Aosa Weigend (2006: 464)

Acuña, Rafael, Chinchilla, Isler F. & Weigend, Maximilian, 2018, An unusual disjunction in Loasaceae: Central American Chichicaste grandis is nested in Brazilian Aosa, Phytotaxa 365 (3), pp. 273-287 : 282-285

Aosa Weigend (2006: 464)

Type species:— Aosa parviflora (Schrad. ex DC.) Weigend (2006: 464) . Basionym: Loasa parviflora Schrad. ex De Candolle (1828: 342)

Heterotypic synonym: — Chichicaste Weigend (2006: 464–465) . Type species: Chichicaste grandis (Standl.) Weigend (2006: 465) . Basionym: Loasa grandis Standley (1927: 12)

Aosa grandis (Standl.) R.H.Acuña & Weigend , comb. nov. Basionym: Loasa grandis Standley (1927: 12) . Homotypic synonym: Chichicaste grandis (Standl.) Weigend (2006: 465) .

Type: — COSTA RICA, Guanacaste: Vicinity of Tilarán [on the road to El Silencio], 500–650 m, 10–31 January 1926, P. Standley & J. Valerio 44558 (holotype: US barcode US 00115209!, isotype: US barcode US 00603972!).

Notes:— There is some variation in vestiture between populations: those in the eastern part of the range, especially in Darién, have more abundant, longer, conical to falcate scabrid trichomes on the adaxial lamina, interspersed between the shorter, pustule-shaped trichomes. The ovaries in plants from Arenal, Chagres and Darién are densely covered in stinging trichomes, while those from San José, Puntarenas and Antioquia have fewer stinging trichomes. Specimens from the Chagres Basin differ from other populations by the presence of pseudostipules and decurrent bracts, but their size and development seem variable (cf. the much larger structures in C. Dodge & P. Allen 17336 with those of W. Lewis et. al 3491). Despite this, the trichome cover and floral morphology of these specimens show no significant differences from other Aosa grandis populations. Confirmation if these populations deserve taxonomic recognition will require further study, especially in living plants. Irrespective of their origin and morphological variability, the presence of short-pustulose scabrid trichomes and the absence of smooth-shafted glochidiate trichomes on intercostal areas of the adaxial lamina, is constant in all material studied ( Fig. 3 ).

Distribution:— This species is endemic to the Costa Rica-Chocó biogeographic hotspot in Costa Rica, Panama and Colombia ( Fig. 5 ). According to Morales (2007) and our own observations, populations in Costa Rica are mainly found in three areas: the Arenal Basin (Tilarán, Guanacaste, and adjacent Alajuela), eastern Cartago, and the Wet Premontane Central Pacific Region (southern San José and adjacent Puntarenas). In Panama, populations are known from the Antón Valley area (Coclé), the Chagres Basin ( Panamá) and eastern Darién. In Colombia it is known from northwestern Antioquia.

Phenology:— This species appears to flower more profusely between December and April, while fruiting seems to take place mostly from March to May.

Habitat and ecology:— Aosa grandis is found in wet to rain forests, 70–1300 m elevation, being most abundant between 600–1000 m. It is uncommon and local throughout much of its range ( Standley 1927, Weigend 2001). It has been collected mostly near forested river or streams banks, on shallow, but humus rich soils, often on steep slopes. Short-tongued hymenopterans visit the flowers in Costa Rica. From our own observations of plants in Quepos in March 2017, most of the flowers studied (> 80%) set fruit.

Etymology:— Aosa is a partial anagram of Loasa , the genus from which it was segregated, while grandis refers to the large size of this species.

Conservation status:— Aosa grandis grows in low densities in extensively forested areas, but it can withstand some habitat fragmentation, as long as some forest remains unaltered e.g. on steep slopes flanking watercourses. In Costa Rica, most known specimens have been collected outside protected areas, but some come from within the current limits of PN (Parque Nacional) Volcán Arenal, PN Barbilla, Refugio de vida silvestre La Marta and PN Los Quetzales. On the other hand, in Panama most collections come from inside or close to currently protected areas, most notably Monumento Natural Cerro Gaital, PN Chagres and PN Darién. Previous records from the Reserva Forestal de Fortuna, Chiriquí, belong to the Critically Endangered Nasa panamensis . There is only one collection known from Colombia (F. López & M. Sánchez 44). The other specimen reported for the country by Weigend (2001), S. Espinal 4678 (MEDEL!), is actually Nasa triphylla (Juss.) Weigend in Weigend et al. (2006: 82) subsp. papaverifolia (Kunth) Weigend in Weigend et al. (2006: 82). Villa Arteaga is close to (but outside) the current limits of PNN (Parque Nacional Natural) Paramillo ( Ministerio de Ambiente y Desarrollo Sostenible de Colombia 2002 -Ongoing). This area still remains poorly explored by botanists as the armed conflict precluded scientific research for ca. five decades (M. Vélez, pers. comm.). It is possible that this species could still be found elsewhere on the western slopes of the northwerstern end of the Andes close to PNN Paramillo as well as in PNN Los Katíos (the species is known from adjacent PN Darién close to the international border) or in Serranía del Baudó. Although not officially assessed by the IUCN, we recommend this species to be treated as VU C2a(i); E following the red list criteria ( IUCN 2001) due to its low population density, small inferred population size and apparent low tolerance to human disturbance.

