Population studies in Goodyera (Orchidaceae) with emphasis on the hybrid origin of G. Tesselata

Morphological, cytological, and paper Chromatographic studies of populations from northern Michigan and examination of herbarium specimens from throughout North America were used to clarify the relationships ofGoodyera oblongifolia, G. repens var.ophioides, andG. tesselata. A canonical analysis of morphological data from mixed populations of these three species depictsG. tesselata as intermediate betweenG. oblongifolia andG. repens var.ophioides. The latter two species are diploid (2n = 30) andG. tesselata is tetraploid (2n = 60). Triploids (2n = ca. 45) were found in two mixed-species populations in northern Michigan.Goodyera tesselata produces three phenolic compounds present inG. oblongifolia and five different compounds present inG. repens var.ophioides. The range ofG. tesselata is confined to glaciated territory (except for two stations) in northeastern North America where the postglacially produced ranges ofG. oblongifolia andG. repens var.ophioides overlap. However,G. tesselata is quite abundant in areas outside the region of sympatry of the other two species. Based on this evidence, it is postulated thatG. tesselata is an allotetraploid species which resulted from hybridization betweenG. oblongifolia andG. repens var.ophioides during early post-Pleistocene. The slightly earlier blooming season ofG. tesselata may have been selected for to provide a measure of reproductive isolation between the tetraploid and its parents and to adapt the new species to the rather short growing season of northeastern North America.