Browsing by Author "Schneider, Harald"

Now showing 1 - 4 of 4

Open Access
Deciding among green plants for whole genome studies.
(Trends in plant science, 2002-12) Pryer, Kathleen M; Schneider, Harald; Zimmer, Elizabeth A; Ann Banks, Jo
Recent comparative DNA-sequencing studies of chloroplast, mitochondrial and ribosomal genes have produced an evolutionary tree relating the diversity of green-plant lineages. By coupling this phylogenetic framework to the explosion of information on genome content, plant-genomic efforts can and should be extended beyond angiosperm crop and model systems. Including plant species representative of other crucial evolutionary nodes would produce the comparative information necessary to understand fully the organization, function and evolution of plant genomes. The simultaneous development of genomic tools for green algae, bryophytes, 'seed-free' vascular plants and gymnosperms should provide insights into the bases of the complex morphological, physiological, reproductive and biochemical innovations that have characterized the successful transition of green plants to land.
Open Access
Ferns diversified in the shadow of angiosperms.
(Nature, 2004-04) Schneider, Harald; Schuettpelz, Eric; Pryer, Kathleen M; Cranfill, Raymond; Magallón, Susana; Lupia, Richard
The rise of angiosperms during the Cretaceous period is often portrayed as coincident with a dramatic drop in the diversity and abundance of many seed-free vascular plant lineages, including ferns. This has led to the widespread belief that ferns, once a principal component of terrestrial ecosystems, succumbed to the ecological predominance of angiosperms and are mostly evolutionary holdovers from the late Palaeozoic/early Mesozoic era. The first appearance of many modern fern genera in the early Tertiary fossil record implies another evolutionary scenario; that is, that the majority of living ferns resulted from a more recent diversification. But a full understanding of trends in fern diversification and evolution using only palaeobotanical evidence is hindered by the poor taxonomic resolution of the fern fossil record in the Cretaceous. Here we report divergence time estimates for ferns and angiosperms based on molecular data, with constraints from a reassessment of the fossil record. We show that polypod ferns (> 80% of living fern species) diversified in the Cretaceous, after angiosperms, suggesting perhaps an ecological opportunistic response to the diversification of angiosperms, as angiosperms came to dominate terrestrial ecosystems.
Open Access
Phylogeny and evolution of ferns (monilophytes) with a focus on the early leptosporangiate divergences.
(American journal of botany, 2004-10) Pryer, Kathleen M; Schuettpelz, Eric; Wolf, Paul G; Schneider, Harald; Smith, Alan R; Cranfill, Raymond
The phylogenetic structure of ferns (= monilophytes) is explored here, with a special focus on the early divergences among leptosporangiate lineages. Despite considerable progress in our understanding of fern relationships, a rigorous and comprehensive analysis of the early leptosporangiate divergences was lacking. Therefore, a data set was designed here to include critical taxa that were not included in earlier studies. More than 5000 bp from the plastid (rbcL, atpB, rps4) and the nuclear (18S rDNA) genomes were sequenced for 62 taxa. Phylogenetic analyses of these data (1) confirm that Osmundaceae are sister to the rest of the leptosporangiates, (2) resolve a diverse set of ferns formerly thought to be a subsequent grade as possibly monophyletic (((Dipteridaceae, Matoniaceae), Gleicheniaceae), Hymenophyllaceae), and (3) place schizaeoid ferns as sister to a large clade of "core leptosporangiates" that includes heterosporous ferns, tree ferns, and polypods. Divergence time estimates for ferns are reported from penalized likelihood analyses of our molecular data, with constraints from a reassessment of the fossil record.
Open Access
The Evolution and Diversification of Epiphytic Ferns
(2007-05-03T18:53:24Z) Schuettpelz, Eric
Leptosporangiate ferns, with more than 9000 extant species, are truly exceptional among the non-flowering lineages of vascular plants. However, this rather remarkable diversity was not simply a consequence of being able to "hold on" as flowering plants rose to dominance. Instead, it appears to be the result of an ecological opportunistic response to the establishment of more complex, angiosperm-dominated ecosystems. The proliferation of flowering plants across the landscape undoubtedly resulted in the formation of a plethora of new niches into which leptosporangiate ferns could diversify. Many of these were evidently on shady forest floors, but many others were actually within the new angiosperm-dominated canopies. Today, almost one third of leptosporangiate species grow as epiphytes on angiosperm trees. My dissertation aims to demystify the evolution and diversification of epiphytic ferns in order to more fully understand the leptosporangiate success story. By assembling and analyzing the most inclusive molecular dataset for leptosporangiate ferns to date, I provide unprecedented insight into overall fern relationships and a solid and balanced phylogenetic framework within which the evolution of epiphytism can be examined. By employing this phylogeny and numerous constraints from the fern fossil record, I uncover the timing of epiphytic fern diversification and examine the origin of the modern tropical rain forest biome in which these ferns reside.