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30 December 2023 Two New Species of Aphyllon from Northeastern Mexico
L. Turner Collins, Carlos Velazco, Adam C. Schneider
Author Affiliations +
Abstract

Plants originally identified as Aphyllon ludovicianum that occur near Monterrey, Nuevo Leon, and Cuatro Ciénegas Bolson, Coahuila, Mexico, were found to not align with the protologue of that species, the close relative A. multiflorum, or any other species of Aphyllon. Following a detailed study of floral morphology, geographic range, host species, and phylogenetic position using dry herbarium specimens, field study, and georeferenced color photographs, we propose the new binomials Aphyllon spectabile for the plants from Nuevo Leon and Aphyllon gypsophilum for the plants from Coahuila, Mexico. These additions increase the taxonomic diversity of Aphyllon to 27 species plus ten additional subspecies. Gymnosperma glutinosum and two species of Xanthisma were reported for the first time as a host species for the genus Aphyllon. We also provide an updated key to Aphyllon in Mexico.

Resumen—Las plantas identificadas como Aphyllon ludovicianum y que ocurren cerca de Monterrey, Nuevo León y Cuatro Ciénegas Bolsón, Coahuila, México no se alineaban con el protólogo de A. ludovicianum, de A. multiflorum o de alguna otra especie de Aphyllon. La morfología floral, rango geográfico y la especie de planta hospedera fueron incluidas en esta comparación utilizando ejemplares de herbario y múltiples fotografías a color. Proponemos el nuevo binomio Aphyllon spectabile para las plantas de Nuevo León y Aphyllon gypsophilum para las plantas de Coahuila, llevando la total diversidad taxonómica a 27 especies de Aphyllon y 10 subespecies adicionales. Gymnosperma glutinosum y dos especies de Xanthisma son reportadas por primera vez como planta hospedera para el género Aphyllon. Se presenta una clave actualizada de Aphyllon en México.

The genus Aphyllon A.Gray (Orobanchaceae) is distributed throughout the western hemisphere, but is most species-rich in western North America. During the examination of herbarium exsiccatae for the Flora of North America (Collins et al. 2018), several accessions of the genus Aphyllon could not be assigned an available binomial. Two such groups of these specimens originated from northeastern Mexico; one set from the area surrounding Monterrey, Nuevo León, and the other from the Cuatro Ciénegas Bolson in Coahuila. Meanwhile, observations of the plants near Monterrey began to appear on the iNaturalist.org website (Ernesto 2015). Compared with known species of Aphyllon from northeastern Mexico and southern Texas, these plants were striking because of the large colorful flowers (Fig. 1). The second set of specimens, around Cuatro Ciénegas Bolson and apparently confined to gypsum dune habitat, stood out by their rather small corollas with extremely short corolla lobes (Fig. 2).

Many of these plants had previously been identified as A. ludovicianum (Nutt.) A.Gray or A. multiflorum (Nutt.) A.Gray, two closely related species within Aphyllon sect. Nothaphyllon A.Gray. Within the section, both species are part of a complex with racemose inflorescences, informally called the A. ludovicianum complex (Collins 1973; Collins et al. 2009; Schneider et al. 2016), in contrast to species with corymbose inflorescences (A. californicum complex) or those that have a small number of clustered flowers with long pedicels (A. sect. Aphyllon).

As Collins (1973; Collins et al. 2009) pointed out, the binomial Aphyllon ludovicianum (as Orobanche) has been historically applied to plants now representing at least four different species, including A. cooperi A.Gray, A. validum (Jeps.) A.C.Schneid, and the more recently described A. arizonicum (L.T.Collins) A.C.Schneid. and A. riparium (L.T.Collins) A.C.Schneid. Since all these species have racemose (spikelike) inflorescences among other shared morphological features, it is understandable that earlier researchers did not distinguish them. Especially so, given that few specimens, sometimes fragmentary, were available for examination at the time of the descriptions.

Likewise, the taxon Aphyllon multiflorum (Nutt.) A.Gray has been treated in a variety of ways, from Munz's (1930) recognition of four varieties of this species (classified in Orobanche) to Holmes and White's (2001) demotion of rank to a subspecies of Orobanche ludoviciana. While A. multiflorum has been reported in Mexico, we suspect the name has been misapplied. No vouchered specimens from Mexico were observed in this study that could be correctly identified to this taxon.

Finding distinguishing characters in the genus Aphyllon is a difficult task due to the many shared morphological characters and the absence of true leaves and roots. As a result, almost all useful taxonomic characters in the genus are found in the inflorescence and flowers. Several species of Aphyllon in Mexico are similar in overall appearance and share several morphological characters in common, including A. cooperi subsp. Palmeri (Munz) A.C.Schneid., A. ludovicianum, and A. castilloi Franc.Gut., Cháazaro, & Espejo. Hence, it was necessary to assess their phylogenetic relationships and to find morphological characters that could easily separate the species.

