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Background: Magnolia pugana populations are declining, in addition, it is estimated that precipitation will decrease by up to 10 % and temperatures will increase (2-4 °C) under the most severe climate change scenario, which may affect germination. Hypotheses: The interaction of increased temperature and decreased water potential reduces and delays the germination of Magnolia pugana seeds. Studied species: Magnolia pugana, an endangered species endemic to western Mexico. Study site and dates: Southern Zacatecas and central Jalisco, Mexico. April 2019. Materials and methods: Seed viability was evaluated with tetrazolium test. In addition, the effects of temperature (24, 28, and 37 °C), water potential with PEG 8000 (0, -0.3, -0.6, -0.9, -1.2 MPa) and its interaction on the percentage and mean germination time were analyzed with factorial ANOVA tests. Results: Viability was 80 %. The interactions between temperature and water potential on germination percentage and mean germination time were significant. There was no germination at 37 °C. The highest germination (78 %) was at 24 °C and -0.3 MPa, while the lowest (3 %) was at 28 °C and -0.6 MPa. The control treatment (24 °C and 0 MPa) facilitated germination in a shorter time (23.9 ± 1.5 days). At 28 °C and -0.9 MPa, the mean germination time was slowed by 1.5 times. Conclusions: Magnolia pugana germinability was reduced by the interaction between low water potentials and increased temperature, conditions predicted by future climate change scenarios, therefore its vulnerability to extinction couldincrease.

Abstract Mexican territory is one of the centers of origin and dispersion of the genus Opuntia, where several of its species have been an important plant resource for people in arid and semiarid zones. Opuntia streptacantha is widely distributed in Mexico; however, precise aspects of its geographic distribution and ecological status are still unknown. Here, we modeled its potential distribution under paleoclimatic, current, and future conditions through maximum entropy and predictions from 824 records and seven environmental variables. Potential distribution of O. streptacantha in the interglacial period was contracted and slightly north than current distribution, with 44,773 km2 of optimal habitat. In other past periods, the central location of potential distribution coincides with the actual current distribution, but the period of the last glacial maximum was characterized by 201 km2 of very suitable habitat, absent in interglacial, current, and future periods. The future model suggests that potential distribution will move toward the south of the Mexican territory. Synthesis and applications. The potential distribution of O. streptacantha can be applied for the conservation and management of the species, and also in the selection of areas with crassicaule scrubs for protection, conservation, and reproduction of species resistant to the hostile conditions of arid and semiarid zones of Mexican territory, where the structure and composition of the vegetation will be affected in the next 100 years.

Background: Percentage and speed of germination are crucial factors that can restrict processes involved in plant succession during ecological restoration. Pre-germination treatments and the effect of storage time on germination percentage and mean germination time were investigated in nine native herbaceous plants of the La Primavera Flora and Fauna Protection Area. Question: Do the seeds of the studied species go dormant, and can storage time affect germination percentage and mean germination time? Species studied: Aeschynomene villosa var. longifolia (Micheli) Rudd, Crotalaria pumila Ort., Dalea leporina (Ait.) Bullock, D. foliolosa (Ait.) Barneby, Desmodium aparines (Link) DC., D. distortum (Aubl.) JF Macbr., D. tortuosum (Sw.) DC., Paspalum notatum Flüggé, and Zornia reticulata I. E. Smith. Place and dates of study: Area of Protection of Flora and Fauna La Primavera. From 2019 to 2020 Methods: Under greenhouse conditions, four treatments were applied prior to germination: scarification with a tweezer pliers, immersion in water at 40 ᵒC for 24 and 48 h, and control. Results: Seven species had highly viable (≥ 90 %) seeds after 12 months of storage. Five species with seed dormancy reached germination above 80 % after 24 months of storage and scarification with a tweezer pliers. Mean germination time for most species decreased with the scarification treatment. Conclusion: Our findings provide basic information on the germination of native species that could help restore degraded sites in the La Primavera Flora and Fauna Protection Area.

In Mexico, plants with crassulacean acid metabolism (CAM) are part of the Mexican culture, have different uses and are even emblematic. Unfortunately, only a small fraction of the Mexican CAM plants has been studied physiologically. For this review, the following questions were considered: What ecophysiological studies have been conducted with CAM species native to Mexico? What ecophysiological processes in Mexican CAM plants are the most studied? What type of ecophysiological studies with CAM plants are still needed? A database of scientific studies on CAM plant species from Mexico was documented, including field and laboratory works for species widely distributed, and those studies made outside Mexico with Mexican species. Physiological processes were grouped as germination, photosynthesis, and water relations. Most studies were done for CAM species of Cactaceae, Bromeliaceae, Asparagaceae and Orchidaceae, andmost ecophysiological studies have been done on germination of cacti. Field and laboratory studies on photosynthesis and water relations were mostly for terrestrial cacti and epiphytic bromeliads. There were few physiological studies with CAM seedlings in Mexico and few studies using stable isotopes of water and carbon of CAM plants in the field. More field and laboratory studies of physiological responses and plasticity of CAM plants to multiple stress factors are required to model plant responses to global climate change. In general, more physiological studies are essential for all CAM species and for species of the genus Clusia, with C3-CAM and CAM members, which can become ecologically important under some climate change scenarios.

La calidad de vida es un aspecto relevante en la vida de las personas, más aún cuando se presentan comorbilidades altas en población general, por lo que su medición de forma válida y confiable es necesaria. Objetivo: Determinar las propiedades psicométricas del Instrumento de Evaluación de Funcionalidad en el Tratamiento para Enfermedades Crónicas (FACT-GP) en población general mexicana. Método: Se empleó un diseño transversal, con un muestreo no probabilístico, por disponibilidad. Análisis estadístico: Se realizó un modelo factorial confirmatorio. Resultados: Se incluyeron 254 participantes con M = 23.5 años (21-32). Se identificaron 4 factores con 18 reactivos. La consistencia interna de la escala global fue .81, que explican el 58.93 % de la varianza. El análisis factorial confirmatorio presenta índices adecuados (CFI, RMR, RMSEA), que indican un ajuste equilibrado y parsimonioso de la estructura del modelo. Conclusión: El FACT-GP mostró una estructura similar a la versión original, con indicadores válidos y confiables para su uso en la atención clínica e investigación dirigida a población general mexicana.