Additional specimens examined:— COSTA RICA. Guanacaste: Can. Tilarán, Río Chiquito , bajos de San Pedro. Bosque muy húmedo tropical/premontano, 650–700 m, 15 January 1987, W. Haber & E. Bello 6594 ( MO) ; Río Negro ford on south side of Lake Arenal ; slope and ridges; 10 km NNE of Santa Elena. In premontane wet forest, 600–800 m, 9 May 1986, W. Haber et al. 4902 ( MO) ; Alajuela: [Can. San Ramón?] San Gerardo, Río Caño Negro, Finca de Chavarría , 800 m, 11 January 1989, E. Bello 646 ( CR, MO) ; Cartago: Can. Turrialba, Margen izquierda de Quebrada Jesús. Afluente innominado. Camino a Cerro Tigre , 800 m, 22 March 1996, G. Herrera & G. Valverde 8844 ( CR, F, MO, USJ; Prov. Limón is apparently erroneous) ; A 16 km SE de Turrialba camino a Puerto Limón. Selva alta perennifolia en cañada, 768 m, 21 February 1982, O. Téllez et al. 5310 ( CR) ; 13 km E of Turrialba on the Hwy to Limón. Canyon of Río Chitaría , 750–800 m, 10 May 1983, R. Liesner et al. 15441 ( CR, MO) ; Río Chitaría, on road Turrialba-Limón , forest on steep slope, 700 m, 17 February 1991, P. Maas 7982 ( CR, F, MO, U) ; Route 10, road between Turrialba and Siquirres , Río Chitaría Canyon. On the steep slopes on the side of the road and river, 768 m, 15 December 2015, R. Acuña et al. 1223 ( BONN, USJ) ; ditto, 05 March 2017, R. Acuña et al. 1747 ( USJ) ; Can. Jiménez, Pejibaye, Centro histórico RVS La Marta, cuenca del Reventazón , 781 m, 05 January 2010, R. Kriebel & D. Santamaría 5447 ( CR) ; San José: Can. Puriscal, Cuenca del Tulín. 2 km antes de San Rafael, a orillas del río, 1274 m, 09 December 2004, A. Soto et al. 438 ( CR) ; Can. Aserrí, Cuenca del Pirrís-Damas, Fila Aguabuena , Quebrada Laja , 1100-1200 m, 23 January 2003, J. Morales & B. Hammel 9055 ( CR) ; Cuenca del Pirrís-Damas. A lo largo de Quebrada Laja, Ca. 2.5 km al noreste de altos. El Aguacate, 800–900 m, 24 January 2003, B. Hammel et al. 22686 ( CR) ; Cuenca del Pirrís-Damas, Fila Bustamante, Fila Aguabuena , entre Quebrada Chilamate y Quebrada Pilas, camino, 1300 m, 12 December 1996, J. Morales 5923 ( CR; Can. Acosta is apparently erroneous) ; Can. Tarrazú, Cuenca del Naranjo y Paquita. San Isidro , Quebrada Seca , 2 Km antes de San Isidro, viniendo de Nara , 800 m, 05 March 2008, J. Morales 15960 ( CR) ; Can. Pérez Zeledón, R.F. Los Santos. California . Camino entre California y Zaragoza, 1000 m, 06 March 2001, A. Estrada et al. 2810 ( CR) ; Puntarenas: Can. Quepos, Distrito Savegre, Dos Bocas, propiedad privada. Bosque muy húmedo tropical, en claros de bosque ripario, a la orilla de la quebrada, 570 m, 02 March 2015, I. Chinchilla & O. Chinchilla 2455 ( USJ) ; ditto, 15 April 2017, I. Chinchilla & O. Chinchilla 3138 ( USJ), Dos Bocas, Rio Hatillo Basin creek , 584 m, 08 January 2016, R. Acuña et al. 1264 ( BONN, USJ) . — PANAMA. Coclé: North rim of El Valle de Antón , 600–1000 m, 12 February 1939, P. Allen 1658 ( MO) ; La Mesa, near El Valle , 800 m, 18 January 1968, J. Dwyer & J. Duke 8250 ( MO) ; 3.5 miles NE of El Valle near Los Llanos along deep forested draw, Atlantic slope-headwaters of the Rio Indio , 800 m, 25 April 1979, B. Hammel 7168 ( MO, PMA, US) ; 2.5 miles from El Valle on road to La Mesa, 11 February 1971, T. Croat 13381 ( MO) ; La Mesa region N of Cerro Gaital vicinity of El Valle. Roadside and disturbed forest, 800 m, 02 July 1978, B. Hammel 3867 ( MO) ; [Panamá?]: Forest along banks of Quebrada La Palma and cañón of R. Chagres, 70–80 m, 09 January 1935, C. Dodge & P. Allen 17336 ( MO, P, U) ; Panamá: Tributary of Rio Chagres , 5 miles SW of Cerro Brewster. Sandy and rocky river banks, 300 m, 14 December 1967, W. Lewis et. al 3491 ( MO) ; Darién: Río Pucuro base camp, Río Pucuro between Cerro Mali and Cerro Tacarcuna, 650 m, 24 January 1975, A. Gentry & S. Mori 13871 ( MO) ; Banks of river below Rancho Frío (upper), 400 m, March 1985, W. D’Arcy & G. McPherson 16217 ( MO) . — COLOMBIA. Antioquia: Mun. Mutatá, Selva Pluvial , carretera al mar, cerca de Villa Arteaga, 150 m, 06 December 1948, F. López & M. Sánchez 44 ( MEDEL, US) .

