Tillandsia aëranthos (Loisel.) L.B. Smith (1943: 200)

Rossado, Andrés J., Donadío, Sabina & Bonifacino, José M., 2024, A taxonomic revision of Tillandsia (Tillandsioideae, Bromeliaceae) from Uruguay, Phytotaxa 667 (1), pp. 1-90 : 1-90

1. Tillandsia aëranthos (Loisel.) L.B. Smith (1943: 200) . Figs. 5A , 6 , and 7.

≡ Anoplophytum aëranthos (Loisel.) Beer ([1856] 1857: 40) ≡ Anoplophytum dianthoideum (G. Rossi) Beer ([1856] 1857: 41), nom. illeg. superfl. ≡ Tillandsia dianthoidea G. Rossi (1826: 79) , nom. illeg. superfl. ≡ Pourretia aëranthos Loiseleur-Deslongchamps (1821 : t. 304). Type (lectotype designated by Smith & Downs 1977: 837):—[Icon] t. 304 in Loiseleur-Deslongchamps (1821)!. Epitype (designated here):— URUGUAY: [Montevideo], “Quinta Siberia (Miguelete)”, 25 November 1904, Berro 6087 (MVFA!).

= Tillandsia microxiphion Baker (1893 : t. 7320). Type (lectotype designated here):— URUGUAY. Without information: “Cuaió” [Cuaró], 1890, André k-323 (K000321912 [online image!]; isolectotype: F0045287F [online image!]).

– Tillandsia bicolor auct . non Brongniart (1829 [1834]: 185).

Plants caulescent, not branched or few to much branched from the base and then forming subdense clumps up to 25 cm in diameter but generally smaller, sometimes stems short and then plants appearing acaulescent. Roots 0.5–1 mm diameter, only present at the base of the stem. Stems up to 45 cm long but generally shorter than 25 cm. Leaves spirally arranged, distributed along the stem, dark green to grayish-green, sometimes violaceous when sun-exposed; sheaths gradually merging into blades, very widely triangular-ovate, densely lepidote except for the glabrous basal portion; blades (35–)45–135(–155) × 5–14 mm, suberect to spreading, sometimes somewhat reflexed, very narrowly to narrowly triangular, channelled from the base to almost the apex, chartaceous, densely appressed-lepidote throughout, trichomes symmetric. Inflorescences simple; peduncles wholly covered by bracts or seldom apically visible, (2.5–) 5–15 cm long, 2.7–3.7 mm in diameter, glabrous; peduncle bracts 5 to 12(16) in number (the basal ones leaf-like), erect, evenly distributed along the peduncle, densely imbricate (sheaths covering ¼ to ca. ¾ of the sheath of the following bract); upper peduncle bract with developed blade; sheath 14–34 × 8–14 mm, (narrowly) elliptic to elliptic-ovate, fuchsia to grayish-fuchsia, lepidote (except for the always glabrous base and margins) with denser trichomes towards the apex or trichomes only present apically; blade 5.5–17(–33) mm long. Spike spirally and densely (5)6 to 16-flowered, 30–70 mm long, ellipsoid; rachis hidden by the floral bracts or sometimes partially exposed, red to greenish, glabrous. Floral bracts densely to very densely distributed (3.5–11 times longer than the internodes), imbricate or not, ecarinate; sheath clasping the base of the flower, elliptic, sometimes elliptic-ovate, fuchsia; basal floral bracts always with blade; sheath 16–30 × 9–15(–18) mm, about equaling or longer than the sepals, glabrous with trichomes only present apically or sometimes subdensely lepidote (except for the always glabrous base and margins); blade (1–)3–15(–24) mm long; upper floral bracts shorter, bladeless, glabrous or with scarce trichomes towards the apex. Flowers 20–30 mm long, scentless; sepals mostly hidden by floral bracts, 12–23 × 3.2–8 mm, unequally connate, narrowly elliptic-ovate to narrowly ovate, pink to fuchsia, glabrous; abaxial sepal ecarinate, connate with the adaxial sepals for 0.1–0.4 mm (appearing free); adaxial sepals stronglY carinate, connate to each other for 10–16.7 mm (more than ⅔ of their length), and longer than the abaxial one; petals 21–33 mm long, spatulate; claw ca. 3.5 mm wide, basally semitransparent, then white and apically purple; limb 5–8 mm wide, divergent to spreading, elliptic, bluish-purple to dark purple, margins slightly irregular-crenate; stamens 12–21 mm long, included and visible (almost reaching the throat of the corolla), shorter to equaling the pistil; filaments 9–16 mm long, plicate for 0.7–2 mm in the apical half; pollen yellow; pistil 11–21 mm long, included (reaching the throat of the corolla) but visible at late anthesis; ovary 2.3–5.5 × 1.8–3.8 mm, obovoid-ellipsoid, clearly differentiated from the style; style 7–13 mm long, 1.7 to 3 times as long as the ovary, white; stigmas simple-erect to simple-patent. Capsules 20–34 × 3–4.2 mm, exceeding its respective floral bract, cylindrical-prismatic to very narrowly ellipsoid-prismatic, apex obtuse to rounded and short-beaked.

