Genetics, phylogenetics, and biogeography: Considering how shifting paradigms and continents influence fern diversity |
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Authors: | Christopher H Haufler |
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Institution: | 1. Department of Ecology and Evolutionary Biology, University of Kansas, 66049, Lawrence, KS, U.S.A.
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Abstract: | About 25 years ago, a revolution began in evolutionary studies of seed-free vascular plants. Whereas common wisdom and laboratory-based
observations had averred that minute spores and inbreeding of individual bisexual gametophytes diminished barriers to long
distance migration, genetic analyses of sporophyte populations demonstrated outcrossing breeding systems that required two
spores for each successful migration event. After those population-based discoveries, the processes controlling biogeographic
patterns of ferns appeared to resemble those of seed plants, and vicariance took on renewed significance. More recently, data
from DNA sequencing predicted that some of the most diverse extant fern families originatedafter the isolation of major land masses, and these new hypotheses also demanded fresh consideration of biogeographic assumptions.
The Polypodiaceae yield phylogenetic insights through integration of DNA sequence analysis and biogeography. New evidence
shows separate yet simultaneous radiations in the New and Old Worlds. By combining sequence data, vicariance, and a reassessment
of morphological features, new family and generic boundaries are obtained. Contributors to this symposium discovered similar
patterns in the systematics and biogeography of the seed-free vascular plants they studied. Although long distance migration
remains an important factor in explaining fern distributions, local and recent radiations that result in species complexes
are also significant in explaining fern biogeography. |
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