作 者 ：SA Ren, CHEN Chia-Jui, LI Pei-Chun
期 刊 ：植物分类学报 2000年 2期
Keywords:Thermopsis, Geographical distribution, Origin, Evolution,
Abstract:
The present article is the first comprehensive treatment of phytogeography of Thermopsis
(Fabaceae) in the world. Thermopsis is one of the few genera within Fabaceae with the distribution
pattern of the East Asia-North American disjunction. The distribution patterns of 5 recognized sec-
tions (including a new one) covering 21 species in Thermopsis are analyzed, and the results show
four centres of frequency of the genus: the Eastern Asiatic Region (9 spp. / 3 sects., including 4
endemic species), the Irano-Turanian Region (7 spp./3 sects., including 3 endemic species), the
Rocky Mountain Region (7 spp./2 sects., all endemic), and the Atlantic North American Region
(3 spp. / 1 sect., all endemic). In the light of the fact that most species and sections, a number of
phylogenetic series of the genus, and the most primitive sections and most advanced sections in
Thermopsis occur in the East Asia, the Eastern Asiatic Region might be the centre of diversity of the
genus. As the Irano-Turanian Region and the Rocky Mountain Region were just second to that of
Eastern Asiatic Region in number of sections and species, and many polyploids appeared in these
regions, they were considered as the secondary centres of distribution and speciation of the genus.
The speciation looks to be frequent and complex in these regions, and many new taxa have been de-
scribed from there while many new reduced or incorporated taxa have happened over there. Howev-
er, recent molecular data has shown that two reduced taxa of Thermopsis are distinct in these re-
gions. Based on the modern distribution patterns and evolutionary trends in morphological characters
of the genus, and available fossil record of the genus and the historical geology, we speculate that
Thermopsis had already existed on Eurasia and North America before the Late Miocene, and proba-
bly originated from an ancestral form of Sophora-like taxa with lupine alkaloids somewhere in the
Laurasia in the Early Tertiary or Late Cretaceous. After the separation of the two continents, species
on different continents developed distinctly under influences of different evolutionary factors. In
Asia, the late Tertiary orogeny, disappearing of the Tethys and aridity and freezing caused by the
Quaternary glaciation were the main forces to promote the speciation and evolutionary processes,
whereas in North America it was the Quaternary glaciation and the orogeny of partial area to promote
evolution of the genus. According to the evolutionary trends in Thermopsis and the distribution pat-
tern of the primitive taxa, Sino-Japanese Subregion of Eastern Asiatic Region may be considered as
the centre of primitive forms of Thermopsis.