La competencia y la facilitación son factores importantes que afectan la supervivencia de las plántulas y probablemente afectan la distribución y abundancia de las plantas. Las interacciones entre especies se relacionan con la filogenia, es probable que las especies estrechamente relacionadas compitan más por recursos y que en las menos emparentadas ocurra facilitación. Se investigó si plantas de matorral tamaulipeco creciendo junto a parientes cercanos y lejanos diferían en supervivencia, longitud y peso de tallos y raíces, asumiendo que las especies estrechamente relacionadas competirían más que las lejanas. También se exploró si el peso de semillas se asoció con el tamaño de la planta entre 1 y 24 meses de edad. Se pusieron a crecer plantas de matorral tamaulipeco, con un hermano o con un individuo de otras especies, de 1-24 meses. La supervivencia de plántulas fue similar para todas las especies cuando éstas crecieron solas o en competencia, a los 1, 6 y 12 meses. A los 24 meses, la supervivencia de plántulas de Vachellia farnesiana fue menor cuando creció con Havardia pallens. No hubo evidencia de una competencia o facilitación fuerte para especies filogenéticamente más cercanas. El tamaño de la plántula se correlacionó con el peso de la semilla únicamente al mes de germinadas. La altura máxima y promedio de la planta adulta no se correlacionó con el peso de semillas o con la altura de la planta. La filogenia no explicó la competencia con los vecinos más cercanos durante la germinación de especies del matorral tamaulipeco.

Background and aims – The reproductive characteristics of sympatric Cactaceae are important because they help to understand interfering or facilitating mechanisms that allow their coexistence. Globose Cactaceae show melittophily flowers that may be attractive to a shared set of pollinators, and if the flowering events are not overlapping, flower resources could be present for the pollinators through time. Ariocarpus kotschoubeyanus and Neolloydia conoidea are two sympatric cactus species in the southern Chihuahuan Desert. The objective of this study is to describe and compare some reproductive characteristics of these species.Material and methods – Individuals of Ariocarpus kotschoubeyanus and Neolloydia conoidea (n = 231 and 212, respectively) were marked and monitored during one year, recording for each species, the floral phenology, behaviour and morphology, flower visitors, breeding and mating systems (through pollination experiments).Key results – The flowering periods of these species do not overlap. The flowers of both species are melittophily, with the same shape, colour, and similar behaviour; both are obligate xenogamous plants. The mating system of Neolloydia conoidea is outcrossing but mixed in Ariocarpus kotschoubeyanus. They share 75% of pollinators (solitary and social bees).Conclusions – The temporal blooming separation of these species could be an important factor to facilitate coexistence within the xerophyte community since they share the same set of pollinators to achieve their reproductive success.

Gypsum soils occur around the world, mainly in arid regions. These harsh environments promote unusual flora with high degrees of endemism. Mexico has extensive gypsum outcrops, but their flora has been poorly studied. However, the highest species richness and endemism are expected to be concentrated in Mexico’s northern dry regions. To promote the study of this flora and its conservation, we estimate how well sampled it is, quantify species richness, identify centers of endemism, and detect which gypsum outcrops lie within federal protected natural areas (PNA). We conducted exhaustive literature and herbaria reviews to generate a database of botanical records on gypsum soils. The total species and gypsophyte richness were calculated using cell grids. Centers of endemism were identified using the corrected weighted endemism index (CWE). We mapped the gypsum outcrops within PNA polygons. The most collected sites are Cuatro Ciénegas (Coahuila) and Santo Domingo Tonalá (Oaxaca), which also had the highest total species richness. Nevertheless, gypsophyte richness was higher in Cuatro Ciénegas and Nuevo León. The CWE identified seven gypsophyte centers of endemism. Mexico hosts the most diverse gypsophile flora in the world, despite having been only partially studied and collected. The regions with the highest species richness and endemism are unprotected.

An integrative geographical climatology is presented to objectively identify regional patterns of climate variability within the mid-low Nazas-Aguanaval basin within the States of Durango and Coahuila in Central Northern Mexico, using decadal mean values for maximum and minimum temperature, as well as monthly precipitation during the seven periods from 1951-2020. The historical data was acquired from 26 field meteorological stations and 44 grid points from the SWAT model. Furthermore, the data was categorized by means of geographical features of altitude, longitude and latitude in three groups each. A combination of meteorological vulnerability from all the categories for each sampling point was then estimated for each locality. From the overall analysis, western sites resulted as the most vulnerable to climatic changes, while eastern and central (latitude) displayed the lowest variability occurrence. By means of downscaling the meteorological variation, it is possible to improve the understanding of mechanisms relying on regional climate variability and climate change. This evaluation can be further incorporated to management strategies for different stakeholders in arid and semi-arid lands, particularly within the Chihuahuan Desert.

Cactus species are key components in American deserts and have a high socioeconomic value. Climate change exerts a threat to biodiversity, structure and functioning within deserts and many cactus species are predicted to face extinction because of climate change. Defining which plant species could tolerate climate change effects in desert ecosystems acquires crucial importance to promote conservation of these species. Echinocactus platyacanthus is a specially protected cactus species, widely distributed in desert areas of Mexico; however, long-term implications of climate change on survival and physiological responses of this species are still unclear. We assessed the effect of induced warming in the photosynthetic performance and survival on five-years old individuals of Echinocactus platyacanthus for a year. Open-top chambers (OTCs) were used to simulate the effect of global warming (a drive of climate change), while controls were exposed to the current climatic conditions. A generalized canonical correlation analysis was used to measure the intensity of the relationship among environmental variables (mean air temperature, evapotranspiration, global photon flux density, and rainfall), micro-environmental (mean temperature, mean relative humidity and photosynthetic photon flux density) and ecophysiological variables [effective quantum yield of photosystem II (ΦPSII) and electron transport rate (ETR), both within and outside of OTCs]. OTCs had higher temperature than control plots through the seasons. Echinocactus platyacanthus showed higher seasonal variations in photosynthetic performance under warming than in current temperature; nevertheless, 100% survival in both treatments were found. The ΦPSII and ETR values were lower in summer inside OTCs but increased in autumn and winter. We found a strongest correlation between environmental and micro-environmental variables, as well as between micro-environmental and ecophysiological ones, which support the premise that the young individuals of E. platyacanthus depends on the microenvironment to survive. Although after a continuous year under induced warming, individuals of E. platyacanthus showed a decrease in the ΦPSII values during summer and spring and an increase in autumn and winter, survival was not affected. These results reflect the high tolerance in early developmental phases of E. platyacanthus, an adequate functioning of the photosynthetic apparatus of this species could be an efficient physiological mechanism to face future climate change.

