Tillandsia arequitae (André) André ex Mez (1896: 814)

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

2. Tillandsia arequitae (André) André ex Mez (1896: 814) . Figs. 9A , 10 , and 11.

≡ Tillandsia xiphioides var. arequitae André (1893: 156) . Type (lectotype, first-step designated by Smith 1935: 169 [as “type”]):— URUGUAY. [Lavalleja]: “Grotte d’Arequita, prov. de Minas ”, 3 October 1890, André k- 320 p. p. (K [two specimens], second-step lectotype designated here: K000321922 [online image!]; syntypes: F0045276F [online image!], GH00093911 [online image!], NY00329214 [online image!]).

Plants caulescent, much branched from the base and forming dense clumps up to 1.5–2 m in diameter but generally smaller, seldom not branched. Roots up to 3 mm in diameter, present all along the stem. Stems well developed, up to 2.5 m long but frequently shorter, pendant for most of its length and apically ascending. Leaves spirally arranged, clustered apically forming a rosette, gray; sheaths 15–30 mm wide, gradually merging into blades, densely lepidote except for the glabrous very base; blades 50–130 × (8–) 10–30 mm, spreading to reflexed, narrowly triangular, flat at the base and then gradually channelled towards the apex (rarely slightly channelled at the base), fleshy, densely tomentose-lepidote throughout, trichomes asymmetric. Inflorescences simple; peduncles wholly covered by bracts, (4.5–) 6.5–14.5 cm long, ca. 2.5 mm in diameter, glabrous; peduncle bracts 6 to 10 in number (the basal ones leaf-like), erect, evenly distributed along the peduncle and densely imbricate (ca. 2–3 times longer than the internodes); upper peduncle bract bladeless, 22–50 × 9–13 mm, narrowly elliptic to narrowly ovate-elliptic, green to grayish-green, subglabrous to subdensely lepidote, occasionally wholly glabrous or sometimes with trichomes present only in the middle portion. Spike distichously and densely (3)5 to 12(15)-flowered, (40–) 50–120 mm long, strongly complanate, narrowly elliptic in outline; rachis totally hidden by the floral bracts or sometimes partially exposed, green, glabrous. Floral bracts densely imbricate, 2.5–4.7 times longer than the internodes, clasping the basal half of the flower, bladeless, narrowly elliptic-triangular to narrowly ovate-triangular, ecarinate, greenish to yellowish, glabrous (seldom only the most basal bract with scattered trichomes in the middle portion); basal floral bracts 22–44 × 8–13.5 mm, exceeding the sepals by 3–9(–12) mm. Flowers 34–55 mm long, softly fragrant; sepals hidden by floral bracts, 17–31 × 5–8.5 mm, evenly very short connate at the base for less than 1 mm (appearing free), narrowly elliptic to narrowly oblong, sometimes narrowly obovate-elliptic, light green to yellowish-green, glabrous; abaxial sepal ecarinate; adaxial sepals strongly carinate, and generally longer and wider than the abaxial one; petals 40–55(–67) mm long, spatulate; claw 2.5–4.2 mm wide; limb (7.5–) 11–17 mm wide, spreading, widely elliptic to orbicular, white, margins crenate; stamens 27–42 mm long, barely included (about equaling the petal claw), slightly shorter than the pistil; filaments 23–35 mm long, straight (not plicate); pollen yellow; pistil 30–40 mm long, slightly exserted; ovary 5–8 × ca. 2.8 mm, ovoid to ovoid-ellipsoid, tapering into the style; style 22–35 mm long, ca. 4–7 times as long as the ovary, white; stigmas simple-patent. Capsules 17–27 × 4–5.5 mm, not exceeding its respective floral bract, narrowly ellipsoid-prismatic, apex acute-obtuse and beaked.

Vernacular names:— Clavel del aire blanco ( Herter 1949 –1956; Brito & Llano 2008), Clavel del aire del Arequita ( Brito & Llano 2008).

Classification:— Tillandsia arequitae belongs to T. subg. Aerobia , based on its morphological characteristics and the molecular phylogeny by Vera-Paz et al. (2023).

Distribution and habitat:— Tillandsia arequitae is an endemic species to Uruguay, restricted to the south of the “Sierra del Este” geomorphological region, in Lavalleja and Maldonado departments ( Fig. 11 ). This xeromorphic and epilithic species grows mainly on vertical and fully sun-exposed rocky surfaces, usually forming dense populations of profusely branched and long-caulescent plants. Moreover, T. arequitae occasionally grows as an epiphyte on trees close to the rocky surfaces where it is more abundant. This species commonly establishes almost exclusive communities ( Fig. 10A ) although sometimes it cohabits with other xerophytic vascular plants (mainly Cactaceae species).

