Commelina Plum.

Genus Commelina Plum. View in CoL ex L.

The gem-fruited Commelina View in CoL

Athyrocarpus Schltdl. ( Schlechtendal 1855: 454) View in CoL ; Hasskarl (1866: 212); Bentham in Bentham & Hooker (1883: 847). – Type species: Commelina pallida Humb. & Bonpl. ex Willd. View in CoL ; designated here.

Commelinopsis Pichon ( Pichon 1946: 227) View in CoL , pro parte. – Type species: Commelina persicariifolia Redouté. View in CoL

Phaeosphaerion Hassk. ( Hasskarl 1866: 212) View in CoL . – Type species: Commelina leiocarpa Benth. View in CoL

Characterisation and circumscription

This informal and non-monophyletic group is treated as such due to the historical taxonomic and nomenclatural confusion involving its species. The only character uniting these eight species is their showy and gem-like fruits, used in the past to delimit genera previously segregated from Commelina (i.e., Athyrocarpus , Commelinopsis , and Phaeosphaerion ) and tribe Pollieae C.B.Clarke ( Clarke 1881) . Despite the morphological dissimilarity between these species, they continue to be confused and lumped together by field and generalist botanists, as well as by ecologists, parataxonomists, and amateurs. Thus, treating them in the same study not only makes sense from a nomenclatural and taxonomic perspective but also centralises the most up-to-date information available for this group.

The fruits in the gem-fruited Commelina can range from dehiscent to partially dehiscent to indehiscent, crustaceous or not, and be shiny pearly-white to silvery, opaque off-white, opaque reddish-brown to dark maroon, or glaucous atro-vinaceous to bluish-black to black. The seeds can be monomorphic or dimorphic, free or variously fused to the fruit wall or septa, and their ornamentation can range from smooth to variously ornate. However, as hypothesised by Faden & Hunt (1987), the gem-like fruits seem to have evolved independently several times within Commelina since all gem-fruited species are morphologically and phylogenetically related to other species that lack such fruits (Pellegrini et al. in prep.). Furthermore, gem-fruited species of Commelina are recovered in at least three distantly related lineages in the genus (Pellegrini et al. in prep.).

Accepted species

We currently accept eight species of gem-fruited Commelina , plus six morphologically similar or closely related species, totalling 14 species. These species are organised into three morphologically cohesive and molecularly supported species groups (Pellegrini et al. in prep.), namely: 1) Commelina benghalensis group [i.e., C. obliqua Vahl , C. pseudomonosperma (Kuntze) L.M.Campb. , and C. rufipes Seub. ]; 2) C. robusta group [i.e., C. bambusifolia Matuda , C. huntii M.Pell. , C. robusta Kunth , C. scabrata Seub. , C. sugariae M.Pell. sp. nov., and C. vestita Seub. ]; and 3) C. tuberosa group [i.e., C. almandina M.Pell. & Cornejo sp. nov., C. efoveolata (C.B.Clarke) L.M.Campb. , C. leiocarpa Benth. , C. pallida Humb. & Bonpl. ex Willd. , and C. texcocana Matuda ].

Distribution

This non-monophyletic group is currently restricted to the Neotropics, although at least one undescribed species is from the Palaeotropics (i.e., Madagascar; Faden & Hunt 1987). In the Neotropics, the group occurs from Mexico, reaching the Antilles and extending all the way down to northern Argentina, Bolivia, and Brazil. Brazil and Mexico are the most species-rich countries for members of this group, with 8 and 7 species, respectively.

Ecology

Most species in this group grow in the understory of dry or rainforests, with a few of them also occurring or being restricted to open environments.

