Population structure and ecology of a tropical rare rhizomatous species of teosinte Zea diploperennis | Population structure and ecology of a tropical rare rhizomatous species of teosinte Zea diploperennis (Gramineae)

Inglés. One of the objectives of the Sierra de Manantlán Biosphere Reserve (Jalisco, México) is the conservation in situ of the teosinte Zea diploperennis Iltis, Doebley, Guzman & Pazzi. Zea diploperennis is perennial, shade intolerant and its 1-3 m shoots are architecturally similar to maize. Clonal growth is of the phalanx type. Genets are iteroparous (modules semelparous). The demography of seven module and genet populations was studied in seven sites representing three stages of old-field succession. Seven permanent one-meter-square plots were randomly established in each site. All genets initially present and those that became established during our study were mapped and labeled according to year of establishment The magnitude of demographic fluctuations was greater in module populations. Genet population dynamics followed a seasonal rhythm with a maximum population size obtained at the onset of the rainy season. A relation was documented between percent annual mortality of a cohort and its age: the younger the cohort, the greater the mortality. This was a statistically significant relationship, Y=[ sin(-0.288x + 1.657)]2 (r = 0.92, p < 0.01), where is proportion annual mortality of genets and is the age of the cohort. The maximum rates of genet mortality occurred during the rainy season when population densities were greatest. As a consequence, we postulate that competition occurs principally during the rainy season. Linear relationships were observed between rate of population increase of genets versus old-field successional stage and soil type. Those areas with poor soil (Ultisol), degraded soil or soils with similar physical characteristics could be rehabilitated by introducing Z. diploperennis. Such rehabilitation would achieve two distinct objectives, promote propagation of this rare endemic and reclaim areas that are susceptible to erosion and further degradation.

Español; castellano. Se estudió la demografía de Zea diploperennis en siete sitios de cultivo abandonados. La magnitud de las fluctuaciones demográficas fue más grande en las poblaciones de módulos. La dinámica de las poblaciones de genets siguió un ritmo estacional con un tamaño máximo de la población al inicio de la temporada de lluvias; las cohortes más jóvenes presentan la más alta mortalidad, i. e., Y = [sin (–0.288x + 1.657)]2, (r = 0.92, p < 0.01), donde es la proporción de la mortalidad anual y es la edad de la cohorte. La máxima tasa de mortalidad de genets ocurrió durante la temporada de lluvias cuando la densidad de la población fue más alta, cuando la competencia parece mayor. Hubo relaciones lineales entre la tasa de incremento de genets y el estado sucesional y el tipo de suelo. Aquellas áreas con suelos pobres degradados o suelos con similares características, pueden ser rehabilitados introduciendo Z. diploperennis, protegiéndola y combatiendo la degradación del suelo.