Revised classification of Acanthaceae and worldwide dichotomous keys
Creators: name: Manzitto-Tripp, Erin A.
name: Darbyshire, Iain
name: Daniel, Lucinda A. McDade Thomas F.
name: Kiel, Carrie A.
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Magnoliopsida
Lamiales
Acanthaceae

description: Key to the genera of Andrographideae
Filaments swollen (pouched) distally; corolla subequally 5-lobed, not clearly bilabiate...................................................................... 2
Key to the genera of Ruellieae
Filaments not swollen or pouched; corolla bilabiate or subequally 5-lobed......................................................................................... 3
Filament curtain lacking .............................................................. 2
Filament curtain present .............................................................. 5
Cladodes (reduced abortive branches) present in the inflorescence, terminated by paired small spines; seeds not compressed, with 2 distinct grooves, surface with hygroscopic trichomes ............... Haplanthodes
Anther filament connective tissue positioned lateral to thecae, thecae facing outward in a 180° configuration from connective tissue........................................................................................3
Cladodes absent in inflorescence; seeds somewhat compressed, not distinctly grooved, surface lacking trichomes, verrucose ........ .............................................................................. Haplanthus [9]
Anther filament connective tissue positioned dorsal to thecae, thecae held parallel (i.e., side-by-side) as typical in Acanthaceae .... 4
Plants with basal rosettes of leaves.............................. Pararuellia
Ovules 2 per locule; anthers glabrous, dehiscent by longitudinal slit in central half or 2/3 of each theca........ Sphinctacanthus [10]
Plants upright, with cauline leaves................................................. ...................................................... “ Pseudosiphonium ined.” [16]
Ovules 3 or more per locule, or if 2 then anthers conspicuously penicillate at base and dehiscent by longitudinal slit in distal half extending to apex......................................................................... 4
Plants with long, tubular flowers (≥ 5 cm total length), these yellow to white, narrow, unexpanded portions of tubes ≥2× longer than expanded portions; leaves not in a basal rosette; Papuasia................ ............................................................................. Leptosiphonium
Capsule compressed perpendicular to the septum, elliptic, oblanceolate or narrowly oblong in face view; seeds subglobose, ellipsoid or block-like, not compressed, often pitted or rugose and grooved; anthers often penicillate at base ........ Andrographis [11]
Plants with short, infundibuliform flowers (<5 cm total length), these mostly purple, narrow unexpanded portions of tubes ± equal to expanded portions (or marginally different in length, not as above); leaves typically held in a basal rosette; Australia, New Caledonia, New Guinea ............................................. Brunoniella
Capsule not compressed, narrow throughout and 4-angled; seeds markedly compressed, smooth and lacking trichomes, or covered in trichomes; anthers not penicillate ............................................ 5
Pollen with coarse reticulate exine; corolla with a very long, narrow, unexpanded portion of tube; androecium of 2 stamens + 2 staminodes; ovary with 4 ovules ...................................................... 6
Calyx 4-lobed; slender procumbent herbs ................. Graphandra
Calyx 5-lobed; habit variable but not procumbent herbs............. 6
Staminodes present ........................................ Phlogacanthus [12]
Staminodes absent ....................................................................... 7
Corolla tube shorter than limb; upper lip ± curved.... Diotacanthus
Corolla tube longer than limb; upper lip not curved...................... .............................................................................. Gymnostachyum
Key to the genera of Whitfieldieae
Seeds covered in hygroscopic trichomes that obscure the seed surface; androecium of 2 stamens and (usually) 2 staminodes; corolla salverform (or sinus between the anterior pair of lobes broader than the other sinuses), tube narrowly cylindrical throughout............... .................................................................................... Lankesteria
Seeds lacking trichomes, surface with concentric rings at least towards rim; androecium of 4 stamens (very rarely reduced to 2 stamens plus 2 staminodes in occasional flowers); corolla form various but not salverform with tube narrowly cylindrical throughout........ 2