Materials and Methods

Species Characterization—Data were obtained from two sources, herbarium exsiccatae and geolocated color photographs. Morphological data were obtained from herbarium specimens from the following collections; ANSM, ASU, F, ILL, MO, NY, TEX-LL, and US. Online records and scans of Aphyllon specimens from several Mexican herbaria (ANSM, UNAM, CFNL) were also observed. Data for Coahuila plants were obtained entirely from dried herbarium specimens from two herbaria, TEX-LL and ASU. SEINnet ( https://swbiodiversity.org/seinet/index.php) records of Aphyllon from Mexico were also searched, but no additional matching images were found. Finally, measurements and morphological structures were compared with several closely related species (Table 1). Aphyllon dugesii S.Watson was not included in the comparative study due to uncertain taxonomic status but is quite distinct from A. ludovicianum and its segregates.

Fig. 1.

Photographs comparing (A) Aphyllon ludovicianum, (B) Aphyllon multiflorum, and (C) Aphyllon spectabile.

img-z2-1_587.jpg

Further assessment of qualitative characters of plants from Nuevo León such as color, shape of floral parts, and inflorescence type, was based on 54 photographs from 50 iNaturalist records of plants in situ (iNaturalist 2023). Unfortunately, such records of the Coahuila plants were not available for examination, nor was fresh material.

Phylogenetic Analysis—DNA from three specimens of A. spectabile, including the holotype, and as well as one specimen of A. gypsophilum were extracted from dried floral tissue using a Qiagen DNeasy Plant Pro Kit. The five nuclear ribosomal (ITS and ETS) and plastome (matK, rps2, and trnL-trnF) regions used by Schneider et al. (2016) were amplified and Sanger sequenced following their methodology. Sequence chromatograms were inspected for quality and trimmed, then aligned with existing nuclear ribosomal and concatenated plastid sequence alignments from Schneider et al. (2016) using the MUSCLE plugin for Geneious 9.1.8. To expand geographic sampling of closely related species, we also extracted and sequenced DNA from one specimen of A. ludovicianum from Florida (Schneider et al. 2021), and one specimen of A. riparium from Arizona. Newly generated sequences were deposited to GenBank (Appendix 1), and sequence alignments have been deposited in the Dryad Digital Repository (Collins et al. 2023).

Maximum likelihood phylograms were inferred by RAxML-NG (Kozlov et al. 2019) using the CIPRES Science Gateway (Miller et al. 2010). We applied a GTR 1 G nucleotide substitution model, partitioned by each cpDNA gene, 500 rapid bootstrap replicates, and used one or two specimens of A. pinorum (Hook.) A.Gray (Colwell 96-WA-LC1 and Egger 804, vouchers at WTU) as an outgroup.

Taxonomic Treatment

  • Aphyllon spectabile L.T.Collins, Velazco, & A.C.Schneid., sp. nov. Type: Mexico. Nuevo León: Santa Catarina, La Huasteca Park entrance, 21 Aug 2021, Carlos Velazco s.n. (holotype: MO).

  • Plants unbranched (excluding inflorescence), 7–27 cm. Stem base not or only slightly enlarged. Roots few to many, short, fragile, root mass poorly developed and less than 10 mm in diameter. Leaves several to numerous, lanceolate or broadly triangular, 3–10 mm, glabrous, margins entire, or sometimes ciliate. Inflorescences compact racemes, short or elongate, glandular-puberulent, rarely branched, pallid (sometimes entirely creamy-white) or purple tinged, bracts narrowly lanceolate to lanceolate, 11–20 mm, apex acute or acuminate, densely glandular-pubescent. Pedicels 0–5(10) mm, only proximal flowers pedicellate; bracteoles 2. Flowers: calyx (15)19–23 mm, slightly asymmetric, cup 4–5 mm, lobes 15–16 mm, reflexed, narrowly lanceolate-attenuate, pallid externally or purple tinged, purple internally, densely glandular pubescent; corolla 35–40 mm, tube white, pubescent externally, only slightly bent, mouth flared, abruptly constricted above ovary, purple veins in the lobes but not in the tube; palatal folds prominent, yellow, pubescent; abaxial (lower) lip 12–15 mm, lobes dark purple, lavender or white, rarely pale blue, apex obtuse or rounded, margins incurved or involute; adaxial(upper) lip 12–15 mm, erect or reflexed, dark purple, lavender, or rarely white, or pale blue, lobes erect or reflexed, sometimes torqued (bent) centripetally, rounded, margins entire, undulate or erose, pubescent or glabrous; filaments pilose, glabrous at insertion, anthers included, pilose; stigma peltate, discoid-crateriform or 2-lobed, sometimes with a descending narrow appendage. Fruit: Capsule. Flowering from Nov–May, most frequently in Feb and Mar. Figure 1C.

