ABSTRACT
Trillium species are widely distributed in North America and Asia. The genus Trillium is common in eastern and western North America and eastern Asia. The plants have ten large chromosomes which exhibit cold-induced banding patterns. This chapter compares the modes of speciation of American and Asian Trillium species, adding chromosomal data and ecological observations of the reproductive system. It discusses how the different mechanisms of speciation may have occurred in North America and Asia from both genetic and ecological standpoints. The three examples, two from eastern and one from western North America indicate that, within a given species of Trillium, there is a strong association between chromosomal variation and environmental heterogeneity. Trillium kamchaticum Pall, grows in the Acer, Ulmus, and Cryptomeria mixed forests of northern Japan. The most important difference between North American and Asian Trillium species is the development of polyploid species in Asia.
