Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

Coryphantha consists of 43 to 67 species. This genus exhibit patterns of morphological variations that have been understood differently and have led to an unstable taxonomy, resulting in the fact that a consensus on the delimitation of species has yet to be reached. Previous classifications are based on qualitative characters. In order to clarify and circumscribe species of Coryphantha, different multivariate analysis techniques were used. A total of 1840 individuals among 48 taxa were examined; 467 in the field and 1373 from herbarium specimens. We used 28 vegetative and reproductive characters of which 17 were quantitative and 11 qualitative. Cluster analysis indicated the presence of two major groups based on the presence or absence of extrafloral glands. Discriminant analysis for each subgroup consisting of the cluster analysis allowed circumscription based on morphometric variables of the majority of the analyzed species. Based on morphological characters and multivariate analysis, recognition of taxonomic categories at species or subspecies level is discussed. 45 species and three subspecies are recognized.

Four species of hysterioid fungi belonging to the class Dothideomycetes of the phylum Ascomycota occurring in the tropical dry forest in the National Park of “Lagunas de Chacahua” in the state of Oaxaca are described and illustrated. Of these, Anteaglonium abbreviatum and Rhytidhysteron rufulum are new records for the state, Psiloglonium simulans is cited for the first time for Mexico and Gloniella tropicalis is described as a species new to science.

Piper sanctum, long treated as a distinct species, is here reduced to a synonym of P. auritum, which is a popularly known plant in Mexico. The oldest binomial for the species to which the name Piper sanctum was misapplied is P. commutatum, a taxon ranging from central Mexico south to Costa Rica and occurring in cloud forest, tropical perennial forest, tropical subdeciduous forest and humid canyons in tropical deciduous forest, at elevations from sea level to 2050 m. Synonyms of Piper commutatum include: P. papantlense, P. nudum, P. diandrum, P. membranaceum, and P. venulosum, among others.

Several national and foreign herbaria were reviewed to obtain the checklist of the family Poaceae of the state of Morelos, Mexico. The family is represented by 104 genera, 306 species and 10 infraspecific categories, classified in eight subfamilies with Chloridoideae, Panicoideae and Pooideae the most diverse ones. Morelos is repositioned from the 20th to the 13th most diverse state in Mexico with respect to species richness of the family. We present a brief analysis of the knowledge of the flora in this state by municipalities, as well as the collection effort that has been made throughout the years. Seven noxious weed species, which are listed in Mexican laws are recorded in the state.

The addition of Pisonia donnellsmithii Heimerl ex Standl. (Nyctaginaceae) to the flora of Guerrero state, Mexico, is presented. For the first time, it is possible to describe the pistillate flowers, the fruits, and the seeds. The description of the genus, an illustration of this taxon, as well as a key to the species of Pisonia in Mexico are also included.

Background and Aims: Habitat fragmentation and other human disturbances can cause loss of soil fertility, erosion, biodiversity, among others; however, available information in arid regions is limited. Our aim was to determine the effects of a disturbance gradient on species composition in two vegetation types in a semi-arid area of central Mexico.Methods: We selected six patches, three of shrubland and three of tropical dry forest, in the area of Cerro Colorado. We quantified the species and generic diversity of ten quadrats per patch (60 in total), placed randomly, during the months May-June 2011. We developed a disturbance index based on disturbances such as grazing and wood use among others. High, medium and low disturbance areas were identified in both tropical dry forest and shrubland.Key results: Results indicate that tropical dry forest is more diverse than shrubland. The shrubs Cnidoscolus tehuacanensis and Mimosa luisana were indicators of disturbance as they are found in higher relative abundance in highly disturbed quadrats. In tropical dry forest, three genera (Thevetia, Acacia and Bursera) showed higher relative abundance in conserved patches while in shrubland only one (Parkinsonia) shows this pattern, hence they could serve as indicator species.Conclusions: Our results provide evidence that disturbance in semi-arid areas of central Mexico plays an important role in species composition, facilitating the establishment of certain native species that can be considered colonizer species. These native species could be used as indicators of disturbance in assessing habitat suitability for different species.

