| Sphagnum peatmosses currently play a global environmental role in maintaining atmospheric chemistry and climate homeostasis and likely have done so for hundreds of millions of years in Earth's past. Modern Sphagnum-dominated peatlands store a large proportion of global soil carbon as peat, such long-term sequestration fostering global climate homeostasis. Sphagnum peat mosses also harbor microbial methanotrophs and nitrogen fixers that likewise play globally important roles in Earth's biogeochemical cycles. Sphagnum has also been utilized in many ways by ancient and modern cultures. Although fossil fragments of Sphagnum-like peatmosses are known from the Permian (Neuberg, 1956, 1960), recent molecular clock analyses suggest that peat mosses may be considerably older, and certain Ordovician microfossils were interpreted by Kroken et al. (1996) as the resistant remains of sporophytic capsule epidermis of Sphagnum-like early mosses. This thesis aimed to increase understanding of the ecophysiology, paleobiology and evolutionary traits of Sphagnum, focusing on environmental impacts occurring from Ordovician through modern times. The effects of combined temperature and UV treatments on Sphagnum compactum structure were determined in laboratory cultures, revealing dramatic impacts of elevated temperature, as well as temperature-UV interactions, Laboratory analyses of the environmental influences most important in controlling development and maintenance of normal dorsiventral or axial gametophytic body orientation in a suite of modern seedless plants, including S. compactum, revealed the strong influence of illumination direction. Finally, well-understood shallow marine mid-Ordovician carbonates (Sinnipee Group), located in Dane Co., WI, and dated at 455-460 Mya, were investigated for evidence of peatmoss fossils. The discovery and description of fragmentary Ordovician Sphagnum-like leaf and stem remains from this deposit indicates that peatlands were likely present on Earth at least 150 million years earlier than previously thought. Given the global biogeochemical importance of modern Sphagnum, the discoveries documented in this thesis improve knowledge of Ordovician terrestrial biota and illuminate ancient to modern plant-environment interactions. |
