Phylogenetic relationships in Coryphantha and implications on Pelecyphora and Escobaria (Cacteae, Cactoideae, Cactaceae).

The genus Coryphantha includes plants with globose to cylindrical stems bearing furrowed tubercles, flowers arising at the apex, and seeds with flattened testa cells. Coryphantha is the second richest genus in the tribe Cacteae. Nevertheless, the genus lacks a phylogenetic framework. The limits of Coryphantha with its sister genus Escobaria and the infrageneric classification of Coryphantha have not been evaluated in a phylogenetic study. In this study we analyzed five chloroplast regions (matK, rbcL, psbA-trnH, rpl16, and trnL-F) using Bayesian phylogenetic analysis. We included 44 species of Coryphantha and 43 additional species of the tribe Cacteae. Our results support the monophyly of Coryphantha by excluding C.macromeris. Escobaria + Pelecyphora + C.macromeris are corroborated as the sister group of Coryphantha. Within Coryphantha our phylogenetic analyses recovered two main clades containing seven subclades, and we propose to recognize those as two subgenera and seven sections, respectively. Also, a new delimitation of Pelecyphora including C.macromeris and all species previously included in Escobaria is proposed. To accommodate this new delimitation 25 new combinations are proposed. The seven subclades recovered within Coryphantha are morphologically and geographically congruent, and partially agree with the traditional classification of this genus. Daniel Sánchez, Balbina Vázquez-Benítez, Monserrat Vázquez-Sánchez, David Aquino, Salvador Arias.

Introduction

(Engelm.) Lem. was described by Engelmann (1856) as a subgenus of Haw. Later, Lemaire (1868) raised it to generic level. Hunt and Benson (1976) proposed (Engelm.) Britton & Rose as the type of this genus. is morphologically characterized by adult plants with globose to cylindrical stems, covered with numerous spirally-arranged tubercles, flowers that arise at the apex of the stem, stem tubercles with a groove in maturity, and seeds with flattened testa cells (Anderson 2001; Dicht and Lüthy 2005; Hunt et al. 2006). Species of mainly inhabit the Mexican highlands in xerophytic shrublands and grasslands, although some prefer tropical deciduous forests and coniferous forests (Dicht and Lüthy 2005).

The taxonomy of has been complicated. Attributes such as the shape and size of the stem, the number, color, and orientation of the spines change according to the development state of the specimen, causing confusion with members of other genera such as Britton & Rose, , and Britton & Rose (Vázquez-Benítez et al. 2016). For instance, Benson (1969, 1982) recognized as a subgroup of because of the tubercle grooves, an opinion that persists to this day (Zimmerman and Parfitt 2004).

Species number in (excluding ) has varied over time, Lemaire (1868) recognized 25 species, Bravo-Hollis and Sánchez-Mejorada (1991) 59 species, Dicht and Lüthy (2001) and Hunt et al. (2006) 43 species, and Vázquez-Benítez et al. (2016) 45 species. This last study was based on a broad and inclusive morphometric analysis (Vázquez-Benítez et al. 2016). Regardless of the differences in species number, is the second richest genus in the tribe Cacteae (Vázquez-Benítez et al. 2016).

Current infrageneric classifications in have been entirely based on morphology, which has been evaluated according to different criteria, generating artificial classifications. Bravo-Hollis and Sánchez-Mejorada (1991) recognized three series within the genus: Britton & Rose, Lem., and Salm-Dyck. Dicht and Lüthy (2001, 2005) recognized two subgenera: and Backeb., divided into sections and series. Finally, Hunt et al. (2006) proposed an artificial classification in which three subgenera and three informal groups were recognized. Those proposals have been based on the presence/absence of extrafloral glands at the areole, the type of development and position of the areole on the tubercles, growth form and shape of the tubercle. None of these proposals has been evaluated within a phylogenetic framework.

A previous molecular phylogenetic study of the tribe Cacteae included a few species of the genus (Butterworth et al. 2002). This study suggested that is part of the (=mammilloid) clade, a group that includes other genera such as , , Alexander, and Ehrenb. The position of within mammilloid clade was further supported by other studies with better sampling and larger molecular data set (Butterworth and Wallace 2004; Crozier 2005; Bárcenas et al. 2011; Hernández-Hernández et al. 2011; Vázquez-Sánchez et al. 2013). Overall, these phylogenetic studies suggest that is not monophyletic (Bárcenas et al. 2011; Vázquez-Sánchez et al. 2013). Recently, Breslin et al. (2021) proposed the recircumscription of the mammilloid clade by recognizing three genera, , (K.Brandegee), and (including ). However, sampling in the clade was poor. In this study, we performed phylogenetic analyses focusing on the tribe Cacteae to test for the monophyly of and to better understand its relationship to . With the phylogenetic hypothesis obtained we evaluated the infrageneric classification proposed by Dicht and Lüthy (2005), and propose the set of morphological characters that define the genus .

