An updated synopsis of Tanaecium (Bignonieae, Bignoniaceae)

Abstract Tanaecium Sw. emend L.G. Lohmann (Bignonieae, Bignoniaceae) is a genus of Neotropical lianas that is morphologically variable, especially in floral features. The genus is distributed from Mexico and the Antilles to Argentina, and centered in Amazonia. Here, we present an updated overview for Tanaecium that recognizes 21 species within the genus. Species delimitation was based on a detailed analysis of protologues and herbarium specimens, including type collections of all taxa. We present a detailed description for the genus and a key for the identification of all species. For each of the 21 species recognized, we present information on the nomenclature, phenology, habitat, distribution, and taxonomic notes. Furthermore, Spathicalyx kuhlmannii J.C. Gomes is transferred into Tanaecium kuhlmannii (J.C. Gomes) Frazão & L.G. Lohmann. A lectotype is proposed for Tanaecium crucigerum Seem.


Introduction
Tanaecium Sw. emend L.G.Lohmann is a monophyletic genus, well supported by molecular characters (Frazão and Lohmann 2018), as well as by subulate and/or bromeliad-like prophylls of the axillary buds, a putative morphological synapomorphy (Lohmann and Taylor 2014). Species of the genus are lianas or shrubs distributed from Mexico and the Antilles to Argentina (Lohmann and Taylor 2014;Pace et al. 2016;Frazão and Lohmann 2018;Kaehler et al. 2019). The genus is centered in Amazonia, where 11 species occur (Lohmann and Taylor 2014;Frazão and Lohmann 2018;Kaehler et al. 2019). While some species show disjunct distributions (e.g., Tan-PY, FCQ, QCNE, QCA, NY, US, MO, A, and F. Furthermore, images of specimens from AAU, B, BR, COL, G, K, L, M, and P were accessed online through Jstor Global Plants (2019) or the online database of individual herbaria. All protologues were consulted in the Peter Raven Library (Missouri Botanical Garden) or using the online database of BHL (2019). Morphological terminology used here follows Hickey (1974) for leaf venation, Radford (1986) for leaf morphology, Weberling (1989) for inflorescence morphology, Gomes-Silva (2009) for leaflet mite-domatia, Nogueira et al. (2013) for trichomes, and Lohmann and Taylor (2014) for prophyll morphology and other morphological traits. Phenology is based on data gathered from herbarium specimens. Distributions are based in data gathered from herbarium specimens and information provided in Lohmann and Taylor (2014). Lianas or shrubs, without dimorphic juvenile growth; stems with four phloem wedges in cross section (without in T. tetramerum), solid (hollow in T. apiculatum); branchlets terete or tetragonal, without ridges, with or without striation, without peeling epidermis (present in T. decorticans), sparse or dense lenticels, with or without simple non-glandular trichomes (dendritic non-glandular trichomes in T. xanthophyllum); interpetiolar region with or without fields of patelliform glandular trichomes, and discontinuous interpetiolar ridges (sometimes continuous); prophylls of the axillary buds bromeliad-like and/or subulate (minute and triangular or foliaceous), without patelliform glandular trichomes (present in T. selloi). Leaves 2-3-foliolate (sometimes simple in T. tetramerum) with the terminal leaflet modified into a simple or trifid tendril (sometimes bifid in T. pyramidatum); leaflets without cartilaginous margin (present in T. apiculatum), secondary venation brochidodromous (craspedodromous in T. parviflorum). Inflorescence in a fascicule, raceme, thyrse or compound thyrse, terminal (sometimes axillary); calyx campanulate, cupular or tubular, bilabiate or truncate (sometimes spathaceous); corolla magenta, pink, yellow, pale yellow or white, infundibular or wide infundibular (campanulate or hypocrateriform), zygomorphic (actinomorphic in T. tetramerum), pentamerous (tetramerous in T. tetramerum), aestivation imbricate; androecium didynamous, pollen in monads, 3-colpate, psilate and microperforate (inaperturate and coarse-reticulate in T. apiculatum); nectar disk well-developed; gynoecium with ovary without stipe at the base, with one, two, or many series of ovules in each placenta, stigma papilose. Capsule elliptic or linear (linear-oblong), with or without lenticels, calyx caducous (persistent); seeds winged or wingless, with body smooth and glabrous, winged hyaline or opaque, linear, wingless corky or woody and rounded.
Key to species of Tanaecium Habitat and distribution. Tanaecium affine is known from humid forests with rich soils, although it has been collected in primary and secondary forests with lateritic soil in Peru (Loreto, Mayanas). It is native from Bolivia (La Paz), Colombia (Antioquia, Boyaca), Ecuador (Napo, Pastaza, Sucumbíos), and Peru (Amazonas, Junín, Loreto, Pasco, Puno). Phenology. Flowering: February to April, September and November; fruiting: February to December.