Fruit dispersal

Fruit and seed dispersal in the gem-fruited species has never been studied, and this reflects the complete absence of dispersal studies for Commelinaceae ( Pellegrini & Faden 2017) . However, it is hypothesised that the species with indehiscent fruits are zoochoric and potentially dispersed by birds ( Faden & Hunt 1987; Pellegrini & Faden 2017). However, the species with dehiscent fruits (e.g., the newly described C. almandina M.Pell. & Cornejo sp. nov.) seem less likely to be dispersed by birds, despite being dark-coloured, clearly exposed by the plant’s vining habit, and being exerted from the spathe during maturity (Pellegrini, pers. obs.). Species with white fruits (dehiscent or not) are small-sized, prostrate to ascending, sometimes scrambling, small understory herbs, making their fruits somewhat difficult for most open environment birds to access. This makes it more likely for the dispersers to be some type of understory bird(s) native to the Neotropical rainforests (Pellegrini, pers. obs.).

Nomenclatural remarks

Athyrocarpus was first described by Schlechtendal (1855: 454), who provides a rather detailed diagnosis for his new genus, characterising it by its sub-solitary inflorescences, with the superior cincinnus aborted or completely lacking and the lateral one 2–4-flowered, flowers similar to Commelina in possessing 5 stamens (2 of which are ended by antherodes, i.e., staminodial), indehiscent green fruits becoming lead-blue at maturity, and dimorphic seeds. Schlechtendal (1855) goes into further detail, comparing his new genus to Aclisia E.Mey. ex C.Presl , Pollia Thunb. , and Lamprocarpus Blume (all currently treated as Pollia s. lat.) due to their similar fruit morphology. Therefore, Schlechtendal’s (1855: 454) is considered the original work where this name was first validly published. Thus, Hasskarl (1866: 212) and Bentham & Hooker (1883: 847) actually represent citations of Schlechtendal’s genus and not attempts to validate the name as considered by many databases. Finally, Schlechtendal (1855: 454) included two species in his new genus, C. pallida and C. rubens Redouté ; however, without formally transferring any of them to Athyrocarpus . Based on Schlechtendal’s diagnosis, plus the fact that C. rubens is considered to be distantly related to C. pallida (this study; see Remarks under C. rubens and Discussion), we designate C. pallida as the type species for Athyrocarpus . Interestingly, neither C. pallida nor C. rubens present the gem-like blue fruits deemed to be diagnostic for the genus.

When describing Commelinopsis, Pichon (1946) unambiguously designated Commelina persicariifolia Redouté as the type species for his new genus by including it as its sole species. Nonetheless, the species does not possess the crustaceous, indehiscent and pearly-white to silvery capsules and seeds fused to the fruit wall and septae, which were listed by the author as diagnostic for the genus ( Pichon 1946: 227). This is easily explained by Pichon’s incorrect application of C. persicariifolia , which for Pichon was conspecific with C. rufipes . Therefore, despite the widespread use of this generic name for the C. rufipes complex, it is actually typified by an unrelated species belonging to the C. tuberosa group.

Phaeosphaerion was described by Hasskarl (1866: 212) based on his identification key for the genera of Commelinaceae . Despite being brief, the step leading to Phaeosphaerion characterises the genus as having flowers obscured by the spathe, simple stigma, and indehiscent, shiny and lead-black capsules. Despite not formally transferring it to his new genus, Hasskarl (1866: 212) does cite C. leiocarpa Benth. Hence , this species must be treated as the type species for the genus Phaeosphaerion .

Key to the gem-fruited Commelina Plum. View in CoL ex L. and allies

1. Leaf-sheaths with hyaline to white hairs along the margin; inflorescences predominantly axillary and leaf-opposed, long pedunculate (peduncle the same length or longer than ½ length of the spathe), spathe base free, internally inconspicuously mucilaginous; sepals opaque, green, lower sepals sessile, free, medial petal shortly-clawed, style base tapering into the ovary; fruits thick-walled ................. ............................................................................................................ 2 ( Commelina tuberosa View in CoL group)

