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Echeveria kristenii is described as a new species from Sierra Azul, Mezquital, Durango. The new species belongs to a sub-group of northwestern Mexican taxa within ser. Gibbiflorae. Within the series it is most similar to E. dactylifera and E. novogaliciana in its acaulescent habit, sessile, farinaceous and somewhat narrowed leaves, paniculate inflorescences with short cincinni, and the presence of finger-like appendages at the base of the epipetalous filaments. Characters that distinguish it from those species include the size of the rosette, the shape, color, and size of the leaves, and the color of the styles and nectary scales. Additionally, three diagnostic nucleotide characters were found in rbcL, matK and ITS2, three standard DNA barcoding regions, that differentiate the new species not only from its closest relatives, but from all other taxa of ser. Gibbiflorae.

Echeveria islasiae is proposed as new species, a plant collected near the town of Olinala in the state of Guerrero, Mexico. Its morphological characteristics such as few-flowered cincinnate inflorescences and an elongate corolla with greenish apex relate it with the taxa of ser. Longistylae. Conversely, it differs from the other taxa of the series by having narrower, dark green, oblanceolate-spatulate to cymbiform leaves that are somewhat triquetrous at the apex, deep red floral peduncles and pedicels, the corolla pink colored at the middle, and the absence of appendages at the sides of the epipetalous filaments. A first effort to build a reference library for DNA barcoding shows two diagnostic nucleotides which differentiate the new species from related taxa, one in the matK chloroplast region and one in the ITS2 nuclear region.

Background A puzzle in evolution is the understanding of how the environment might drive subtle phenotypic variation, and whether this variation is adaptive. Under the neutral evolutionary theory, subtle phenotypes are almost neutral with little adaptive value. To test this idea, we studied the infraspecific variation in flower shape and color in Mammillaria haageana, a species with a wide geographical distribution and phenotypic variation, which populations are often recognized as infraspecific taxa. Results We collected samples from wild populations, kept them in the greenhouse for at least one reproductive year, and collected newly formed flowers. Our first objective was to characterize tepal natural variation in M. haageana through geometric morphometric and multivariate pigmentation analyses. We used landmark-based morphometrics to quantify the trends of shape variation and tepal color-patterns in 20 M. haageana accessions, belonging to five subspecies, plus 8 M. albilanata accessions for comparison as the sister species. We obtained eight geometric morphometric traits for tepal shape and color-patterns. We found broad variation in these traits between accessions belonging to the same subspecies, without taxonomic congruence with those infraspecific units. Also the phenetic cluster analysis showed different grouping patterns among accessions. When we correlated these phenotypes to the environment, we also found that solar radiation might explain the variation in tepal shape and color, suggesting that subtle variation in flower phenotypes might be adaptive. Finally we present anatomical sections in M. haageana subsp. san-angelensis to propose some of the underlying tepal structural features that may give rise to tepal variation. Conclusions Our geometric morphometric approach of flower shape and color allowed us to identify the main trends of variation in each accession and putative subspecies, but also allowed us to correlate these variation to the environment, and propose anatomical mechanisms underlying this diversity of flower phenotypes.

Genetic mechanisms controlling root development are well-understood in plant model species, and emerging frontier research is currently dissecting how some of these mechanisms control root development in cacti. Here we show the patterns of root architecture development in a gradient of divergent lineages, from populations to species in Mammillaria. First, we show the patterns of variation in natural variants of the species Mammillaria haageana. Then we compare this variation to closely related species within the Series Supertexta in Mammillaria (diverging for the last 2.1 million years) in which M. haageana is inserted. Finally, we compared these patterns of variation to what is found in a set of Mammillaria species belonging to different Series (diverging for the last 8 million years). When plants were grown in controlled environments, we found that the variation in root architecture observed at the intra-specific level, partially recapitulates the variation observed at the inter-specific level. These phenotypic outcomes at different evolutionary time-scales can be interpreted as macroevolution being the cumulative outcome of microevolutionary phenotypic divergence, such as the one observed in Mammillaria accessions and species.

Genetic mechanisms controlling root development are well-understood in plant model species, and emerging frontier research is currently dissecting how some of these mechanisms control root development in cacti. Here we show the patterns of root architecture development in a gradient of divergent lineages, from populations to species in Mammillaria. First, we show the patterns of variation in natural variants of the species Mammillaria haageana. Then we compare this variation to closely related species within the Series Supertexta in Mammillaria (diverging for the last 2.1 million years) in which M. haageana is inserted. Finally, we compared these patterns of variation to what is found in a set of Mammillaria species belonging to different Series (diverging for the last 8 million years). When plants were grown in controlled environments, we found that the variation in root architecture observed at the intra-specific level, partially recapitulates the variation observed at the inter-specific level. These phenotypic outcomes at different evolutionary time-scales can be interpreted as macroevolution being the cumulative outcome of microevolutionary phenotypic divergence, such as the one observed in Mammillaria accessions and species.