Vernacular names:— Clavel del aire ( Herter 1949 –1956; Lombardo 1984; Lombardo 1198 [MVJB]), clavel del aire común ( Brito & Llano 2008), clavel del aire azul ( Herter 1949 –1956), clavel del campo ( Herter 1949 –1956), flor del aire ( Herter 1949 –1956), flor del viento ( Herter 1949 –1956).

Classification:— Tillandsia aëranthos belongs to T. subg. Anoplophytum s.s., based on its morphological characteristics and the molecular phylogeny by Barfuss et al. (2005).

Distribution and habitat: — Brazil, Argentina, and Uruguay. In Argentina, Tillandsia aëranthos is distributed in the eastern region of the country mainly associated to the Pampean and Espinal phytogeographic provinces. In Brazil, its distribution is confined to the southern states of Santa Catarina and Rio Grande do Sul, in the latter being a very common species. Additionally, it was cited as a rare species for São Paulo state ( Wanderley & Martins 2007).

In Uruguay, T. aëranthos is the most common Bromeliaceae species, and one of the most frequent and broadly distributed vascular epiphytes ( Mai et al. 2019; Fig. 7 ). This species occurs throughout the country growing mainly as epiphyte in a variety of habitats, including all types of woodlands, isolated trees in grasslands, and it is also one of the few vascular plants able to grow as epiphyte even in hillside shrublands. Further, T. aëranthos is frequently found as epilithic growing on rocky blocks or walls associated to hillside forests. This species is also very abundant in urban areas, where it grows in parks, street trees, power lines, columns and walls. Tillandsia aëranthos shows a great habitat versatility as it was also found in coastal Pinus plantations, growing directly in pine leaf litter.

It should be noted that T. aëranthos together with T. bergeri Mez (1916: 254) , are the species of T. subg. Anoplophythum with the southernmost distribution. In this sense, T. aëranthos reaches its southernmost distribution in eastern Buenos Aires province, Argentina ( Guerrero 2020). Tillandsia aëranthos is morphologically very close to, and can be confused with T. tenuifolia Linnaeus (1753: 286) , a morphologically variable and widespread species in South America. Misidentification of materials of both species over time had led to erroneous citations of T. aëranthos in certain provinces of northwestern Argentina (e.g. Catamarca, Jujuy, Salta; Zuloaga et al. 2019) and in Paraguay (as reported for that country by Smith & Downs 1977 and Zuloaga et al. 2019).

Phenology:— In Uruguay, Tillandsia aëranthos flowers from mid-winter to mid-spring, mostly from late August to late October ( Fig. 4 ). Nevertheless, it is possible to find individuals flowering from late July (rarely from mid- July) to mid-November, depending on the climatic conditions of the year and those of each individual. Fruits begin to develop as of September and October and they continue to grow in length for about one month. Then they remain without growth until seed dispersal, between late spring and early summer (mostly in December and early January).

