118urn:lsid:arphahub.com:pub:71cc5dc6-a767-5334-951f-ef6ae8936459Plant Ecology and Evolutionplecevo2032-39132032-3921Meise Botanic Garden and Royal Botanical Society of Belgium10.5091/plecevo.145707145707Research ArticleAngiospermaeBiodiversity & ConservationCatalogues and ChecklistsFloristics & DistributionIdentification keyMorphology & AnatomyPhylogenySystematicsTaxonomyAmericasPacificA new and endemic species of Struthanthus (Loranthaceae) from Guerrero, MexicoMaldonado-BorjaMaría Guadalupehttps://orcid.org/0000-0002-9515-69691Cerros-TlatilpaRosatlatilpa@uaem.mxhttps://orcid.org/0000-0002-7079-62302Maestría en Manejo de Recursos Naturales, Centro de Investigaciones Biológicas, Universidad Autónoma del Estado de Morelos, Cuernavaca, MexicoMaestría en Manejo de Recursos Naturales, Centro de Investigaciones Biológicas, Universidad Autónoma del Estado de MorelosCuernavacaMexicoFacultad de Ciencias Biológicas, Universidad Autónoma del Estado de Morelos, Cuernavaca, MexicoUniversidad Autónoma del Estado de MorelosCuernavacaMexico
Corresponding author: Rosa Cerros-Tlatilpa (tlatilpa@uaem.mx)
Academic editor: Luiza Teixeira-Costa
2025220520251582195204CEB88297-F9C8-57BB-BCE7-7212AF48C75C155017233112202424032025María Guadalupe Maldonado-Borja, Rosa Cerros-TlatilpaThis is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Background and aims – Struthanthus is a neotropical genus with 60 to 70 species, distributed from northern Mexico to Argentina. Eighteen species are reported in Mexico. During fieldwork to investigate Struthanthus in Mexico, a new species was collected in the state of Guerrero. We present a full description, distribution map, illustrations, and photographs of an unusual new Struthanthus species endemic to Guerrero, Mexico.
Material and methods – This study is based on fieldwork, literature revision, and examination of herbarium material. Collected specimens were prepared for storage in the herbarium, analysed, measured, described, and photographed. Preliminary conservation assessment is based on spatial analyses following IUCN guidelines and criteria.
Key results – We propose a new species of Struthanthus for Guerrero, Mexico, S.longipetiolatus. This species is only known from cloud forests, oak-pine forests, and oak forests in the province of Sierra Madre del Sur, in the state of Guerrero. A distribution map and an identification key are provided for S.longipetiolatus and its morphologically similar congeners in the region.
Conclusion – The newly described species increases the number of Struthanthus species in Mexico to 19 and the number of endemic species to nine. This discovery underlines the need for continued botanical inventories and research on parasitic plants.
endemismhemiparasitemistletoetaxonomyIntroduction
Struthanthus Mart. is a complex genus of Loranthaceae because it shares morphological characters with other genera of small flowers, such as Cladocolea Tiegh. (Kuijt 1987, 1991b), Panamanthus Kuijt (Kuijt 1991a), Passovia H.Karst. (Kuijt 2011; Caires et al. 2021), Peristethium Tiegh. (Kuijt 2012; Caires et al. 2014; Caires and Azevedo 2015), Phthirusa Mart. (Kuijt 2009), and Pusillanthus Kuijt (Caires et al. 2012). Struthanthus is closely related to Cladocolea and Peristethium, genera recognized as polyphyletic (Kuijt 1975, 1981, 2012; Kuijt and Hansen 2015; Galván-González et al. 2024). Struthanthus is a neotropical genus distributed from northern Mexico to Argentina, comprising 60–70 species (Caires and Dettke 2020). About 18 species of Struthanthus have been reported from Mexico (Galván-González et al. 2024; Maldonado-Borja et al. 2024). The exact number of species within Struthanthus remains uncertain due to the lack of a comprehensive taxonomic treatment (Kuijt 1964, 2003b, 2012, 2016; Dettke and Waechter 2012; Caires and Azevedo 2015; Robles et al. 2016; Maldonado-Borja et al 2023). According to Martínez-Ambriz et al. (2017), four species of Struthanthus are distributed in Guerrero: S.crassipes (Oliv.) Eichler, S.interruptus (Kunth) G.Don, S.quercicola (Schltdl. & Cham.) G.Don, and S.ramiro-cruzii Martínez-Ambr. & Sor.-Benítez. Recently, Cladocolearacemosa Kuijt was transferred to Struthanthus as S.racemosus (Kuijt) Galv.-González (Galván-González et al. 2024). Here, we describe a new species of Struthanthus from Guerrero, Mexico that shares morphological affinities with S.ibe-dzi Mald.-Borja & Cerros, S.racemosus, and S.ramiro-cruzii.