Mexico is considered as diversification and endemism center of the genus Echeveria. Previous tree inference studies have shown the genus to be non-monophyletic in relation to other genera, but sampling for Echeveria has been poor, and has not allowed to understand the relationships within the genus. In this work, Bayesian and maximum likelihood phylogenetic analysis were performed, using a combined standard DNA barcoding loci matrix (rbcL, matK and ITS2) and GenBank ITS2 accessions for Graptopetalum, some Sedum and few Echeveria taxa. The selection of taxa encompasses all current infrageneric categories of the genus Echeveria, as well as species from genera previously associated with it. The inferred consensus trees suggested that Echeveria is paraphyletic. Instead, four main clades were retrieved within the “Echeveria group”: Clade I includes exclusively Pachyphytum species. Clade II is formed by the majority of series Urbiniae; Clade III encompasses series Chloranthae, Ciliatae, Echeveria, Mucronatae, Nudae, Racemosae, Thyrsiflorae, Pachyphytum cuicatecananum and Thompsonella; Clade IV contains series Angulatae, Gibbiflorae, Occidentales, Pruinosae, Secundae, some Urbiniae species, Valvatae. genera Cremnophila, Graptopetalum and Reidmorania. Pachyphytum and Thompsonella were retrieved as monophyletic groups, but the first outside Echeveria while the latter inside. Results of our study suggest that Echeveria and the Echeveria Group require a redefinition.

Background. Distinguishing species and populations in Crassulaceae is challenging because of the morphological variability and inter-specific hybridization. Currently our understanding of the morphological and anatomical features in Echeveria is poor, and therefore it is difficult to delimit species, and morphotypes within the species. Question. Our objective was to describe the foliar anatomy and the shape of accessions in E. gigantea. We used E. gibbiflora , another species in the series as a comparison group. Comparing the two species allowed us to evaluate the relationship between anatomy and morphology in E. gigantea . Methods. We performed a survey of anatomical features in seven accessions of E. gigantea , and one accession of E. gibbiflora . We obtained epidermal prints, leaf sections, performed geometric and morphometric analyses. Results. We found that 65 % of the anatomical traits are heterogeneous among the taxonomic units. Our analysis showed that E. gibbiflora and some E. gigantea accessions share extensive anatomical similarities. There was variation within the E. gigantea , suggesting that at least one of the accessions is an independent taxonomic group. The traits with the largest contribution to variation between the groups were related to the epidermis, the hypodermis, the type of vascular bundles and the collenchyma associated to the vascular bundles. In addition we quantified the variation in leaf shape. Interestingly, we found correlations between the organ shape and anatomical traits. Conclusion. These analyses provide information about traits towards the morpho-anatomical definition of E. gigantea variation and suggest developmental correlation yet to be explained.

Echeveria michihuacana (Crassulaceae), a new species for science, is described and illustrated. The new taxon is related to a group of species of Echeveria series Gibbiflorae from western Mexico, including Echeveria dactylifera, Echeveria fulgens, Echeveria patriotica, and particularly the recently published Echeveria pistioides. With the last species, E. michihuacana is similar in the shape and coloration of floral structures, as well as in its geographical distribution. In contrast, it differs from all of the aforementioned related species in having an evident stem, larger panicles and flowers, deep-red nectary scales, and absence of appendages on the inner side of the petals.

Pachyphytum viscidum (Crassulaceae: Saxifragales) is described as a new species to science. The specimens analyzed come from the Sierra de Santa Barbara, Guanajuato, Mexico. Some morphological diagnostic characters for the new species are: sticky stems and leaves; dark green leaves; absence of wax on all their organs; and pale pink flowers. The new species is placed in the section Diotostemon of the genus, with possible proximity to P. brevifolium and P. hookeri. DNA sequence analysis from the matK and rbcL chloroplast regions, as well as ITS2 nuclear loci, revealed the presence of molecular diagnostic sites which, in addition to the aforementioned morphological character states, further support the taxonomic description as well as future integrative taxonomy studies in Mexican Crassulaceae.

Sedum piaxtlaense is described as a new species based on a collection in the Rio Piaxtla Canyon, growing in tropical deciduous forest in the Sierra Madre Occidental near the border of the Mexican states of Durango and Sinaloa. This new species belongs into the section Sedastrum (Rose) A. Berger whose distinctive morphological characteristics are basal rosettes, generally pubescent leaves, concave carpel base, usually paniculate inflorescences, and white corollas, the only exceptions being Sedum glabrum and S. jarocho which do not show any pubescence in their floral structures. S. piaxtlaense is apparently closely related to S. hintonii and S. mocinianum from which it differs in the laxer rosettes, concave leaves of larger diameter, as well as a shorter inflorescence with up to eight flowers per cincinnus and large pedicels, and its distribution in another biogeographical province.

Echeveria xochipalensis, from the state of Guerrero, Mexico, is described as a new species to science. It is related to species of ser. Gibbiflorae, particularly to both E. fulgens varieties, from which it is distinguished by its green to lilac-gray spatulate leaves, although they commonly are coppery tinged; the leaves are rigid and with entire margin (not crenate), the margin is yellow-hyaline; bracts oblanceolate with rigid consistency; corolla pink at base and orange at the apex and whitish filaments, ovaries and nectary scales.

