Abstract
A cladistic analysis of living Nyssa (Cornaceae) using 18 morphological characters suggests that: 1) the eastern Asian N. shweliensis and N. sinensis are closely related to the eastern North American N. sylvatica; 2) the newly described species from Costa Rica (N. talamancana) is closely related to the southeastern and eastern Asian N. javanica and N. shangszeensis, demonstrating another intercontinental disjunct distribution; and 3) no intercontinental species pair relationship has been revealed. The phylogenetic position of the eastern North American N. aquatica remains unresolved. Fossil evidence and geological data suggest that the intercontinental disjuncts in Nyssa are ancient. The migration of Nyssa between Eurasia and North America was probably via the North Atlantic land bridges. Its journey into Asia was probably through two pathways: 1) across Europe and western Siberia after the disappearance of the Turgai Strait at the end of the Eocene; and 2) via the shores of the Tethys Seaway. Nyssa became widely distributed in the Northern Hemisphere in the Tertiary, but suffered from wide extinctions probably during climatical changes in the late Tertiary and Quaternary. Species of Nyssa have survived in refugia of eastern and southeastern Asia and North and Central America. A new nomenclatural combination is made: Nyssa sylvatica var. ursina.
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