Background and Aims: The colonization of lithic substrates by fungal communities is determined by the properties of the substrate (bioreceptivity) and climatic and microclimatic conditions. However, the effect of the exposure time of the limestone surface to the environment on fungal communities has not been extensively investigated. In this study, we analyze the composition and structure of fungal communities occurring in biofilms on limestone walls of modern edifications constructed at different times in a subtropical environment in Campeche, Mexico.Methods: A chronosequence of walls built one, five and 10 years ago was considered. On each wall, three surface areas of 3 × 3 cm of the corresponding biofilm were scraped for subsequent analysis. Fungi were isolated by washing and particle filtration technique and were then inoculated in two contrasting culture media (oligotrophic and copiotrophic). The fungi were identified according to macro and microscopic characteristics.Key results: We found 73 genera and 202 species from 844 isolates. Our results showed that fungal communities differed in each biofilm. In the middle-aged biofilm a high number of isolates was found, but both species richness and diversity were low. In contrast, in the old biofilm species richness and diversity were high; Hyphomycete 1, Myrothecium roridum and Pestalotiopsis maculans were abundant. The dominant species in the middle-aged biofilm were Curvularia lunata, Curvularia pallescens, Fusarium oxysporum and Fusarium redolens, and in the young biofilm were Cladosporium cladosporioides, Curvularia clavata, Paraconiothyrium sp. and Phoma eupyrena.Conclusions: Our results suggest that the composition of the fungal community in each biofilm varies according to time of exposure to the environment. Furthermore, the fungal community was composed of a pool of uncommon species that might be autochthonous to limestone.

Background and Aims: Wild red nanche develops in both temperate and tropical areas. In Mexico, it has been used as an ornamental and medicinal plant since pre-Hispanic times; however, little is known about its morphology. Therefore, the aim of this research was to characterize the morphological quality of fruits and endocarps of red nanche collected in the Central Valleys of Oaxaca, Mexico.Methods: Three study areas were located, but fruits were found in the municipality of Santiago Matatlán only. These were collected and transferred to the Seed Analysis Laboratory of the Colegio de Postgraduados, Campus Montecillo. For evaluation of the morphological quality of fruit and endocarps, four replications of 100 fruits were selected by Completely Randomized Design (CRD). With the obtained data, an analysis of measures of central tendency was performed using the SAS statistical package.Key results: The results indicated that the fruits of red nanche are large, oblate-shaped, the color of the epicarp is cherry to purple, that of the mesocarp pink to lilac, they taste sweet, and show adequate firmness and quantity of ascorbic acid. The fruit has three fibrous endocarps, is cone to triangular-shaped and has one to two embryos. The embryo is cream colored without endosperm, the cotyledons are bent at the apex and the radicle is present at the other side . It is protected by a thin brown colored integument.Conclusions: Variation was observed in the morphological characteristics. The fruits have food potential and quality for export.

Background and Aims: The understanding of the reproductive biology of plants, from the formation of the seed to its establishment, allows the development of different conservation strategies. In the genus Bursera, whose main center of diversification is Mexico, the diaspore is a pyrene formed by a strongly lignified endocarp enclosing the seed. The anatomical characteristics of the pyrene and the parthenocarpy are the main factors that have hindered the study of embryogenesis and the development of propagation techniques. In this paper we describe the morphology of the Bursera bipinnata embryo, extracted by a technique that does not alter the structure or the chemical composition of tissues.Methods: During the beginning of the dispersal stage 2014, we collected unripe fruits and pyrenes with exposed pseudaril. Unripe fruits were fixed in FAA. A low speed micromotor with handpiece was used. A conical burr was used in unripe fruits to scabble the fruit valves. To open the pyrenes a diamond disc was used. After opening the endocarp, embryos were removed and fixed.Key results: The pattern of development coincides with other model species of angiosperms. In immature fruits globular, heart-shaped, torpedo and cotyledonary stages were observed, the latter in early stages. During the torpedo stage, cotyledons branch into three lobes and are spliced, as they grow, they are folded upon themselves, and cover the embryonic axis; however, the radicular meristem is always exposed.Conclusions: The extraction technique is rapid, inexpensive and non-destructive to tissues, having a potential use in the detailed analysis of embryogenesis in the genus Bursera, tissue culture and ex situ conservation.

Background and Aims: Annona lutescens was described in 1914 as a new species from Guatemala. Further studies allowed to locate this taxon in Chiapas, Mexico. However, some authors consider it as a synonym of A. reticulata, a species of American origin that is widely cultivated in many parts of the world. Leaf shape and fruit color are the original characters proposed to segregate these two species. The aim of this study was to evaluate whether both characters can be used to distinguish these taxa.Methods: Leaf shape was evaluated using a geometric morphometric approach. In addition, differences in fruit color and hypocotyl coloration of seedlings maintained in controlled environmental conditions were observed.Key results: The geometric morphometric analysis showed that the leaf shape of both species is very variable and that there is no significant difference between them. Fruit and hypocotyl coloration is specific to each species.Conclusions: It is suggested that A. lutescens should be treated as a synonym of A. reticulata until more evidence is obtained to clarify the relationships between them.