Materials and methods

The monophyly of the tribe Cacteae has been largely corroborated by phylogenetic studies (Butterworth et al. 2002; Vázquez-Sánchez et al. 2013). The most comprehensive phylogenetic hypothesis of the tribe recovers three grades and the clade named “core Cacteae”, which is in turn composed by two subclades, the “ clade” and the clade B (henceforth “mammilloid clade”) (Vázquez-Sánchez et al. 2013). The present comprehensive study included 44 species of (95.6%), eight species of (44%), 30 additional taxa belonging to the “mammilloid clade”, four taxa of the “ clade”, 10 taxa of the “ clade”, and Link & Otto as the functional outgroup (Appendix 1). For the genus , we followed the species accepted by Dicht and Lüthy (2005) and those accepted by Arias et al. (2012). Our analyses included mostly new sequences for and complementary sequences previously published (Butterworth et al. 2002; Butterworth and Wallace 2004; Bárcenas et al. 2011; Hernández-Hernández et al. 2011; Fehlberg et al. 2013; Schwabe et al. 2015; Kuzmina et al. 2017; Aquino et al. 2019, and Vázquez-Sánchez et al. 2013, 2019) (Appendix 1).

Samples of plant tissue from the epidermis and hypodermis of the stem were dried, frozen, and pulverized. Total DNA extraction was achieved by using the DNeasy plant mini kit (Qiagen, California). We amplified chloroplast markers widely used in phylogenetic reconstruction in Cacteae (Vázquez-Sánchez et al. 2013, 2019). Specifically, we amplified the chloroplast coding regions matK and rbcL, and the intergenic spacers psbA-trnH and the trnL-trnF (including part of the trnL), and the rpl16 intron. Primers and profiles of thermal cycles followed Vázquez-Sánchez et al. (2013). The PCR products were sequenced at the High Throughput Genomics Unit at the University of Washington (now unavailable). Appendix 1 shows in detail the GenBank accessions for each taxon.

The sequences for each marker were assembled using SEQUENCHER (v. 4.8, Gene Codes Corporation 2007). The matrices were aligned manually with MESQUITE (v. 2.75, Maddison and Maddison 2015). Table 1 shows some numeric records about the taxa and the aligned sequences included in the subsequent analyses. Insertion-deletion events in aligned sequences (indels) were coded using the simple coding method (Simmons and Ochoterena 2000) (Appendix 2). Additionally, eight morphological characters, proposed as diagnostic for and related genera were coded and used in a combined phylogenetic analysis. It has been suggested that in the inclusion of indels and a set of morphological characters in phylogenetics analysis results in more accurate hypotheses (Sánchez et al. 2019; Martínez-Quezada et al. 2020). Character states were extracted from the descriptions of the species (Bravo Hollis and Sánchez-Mejorada 1991; Barthlott and Hunt 2000; Dicht and Lüthy 2005; Hunt et al. 2006) and corroborated in the field, in living collections (Jardín Botánico, Instituto de Biología, UNAM), and with herbarium specimens (MEXU). Characters and character states are listed in Table 2. DNA evolution models for each sequence were estimated using the corrected Akaike information criterion (AICc) in JMODELTEST2 (Darriba et al. 2012) on the CIPRES Science Gateway (v. 3.3 Miller et al. 2010) (Table 1). The Mkv model (Lewis 2001) was assigned for the indels and the morphological partitions. The first matrix was concatenated by including the five DNA regions. The second matrix included the five DNA regions and the indels partition. Finally, the third matrix included the five DNA regions, the indels and morphological characters. A partitioned Bayesian inference (BI) analysis was performed in MRBAYES (v. 3.2.1, Ronquist et al. 2012). The BI analysis for those matrices consisted of two runs of four chains for 20 million iterations, saving one tree every 1000 generations, and beginning with one random tree. The burn-in parameter was fixed as 25%.

Table 1.

Data of the aligned sequences used in the phylogenetic analysis.

	matK	psbA-trnH	rcbL	rpl16	trnL-F	Combo
Taxa	95/99	91/99	83/99	86/99	85/99	–
Length (aligned)	817	391	538	1349	1218	4313
Non-informative sites	730	313	509	1100	1048	3700
Informative sites	87	78	29	249	170	613
% informative sites	10.6	19.9	5.4	18.4	13.9	14.2
Informative indels	1	11	0	8	14	34
Substitution model	TPM1uf+I+G	TPM1uf+I+G	K80+I	TIM1+I+G	TVM+G	–

Table 2.

Characters and character states for the ancestral states reconstruction.

1. Growth form: (0) globose, (1) short cylindrical, (2) cylindrical, (3) depressed-globose.

2. Groove on tubercle in mature plant: (0) absence, (1) complete, (2) incomplete.

3. Extrafloral glands at or near the axil: (0) absence, (1) turgid throughout the year, (2) turgid only at flowering season.