– Leaf-sheaths with light brown to brown or rusty to rusty-brown or red to dark red to atro-vinaceous hairs along the margin; inflorescences terminal or apparently so, short-pedunculate to sessile (peduncle shorter than ½ length of the spathe), spathe base connate at least at base, internally conspicuously mucilaginous; sepals hyaline, colourless to white, lower sepals shortly-clawed, connate up to half their length, medial petal sessile, style base not tapering into the ovary; fruits thin-walled ............ 6

2. Peduncle pendulous, spathe slightly falcate, base cordate; pedicels puberulous with minute hook-hairs only, style twice as long as the stamens, persistent in fruit, stigma tan-coloured; fruits indehiscent, glaucous, not constricted between the seeds when mature, atro-vinaceous to bluish-black to black when mature, apex round to apiculate; seeds monomorphic, triangular to widely triangular to triangular-ellipsoid ............................................................................................................................................. 3

– Peduncle straight, spathe straight, base subcordate to round; pedicels pilose with acicular hairs or with a mixture of acicular and hook-hairs, style slightly longer than the stamens, deciduous in fruit, stigma white; fruits dehiscent, 3-valved, opaque, constricted between the seeds when mature, tan-coloured or reddish-brown to dark maroon when mature, apex rostrate; seeds dimorphic, ellipsoid ........................................................................................................................................................... 4

3. Stems branched from the base or almost so, sparsely to densely hispid with acicular hairs; leaf-blades adaxially sparsely to densely hispid with acicular hairs, abaxially sparsely to densely hispid with acicular hairs, hairs generally congested along the midvein, margin ciliate with a mixture of prickle- and acicular hairs; spathe externally sparsely to densely hispid with acicular hairs; dorsal sepal pilose along the midvein, lower sepals widely elliptic, petals white to pale lilac-blue to light blue, medial petal apex obtuse to round, antherodes yellow, X-shaped, upper lobes conspicuous, lower lobes spathulate to obovate, medial anther linear-hastate; seeds slightly cleft towards the embryotega, ventrally flattened, dark grey to black, testa rugose, farinae white .................................................... ............................................................................. Commelina efoveolata (C.B.Clarke) L.M.Campb.

– Stems branched in the upper half or upper third, scabrid with a mixture of prickle- and hook-hairs; leaf-blades adaxially glabrous to scabrid with a mixture of prickle- and hook-hairs, sometimes also sparsely setose along the midvein, abaxially scabrid with a mixture of prickle- and hook-hairs and setose along the midvein, margin papillose; spathe externally glabrous to scabrid with a mixture of prickle- and hook-hairs; sepals glabrous, lower sepals ovate to widely ovate, petals sky blue, medial petal apex cuspidate, antherodes white, V-shaped, upper lobes absent, lower lobes filiform, medial anther narrowly sagittate; seeds not slightly cleft towards the embryotega, ventrally pyramidal, light grey to greyish-brown, testa foveolate, farinae cream-coloured ........................................................ .............................................................................................................. Commelina leiocarpa Benth. View in CoL

4. Vining herbs; synflorescence generally composed of a main florescence plus 1–2 co-florescences; all sepals evenly pilose, paired petals limb base subcordate, antherodes with upper lobes conspicuous, lower lobes spathulate to obovate, anthers white to cream-coloured, lateral anthers held near the antherodes and medial anther, stigma truncate; fruits with valves splitting only up to mid-length, reddish-brown to dark maroon when mature ...................................................................................... ........................................................................... Commelina almandina M.Pell. & Cornejo sp. nov.