Notes. This species is morphologically similar to Fridericia florida but differs by the bilabiate calyces, stems with conspicuous patelliform trichomes in the interpetiolar region, and occurrence in rich soils (Gentry 1992). In addition, T. affine can also be recognized by the numerous peltate trichomes distributed throughout the leaflets, emarginated membrane-like domatia, and fields of patelliform trichomes that cover the inflorescence nodes. Tanaecium affine shares vegetative traits with Tanaecium tetragonolobum, a sympatric species (Tab. 1). However, T. tetragonolobum can be differentiated by the glabrous leaflets (vs. leaflets covered with peltate trichomes in T. affine), petioles longer than petiolules (vs. petioles shorter than petiolules in T. affine), and subulate prophylls of the axillary buds (vs. bromeliad-like prophylls of the axillary buds in T. affine). Notes. This species shares wide infundibular corollas with T. crucigerum, T. cyrtanthum, T. duckei, T. exitiosum, T. kuhlmannii, and T. jaroba, but can be differentiated from these taxa by the leaflets with apiculate apices and cartilaginous margins, and tubular calyces with stellate simple trichomes (Tab. 1). Out of these species, Tanaecium crucigerum and T. jaroba are the only ones that also occur in Venezuela. These species can be differentiated from T. apiculatum by the abaxial surface whitish-tomentose in T. crucigerum and abaxial surface glabrous or pubescent in T. jaroba (vs. abaxial surface glabrous in T. apiculatum). Notes. Tanaecium bilabiatum is easily differentiated from other Tanaecium species by the pulvinated petioles (typical of Adenocalymma but usually lacking in Tanaecium and other Bignonieae; Lohmann and Taylor 2014), large bilabiate calyces, covering 1:3 to 2:3 of the corolla tube, white corollas with yellow mouths, oblong and flattened fruits, and seeds with vestigial wings (rarely well-developed) (Tab. 1).   Habitat and distribution. Tanaecium crucigerum occurs in wet forests in the Lesser Antilles (Dominica, Martinique), Trinidad and Tobago, Costa Rica (Limón), and Venezuela (Anzoátegui, Apure, Cojedes, Delta Amacuro, Guárico, Portuguesa).

Tanaecium caudiculatum
Phenology. Flowering: April to July, and October; fruiting: February, April to July, and October to November.
Notes. Like Lohmann and Taylor (2014), we were also unable to locate the lectotype of T. crucigerum selected by Howard (1989: 334), the collection J. Imray 95 supposedly deposited at K. This collection is thus presumed lost. As such, we select another Imray collection from Dominica studied by Seemmann (1856) deposited at K as lectotype. We selected the material J. Imray 94 as lectotype due to high quality of this material. This species is morphologically most similar to T. jaroba, sharing many characters such as the simple tendrils, wide infundibular corollas, and wingless seeds (Tab. 1). Tanaecium crucigerum differs from T. jaroba by the whitish-tomentose leaflets on the abaxial surface (vs. glabrous or pubescent leaflets on the abaxial surface in T. jaroba). Notes. This species is generally caducous when flowering, and produces new leaves when fruiting. The tendril is simple and the leaflets have patelliform trichomes concentrated at the base abaxially. The calyces are campanulate or cupular, while the fruits are linear and inflated, bearing linear seeds, with a lateral seed body (Tab. 1). Habitat and distribution. Tanaecium decorticans is known from the Brazilian Amazon (Pará, Maranhão).
Notes. This species is morphologically most similar to T. pyramidatum, sharing characters such as the subulate prophylls, infundibular corolla with white mouth, and linear fruits (Tab.1). However, T. decorticans can be differentiated from T. pyramidatum by the stems with peeling epidermis (vs. stems without peeling epidermis in T. pyramidatum), petiolules with arrow-shaped apices (vs. lacking in T. pyramidatum), and fruits flattened with glandular patelliform and peltate trichomes along the margins (vs. fruits inflated without glandular patelliform and peltate trichomes along the margins in T. pyramidatum) (Frazão and Lohmann 2018) (Tab. 1). Fig. 1B  Notes. This species is widespread through the Neotropics, where it is found in many vegetation types. The species encompasses an enormous degree of morphological variation, representing a species complex. Detailed morphological and molecular studies are necessary to sort out the patterns of variation and identify putative cryptic species.
Phenology. Flowering: April to August and November to December; fruiting: March to August and December.
Notes. This species has the longest wide infundibular white flowers in the whole tribe Bignonieae, with corollas up to 35 cm long (Gentry 1997, Howard 1989. It is most morphologically similar to T. crucigerum, with which it shares ellipsoid fruits that bear wingless woody seeds (Tab. 1). Tanaecium jaroba differs from T. crucigerum by the glabrous or pubescent leaflets abaxially (vs. whitish-tomentose leaflets abaxially in T. crucigerum).
