BIOSYSTEMATIC STUDIES IN SINNINGIA AND RECHSTEINERIA (GESNERIACEAE)

Tests of crossability and F1 hybrid fertility for 16 species of Sinningia and Rechsteineria show that these two genera constitute a single comparium made up of well-defined cenospecies. Floral structure suggests that divergence has resulted from adaptation to different principal pollinators. Recommendations are made for redefining sectional limits and combining Sinningia and Rechsteineria in one genus. EXPERIMENTAL hybridization is often of great help in delimiting related taxa at the generic level or lower. Although tropical floras, because of their diversity, would especially benefit from this type of investigation, they have received much less attention than floras of temperate regions. Sinningia Nees and Rechsteineria Regel, two closely allied neotropical genera known for the difficulty of their taxonomy as well as the ease with which intergeneric hybrids can be made between them (Arnold, 1960), warrant such an investigation. They are separated taxonomically by differences in floral structure that suggest adaptation to different pollinators. On the basis of their obliquely inserted, funnelform or pouched corolla tubes of purple, white, or rose-red, Sinningia species are probably beepollinated. In contrast, most Rechsteineria species have typical hummingbird flowers. The scarletto-yellow corolla tubes have a nearly erect insertion and are approximately cylindrical in shape. Sinningia is a relatively small but highly diverse genus of some 20 species native to Brazil, particularly to the southeast. Rechsteineria is a larger group containing about 80 species. Most of these are also located in southeast Brazil, but they range from northern Argentina to southern Mexico and as far west as the Andes in Peru. The species of both genera are tuberous perennials, and all that have been studied are self-compatible and have a chromosome count of 2n = 26 (Clayberg, 1967). The last to treat Sinningia and Rechsteineria was Fritsch (1893-94, as Corytholoma; 1913), who based his classification of the latter genus on that of Hanstein (1864). The sections recognized and characterized by these authors are given in Table 1, with the number of known species in parentheses after each section and subsection. Section Thamnoligeria was added by 1 Received for publication 18 January 1968. Fritsch in 1908. The species listed under each section are those used or discussed here. MATERIALS AND METHODS-Plants or seeds of Sinningia and Rechsteineria species were obtained from botanical gardens, private collections, and recent plant explorations. These sources have been given elsewhere (Clayberg, 1967) except for S. barbata, which was provided by the L. H. Bailey Hortorium, Cornell University, Ithaca, N.Y. While the species used were chiefly those available, studies of the literature and of the herbaria of the Smithsonian Institution, the New York Botanical Garden, and Cornell University indicate that these species are typical members of the sections to which they belong. As wild types of S. speciosa, the florists' gloxinia, were not available, several commercial varieties were used. No differences in results were observed among the cultivars tested, which included 'Fire King' and 'Queen Victoria.' Because most of the species are dormant for varying periods of the year, it was sometimes difficult to bring them into flower at the same time. In these instances crosses were made with pollen which had been stored in a freezer. The capability of such pollen to function in crosses of unknown compatibility was checked, when suitable testers were available, by using these pollen lots in known compatible cross combinations. All crosses were made with fresh pollen when it was available, and those unsuccessful with stored pollen were subsequently repeated with fresh pollen. Fresh pollen for freezing was collected at regular intervals, dried for about 1 hr over anhydrous silica gel at room temperature, and then stored in a desiccator at -17 C. Under these conditions pollen survived satisfactorily for 6 months or more. Hybrids and parental species were evaluated for fertility on the basis of pollen stainability in acetocarmine. All of the species except one