– Scrambling herbs; synflorescence composed of a solitary main florescence; all sepals glabrous to dorsal sepal pilose along the midvein, paired petals limb base truncate, antherodes with upper lobes absent or reduced, lower lobes filiform, anthers yellow, lateral anthers held near the medial, stigma capitate; fruits with valves splitting to base, tan-coloured when mature .......................................... 5

5. Stems, leaf-sheaths, leaf-blades and spathe sparsely strigose to strigose, hairs drying light brown to golden; leaf-blade base obtuse to round; spathe with apex acute, straight; pedicel pilose with a mixture of acicular and hook-hairs, dorsal sepal ovate, glabrous to slightly puberulous along the midvein, lower sepals ovate, slightly overlapping, petals pale lilac to lilac, antherodes V-shaped, medial anther linear sagittate to narrowly sagittate, strongly curved, ovary verrucose; capsules widely ellipsoid to oblongoid, sessile ..................................................... Commelina pallida Humb. & Bonpl. ex Willd. View in CoL

– Stems, leaf-sheaths and leaf-blades glabrous, spathe glabrous to velutine, when present hairs hyaline; leaf-blade base cuneate; spathe with apex acuminate, slightly falcate; pedicel pilose with acicular hairs only, dorsal sepal elliptic to narrowly triangular, setose along the midvein, lower sepals triangular to widely trullate, divergent, petals white to light blue, antherodes scarcely X-shaped, medial anther oblong-sagittate, curved, ovary smooth; capsules fusiform to ellipsoid, short-stipitate .............................................................................................. Commelina texcocana Matuda View in CoL

6. Leaf-blade margin slightly revolute; spathe only basally connate, much lighter than the leaves (in vivo), the fused base splitting open in fruit; pedicels sparsely puberulous to puberulous with minute hook-hairs, sepals early deciduous in fruit, medial petal opaque, antherodes narrowly hastate to subtrapezoid, stigma truncate; fruits short-stipitate, indehiscent, not constricted between the seeds, crustaceous, pearly-white to silvery when mature; seeds ventrally pyramidal, all adnate to the fruit wall and septa and forming a dispersal unit, testa smooth, non-farinose; seeds embryotega lateral, ventral seeds hilum linear ........................................................... 7 ( Commelina benghalensis View in CoL group)

– Leaf-blade margin flat; spathe base connate on the basal half to almost completely connate, the same colour as the leaves (in vivo), base remaining fused in fruit; pedicels glabrous, sepals persistent and accrescent in fruit, medial petal hyaline, antherodes X-shaped, stigma trilobate; fruits sessile, dehiscent, constricted between the seeds, not crustaceous, tan-coloured or off-white when mature; seeds ventrally flattened, not adnate to the fruit wall and septa and each dispersed individually, testa ornate, at least ventral locule seeds farinose; seeds embryotega semidorsal to semilateral, ventral seeds hilum curved or C-shaped ..........................................................9 ( Commelina robusta View in CoL group)

7. Stems prostrate; leaf-sheaths hirsute throughout, margin hirsute, hairs rusty to rusty-brown, blades lanceolate to elliptic-lanceolate, opaque, membranous, hispid on both sides, hairs hyaline, sparsely hirsute along the midvein and near base, hairs rusty to rusty-brown, base symmetric, cuneate to obtuse, apex acute; spathe ovate to widely ovate, hispid with hyaline acicular hairs, sometimes with some rusty hirsute hairs; paired petals limb rhombic to rotund, medial petal elliptic to narrowly oblanceolate, flat; antherodes apiculate between the upper lobes, upper lobes absent; medial connective oblong; seed testa smooth ....................................................................................... Commelina rufipes Seub. View in CoL

– Stems ascending to scrambling; leaf-sheaths glabrous, margin glabrous to setose, hairs light brown to rusty, blades lanceolate to ovate, sometimes elliptic, lustrous, thinly chartaceous to chartaceous, glabrous on both sides or adaxially glabrous to scabrid with prickle-hairs and abaxially, base asymmetric to strongly asymmetric, one side cuneate the other round, apex acuminate to long-acuminate; spathe very widely ovate to depressed ovate, glabrous, rarely with occasional hook-hairs; paired petals limb widely rhombic-reniform to reniform, medial petal lanceolate or spathulate to oblanceolate, not flat; antherodes not apiculate between the upper lobes, upper lobes present; medial connective saddle-shaped; seed testa inconspicuously foveolate ..................................................... 8