Material and methods
The description is based on our collections from Sierra Madre del Sur (SMS) in Guerrero and herbarium specimens from ENCB, HUMO, MEXU, and XAL (acronyms follow Thiers 2024). Specimens were collected, pressed, and dried, with three to five duplicates. Vouchers were deposited in HUMO and duplicates in HUAP, MEXU, and UAMIZ. Vegetative and reproductive structures were carefully studied under a stereoscopic microscope. Measurements and photographs of the floral structures were taken using fresh or rehydrated material. Morphological descriptions were based on Kuijt’s terminology (Kuijt 1987, 2003a, 2003b). The map was generated with QGIS v.3.16 (QGIS Development Team 2020) using data from our fieldwork and herbarium labels. The conservation status assessment of the new species follows the IUCN Red List categories and criteria (IUCN 2022). The extent of occurrence (EOO) and area of occupancy (AOO), using 2 × 2 km grid cells (4 km2), were estimated using the Geospatial Conservation Assessment Tool (GeoCAT; Bachman et al. 2011).
Holotype of Struthanthuslongipetiolatus (HUMO 40027).
https://binary.pensoft.net/fig/1330691
Morphological comparison of Struthanthuslongipetiolatus with S.ibe-dzi, S.racemosus, and S.ramiro-cruzii.
Characters
S.ibe-dzi
S.longipetiolatus
S.racemosus
S.ramiro-cruzii
Stem nodes
compressed and bicarinate
subterete to complanate
terete
terete
Leaf shape
ovate to lanceolate, rare elliptical
lanceolate, ovate, or narrowly ovate
narrowly lanceolate to subulate-falcate
ovate to lanceolate, cordate when mature
Leaf apex shape
acute to acuminate
long acuminate to acute mucronate
apiculate
apiculate or acute
Leaf base shape
cuneate to oblique
attenuate to oblique
attenuate to cuneate
subcordate to truncate
Petiole length (cm)
0.25–1.2
1.2–3.2
0.6–0.9
0.5–1
Inflorescences per axil
1
1
1
1(2)
Inflorescence subunit
mostly triads, rarely monads in the apical flowers of inflorescence
triads
monads
triads, rarely monads or dyads in the apical flowers of the inflorescence
Flowers in triads (monads if applicable)
central sessile and laterals pedicellate
central sessile and laterals pedicellate
monads pedicellate
central sessile and laterals pedicellate
Pistillate inflorescence length (cm)
2–5
3.5–7.6
3–4.5
2.5–6.2(–10.5)
Triads/monads number per pistillate inflorescence
6–12(–15) triads
10–14(–16) triads
8–10(–12) monads
8–20 triads
Pistillate flower length from base of ovary (mm)
5.8–7.2
4.7–6
3.8–5
5–5.8
Staminate inflorescence length (cm)
2–6.8
3.6–10.8(–12)
3.6–4.6
2.5–8
Triads/monads number per staminate inflorescence
6–16(–19)
12–16(–18)
10–12 monads
10–16
Staminate flower length from base of ovary (mm)
6–9
6.2–10.2
4.6–6
6–7
Flower colour
green
olive green yellowish to pink-reddish
reddish
greenish-yellow
Diagnosis
Struthanthuslongipetiolatus is similar to S.ibe-dzi, S.racemosus, and S.ramiro-cruzii. Plants scandent and pendant with inflorescences in racemes and triads peduncled, the central flower sessile, and the lateral ones pedicellate as in S.ibe-dzi and S.ramiro-cruzii. However, the new taxon is distinguished by its olive green yellowish to pink-reddish stems, petioles, leaves, inflorescence, petals, and style of the pistillate flower and by the long petioles reaching up to 3.2 cm.