  • DiagnosisAphyllon spectabile can be distinguished from A. ludovicianum by its much larger flowers, narrow distribution range around Monterrey, Mexico, and the unique host species Gymnosperma glutinosum.

  • DistributionAphyllon spectabile is restricted to a small area in the Sierra Madre Oriental in northeastern Mexico, in the vicinity of Monterrey, Nuevo Leon, including Sierra de las Mitras, Sierra de la Sillas, and Sierra de la Loma Largo. A single specimen is reported from the adjacent state of Coahuila, with the location given only as “Saltillo.” Since the authors were not able to access other collections from the Sierra Madre Oriental, it is possible that the species is more widely distributed than indicated in this treatment.

  • Habitat—The species occurs in the zone of xeric vegetation (mattoral xerofila) primarily on arid and semiarid mountain slopes of the Sierra Madre elevations between 500 and 1500 m. This species is found in several different vegetation assemblages within this zone, whereas A. ludovicianum is primarily found in prairies.

  • Host—The only reported host species is Gymnosperma glutinosum Less. (Asteraceae), although the authors were not able to confirm this association by direct observation. Aphyllon was not previously known to parasitize Gymnosperma Less., but other members of the subtribe Gutierreziinae do serve as host species, including Gutierrezia Lag. (A. arizonicum, A. multiflorum), and Euthamia (Nutt.) Cass. (A. californicum subsp. grayanum (Beck) A.C.Schneid.; herbarium vouchers Colwell 1425 at YM; Mason 12127, JEPS 20913).

  • Etymology—The epithet spectabile refers to the distinctively large and brightly colored flowers.

  • Phylogenetic Affinities—Phylogenetic evidence strongly supports the placement of A. spectabile within the A. ludovicianum complex, although existing markers are not sufficient to further resolve most species within this clade, nor provide support for or against species monophyly (Fig. 3).

  • Notes—Morphologically, several floral characters clearly differentiate Aphyllon spectabile from A. ludovicianum and other close relatives or co-occurring species (Table 1). The corollas of A. spectabile are 35–45 mm long, which is approximately double the size of the 14–20 mm long corollas of A. ludovicianum. Likewise, the corolla lobe lengths of A. spectabile (13–15 mm) are about twice as long as those of A. ludovicianum (5–8 mm long). Only the highly disjunct A. californicum has flowers this large, but the two species differ in floral architecture, biogeographic distribution, and host affinity (Tables 1, 2).

  • The corolla tube of A. spectabile is white with large purple lobes, purple veins, and measuring about 10 mm at the opening. This is noticeably different from A. ludovicianum, in which the tube is lavender, pinkish, or yellow, rarely pure white, with lobes similarly colored, without purple veins and measuring only about 5 mm at the opening. Additionally, the margins of lower corollas lobes are involute in A. spectabile, while the margins in A. ludovicianum are only slightly incurved.

  • Ecologically and biogeographically, Aphyllon spectabile and A. ludovicianum are also distinct. A. ludovicianum is a prairie species distributed throughout the North American Prairies to the eastern slopes of the Rocky Mountains. It utilizes a variety of host species, but is found primarily on Artemisia L. spp., Heterotheca Cass. sp., and Grindelia squarrosa (Pursh) Dunal, but never Gymnosperma.

  • Contrasted with the two previously mentioned species, A. multiflorum has intermediately sized corollas that are 22–36 mm long with lobes 5–9 mm long (Table 1). The distribution of A. multiflorum is in the arid grasslands and semi-desert of the southern plains in Colorado, New Mexico, and western Texas. The primary host is Gutierrezia sarothroe (Pursh) Britton & Rusby, but occasionally is found on Heterotheca spp.

  • The only other species that occurs with A. spectabile in the Sierra Madre in the vicinity of Monterrey, Mexico is Aphyllon cooperi A.Gray. However, several morphological characters distinguish these two taxa, most notably corolla and calyx measurements and corolla lobe differences (Table 2). Host and phylogenetic position are also highly distinct from A. spectabile (Fig. 3).

  • Additional Specimens ExaminedMexico.Coahuila: Saltillo [no location or habitat data], 1–15 Apr 1880, E. Palmer s.n. (NY). NUEVA LEON: near Monterrey, 20 May 1900, Wm. Canby 183 (TEX). Monterrey, 3 Mar 1900, Trelease 183 (MO, GH). 5 miles SE of Monterrey, J.T.Bucholz s.n. (ILL). Corrizalejo, 3 miles out [from Monterrey?], 23 Mar 1946, Jose Roybal 48 (US). Monterrey, 20 Apr 1947, M.M. Lacas 266 (F). Monterrey, Obispado, 1 May 1947, M.M. Lucas 338 (F). Hillside, thorny vegetation, Monterrey, San Augustino, 22 Apr 1960, Robert F. Smith M125 (TEX). Loma larga, frente Monterrey, 15 Nov 1966, Jose Luis Gutierrez 220 (TEX). Estación Mariposa between Monterrey and Saltillo, 30 May 1981, M. Lane & M. Leidig 2895 (TEX). Gypsum hills, Santa Rosa, Reyones, n.d., G.B. Hinton 21789 (TEX).

