Struthanthus venetus (Kunth) Blume

Maldonado-Borja, Maria Guadalupe, Miguel-Vázquez, Mónica Isabel, Espejo-Serna, Adolfo & Cerros-Tlatilpa, Rosa, 2024, Reinstatement of Struthanthus venetus (Loranthaceae): an endemic species of central Mexico, PhytoKeys 249, pp. 75-94 : 75-94

Struthanthus venetus (Kunth) Blume , Syst. Veg. (ed. 15 bis) 7 (2): 1731. 1830.

Fig. 1 A – F

Loranthus venetus Kunth , Nov. Gen. Sp. (quarto ed.) 3: 434. 1818 [1820].

Loranthus volubilis Sessé & Moc. , Pl. Nov. Hisp.: 51. 1888. Type: Quahunahuacae arboribus [Cuernavaca, Morelos], M. Sessé et al. s. n. (lectotype, designated by Nelson 1997, pg. 401: MA- 600707!; Cuatrec. No. 924; Neg. / Types: F- 46623).

Type material.

Mexico • Morelos: crescit in Regno Mexicano, prope Cuernavaca, altitudo 850 hexapedalis [1554.5 m], Humboldt & Bonpland 3985 (holotype, photography in JSTOR: P- 00215992!; Fig. 5 A ); (epitype, designated here; Fig. 7 ). Mexico • Morelos: Cuernavaca, Jardín etnobotánico Acapatzingo, calle Mariano Matamoros esquina con Degollado, col. Acapatzingo, 18°54'27.91"N, 99°13'29.95"W [18.9079155, -99.2243666], 1462 m, on Gliricidia sepium (Jacq.) Kunth ( Fabaceae ), 8 May 2023 (fl), M. I. Miguel V. 1300 (HUMO- 40028).

Description.

Shrub hemiparasitic, perennial, woody, scandent, monoecious-monocline. Haustorium with terete epicortical roots, emerging from the base of the plant, secondary haustoria. Stems terete, glabrous, glaucous when young, brown to brown-grayish with lenticels; green, voluble with nodes flat when young; with epicortical roots. Leaves opposite, subopposite or alternate, decussate, sessile to subpetiolate, petioles 1.0–6.0 mm long, resupinate; leaves shape variable on the same individual, ovate to widely lanceolate, obovate, oblong, elliptic or rarely rotund, 2.0–5.5 × 4.0–12.0 cm, apex obtuse to rounded, truncate to subemarginate with a small mucron, base attenuate, margin hyaline; glabrate, glaucous, crasso – coriaceous, pinnate venation, middle vein fading; leaves prehensile when young. Inflorescences racemes, 1 (2) per axil, indeterminate, 2.0– 6.2 cm long, peduncle 0.5–1.0 cm long, rachis subterete, glabrous, green; 6–8 (10) triads, opposite to subopposite, decussate, peduncle triad 0.6–2.0 mm long; bracts and bracteoles cymbiform, deciduous in anthesis. Flower buds cylindric to widely clavate with a rounded apex, 5.0– 6.2 mm long. Mature flowers bisexual, sessile, hexamerous, 2.2–3.5 × 6.0–8.0 mm; petals linear, reflexed in the middle part to 45 ° up to 90 °, 0.8–1.0 × 4.2–7.0 mm, white greenish to yellowish, petal apex rarely brown to reddish. Androecium with dimorphic stamens in two series, alternate, adnate to petals, filament free on middle part, papillate; first series with a filament 0.5–1.0 mm long, second series 0.3–0.6 mm long; symmetric anthers, dorsifixed, connective apiculate, anthers of the second series with a prominent connective; trichomes (villous) on the abaxial side of the anther up to 1.0 mm. Gynoecium with a convolute style, 3.2–5.0 mm long, 2 (3) longitudinal folds, stigma capitate, slightly oblique; ovary inferior, cylindric 1.4–1.8 × 1.5–2.0 mm; nectary or nectariferous ring with 6 protuberances, globose, around the style; calyculus green – yellowish, irregular to dentate margin. Fruit a single-seeded berry, ovoid to subglobose, 4.6–7.5 × 7.8–12.0 mm, granulated, rusty; pedicel accrescent on the fruit, granulated. Seeds ovoid, 4.0–6.0 × 6.5–10.0 mm (Figs 2 , 3 ).

