Tillandsia Linnaeus (1753: 286)

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

Tillandsia Linnaeus (1753: 286) . Type:— Tillandsia utriculata Linnaeus (1753: 286)

Herbs, acaulescent to long-caulescent, not-branched to strongly branched and then forming dense clumps. Roots always present, rarely absent when adult. Leaves simple, spirally or distichously arranged, distributed along the stem or clustered forming a rosette, light green to gray, or violaceous; sheaths from almost indistinguishable from the blade to clearly differentiated, completely hidden by other leaves to completely visible, generally strongly clasping the stem; blades linear to narrowly triangular, flat to terete, thin to fleshy, densely lepidote throughout, margin entire; trichomes peltate, symmetric to strongly asymmetric, closely appressed to spreading. Inflorescences racemose, terminal, simple, compound, or sometimes single-flowered; peduncles distinct, ebracteate to wholly covered by bracts; fertile part of the inflorescence with distichously or spirally arranged flowers; floral bracts always present, densely lepidote to glabrous, gradually reducing in size towards the apex of the inflorescence. Flowers perfect, actinomorphic, scentless to strongly fragrant; sepals 3, clasping the basal portion of the flower, equally or unequally connate (only the adaxials highly connate), sometimes appearing free, ecarinate to strongly carinate, glabrous to densely lepidote; petals 3, free, lingulate to spatulate, glabrous; stamens 6, free, included, all equal in length, shorter to longer than the pistil; filaments sublinear, flat, straight or with a plicate portion in its apical half; anthers linear, basifixed to subbasifixed, longitudinal dehiscence, pollen orange to yellow, or white; carpels 3, connate; ovary partially inferior although superior in appearance, ovules numerous, placentation axile; style 1, shorter to many times longer than the ovary, cylindrical; stigmas lobes 3, elongated to truncate, erect to spreading, straight, recurved or spirally twisted. Fruits elongated septicidal capsules, base of the style generally persistent at the apex of the capsule as a beak. Seeds numerous, fusiform, with a white feathery appendage at the apical end.

Diversity:—Within Bromeliaceae , Tillandsia is the largest genus in Uruguay. It is represented by 17 species and one natural hybrid, belonging to four subgenera and one species complex: Tillandsia subg. Aerobia (3 spp.), T. subg. Anoplophytum (4 spp. + 1 hybrid), T. subg. Diaphoranthema (8 spp.), T. subg. Phytarrhiza (1 sp.), and T. gardneri complex (1 sp.) ( Table 1). Two species are endemic to Uruguay ( T. arequitae and T. uruguayensis ) and two are exotic and subspontaneous, mainly occurring in Montevideo city ( T. capillaris and T. virescens ).

Distribution and habitat:—The genus Tillandsia is distributed throughout Uruguay, inhabiting all types of woody vegetation (forest and shrublands), isolated trees in grasslands, rocky outcrops, as well as urban areas. Only three species are broadly distributed across the country ( T. aëranthos , T. recurvata , and T. usneoides ), while the remaining have a distribution restricted to some specific habitats and/or to particular regions or localities. In this sense, nine of the 15 native species ( T. aëranthos , T. bandensis , T. duratii , T. ixioides , T. loliacea , T. recurvata , T. recurvifolia , T. tricholepis , and T. usneoides ) and one natural hybrid ( T. × marchesii ) live in the open thorn forests associated to the plains of the northern strip of land along the Uruguay River ( Fig. 3 ). It is in these forests, influenced by the Espinal phytogeographic province ( Fig. 1A ), where the highest specific diversity of Tillandsia in Uruguay is found. Other extensive areas with high number of species are the woods associated to the Laguna Merín basin in the east of the country, the southern region of “Sierras del Este” and the northern region of “Cuchilla de Haedo” hill systems, placed in southern and northern Uruguay, respectively ( Fig. 3 ).

In terms of habit, with 14 predominantly or exclusively epiphytic and three exclusively epilithic species, Tillandsia is the richest genus of the epiphytic flora of Uruguay ( Mai et al. 2019) and one of the main components of the epilithic vegetation. It should be noticed that all the species of Tillandsia occurring in Uruguay are categorized as atmospheric, as they are non-tank plants that depend almost exclusively on absorptive leaf trichomes for water and nutrient uptake ( Benzing 2000).

Phenology: —All the species of Tillandsia occurring in Uruguay are polycarpic and exhibit an annual and a regular flowering pattern. The annual flowering pattern occurs at both individual and at population levels because each plant flowers only once a year and all the plants of the same population flower approximately at the same time, while the regular flowering pattern for each species is due to the little variation in the flowering time among years. It is worth mentioning that, within a year, the duration of the flowering period shows significant variation among species ranging from less than a month (e.g. T. recurvata ) to approximately three months (e.g. T. duratii ). In Uruguay, there are species of Tillandsia in flower for approximately six months, from mid-winter (July) to early summer (late January) ( Fig. 4 ).

In Tillandsia the onset of the inflorescence emergence is evidenced by the bulging of the apex of the stem, which depending on the species it could share the same color as the floral bracts (e.g. T. aëranthos ), or have the same color as the leaves and therefore be barely noticeable (e.g. T. uruguayensis ). The development of the inflorescence, excluding the flowering period, takes from a few weeks (e.g. T. stricta ) to several months (e.g. seven to eight months in T. myosura ). After the flowering period, it is quite constant among species that the fruits grow in length rapidly for about a month. Then, they remain without any apparent growth until seed dispersal. The timing of this last stage (between fruit stop growing in length to seed dispersal) is highly variable depending on each species, being able to take from less than a month as in T. aëranthos to approximately a year in T. virescens ( Fig. 4 ). In Uruguay, there are species of Tillandsia dispersing its seeds along the whole year.

The complete reproductive cycle of Tillandsia in Uruguay, i.e. from the onset of the inflorescence emergence to the dehiscence of its fruits, lasts from four to five months in species such as T. aëranthos and T. recurvifolia , to about a year and a half in T. duratii and T. myosura ( Fig. 4 ).

Conservation:— Eight species and one subspecies of Tillandsia were classified as threatened for Uruguay, i.e. ca. 55% of Tillandsia native species ( Table 1). This relatively high number of threatened species is due to the fact that most species of Tillandsia within Uruguay show narrow distributions, mainly associated to poorly represented woodlands strongly influenced by neighboring phytogeographic provinces (i.e. Espinal or Paranaense).

Seven of the 15 native species of Tillandsia in Uruguay occur in protected areas included in the National System of Protected Areas (Sistema Nacional de Áreas Protegidas—S.N.A.P.), however, only one of them (and one subspecies) were classified as threatened (i.e. T. bandensis subsp. grandipetala and T. uruguayensis ). It should be warned that threatened species not occurring within conservation areas are in a highly vulnerable situation. Most of them grow in open thorn forests ( Fig. 1A ), a habitat that has experienced noticeable area reduction and fragmentation as a result of the strong agricultural pressure.

Figures

FIGURE 1. Native forests from Uruguay. A. Open thorn forest (“bosque parque”; near Paso de Las Cadenas, Río Negro). B. Palm forest (“palmar”; near Laguna Negra, Rocha). C. Riverside forest (“bosque ribereño”; Sopas stream, Salto). Photos by Mauricio Bonifacino.

FIGURE 3. Diversity of Tillandsia in Uruguay as indicated by the number of Tillandsia species per 45 × 45 km grid cell.

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.