  • Fig. 2.

    Photographs of herbarium specimens comparing Aphyllon ludovicianum with Aphyllon gypsophilum. A. Aphyllon ludovicianum with lanceolate bracts (at white wedges). B–C. Aphyllon gypsophilum. B. Inflorescence at anthesis showing glabrous anthers. C. Infructescence with unique deltoid bracts and apiculate apices. Voucher specimens: (A) Collins 2024 (MO); (B–C) Lewis s.n. (ASU). Scale bars 5 1.00 cm.

    img-z3-1_587.jpg

    Table 1.

    Morphological comparison of A. spectabile and A. gypsophilum with six other species of Aphyllon. Diagnostic characters for each species indicated in bold font. Data for A. castilloi and A. chiapense taken from the protologues of these taxa (Francisco-Gutiérrez et al. 2019; Francisco-Gutierrez and Alvarado-Cárdenas 2023).

    img-z4-2_587.gif

    Fig. 3.

    Relationship of Aphyllon spectabile to close relatives in A. sect. Nothaphyllon based on plastid (cpDNA) and nuclear ribosomal (nrDNA) evidence. Bootstrap support . 75% shown. Clade of 22 specimens representing seven species collapsed for concision. Collector, collection number, herbarium, and herbarium accession number shown at tips.

    img-z5-1_587.jpg
  • Aphyllon gypsophilum L.T.Collins sp. nov. Type: Mexico: Coahuila: Along road to gypsum dunes 4 miles w of Cuatro Ciénegas hwy [30], 10 Jun 1968, Donald Pinkava 5271 (Holotype: LL, Isotype ASU).

  • Plants annual, stems slender, 15–21 cm long, 2–3(5) mm diam, unbranched, stem base not enlarged. Roots few simple, mass poorly developed less than 10 mm in diameter. Leaves few, lanceolate, 6–10 mm long, glabrous, margins entire, sometimes minutely ciliate. Inflorescence dense raceme, 3–9 cm long, rarely branched; glandular pubescent, floral bracts 9–10 mm, proximal narrow lanceolate, distal deltoid with apiculate apex, purple tinged, glandular pubescent, apex pubescent. Pedicels 0–3 mm (10 mm proximally), bracteoles 2; Flowers: calyx 7–10 mm, ± symmetric; purple tinged, lobes 4–6 mm, narrowly lanceolate-attenuate; corolla 8–15 (17) mm, tube almost straight, pale, slightly constricted above ovary, glandular pubescent becoming glabrate, lobes purple, 2 mm long, 1–2 mm wide, apex rounded; palatal folds not prominent, pubescent; anthers 1–1.5 mm, glabrous, filament glabrous, pubescent at insertion; Fruit: Capsule oval to ovate, 6–7 mm long. Flowering Apr–Oct. Figure 2.

  • Diagnosis—Superficially, A. gypsophilum and A. ludovicianum seem almost identical, however, the fine details of the flower and the ecological data clearly separate the two species. Aphyllon gypsophilum can be distinguished from A. ludovicianum by its smaller flowers, extremely short corolla lobes, and deltoid bracts in the inflorescence, and the unique host species Xanthisma gypsophilum (B.L.Turner) D.R.Morgan & R.L.Hartm. and X. restiforme (B.L.Turner) D.R.Morgan & R.L.Hartm. In fact, the host affinity and presence of dimorphic floral bracts sets A. gypsophilum apart from all other species. Aphyllon gypsophilum occurs exclusively in gypsum sand dunes whereas A. ludovicianum is a prairie species primarily parasitizing Artemisia L. spp., Heterotheca spp., and Grindelia squarrosa (Pursh) Dunal.

  • Distribution and HabitatAphyllon gypsophilum appears to be endemic to the Cuatro Ciénegas Bolson which is part the Chihuahuan Desert in the state of Coahuila, Mexico. Within the bolson, the plants only occur in the gypsum sand dunes.

  • Host—This species parasitizes at least two gypsophilic species of Xanthisma (Machaeranthera). Xanthisma restiforme is endemic to the Cuatro Ciénegas gypsum dunes (Turner 1973). The second host, X. gypsophilum, is another gypsophile widely distributed in the Chihuahuan Desert. This is the first report of a gypsophilic host for the genus Aphyllon and the first report of Xanthisma as host for a species of Aphyllon, though several other species do parasitize its close relative Grindelia.

  • Etymology—The epithet ‘gypsophilum’ refers to the distinctive gypsum sand dune habitat and the host Xanthisma gypsophilum.

