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New York Botanical
Garden, New York, USA
EMu user since 2002
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Bertholletia excelsa
belongs to a pantropical family of trees (Lecythidaceae) that includes
approximately 200 species in the Neotropics, distributed from southern
Mexico into southern Brazil (Mori and Prance, 1990a; Prance and Mori, 1979).
The Brazil nut represents a single species in the well-defined genus
Bertholletia. Although there is considerable variation in fruit size and
shape and number of seeds per fruit, there is no justification for
recognizing more than one species of Bertholletia.
The closest relatives
of B. excelsa are among species of Lecythis commonly referred to in
the vernacular as the jarana group (Mori and Prance, 1990b). Other species
with edible seeds in the family are Lecythis pisonis and its relatives, L.
minor and L. ollaria. The latter two species, however, sometimes cause hair
and fingernail loss because of excess selenium accumulation in the seeds
(Dickson, 1969; Kerdel-Vegas, 1966). Nevertheless, the differences between
Bertholletia and Lecythis are so great that there is little
hope for introducing genetic material from one genus into the other via
hybridization. Consequently, germ plasm for improvement of Brazil nut
production will have to come from the variation found within B. excelsa,
not from closely related species in other genera.
Bertholletia excelsais an Amazonian plant that prefers nonflooded forest (terra firma) in the
Guianas, Colombia, Venezuela, Peru, Bolivia and Brazil.
Trees of Bertholletia excelsa occur in stands of 50 to 100 individuals that are
known as "manchales" in Peru (Sánchez, 1973) and "castanhais" in Brazil
(Dias, 1959). Density of Brazil nut trees per hectare varies considerably
throughout the Amazon. In a study of Brazil nut production in eastern
Brazil, Miller (1990) found from 9 to 26 reproductive trees per hectare,
while Becker and Mori (unpublished data) found only one tree over 10
centimeters dbh in a 100-hectare plot in central Amazonian Brazil.
There is some evidence
that Brazil nut trees are gap dependent (Mori and Prance, 1990b). Moreover
some authors have suggested that stands of the Brazil nut owe their origin
to pre-Colombian Indians (Miller, 1990; Mori and Prance, 1990b; Müller et
al., 1980). An understanding of the development of reproductive individuals
from seed is still needed before management of Brazil nuts in natural stands
is possible.
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