Variações fenotípicas em espécies lenhosas do Cerrado em três áreas no Triângulo Mineiro

Abstract

This work describes the phenotypic variation in leaf morphologies and height for eight woody species of the "Cerrado" vegetation in three areas of the Triângulo Mineiro, (MG, Brazil). The analyzed species were: Acosmium dasycarpum (Vog.) Yak. (Leguminosae-Papilionoideae), Byrsonima crassa Nied. (Malpighiaceae), Caryocar brasiliense Camb. (Caryocaraceae), Davilla elliptica St. Hill. (Dilleniaceae), Matayba guianensis Aubl. (Sapindaceae), Miconia fallax DC. (Melastomataceae), Qualea parviflora Mart. (Vochysiaceae) and Roupala montana Aubl. (Proteaceae). The three collection sites possess different edaphic and vegetation physiognomic patterns: a cerrado strictu senso on a red dystrophic latosoil (area 1); a cerradão on lytolic eutrophic neosoil (area 2), both near Araguari; and a cerradão on a red dystrophic latosoil near Uberlândia (area 3). For M. guianensis and M. fallax variations in reproductive structures (seeds and fruits) of plants that grew in the areas 1 and 3 were also described. Ecotypes were recognized by differences in the length of the petiole, size and shape of the leaf, and plant height. In the cerradão (area 3) most of the analyzed individuals presented larger and more elongated leaves, with a longer petiole. Significant positive correlations were detected between leaf area and petiole length for all analyzed species, indicating an integrated genetic regulation mechanism determining phenotypic expression of those characters. It is suggested that the morphologic plasticity observed in the leaf characters maximizes the light reception, and therefore, could also be considered adaptive. Only three species differed significantly between the studied areas in their indices of fluctuating asymmetry (FA), which is considered one of the best means of quantifying the instability of the development under conditions of genetic or environmental stress. The patterns of FA variation found for these three species were dissimilar in the studied areas, contrary to the tested hypothesis that predicts lower foliar FA values in plants that grow in more fertile soils. No significant correlations between FA and leaf size, leaf elongation or plant height were found, suggesting lack of a linear pattern of variation for these characters. It is argued that the great plastic potential for adjustments in leaf size and shape as well in other plant traits is buffering the adverse conditions and minimizing the developmental instability. FA in leaves does not seem to be appropriate for monitoring nutritional edaphic stress of "Cerrado" vegetation, considering the great ability of the plants to control their development under adverse conditions. M. fallax and M. guianensis presented different patterns of variation of the reproductive structures in the studied areas, possibly related to dispersion of seeds and to increase fitness.