4. Position of the flowers: (0) apical or nearly apical, (1) in a ring distant from the apex.

5. Margin of the outer tepals: (0) fimbriate, (1) entire.

6. Color of the mature fruit: (0) red-pink, (1) green, (2) yellow.

7. Type of cortex: (0) watery, (1) mucilaginous, (2) laticiferous.

8. Multicellular sculpture of the lateral side of the seed: (0) flat, (1) tuberculate, (2) pitted.

The ancestral states of the eight morphological characters were traced in the selected phylogeny to test them as potential synapormophies of clades. The tracing of characters was performed in MESQUITE (v.2.75, Maddison and Maddison 2015) using the parsimony ancestral state method on the majority consensus tree from the combined BI analysis.

Results

Phylogenetic analyses including DNA sequences only (Appendix 3: Fig. A1) and DNA sequences + indels partition (henceforth “molecular analysis”) showed identical topologies (Fig. 1). The phylogenetic analysis with morphological data (henceforth “combined analysis”) recovered a more resolved phylogeny (Fig. 2) with minor changes in the main clades, except for the position of one clade. In the molecular analysis, and were recovered as the sister clade to s.s. (PP = 0.96, Fig. 1). This clade formed a polytomy with and (including ) clades (Fig. 1). In the combined analysis, and were included in the clade PP = 0.98, Fig. 2). Each clade; , , , , and s.s. showed resolved relationships between them with moderate to low support (Fig. 2).

Figure A1.

Ancestral states reconstruction in and related genera A growth form B groove on the tubercle in mature plant C extrafloral glands at or near the axil D position of the flowers E margin of the outer tepals F color of the mature fruit G type of cortex H multicellular sculpture of the lateral side of the seed.

Figure 1.

Phylogenetic relationships of and close related genera. Majority rule phylogram, from the BI analysis using cpDNA sequences and indels partitions (molecular analysis). Numbers in nodes indicate posterior probabilities. Labels indicate the main recovered clades and subclades.

Figure 2.

Phylogenetic relationships of and close related genera. Majority rule phylogram, from the BI analysis using cpDNA sequences, indels, and morphological partitions (combined analysis). Numbers in nodes indicate posterior probabilities. Labels indicate the main recovered clades and subclades.

In all analyses the clade included (PP = 1.0) (PP = 0.7, Fig. 1; PP = 0.79, Fig. 2), and (PP = 0.8, Fig. 1; PP = 0.52, Fig. 2). Phylogenetic relationships in both analyses indicate that is not a monophyletic group, because was recovered in the clade (Figs 1, 2). s.s. is divided into two main clades, with 33 species grouped in clade I (PP = 0.99, Fig. 1; P = 1, Fig. 2), and 13 species grouped in clade II (PP = 0.91; Fig. 1; PP = 0.99. Fig. 2). Clade I is composed by five subclades (A, B, C, D, E), and Clade II by two subclades (F, G) (Figs 1, 2), all of them with high supports. The clade (PP = 0.98, Fig. 1; PP = 0.97, Fig. 2) is divided into two subclades, the first one includes , , , , , and (PP = 1, Figs 1, 2); while the second subclade includes , , , , and (PP = 1.0; Figs 1, 2).

The ancestral state reconstruction (Appendix 3: Fig. A1) showed that the presence of a complete groove on the tubercle (Appendix 3: Fig. A1B), the apical origin of the flowers (Appendix 3: Fig. A1D), the entire margin of the outer tepals (Appendix 3: Fig. A1E), the green color of the fruit (Appendix 3: Fig. A1F), and the flat multicellular sculpture of the lateral side of the seed (Appendix 3: Fig. A1H) were ancestral states to s.s., few or null changes on these characters states occurred inside the clade. In contrast, in the clade, the fimbriate margin of the outer tepals (Appendix 3: Fig. A1E), the red color of the mature fruit (Appendix 3: Fig. A1F), and the pitted multicellular sculpture of the seed were ancestral character states (Appendix 3: Fig. A1H). Additionally, growth form was ambiguous in s.s. and clade. The absence of glands near the axil of the tubercles was ancestral to s.s., and the presence of those glands evolved independently in two subclades of (Appendix 3: Fig. A1C). In clade II, turgid glands present all year-long were ancestral, while glands present only during flowering season evolved once in subclade D (Appendix 3: Fig. A1C. Finally, watery cortex was ancestral in s.s., but it changed into mucilaginous cortex in the subclade F (Appendix 3: Fig. A1G).

Discussion

The close relationships among , , , , and have been recognized by several studies (Butterworth and Wallace 2004; Crozier 2005; Vázquez-Sánchez et al. 2013; Breslin et al. 2021). Breslin et al. (2021) recovered them as closely related lineages and redefined their limits. These authors proposed to expand the limits of to include 37 species of , , and . Our results (Figs 1, 2) recovered, with moderate to low support, the same phylogenetic position of and . Additionally, was nested within . Morphological (Hunt 1985) and molecular evidence (Butterworth and Wallace 2004) suggest that is closely related to other taxa now classified within , so it should be transferred (see Taxonomic summary).

