Abstract

BENAVIDES-MARTINEZ, Iván F.; BURBANO-MARTINEZ, Diana L.; URBANO-APRAEZ, Sandra M.  and  SOLARTE-CRUZ, María E.. THE EFFECT OF THE ALTITUDINAL GRADIENT ON AUTOECOLOGICAL FEATURES OF ESPELETIA PYCNOPHYLLA ssp. ANGELENSIS CUATREC. (ASTERACEAE) IN THE PARAMO 'EL INFIERNILLO' (NARIÑO-COLOMBIA). Actu Biol [online]. 2007, vol.29, n.86, pp.41-53. ISSN 0304-3584.

Some autoecological features of Espeletia pycnophylla ssp. angelensis Cuatrec. such as its demographic structure, population density, spatial pattern of dispersion, production of reproductive structures, adult morphometry and survivorship, were studied in an altitudinal gradient on a dry paramo of Nariño (Colombia). Hypothesis proposed by other authors about a linear effect caused by the elevation on these variables were completely rejected. The elevation induces an ecoclinal effect on population density, and this density correlates negatively with both production of reproductive structures and adult sizes. These results elucidate an unequivocal effect of density-dependence phenomena on population fitness. The intermediate zone of the altitudinal gradient exhibits a high population density, but on the other hand show reduced corporal adult sizes, minimal production of reproductive structures and the probability of juveniles reaching advanced ages is low. Evidently, this intermediate elevation can have favorable ecological conditions for the seedling establishment, wich increments population densities at long term. We propose that other author's generalizations about the influence of elevation on the autoecology of these plants are limited, because the particular life and disturbance stories of paramos and the spatial, ecological and genetic isolating are explicative factors impossible to take away from the context. The demographic structure of the population fitted the logarithmic model, revealing its early regeneration state from the last fire event on 2003 and the similarity of the survivorship curves among every elevation, probed a high demographic stability.

Keywords : autoecology; Espeletia pycnophylla ssp. angelensis; altitudinal gradient; Nariño; paramo.

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