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Background: Reproductive traits are features of a species’ biology that may determine its rarity, as they affect its genetic diversity and structure, as well as its population dynamics. Study species: The rare and threatened species Furcraea parmentieri, whose distribution is limited to the Trans-Mexican volcanic belt. Questions: How is the reproductive phenology of F. parmentieri? Does flower morphology vary between individuals? Does it produce nectar? Which animals visit its flowers? Is it self-compatible? Do the seeds originated via different pollination treatments show differences in their germinability? Study sites and dates: We studied the F. parmentieri from 2007 to 2008, at El Xitle volcano (altitude: 2800 – 3100 m; pine-oak forest), in the south of Mexico City. Methods: Reproductive phenology was recorded through fortnightly visits to the study site. Flowers were collected, flower visitors were recorded and nectar production was measured. An experiment was done which included four treatments: autonomous pollination, geitonogamy, cross pollination, and a control. We measured seed set, fruit set and seed germination in each treatment. Results: Inflorescences started in January and flowering finished in May. Fruit maturation took from May to November. Nectar production was negligible. Flowers were visited by hawkmoths and hummingbirds. Fruit set was very low (ca. 5 %) and we observed self-incompatibility. Conclusions: Fucraeae parmentieri presents a low fruit set due to pollinator limitation. However the population seems to be thriving. The main threat faced by this species is the high land-use change rate along its distribution range, as well as climate change.

We studied the demography of two populations of Agave angustifolia, one in a preserved tropical dry forest (Xochicalco), and the other one in a pastureland area used for cattle grazing (Tembembe), to test whether populations are likely to thrive on the deteriorated habitats left after cattle ranching. Seed germination and seedling survival experiments were carried out in different natural microsites (i.e. under tree canopies and in open microsites). We built Lefkovitch matrices and carried out prospective (elasticity) and retrospective (Life Table Response Experiments) analyses for both populations. Numerical simulations were performed to project the effect of inflorescences harvest and seedling introduction. Seedling survival and seed germination were highest in Tembembe. Population growth rate was slightly higher in Tembembe (lambda =1.268) than in Xochicalco (lambda =1.208). Prospective and retrospective analyses showed that stasis and growth contributed most to population growth rate and that the differences between the two populations were accounted for a lower fecundity and stasis in Xochicalco compared to Tembembe. Simulations of inflorescence harvest showed that lambda dropped below unity only when all inflorescences were eliminated. The simulated introduction of seedlings produced a substantial rise in lambda. As the lambda values reflect thriving populations at both sites, we suggest that this species could be successfully used in restoration programs.

Se estudió la demografía de nueve poblaciones de la epífita Tillandsia recurvata establecidas sobre Prosopis laevigata en la región de Tehuacán, Puebla, para evaluar si existía asincronía demográfica entre ellas, condición fundamental para la persistencia de una metapoblación. Estas poblaciones diferían en términos del tamaño del árbol (volumen de la copa) y de su número de individuos. Se construyeron dos matrices de Lefkovitch por población, una para 2001-2 y otra para 2002-3. Las estructuras poblacionales difirieron entre poblaciones: la proporción de plántulas fue mayor en los árboles pequeños, mientras que en los árboles grandes se observó una mayor proporción de adultos. Los valores de ? variaron entre poblaciones y entre años, pero no mostraron ningún patrón claro de variación. Se encontró una correlación positiva entre ? y el tamaño poblacional, pero sólo para 2002-3. Las poblaciones estudiadas mostraron un comportamiento demográfico asincrónico, favoreciendo la persistencia de la metapoblación.

Se abordó experimentalmente el estudio de la respuesta germinativa y el crecimiento de plántulas de Mammillaria magnimamma. Se determinó el porcentaje final de germinación y la velocidad de germinación de las semillas bajo diferentes condiciones de luz/oscuridad, temperatura y pretratamientos de acidez. Las semillas son fotoblásticas positivas y su viabilidad es alta (86%); el requerimiento de luz disminuyó al aumentar la edad de las semillas. La variación en la temperatura afectó la velocidad de germinación y los pretratamientos de acidez no tuvieron un efecto significativo sobre la germinación. Se estudió el crecimiento de plántulas de esta especie en condiciones de invernadero bajo un diseño factorial que incluyó dos niveles de luz, dos de disponibilidad de nutrimentos y dos de frecuencia de riego. Las plántulas son de crecimiento lento (entre 0.014 y 0.027 g g-1 d-1) y responden positivamente a la adición de nutrientes y a los niveles elevados de exposición lumínica.