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Background and Aims: Cedrela odorata (Spanish cedar) is a tropical tree native to America with an important international trade market. In this study, the morphological variation of C. odorata was compared among three conditions: logging, plantations, and natural populations, with the objective to evaluate the current condition of managed populations after harvesting and in plantations, in contrast to relatively well-preserved populations.Methods: Two sites were chosen for each condition. The population density and four morphological attributes were measured: diameter at breast height, height, angle of branch insertion and crown form. A multivariate approach was used to compare the morphological variation among conditions (generalized discriminant factors analysis) and determine total variation distributed among size classes (cluster analysis), as well as assignment of these classes to each condition (canonical correspondence analysis).Key results: Four significantly different size classes were identified among all populations with specific association to condition. Strongest correlations were between highest trees with natural populations and small trees with plantations. Forest management, including harvesting and plantation conditions, reduced the phenotypical variation and modified the dasometrical attributes of C. odorata. The logging of the better shaped phenotypes increased the smaller size trees frequency compared to commercial size individuals, and changed the forest composition favoring small categories.Conclusions: The forest exploitation generates homogenization in median height-class and the plantation in lower height-class. In both cases, the harvestable trees are scarce, even after 20 years of management; and they are non-existent in plantations of 15 years. These results suggest that the removal of the highest trees, as well as forest plantations, are not being effective to wood production since they do not reach commercial sizes in the time of recovery or projected growth.

Platanus mexicana is a dominant arboreal species of riparian ecosystems. These ecosystems are associated with altitudinal gradients that can generate genetic differences in the species, especially in the extremes of the distribution. However, studies on the altitudinal effect on genetic variation to riparian species are scarce. In Mexico, the population of P. mexicana along the Colipa River (Veracruz State) grows below its reported minimum altitude range, possibly the lowest where this tree grows. This suggests that altitude might be an important factor in population genetics differentiation. We examined the genetic variation and population structuring at four sites with different altitudes (70, 200, 600 and 1700 m a.s.l.) using ten inter-simple sequence repeats (ISSR) markers. The highest value for Shannon index and Nei’s gene diversity was obtained at 1700 m a.s.l. (He = 0.27, Ne = 1.47, I = 0.42) and polymorphism reached the top value at the middle altitude (% p = 88.57). Analysis of molecular variance (AMOVA) and STRUCTURE analysis indicated intrapopulation genetic differentiation. The arithmetic average (UPGMA) dendrogram identified 70 m a.s.l. as the most genetically distant site. The genetic structuring resulted from limited gene flow and genetic drift. This is the first report of genetic variation in populations of P. mexicana in Mexico. This research highlights its importance as a dominant species, and its ecological and evolutionary implications in altitudinal gradients of riparian ecosystems.

Antecedentes: Con base en caracteres morfológicos de hojas, flores y frutos se han segregado nuevas especies del complejo Magnolia mexicana en México. Por su importancia evolutiva, ecológica y de uso medicinal es relevante analizar la variación morfológica y conocer el estado actual de sus poblaciones en su área de distribución. Preguntas: ¿Existe diferenciación en la morfología de hojas, flores y frutos en las poblaciones de M. mexicana? ¿Cuál es el estado actual de las poblaciones de M. mexicana? Especie de estudio: Magnolia mexicana (DC.) G. Don (Magnoliaceae). Sitios y años de estudio: El estudio se realizó en seis poblaciones de M. mexicana en la Sierra Madre Oriental, entre mayo y octubre de 2019 y 2020. Métodos: Se analizaron 480 hojas, 240 flores y 84 frutos mediante análisis univariados y multivariados. Resultados: Los primeros componentes principales explicaron 85, 69 y 68 % de la variación foliar, floral y frutal, respectivamente; y las primeras 2 funciones discriminantes 82, 66 y 94 % de dicha variación. Los caracteres morfológicos con mayor variación fueron: diámetro del peciolo y  vena media, número de estambres, ancho de carpelos, y largo y ancho de semillas. Conclusiones: El rango de variación en las características morfológicas de M. mexicana fue más amplio que el documentado en la descripción original de la especie. Las poblaciones están aisladas y presentan baja densidad y alta diferenciación morfológica entre sí, en particular en flores y frutos, por lo que su identidad taxonómica requiere ser corroborada a nivel genético.