Interest in invasive species has increased around the world over the last several decades. In Mexico, studies on invasive species date as early as 1939 and the number of publications has increased considerably in recent decades. However, to our knowledge, the analysis of information gaps and research priorities is lacking. Therefore, it is necessary to identify gaps in the knowledge of invasive species in order to define future research priorities and focus conservation efforts. We assessed the current state of knowledge of biological invasions in Mexico based on the existing literature. Our aim was to identify in which areas information is absent or insufficient and which areas should be prioritised. We identified a total of 869 references. The number of references increased over time and the topics were strongly biased towards two areas: 1) natural history and geographical distribution patterns and 2) effects on native biota and ecosystems. The remaining topics were only moderately or poorly studied. Most studies focused on vascular plants (n = 280) and fishes (n = 174). Notably, a large portion of the references (n = 215) focused on only eight invasive alien species, including their ecological and socioeconomic impacts. Only 95 references examined the effects of alien species on biodiversity; these studies were mainly carried out on islands (n = 41) or in terrestrial or freshwater ecosystems in protected natural areas (n = 165). The findings of the present review can guide future studies in filling in the existing research gaps on biological invasions. Additionally, future studies should aim to define national priorities of the impacts of biological invasions and to promote the prevention and control of alien species by considering the distinct vectors and pathways of introduction and movement.

Dolines are karst depressions whose environmental and climatic characteristics in tropical regions are not well known. By measuring and analyzing different components of the microclimate in two dolines located in Tamasopo, Mexico, we aim to contribute to the understanding of the climatic conditions in these formations. The variables analyzed include temperature, solar radiation, soil and air humidity, as well as their relationship to physical and chemical characteristics of the soil such as pH, conductivity, texture, and the content of organic matter, carbon, nitrogen, phosphorus, calcium, potassium, sodium and magnesium. Measurements and soil samples were taken in three strata: bottom, slope and exterior. The results show a gradient in the climatic variables along the three strata, as well as higher concentrations of all elements, except phosphorus, in soil from the dolines, with respect to the exterior. Furthermore, statistical analysis shows a high correlation between the environmental conditions and edaphic properties. The micro climatic factors of the dolines generate a different environment, rich in humidity and with temperatures commonly lower than those present in tropical regions. These conditions cause abrupt changes in the physical and chemical composition of the soil, which present high concentrations of nutrients.

Antecedentes: La distribución de plantas depende de dispersores que transportan semillas a hábitats adecuados y de plantas que faciliten o inhiban germinación y establecimiento. Es importante conocer cómo estos factores influyen en la distribución de la vegetación y contemplar esta información en planes de manejo. Hipótesis: Las semillas y plántulas de las especies estudiadas diferirán en abundancia bajo diferentes especies de árboles y posición respecto al borde de la vegetación. Se espera una mayor densidad de semillas y plántulas bajo especies de árboles dispersos por animales y en los bordes de los fragmentos. Método. Se realizó conteo directo de semillas y plántulas de Zanthoxylum fagara (L.) Sarg. en México y Zanthoxylum coco Gillies ex Hook.f. & Arn. en Argentina, en fragmentos de vegetación remanente bajo copas de árboles, en borde e interior de vegetación. Resultados: Para ambas especies, la densidad de semillas fue similar en borde y en interior. La densidad de plántulas de Z. fagara fue mayor en el borde que 40 m al interior, así como bajo las copas de árboles dispersados por fauna. Para Z. coco no se encontraron diferencias. Conclusiones: Para ambas especies los dispersores de semillas no parecen importantes, se presenta similar densidad de semillas en borde e interior. Quizá tengan efecto en regeneración de Z. fagara, con mayor densidad de plántulas en borde que al interior. Es probable que mayor disponibilidad de luz en borde promueva regeneración de esta especie. Para Z. coco no parece existir un efecto de los dispersores en la regeneración.

Background: In semiarid ecosystems, many plant species are tolerant to drought. However, increased aridity as a result of climatic change could modify the capacity of germination and establishment. Hypothesis: Under drought conditions, small-seeded species will tend to germinate in higher proportions than large-seeded species because the former have larger surface-to-volume ratio, allowing for more rapid water uptake. Study species: Ageratina espinosarum, Flourensia resinosa, Montanoa tomentosa and Gymnosperma glutinosum (Asteraceae), Dalea bicolor, Eysenhardtia polystachya and Mimosa pringlei (Fabacecae). Study site: Hidalgo, Mexico. September 2015. Methods: We evaluated the effect of five water potential treatments on seed germination. Four dishes (replicates), each with 25 seeds, were used in each treatment. Seeds of each species were weighed and the relationship between seed germination under water stress and seed size was obtained. Results: Germination decreased as water potential was reduced; almost no seeds germinated at -0.8 MPa. The least sensitive species was Eysenhardtia polystachya, whose germination reached 35 % at -0.6 MPa. A positive relationship was found between seed size and germination proportion under water stress. Conclusions: Contrary to expectation, germination was higher in the large-seeded species in all drought treatments, suggesting that large seeds may have a greater capacity to retain water in dry environments.

Background: Cactaceae is the fifth taxonomic group with the highest proportion of threatened species and among the angiosperms, the most vulnerable to human disturbance. One way to contribute to the preservation of this family is to understand the processes that promote seed germination. Questions: Have the relationship between seed traits and cactus germination been documented? How common is dormancy and seed banks in Cactaceae? Are there general patterns in cacti germination response to temperature, light, water, salinity, phytohormones, hydration/dehydration cycles, mechanical or chemical scarification? Data description: A total of 333 studies on cactus germination with information on 409 taxa. Study site and dates: since 1939 to January 2020. Methods: A search of scientific articles in Google Scholar was performed with the words Cactaceae, cacti and cactus, in combination with various matters on germination in English, Spanish and Portuguese. Results: The main germination studies in cactus deal with photoblasticism (275 taxa), temperature (205 taxa) and seed longevity (142 taxa). Other lines of study in cactus germination (e.g., desiccation tolerance, vivipary, phytohormones, mechanical or chemical scarification, in vitro germination, hydration/dehydration cycles, water and saline stress, serotiny, storage in cold, high temperature tolerance and soil seed bank) include between 14 and 65 taxa. Cacti have only physiological dormancy and optimal germination for most species occur between 20 and 30 °C. Photoblasticism is strongly influenced by phylogeny with 80.9 % positive photoblastic species. Conclusions: Mexico, Brazil and Argentina are the three leading countries in the study of cactus germination.

