| The objective of this study was to examine the biogeography and human use of a tropical rainforest species--the piassava palm (Attalea funifera). Inquiry focused on the physical and biological processes that affect the range of this species, and included the role of humans as agents of ecological change.;Piassava produces male, female, and bisexual inflorescences. Apomixis does not occur, while self-pollination through geitonogamy is possible on bisexual inflorescences. Piassava is mostly dioecious, and is pollinated by sap beetles (Mystrops sp.) and weevils (Phyllotrox tatianae). This palm changes sex during its lifetime, a condition related to the cost of fruit production and the level of insolation.;Piassava produces huge bunches 500 gm fruit. Seed predation by bruchid beetles (Pachymerus nucleorum Fabr.) is distance- and density-dependent. Human hunting of rodents has led to their rarity and, consequently, largely eliminated seed dispersal.;Piassava's fiber has a history of exploitation beginning in the 1500's with the fashioning of anchor ropes, extends through the colonial period with the manufacture of brooms and brushes, and continues to the present as the most common raw material for Brazilian brooms.;Piassava inhabits a north-south belt of restinga rainforests along the coast of Bahia, Brazil. Its range coincides with the zone of tropical rainforest climate (Koppen Af), and is restricted to Pliocene/Pleistocene podzolic soils.;Ownership of piassava-rich forests is mostly private. Management incudes benign neglect, planting, and burning. Planting piassava seeds using wild sources has met with notable success. Burning is carried out to increase the density of piassava. Seedlings survive because their stems, which are below the soil surface, resprout after the fire.;Piassava's distribution is responsive to increasing aridity and rainfall variability at its northern and southern ecotones. Its western margin coincides with a transition from podzols to latosols and tall rainforests. Piassava's restriction to podzolic soils may result from its inability to reach the energy-rich forest canopy of the tall rainforest, triggering a male-dominated population that is unable to reproduce. As Bahia's rainforests are eliminated, piassava may expand to occupy its full climatic range. |