  • Phylogenetic Affinities—Phylogenetic evidence using nuclear ribosomal genes strongly supports the placement of A. gypsophilum within the A. ludovicianum complex and a sub-clade (BS 5 93) composed in part of the South American taxa A. chilense and A. tacnense (Fig. 3; Schneider et al. 2016). All known hosts parasitized by members of this clade are in the subtribe Machaerantherinae of the Astereae. The single sample of A. gypsophilum resolved sister to the rest of the clade with very weak support (BS 5 66).

  • Notes—Morphologically, A. gypsophilum resembles A. ludovicianum, but is noticeably smaller in all aspects with slender delicate stems. The flowers are much smaller with rather short narrow corolla lobes (2 mm long by 1 mm wide when dried). The corolla tube is only slightly bent, sometimes essentially straight, and has reduced pubescence, becoming glabrate with age. Inside the corolla tube there is pubescence around the base of the filaments at the insertion, but otherwise the inner tube is glabrous. Although this character occurs in a few other species of Aphyllon, it is not known in Aphyllon ludovicianum which does not have pubescence in the corolla tube. Other taxa known in Mexico also have glabrous filaments.

  • Most individuals of Aphyllon gypsophilum have two distinctly differently shaped floral bracts (Fig. 2). The lower portion of the inflorescence has lanceolate bracts with acute apices which is typical for the genus. However, in the upper portion of the inflorescence the bracts are oval or deltoid with a distinct apiculate apex (Fig. 2C). These deltoid bracts with apiculate apex have not been reported before in Aphyllon. This is unusual as floral bracts in Aphyllon are generally rather uniform throughout the plant, mostly lanceolate or triangular, varying only slightly in shape, length and width, with an occasional variation of the apex. Hence, they are usually of minimal value taxonomically. This is the first report of dimorphic floral bracts in a species of Aphyllon, though a single specimen was observed with only lanceolate bracts.

  • Additional Specimens ExaminedMexico.Coahuila: 1.8 miles sw of Posa de la Becarra opposite Laguna Grande, 9 Jun 1968, Donald Pinkava et al. 5178, (ASU). Along road to gypsum sand dunes 4 miles west of Cuatro Ciénegas hwy, 10 Jul 1968, Donald Pinkava et al. 5276 (ASU). 1.1 mi s of Puerto Salada along road & canal to Santa Tecla, 13 Jun 1968, Donald Pinkava et al. 5564 (ASU). Mt. Anteojo, 17 Jun 1968, Donald Pinkava et al. 5764 (ASU). Tip of Sierra de San Marcos, 10–15 Aug 1968, Janice Lewis s.n. (ASU; Fig. 2B, C). Gypsum dunes 12 mi southwest of Cuatro Ciénegas on Hwy 30, 16 Oct 1971, J. Bacon & W.R. Leverich 1146 (TEX). Gypsum dunes 22 mi southwest of Cuatro Ciénegas, 3 Apr 1972, A.M. Powell & B.L. Turner 2241 (TEX). Gypsum dunes 12 miles southwest of Cuatro Ciénegas, 18 Aug 1973, James Hendrickson 12537 (TEX). Poza El Bonito, Cuatro Ciénegas, Coahuila, 16 Jun 1977, J. Marroquín s.n. (ANSM).

  • Table 2.

    Biogeographical and ecological comparison of A. spectabile and A. gypsophilum with six other species of Aphyllon sect. Nothaphyllon. Asterisk denotes multiple subspecies included.

    img-z6-2_587.gif

    Discussion

    Aphyllon Diversity in Mexico—In the first two decades of the 21st century, seven new species of Aphyllon were added to the flora of North America, including Mexico. Along with A. spectabile, A. gypsophilum, and the recently described Aphyllon chiapense Francisco-Gutierrez, this is a total of ten new species added to the genus, all but three of which are in A. section Nothaphyllon, which comprises over eighty percent of the species in the genus. Numerous specimens currently in herbaria cannot be identified with confidence because they do not fit the protologue of known species and at least two published names remain poorly defined, Aphyllon dugesii Wats. and a variety of A. multiflorum that lacks an available name in the genus (basionym Orobanche multiflora var. pringlei Munz).

    The concept of A. dugesii is presented quite differently by Collins and Yatskievych (2015) and de Rzedowski (1998), and host affinities remain incomplete. On the other hand, documentation of Orobanche multiflora var. pringlei is almost nonexistent. Beyond the protologue (Munz 1930) and the two specimens from Chihuahua cited therein, not a single research paper discusses this variety. While the binomial A. multiflorum has been regularly applied to herbarium specimens for plants in western US and Mexico, the first author has searched diligently for other specimens to refer to this varietal name but has found none.