Opuntia spp. are cacti with high ecological, economic and conservation interest in semiarid environments, particularly in Mexico. We conducted a systematic search of the existing peer-reviewed literature about the state of knowledge of pollination ecology on these plants. We documented the most studied Opuntia species worldwide with an emphasis on Mexico. We found that only 15% of Opuntia species described have been investigated so far, and studies were mainly focused on comprehension of the biology of a single species. Despite the economic and cultural importance of Opuntia, there is a significant lack of knowledge about the flower-visiting insects and their taxonomic identity. We provide a checklist of the insect species associated with Opuntia spp. Through a circular network, we visualize the complex Opuntia flower-visiting insect relationship, and we detected a set of key species constituting the generalist core of the networks constructed. Since pollination is crucial for crop production, a better understanding of ecological interactions would inform management measures to strengthen biodiversity and agriculture sustainability as well as productivity in arid and marginal lands. Further research on pollination ecology is needed to improve the conservation status of the insects associated with Opuntia species.

Background. Plant morphology is the expression of a set of characteristics in response to environmental conditions and therefore to the availability of resources. Questions. Are the populations of Turnera diffusa morphologically different due to climatic factors? Species studied. Turnera diffusa, known as “damiana”. Study site and dates. Jaumave and Güémez in Tamaulipas, Mexico; during October 2013 and April 2014. Methods. Abiotic characteristics of study sites and morphological traits of the plants were evaluated, as well as the exposure of the plants to light, and the flowering; 15 random transects of 100 m2 each were made in each site. A multivariate analysis with linear discriminant functions was applied to determine possible differences between the two populations considering the morphological variables. Results. The population of T. diffusa of Güémez did present higher branch density and bigger leaves than those of Jaumave, which can be related to the greater precipitation that is received in that locality in comparison with Jaumave. T. diffusa plants with higher height were found under natural shade conditions and flowering is a condition that seems to be unrelated to the exposure. Conclusions. Populations of Turnera diffusa of Jaumave and Güémez were morphologically different.

Background: Climate change will increase temperature and reduce rainfall across temperate forests of Mexico. This can alter tree establishment dynamics within forest and in neighbouring man-made clearings. Hypotheses: Climate change will reduce emergence and survival of tree seedlings, and surviving plants will display functional responses matching with these changes. These effects should be more noticeable in clearings due to the lack of canopy cover. Studied species: Quercus eduardii (Fagaceae, section Lobatae) an oak species endemic to Mexico. Study site and years of study: Tree growing season 2015-2016 (rainy season) in a mature oak forest and a neighbouring clearing in Sierra de Álvarez, state of San Luis Potosí. Methods: In both habitats, we established control plots (under current climatic conditions) and climate change simulation plots (increased temperature and reduced rainfall). At the beginning of the growing season, we sowed acorns of Q. eduardii in these plots and monitored the emergence, survival and growth of seedlings. At the end of the growing season, we assessed functional responses on surviving seedlings. Results: Seedling emergence and survival were lower in climate change plots from both habitats. However, differences in survival between climate treatments were larger within the forest. Seedlings from climate change plots displayed functional responses indicating higher levels of thermal and water stress. Conclusions: This study indicates that climate change will constrain tree recruitment in Mexican oak forests. However, contrary to our expectations, it seems that these effects will be higher within forests than in man-made clearings.

El incremento en las temperaturas puede afectar de forma positiva o negativa la germinación. Se estima que la temperatura se incrementó en las últimas décadas 0.6 °C y se espera que para el año 2099 aumente entre 1.5 y 4.7 °C. El objetivo del presente trabajo fue evaluar la germinación de semillas de siete procedencias de Acacia farnesiana y tres de A. schaffneri a diferentes temperaturas. La información generada permitirá conocer la respuesta de ambas especies ante el incremento de las temperaturas. Se recolectaron frutos de al menos 10 plantas madre/por procedencia/taxón, se escarificaron las semillas, sembraron en charolas de plástico y se colocaron en una germinadora a temperatura de suelo real (Testigo (T0)), y cinco tratamientos con aumento de temperatura: testigo +2 °C (T1), +5 °C (T2), +7 °C (T3), +10 °C (T4) y +15 °C (T5), durante 15 días. A. farnesiana presentó un mayor porcentaje de germinación en el T2 y T3; mientras que A. schaffneri en el T2; no hubo diferencias significativas entre las procedencias de cada una de las especies. A. farnesiana germinó con mayor rapidez (t50) en el T3, con diferencias significativas entre procedencias (mayor velocidad FCF) y A. schaffneri en el T1, sin diferencias significativas entre sus procedencias. Los resultados sugieren que ambos taxa y sus procedencias tienen la capacidad de germinar si las temperaturas aumentan conforme a los pronósticos.

Tomato susceptibility/resistance to stem canker disease caused by Alternaria alternata f. sp. lycopersici and its pathogenic factor AAL-toxin is determined by the presence of the Asc1 gene. Several cultivars of commercial tomato (Solanum lycopersicum var. lycopersicum, SLL) are reported to have a mutation in Asc1, resulting in their susceptibility to AAL-toxin. We evaluated 119 ancestral tomato accessions including S. pimpinellifolium (SP), S. lycopersicum var. cerasiforme (SLC) and S. lycopersicum var. lycopersicum “jitomate criollo” (SLJ) for AAL-toxin susceptibility. Three accessions, SP PER018805, SLC PER018894, and SLJ M5-3, were susceptible to AAL-toxin. SLC PER018894 and SLJ M5-3 had a two-nucleotide deletion (nt 854_855del) in Asc1 identical to that found in SLL cv. Aichi-first. Another mutation (nt 931_932insT) that may confer AAL-toxin susceptibility was identified in SP PER018805. In the phylogenetic tree based on the 18 COSII sequences, a clade (S3) is composed of SP, including the AAL-toxin susceptible PER018805, and SLC. AAL-toxin susceptible SLC PER018894 and SLJ M5-3 were in Clade S2 with SLL cultivars. As SLC is thought to be the ancestor of SLL, and SLJ is an intermediate tomato between SLC and SLL, Asc1s with/without the mutation seem to have been inherited throughout the history of tomato domestication and breeding.

Ephedra is one of the largest genera of the Ephedraceae family, which is distributed in arid and semiarid regions of the world. In the traditional medicine from several countries some species from the genus are commonly used to treat asthma, cold, flu, chills, fever, headache, nasal congestion, and cough. The chemical constituents of Ephedra species have been of research interest for decades due to their contents of ephedrine-type alkaloids and its pharmacological properties. Other chemical constituents such as phenolic and amino acid derivatives also have resulted attractive and have provided evidence-based supporting of the ethnomedical uses of the Ephedra species. In recent years, research has been expanded to explore the endophytic fungal diversity associated to Ephedra species, as well as, the chemical constituents derived from these fungi and their pharmacological bioprospecting. Two additional aspects that illustrate the chemical diversity of Ephedra genus are the chemotaxonomy approaches and the use of ephedrine-type alkaloids as building blocks in organic synthesis. American Ephedra species, especially those that exist in Mexico, are considered to lack ephedrine type alkaloids. In this sense, the phytochemical study of Mexican Ephedra species is a promising area of research to corroborate their ephedrine-type alkaloids content and, in turn, discover new chemical compounds with potential biological activity. Therefore, the present review represents a key compilation of all the relevant information for the Ephedra genus, in particular the American species, the species distribution, their ecological interactions, its ethnobotany, its phytochemistry and their pharmacological activities and toxicities, in order to promote clear directions for future research.

