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

One of the objectives of the Sierra de Manantlan Biosphere Reserve (Jalisco , Mexico) is the conservation in situ of the teosinte Zea diploperennis Ilt is, Doebley, Guzman & Pazzi. Zea diploperennis is perennial, shade intolera nt and its 1-3 in shoots are architecturally similar to maize. Clonal growt h is of the phalanx type. Genets are iteroparous (modules semelparous). The demography of seven module and genet populations was Studied in seven site s representing three stages of old-field succession. Seven permanent one-me ter-square plots were randomly established in each site. Ail genets initial ly present and those that became established during our study were mapped a nd labeled according to year of establishment The magnitude of demographic fluctuations was greater in module populations. Genet population dynamics f ollowed a seasonal rhythm with a maximum population size obtained at the on set of the rainy season. A relation was documented between percent annual m ortality of a cohort and its age: the younger the cohort, the greater the m ortality. This was a statistically significant relationship, Y = [sin (-0.2 88x + 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 mortali ty 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 popul ation 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 diploperen nis. Such rehabilitation would achieve two distinct objectives, promote pro pagation of this rare endemic and reclaim areas that are susceptible to ero sion and further degradation.