8. Synflorescences composed of a solitary main florescence, terminal; spathe margin flat, apex acuminate; petals white, medial petal lanceolate, flat, margin revolute at mid-length, forming a medial constriction, apex acute; antherodes narrowly hastate, distinctly lobed, minute pollen sacs between the upper and lower lobes present, obliquely connate to the lower lobes, lateral anthers elliptic to ovate, held near the antherodes, medial anther held near the medial petal, style sigmoid, apex strongly recurved; fruits 6–9 per spathe, widely ellipsoid to widely oblongoid, stipe 0.3–0.9 mm long .................................. ..................................................................................................................... Commelina obliqua Vahl View in CoL

– Synflorescences composed of main florescence plus 1–6 co-florescences, axillary and terminal; spathe margin repandous, apex acute; petals pale lavender to light pink, medial petal spathulate to oblanceolate, cucullate, margin flat, lacking a medial constriction, apex round; antherodes subtrapezoid, indistinctly lobed, minute pollen sacs between the upper and lower lobes absent, lateral anthers subcordate to cordate, held near the medial anther and stigma, style straight to very gently sigmoid, apex not recurved; fruits 2–4 per spathe, widely obovoid, stipe 0.8–1.2 mm long ............. .................................................................... Commelina pseudomonosperma (Kuntze) L.M.Campb. View in CoL

9. Leaf-sheaths hirsute, blades narrowly oblong to narrowly elliptic, obliquely asymmetric, adaxially glabrous to hispid, abaxially hirsute along the midvein, apex acuminate to long-acuminate; spathe connate to the apex or almost so, marcescent in fruit, upper cincinnus vestigial, flowerless, peduncle included in the spathe, lower cincinnus glabrous to sparsely puberulous with minute hook-hairs only towards the apex; lower sepals connate up to mid-length, paired petals limb base cuneate, medial petal lanceolate to ovate, medial anther lacking a vinaceous to dark purple spot on the connective; capsules off-white and opaque when mature, all locules 1-seeded; ventral seeds hilum C-shaped ... ......................................................................................................................................................... 10

– Leaf-sheaths scabrid, blades lanceolate to ovate, straight, scabrid or velutine on both sides, apex obtuse to acute; spathe connate up to mid-length, remaining green in fruit, upper cincinnus developed, flowered, peduncle exserted from the spathe, lower cincinnus pilose with hook-hairs or with a mixture of acicular and hook-hairs; lower sepals connate up to the upper third, paired petals limb base cordate, medial petal spathulate to obovate, medial anther with an orange-brown or vinaceous to atro-vinaceous spot on the connective; capsules tan-coloured and shiny when mature, dorsal locule 1-seeded, ventral ones 2-seeded; ventral seeds hilum curved ......................................................................................11

10. Leaf-blades sessile, adaxially hispid with a mixture of acicular and glandular hairs, abaxially hispid, hirsute along the midvein, hairs acicular, base amplexicaulous to subamplexicaulous; paired petals light blue to pale lilac; fruits subglobose, smooth, apex round to 3-lobed, not parasitised, equally 3-valved, valves splitting to base; seeds monomorphic, all free from the fruit wall, testa smooth to inconspicuously foveolate ............................................................ Commelina bambusifolia Matuda View in CoL

– Leaf-blades pseudopetiolate, adaxially glabrous to hispid, hairs acicular, abaxially hispid, hirsute along the midvein, hairs acicular, base cuneate; paired petals sky blue; fruits prismatic, sparsely verrucose, apex aristate, consistently parasitised by weevil larvae, unequally 2-valved, valves splitting up to mid-length; seeds dimorphic, dorsal locule seed adnate to the fruit wall, testa shallowly foveolate, ventral locule seeds free from the fruit wall, testa sparsely echinate ................................................. ................................................................................................................. Commelina scabrata Seub. View in CoL