Agave victoriae-reginae es una especie endémica del Desierto Chihuahuense y crece sobre paredes en cañones. Posee semillas aplanadas que pueden ser dispersadas durante eventos episódicos de inundación. La presente investigación se basó en determinar posibles adaptaciones morfológicas y anatómicas en las semillas que favorecen la hidro-dispersión. Se realizó un análisis morfológico y anatómico de las semillas mediante microscopía electrónica de barrido (MEB). Se evaluaron aspectos de permeabilidad, flotabilidad, germinación y velocidad de germinación (T50) por tratamientos y tamaños de semilla. Las semillas son diferentes en longitud, diámetro, espesor y no en peso; con forma lacriforme semi- planas y cubierta porosa con cámaras de aire en la hipodermis y son consideradas fotoblásticas neutras. Se concluye que las semillas de la especie poseen características propias para la hidro-dispersión.

Se presenta un estudio morfométrico y microestructural en semillas de una población de la cactácea amenazadaAstrophytum myriostigmaLem., removida en su tota- lidad en el sitio por saqueo. Se incluyen resultados que separan tamaños de semillas y embriones (grandes y pequeños) así como promedios para ambos. Se realizó una descripción de características en la semilla obtenidas mediante estereoscopía. Se incluye una descripción detallada de la forma y color, así como microestructural del funículo, capa funicular y otras estructuras que le acompañan.

Introducción: La toxoplasmosis causada por el Toxoplasma gondii se transmite a los humanos de manera transplacentaria, entre otras. Se estima que infecta a un tercio de la población mundial y está asociado con infección congénita y abortos. Solo son sintomáticos del 10 al 20% de los casos. Caso clínico: Se presenta el caso de un recién nacido pretérmino referido a un hospital de mayor complejidad. Durante la hospitalización se realiza el diagnóstico de toxoplasmosis congénita con diversas manifestaciones sistémicas. Conclusiones: La mayor parte de los casos de toxoplasmosis congénita suelen ser asintomáticos. Es necesario realizar pruebas diagnósticas y un examen físico completo ante la sospecha de la infección para detectar tempranamente todas las manifestaciones posibles.

A total of six species of pelagic shrimps were collected during the TALUD XIV cruise aboard the R/V "El Puma", in the northern Gulf of California, in April 2011, including two species of Dendrobranchiata [Eusergestes similis (Hansen, 1903) and Sergia phorca (Burkenroad, 1940)], and three species of Caridea [Pasiphaea americana Faxon, 1893, P. emarginata Rathbun 1902, and P. pacifica Rathbun, 1902]. Additional specimens of the previously reported Maryprocessa pippinae (Wicksten & Méndez, 1985) were also found among the samples. Most frequently collected species were P. americana (50% of total) and P. pacifica (36.6%). Most numerous species in the samples were P. pacifica, P. americana and E. similis. Some minor morphological differences not previously recorded in specimens of Pasiphaea pacifica collected elsewhere were detected. These differences might correspond to an intraspecific variation.

Título en ingles: Evaluation of the mutagenic potential of biocides (vertimec and pentachloro) on onionTítulo corto: Genotoxicidad en Allium cepa producida por biocidas.Resumen: El uso de biocidas es una constante en el campo agronómico, el daño ocasionado a los cultivos y por consiguiente el gran potencial de daño para los consumidores es conocido, sin embargo su uso sigue en marcha. Por ello se realizaron pruebas citogenéticas para la observación de aberraciones cromosómicas en Allium cepa, usando muestras de raíces de plantas expuestas y no expuestas a biocídas. Los tratamientos se realizaron con el objetivo de comparar el grado de afectación de los biocídas sobre la mitosis y la ocurrencia de mutaciones cromosómicas. El ANOVA para los datos de desarrollo radicular al finalizar la experimentación, mostraron un CV de 9.88, se observo diferencias significativas entre el control y los tratamientos, los porcentajes de inhibición llegaron a tener valores máximos de 84.2% para vertimec X8 y 76.5% para pentacloro X8, y valores mínimos de 38.2% para vertimec X0.5 y 43.8% para pentacloro 0.5 X. El índice mitótico fue mayor para el control (0.193) y menores para el tratamiento con menor desarrollo radicular, vertimec X8 (0.021) y pentacloro X8 (0.028). Las pruebas citogenéticas mostraron la ocurrencia de anomalías en el ciclo celular siendo la más frecuente la C-mitosis. Se puede concluir que el test Allium es un buen indicador de citotoxicidad y genotoxicidad. Los biocidas ocasionan cambios en la estructura genómica de un cultivo, estos cambios podrían acumularse y ocasionar cambios de expresión génica, pudiendo dañar regiones de interés agronómico para una especie y afectar su estabilidad genética. Palabras clave: test Allium, anomalía mitótica, estabilidad genética, genotoxicidad, citotoxicidad.Abstract: The use of biocides is a constant in the agronomic field. The damage to crops and therefore, the potential harm for consumers is known;however, they are still in use. As a result, tests to observe cytogenetic aberrations in Allium cepa were performed, using plants’ roots samples exposed and not exposed to biocides. Treatments were performed in order to compare the degree of impact of biocides on mitosis and the presence of chromosomal mutations. The ANOVA for root development data at the end of the experiment showed a CV of 9.88. Significant differences were observed between control and treatments. Inhibition percentages reached a maximum of 84.2% for Vertimec X8 and 76.5% for pentachloro X8, and minimum values of 38.2% for Vertimec X0.5 and 43.8% for pentachloro X0.5. The mitotic level was higher for control (0.193) and lower for treatment with less root development Vertimec X8 (0.021) and pentachloro X8 (0.028). Tests showed the appereance of cytogenetic abnormalities in the cell cycle, being C-mitosis the most frequent one. It can be concluded that the Allium test is a good indicator of cytotoxicity and genotoxicity. Biocides cause changes in the genomic structure of crops, which may accumulate and cause gene expression changes that can damage regions of agronomic interest for a species and affect its genetic stability.Key words: Allium test; mitotic abnormalities; genetic stability; genotoxicity;cytotoxicity

