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Antecedentes y Objetivos: En Oaxaca, México, se reportan 26 especies del género Mammillaria; siete de ellas endémicas. Mammillaria deherdtiana subsp. dodsonii está catalogada como amenazada. Los objetivos del trabajo fueron describir las características demográficas, reproductivas y aspectos etnobotánicos de su uso, así como los aspectos florísticos y bioclimáticos de las localidades estudiadas. Métodos: En enero de 2015 se encontraron dos localidades de Mammillaria deherdtiana subsp. dodsonii en la Sierra Norte. Entre enero y marzo se ubicaron cinco transectos de 5 m2 en una de ellas, en los cuales se registró el número de individuos, se establecieron categorías de tamaño y se obtuvo la estructura poblacional. Para la marcha floral se eligieron diez flores y cada dos horas se registró el diámetro de la apertura del perianto. Se registraron las especies de plantas vasculares que crecían cerca de ella y se obtuvieron datos de las variables climáticas. Se entrevistó a los pobladores para documentar el conocimiento y uso que le dan a esta cactácea.Resultados clave: La estructura poblacional es multimodal. Los individuos juveniles conforman 65% y los adultos reproductivos 33% en la localidad estudiada. La antesis dura siete horas; se observó dicogamia y hercogamia, lo cual indica un sistema de cruza xenógamo. La subespecie es reconocida con nombres en español y zapoteco y es usada de manera ocasional como alimento, medicina y ornamento. Se registraron 15 especies pertenecientes al bosque de Pinus y Abies. Las preferencias ambientales de la subespecie son temperaturas de 9.6-12.7 °C y precipitación de 1009-1405 mm.Conclusiones: El sistema de cruza xenógamo resulta preocupante por la observación de un solo visitante floral. La presencia de cerdas y espinas radiales sugiere adaptaciones morfofisiológicas de esta subespecie al frío. Se sugiere profundizar en la presencia y efectividad de los polinizadores y en la dinámica de reclutamiento de la subespecie.

We studied populations of Stenocereus pruinosus throughout Mexico, a species important for its edible fruit. The Tehuacan Valley is setting of ancient and the currently most active management of S. pruinosus; we hypothesized Tehuacan as the original area of domestication of S. pruinosus and expected to find there its highest genetic variation and original source of genes of cultivated plants. Through nuclear microsatellite loci we studied spatial distribution of genetic variation and population differentiation. We sampled wild and managed populations of the Central-western (Tehuacan, Central Valleys and Tehuantepec, Oaxaca), north-eastern (Huasteca) and south-eastern (Chiapas) regions. Differences among regions and populations were compared through homogeneity and exact test for F IS , AMOVA, Bayesian analysis, and genetic barriers. A niche analysis allowed corroborating taxonomic identity of populations. The highest genetic diversity was in Tehuantepec (H E = 0.841), decreasing towards the extremes of distribution (H E = 0.242 in Huasteca, H E = 0.254 in Chiapas). Genetic structure is significantly high among populations and regional groups, differentiating one group formed by northern and southern populations and other formed by populations of the Central-western region. Differences among groups suggested that populations from Huasteca could be species different to S. pruinosus, but the niche analysis did not support such hypothesis. Populations from Tehuantepec were different but genetically interconnected with those of Tehuacan. Tehuantepec is the main reservoir of genetic diversity of wild populations of S. pruinosus, but Tehuacan is the principal current area of domestication of S. pruinosus and probably where its domestication originated. Conclusions would be stronger by analyzing DNAc lineages.

In order to increase our embryological knowledge of Pereskia, a genus considered the earliest member of Cactaceae, we followed the development of the flowers and seeds of Pereskia lychnidiflora, a species from southeastern Mexico. We compared our data with that available from other closely related members in the family. The embryological characterization showed that basic features are homogeneous across the family and supported the placement of P. lychnidiflora as a member of one of two Pereskia clades, the one sister to remaining cacti. Our data also supports the hypothesis that within the family Cactaceae, the evolutionary tendency is towards a reduction of the perisperm. A multilayered seed coat was observed in P. lychnidiflora. A novel finding was the presence of stomata along the basal and central part of the ovary, a character that has never been reported before in other members of Pereskia.