The development of the inflorescence (from the inflorescence emergence to the time the first flower opens) takes between one and two months and the complete reproductive cycle (from the onset of inflorescence emergence to the dehiscence of capsules) lasts from four to five months. This is a short reproductive cycle compared to those of the other species of Tillandsia occurring in Uruguay.

Reproductive observations:— The inflorescences of Tillandsia aëranthos have several flowers open at the same time ( Fig. 6E ). Each inflorescence remains with open flowers for approximately 20 to 50 days, depending on the number of flowers it bears and the time of the year (winter inflorescences last longer than spring ones). Individual flowers are open mostly from (9)10 to 18(23) days, which contrasts with the four to six days reported by Bianchi & Vesprini (2014) for Argentina.

It should be noticed that in T. aëranthos , the bracts are bright fuchsia since the beginning of the inflorescence emergence, and after the flowering period they dry up (along with the sepals), and change their color from pink to stramineous ( Fig. 6I ). This behaviour is in contrast to the morphologically similar T. recurvifolia and T. stricta in which after the flowering period bracts and/or sepals turn green and remain alive for several months.

According to Bianchi & Vesprini (2014), Tillandsia aëranthos is a self-incompatible species, whose flowers show apparent protandry. These flowers are pollinated by hummingbirds, which visit the flower sporadically and for very short periods of time ( Bianchi & Vesprini 2014; Bianchi 2009; and personal observations).

Conservation:— We consider Tillandsia aëranthos as Not Threatened in Uruguay. It is a common species with high frequency throughout its distribution range, inhabiting all types of habitats across the country. Nevertheless, we think that it is especially important to protect the epilithic populations that grow in some big hills of the “ Serranías del Este ” (see Note II) .

Diagnostic characters:— In Uruguay, Tillandsia aëranthos is the only species that combines spirally arranged flowers and sepals unequallY connate (the adaxial ones fused to each other for more than ⅔ of their length, the adaxial with the abaxial fused for less than 0.5 mm and appearing free). In the rest of the species with spirally arranged flowers, the sepals are equallY connate for less than ⅓ of their length ( Fig. 5A–E ; but see the hYbrid T. × marchesii ).

When sterile, T. aëranthos may be confused with T. ixioides , T. recurvifolia , or T. stricta , not only because they have a similar morphology but also because T. aëranthos has an overlapping distribution with all this three species. Tillandsia aëranthos differs from all of them in having symmetric trichomes with appressed wing throughout the blade, while the other three species have asymmetric trichomes, at least those located towards the base of the blade, and/or trichomes with spreading or divergent wing. Furthermore, T. aëranthos has generally well-developed stems in contrast to the acaulescent (or nearly so) T. recurvifolia and T. stricta , and their blades are not strongly rigid as in T. ixioides .

Background in Uruguay:— Tillandsia aëranthos was first cited for Uruguay in 1821 by Loiseleur-Deslongchamps in the original publication of its basionym, Pourretia aëranthos . It is worth noting that this species was the first Tillandsia cited for the country and one of the only two Bromeliaceae species mentioned in the first Flora of Uruguay ( Gibert 1873) along with Dyckia remotiflora Otto & Dietrich (1833: 129) .

Note I:— Several varieties of T. aëranthos have been described from Rio Grande do Sul, in southern Brazil [ T. aëranthos var. aemula Strehl (2000: 21) , T. aëranthos var. alba Strehl & Rohde (1998: 77) , T. aëranthos var. albobracteata Strehl (2004: 28) , T. aëranthos var. flava Strehl (2004: 28) , T. aëranthos var. rosea Strehl (2000: 22) ]. However, the status of these varieties (i.e. correct names vs. synonyms) varies according to the reference considered. The recognized varieties differ from the typical mainly in the color or size of flower parts and bracts. We consider that these characteristics are highly variable among the individuals of T. aëranthos , blurring the boundaries between the currently recognized infraspecific entities. In fact, we have registered individuals of T. aëranthos bearing flowers with petals of different colors in the same inflorescence. Given this fact, and in accordance with Tardivo et al. (2024), we decide not to recognize any infraspecific taxa for T. aëranthos .

