PATTERNS AND MAINTENANCE OF EXTRAORDINARY VARIATION IN THE CARIBBEAN ORCHID, TOLUMNIA (ONCIDIUM) VARIEGATA

Patterns of morphological variation within the Tolumnia variegata complex of Puerto Rico, Hispaniola, and Cuba are described. Univariate and multivariate analyses of population data obtained from fresh material collected in Puerto Rico and the Dominican Republic indicated that three a priori groups (Puerto Rican spring- and fall-flowering populations, and Hispaniolan spring-flowering) are slightly different but considerable univariate overlap occurs in all characteristics measured, especially between the two phenological types in Puerto Rico. Among the flowering types, sympatric populations are either not different or are similar morphologically than pairs of allopatric populations. Similar analyses of herbaruim specimens, including type material, revealed that T. leiboldii, a species often confused with T. variegata, is restricted to Cuba, and is distinguished by having obovate instead of pandurate petals. Furthermore, spring- and fall-flowering T. variegata are more similar to each other within islands than among islands. Phenological and geographical groups are slightly different but the similarities among them are outstanding. Thus the Cuban, Hispaniolan, Puerto Rican, and Virgin Island populations of both phenological types represent a single species, T. variegata. Although some characteristics are plastic, especially vegetative features, the origin and maintenance of extraordinary levels of variation in T. variegata may involve hybridization, founder effects, and frequency dependent selection.