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Resumen: Los términos 'forma de crecimiento' y 'hábito' con frecuencia se usan como sinónimos; sin embargo, su asignación a las diferentes especies resulta problemática en algunos grupos taxonómicos debido a la diversidad morfológica; éste es el caso en Cactaceae, particularmente en la tribu Cacteae de la subfamilia Cactoideae. Se estudió la morfología del tallo de 102 especies (26 géneros) de Cacteae con el objetivo de identificar el hábito y reconocer cuántas formas de crecimiento se presentan en la tribu, así como para hacer una distinción clara entre los términos 'hábito' y 'forma de crecimiento' para Cactaceae y discutir sus diferencias respecto a los conceptos de forma de vida y arquitectura vegetal. Con base en las observaciones y mediciones para 102 especies de Cacteae se reconocieron cuatro formas de crecimiento (cilíndrica, columnar, globosa y globosa-deprimida). Por su tamaño y longevidad no es posible utilizar los términos 'árbol' o 'hierba' para las especies de Cacteae. El 12% de las especies estudiadas de esta tribu tienen ramificación basítona (arbustos) como Acharagma roseana, Ferocactus pilosus y Thelocactus bicolor. Sugerimos utilizar únicamente el término 'forma crecimiento' para referirse a los tallos de la tribu Cacteae con la finalidad de evitar confusiones. Palabras clave: arbusto, arquitectura vegetal, cilíndrica, columnar, forma de vida, globoso. Abstract:The terms 'growth form' and 'habit' are often used as synonyms. However, their assignment to different species is problematic because of the morphological diversity occurring in some taxonomic groups, as is the case in Cactaceae, particularly in the tribe Cacteae of the Cactoideae subfamily. Stem morphology was studied in 102 species (26 genera) of Cacteae in order to identify the habit and to recognize how many growth forms occur in the tribe, as well to make a distinction between the concepts of habit and growth form in Cactaceae, and to discuss the differences between them and the concepts of life form and plant architecture. Based on observations and measurements for 102 species of Cacteae, four growth forms (cylindrical, columnar, globose, and globose-depressed) were recognized. Neither the habit 'tree' or 'herb' can be assigned to any member of Cacteae based on their size or longevity. Twelve percent of the studied species of this tribe have basitonic branching (shrubs) as for Acharagma roseana, Ferocactus pilosus and Thelocactus bicolor. In order to avoid confusion, we suggest using only the term 'growth form' when referring to the various stem forms in the Cacteae tribe.

RESUMENCoryphantha tiene entre 43 y 67 especies. Los patrones de variación morfológica del género se han interpretado de distintas formas y han conducido a una taxonomía inestable, de manera que aún no se ha establecido un consenso en la delimitación de las especies. Clasificaciones previas de Coryphantha se han basado en caracteres cualitativos. Para dilucidar y circunscribir especies de Coryphantha se emplearon diferentes técnicas de análisis multivariado. Se muestrearon un total de 1840 individuos, 467 ejemplares en campo y 1373 registros herborizados de 48 taxa del género. Se emplearon 28 caracteres vegetativos y reproductivos de los cuales 17 fueron cuantitativos y 11 cualitativos. El análisis de conglomerados indicó la presencia de dos grandes grupos organizados por la presencia o ausencia de glándulas extraflorales. Los análisis discriminantes para cada subgrupo formado por los análisis de conglomerados permitieron circunscribir con base en variables morfométricas a la mayoría de las especies analizadas. Con base en los caracteres morfológicos y los análisis multivariados se discute el reconocimiento de categorías taxonómicas a nivel de especie o subespecie. Se reconocen 45 especies y tres subespecies.Palabras clave: análisis de conglomerados, análisis discriminante, Cactaceae, Coryphantha, taxonomía. ABSTRACTCoryphantha consists of 43 to 67 species. This genus exhibit patterns of morphological variations that have been understood differently and have led to an unstable

Seed morphology of 24 species of Stenocereus was examined by scanning electron microscopy. Quantitative and qualitative features were evaluated to identify groups of species using a phenetic analysis. Two groups were distinguished based on morphological variations of seed size, luster, multicellular sculpture, keeling, cell-size, periclinal wall sculpture, microrelief and HM complex shape and position relative to rim. All species studied were keeled, with isodiametric cells in the lateral region. Stenocereus alamosensis, S. kerberi and S. beneckei are unique among Stenocereus species in that their seeds are flat but lack micro-relief. Stenocereus aragonii and S. eichlamii have large, glossy seeds lacking micro-relief unlike other Stenocereus species, but like most Pachycereus, are unique in that cells in the lateral region display partly convex, low domes. Quantitative and qualitative congruence and discordance among characters that determine species groups in Stenocereus are discussed.

The process of hybridization occurs in approximately 40% of vascular plants, and this exchange of genetic material between non-conspecific individuals occurs unequally among plant lineages, being more frequent in certain groups such as Opuntia (Cactaceae). This genus is known for multiple taxonomic controversies due to widespread polyploidy and probable hybrid origin of several of its species. Southern Mexico species of this genus have been poorly studied despite their great diversity in regions such as the Tehuacán-Cuicatlán Valley which contains around 12% of recognized Mexico’s native Opuntia species. In this work, we focus on testing the hybrid status of two putative hybrids from this region, Opuntia tehuacana and Opuntia pilifera, and estimate if hybridization occurs among sampled southern opuntias using two newly identified nuclear intron markers to construct phylogenetic networks with HyDe and Dsuite and perform invariant analysis under the coalescent model with HyDe and Dsuite. For the test of hybrid origin in O. tehuacana, our results could not recover hybridization as proposed in the literature, but we found introgression into O. tehuacana individuals involving O. decumbens and O. huajuapensis. Regarding O. pilifera, we identified O. decumbens as probable parental species, supported by our analysis, which sustains the previous hybridization hypothesis between Nopalea and Basilares clades. Finally, we suggest new hybridization and introgression cases among southern Mexican species involving O. tehuantepecana and O. depressa as parental species of O. velutina and O. decumbens.