CLARKE, H.DAVID*, DAVID S. SEIGLER, AND STEPHEN R. DOWNIE. Department of Botany, Smithsonian Institution, Washington, DC 20560 and Department of Plant Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801. - Systematics and biogeography of Acacia subgenus Acacia in the West Indies.
New World members of Acacia subgenus Acacia total
approximately 60 species and are divisible into six groups of species
that include the ant acacias and the A. macracantha, A
farnesiana, A. rigidula, A. constricta, and A .
acuifera species group. While the center of diversity of the
subgenus is in Mexico, a cpDNA restriction site study found members of
the West Indian A. acuifera species group to be ancestral
within the subgenus. Moreover, most members of the A. acuifera
species group are narrowly endemic on serpentine or karstic soils in
Cuba and the Dominican Republic. These areas, and Caribbean coastal
dry forests in general, have been cited as areas that may have served
as refugia for an early Tertiary boreotropical flora. The center of
diversity of the A. acuifera species group corresponds to the
oldest landform in the Caribbean viz., eastern Cuba and western
Hispaniola. Principal components analysis of morphological characters
of members of the A. acuifera species groups revealed all taxa
to be phenetically distinct. This morphological differentiation of
the species also attests to their constituting an ancient radiation in
these serpentine areas. Application of a modified island biogeography
model to this radiation combined with what is known of the geological
history of the Caribbean implicates both vicariance and dispersal in
the evolution of these species.
Key words: Acacia, biogeography, cpDNA, Fabaceae, restriction site mapping, serpentine endemism