Habitat and distribution. Tanaecium kuhlmannii is known from only a few localities within humid formations of the Atlantic Forest of Brazil (Minas Gerais, Rio de Janeiro). Phenology. Flowering: December; fruiting: January. Notes. Gomes (1956) originally described this species as Spathicalyx kuhlmannii J.C. Gomes, but Gentry (1977) synonymized it with Spathicalyx duckei (A.Samp.) A.H.Gentry. More recently, Lohmann and Taylor (2014) synonymized Spathicalyx with Tanaecium and recognized a single species, Tanaecium duckei (A. Samp.) L.G. Lohmann, following Gentry (1977). A detailed study of these taxa showed that apart from the allopatric distribution (T. duckei is restricted to the Amazon, while T. kuhlmannii is restricted to the Atlantic Forest of Brazil), T. kuhlmannii can be distinguished by the patelliform glandular trichomes along the tertiary veins of leaflets (vs. absent in T. duckei), and the ferrugineous stipitate glandular trichomes that cover the fruit surface (vs. ferrugineous stipitate glandular trichomes lacking in T. duckei). Furthermore, T. kuhlmannii has leaflets with patelliform trichomes ≥ 0.45 mm in diameter abaxially (vs. leaflets with patelliform trichomes < 0.45 mm in diameter abaxially in T. duckei), that also show a protrusion at the patelliform insertion (vs. without protrusion at the patelliform insertion in T. duckei), and anthers ≥ 7 mm long. (vs. anthers < 7 mm long in T. duckei). Based on these morphological features and distribution data, we here recognize both taxa as separate and propose the new combination Tanaecium  Habitat and distribution. Tanaecium neobrasiliense is found in caatinga and cerrado in eastern Brazil (Bahia, Ceará, Distrito Federal, Minas Gerais). Phenology. Flowering: November to January; fruiting: January to April and June.
Notes. This species is generally confused with T. pyramidatum due to its pink corollas. However, it can be differentiated from T. pyramidatum by the leaflets 8-15 times longer than the petiole, costate calyces, and corollas with cuspidate lobes. The prophylls of the axillary buds are subulate or bromeliad-like, positioned in an acute angle in relation to the stems (vs. straight angle in T. pyramidatum) (Tab. 1).
14. Tanaecium parviflorum (Mart. ex DC.) Kaehler & L.G.Lohmann, in press ** Fig. 1E Pithecoctenium parviflorum Mart. ex DC. in A.DC. Prodr 9: 197. 1845 Notes. Tanaecium parviflorum can be distinguished from all other species of the genus by the dentate leaflet margins, calyces aristate (rarely mucronate), and fruit apices caudate. Like T. cyrtanthum and T. tetramerum, this species is also caducous when flowering. However, T. parviflorum differs from these two species by the strongly compressed corollas (Tab. 1). Notes. This species can be distinguished from other Tanaecium species by the petioles with patelliform trichomes at the apices, subulate prophylls of the axillary buds, fruits lenticellated, linear, and inflated. Despite that, T. pyramidatum is extremely variable morphologically. For example, populations from the Brazilian dry forests and cerrados have pubescent leaflets abaxially, a feature not found in any other population of this species. On the other hand, populations from Mexico are strongly covered by lenticels. Both of these features are found exclusively in these populations. Additional studies of T. pyramidatum, including phylogeographic studies based on a broad sampling of individuals collected throughout the range of this species, are necessary to identify putative cryptic species (Tab. 1).  1978 [1979] Notes. This species is well characterized morphologically and can be separated from other species of Tanaecium by the elliptic to ovate leaflets with cuspidate apices, tuft domatia in the abaxial surface of leaflets, fruits linear-oblong covered with peltate and patelliform glandular trichomes, and flat seeds with vestigial wings (Tab. 1). Tanaecium selloi (Spreng.)  Habitat and distribution. Tanaecium tetragonolobum is found in dry to evergreen lowland forest vegetation (Gentry 1997)  Notes. Tanaecium tetragonolobum can be confused with two sympatric species, T. jaroba and T. dichotomum due to the stems with interpetiolular glandular fields (sometimes lacking in T. dichotomum) and subulate or bromeliad-like prophylls of the axillary buds (Tab. 1). However, T. tetragonolobum can be separated from T. jaroba by the membrane-like domatia (lacking in T. jaroba), lack of glandular peltate trichomes abaxially (present in T. jaroba), and interpetiolular patelliform trichomes < 0.3 mm (vs. interpetiolular patelliform trichomes > 0.3 mm in T. jaroba). On the other hand, T. tetragonolobum can be separated from T. dichotomum by the trifid tendrils (vs. simple tendrils in T. dichotomum) (Tab. 1). Habitat and distribution. Tanaecium tetramerum is known from Central South America, where it occurs in Bolivia (Cochabamba, Santa Cruz), and Paraguay (Alto Paraguay, Chaco). This species occurs in xerophytic vegetation along the Chaco, in transition areas between the Chaco and Bolivian Chiquitano, Interandian, and Andean valleys. Tanaecium tetramerum generally grows on sandy soils or rocky outcrops. Phenology. Flowering: January to February, August and November; fruiting: January to February, April, and July.