    Despite the recent progress, undescribed species of Aphyllon still exist. Some of these new forms parasitize unique hosts (e.g. Zaluzania Pers.) and clearly represent separate lineages (A. sp. nov. in Fig. 3; Schneider et al. 2016). In other cases, certain specimens simply do not seem to match any of the known species of Aphyllon in North America. Despite the recent addition of species to the genus, especially in Mexico, the rate of increase should alert the botanical community that additional explorations will almost certainly yield further discoveries.

    Further Evidence for Madrean Diversification of Aphyllon—The expanded recognition of taxonomic diversity of Aphyllon in Mexico further refines understanding of the diversification and biogeography of the genus as a whole. Four new species have been split from A. ludovicianum in the last four years, and at least one more awaits a formal description. DNA sequence data from three of these (A. spectabile, A. gypsophilum, and the undescribed species parasitizing Zaluzania) show very little differentiation from other A. ludovicianum complex taxa (Fig. 3). Taken together, along with the edaphicendemic host in the case of A. gypsophilum, we suggest these newly described Mexican species of Aphyllon speciated in situ, in parallel with the diversification of Aphyllon californicum into a host-specific subspecies within the California Floristic Province over the last several hundred thousand years (Schneider and Moore 2017).

    More specifically, A. spectabile and A. gypsophilum both have narrow geographical distributions in the Sierra Madre Oriental and Chihuahuan Desert Region, and likely evolved there. The Chihuahuan Desert is the largest desert in North America and arguably the most biologically diverse desert in the Western Hemisphere, with some 3382 plant species, of which at least 826 taxa are endemic or nearly endemic (Daniel 2022). Pinkava (1984) reported 23 species as endemic to the Cuatro Ciénegas Bolson, including several endemic gypsophiles or halophiles. The two gypsophile species of Xanthisma cited earlier are a part of this specialized assemblage, and by way of association, A. gypsophilum must be added to this list as well. Although the area around Monterrey where A. spectabile occurs is not technically part of the Chihuahuan Desert, the vegetation is significantly influenced by the adjacent desert biota.

    Phylogenetic data is not yet available for two of the southernmost Mexican species of Aphyllon, A chipanese and A. castilloi, however, the protologues hypothesize an affinity to A. dugesii and A. cooperi subsp. palmeri. If this is correct, these species would represent a separate burst of diversification onto unique hosts in tropical forests within a separate clade that is about twice as old as the A. ludovicianum complex (Schneider et al. 2016; Schneider and Moore 2017; Francisco-Gutierrez et al. 2019; Francisco-Gutierrez and Alvarado-Cárdenas 2023). Further clarification of taxonomic limits (A. dugesii, species novae, etc.), and improved phylogenetic resolution towards the tips of the phylogeny will continue to refine relationships among individual taxa, the extent and significance of Mexican centers of diversity, and precision in reconstructing the geographic origin of key clades, including Aphyllon itself.

    Key to Aphyllon in Mexico

    1. Pedicels 10–110 mm, equal to or longer than plant axis; bracteoles subtending calyx absent (but floral bract subtending each pedicel present)

    2 [A. sect. Aphyllon]

    2. Corollas yellow, flowers in fascicles, of 6–15(–20) flowers, forming an irregular corymb, nw Mexico, especially n Baja, host not Asteraceae A. franciscanum

    2. Corollas white or tinged lavender, flowers 1–3 per inflorescence, host Asteraceae: Astereae. (widespread in USA and Canada but known in Mexico only from a single disjunct collection from Oaxaca: Camp 2451, NY). A. uniflorum

    1. Pedicels 0–30 mm, shorter than plant axis; bracteoles 2; inflorescences racemes, sometimes spikelike, corymbs, or panicles, corollas purple, lavender, pink, maroon or white, flowers numerous, 3 [A. sect. Nothaphyllon]

    3. Corolla lobe apices rounded or obtuse; plants lavender, pinkish, yellow, or sometimes purple 4

    4. Corolla lobes ovate, 3–5 mm long, 1–3 mm wide; tropical forests in s Mexico 5

    5. Corolla mouth open, lower lobes slightly reflexed, apex rounded, host Simsia foetida; known only from tropical semideciduous forest in Veracruz A. castilloi

    5. Corolla mouth closed, lower lobes not spreading or reflexed, apex bifid; known only from tropical forest in Chiapas A. chiapense

    4. Corolla lobes oblong, 4–15 mm long, 3–9 mm wide; hosts Asteraceae other than Simsia foetida; known mostly from arid or semiarid prairies, desert, or mountains 6

    6. Corolla lips internally maroon or reddish purple, sometimes with maroon or reddish-purple stripes, veins, or blotches; palatal folds glabrous; Baja California A. parishii

    6. Corolla lips internally purple or pink, sometimes white with purple veins, rarely light yellow; palatal folds pubescent 7