Struthanthuslongipetiolatus. A. Habit, scandent and pendant shrub. B. Staminate inflorescence. C. Lateral view of a staminate flower with two petals removed to show the anthers. C1. Front and side view of anther basifixed, dimorphic, and elliptical with an apicular connective. C2. Dissected staminate flower with two alternating stamens, stylodium straight to slightly wavy, and undifferentiated stigma. D. Lateral view of a pistillate flower with two petals removed to show the contour of the convolute style. D1. Dissected pistillate flower with staminodes, a convolute style, and a capitate stigma. E. Mature leaf. F. Infructescence. Male inflorescence from Maldonado-Borja 87 (A, B, C, C1, C2); female inflorescence from Maldonado-Borja 119 (D, E) and Maldonado-Borja 54 (F). Illustration by Eduardo Santaella.
https://binary.pensoft.net/fig/1330692Description
Shrubs woody, scandent, pendant, 0.8–4(–6.5) m long, perennial, hemiparasitic, dioecious. Haustorium terete, with several epicortical roots at the base of the plant; epicortical roots produce secondary haustoria that attach to the host. Stems 1–4.5 mm diameter, voluble, terete to subterete, glabrous, olive green to pinkish, and brown greenish when dried, with lenticels when mature; with epicortical roots. Nodes subterete to complanate, bicarinate mainly when young; stem internodes 3.5–8.6(–10) cm long. Leaves opposite to subopposite; petioles 1.2–3.2 cm long, channelled near the leaf blade base, resupinate; blades lanceolate, ovate, or narrowly ovate, 1.2–5.0 × 6.5–16.5 cm, apex long acuminate to acute mucronate, base attenuate to oblique, olive green to pinkish-reddish, margin entire, repand when mature, hyaline, venation pinnate, glabrous, papyraceous. Inflorescences indeterminate, axillary, 1 per axil, racemes of triads, rarely paniculated; rachis subterete to applanate, nodes plane, triads opposite to subopposite, decussate; central flower from triad sessile, lateral flowers pedicellate 0.22–0.65 mm long. Bracts and bracteoles caducous, cupuliform. Pistillate inflorescences 3.5–7.6 cm long, peduncles 0.5–1.35 cm long, 10–14(–16) triads, triad peduncle 0.5–1.28 mm long. Staminate inflorescences 3.6–10.8(–12) cm long, peduncle 0.45–1.6(–2) cm long, 12–16(–18) trads, triad peduncle 0.6–1 mm long. Pistillate flowers hexamerous. Flower buds cylindrical, rounded at the apex; mature flowers 1.25–2.2 × 4.7–6 mm, calyculus irregular, 0.1–0.2 mm, petals linear 0.5–0.75 × 2.8–3.65 mm, olive green yellowish to pink-reddish, staminodes one series; nectary globose, hexagonal, surrounding the style; ovary inferior 1–1.2 × 2–2.6 mm, green yellowish; style strongly convolute, 3.2–4 mm long, stigma capitate, pink-reddish when ripe. Staminate flowers hexamerous, central flower of triad sessile, pedicels of lateral flowers 1.2–2.2 mm long. Flower buds claviform with rounded apex; mature flowers 2.4–4.8 × 6.2–10.2 mm, petals linear, 0.8–1.25 × 5–8.5 mm, olive green yellowish to pink-reddish, without trichomes at the insertion of the petal and the filament; anthers basifixed, dimorphic, and elliptical, 0.9–1.18 × 2.2–3.2 mm, fully attached to petals, asymmetrical theca, apicular connective; calyculus irregular, green yellowish 0.2–0.5 mm, vestigial ovary 1.2–2.25 × 1–2 mm, nectary globose, hexagonal, surrounding the stylodium base; stylodium straight to slightly wavy, 1.4–3 mm long, stigma undifferentiated. Fruit a berry, ovoid, green when immature, orange to vermillion when ripe, bluish-black when dry, glaucous, 3.45–6.65 × 8.2–10 mm. Seed ovoid, 2.2–4.8 × 4.2–5.2 mm.
