weakly curved, membranous, glabrous outside, glabrous inside except with few glandular trichomes at stamen insertion; stamens included, glabrous, pollen in monads; ovary terete, smooth, glabrous or lepidote, with a single series of ovules on each placenta, style glabrous, stigma rhombic, glabrous. Capsules drying dark brown, linear, fl attened, smooth, glabrous or puberulous, with calyx caducous; seeds oblong, winged, with wings opaque.
Martinella comprises three species, distributed from Mexico to eastern Brazil. Th e main features that distinguish the species are summarized in Table 1 and outlined in the key below. Diagnosis. Martinella insignis diff ers from M. iquitoensis and M. obovata by its 5-lobed calyces and yellow corollas, in contrast to 2-4-lobed calyces and dark purple to red corollas in these other species (Table 1).
Distribution and habitat. Martinella insignis is restricted to the northern portion of the Brazilian Atlantic Forest, occurring predominantly in areas with sandy soils (Fig. 3).
Etymology. Th e species epithet means remarkable or clearly distinguishable. Th is epithet was probably selected by Alwyn Gentry as reference to the contrasting fl oral color among species of Martinella .
Phenology. Flowering specimens were collected between September and February and fruiting collections in January, September and November.
Conservation status. Th is species is considered Data Defi cient [DD] according to IUCN Standards and Petitions Subcommittee (2014) since this taxon is only known from very few specimens, with little information about its distribution and abundance. Further fi eld studies are needed so that its conservation status can be properly documented.  Gentry (1977Gentry ( , 1982Gentry ( , 2009   Discussion. Martinella insignis is the fi rst species of Martinella found in the Atlantic Forest of Brazil. Th is new species clearly belongs to Martinella based on its prophylls, the continuous interpetiolar ridges and the corolla shape. However, M. insignis can be distinguished by the membranous leafl ets, 5-lobed aristate calyces, and yellow corollas. In addition, M. insignis also has pocket-shaped leaf domatia (Fig. 2C) and a puberulous indument of glandular stipitate trichomes that covers almost all organs, with variable density (Fig. 2E-F). Th ese trichomes may also be found in M. obovata and a few other species in Bignonieae, and are typically formed by a multicellular secretory head, supported by a uniseriate stalk (Nogueira et al 2013). Only corollas and fruits lack these; the corollas are glabrous, and fruits have simple, deciduous trichomes (Fig. 2G). Similar to the other species, the root system of M. insignis has unusual tuberous portions (Fig. 2D) that might represent an adaptation to the sandy soils, by accumulating water. However, the anatomical structure and function of these are yet unknown. Alwyn Gentry had already noted this new taxon, and had proposed the epithet "insignis" in sched.; his earlier fi ndings are here accredited.

Conservation status.
Martinella iquitoensis is distributed geographically through an area that is < 2000 km 2 , with seven Rapoport (1982) sub-populations known to date and ≥ 20% of its known individuals occurring outside Protected Areas, making it susceptible to the current reduction and degradation of its habitat. Th erefore, this species is here considered as Vulnerable [VU B2ab(ii,iii)] according to the IUCN criteria (IUCN 2012;IUCN Standards and Petitions Subcommittee 2014).
Discussion. Th is species was distinguished by Sampaio from M. obovata based on the corolla color and size, leafl et texture and size, tendril type, and calyx indument. However these characters have proven to be fairly variable, especially in M. obovata , leading to morphological overlap between those taxa. Th e lack of a clear morphological discontinuity combined with the sympatric distributions, make these species hard to separate. Moreover, the diffi culty in delimitating these two species can be observed in the few treatments that dealt with those species, which is particularly evident in the contrasting species keys presented (Sampaio 1935;MacBride 1961;Gentry 1982;Gentry 2009).
A character that might help telling these species apart is the infl orescence structure: a thyrse or panicle in M. iquitoensis versus a raceme in M. obovata . Th is character, combined with leafl et base, is here proposed as diagnostic for each species; however, the examination of additional material is necessary to validate its usefulness and consistency. Distribution and habitat. Th is species is found from Central America and the Antilles through northern South America to the southern Amazon basin, in the Antilles, Belize, Bolivia, Brazil, Colombia, Costa Rica, Ecuador, French Guiana, Guatemala, Guyana, Honduras, Mexico, Panama, Peru, Surinam, and Venezuela, in diff erent soil types and habitats (Lohmann and Taylor 2014; Fig 3).

Martinella obovata
Conservation status. Martinella obovata is distributed geographically through an area that is ≥ 2000 km 2 , with < 20% of its known individuals occurring outside Protected Areas, and seventy-two Rapoport (1982) sub-populations known to date. Th erefore, this species is here considered as Least Concern [LC] according to the IUCN criteria (IUCN 2012; IUCN Standards and Petitions Subcommittee 2014).
Discussion. Th is species is the most variable and has the largest distribution in the genus (Central America and Caribbean throughout Amazon basin). Such variation is product of its phenotypic plasticity and wide ecological range, and is responsible for making this species hard to be distinguished from M. iquitoensis (as discussed above). Nonetheless, this high variation may also be seen as an evidence of a species complex, in which case, additional studies would be needed. For a complete list of synonyms see Gentry (1977).