In the molecular analysis, and were recovered, with low support, as the sister group to s.s. In contrast, Breslin et al. (2021) found to be the sister to + . The addition of eight morphological characters in the combined analysis recovered and within the clade , and supported s.s. and as sister lineages. We argue that the low sampling of this early diverged lineage of (Butterworth and Wallace 2004) and the few sequences included do not allow us to conclude about their relationships.

Finally, Breslin et al. (2021) proposed and to be a single genus, as traditionally treated by North American botanists (Benson 1982; Zimmerman and Parfitt 2004). However, sampling in Mexican was not representative. Molecular and combined analyses recovered and as independent lineages and the ancestral state reconstruction (Appendix 3: Fig. A1) showed that each genus has a unique combination of morphological characters. Our results support the traditional recognition of and as separate genera (Taylor 1979; Bravo-Hollis and Sánchez Mejorada 1991; Dicht and Lüthy 2005; Hunt et al. 2006; Korotkova et al. 2021).

 clade

The eight sampled species of , together with , , and form a monophyletic group with high support values (Figs 1, 2). This clade is diagnosed by the tubercles with complete grooves, external tepals with fimbriate margins, and seeds with pitted multicellular sculpture on the lateral side (except in , and ) (Appendix 3: Fig. A1, Fig. 3).

Figure 3.

Representative species and morphology of and A bearing red fruits (S. Arias 2090, MEXU) B flower of (Quehl) Borg with fimbriate outer tepals (D. Aquino 322, MEXU) C bearing flowers with fimbriate outer tepals (S. Arias 1788, MEXU) D close-up of the furrow on the tubercles (arrow) in (H. Sánchez-Mejorada 3616, MEXU) E green fruits (top) and flat multicellular sculpture of the lateral side of the seed (bottom) in (B. Vázquez 2555, MEXU) F (D. Aquino 400, MEXU) G (SA 2212, MEXU) H (B. Vázquez 2625, MEXU) I (S. Arias 2109, MEXU) J (B. Vázquez 2618, MEXU) K glands at the axil (arrow) in (D. Sánchez s.n., IBUG) L (S. Arias 2129, MEXU).

Although previous molecular analyses recovered outside the core clade, phylogenetic relationships of were not clear due to lack of resolution (Bárcenas et al. 2011) and insufficient sampling of (Vázquez-Sánchez et al. 2013; Crozier 2005). Our analyses, including 46 taxa of , recovered two different samples of in the clade (PP = 1.0, Figs 1, 2), contrasting with the traditional classification in the monotypic (Backeberg) Moran, or Backeb. (sensu Dicht and Lüthy 2005). Previous morphological analysis of concluded that was the most dissimilar taxon of the genus (Vázquez-Benítez et al. 2016). The main character that differentiates this species from the rest of the species in the clade is the presence of an incomplete groove in the tubercles and fimbriate outer tepals.

shares the fimbriate outer tepals with the other species of the genus (Fig. 3B, C). Interestingly, and show identical flower morphology (Zimmerman and Parfitt 2004). Additionally, shows a shallowly pitted lateral seed coat (Barthlott and Hunt 2000, plate 73.3–4), similar to the flat cells observed in . Probably, the flat sculpture of the lateral side of the seed in is the result of the same development observed in . As observed in (Taylor and Clark 1983) the change of pitted to flat relief of periclinal walls of the seed testa has evolved independently in several lineages of the tribe Cacteae (Appendix 3: Fig. A1H). Given our results, we propose the recognition of as a member within the new rearrangement of and described in the following paragraphs (see Taxonomic summary).

As in previous analysis our phylogenetic hypothesis recovered the two species of in the clade (Butterworth and Wallace 2004; Bárcenas et al. 2011; Vázquez-Sánchez et al. 2013). Traditionally, is recognized (Boke 1959; Anderson and Boke 1969) by the presence of a rudimentary groove on the tubercles and the “reticulate or striate” seed structure (“par-concave” sensu Barthlott and Hunt 2000). However, also falls into Taylor’s (1979) concept of , which is circumscribed by seeds with intracellular pits (par-concave) and grooved tubercles. Following Boke (1959), the rudimentary groove in (Fig. 3D) is morphologically equivalent to the groove found on the tubercles of and . Regarding seed morphology, the pitted appearance of the seed coat in happens because only the central portion of the outer wall of the testa cell is thinner and collapses, while in the entire outer wall of the testa cell is thin and collapses (Barthlott and Hunt 2000). Therefore, and show a pitted lateral seed coat, differing in cell shape and pit diameter.