11. Leaf-sheath margin densely hispid to setose with rusty to rusty-brown hairs; paired petals white, medial petal concave, 2-auriculate, concolourous with the paired petals, lateral anthers with margin tinted purple to atro-purpureous; ovary and capsules with black papillae, capsules 1–2 per spathe; seeds apricot-farinose, dorsal seed testa shallowly foveolate ................... Commelina huntii M.Pell. View in CoL

– Leaf-sheath margin with light brown to brown or red to dark red to atro-vinaceous hairs; paired petals light blue to blue to sky blue or pale lilac to lilac, medial petal involute, entire, discolourous with the paired petals, lateral anthers evenly coloured; ovary and capsules smooth, capsules 3–9 per spathe; seeds white-farinose, when present dorsal seed testa rugose-foveolate ......................................... 12

12. Herbs delicate; stems ascending to erect throughout, unbranched or branched only at base, not glaucous; leaf-sheath margin with light brown to brown hairs, blades abaxially light green speckled with vinaceous to dark purple to completely vinaceous to dark purple; spathe cordate to widely cordate, rarely depressed ovate; lower sepals limb obovate to widely obovate, depressed oblique-ovate, paired petals claw blue to sky blue, medial petal white, apex slightly involute, filaments apex tan-coloured, antherodes apiculate between the upper lobes, anthers pale orange-yellow to pale apricot, lateral anthers held near the stigma, medial anther held near the antherodes; capsules 6–9 per spathe .................................................................................................... Commelina vestita Seub. View in CoL

– Herbs medium-sized to robust; stems base prostrate, apex ascending to scrambling, branched throughout or branched on the upper third, glaucous; leaf-sheath margin with rusty to rusty-brown to red to dark red to atro-vinaceous hairs, blades abaxially evenly light green to greyish-green; spathe widely ovate to very widely ovate or depressed ovate to widely depressed ovate; lower sepals limb widely oblique-ovate, paired petals claw mauve to lilac, rarely white, medial petal light blue to pale lilac, apex completely involute, filament apex burgundy to atro-vinaceous, antherodes not apiculate between the upper lobes, anthers orange-yellow to orange to apricot, lateral anthers held near the medial anther; capsules 3–5 per spathe .......................................................................................... 13

13. Stems glabrous to scabrid with prickle-hairs; leaf-blades abaxially scabrid with prickle-hairs, abaxially scabrid with prickle-hairs to pilose with acicular hairs, hairs hyaline; spathe depressed ovate to widely depressed ovate, rarely very widely ovate, externally scabrid with prickle-hairs, apex obtuse to round, bracteoles very widely ovate to depressed ovate; dorsal sepal triangular to widely triangular, paired petals limb very widely ovate-reniform to depressed ovate-reniform, medial petal spathulate to obovate, abaxially puberulous at base with glandular microhairs, antherodes with upper lobes equal to subequal to lower ones, ovary 3-carpellate, ellipsoid; capsules obovoid, not dorsiventrally compressed, 3-locular, unequally 2-valved, 5-seeded ............................. Commelina robusta Kunth View in CoL

– Stems puberulous with glandular microhairs; leaf-blades abaxially hispidulous to densely hispidulous with acicular hairs or a mixture of prickle- and acicular hairs, hispid along the midvein with acicular hairs, hairs hyaline, sometimes rusty at blade base; spathe widely ovate to very widely ovate, externally sparsely pilose to pilose with minute hook-hairs or with a mixture of hook- and glandular microhairs, sometimes with sparse to occasional hispid setose hairs, apex obtuse to acute, bracteoles ovate; dorsal sepal elliptic to ovate, paired petals limb ovate-reniform to widely ovate-reniform, medial petal oblanceolate, glabrous on both sides, antherodes with upper lobes conspicuously shorter than lower ones, ovary 2-carpellate, oblong; capsules oblong to rectangular, dorsiventrally compressed, 2-locular, equally 2-valved, 4-seeded ..................................... Commelina sugariae M.Pell. sp. nov.