Struthanthuslongipetiolatus. A. Pistillate inflorescence with reddish styles. B. Dissected pistillate flower with staminodes (st), a convolute style, and a capitate stigma (s) above the ovary (o). C. Hexamerous nectary (ne), irregular calyculus (ca). D. Staminate inflorescence with pendant petioles (p), pink-reddish leaves. E. Dissected staminate flower showing two series of stamens (S1, S2), basifixed, dimorphic, with elliptical anthers and apicular connective; stylodium slightly wavy, and undifferentiated stigma. F. Hexamerous nectary (ne), irregular calyculus (ca). G. Sexual dimorphism, female (left) and male (right) flowers, two petals were removed. H. Immature fruits. I. Mature orange and vermillion fruits. Photos by Rosa Cerros-Tlatilpa (A, D, H, I) and Maria Guadalupe Maldonado-Borja (B, C, E, F, G).
https://binary.pensoft.net/fig/1330693Distribution and habitat
Struthanthuslongipetiolatus is endemic to Guerrero, Mexico, in cloud forests, oak-pine forests, and oak forests in the Sierra Madre del Sur Biogeographic Province (Morrone et al. 2017), in the municipalities Chilpancingo de los Bravo, General Heliodoro Castillo, and Leonardo Bravo (Fig. 4). It is found at elevations between 2,332 and 2,577 m a.s.l.
Distribution of Struthanthuslongipetiolatus and congeners.
https://binary.pensoft.net/fig/1330694Hosts
Struthanthuslongipetiolatus mainly parasitizes Pinus spp. (Pinaceae), but also Ostryavirginiana (Mill.) K.Koch (Betulaceae), and Quercus spp. (Fagaceae). It was also found parasitizing cultivated fruit trees such as Crataegusmexicana Moc. & Sessé ex DC., Prunuspersica (L.) Batsch (Rosaceae), and Psidiumguajava L. (Myrtaceae) (Fig. 5).
Habit of Struthanthuslongipetiolatus. A. Pendant plants in the type locality. B. Mistletoe on Pinus spp. C. Haustorium and epicortical roots with red lenticels (l). Photos by Maria Guadalupe Maldonado-Borja (A) and Rosa Cerros-Tlatilpa (B, C).
https://binary.pensoft.net/fig/1330695Phenology
Flowering from May to August and fruiting from December to February.
Etymology
The specific epithet refers to the characteristic long petioles in this taxon, unique among Mexican species.
Preliminary IUCN conservation assessment
Endangered: EN B1ab(iii) + 2ab(iii). Struthanthuslongipetiolatus is known only from the centre region of Guerrero in the Province of Sierra Madre del Sur. The extent of occurrence (EOO) is estimated at 293 km2 (criterion B1: EN) and the area of occupancy (AOO) is estimated at 52 km2 (criterion B2: EN). There are four locations (condition a) and there is a continuing decline in habitat quality (condition b(iii)), together indicating Endangered under criteria B1 and B2. The state of Guerrero experiences an annual deforestation rate averaging 13,311.8 hectares/year (CONAFOR 2020). Additionally, in 2022 alone, forest fires impacted 108,597 hectares of forests (ISNIF 2022). Likewise, the main hosts of S.longipetiolatus are pine trees, which are immoderately cut down. It is estimated that 98% of the timber production in Guerrero is from Pinus spp. (González et al. 2018). Press and Phoenix (2005) suggest that hosts are essential to keep parasitic plants (pp) in a location; therefore, local extinction of a host can cause the pp population to decline. Therefore, following the guidelines of the IUCN criteria (IUCN 2022), S.longipetiolatus should be classified as Endangered: EN B1ab(iii) + 2ab(iii).
Additional material examined