Finally, the margin of the outer tepals in may be entire or fimbriate, while in is always fimbriate (Anderson and Boke 1969); this character is also observed in all species of (Zimmerman and Parfitt 2004; Hunt et al. 2006). We hypothesized that represents a derived lineage in that has changed radically its growth form and the shape of its tubercules to occupy specific niches in the Sierra Madre Oriental. A similar trend is observed in species of the genus (Backeb.) Buxb. & Backeb., in which some species have evolved into a globose-depressed growth form with cylindrical and flattened distally (hatchet-shaped) tubercles (e.g., (Backeb.) Glass & R.A.Foster) or pyramidal and dorsiventrally flattened (scale-like) tubercles (e.g., (Boed.) Buxb. & Backeb.) (Vázquez-Sánchez et al. 2019).

Several studies recovered with high support the alliance of and a clade including , the type species of . A diagnostic character of and is the outerperianth-segments with ciliated margins as shown in (Fig. 3B), Řepka & Vaško (Řepka and Vaško 2011) and Britton & Rose (Benson 1982) not included in this analysis. The genus was published in 1843 by Ehrenberg, while was published 80 years later, in 1923, by Britton and Rose. In this context, we propose to merge members, including into (see Taxonomic summary) following priority of publication as dictated by the principle III of the International Code of Nomenclature for algae, fungi, and plants (Turland et al. 2018).

can be recognized as a natural group by excluding . s.s. (henceforth ) conformed a robust clade (PP = 1, Figs 1, 2) and can be diagnosed by tubercles with a complete groove, flowers with apical origin, outer tepals with entire margin, green fruits, and seed with flat multicellular sculpture on the lateral side (Appendix 3: Fig. A1, Fig. 3).

Although subgenera and recognized by Dicht and Lüthy (2005) are partially recovered, our phylogenetic analyses showed that most of the infrageneric sections and series proposed by these authors do not represent natural entities. All sampled members of were recovered in clade I, including taxa without turgid glands near the axil throughout the year (Appendix 3: Fig. A1C). However, this clade also included two of the species assigned to section Dicht & A. Lüthy in the (Table 3), making (sensu Dicht and Lüthy 2005) a paraphyletic group. Clade II grouped all the members of the subgenus , but the members of the sections and (Fig. 1) were recovered in the clade and the clade I, respectively. Therefore, (sensu Dicht and Lüthy 2005) represents a polyphyletic group. All members of clade II show turgid glands at or near the axil throughout the year (Fig. 3K), which is recognized as a consistent diagnostic feature and a potential synapomorphy for this lineage (Appendix 3: Fig. A1C).

Table 3.

Species memberships of the main clades obtained in this study and their previous infrageneric classification by Dicht and Lüthy (2005).

Clade I	subgenusCoryphantha and subgenus NeocoryphanthasectionRobustispina
Subclade A	Series Retusae: Coryphanthaelephantidens complex and C.retusa.
Subclade A	Series Pycnacanthae: C.pycnacantha and C.tripugionacantha
Subclade A	Series Salinenses (in part): C.pallida complex
Subclade B	Series Coryphantha (in part): Coryphanthahintoniorum and C.maiz-tablasensis
Subclade B	Series Corniferae (in part): C.compacta, C.cornifera, C.delaetiana, C.delicata, C.echinusC.neglecta, C.nickelsiae, C.pseudoechinus, C.pseudonickelsiae, C.ramillosa, and C.recurvatasubsp.canatlanensis
Subclade C	Series Salinenses (in part): Coryphanthadurangensis, C.durangensissubsp.cuencamensis, and C.longicornis
Subclade D	sectionRobustispina: Coryphanthaposelgeriana and C.robustispina
Subclade E	Series Coryphanta (in part): C.sulcate
Subclade E	Series Salinenses (in part): C.difficilis, C.kracikii, and C.salinensis
Subclade E	Series Corniferae (in part): C.werdermannii and C.echinus
Clade II	Subgenus Neocoryphantha except sectionRobustispina
Subclade F	Series Clavatae: C.octacantha, C.jalpanensis, C.clavata, C.clavata, C.glassii, C.erecta, and C.potosiana
Subclade F	Series Ottonis: C.ottonis, C.vogtherriana, and C.georgii
Subclade G	Series Echinoideae: C.wohlschlageri, C.vaupeliana, C.glanduligera, and C.echinoidea

In order to reflect the relationships found in our phylogenetic hypothesis and to provide a natural infrageneric classification of the genus, we re-circumscribe the two subgenera in . One for clade I, the , and another one for clade II, the (see Taxonomic summary). We further propose to recognize the recovered subclades as sections (see Taxonomic summary). The species belonging to each section, their morphological similarities, and their distribution (biogeographic provinces) are discussed below.

(clade I) emerged in five subclades that partially represent some taxonomic groups proposed by Dicht and Lüthy (2005). However, series and subseries suggested by these authors do not represent monophyletic groups. Clade A included species from series Dicht & A. Lüthy, Dicht & A. Lüthy and Dicht & Lüthy (Table 3). In this case, members of clade A present most of the radial spines with subulate shape (Fig. 3F) (Bravo-Hollis and Sánchez-Mejorada 1991; Dicht and Lüthy 2005). Our results found that the species complexes and do not represent monophyletic groups. This result corroborates that and are different species from as proposed by Vázquez-Benítez et al. (2016). Additionally, our results support the proposal of Arias et al. (2012) to recognize and as two distinct species. The distinction of Bravo from Britton & Rose, remains unresolved, since the former was not included in our analysis.