Los encinos blancos tienen semillas recalcitrantes que se mantienen viables por corto tiempo. Sin embargo, esta información es escasa para encinos mexicanos. Este es el caso de Quercus polymorpha, una especie tolerante a la sequía y ampliamente distribuida en la Sierra Madre Oriental que puede utilizarse en programas de restauración forestal. Las bellotas son colectadas durante la época reproductiva y son almacenadas por varios meses antes de su germinación. Este estudio se enfocó en 1) determinar cuántas semillas se pierden durante el almacenamiento debido a factores fisiológicos relacionados con su viabilidad, 2) cuantificar las semillas que se pierden por otros factores, y 3) evaluar si la estratificación fría puede estimular la germinación de las bellotas. Las bellotas utilizadas fueron almacenadas durante un año. El 70 % de las bellotas estaban parasitadas por insectos antes de su almacenamiento, mientras que el 20 % perdió su viabilidad debido a factores fisiológicos o infestación por hongos. Los ensayos de germinación se llevaron a cabo utilizando sólo bellotas potencialmente viables, las cuales fueron sometidas a tres periodos de estratificación en frío (0, 20 y 50 días). El experimento mostró que las bellotas estratificadas durante 50 días tienen mayores tasas de germinación (64.2 %) que las de 20 (44.8 %) y 0 días (16. 5 %).

Magnolia pugana es una especie endémica y en peligro de extinción localizada en el occidente de México, que se distribuye en bosques de galería en las barrancas del sur de Zacatecas y centro-norte de Jalisco. El objetivo de este trabajo fue conocer la viabilidad de las semillas e identificar los tratamientos para romper la latencia de semillas de esta especie. Se colectaron semillas de cuatro localidades, tres en Jalisco (Centro Universitario de Ciencias Biológicas y Agropecuarias, San Lorenzo y San Nicolás) y una en Zacatecas (Palo Verde). Se aplicaron los siguientes tratamientos germinativos: (1) remoción manual del arilo, (2) remoción de arilo por lixiviación, (3) inmersión en ácido giberélico con 100 mg L-1, (4) inmersión en ácido giberélico con 200 mg L-1, (5) inmersión en ácido giberélico con 300 mg L-1 y (6) control. Se utilizaron 100 semillas por tratamiento con cinco repeticiones cada una. El tratamiento que presentó el mayor porcentaje de germinación para las cuatro localidades fue la remoción manual del arilo con 52 %, mientras que el tratamiento con menor germinación fue el control con 3.5 %. Por localidad, San Lorenzo obtuvo el mayor porcentaje de germinación con 16.5% en promedio, mientras que San Nicolás registró el menor con 5.33 %. Los tratamientos germinativos no lograron romper la latencia (porcentajes de germinación < 70 %). Las semillas de las cuatro localidades se embebieron de agua por lo que no se presenta la latencia física. Las semillas con mayor biomasa absorbieron menos agua.

We evaluated the effect of spine removal on three cactus species varying in spine-shading of stems. Turbinicarpus schmiedickeanus showed the greater spine shading (c. 61 %), followed by Mammillaria zephyranthoides (43 %), and Echinocactus platyacanthus (17 %). We evaluated photosynthetic activity [titratable acidity, electron transport rate, potential quantum yield of Photosystem II, effective quantum yield of Photosystem II, and non-photochemical quenching], as well as pigment content (chlorophylls a and b, total chlorophyll, chlorophyll a/b, carotenoids, and total chlorophyll/carotenoids ratio). For T. schmiedickeanus, the species having the higher spine shading, spine removal increased the CAM activity (acidity level) and the effective quantum yield of Photosystem II and diminished both electron transport rate and non-photochemical quenching at 15:00 hours. For M. zephyranthoides, the species having intermediate spine shading, spine removal also increased the acidity level but diminished effective quantum yield of Photosystem II at midday, as well as chlorophyll a, total chlorophyll, and carotenoids, although there was higher non-photochemical quenching (heat quenching) as an adaptation to avoid photosynthetic damage. Spine removal did not affect acidity level or pigment content from E. platyacanthus, the species having the lower spine shading; however, at midday this species without spines showed a decrease of effective quantum yield of Photosystem II, as well as an increase of non-photochemical quenching and electron transport rate. We suggest that a main function of cactus spines is reduction of sun exposure to avoid damage to the photosynthetic apparatus.

The Peruvian peppertree (Schinus molle) is a dioecious species from South America that was introduced into central Mexico five centuries ago. This tree has invaded abandoned agricultural fields from semiarid regions, where it can be found with several native succulent plants that have recolonized these areas. Although peppertrees have negative allelopathic effects on crops, their effects on these native plants remain unknown. Indeed, the allelopathy of peppertrees has only been tested for female individuals, while the allelopathic potential of male peppertrees has not been assessed yet. This study focused on these issues and assessed whether peppertrees affect germination of succulent plants from the Chihuahuan Desert and whether these effects differ between male and female trees. For this we conducted a series of germination bioassays where seeds of native species were watered with aqueous extracts of staminate flowers and leaves produced by male peppertrees, and with aqueous extracts of fruits and leaves produced by female peppertrees. Additionally, we conducted experiments where seeds of native species were sowed on soils collected beneath the canopy of both tree genders. The results of all these experiments indicated that both peppertree genders can reduce germination of native species, but also suggested that male peppertrees would have stronger allelopathic effects than female peppertrees. To our best knowledge, this is the first study reporting allelopathic effects of peppertrees on native plants from Mexico, but this is also the first study indicating differential gender effects for invasive dioecious species with allelopathic potential.

Plants from drylands have developed strategies to germinate even in places where available humidity is sporadic with large periods of drought. Previous works determined germination of cacti species as a response to discontinuous humidity events (“seed hydration memory”). This study is aimed at assessing whether species of the Chihuahuan Desert show a seed hydration memory. Our hypothesis is that seeds of desert species can tolerate periods of dehydration after single or multiple hydration events and subsequently germinate more and faster. We evaluated nine species: Sartwellia mexicana, Echinocactus platyacanthus, Cucurbita foetidissima, Lepidium virginicum, Lesquerella berlandieri, Yucca filifera, Atriplex canescens, Nassella tenuissima, and Ferocactus pilosus, using four treatments: T1 = 24 hours hydration/5 days dehydration (HD), T2 = Three consecutive cycles of 24 hours hydration/5 days dehydration, T3 = 72 hours hydration /5 d dehydration, and T4 = Control. Echinocactus platyacanthus, Nassella tenuissima, Ferocactus pilosus, and Lepidium virginicum showed higher germination with HD treatments than the control. Ferocactus pilosus and Lepidium virginicum had the highest germination in T2, Nassella tenuissima in T3, Echinocactus platyacanthus in any HD treatment while Yucca filifera in the control and T2. Yucca filifera and F. pilosus had the lowest germination rate (t50) in T2; E. platyacanthus in T1 and T2. The remaining species didn’t show differences in t50 between treatments. These results indicate that at least some desert species germinate more and faster after single or multiple hydration- dehydration events evincing the ability of those seeds to retain, during dehydration, the physiological changes produced from seed hydration.