Distribution, habitat, and hosts.

Struthanthus venetus is known from oak and pine-oak forests, tropical deciduous and subdeciduous forests, urban areas, and crop fields. It occurs in central Mexico, mainly in the states of Morelos, Ciudad de México, Estado de México, Guanajuato, Guerrero, and Puebla (Fig. 5 ), at elevations from 850 to 2,445 m. It parasitizes species of at least 26 families, including gymnosperms and angiosperms: Adoxaceae E. Mey. , Asteraceae Bercht. & J. Presl , Bignoniaceae Juss. , Burseraceae Kunth , Casuarinaceae R. Br. , Convolvulaceae Juss. , Cupressaceae Gray , Fabaceae Lindl. , Fagaceae Dumort. , Meliaceae Juss. , Moraceae Gaudich. , Myrtaceae Juss. , Oleaceae Hoffmanns. & Link , Opiliaceae Valeton , Petiveriaceae C. Agardh , Pinaceae Spreng. ex Rudolphi , Proteaceae Juss. , Punicaceae Bercht. & J. Presl , Rosaceae Juss. , Rubiaceae Juss , Rutaceae Juss , Salicaceae Mirb. , Tiliaceae Juss. , and Verbenaceae J. St. - Hil. Host records include other genera of parasitic plants such as Phoradendron ( Santalaceae ) and Schoepfia ( Schoepfiaceae ).

Phenology.

Flowering from April to November and with fruits from June to April.

Notes.

Older individuals have larger leaves near the base of the stem, leaf shape and size of variable size thorough the whole plant, and thick and corky petioles. Also, petals of some flower buds become reddish near the apex.

Additional specimens examined.