As documented by Dicht and Lüthy (2005), there was a historical confusion between and , since they are morphologically similar (Arias et al. 2012). This affinity is now justified since they belong to the same clade. Dicht and Lüthy (2005) classified within series along with northern species. This species emerged in Clade A, which is recognized here as (see Taxonomic summary). This is distributed in central Mexico, encompassing the southern portion of the piedmont of Sierra Madre Occidental, the Mexican High Plateau, the plains and piedmonts of the Mexican Transvolcanic Belt, the southern portion of Sierra Madre Oriental, and the Balsas Basin.

Clade B included members of the series and Dicht & A. Lüthy (Table 3). Members of this clade show upright or radiate tubercles (Fig. 3G). This lineage is recognized in the present work as the . This clade presents a wide distribution and occupies several northern ecoregions. An eastern group of species inhabits the Chihuahuan Desert, the Sierra Madre Oriental, and the Tamaulipas-Texas Semiarid Plain, and a western group occupies the Chihuahuan Desert, the piedmont of the Sierra Madre Occidental, and the Sierra Madre Occidental.

is classified into the monotypic Dicht & Lüthy by the presence of globose seed and broad basal hylum (Dicht and Lüthy 2005). Although was not included in our analysis, we suggest that it belongs to clade B, because of its morphological affinity to and (Vázquez-Benítez et al. 2016), and also the similar geographic distribution. (Backeb.) Glass was not included in our analysis. Dicht and Lüthy (2005) mention some morphological affinities to . In addition, and shared the presence of glands in the spiniferous areole. For now, we propose as a member of this group because of its morphological and geographical congruence to other species of this clade (Dicht and Lüthy 2005).

Subclade C included two members of the series (Table 3). These taxa can be distinguished by the presence of appressed tubercles and woolly stem tips (Fig. 3H) (Bravo-Hollis and Sánchez-Mejorada 1991; Dicht and Lüthy 2005). Our study included and , which formed a monophyletic group. However, they showed different branch lengths, which suggests that its recognition as different species, as proposed by Vázquez-Benítez et al. (2016), must be considered. This small group is recognized in the present work as the (see Taxonomic summary). This group presents a narrow distribution in the state of Durango, inhabiting the Chihuahuan Desert and the piedmont of the Sierra Madre Occidental.

Subclade D corresponds to (Table 3, Taxonomic summary). This clade is supported by the presence of turgid glands near the axil only during the flowering season (Fig. 3I; Appendix 3: Fig. A1C). Although those species have been grouped in the past with other taxa with glands (Dicht and Lüthy 2005; Vázquez-Benítez et al. 2016), our results suggested that this character state emerged independently from an ancestral with absent glands. This species occurs in the Chihuahuan Desert and in the northern piedmont of the Sierra Madre Occidental.

Subclade E was formed by six taxa classified into the series , series , and series (Table 3). There are no evident morphological characters that define clade C. Affinities such as the red filaments have been observed in , , , and . Particularly, and share a yellow flower with a brilliant red flower throat (Dicht and Lüthy 2005). Also, , , show tubercles appressed, and slightly appressed in (Fig. 3J). Members of subclade E are proposed here as the , which is distributed in the Chihuahuan Desert, the Sierra Madre Oriental, and the Tamaulipas-Texas Semiarid Plain.

We propose the division of (clade II) into two sections. The first one is (see Taxonomic summary), which corresponds to subclade F (Table 3). This section presents mucilaginous cortex (Dicht and Lüthy 2005), a character recovered as ancestral to the group in our analyses (Fig. 3K, Appendix 3: Fig. A1G). occurs mainly in the southern part of the Chihuahuan Desert and in the Mexican High Plateau, with ranging to the interior plains and piedmonts of the Sierra Madre Occidental and the Mexican Transvolcanic Belt. The second is , which corresponds to subclade G (Fig. 3L, Table 3). This section can be recognized by the presence of watery cortex (Appendix 3: Fig. A1G). Members of the section are distributed in the Chihuahuan Desert and the Sierra Madre Oriental.

Taxonomic summary



Phylogenetic analyses support the addition of within . Three lectotypes are proposed.

(K.Brandegee) Walton. Cact. J. (London) 2: 50. 1899.

(K.Schum.) D.Aquino & Dan.Sanchez comb. nov.

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Phylogenetic evidence supports the transference of to (see discussion) which results in 25 new combinations. Also, nine lectotypes, and three isolectotypes are proposed. Twenty species and 14 subspecies of , are recognized.

Ehrenb., Bot. Zeitung (Berlin) 1: 737. 1843.

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Type.

Ehrenb.