We characterized variations in Cordia boissieri flowers and established if these variations occur between plants or between flowering events. Flowering and fruiting was measured for 256 plants. A GLM test was used to determine the relationship between flowering and fruit set processes and rainfall. We performed measurements of floral traits to detect variations within the population and between flowering events. The position of the anthers with respect to the ovary was determined in 1,500 flowers. Three out of four flowering events of >80% C. boissieri plants occurred after rainfall events. Only one flowering event occurred in a drought. Most plants flowered at least twice a year. The overlapping of flowering and fruiting only occurred after rainfall. Anthesis lasted three-to-five days, and there were two flower morphs. Half of the plants had longistylus and half had brevistylus flowers. Anacahuita flower in our study had 1–4 styles; 2–9 stamens; 6.5–41.5 mm long corolla; sepals from 4.5–29.5 mm in length; a total length from 15.5–59 mm; a corolla diameter from 10.5–77 mm. The nectar guide had a diameter from 5–30.5 mm; 4–9 lobes; and 5 distinguishable nectar guide colors. The highest variation of phenotypic expression was observed between plants.

The endangered cycad Dioon edule requires shade provided by filtered sunlight under the canopy of trees or maternal plants during initial growth stages. It is known that germination improves under shade, but there is no report of radiation conditions. In order to understand how photosynthetic photon flux density (PPFD) affect germination traits, we evaluated some germination indexes. A sample of three mature strobili and 200 viable seeds per strobilus were selected to evaluate seed size (length, width, and fresh weight). Two experimental treatments were established simulating shade under the oak forest canopy with PPFD 81 µmol m?2 s?1 (PPFD81), and under maternal plant canopy with PPFD 17 µmol m?2 s?1 (PPFD17), as measured previously in the study site. Means of response variables (germinability, velocity of germination, synchronization, mean germination time and relative frequency of germination) for the two treatments were compared using a t-test and a correlation analysis. No significant correlation between seed size and germination traits was detected. Germinability was higher at PPFD17 (89 %) than PPFD81 (39 %), but mean germination time was similar across treatments. The velocity of germination was greater under PPFD17 but synchronization was the opposite. The low PPFD stimulated D. edule germination, but also the spectral composition must be evaluated.

Se evaluó el efecto de la densidad de semillas en la germinación de 2 cactáceas columnares: Isolatocereus dumortieri y Myrtillocactus geometrizans. Se utilizaron 5 tratamientos de densidad de semillas (1, 5, 10, 20 y 50 semillas). Isolatocereus dumortieri mostró menor porcentaje de germinación con el aumento de la densidad, mientras que la germinación de M. geometrizans no fue afectada por la densidad de semillas. Estos resultados sugieren que las plántulas de I. dumortieri podrían competir por recursos.The effect of seed density on the germination of 2 columnar cactus species (Isolatocereus dumortieri and Myrtillocactus geometrizans) was evaluated using 5 seed density treatments (1, 5, 10, 20 and 50 seeds). Isolatocereus dumortieri had a lower germination percentage with increasing seed density; germination of M. geometrizans was not affected by seed density. These results suggest that I. dumortieri seedlings might compete for resources with siblings.

Los bosques naturales de Pinus tropicalis Morelet en Cuba han sido alterados por prácticas inadecuadas de aprovechamiento forestal. Esta investigación tiene el objetivo de caracterizar la estructura de un bosque perturbado de Pinus tropicalis en Galalón, Pinar del Río. Para ello se realizó un inventario florístico, se determinaron los índices de valor de importancia ecológica y de importancia ecológica ampliado. Se calculó la diversidad alfa mediante el recíproco del índice de Simpson (1/D) y el índice de Jackknife, así como la diversidad beta por medio de Morisita-Horn y Jaccard. Se evaluó el grado de perturbación del área mediante indicadores de cambios en el ecosistema. Se identificaron un total 22 familias, 30 géneros y 31 especies. Los parámetros estructurales indicaron que las especies de mayor importancia ecológica son P. tropicalis, P. caribaea var. caribaea y Byrsonima crassifolia. La diversidad florística se calificó de baja y la similitud resultó en tres grupos diferenciados por su composición florística.

Semiarid grasslands in northeastern Mexico contain many endemic plants and animals and are an important refuge for resident and migratory animals. Here, as in many other semiarid areas, biological soil crusts are a key component of the ecosystem. However, findings about their effect on the germination of vascular plants are in contrast. We asked whether germination of some native plant species would be inhibited by the presence of biological soil crusts as it has been found in other studies and evaluated the effect of seven dominant biological soil crusts: Psora cerebriforme (W.A.Weber), Psora decipiens (Hedwig) Hoffm., Placidium sp., Endocarpom pussillum (Hedwig), Xanthoparmelia chlorochroa (Tuck.) Hale, Nostoc commune (Vauch), and Oxymitra sp. from the area, on the germination percentage and germination rate of three native plant species: Frankenia gypsophila (I.M.Johnst.), Muhlenbergia arenicola (Buckl.), and Sartwellia mexicana (A.Gray). Germination tests were carried out in an environmental chamber at 26 °C and at a constant humidity of 60% with 12 hours by 12 hours light and darkness. Biological soil crusts did not affect germination percentage of the three evaluated plant species when compared to bare soil. Germination rate ranged between 3.5 and 5 days and there were no differences between substrates.

Most Lupinus spp. (Fabaceae) grow in pine and pine-oak forests with natural and induced fires, and their seeds have physical dormancy, which could be broken in response to appropriate environmental signals, such as high temperatures, humidity and fire. We applied heat treatments to break seed dormancy of L. elegans and L. rotundiflorus from the State of Jalisco, México, with different storage times (0, 1 and 2 yr for L. elegans and 0, 1, 2, 3 and 4 yr for L. rotundiflorus). Seeds were immersed in boiling water for 5, 10, and 15 s and incubated in wet and dry sand at 100 °C, 120 °C, and 150 °C during 60 min and 90 min. Germination trials were set at 25 °C with 12 h of irradiance per day. For both species, no germination resulted after incubation at 120 °C and 150 °C. For L. rontundiflorus, germination was higher for seeds incubated in wet sand for 60 m than for those incubated for 90 m. After scarification with boiling water, fresh seeds of L. elegans, germinated more than those stored for 1 and 2 yr, whereas incubation in wet and dry sand resulted in higher germination for 1 and 2 yr old seeds than for fresh seeds. Fresh seeds of L. rotundiflorus showed higher germination than stored seeds across treatments. Our results may be useful for further studies to understand and predict ecological plant responses in Mexican forests.