Mexico. Ciudad de México • Coyoacán, Universidad Nacional Autónoma de México (UNAM, between Institute of Biomedical Research and Sports Complex Buildings , 19.32437, -99.190957, 2229 m a. s. l., 22 Feb 2018 (fr), M. A. Caraballo 3383 ( US) • Cuauhtémoc, alameda central a 10 m de la avenida Hidalgo. Colonia Centro , 19°26'08.2"N, 99°08'42.65"W [19.435561, -99.14518], s. d., L. Agonizante N. s. n. ( UAMIZ) • ibid., San Antonio Abad y avenida del Taller, col. Tránsito , 19°24'50.61"N, 99°08'4.66"W, 2,250 m a. s. l., 23 Feb 1974 (fr), J. Gimate L. s. n. ( ENCB) • Iztapalapa, dentro del campus de la UAM-Iztapalapa, calle San Rafael Atlixco , 19°21'36.8"N, 99°04'17.8"W, 2,240 m a. s. l., 4 Aug 2022 (fl), R. Cerros T. s. n. ( HUMO) • Gustavo A. Madero, Sierravista 353, jardinera frente a tienda. En Lindavista , 19°29'55.25"N, 99°08'42.65"W [19.49868, -99.12861], 2,240 m a. s. l., 15 Oct 2023 (fl, fr), M. G. Maldonado B. 183 ( HUMO) . Estado de México • Ixtapan de la Sal , 18°50'31.49"N, 99°40'48.11"W, 1,876 m a. s. l., 15 May 2023 (fl), M. I. Miguel V. 1305 ( HUMO) • ibid., 18°50'53.45"N, 99°40'52.27"W, 1,913 m a. s. l., 15 May 2023 (fl), M. I. Miguel V. 1306 ( HUMO) • Temascaltepec, Chorrera [Carnicería], 19°02'40"N, 100°01'19.5"W, 1,230 m a. s. l., 8 Aug 1932 (fl), G. B. Hinton 1281 ( DES, GH, US) • Tejupilco, en el cerro de la Muñeca , 18°54'40"N, 100°08'20"W, 1,500 m a. s. l., 27–28 Feb 1954 (fr), E. Matuda 30519 ( MEXU) • Tepetlixpa, carretera Atlatlahucan-Tepetlixpa , 1 km antes de la desviación a Nepantla, 18°58'47.87"N, 98°51'10.81"W [18.979963, -98.853003], 1,964 m a. s. l., 2 Aug 2022 (fl), M. I. Miguel V. 1027 ( HUMO) • Tonatico, salida de Tonatico (N-S) , 18°48'22.68"N, 99°39'52.27"W, 1,668 m a. s. l., 15 May 2023 (fl), M. I. Miguel V. 1307 ( HUMO) . Guanajuato • León de los Aldama, blvd. Adolfo López Mateos, en barranca frente a Mobil 1, cerca del parque los Cárcamos , 21°09'49.32"N, 101°41'3.44"W, 1,829 m a. s. l., 5 Jul 2023 (fl), M. G. Maldonado B. 142 ( HUMO) • ibid., en parque Cárcamos, Av. Adolfo López Mateos, esquina con blvd. José María Morelos, en árboles frente al lago , 21°10'3.14"N, 101°41'3.88"W, 1,822 m a. s. l., 5 Jul 2023 (fl), M. G. Maldonado B. 143 ( HUMO) • ibid., en parque Cárcamos, av. Adolfo López Mateos esquina con blvd. José María Morelos, en árboles frente al lago , 21°10'2.89"N, 101°40'59.99"W, 1,823 m a. s. l., 5 Jul 2023 (fl), M. G. Maldonado B. 144 ( HUMO) . Guerrero • Chilpancingo de los Bravo, col. Juquila, en terreno baldío en la calle Cuauhtémoc, esquina con Miguel Hidalgo , 17°31'52.20"N, 99°30'40.82"W, 1,337 m a. s. l., 15 Jan 2023 (fr), M. G. Maldonado B. 83 ( HUMO) • ibid., 15 Jan 2023 (fl), M. G. Maldonado B. 84 ( HUMO) • ibid., 15 Jan 2023 (fl), M. G. Maldonado B. 85 ( HUMO) • ibid., 27 Feb 2023 (fl), M. G. Maldonado B. 86 ( HUMO) • Leonardo Bravo, Corral de Piedra, a lado del tecorral que delimita el patio trasero del sr. Hipólito Maldonado , 17°39'45.01"N, 99°56'36.35"W, 1,563 m a. s. l., 23 Apr 2023 (fl, fr), M. G. Maldonado B. 95 ( HUMO) • Pilcaya, el Mogote , 18°40'55.31"N, 99°33'57.27"W, 1,504 m a. s. l., 15 May 2023 (fl), M. I. Miguel V. 1303 ( HUMO) • ibid., loc. Piedras Negras, costado de la carretera , 18°43'23.59"N, 99°36'30.28"W, 1,557 m a. s. l., 15 May 2023 (fl), M. I. Miguel V. 1304 ( HUMO) • Taxco de Alarcón, Axixintla; km 194 carretera Taxco-Cuernavaca , 