Flowers in well-developed racemes or spikes, these sometimes branched to form panicles; tropical Africa and Madagascar ....... 3
Flowers in axillary or subterminal fascicles, glomerules or short umbels; Madagascar [13]............................................................. 4
Each inflorescence unit 1-flowered; calyx ≥ 9 mm long, usually extending beyond or subequal in length to bracteoles, often showy and can be colored similar to corolla........................... Whitfieldia
Each inflorescence unit either 1-flowered or 2–3-flowered; calyx up to 8 mm long, hidden within paired bracteoles, not colored similar to corolla..................................................... Chlamydacanthus
Peduncle of each inflorescence unit conspicuous, filiform, 7–14 mm long, considerably longer than bracteoles and calyces .. .. Zygoruellia
Inflorescence units either sessile or peduncles shorter than or equal in length to bracteoles and calyces, not filiform.......................... 5
Corolla bright orange-red or scarlet, tube markedly curved; stamens exserted well beyond corolla lobes..................... Camarotea
Corolla variously colored but not bright orange-red or scarlet, tube straight or curved; stamens not or only slightly exserted beyond corolla lobes................................................................................. 6
Corolla tube subequal in length to limb, limb strongly bilabiate, lobes of upper lip partially fused, all lobes with long wispy white trichomes internally ............................................. Leandriella [14]
Corolla tube longer than limb, often markedly so, limb not strongly bilabiate, lobes of upper lip more deeply divided, or limb subequally 5-lobed, all lobes lacking long white trichomes internally .......................................................... Forcipella / Vindasia [15]
5 Pollen, corolla, androecium, and ovule number various, but not in the above combination................................................................. 7
6 Dichasia of 2 flowers typically arranged in terminal spikes, each flower subtended by a single leaf-like bract; pollen colporate; tropical Asia................................................................................ Eranthemum
6 Dichasia typically of 2 flowers, axillary and not arranged into terminal spikes, each flower subtended by pair of leaf-like bracts; pollen porate; west-central Africa ................................. Kosmosiphon
7 All anther thecae lacking basal awns or appendages ................... 8
7 One or more anther thecae with basal awns or appendages....... 27
8 Corolla with a rugula and with rows of trichomes on the inner surface of posterior corolla; transverse fusion of filaments creating a ridge or “strobilanthoid” type of filament curtain ....................... 9
8 Corolla lacking a rugula or rows of trichomes; filament curtain not “strobilanthoid” ......................................................................... 10
9 Ovaries with ≤4 ovules ............................................ Strobilanthes
9 Ovaries with>4 ovules ....................................... Strobilanthes s.l. [incl. Hemigraphis / Clarkeasia / Stenosiphonium] [17]
10 Androecium of 2 stamens + 2 staminodes................................. 11
10 Androecium of 4 stamens.......................................................... 14
11 Ovaries with 2 ovules; pollen with sexine lips, 12-pseudocolpate; plants usually strongly odoriferous with a creosote-like smell ...... .................................................................................... Duosperma
11 Ovaries with>2 ovules; pollen lacking sexine lips and not 12- pseudocolpate; plants not typically strongly odoriferous .......... 12
12 Corolla very large, gullet-shaped, pale green to greenish-yellow (sometimes with maroon tinges), cream-colored, or entirely dark maroon; primarily nocturnal, and adapted to bat pollinators; calyx 3-lobed; pollen lacking pseudocolpi.......................... Louteridium
12 Corolla various but not in the above character combination, and rarely yellow; calyx not 3-lobed; pollen with 4 pseudocolpi......13
13 Plants usually large herbs to large shrubs; corolla strongly bilabiate, hooded; leaf bases decurrent onto the petiole and forming a wing; plants typically of forests and woodlands or their margins.... ...................................................................................... Brillantaisia
13 Plants typically small herbs; corolla usually more weakly bilabiate, typically not hooded; leaf bases not typically decurrent onto the petiole thus not forming a wing; plants typically of riparian corridors ...................................................................... Hygrophila
14 Plants with large, inflated calyces with calyx lobes fused nearly to the apex (thus appearing tubular); all plant surfaces covered with large, prominent glands ............................................ Satanocrater
