Distribution of Adult Male and Female Baccharis concinna (Asteraceae) in the Rupestrian Fields of Serra Do Cipó, Brazil

Abstract

This study focuses on the sex ratio and spatial distribution of males and females in three populations of the endemic and restricted tropical dioecious shrub, Baccharis concinna (Asteraceae) in the mountainous region of Serra do Cipó, southeastern Brazil. The proportion of female plants in the population at lower elevation (1000 m a.s.l.) was significantly greater than of male plants. At this elevation of P/N and Ca/Al ratios in the soil were also greater indicating better nutritional status of the soils. The concentration of aluminium increased significantly with the elevation (p < 0.001), perhaps rendering soils less conducive to female plants at higher elevations. Female plants are possibly adversely affected to a greater extent by soil quality than male plants. The spatial distribution of the populations within habitat was tested by the K(t) function, where the neighbourhood of a given individual was defined by a circle with a radius (t) up to 3 m. Despite the strong tendency for aggregation, the distribution of the sexes within habitats was random and the hypothesis was not supported. The independent distribution of the sexes within habitats may be explained by nutrient homogeneity of the soils, as well as by an absence of antagonism between the sexes. Nevertheless, we found a trend for males and females to be aggregated according to their gender.

Unexpected effects of pigeon-peas (Cajanus cajan) in the restoration of rupestrian fields

“…Although the amount of organic matter was not analyzed in the present study, the amount of nitrogen between the two treatments did not differ statistically. The quantity of magnesium found in this study was lower than that reported by Marques et al (2002) and Benites et al (2003) for Serra do Cipó.…”

“…The level of Phosphorus found in the restored areas was higher then the level reported by Marques (2002) and Negreiros et al (2009), while the values found in non-restored areas were similar to those reported by Negreiros et al (2008). The higher amount of Phosphorus in the soil must also be related to the elevated litter formation in the areas where C. cajan was planted.…”

Fluctuating asymmetry and herbivory in two ontogenetical stages ofChamaecrista semaphorain restored and natural environments

“…Plant species adapted to nutrient-poor environments have developed efficient systems to minimize nutrient losses such as high rate of resorption of nutrients (Nardoto et al 2006;Kozovits et al 2007) and scleromorphic leaves that in turn, reduce the probability of abscission and facilitate high concentration of chemical defenses (Fernandes and Price 1988;Price et al 1998). The endemic plants of the ruprestrian fields, such as C. semaphora, are adapted to the natural nutritional deficiencies of soil (Ribeiro and Fernandes 2000;Marques et al 2002;Negreiros et al 2008) and therefore these environmental conditions do not represent a stress factor to generate differences in developmental instability. Even when under the stress imposed by harsher conditions found in restored sites, the stress may have been not enough to influence the stability of the development of the studied species.…”

“…One of the harsher environments in the tropics is the quartzitic outcrop fields that occur at higher altitudes in the Espinhac¸o mountain range in southeastern Brazil (Ribeiro and Fernandes 2000;Marques et al 2002). In this vegetation formation, known as rupestrian fields we find the majority of the endangered species of the Brazilian Cerrado (savanna vegetation) (see Menezes and Giulietti 2000).…”

Sexual ratio and floral biology of the dioecious Neea theifera Oerst. (Nyctaginaceae) in a cerrado rupestre of central Brazil

“…In this sense the biology and population structures of some dioecious species may be strongly infl uenced by environmental factors, such as climate, soil and altitude (Freeman et al 1997). Th ese factors can infl uence the spatial distribution of sexual morphs as much as growing pattern, sex ratio and even pollination ecology of dioecious populations (Freeman et al 1997;Marques et al 2002;Ortiz et al 2002).…”