18°37'43.9"N, 99°30'39.9"W, 1,940 m a. s. l., 13 May 2021 (fl, fr), M. G. Maldonado B. 47 ( HUMO) • ibid., Palmillas; km 29 carretera Taxco-Cuernavaca , 18°30'52.6"N, 99°25'35.3"W, 1,940 m a. s. l., 13 May 2021 (fl, fr), M. G. Maldonado B. 48 ( HUMO) . Morelos • Amacuzac, km 18 de la carretera de cuota a Acapulco, a 2 km de Casahuatlán, 100 m a orilla de carretera , 18°33'57"N, 99°24'27"W, 987 m a. s. l., 3 Jul 2007 (fl, fr), L. G. Galván-González 123 ( MEXU, UAMIZ, IEB) • Atlatlahucan, carretera Cuautla-Amecameca, 10 m adelante de la desviación a Yecapixtla, a un costado de la carretera , 18°53'52.61"N, 98°54'29.13"W, 1,518 m a. s. l., 2 Aug 2022 (fl), M. I. Miguel V. 1026 ( HUMO) • ibid., carretera Atlatlahucan-Totolapan, en la esquina con la calle Galeana, a un costado de la carretera , 18°56'44.9"N, 98°53'52.3"W, 1,680 m a. sl., 2 Aug 2022 (fl), M. I. Miguel V. 1028 ( HUMO) • Coatlán del Río, rumbo al parque ecoturístico el Hoyanco, a orillas del canal de agua , 18°43'21"N, 99°25'51"W, 1,219 m a. s. l., 24 Feb 2013 (fr), L. G. Galván-González 212 ( HUMO) • Cuautla, 420 m antes de la empresa Campi, en dirección de sur a norte, a un costado de la carretera Izúcar de Matamoros – Cuautla , 18°50'32.78"N, 98°55'37.56"W, 1,367 m a. s. l., 30 May 2023 (fl), M. I. Miguel V. 1309 ( HUMO) • Cuernavaca, on shrubs, hillsides above Cuernavaca , 9 Nov 1895 (fl), C. G. Pringle 6185 ( MEXU; UC; HUH; US; P; VT; COLO) • ibid., near Cuernavaca , 2 Jun 1939 (fl), O. Nagel 8026 ( GH, MEXU) • ibid., about 4.5 mi E of Ocotepec on road from Cuernavaca to Tepoztlán , [18°58'39.85"N, 99°09'39.85"W, 1,643 m a. s. l.], 4 Aug 1971 (fl), W. D. Stevens 1385 ( ENCB) • ibid., Colonia del Bosque , 18°54'49.4"N, 99°15'17.1"W, 1,510 m a. s. l., 31 May 2014 (fr), N. R. Rueda 2 ( HUMO) • ibid., en barranca de la col. la Unión , 18°54'49.4"N, 99°15'17.1"W, 1,490 m a. s. l., 31 May 2014 (fl), L. G. Galván-González 221 ( HUMO) • ibid., Facultad de Ciencias del Deporte, campus Chamilpa de la UAEM , 18°59'7.03"N, 99°14'18.46"W, 1,932 m a. s. l., 21 Nov 2016 (fl, fr), L. G. Galván-González 367 ( HUMO) • ibid., la Carpa brecha a la barranca del Túnel , 18°57'2.99"N, 99°14'29.92"W, 1,908 m a. s. l., 5 Jul 2021 (fl), M. I. Miguel V. 964 ( HUMO) • ibid., jardín botánico de la UAEM , 18°59'11.4"N, 99°17'15.3"W, 1,906 m a. s. l., 18 May 2022 (fl, fr), M. G. Maldonado B. 60 ( HUMO) • ibid., jardín etnobotánico Acapatzingo, calle Mariano Matamoros esquina con Degollado , 18°54'27.91"N, 99°13'29.951"W, 1,462 m a. s. l., 8 May 2023 (fl), M. I. Miguel V. 1300 ( HUMO) • Emiliano Zapata, Tetecalita, entrando por vv. Las Granjas , 18°46'26.7"N, 99°10'0.2"W, 1,194 m a. s. l., 18 Dec 2014 (fr), Y. Montoya M. 369 ( HUMO) • Jantetelco, faldas del cerro del Chumil , 18°42'42"N, 98°45'16"W, 1,428 m a. s. l., 1 Sep 2006 (fl, fr), L. G. Galván-González 15 ( HUMO) • ibid., Chalcatzingo zona arqueológica , 18°40'40.38"N, 98°46'14.18"W, 1,365 m a. s. l., 9 May 2023 (fl), M. I. Miguel V. 1301 ( HUMO) • ibid., desviación junto al puente Jantetelco, en la carretera Puebla-Jantetelco, frente al parque , 18°42'58.54"N, 98°46'1.1"W, 1,435 m a. s. l., 19 Jun 2023 (fl), M. G. Maldonado B. 123 ( HUMO) • Jiutepec, parque estatal el Texcal, 250 m al noreste de la entrada principal, cerca del borde de la reserva, a un costado de una brecha , 18°53'46.79"N, 99°08'26.12"W, 1,408 m a. s. l., 31 May 2023 (fl), M. I. Miguel V. 1324 ( HUMO) • Jonacatepec, 20 m antes de la planta tratadora de agua, a un costado de la carretera Tepalcingo-Jonacatepec , 18°39'41.09"N, 98°48'37.88"W, 1,295 m a. s. l., 30 May 2023 (fl), M. I. Miguel V. 1308 ( HUMO) • Miacatlán, Xochicalco, 1.85 km al S de la zona arqueológica , 18°47'35.4"N, 99°17'48.53"W, 1,198 m a. s. l., 10 May 2023 (fl), M. I. Miguel V. 1302 ( HUMO) • Puente de Ixtla, Tilzapotla. El Espinazo del Diablo, 1.5 km al este de Tilzapotla, brecha de terracería mina la Parreña, entronque con la Piaña-carretera el Salto , [18°29'31.66"N, 99°14'25.92"W, 1,410 m a. s. l.], 30 Jun 1998 (fl), J. C. Juárez 993 ( HUMO) • ibid., carretera Tilzapotla-Caxintla, 300 m pasando la cantera, 1.5 km antes de la desviación hacia el Salto, 18°28'51.7"N, 99°15'50"W, 1,037 m a. s. l., 9 Feb 2023 (fr), M. I. Miguel V. 1251 ( HUMO) • Temixco, barranca los Sabinos , 18°48'35"N, 99°15'58"W, 1,215 m a. s. l., 10 Nov 2006 (fl buds), R. Cerros T. 2725 ( UAMIZ) • Tepoztlán, carretera Tepoztlán-Oacalco , 18°58'10"N, 99°04'25"W, 1,560 m a. s. l., 28 Sep 2006 (fr), R. Cerros 2676 ( CIIDIR, MEXU, UAMIZ) • ibid., Cerro de la Cruz, cerca de San Andrés de la Cal. [18°57'35.73"N, 99°6'59.76"W, 1,200 m a. s. l.], 4 Apr 2009 (fl), M. Cházaro B. 9401 ( XAL) • ibid., alrededor del poblado de San Andrés de la Cal, 18°57'09"N, 99°06'36.1"W, 1,783 m a. s. l., 7 Jun 2020 (fl), R. Hernández C. 2439 ( HUMO) • Tlaltizapán, balneario Sta. Isabel, área de acampado , 18°43'58.44"N, 99°06'51.22"W, 954 m a. s. l., 15 Jun 2023 (fl), M. I. Miguel V. 1346 ( HUMO) • Yautepec, huerta de una casa particular (la familia Chávez) a ca. 1 km al NE de Yautepec [Tabachines] , 18°53'55.6"N, 99°02'16.9"W, 1,231 m a. s. l., 4 Apr 1986 (fr), D. H. Lorence 5033 ( RSA, US) • ibid., carretera Tlayacapan-Oaxtepec, 400 m adelante de la desviación a Atlatlahucan , 18°55'39.15"N, 98°57'59.59"W, 1,481 m a. s. l., 2 Aug 2022 (fl remains), M. I. Miguel V. 1029 ( HUMO) • ibid., 200 m adelante de la excaseta de Oacalco, autopista Oaxtepec-Tepoztlán , 18°55'59.23"N, 99°01'39.22"W, 1,367 m a. s. l., 30 May 2023 (fl), M. I. Miguel V. 1310 ( HUMO) • Yecapixtla, Yecapixtla , [18°52'9.13"N, 98°49'47.98"W], 1,700 m a. s. l., 10 Oct 2014 (fl), L. Ortega C. 148 ( HUMO) • Zacualpan de Amilpas, Campos de cultivo de Tlacotepec , 18°48'46"N, 98°44'48"W, 1,770 m a. s. l., 22 Sep 2006 (fr), L. G. Galván-González 44 ( UAMIZ) . Puebla • Atlixco, camino Puebla-Atlixco, 200 m después de la caseta de cobro Siglo XXI , 18°56'09.01"N, 98°26'58.31"W, 1,927 m a. s. l., 19 Jun 2021 (fl, fr), M. G. Maldonado B. 122 ( HUMO) • Puebla, jardín botánico de la BUAP , 18°59'57.51"N, 98°11'49.65"W, 2,150 m a. s. l., 12 Dec 2017 (fr), A. J. Coombes 1808 ( HUAP) • Puebla, camellón frente al jardín botánico de la BUAP , 18°59'57.6"N, 98°11'53.15"W, 2,132 m a. s. l., 30 Sep 2022 (fl, fr), M. I. Miguel V. 1032 ( HUMO) • ibid., camellones de la BUAP , 18°59'56"N, 98°11'50.06"W, 2,134 m a. s. l., 9 Jun 2023 (fl), M. I. Miguel V. 1345 b ( HUMO) • Tepexco, al N de loc. de Ixtlala , 18°35'37.58"N, 98°42'8.3"W, 1,151 m a. s. l., 24 Aug 2016 (fr), L. Caamaño O. 9052 ( HUAP, HUMO) • 1.5 km al N del balneario Ixtatlala, sobre la brecha al poblado de Tepexco , 18°36'16.2"N, 98°42'20.2"W, 1,154 m a. s. l., 28 Aug 2022 (fl), M. I. Miguel V. 1030 ( HUMO) • ibid., 28 Aug 2022 (fl, fr), M. I. Miguel V. 1031 ( HUMO) .