Se estudiaron características fisiológicas y morfológicas de plántulas de especies leñosas (nodrizas) y suculentas (protegidas), las cuales se distribuyen en un gradiente ambiental en el Altiplano Mexicano. Del extremo mésico se eligieron Acacia schaffneri, A. farnesiana y Opuntia jaliscana y, del extremo xérico se escogieron A. schaffneri, Prosopis laevigata y O. streptacantha. En un experimento en invernadero, plántulas de 24 semanas de edad fueron sometidas por 90 días a diferentes niveles de radiación (alta = 2133 μmol m-2d-1, baja = 66 μmol m-2d-1), humedad aprovechable (alta = 60%, baja = 30%) y fertilidad (alta = suelo debajo de dosel, baja = suelo de área abierta). Las variables de respuesta evaluadas fueron la tasa relativa de crecimiento y sus componentes: morfológico (el cociente del área fotosintética) y fisiológico (la tasa de asimilación neta); así como la eficiencia cuántica del fotosistema II (ΦPSII) y la tasa de transporte de electrones. Las plántulas de suculentas presentaron mayor tasa relativa de crecimiento y cociente del área fotosintética que las plántulas de leñosas. La mayoría de las especies crecieron más en radiación y humedad altas. El suelo debajo de dosel favoreció el crecimiento de las suculentas, pero las leñosas presentaron los valores de la tasa de asimilación neta más altos. Los resultados sugieren que las plántulas de suculentas tienen mejor desempeño ecofisiológico para establecerse debajo del dosel de plantas nodrizas, y que las de leñosas presentan características ecofisiológicas de especies nodrizas mejor adaptadas a espacios abiertos.

Cacti establish mostly occurs under the canopy of nurse plants which provide a less stressful micro-environment, although mechanisms underlying this process are unknown. The impact of the combination of light and watering treatments on Opuntia streptacantha (Cactaceae) seedlings was examined.Ecophysiological [titratable acidity, osmotic potential ('solute potential', Ψs ), relative growth rate (RGR) and their components (NAR, SLA, and LWR)], anatomical (chloroplast density, chloroplast frequency, and cell area), and environmental [photosynthetic photon flux density (PPFD) and air temperature] sets of variables were analyzed, assessing relationships between them and measuring the intensity of the relationships. Three harvests were carried out at days 15, 30, and 45. Ψs and acidity content were the most important responses for seedling establishment. The main anatomical and environmental variables were chloroplast density and water availability, respectively. Opuntia streptacantha seedlings establish better in the shade-watering treatment, due to higher Ψs and acidity, unaffected chloroplasts, and lower PPFD. In addition, the chloroplasts of cells under high-light and non-watering treatment were clumped closer to the center of the cytosol than those under shade-drought, to avoid photoinhibition and/or to better distribute or utilize the penetrating light in the green plant tissue.Opuntia seedlings grow better under the shade, although they can tolerate drought in open spaces by increasing and moving chloroplasts and avoiding drastic decreases in their Ψs . This tolerance could have important implications for predicting the impact of climate change on natural desert regeneration, as well as for planning reforestation-afforestation practices, and rural land uses.

We investigated if seeds of Agave lechuguilla from contaminated sites with heavy metals were more tolerant to Cd ions than seeds from noncontaminated sites. Seeds from a highly contaminated site (Villa de la Paz) and from a noncontaminated site (Villa de Zaragoza) were evaluated. We tested the effect of Cd concentrations on several ecophysiological, morphological, genetical, and anatomical responses. Seed viability, seed germination, seedling biomass, and radicle length were higher for the non-polluted site than for the contaminated one. The leaves of seedlings from the contaminated place had more cadmium and showed peaks attributed to chemical functional groups such as amines, amides, carboxyl, and alkenes that tended to disappear due to increasing the concentration of cadmium than those from Villa de Zaragoza. Malformed cells in the parenchyma surrounding the vascular bundles were found in seedlings grown with Cd from both sites. The leaves from the contaminated place showed a higher metallothioneins expression in seedlings from the control group than that of seedlings at different Cd concentrations. Most of our results fitted into the hypothesis that plants from metal-contaminated places do not tolerate more pollution, because of the accumulative effect that cadmium might have on them.

En los pastizales del norte de México se han introducido gramíneas de origen africano, con el propósito fundamental de controlar la erosión del suelo e incrementar la productividad. Estas especies en lo general exhiben mayor talla y mayor producción de semilla, por lo que existe el riesgo, en caso de su naturalización, de que desplacen a las especies nativas. La invasión de ecosistemas semiáridos por estas especies exóticas ocasiona múltiples problemas, por lo que es fundamental identificar con anticipación los mecanismos que contribuyen a su propagación. En ensayos con condiciones controladas se trabajó con las gramíneas nativas Bouteloua gracilis y B. curtipendula así como las exóticas africanas Eragrostis curvula, E. lehmanniana, E. superba, Melinum repens y Panicum coloratum. El estudio examinó la germinación de semillas y la asignación de biomasa en plántulas, en condiciones de esterilización de semilla y suelo (semilla lavada y no lavada más suelo esterilizado y no esterilizado). En el presente estudio solamente E. superba superó los porcentajes de germinación (P

A total of six species of pelagic shrimps were collected during the TALUD XIV cruise aboard the R/V "El Puma", in the northern Gulf of California, in April 2011, including two species of Dendrobranchiata [Eusergestes similis (Hansen, 1903) and Sergia phorca (Burkenroad, 1940)], and three species of Caridea [Pasiphaea americana Faxon, 1893, P. emarginata Rathbun 1902, and P. pacifica Rathbun, 1902]. Additional specimens of the previously reported Maryprocessa pippinae (Wicksten & Méndez, 1985) were also found among the samples. Most frequently collected species were P. americana (50% of total) and P. pacifica (36.6%). Most numerous species in the samples were P. pacifica, P. americana and E. similis. Some minor morphological differences not previously recorded in specimens of Pasiphaea pacifica collected elsewhere were detected. These differences might correspond to an intraspecific variation.