The largest population of T. arequitae is found in Arequita hill (Lavalleja; Fig. 2A ), which is both the type locality and the place after which the specific epithet was coined. However, it should be noticed that T. arequitae is a rare species. So far, no more than 10 populations have been recorded, most of which are distant from each other. Given this situation, and the fact that the habitat is so specific and highly discontinuous, we hypothesize that very scarce to no gene flow may occur between several of its populations. This is also in part supported by morphological differences noticed among some of the localities where T. arequitae occurs. Nevertheless, we consider that new populations could possibly be discovered in less explored hills of the southern parts of “Sierra del Este”.

Phenology:— Tillandsia arequitae flowers in spring, from late October to early December, with the peak blooming period in November ( Fig. 4 ). Fruiting occurs mainly as of December and seed dispersal from late February to April (late summer–early autumn). The complete reproductive cycle (from the onset of the inflorescence emergence to the dehiscence of capsules) takes from seven to eight months.

Reproductive observations:— In Tillandsia arequitae , well-developed inflorescences are in flower for about 20 to 30 days. The number of open flowers at any given time per inflorescence is generally two but it can vary from one to three. Individual flowers remain open from four to six days, and once they wither their petals change from white to semi-transparent (as it similarly occurs in T. uruguayensis and T. xiphioides ). After the flowering period, peduncle and floral bracts turn stramineous and dry up ( Fig. 10I ).

Conservation assessment:— The estimated EOO and AOO for Tillandsia arequitae were 2,780 km 2 and 44 km 2, respectively. This Uruguayan endemic species is known from about ten different scattered populations, none of which occurs in national protected areas. Most of these populations grow in well-preserved habitats and each of them consists of a relatively low number of individuals (except Arequita Hill). At Arequita Hill, T. arequitae is threatened by recreational activities such as rock climbing, as it grows on nearly vertical rock walls where climbing routes are placed. Additionally, since it is a rare and ornamental species, T. arequitae is extracted from its natural habitat for illegal trade.

Considering these factors alongside the EOO and AOO results, and in accordance with the B criterion of the IUCN guidelines, we tentatively propose classifying T. arequitae as Endangered (EN). Furthermore, it is crucial to emphasize the necessity for adequate protection measures to safeguard this species from the risk of extinction in the wild. Tillandsia arequitae is considered as a priority for conservation in Uruguay by Marchesi et al. (2013).

Diagnostic characters:— Tillandsia xiphioides is the taxon that morphologically shows the greatest likeness to T. arequitae . In fact, T. arequitae was first described as a variety of the former species. In the identification key of Smith and Downs (1977), T. arequitae is differentiated from T. xiphioides by the presence of an elongated peduncle, largely exposed vs. a short peduncle, largely hidden by the leaves. Although these characteristics are present in all the specimens of T. arequitae , several specimens of T. xiphioides have highly developed peduncles that greatly exceed the rosette of leaves. Therefore, the length and exposure of the peduncle should not be used as the only criterion to separate this species.

In this sense, Tillandsia arequitae can be properly distinguished from T. xiphioides by its peduncle bracts 2 to 3 times longer than the internodes (vs. at least 4 times longer), basal floral bracts 22–44 mm long (vs. 45–85 mm long and strictly equal to or more than 55 mm long within the distribution range of T. arequitae ), and petals less than 70 mm long (vs. more than 80 mm long). The length of the basal floral bracts is an easily measurable and useful character to differentiate these two species even in herbarium specimens, although occasionally this value could be close between the species. In this sense, the longer floral bracts in T. arequitae are found in well-developed inflorescences and in this case are always shorter than the rachis, while the shorter floral bracts in T. xiphioides (and therefore close to the higher value for T. arequitae ) are found in small inflorescences and are always much longer than their rachis. Further, T. arequitae has softly fragrant flowers, and patent petals with shortly crenate margins, while T. xiphioides has strongly fragrant flowers and reflexed petals (sometimes even strongly recurved or weakly helicoid) with conspicuously crenate-serrate margins. It should be noticed that even though T. arequitae and T. xiphioides grow in similar habitats, they have not been found cohabiting.

Background in Uruguay:— The basionym of Tillandsia arequitae was published in 1893 based on the first herbarium specimens of this species, which was collected in Uruguay in 1890.