Key to the species of Aosa (Modified from Weigend 1999 and Henning et al. 2017)

1. Leaves strictly opposite and equal........................................................................................................................................ A. uleana

-. Leaves alternate, rarely in very unequal pairs (one leaf 3–10 times larger than the other, A. rostrata only).....................................2

2. Inflorescences alternating with two leaves on stem...........................................................................................................................3

- Inflorescences terminal, or in axil of leaf...........................................................................................................................................4

3. Fruit practically indehiscent and densely covered with tack-shaped glochidiate trichomes (burr). Dorsal filaments of floral scales and the two staminodia of each complex with expanded apices ........................................................................................ A. plumieri

-. Fruit opening with well developed apical valves and covered with scabrid trichomes. Dorsal filaments of floral scales and the two staminodia in each complex with filiform apices............................................................................................................ A. parviflora

4. Mature leaves often exceeding 30 cm in length. Corolla bowl shaped, unicolored, greenish. Petals overlapping in anthesis, with poorly differentiated claw and limb..................................................................................................................................... A. grandis

-. Mature leaves rarely exceeding 20 cm in length. Corolla star shaped, often bicolored, predominantly white, rarely greenish, petals not overlapping in anthesis, claw and limb clearly differentiated......................................................................................................5

5. Inflorescence foliose, without long leafless stalk. Capsule with long terminal beak.........................................................................6

-. Inflorescence leafless, with long, leafless stalk. Capsule without long terminal beak.......................................................................7

6. Plants usually <0.8 m tall, setose. Capsule over 75% superior ......................................................................................... A. rostrata

-. Plants usually> 1 m tall, virtually esetose. Capsule with inferior portion making up to 50% the total length .............. A. sigmoidea

7. Inflorescence stalk (in dry material) not thickened at base. Secondary leaf veins in ≥7 pairs, parallel, all ending in teeth, margin shallowly and regularly dentate.......................................................................................................................................... A. gilgiana

-. Inflorescence stalk (in dry material) abruptly thickened at base. Secondary leaf veins in 2–4 pairs, divergent, upper ones not ending in teeth, margin irregularly serrate and lobate................................................................................................................... A. rupestris

Figures

FIGURE 3. Ultrastructure of mature leaf surfaces. Chichicaste grandis from Cartago, Costa Rica (Acuña et al. 1223 USJ, BONN): A, Overview of adaxial surface, inset: detail of a short, pustule shaped scabrid trichome; B, Overview of abaxial surface; Nasa panamensis from Chiriquí, Panama (Antonio 2885, MO): C, Overview of adaxial surface, inset: detail of a smooth-shafted glochidiate trichome; D, Overview of abaxial surface; Aosa uleana from Rio de Janeiro, Brazil (Jossberger 342, BONN): E, Overview of adaxial surface, inset: detail of a long scabrid trichome; F, Overview of abaxial surface. Scale bars: A, C: 500 μm, insets: 30 μm; B, D, F: 100 μm; E: 200 μm, inset: 100 μm. GL: Gloquidiate trichome; SC: Scabrid trichome; ST: Stinging trichome.

FIGURE 5. Known distribution of Chichicaste grandis relative to the most important protected areas (bright green) of Southern Central America and Northwestern Colombia.