14 Plants lacking large, inflated, nearly completely fused calyces; plant surfaces with or without glands but not to the extent and size as above ..................................................................................... 15
15 Corolla with all 5 lobes comprising the lower lip (thus 1-lipped) .... ............................................................................ Eremomastax [18]
15 Corolla not 1-lipped................................................................... 16
16 Corolla with conspicuous “herring-bone” pattern characterizing lower throat and/or lip surfaces; transverse folds of corolla forming an additional fold (in addition to transverse fusion of filaments), or “corolla fold” type of filament curtain; corolla typically strongly bilabiate but weakly bilabiate in a few species.......................... 17
16 Corolla lacking “herring-bone” patterning; filament curtain not of the “corolla fold” type; corolla typically rotate to zygomorphic, only distinctly bilabiate in a few species ................................... 18
17 Large herbs typically> 1 m in height; leaves drying blackish in color; pollen grains 2-aperturate........................ Calacanthus [19]
17 Small herbs typically <1 m in height; leaves not drying blackish in color; pollen grains 4-aperturate.................................. Hygrophila
18 Calyx 3-lobed ............................................................ Louteridium
18 Calyx not 3-lobed ...................................................................... 19
19 Corolla with flattened, apically rounded, uni- or bicellular trichomes lining inner corolla surfaces; pollen spherical, echinate, lacking ring of echinae surrounding the apertures....... Acanthopale
19 Corolla lacking trichomes as described above; pollen various but not spherical, echinate, and lacking the ring of echinae............ 20
20 Ovary with 2 ovules; pollen with sexine lips and 12-pseudocolpate; plants usually strongly odoriferous with a creosote-like smell .................................................................................... Duosperma
20 Ovary with>2 ovules (rarely reduced to 2); pollen lacking sexine lips and not 12-pseudocolpate; plants not typically strongly odoriferous.........................................................................................21
21 Calyx conspicuously zygomorphic............................................ 22
21 Calyx typically actinomorphic or at most weakly zygomorphic .............................................................................................................23
22 Calyx with 3 anterior lobes fused to varying degrees, 2 posterior lobes mostly free; dorsalmost lobe lacking conspicuous marginal veins; pollen spherical, echinate, and with conspicuous ring of echinae surrounding the apertures .................. Dischistocalyx [20]
22 Calyx in a 2 + 2 + 1 configuration with dorsalmost lobe the largest, the 2 ventral lobes intermediate in size, the 2 lateral lobes the smallest, and all lobes free to the receptacle; dorsalmost lobe with conspicuous marginal veins; pollen spherical, coarsely reticulate, ring of echinae absent........................................... Dinteracanthus
23 Shrubs or trees to 25 m tall and usually> 4 m in height at maturity; plants often used as fence posts; restricted to southern Central America and northern South America...................... Trichanthera
23 Herbs, shrubs, or treelets, but clearly not true trees; plants not used as fenceposts to our knowledge; widespread............................. 24
24 Plants covered in dense tomentum of golden-yellow pubescence; pollen bicolporate with numerous bands of pseudocolpi oriented perpendicular to opposing face........................... Trichosanchezia
24 Plants not as above; pollen not as above.................................... 25
25 Pollen spherical, exine coarsely reticulate, lacking pseudocolpi and lacking sexine lips ............................................................. Ruellia
25 Pollen 3-porate, 12-pseudocolpate, pores flanked by sexine lips .... 26
26 Capsule with fracturing placentae ............................... Phaulopsis
26 Capsule remaining intact post-dehiscence, lacking fracturing placentae................................................................. Heteradelphia
27 Plants creeping or trailing herbs characterized most frequently by near linear leaves, giving overall gestalt a “grass-like” appearance (rarely elliptical to obovate); restricted to Namib and Kalahari Deserts......................................................................... Ruelliopsis
27 Plant habit various but not creeping with linear leaves and “grass-like” in appearance; widespread ................................................ 28