MEXICO – Guerrero • Chilpancingo de los Bravos, Llanos de Tepoxtepec; 17°28’36.13”N, 99°31’36.35”W; 2331 m; 12 Jan. 2022; fr.; Maldonado-Borja 49; HUMO • ibid.; 12 Jan. 2022; fr.; Maldonado-Borja 50; HUMO • ibid.; 12 Jan. 2022; fr.; Maldonado-Borja 51; HUMO • ibid.; 18 Apr. 2022; fr.; Maldonado-Borja 54; HUMO • ibid.; 18 Apr. 2022; ♂ fl.; Maldonado-Borja 55; HUMO • ibid.; 13 May 2022; ♀ fl.; Maldonado-Borja 71; HUMO • ibid.; 26 Aug. 2023; ♂ fl.; Maldonado-Borja 80; HUMO • Km 7 hacia llanos de Tepoxtepec; 17°28’44.11”N, 99°31’9.44”W; 2218 m; 18 Apr. 2022; ♀ fl.; Maldonado-Borja 53; HUMO • Llanos de Tepoxtepec; 17°28’42.99”N, 99°31’31.51”W; 2269 m; 18 Apr. 2022; ♂ fl.; Maldonado-Borja 56; HUMO • Camino hacia el parque de Llanos de Tepoxtepec; 17°27’48.3”N, 99°32’49.6”W; 2577 m; 13 May 2022; ♀ fl.; Maldonado-Borja 68; HUMO • Camino hacia el parque de Llanos de Tepoxtepec; 17°28’33.8”N, 99°31’50.4”W; 2399 m; 13 May 2022; ♂ fl.; Maldonado-Borja 69; HUMO • ibid.; 13 May 2022; ♂ fl.; Maldonado-Borja 70; HUMO • ibid.; 26 Aug. 2022; ♀ fl.; Maldonado-Borja 78; HUMO • Camino hacia el parque de Llanos de Tepoxtepec; 17°28’32.79”N, 99°31’48.59”W; 2376 m; 26 Aug. 2022; ♀ fl.; Maldonado-Borja 79; HUMO • Llanos de Tepoxtepec; en bifurcación camino al Parque, a lado de Huerta de duraznos; 17°28’37.07”N, 99°31’26.32”W; 2383 m; 17 Jun. 2023; ♀ fl.; Maldonado-Borja 117; HUMO • ibid.; 17 Jun. 2023; ♂ fl.; Maldonado-Borja 118; HUMO • ibid.; 17 Jun. 2023; ♀ fl., fr.; Maldonado-Borja 119; HUMO • Llanos de Tepoxtepec, km 8 a 200 m de la telesecundaria; 17°28’33.77”N, 99°31’50.29”W; 2265 m; 26 Aug. 2022; ♂ fl.; Maldonado-Borja 120; HUMO • ibid.; 26 Aug. 2022; ♀ fl.; Maldonado-Borja 121; HUMO • General Heliodoro Castillo, Carretera de Puerto del Varal a Verde Rico; 17°42’32.75”N, 99°54’44.44”W; 2222 m; 24 Apr. 2023; ♂ fl.; Maldonado-Borja 96; HUMO • Leonardo Bravo, Filo de Caballos, Chichihualco; [17.64897°N, -99.82453°W]; 2240 m; 3 Jun. 1983; ♂ fl.; Martínez S. 3895; MEXU, ENCB • ½ km al E de Tres Caminos, Chichihualco; [17.71117°N, -99.77511°W]; 2420 m; 4 May 1987; ♀ fl.; Lorea 4083; XAL • Comunidad “Campo de Aviación”; 17°39’9.51”N, 99°49’24.89”W; 2200 m; 22 Apr. 2023; ♂ fl.; Maldonado-Borja 88; HUMO.
Notes
A single individual can parasitize different tree strata, forming the main haustorium on the top branches and descending to the lower branches, measuring up to 6.5 m in length. This new species is characterized by its long petioles up to 3.2 cm. It can also have olive green yellowish to pink-reddish tones in stems, leaves, flower peduncles, petals, and even in the styles. Unlike other species of the genus, S.longipetiolatus has a well-marked sexual dimorphism, the staminate flowers being larger compared to the pistillate flowers (Fig. 3G). Struthanthuslongipetiolatus exhibits autoparasitism on its stems and leaves.
Key to the species of <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Struthanthus">Struthanthus</tp:taxon-name-part></tp:taxon-name></italic> of Guerrero, Mexico
1.
Stems with exfoliating bark; condensed inflorescence
S.condensatus
–
Stems without exfoliating bark; non-condensed inflorescence
2
2.
Inflorescence spike-like, 1–5 per axil; pedicel on the fruit conspicuously accrescent, pendant
S.quercicola
–
Inflorescence racemiform,1–2 per axil; pedicel on the fruit slightly thickened, straight
3
3.
Triads subsessile; triad flowers all sessile
4
–
Triads pedunculate; lateral flowers pedicellate and central flower sessile
5
4.
Leaves with petioles 0.8–1.2 cm; unisexual flowers; non-accrescent pedicels on the fruit; fruit without glands, reddish
S.interruptus
–
Leaves sessile to subsessile, petioles 0.4–0.6 cm; bisexual flowers; accrescent pedicels on the fruit; fruit with glands, brown-reddish
S.venetus
5.
Leaves ovate to lanceolate, cordate when mature, apex apiculate or acute, base subcordate to truncate
S.ramiro-cruzii
–
Leaves lanceolate, ovate or narrowly ovate, apex acute to long acuminate to apiculate, base acute to attenuate
6
6.