    7. Inflorescence corymbose; n Baja California A. californicum subsp. feudgei

    7. Inflorescence racemose or spike-like 8

    8. Corollas 8–20 mm, lips 2–6 mm; anthers glabrous or with a few hairs 9

    9. Corollas 14–20 mm, lips 3–6 mm; filament glabrous at insertion; prairies and arid grasslands, known along the Rio Grande in Coahuila A. ludovicianum

    9. Corollas 8–15 mm, lips 2 mm; filament pubescent at insertion; gypsum dunes in Cuatro Ciénegas, Coahuila A. gypsophilum

    8. Corollas 22–45 mm, anthers wooly or lanate 10

    10. Corollas 22–36 mm, upper lobes 5–12 mm; anthers woolly; ring of hairs at base of filaments; not documented in Mexico; only southern USA A. multiflorum

    10. Corollas 35–45 mm, upper lobes 10–15; anthers lanate; filaments glabrous at base; Nuevo Leon, Monterrey and vicinity A. spectabile

    3. Corolla lobe apices acute, pointed, or with an apiculate tooth; plants mostly dark purple 11

    11. Inflorescence a raceme; corolla 15–32 mm, tube lavender, or white, tinged with purple, lips dark purple to lavender, with darker purple veins, lobes often with apiculate teeth; anthers mostly pubescent and usually with inconspicuous stalked glands A. cooperi

    a. A. cooperi subsp. cooperi – Sonoran Desert

    b. A. cooperi subsp. latiloba – Sonoran Desert

    c. A. cooperi subsp. palmeri – Chihuahuan Desert

    11. Inflorescence a pyramidal panicle; corollas 13–19 mm, dark purple throughout, lobes sometimes with white margins; anthers glabrous or sparsely pubescent; palatal folds not prominent, pale or light yellow; host Adenostema fasciculatum; chaparral, n Baja California . A. tuberosum

    Acknowledgments

    We thank the curators of the following herbaria for their maintenance and continued access to specimens: ANSM, ASU, F, ILL, MO, NY, TEX-LL, and US. The first author was supported by a grant from the Evangel University Faculty Summer Research Program and in-kind support from Evangel University. Photos of living specimens were contributed by the second author (Aphyllon ludovicianum, Fig. 1A,  https://www.inaturalist.org/observations/27401451), Alejandra Salinas-Camarena, (Aphyllon spectabile, Fig. 1B,  https://www.inaturalist.org/observations/65888167) and Christian Schwarz (Aphyllon multiflorum, Fig. 1C,  https://www.inaturalist.org/observations/4052424). Photos of herbarium specimens were contributed by the first author (Collins 2024, MO, Fig. 2A), and by courtesy of ASU herbarium (Lewis s.n.; Fig. 2B–C), with the assistance of Colton Shrader at Evangel University. George Yatskievych (TEX) and Elizabeth Makings (ASU) provided samples for DNA analysis. GY also provided detailed observations on specimens from TEX. José Villareal-Quintanilla provided scanned images and information from ANSM. We also thank Dan Potter and Richard Olmstead for their useful feedback and assistance during the peer-review process.

    © Copyright 2023 by the American Society of Plant Taxonomists

    Author Contributions

    LTC conducted the morphological comparisons, was the primary author of both species descriptions, and co-wrote the Discussion. CV collected the holotype of A. spectabile, and provided photographs, field notes, and ecological data for this species. ACS contributed the molecular phylogenetic analysis for both species, co-wrote the Discussion, and edited the content and organization elsewhere. The final manuscript was read, edited, and revised by all authors.

    Literature Cited

    1.

    Collins, L. T. 1973. Systematics of Orobanche section Myzorrhiza. Ph.D. dissertation. Milwaukee: University of Wisconsin. Google Scholar

    2.

    Collins, L. T. and G. Yatskievych. 2015. Orobanche arizonica sp. nov. and nomenclatural changes in Orobanche cooperi (Orobanchaceae). Phytoneuron 48: 1–19. Google Scholar

    3.

    Collins, L. T., A. Colwell, and G. Yatskievych. 2009. Orobanche riparia, a new species from the American Midwest. Journal of the Botanical Research Institute of Texas 3: 3–11. Google Scholar

    4.

    Collins, L. T., A. Colwell, and G. Yatskievych. 2018. Orobanche . Pp. 467–488 in Flora of North America North of Mexico , vol 17, eds. Flora of North America Editorial Committee. New York and Oxford: Oxford University Press. Google Scholar

    5.

    Collins, L. T., C. Velazco, and A. Schneider. 2023. Data from: Two New Species of Aphyllon from Northeastern Mexico. Dryad Digital Repository. https://doi.org/10.5061/dryad.bzkh189gc. Google Scholar

    6.

    Daniel, T. F. 2022. Donald Pinkava's studies on the vascular flora of the Bolsón de Cuatro Ciénegas in the Chihuahuan Desert, updates, and taxonomic information on Acanthaceae in the region. Journal of the Botanical Research Institute of Texas 16: 281–295. Google Scholar

    7.