28 Capsule with fracturing placentae ............................................. 29
28 Capsule with placentae that remain attached to capsular wall at time of dehiscence ..................................................................... 30
29 Flowers lacking pair of conspicuously leaf-like bracts; pollen grains with sexine lips ................................................. Phaulopsis
29 Conspicuous pair of relatively large, leaf-like bracts subtending each flower; pollen grains with 4 areas of raised tectum, triangular in polar view................................................................. Petalidium
30 Anther thecae each with 2 appendages................... Diceratotheca
30 Anther thecae otherwise ............................................................ 31
31 Pollen polypseudocolpate with 40+ pseudocolpi.............................. ................................................................“ Sinoacanthus ined.” [21]
31 Pollen otherwise ........................................................................ 32
32 Calyx lobes fused for at least 1/3 of their length and usually over half of their length, with hyaline regions bordering each lobe............................................................................................ 33
32 Calyx lobes unfused or variously fused but rarely over 1/3 of their length, lacking hyaline regions bordering each lobe ................. 34
33 Ovary with 4 ovules, capsule with (up to) 4 seeds ........................ ............................................................................ Dyschoriste [22]
33 Ovary with 8 ovules, capsule with more than 4 seeds................... .............................................................................. Echinacanthus
34 Leaves conspicuously dentate or crenate................................... 35
34 Leaves entire or weakly dentate to crenate, but not conspicuously so...................................................................................... 36
35 Outermost theca of each of longer pair of stamens with a conspicuous appendage, other thecae with much shorter appendages or rounded................................................................ Mimulopsis [23]
35 Either both thecae or one of each pair of thecae of all anthers with an appendage ............................................................. Mellera [24]
36 Plants with long tubular, bird-pollination adapted flowers, often bright red, pink, orange, or yellow in color; pollen bicolporate with numerous bands of pseudocolpi oriented perpendicular to opposing face ...................................................................................... 37
36 Plants with various flowers and pollen, but not as above .......... 38
37 Androecium of 2 stamens + 2 staminodes.................... Sanchezia
37 Androecium of 4 stamens...................................... Suessenguthia
38 Capsules usually 2-seeded ......................................................... 39
38 Capsules with>2 seeds.............................................................. 40
39 Corolla bilabiate, 10–12.5 mm long, tube cylindrical, without a clearly expanded throat; lower lip with long bristly trichomes internally; pollen with 12 pseudocolpi; SW Angola .............. Mcdadea
39 Corolla subactinomorphic, not strongly bilabiate, 22–45 mm long, tube clearly differentiated into a narrow basal tube and an expanded throat; pollen with 18+ pseudocolpi; Angola to D.R. Congo and to Zimbabwe .......................... Strobilanthopsis
40 Inflorescences of very long, terminal spikes, these commonly 30 cm in length; Malaysia ........................................ Stenothyrsus
40 Inflorescences variable, primarily of racemes, less commonly of spikes or solitary flowers, but if a spike, these not so elongate, consistently <15 cm long ................................................................ 41
41 Evergreen shrubs or trees, precocious flowering absent; ultimate branches not as below; pollen bicolporate with numerous bands of pseudocolpi oriented perpendicular to opposing face; Neotropics............................................................................... Bravaisia
41 Deciduous tree to 5 m tall, flowering before the leaves appear (precocious flowering); ultimate branches numerous and curved-ascending; pollen not as above; karst hills of Laos ....................... ........................................................................... Xylacanthus [25]
description: Published as part of Manzitto-Tripp, Erin A., Darbyshire, Iain, Daniel, Lucinda A. McDade Thomas F. & Kiel, Carrie A., 2022, Revised classification of Acanthaceae and worldwide dichotomous keys, pp. 103-153 in TAXON 71 (1) on pages 123-125, DOI: 10.1002/tax.12600, http://zenodo.org/record/14047424