Pathways of karyological differentiation in palms (Arecaceae).
Karyological data are given for 56 palm taxa from all 6 palm subfamilies. In 11 genera and 17 species, chromosome numbers are reported for the first time. Most chromosome numbers in palms range between 2n=36 and 2n=26 in dysploid series. Species of the same genus usually exhibit identical chromosome numbers, which additionally may be constant in larger groups of closely related genera (Coryphoideae tribe Corypheae with nearly always 2n=36, Arecoideae subtribes Euterpeinae and Roystoneinae with 2n=36, Arecoideae subtribe Butiinae with mostly 2n=32). Polyploidy among palms is of minor significance, but the endemic Madagascan genus Voanioala (2n=606±3) is the most striking exception. Karyological characters are compared with morphological, ecological, taxonomic and chorological features, and give some new insights into older and more recent phases of palm evolution. (1) Strong deviations in vegetative or floral morphology are often accompanied by major karyological differences, and sometimes the direction of advancement can be traced through intermediate stages. (2) Apart from Coryphoideae subtribe Thrinacinae, the strongest concentration of apparently original karyological traits is found in the more basal members of each subfamily. (3) The most successful and actively radiating colonizers of the forest floors in evergreen tropical forests, which belong to completely different subfamilies (Old World Licuala, New World Chamaedorea and Geonoma), appear to be very advanced karyologically.