Resumen: Se estudiaron características fi siológicas 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

<p><em>Magnolia pugana</em> 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^-1y (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 &lt; 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.</p>

39 especies herbáceas fueron sembradas en suelos degradados del bosque La Primavera, con dos tratamientos, 1: siembra con todas las especies y 2: siembra con las fabáceas y 15 días después se agregó el resto de las especies, en parcelas de 1 m-2. Con Análisis de Varianza (Anova) analizamos cobertura, densidad y tasa de crecimiento (cociente del área foliar y tasa de asimilación neta). La Dalea leporina registró la cobertura más alta y la Cosmos bipinnatus la mayor densidad. Las asteráceas registraron el crecimiento más alto. Desmodium sericophyllum y D. aparines mostraron el cociente del área foliar más alto y Cosmos bipinnatus la tasa de asimilación mayor. La presencia de otras especies no afectó la densidad ni el crecimiento de las fabáceas; además, mostraron ajustes morfológicos y fisiológicos con ventajas competitivas para establecerse en suelos degradados, por lo que son la mejor opción para iniciar procesos de sucesión vegetal para restaurar suelos en La Primavera.

Numerous Neotropical Magnolia species are endangered and red-listed by the IUCN. Here we highlight major results from over a decade of research on endangered magnolias in western Mexico. Particularly, we compare three species of Magnolia (M. pugana, M. pacifica and M. vallartensis) along a large-scale continentality and moisture gradients, in terms of a) their morphological adaptations, b) genetic structure, diversity, and differentiation, c) reproductive phenology, and d) floral scents and their floral visitors. Fieldwork along this gradient unveiled two new species of Magnolia sect. Magnolia; M. granbarrancae and M. talpana. We found that most continental populations have a higher extinction risk than those with greater maritime influence, due to their lower genetic diversity, and greater fragmentation, isolation, and water stress. Also, these populations are more vulnerable to the environmental conditions predicted with the global warming climate scenarios. We share fieldwork experience and advise on pre-germination treatments and seed dormancy. We propose an ex-situ and in-situ conservation strategy, identify new challenges, and suggest future directions of collaborative work as a global Magnolia conservation consortium.

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The aim of this study was to describe morphological variations of Opuntia jaliscana in 5 wild populations in the state of Jalisco (Mexico). Populations were selected along an environmental aridity gradient, and 61 vegetative and reproductive characters from 25 individuals were measured per population. Quantitative characters were analyzed independently by a one-way ANOVA test using the site as variation factor. Subsequently, a discriminant analysis was performed. The discriminant analysis results showed that the 46% of the total variation was explained by the first four discriminant functions. The analysis of overall membership between populations indicated that individuals were correctly classified in 87% of cases. Pearson linear correlation between the most significant variables and the aridity index, showed a positive relationship to cladode thickness and diameter of the trunk. The population from Tierra Blanca shows an outlier behavior because of variation in cladode thickness and fruit size, which might be related to plasticity of individuals to have a greater availability of water, while in Los Vallejo the separation might be due to selection by management and use. The remaining populations exhibited some morphological variability without separation.

Relative growth rate in Magnolia pugana (Magnoliaceae) seedlings from two populations at different light levels and soil fertility. The study of ecophysiology of endangered species is key to the success of conservation and ecological restoration programs. The objective of this work was to know the effect of light, soil fertility and seed origin on the growth of Magnolia pugana seedlings. The relative growth rate (RGR) and its components (Net Assimilation Rate: NAR and Leaf Area Ratio: LAR), as well as the root-shoot ratio (R/S) were estimated. Seedlings were obtained from seeds collected in two localities in Zapopan, Jalisco, Mexico, the first is a wild population in San Nicolás (SN) and the second is a plantation located in the gardens of the Centro Universitario de Ciencias Biológicas y Agropecuarias (CUCBA). The experiment was conducted under greenhouse conditions. In September 2015, 96 seedlings of approximately three months old were subjected to the following treatments in a factorial experiment (2x2x2): light level (high = 1 120 μmol m-2 s-1 and low = 136.3 μmol m-2 s-1), seedling origin (SN and CUCBA) and soil fertility (high fertility = SN soil, low fertility = CUCBA soil) with 12 replicates for each combination of factors and levels. Growth was estimated in two harvests: the first harvest after 30 days of starting the experiment and the second at 60 days. Light and soil fertility levels, as well as seedling origin influenced growth through physiological and morphological adjustments. In general, Magnolia pugana showed higher RGR and NAR in high light, while LAR decreased. Soil fertility and seedling origin did not affect RGR or its components. However, these were affected by the light level, seedlings from SN grew more in high light. Stem height varied due to soil fertility and seedling origin, in low fertility soil (CUCBA) the seedlings of SN were 35 % higher than those of CUCBA. Low fertility soil under high light caused greater investment in seedling root biomass. The physiological component (NAR) was the major determinant of intraspecific variation in RGR. SN seedlings showed greater phenotypic plasticity due to coming from a wild population, which possibly has higher genetic variation than the cultivated population from CUCBA. The results suggest that Magnolia pugana is a species capable of adapting to diverse environments due to its phenotypic plasticity in response to different light and soil fertility levels. Rev. Biol. Trop. 66(2): 622-633. Epub 2018 June 01.

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