Taxonomy and phytogeography of the Cactaceae of eastern Brazil.
Eastern Brazil is a vast tropical area known to be rich in cactus diversity and endemism. Early
explorers documented little of this due to the difficulty cacti present for preservation and
description of living and museum specimens. Most taxa now known were discovered in the past
100 years, the majority being named and classified by horticulturists, whose activities greatly
distorted their number and geographical range. Extensive literature, field and herbarium studies
enabled better determination of generic and specific limits, correct nomenclature and details of
distribution and ecology. Keys have been writte~ to facilitate identification of the 30 genera, 134
species and 43 heterotypic subspecies here recognised.
In Eastern Brazil cactus biodiversity is concentrated in Bahia and Minas Gerais - each
having > 90 taxa and 30 or more state endemics. The most likely explanation for this is greater
complexity and discontinuity of habitats, leading to isolation of taxa and increased speciation.
Cactus phytogeography lends support to recent hypotheses on historical plant migration routes in
South America, while analysis of distribution patterns indicates> 94% of taxa as ± restricted to
one of 3 major vegetation categories: (1) Mata atlantica, (2) Caatingas & Northern campos
rupestres and (3) Cer~ados& South-eastern campos rupestres. Significantly, the campos rupestres
are rich in endemic cacti, but divisable into two areas on the basis of cactus diversity. Of taxa
included in category (2), > 70% belong to one of three major geographical-ecological areas, ranged
west to east.
Conservation status has been determined usmg information gathered for the above
inventory and applying IUCN 1994 'Red List Categories' combined with Farjon & Page criteria
(,phylogenetic distinction', 'ecological importance', 'genetic diversity'). As guidance to
conservationists, prioritised shortlists of threatened taxa and Area Hotspots are provided. The
South-eastern campos rupestres are of the greatest concern in terms of threatened taxa.