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Taxus globosa es una conífera poco estudiada desde el punto de vista biológico, ecológico y reproductivo. Importante por la sustancia química que produce llamada taxol, útil en el tratamiento de cáncer de ovario y de mama, principalmente. En México está catalogada como especie Sujeta a Protección Especial en la Norma Oficial Mexicana NOM-059-SEMARNAT-2010, lo que implica que podría estar amenazada por factores negativos que inciden en su distribución, desarrollo y regeneración. En el ámbito internacional, se incluye en la lista roja de especies amenazadas de la Unión Internacional para la Conservación de la Naturaleza (UICN) como especie en peligro de extinción. Por lo anterior, es necesario conocer la situación que guardan las poblaciones naturales en su intervalo de distribución natural y comprender sus mecanismos de regeneración y propagación, para el desarrollo de tecnologías que permitan su domesticación y producción. En la presente revisión se recopiló la información existente acerca de T. globosa en México, se expone la distribución actual y potencial; además de revisar las condiciones de las poblaciones en cuanto a la asociación con otras especies vegetales, densidad de individuos adultos y juveniles, aspectos de regeneración, y en consecuencia del estado de conservación de las poblaciones. Con la finalidad de identificar líneas de investigación particulares de este recurso forestal que contribuyan a su conservación y aprovechamiento sustentable.

In Mexico, there is a knowledge gap on plant mortality and health of tropical forest plantations. Therefore, a provenances test of Enterolobium cyclocarpum was established in two sites (Pinotepa de Don Luis and Valdeflores) in the coastal region of Oaxaca, Mexico to determine the mortality factors and biotic agents related to the health of this specie. Mortality and plant health were recorded during 18 months; also, differences between sites and between provenances were determined. Orthogeomys grandis (pocket gopher) in Pinotepa de Don Luis (27.9 %) and drought (29.2 %) in Valdeflores caused higher plant mortality. Powdery mildews (Oidum), aphid (Aphis), cottony cochineal (Pseudoccocus longispinus), twig girdlers (Oncideres), borer (Lepidoptera) and defoliator (Lepidoptera) were the biotic agents related to health of E. cyclocarpum. The powdery mildews and the aphids infected the highest number of plants; in Pinotepa de Don Luis, the powdery mildews and the aphids infected 58.8, 29.2 % of the plants, respectively; whereas, in Valdeflores, the powdery mildews and aphids infected 3.3 % and 0.8 % of the plants, respectively. In Pinotepa de Don Luis, plants from Cortijo and Colotepec had the lowest powdery mildews infection, and the aphid infestation was not different in plants between provenances. In Valdeflores, plants from five provenances were free of powdery mildews infection, and the aphids only infested plant from the El Zarzal provenance. The location and precipitation of the sites influenced the levels mortality and infection of E. cyclocarpum plants.

ResumenLa mariposa Eumaeus toxea es un herbívoro que se alimenta de Zamia paucijuga, una cícada considerada amenazada y vulnerable, con una tendencia a la disminución y desaparición de sus poblaciones. Los objetivos del presente trabajo fueron determinar la distribución geográfica de la mariposa, la duración de su ciclo biológico, su supervivencia y reproducción en su hospedante natural en condiciones de campo, en la provincia fisiográfica Costa de Oaxaca. El trabajo se realizó durante el periodo de junio de 2010 a mayo de 2011. La distribución de la mariposa fue coincidente con la distribución de su hospedante. Empleando la técnica de tablas de vida con decrementos simples y agrupados por estadios, se requirió 47±0.5 días a la urgencia del adulto, un tiempo generacional de 51 días, una supervivencia de 0.027 hasta la urgencia del adulto con una mortalidad del 28.4% para el estadio de huevo y del 68.8% para el estadio de larva; con una tasa de reproducción neta de 0.014. Por su especificidad con el hospedante, baja densidad poblacional y tasa neta de reproducción, la conservación E. toxea depende de la preservación de su hospedante y del dosel arbóreo donde sobreviven sus poblaciones.AbstractThe butterfly Eumaeus toxea is an herbivore that feeds on Zamia paucijuga, an endangered and vulnerable cycad with their populations trending to decline and disappear. The objectives of this study were to determine the geographic distribution of the butterfly and to determine the duration of their life cycle, as well as its survival and reproduction rate when reared with its natural host under field conditions in the physiographic province of Oaxaca Coast. The work was conducted during the period of June 2010 to May 2011. Butterfly distribution coincided with the distribution of their host. Using the technique of single decrement and abridged life table by stages, 47±0.5 days were required for adult emergence, a mean generation time of 51 days, a survival rate of 0.027 to adult emergence with a mortality of 28.4% for the egg stage and 68.8% for the larval stage, and a net reproductive rate of 0.014. Due to the host specificity, low population density and net reproduction rate, the conservation of E. toxea depends on the preservation of its host and the canopy where their populations survive.

Dioon holmgrenii is an endangered species and found in Southern Oaxaca, Mexico. Notwithstanding the extintion condition of this species, there is no relevant information on the ecological aspects of its populations, and this situation complicates the approval of management plans for its conservation. Our aim was to study D. holmgrenii forest characteristics, population structure and life-stages diversity in ten populations located in Sierra Madre del Sur, Oaxaca. For this, four sampling units (SU) measuring 25 x 50 m each (1 250 m2) were established per population, 40 SU in total (50 000 m2). Basal diameter (BD), basal area (BA), stem height (AT), crown diameter (DC), crown area (AC), and number of leaves (NH), were measured for each individual, from January to May 2013. Additionally, plant density, population structure, structural dominance index (IDE), heterogeneity (H'), evenness (E) and similarity (ISct) of life-stages (seedling, juvenile 1, juvenile 2, pre-reproductive, adult 1, adult 2, adult 3, and adult 4) were assessed. Plant density ranged from 148 to 954 individuals ha-1. Total basal area ranged from 1.3 to 17.6 m2.ha-1, and total crown area varied from 78.3 to 1 136.3 m2.ha-1. Forest traits of each individual (DB= 7.7 to 13.4 cm, AB= 0.010 to 0.023 m2, AT= 0.20 to 0.47 m, DC= 0.49 to 1.09 m, AC= 0.55 to 1.55 m2 and NH= 7.06 to 14.90) were different (p˂0.05) among populations. The highest values of IDE (0.01 to 5.63) were found in adult 1 and adult 2 in all populations. The most common population structure was found in those populations with the lowest proportions in juvenile 1 and juvenile 2, and the highest proportion in adult 1. Heterogeneity (H'= 1.05 to 1.71) and uniformity (E= 0.57 to 0.88) of life-stages were significantly different among populations (p˂0.05), and at least four life-stages (3.91= 48.9x8/100) were different among populations for half of the comparisons (22 of 45) of similarity (ISct < 0.68). Alfa diversity of life-stages was high in populations without plant damage, while beta diversity was low in those populations with human presence. Life-stages with the highest reproductive vigour (adult 1, adult 2) showed the highest structural dominance in all populations. These results may support the design and operation of management plans of D. holmgrenii populations, to enhance its protection in the area.