THE SIGNIFICANCE OF TROPICAL PLANT OCCURRENCE IN THE REPUBLIC FLORA

The late Early to early Middle Eocene Republic flora of northeastern Washington State has been significant in documenting the early evolution of modern temperate groups such as the Betulaceae, Acer and the Rosaceae. However, an intriguing aspect of the flora is the reported presence of several distinctly tropical families including Bignoniaceae, Icacinaceae, Melastomataceae, Musaceae, and Theaceae, as well as fossil cycads. While these occurrences have been discussed widely, most of the fossils upon which they are based have not been studied in detail or formally described. Some of these fossils closely resemble several different families. A fruit described as Iodes (Icacinaceae, Pigg and Wehr 2002) is very similar to a Prunus (Rosaceae) endocarp, and Prunus leaves are common at Republic, along with flowers. Other distinctive structures may bear reinterpretation, for example specimens identified as the fruit of Ensete (Musaceae), may be interpreted as Nelumbo (Nelumboaceae) receptacles with embedded fruits. In other cases, primarily tropical families such as Bignoniaceae and Melastomataceae are known to have some temperate relatives, and it is quite possible that single representatives of these families with large tropical distributions might just represent one or two species that have ranges into temperate zones. In contrast to coastal megathermal floras of equivalent age (e.g., Chuckanut), Republic lacks palms, which are might be expected to be common components of tropical floras. We suggest that careful evaluation is needed before conclusively using these fossils to discuss tropical influences