Note I:— In the protologue of Tillandsia xiphioides var. arequitae, André (1893) indicated that the material upon which he based his description was collected by himself in Gruta de Arequita in October 1890 (single gathering). In accordance with this information, five specimens (syntypes) were found at K, F, GH and NY, all of them with the collector number “k-320”. Smith (1935) considered André k-320 at K as “type” (later cited as the “ holotype ” in Smith & Downs 1977), thus making an inadvertent lectotypification ( Prado et al. 2015; ICN Art. 9.10, Turland et al. 2018). This statement can be taken only as the first step of a lectotypification (ICN Art. 9.17, Turland et al. 2018), narrowing the choice to a specimen at K, as two specimens of André k-320 were found at K (K000321921, K000321922). Here, we discard the specimen K000321921 as type material of T. xiphioides var. arequitae because, despite it having the same label information as the other André k- 320 specimens, it undoubtedly corresponds to T. xiphioides var. xiphioides . Hence, we designate K000321922 as the second-step lectotype, as it is a complete and well-preserved herbarium specimen that perfectly fits the diagnosis and tabula of T. xiphioides var. arequitae .

Note II:— The labels on all specimens collected by André, bearing the collection number K-320 (i.e., F0045276F, GH00093911, K000321922, and NY00329214 ), indicate the date “ 3 October 1890,” corresponding to É. André’s visit to Arequita Hill. The presence of past inflorescences and the lack of flowers of three of these specimens (i.e. F0045276F, GH00093911, and NY00329214 ) matches the phenology of the species and the information given in the protologue “La plante tapissait d’immenses rochers à pic, surplombant la grotte d’Arequita… couverts des mapes desséchées de la floraison précédent.”. However, the specimen K000321922 bears flowers, suggesting a later pressing date than indicated on the label. This is in agreement with André (1893) who explicitly indicated that he collected several specimens past flowered for cultivation and that he succeeded in getting them to set flower in boreal spring (“Je recueillis un certain nombre d’exemplaires vivants que je rapportai en Europe et dont j’attendis la floraison pour en faire la détermination. Cette floraison eut lieu au printemps de 1892.”). Consequently, we conclude that the specimen K000321922 was obtained in 1892 from cultivated plants collected in Arequita Hill in 1890. Notwithstanding the fact that the other specimens (F0045276F, GH00093911, and NY00329214 ) have the same collection number, we consider them a different gathering and therefore their status remains as syntypes.

Note III:— In the Flora e Funga do Brasil database ( Tardivo et al. 2024), Tillandsia arequitae is treated as a heterotypic synonym of T. xiphioides . However, T. arequitae has sufficient morphological differences from T. xiphioides to warrant recognition as an independent entity (see Diagnostic characters). Additionally, the phylogeny presented by Vera-Paz et al. (2023), based on molecular data, places T. arequitae and T. xiphioides within the same clade but not as sister taxa. Due to these considerations, we do not follow Tardivo et al. (2024), and consequently, we maintain T. arequitae as an accepted species.

Representative specimens examined:— URUGUAY. Lavalleja: Cerro Arequita , 2 December 1900, Berro 1399 ( MVFA) . Maldonado: 7, 5 km al noreste del pueblo Garzón ( Predio de Bodegas Garzón ), 2016, Rossado & Pinelli 460 ( MVJB) .

Figures

FIGURE 2. Native forests from Uruguay. A. Xeric hillside forest (“bosque serrano”;Arequita Hill, Lavalleja). B–C. Moist hillside forest (“bosque de quebrada”; B: near Bajada de Pena, Rivera; C: near Estación Ataques, Rivera). Photos A and C by Mauricio Bonifacino; B: Andrés Rossado.

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 9. Illustrations of floral parts. A. Tillandsia arequitae. B. T. uruguayensis. C. T. xiphioides. From left to right: floral bract (stretched view), sepal (stretched view), petal (stretched view), and pistil. A based on Rossado 402 (MVFA); B based on Rossado & Bonifacino 418 (MVFA); C based on Rossado 377 (MVJB).

FIGURE 10. Tillandsia arequitae. A. Habitat; one of many rock walls of Arequita Hill (Lavalleja, Uruguay). B. Habit (Arequita Hill). C. Front view of a clump. D. Plant with inflorescences. E. Front view of the flower. F. Lateral view of the flower with its floral bract partially removed. G. Capsule (floral bract and sepals removed). H. Close up of the fertile part of the inflorescence. I. Infructescence. Photos by Andrés Rossado.

FIGURE 11. Distribution map of Tillandsia arequitae.