Note II:— Based on the morphological, ecological, and phenological data, it is likely that there are more than one species inside the highly morphologically variable T. aëranthos in Uruguay. Nevertheless, there is not enough evidence supporting the recognition of new entities at this point. Population-level studies, including both molecular and morphological analyses, are needed to better understand how this species complex is taxonomically structured.

Note III: — Pourretia aëranthos was described by Loiseleur-Deslongchamps (1821) based on a plant from Montevideo ( Uruguay) and later cultivated in France.This species (under the genus Tillandsia ) was validly lectotypified by Smith & Downs (1977), who stated that “In the absence of any specimen the species is typified by the original illustration and description”. Despite the detailed drawings in the original illustration, they may not be sufficient for a precise application of the name, particularly because Tillandsia aëranthos belongs to a group of morphologically very similar species [e.g. T. bella Strehl (2000: 24) , T. jonesii Strehl (2000: 27) , T. polzii Ehlers (1997: 11) , T. tenuifolia , T. winkleri Strehl (2000: 28) ], some of which are difficult to distinguish from each other. Because of this, we have chosen the specimen Berro 6087, kept at MVFA ( Fig. 8), as the epitype of T. aëranthos (≡ Pourretia aëranthos ). Berro 6087 (MVFA) is a complete and well-preserved specimen, that bears several inflorescences and fits accurately with the original illustration and description of the species. Significantly, this specimen was collected in Montevideo ( Uruguay), the original locality of the plant on which the publication of P. aëranthos was based. It is important to note that T. aëranthos is the only species of T. subg. Anoplophytum that grows in this locality.

Note IV: —The name Tillandsia dianthoidea has been extensively used in herbarium specimens and in botanical literature in Uruguay and across the region, either as a correct name ( Mez 1894; André 1905; Herter 1930, 1949 –1956; Smith 1933) or as a synonym of T. aëranthos ( Smith 1943, 1972; Castellanos 1945; Cabrera 1968; Smith & Downs 1977; Lombardo 1984; Brito & Llano 2008; Zuloaga et al. 2019; Tardivo et al. 2024). However, when Rossi (1826) published T. dianthoidea , he included the name Pourretia aëranthos in the synonymy, effectively including the type of P. aëranthos , whose epithet ought to have been adopted when transferring the species to Tillandsia (ICN Art. 52.2(e); Turland et al. 2018). Based on this, we consider Tillandsia dianthoidea as a nomenclaturally superfluous name, deemed illegitimate under ICN Art. 52.1 ( Turland et al. 2018).

Note V: — Tillandsia microxiphion was described based on the single gathering identified as André k-323 (K000321912 and F0045287F). We choose the specimen K000321912 as the lectotype for T. microxiphion as, despite being just a small part of an individual, it is a complete specimen with more reproductive material than the other type material found (F0045287F). It should be noted that the locality “Cuaió” cited in the type specimen should be taken as a typographical error, intending to denote “Cuaró”, as there is no locality in Uruguay named “Cuaió”. Moreover , André visited Cuaró near the border with Brazil during his stay in Uruguay ( André 1905) .

Note VI: —The name Tillandsia bicolor has been extensively included by several authors in the synonymy of T. aëranthos (e.g. Smith 1972; Smith & Downs 1977; Zuloaga et al. 2019; Tardivo et al. 2024). However, after analysing the type materials (P00713156 and P00713157), the original drawing ( Brongniart 1829 [1834]), and also considering the localities of the type materials (Florianópolis Island, Santa Catarina, Brazil), we conclude that T. bicolor is indeed a synonym of T. tenuifolia , a morphologically variable species.