Dahlia mixtecana (Asteraceae, Coreopsideae) is described and illustrated as a new species endemic to western Oaxaca, Mexico. This taxon is related to Dahlia sect. Dahlia and Dahlia sect. Entemophyllon . However, based on the current evidence available and the current system of infrageneric groups, it does not appear possible to assign the new species with confidence to any taxonomic section. The description of the new species is presented with distribution maps, illustrations, photographs, discussions on the taxonomic relationship and an identification key to the sections and species of Dahlia occurring in Oaxaca and species in Dahlia sect. Entemophyllon related to D. mixtecana .

Echeveria Juliana is described as a new species based on collections in the Rio Piaxtla Canyon, in the Sierra Madre Occidental near the border between the Mexican states of Sinaloa and Durango. This species appears to be related to E. tobarensis from Durango. It differs in the size of the rosette, its pale pink color, shape and pruinosity, as well as corolla size, color of the carpels, and its obovate leaves. The new species grows at an uncommonly low altitude of 360 m (1080 ft) in tropical deciduous forest. It belongs into the series Urbiniae as it lacks an evident stem or tuberous roots, and by the possession of a secund inflorescence and a long urceolate corolla.

Sedum kristenii Reyes, Gonzalez-Zorzano & Etter is described as a new species from the Mexican state of Durango. It belongs in the group Americana of the section Sedum and is related to Sedum lumholtzii, Sedum copalense and Sedum bellum, from which it differs in roots, nectary color, and the size of stems and leaves.

Dahlia tamaulipana (Asteraceae, Coreopsideae) a new species from Sierra Madre Oriental in Tamaulipas, Mexico, is described. The new species is morphologically similar to D. tubulata, but differs by developing stems evidently hexagonal and villous in the upper portion of the nodes and the base of the petioles, the internodes reach 3–5.5 × 1–1.5 cm, the stipels are present from the first to the third pair of leaflets, the synflorescence develops (1–)15–25 heads, the heads reach 6.5–10 cm wide across the extended rays, and clavate cypsela with crown-shaped pappus. Both species inhabit the northern portion of the Sierra Madre Oriental, however they are not sympatric and do not share ecological preferences and phenological behavior. The description of the new species is accompanied with photographs, a chromosome count, and a distributions map and a key for Dahlia in Sierra Madre Oriental.

A new species, Sedum brachetii Reyes, Islas et Gonzalez-Zorzano, is described from Guerrero, Mexico. Placed within the section Pachysedum, S. brachetii differs from its closest comparable relatives S. clavatum, S. orbatum, S. cuspidatum and S. ocuilense in stem size, leaf structure, inflorescence size and nectary color. Figures of the holotype are provided.

Hybridization represents an important mechanism in the diversification of Cactaceae where interspecific barriers are poorly developed. Putative hybrids with an intermediate phenotype between the columnar cacti Escontria chiotilla and Polaskia chichipe were observed in Oaxaca, Mexico. The putative hybrids grow sympatrically with their parents, sharing pollinators and overlapping flowering periods. On the basis of morphological, genetic and molecular studies, we show that a gene flow occurs between E. chiotilla and P. chichipe. Morphological and genetic similarities were used to carry out phenetic analyses, which allowed us to separate the two taxa and the potential hybrids, and cluster them into discrete groups with a high degree of consistency. We also generate artificial hybrids by hand-pollination crosses. These hybrids indicate that there are partial pre- and postzygotic barriers between E. chiotilla and P. chichipe. Backcrosses between parents and hybrids produced viable seeds, suggesting that there is a high potential of introgression with both parents. Taken together, we propose that hybrids observed in the field are the product of cross-pollination between E. chiotilla and P. chichipe. Thus, gene flow between both genera can explain why the genetic independence of these taxa has not kept them reproductively isolated. A complete description and illustrations of a new intergeneric hybrid are provided.

La Mixteca Alta es una región montañosa, ubicada al NO del estado de Oaxaca y S de Puebla. La dominan principalmente bosques de Pinus y Quercus, diversos tipos de matorrales y pequeñas áreas con bosque tropical caducifolio y bosque mesófilo de montaña. En el inventario de su flora fanerogámica se reconocen hasta el momento 1550 taxa nativos, 163 (10.5%) de los cuales son endémicos. Noventa y siete de este total (59.5%) son exclusivos de la Mixteca Alta, 50 (30.7%) extienden su área de distribución hacia el centro del estado de Oaxaca y 16 más (9.8%) hacia Guerrero. Treinta y cuatro familias y 92 géneros presentan algún taxon endémico. El género Ainea (monotípico) es endémico a la Mixteca Alta, mientras que Fosteria, Gibasoides y Pseudocranichis rebasan un poco sus límites. Las formas de vida representadas en las especies endémicas corresponden a las plantas herbáceas (52%), suculentas (20%), arbustos (17%), trepadoras (4%), rastreras y epifitas (6%) y árboles (1%). Con el conocimiento actual de la flora se estima que aún quedan por localizarse entre 15 y 20% de las especies. En este trabajo se incluye la lista de los taxa endémicos, con datos sobre su distribución, sus formas de vida y los distritos políticos donde se concentran.