Figures

Figure 1. Flower morphology of Struthanthus venetus (Loranthaceae) A lateral view of flower at early anthesis B upper view of flower at full anthesis showing ascendant petals, the pistil with stigma in the center, and functional stamens with tufts of trichomes (t) behind the anthers C lateral view of flower at full anthesis with a petal removed to show the contour of the convolute style (black dashed line) D lateral view of the convolute style with brownish stigma E long (S 1) and short (S 2) series of stamens next to the whole pistil (right side) F hexagonal nectary (ne) at the base of the style (central circular scar).

Figure 2. Comparative reproductive morphology between Struthanthus venetus and S. interruptus (Loranthaceae). S. venetus: A dissected flower at early anthesis. Note that all stamens are well-developed and arranged in two alternating series (S 1 and S 2). Pistil showing the convoluted style at right B dissected flower during late anthesis C inflorescence with flowers in early and late anthesis. S. interruptus: D dissected pistillate flower showing vestigial, non-functional staminodes and pistil with convoluted style E dissected petals of a staminate flower showing two series of alternating stamens with pollen grains visible and an undifferentiated, wavy pistillode F pistillate inflorescence showing some flowers without petals G staminate inflorescence with flowers at full anthesis exhibiting bright white anthers. Black arrows in pistils are pointing to the first convolution in styles.

Figure 3. Leaves and fruits of Struthanthus venetus and S. interruptus (Loranthaceae). S. venetus: A leaves B infructescence with mature and unmatured fruits. S. interruptus: C leaves D infructescence, fruit reddish, glaucous.

Figure 5. Types of Struthanthus venetus, S. volubilis, and S. interruptus (Loranthaceae) A holotype of Loranthus venetus (≡ Struthanthus venetus), Humboldt & Bonpland 3985 (P- 00215992!) B holotype of S. interruptus, Humboldt & Bonpland s. n. (P- 00215992!) C lectotype of L. volubilis (≡ S. volubilis), Sessé 924 (MA- 600707!).

Figure 7. Epitype of Loranthus venetus (≡ Struthanthus venetus), M. I. Miguel V. 1300 (HUMO- 40028!); collected in Cuernavaca, Morelos at the type locality.