Petiole 0.6–0.9 cm long, subunit of inflorescence in monads
S.racemosus
–
Petiole 1.25‒3.2 cm long, subunit of inflorescence in triads
S.longipetiolatus
Discussion
Struthanthuslongipetiolatus morphologically resembles S.ibe-dzi, S.racemosus, and S.ramiro-cruzii because the four species have inflorescences in racemes. Additionally, unlike other Struthanthus species, they have stamens fully attached to the petal and lack trichomes at the base of the petal’s insertion with the filament. The four species are distributed in the Sierra Madre del Sur, with S.ibe-dzi being endemic to the state of Oaxaca. In contrast, S.longipetiolatus, S.racemosus, and S.ramiro-cruzii are found in the state of Guerrero. Like S.ramiro-cruzii and S.ibe-dzi, S.longipetiolatus has triads with pedicellate lateral flowers and a sessile central one. Struthanthusracemosus differs from S.longipetiolatus in having monads instead of triads in addition to petioles 0.60–0.90 mm long. Additionally, S.longipetiolatus and S.ramiro-cruzii are found in the same locality, but they differ mainly in the leaf shape and pedicel length. Moreover, S.ramiro-cruzii has leaves ovate to lanceolate, cordate when mature, with a petiole 0.5–1.0 cm long while S.longipetiolatus has leaves lanceolate, rarely ovate with apex acute to long acuminate, mucronate, and a base acute to obtuse with a slender petiole up to 3.20 cm long. Another notable difference is the stem colour, which ranges from olive green to pink-reddish, and extends to leaves, flowers peduncles, petals, and even the styles. Plant pigments are involved in various functions including photosynthesis, for example, flowers from calyx to pistil may accumulate pigments implicated in pollination (Miller et al. 2011). According to Heide-Jørgensen (2008), the red colour is due to anthocyanins in the vacuoles of the cells. In S.longipetiolatus, the change of colour from olive green to pink-reddish in the floral parts, mainly the styles, could be related to the fertilization of the flower. According to Miller et al. (2011), floral pigments are modified during flower development, for example, at emergence and after pollination. This change could direct pollinators to unpollinated flowers. Struthanthuslongipetiolatus has petioles arranged in a pendant manner, unlike other species of Struthanthus in Mexico, which have ascending petioles.
Guerrero ranks as the 4th state in Mexico in terms of biological diversity (Botello et al. 2015) and the 5th in plant diversity, with 237 endemic species (Villaseñor 2016). Additionally, 5.4% of its area is designated as Federal Protected Natural Areas (ANPs; DOF 2023; CONANP 2024). The loss of natural vegetation is 2.46% per year (SEMARNAT 2015). Each year, 0.5–0.7% of coniferous forests and 2.4–2.7% of tropical forests are lost. In addition, forest fragmentation in the country is estimated between 22 and 24%, with overgrazing at an annual rate of 23.7–36.3% (SEMARNAT 2015). This makes S.longipetiolatus a vulnerable species due to habitat quality decline. Despite the efforts by the Facultad de Ciencias at UNAM to document the Flora of Guerrero (Diego-Pérez and Fonseca 1994–2024), the state has historically faced social challenges such as poverty, natural disasters, violence (including drug trafficking and forced displacements). These issues have significantly hindered the exploration and knowledge of its biological diversity. Thus, it is crucial to understand the challenges the state faces and recognize the importance of protecting and describing the flora and fauna of Guerrero.
Acknowledgments
We are grateful to Emmanuel Martínez-Ambriz, an anonymous reviewer, the subject editor Luiza Teixeira-Costa, and the editor in chief Brecht Verstraete for their comments and suggestions to improve this manuscript. This work is part of the MSc thesis of the first author and is financially supported by the National Council of Science and Technology (CONAHCYT) through grant 286670. We thank the curators from the herbaria for allowing access to their collections, particularly to ENCB, HUMO, MEXU, UAGC, and XAL for specimen loans. Special thanks to the Secretaría de Medio Ambiente y Recursos Naturales for granting a collecting permit (SGPA/DGGFS/712/1132/1809/N1-0081/04/18). A sincere and deep gratitude to the brothers Germán†, Hipólito, and Jerónimo Maldonado Marino and their respective families, for their support and company during the fieldwork. Also, our gratitude to the family Solano Moreno from Llanos de Tepoxtepec, especially to the fearless young Santiago. We also thank Dr J.C. Caspeta-Mandujano for his help during fieldwork, Eduardo Santaella for the illustrations, and Elizabeth Skendzic for the final review of the manuscript.
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