f The Floristic Migration At The End Of Palaeozoic Times

In Middle Pennsylvanian times there were at least two biomes in tropical Euramerica: (1) wetlands known as coal swamps and (2) seasonally dry environments dominated by conifers, peltasperms and other gymnosperms (DiMichele & Aronson, 1992; Dimitrova et al., 2011). During late Middle Pennsylvanian and Late Pennsylvanian times there was a progressive change in the swamp vegetation, due to a combination of tectonically-driven landscape modification and climate change (Cleal et al., 2010, 2011). The partial removal of the arborescent lycopsids that represented the dominant ecomorphs of the swamp vegetation, removed patterns of incumbent advantage and permitted a lottery-like period of ecological and evolutionary escalation (DiMichele & Phillips, 1996). The result was that the coal swamps initially became dominated by fast-growing, weedy tree ferns. Eventually, in late Late Pennsylvanian and Permian times the swamps became fully drained and the conifer-peltasperm dryland vegetation came to dominate the lowland areas (Kerp, 1996).