(Řepka & Vaško) D.Aquino & Dan.Sánchez comb. nov.

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(Pérez-Badillo, Delladdio & Raya-Sánchez) D.Aquino & Dan.Sánchez comb. nov.

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(J.M.Coult.) D.Aquino & Dan.Sánchez comb. nov.

urn:lsid:ipni.org:names:77248943-1

≡

Ehrenb., Bot. Zeitung 1: 737. 1843.

=

(Britton & Rose) D.Aquino & Dan.Sánchez comb. nov.

urn:lsid:ipni.org:names:77248944-1

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=

=

(Glass & R.A.Foster) D.Aquino & Dan.Sánchez comb. nov.

urn:lsid:ipni.org:names:77248945-1

≡

(Britton & Rose) D.Aquino & Dan.Sánchez comb. nov.

urn:lsid:ipni.org:names:77248946-1

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(Engelm.) D.Aquino & Dan.Sánchez comb. nov.

urn:lsid:ipni.org:names:77248947-1

≡

=

(Britton & Rose) D.Aquino & Dan.Sánchez comb. nov.

urn:lsid:ipni.org:names:77248948-1

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=

=

(Hester) D.Aquino & Dan.Sánchez comb. nov.

urn:lsid:ipni.org:names:77248949-1

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(Quehl) D.Aquino & Dan.Sánchez comb. nov.

urn:lsid:ipni.org:names:77248950-1

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=

=

=

=

(Y.Wright) D.Aquino & Dan.Sánchez comb. nov.

urn:lsid:ipni.org:names:77248951-1

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(Kaplan, Kunte & Snicer) D.Aquino & Dan.Sánchez comb. nov.

urn:lsid:ipni.org:names:77248952-1

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(Glass & R.A.Foster) D.Aquino & Dan.Sánchez comb. nov.

urn:lsid:ipni.org:names:77248953-1

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(Britton & Rose) D.Aquino & Dan.Sánchez comb. nov.

urn:lsid:ipni.org:names:77248954-1

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(Engelm.) D. Aquino & Dan.Sánchez comb. nov.

urn:lsid:ipni.org:names:77248955-1

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=

(Britton & Rose) D.Aquino & Dan.Sánchez comb. nov.

urn:lsid:ipni.org:names:77248956-1

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=

(Baird) D.Aquino & Dan.Sánchez comb. nov.

urn:lsid:ipni.org:names:77248957-1

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=

(Sweet) D.Aquino & Dan.Sánchez comb. nov.

urn:lsid:ipni.org:names:77248958-1

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=

=

=

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=

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(Boed.) D.Aquino & Dan.Sánchez comb. nov.

urn:lsid:ipni.org:names:77248959-1

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(W.H.Earle) D.Aquino & Dan.Sánchez comb. nov.

urn:lsid:ipni.org:names:77248960-1

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(Britton & Rose) D.Aquino & Dan.Sánchez comb. nov.

urn:lsid:ipni.org:names:77248961-1

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=

=

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(Boed.) D.Aquino & Dan.Sánchez comb. nov.

urn:lsid:ipni.org:names:77248962-1

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=

=

=

=

=

=

(Werderm.) Fric. & Schelle, Verzeichniss 9, 1935.

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(Engelm.) D.Aquino & Dan.Sánchez comb. nov.

urn:lsid:ipni.org:names:77248963-1

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=

=

=

=

=

=

(Nutt.) D.Aquino & Dan.Sánchez comb. nov.

urn:lsid:ipni.org:names:77248964-1

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=

=

=

=

=

=

=

=

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(Boed.) D.Aquino & Dan.Sánchez comb. nov.

urn:lsid:ipni.org:names:77248965-1

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=

Phylogenetic analyses obtained here support the recognition of two subgenera in (clade C1 and clade C2), which are composed by two section (subclade A and subclade B) and five sections (subclades C to G), respectively. Also, 46 species and 12 subspecies of , are recognized. Asterisk (*) indicates species that were not included in the phylogenetic analyses. A taxonomic synthesis is presented.

(Engelm.) Lem., Cactées 32. 1868.

Engelm., Proc. Amer. Acad. Arts 3: 264. 1856.

Salm-Dyck, Cact. Hort. Dyck. 1844: 13. 1845.

Doweld, Sukkulenty 3: 17. 2000. Type:

(Engelm.) Britton & Rose

(Dicht & A.Lüthy) Dan.Sánchez & D.Aquino stat. nov.

urn:lsid:ipni.org:names:77248966-1

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Dicht & A.Lüthy, Cactaceae Syst. Init. 11: 21, 2001.

Bremer & A.B.Lau, Cact. Succ. J. (Los Angeles) 49: 72. 1977.

Dicht & A.Lüthy, Cactaceae Syst. Init. 11: 20. 2001.

(Quehl) A.Berger, Kakteen: 270, 339. 1929.

Dicht & A.Lüthy, Cactaceae Syst. Init. 11: 20. 2001.