    Ernesto, R. 2015. iNaturalist Observation:  https://www.inaturalist.org/observations/1805535(accessed 25 February 2023). Google Scholar

    8.

    Francisco-Gutierrez, A. and L. O. Alvarado Cárdenas. 2023. A new tropical species of Aphyllon (Orobanchaceae: Orobancheae) from Chiapas, Mexico. Botanical Sciences 101: 1–10. Google Scholar

    9.

    Francisco-Gutiérrez, A., M. Cháazaro-Basáñez, A. Espejo-Serna, J. GarcíaFranco, and G. Torres-Cantú. 2019. Aphyllon castilloi sp. nov. (Orobanchaceae) from Veracruz, Mexico. Nordic Journal of Botany 37: 1–8. Google Scholar

    10.

    Holmes, W. C. and H. L. White. 2001. Validation of the name Orobanche ludoviciana subsp. multiflora (Orobanchaceae). Sida 19: 623–624. Google Scholar

    11.

    iNaturalist. 2023. iNaturalist research-grade observations. iNaturalist.org. Occurrence dataset  https://doi.org/10.15468/ab3s5x(accessed via GBIF.org on 25 February 2023). Google Scholar

    12.

    Kozlov, A. M., D. Darriba, T. Flouri, B. Morel, and A. Stamatakis. 2019. RAxML-NG: A fast, scalable and user-friendly tool for maximum likelihood phylogenetic inference. Bioinformatics 35: 4453–4455. Google Scholar

    13.

    Miller, M. A., W. Pfeiffer, and T. Schwartz. 2010. Creating the CIPRES Science Gateway for inference of large phylogenetic trees. Pp. 1–8 in Proceedings of the Gateway Computing Environments Workshop (GCE) . New Orleans: Gateway Computing. Google Scholar

    14.

    Munz, P. A. 1930. The North American species of Orobanche section Myzorrhiza . Bulletin of the Torrey Botanical Club 57: 611–624. Google Scholar

    15.

    Pinkava, D. J. 1984. Vegetation and flora of the Bolson of the Cuatro Cienegas region, Coahuila, Mexico: IV. Summary, endemism and corrected catalogue. Journal of the Arizona-Nevada Academy of Science 19: 23–47. Google Scholar

    16.

    de Rzedowski, G. C. 1998. Orobanchaceae. Flora del Bajío y de Regiones Adyacentes 69: 1–12. Google Scholar

    17.

    Schneider, A. C. and A. J. Moore. 2017. Parallel Pleistocene amphitropical disjunctions of a parasitic plant and its host. American Journal of Botany 104: 1745–1755. Google Scholar

    18.

    Schneider, A. C., A. E. L. Colwell, G. M. Schneeweiss, and B. G. Baldwin. 2016. Cryptic host-specific diversity among western hemisphere broomrapes (Orobanche s.l., Orobanchaceae). Annals of Botany 118: 1101–1111. Google Scholar

    19.

    Schneider, A. C., J. Bickell, B. E. Benton, and L. T. Collins. 2021. Aphyllon ludovicianum (Orobanchaceae), newly reported in coastal Alabama and Florida, U.S.A. Journal of the Botanical Research Institute of Texas 15: 583–585. Google Scholar

    20.

    Turner, B. L. 1973. Machaeranthera restiformis (Asteraceae), a bizarre new gypsophile from Northcentral Mexico. American Journal of Botany 60: 836–838. Google Scholar

    Appendices

    Appendix 1.

    Voucher information for specimens newly sequenced in this study. Presented in the following format: SpeciesCollector, Herbarium: GenBank accession codes for ITS, ETS, matK, rps2, trnLtrnF spacer, with missing data indicated by —. All other GenBank and herbarium voucher information available in Supplementary Information of Schneider et al. (2016).

    Aphyllon gypsophilumLewis s.n. ASU: OR478190, OR479190, —, —, —. A. ludovicianumSchneider 1273 FLAS279546: OQ645744, OQ674032, —, —, —. A. ripariumCoburn 3120MO: OR478189, OR479189, —, —, OR479191. A. spectabileLane 2895 TEX00105262: OQ645746, OQ674034, OQ675261, OQ674037, —; Hinton 21789 TEX00105269: OQ645745, OQ674033, —, OQ674036, OQ674038; Velazco s.n. (holotype) MO: OQ645747, OQ674035, OQ675262, —, OQ674039. A. sp.Moran 7703 SD117784: OQ645743, —, —, —, —.

    L. Turner Collins, Carlos Velazco, and Adam C. Schneider "Two New Species of Aphyllon from Northeastern Mexico," Systematic Botany 48(4), 587-594, (30 December 2023). https://doi.org/10.1600/036364423X17000842213560
    Published: 30 December 2023
    KEYWORDS
    endemic
    iNaturalist
    key
    phylogeny
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