The ecology of Paleozoic ferns

Ferns or fern-like plants have been important elements of terrestrial vegetation since the Late Devonian. Rhacophyton, a fern-like plant of the Late Devonian, appears to have been a colonizer of wet substrates, often forming large, nearly monotypic stands in peat-accumulating swamps. The earliest true ferns have been found in environments with high levels of disturbance, often tire, which suggest opportunistic, colonizing life histories, consistent with small, scrambling body plans. During the Early Carboniferous all major body plans and life histories of ferns appear, including scrambling ground cover, tree habit, and lianas. These ecological roles are distributed across several major lineages, including the Zygopteridales, Filicales, and Marattiales, plus some fern-like groups of uncertain affinity, and disappear and reappear independently within these groups. Until the Stephanian, the later part of the Late Carboniferous, ferns largely were confined to secondary ecological roles: colonists, understory vegetation, small vines. Beginning in the latter part of the Westphalian and expanding dramatically in the Stephanian, marattialean tree ferns became the dominant trees of tropical lowland, wetland forests. This dominance continued locally into the Permian in wetter parts of the landscape. The Paleozoic ferns suffered major extinctions at several times, beginning in the Late Carboniferous. By the Permian, new lineages were appearing, some of which would persist into and become dominant vegetational components during the Mesozoic. Among these lineages virtually all of the life histories and body plans that characterized Paleozoic ferns would reappear independently, plus some new kinds of organization and ecology, emphasizing the great evolutionary flexibility and responsiveness of fern-like construction and reproductive biology. (C) 2002 Elsevier Science B.V. All rights reserved.