L.Bremer, Cact. Suc. Mex. 24: 3. 1979.

Species included

(*inserta sedis). (Engelm.) Orcutt, (DC.) Lem., (Quehl) A.Berger, L.Bremer, * L. Bremer & A.B.Lau, Dicht & A.Lüthy, Dicht & A.Lüthy, Backeb., L.Bremer, (K.Brandegee) Britton & Rose, Boed., Backeb., * (Backeb.) Glass, Cutak, Dicht & A.Lüthy (Engelm.) Britton & Rose and Dicht & A.Lüthy.

Dicht & A.Lüthy,

(Engelm.) Britton & Rose, 4: 48. 1923.

Species included.

(Quehl) Orcutt, (Engelm.) Britton & Rose, Halda, Chalupa & Kupčák, (Poselg.) Dicht & A.Lüthy, (Engelm.) Britton & Rose, and Boed.

Dan.Sánchez & D.Aquino sect. nov.

urn:lsid:ipni.org:names:77248967-1

Britton & Rose, (Britton & Rose) 4: 42. 1923.

(Runge ex K.Schum.) Britton & Rose, (L.Bremer) Dicht & A.Lüthy, and Boed.

(Dicht & A.Lüthy) Dan.Sánchez & D.Aquino stat. nov.

urn:lsid:ipni.org:names:77248968-1

Dicht & A.Lüthy,

Basionym.

Dicht & A.Lüthy, Syst. Init. 11: 15. 2001.

(Mart.) Lem., Cactées: 35. 1868.

(*inserta sedis): (C.Ehrenb.) Britton & Rose, Bravo ex S.Arias, U.Guzmán & S.Gama, (Lem.) Lem., Bravo, Britton & Rose, * Bravo, (Mart.) Lem., (Pfeiff.) Britton & Rose, and A.B. Lau.

Dicht & A.Lüthy, Cactaceae Syst. Init. 11: 9. 2001.

(Ant.Schott ex Engelm.) Britton & Rose, 4: 33. 1923.

(Ant.Schott ex Engelm.) Britton & Rose, (Lem.) N.P. Taylor, and (A.Dietr.) Britton & Rose.

Backeb. ex Dicht & A. Lüthy, Cactaceae Syst. Init. 11: 8, 2001.

(Scheidw.) Backeb., Jahrb. Deutsch. Kakt. Ges. 1941: 61. 1942.

(Dicht & A. Lüthy) Dan.Sánchez & D.Aquino stat. nov.

urn:lsid:ipni.org:names:77248969-1

≡

Dicht & A.Lüthy,

(Scheidw.) Backeb., (Scheidw.) Dicht & A.Lüthy, (Lem.) Lem., Boed., Dicht & A.Lüthy, Buchenau, (DC.) Britton & Rose, (Pfeiff.) Lem., (Jacobi) Glass & R.A.Foster, and Werderm. & Boed.

(Dicht & A. Lüthy) Dan.Sánchez & D.Aquino stat. nov.

urn:lsid:ipni.org:names:77248971-1

≡

(Quehl) Britton & Rose, (Otto & A.Dietr.) Lem., Boed., and Holzeis.

New neotypes and lectotypes

Furthermore, two neotypes and three lectotypes are proposed. For a more extensive review of the accepted names in , see Dicht and Lüthy (2005).

(Jacobi) Glass & R.A.Foster, Cact. Succ. J. (Los Angeles) 43: 7. 1971.

≡

(Pfeiff.) Lem., Cactées: 34. 1868.

≡

=

=

=

=

=

Table A1.

Insertion-deletion events coded in the alignment for each sequence. Deletion=DEL, insertion=INS, simple sequence repetition (SSR).

Sequence	Event	Sites	Sequence	Event	Sites
matk	INS	675-677	rpl16	DEL	939-957
psbA-trnH	DEL	96-109	rpl16	INS	1079-1082
psbA-trnH	Del	110-154	rpl16	SSR	1148-1150
psbA-trnH	Del	127-138	trnL-F	INS	365-385
psbA-trnH	Del	132-138	trnL-F	DEL	390-609
psbA-trnH	Del	170-179	trnL-F	DEL	345-592
psbA-trnH	INS	383-389	trnL-F	INS	438-442
psbA-trnH	SSR	214-217	trnL-F	DEL	453-521
psbA-trnH	INS	222	trnL-F	SSR	483-484
psbA-trnH	DEL	272-364	trnL-F	SSR	540-553
psbA-trnH	INS	343	trnL-F	DEL	848-855
psbA-trnH	DEL	362-371	trnL-F	Del	853-890
rpl16	DEL	30-44	trnL-F	DEL	871-1117
rpl16	DEL	210-213	trnL-F	INS	894-897
rpl16	DEL	278-280	trnL-F	DEL	1049-1057
rpl16	INS	550-567	trnL-F	SSR	1151-1152
rpl16	SSR	733-738	trnL-F	SSR	1205-1209