Reproductive features of eight Cordia species (Boraginaceae) from the seasonally dry Pacific slope of Costa Rica are described. Components of the floral, pollinatory, breeding, and seed-dispersal systems of each species are interactive. Two sets of syndromes are recognized: one consisting of floral, pollinatory, and breeding-system traits; the other composed of growth form, habitat preferences, and seed-dispersal traits. Within the genus, in the Neotropics, there has been a radiation from an ancestor presumably characterized by a basic chromosome number of 8, heterostyly, and fleshy fruitedness. Within the separate lines that have diverged in respect of the second syndrome, episodes of polyploidization have occurred as well as chromosomal loss (aneuploidy). Homostyly and dioecism have appeared several times in Cordia, in different lines. Comparisons with the reproductive characteristics shown by Cordia species in two other neotropical communities reveal no contradictions to the generalizations drawn from the Pacific slope results. As PART OF AN EFFORT to understand the evolutionary changes and selective pressures that have brought about the kinds of reproductive adaptations which are to be seen in tropical forests, we have subjected the genus Cordia to an intensive investigation. The eight species of Cordia in the seasonally dry Pacific lowlands of Guanacaste Province, Costa Rica, were chosen for investigation (table 1). Cordia contains a number of common species that present a wide array of breeding systems, ranging from homostyly to heterostyly and dioccy, including flower morphs adapted for varied pollinatory assemblages, and utilizing both wind and animal seed dispersal. Our objective is to quantify, as far as possible, the critical aspects of phenology, floral and pollination biology, breeding system, and seed-dispersal strategy of different Cordia species, to attempt to discern correlations between these features, to interpret their ecological importance, and finally to point out evolutionary shifts which appear to have taken place as well as the selective pressures which may have produced them. DISTRIBUTION Gentry and Janos (1974) have summarized the Central American distribution of Cordia, and additional information is to be found in the work of Johnston (1949a,b, 1950). All eight Guanacaste Cordia species are widespread through most of Central America, presumably at drier sites (with the exception of C. alliodora which occurs up to 1000 meters and is found on the wet Atlantic slope as well). The distribution of Cordia alliodora and C. gerascmnthas extends northward into Mexico, while Cordia inermis and C. pringlei extend southward to northern South America. Most of the species also occur on several islands in the Caribbean.