Representative specimens examined:— URUGUAY. Artigas: Cuareim , 17 August 1901, Berro 1758 ( MVFA) . Canelones: Cerrillos - Campo militar, 25 October 1936, Rosengurtt A-1222 ( BA, MVFA) . Cerro Largo: Arroyo Sarandí del Yí, en nacientes, a 5 km de Sierras de Ríos , 10 October 1999, Brussa & Grela s.n. ( MVFA 29375 ) . Colonia: Molino Quemado , 12 October 1957, Arrillaga 684 ( MVFA) . Durazno: Establecimiento Rincón del Río , 11 November 2016, Haretche 1030 ( MVFA) . Flores: Ruta 14 Trinidad-Cardona, 20 km al SW of Trinidad , Arroyo Guardia Vieja , 21 October 2004, Nyffeler & Eggli 1417 ( MVJB) . Florida: Parque Robaina, costa del Santa Lucía chico, 11 November 2012, Haretche 451 ( MVFA) . Lavalleja: Cerro Arequita, sobre el Río Santa Lucía , 22 September 1965, Del Puerto et al. s.n. ( MVFA 2195 ) . Maldonado: Cerro Pan de Azúcar , 20 October 1935, Rosengurtt B-1444 ( MVFA) . Montevideo: Montevideo , November 1878, Gibert 1091 ( MVM) . Paysandú: Cañada de San Miguel , cerca de su desembocadura, 27 December 2017, Rossado et al. 498 ( MVFA) . Rio Negro: Paso del Palmar , 18 October 1906, Berro 3543 ( MVFA) . Rivera: Cerro Chato Dorado , 10 October 2015, Rossado & Bonifacino 419 ( MVFA) . Rocha: Barra de Valizas , 18 January 2016, Rossado 437 ( MVFA) . Salto: Camino de Constitución a El Espinillar - Orilla del Arroyo Espinillar , 12 September 2001, Brussa et al. s.n. ( MVFA 29729 ) . San José: Sierra de Mahoma , 27 October 1963, Marchesi 805 ( MVFA) . Soriano: Juan Jackson, Estancia Santa Elena , October 1942, Rosengurtt et al. PE-5089 ( MVFA) . Tacuarembó: Gruta de los Cuervos , 2 December 2013, Rossado et al. 337 ( MVFA) . Treinta y Tres: El Yerbalito , 11 October 1902, Berro 2418 ( MVFA) .

Figures

FIGURE 4. Phenology of Tillandsia species occurring in Uruguay. Divisions within each month indicate intervals of approximately 10 days, identified as the beginning, middle, and end of each month. Tillandsia loliacea is excluded due to lack of enough information. * Denotes species with cleistogamous flowers. ** Denotes species with insufficient data to ascertain the timing of fruiting or fruit dehiscence.

FIGURE 5. Illustrations of floral parts. A. Tillandsia aëranthos. B. T. ixioides. C. T. × marchesii. D. T. stricta. E. T. recurvifolia. F. T.geminiflora. From left to right: floral bract (stretched view), sepals (stretched view; adaxial sepals to the right), petal (stretched view), and pistil.A based on Rossado et al. 29 (MVFA; floral bract and sepals) and Haretche 807 (MVFA; petal and pistil); B based on Rossado et al. 455 (MVFA); C based on Rossado 463 (MVFA); D based on Rossado et al. 200 (MVFA; floral bract, petal and pistil) and Rossado 412 (MVJB; sepals); E based on Rossado et al. 366 (MVJB); F based on Rossado 17 (MVFA; floral bract, petal, and pistil) and MVFA 440 (sepals).

FIGURE 6. Tillandsia aëranthos. A. Flowering plants on Butia odorata (near Paso Centurión, Cerro Largo, Uruguay). B. Habitat; forest near Laguna Negra (Rocha, Uruguay). C. Habit (Montevideo, Uruguay). D. Plant releasing the seeds (Quebrada de Los Cuervos, Treinta y Tres, Uruguay). E. Lateral view of the inflorescence. F. Front view of the inflorescence. G. Lateral view of the flower; notice floral bract to the left, strongly clasping the flower, and the highly connate adaxial sepals to the right. H. Lateral view of the flower with the calyx removed, showing only one petal and two stamens. I. Infructescence. Photos by Andrés Rossado.

FIGURE 7. Distribution map of Tillandsia aëranthos in Uruguay and neighboring areas.