National Science Foundation
Apparently,
the lowly fern deserves more respect.
New research
scheduled to appear as the journal Nature’s cover story on
February 1 concludes that ferns and horsetails are not -- as currently
believed -- lower, transitional evolutionary grades between mosses
and flowering plants. In fact, ferns and horsetails, together,
are the closest living relatives to seed plants.
"Today's
systematists are using genomic tools to re-write the textbooks
on animal and plant evolution," says James Rodman, program
director in NSF's division of environmental biology, which funded
the research. "This research is the latest major rearrangement
of the plant tree of life. It will encourage others to explore
ferns as model organisms for basic ecological and physiological
studies."
The research
calls for rethinking the "family tree" of green plants,
according to scientists. Also, it uncovers a research shortcoming:
All main plant model organisms used for research (such as Arabidopsis,
which became the first plant to have all its genes sequenced)
are recently evolved flowering plants.
This limitation
could compromise scientific research. Models in the newly identified
fern and horsetail lineage are needed to round out the study of
plant development and evolution. This could help scientists fight
invasive species, engineer genetic traits, develop better crops
and prospect the botanical world for medicines.
The new research
uses morphological and DNA sequence data to show that horsetails
and ferns make up one genetically related group, which evolved
in parallel to the other major genetically related group made
up of seed plants and including flowering plants.
"Our
discovery that 99 percent of vascular plants fall into two major
lineages with separate evolutionary histories dating back 400
million years. It will likely have a significant impact on several
disciplines, including ecology, evolutionary biology and plant
developmental genetics," said Kathleen Pryer, lead author
of the paper and assistant curator in botany at The Field Museum
in Chicago. "Viewing these two genetically related groups
as contemporaneous and ancient lineages will likely also have
profound consequences on our understanding of how terrestrial
ecosystems and landscapes evolved."
The work of
Pryer and her colleagues builds on the Deep Green project, a collaboration
of researchers dedicated to uncovering the evolution of and interrelation
of all green plants. In 1999, Deep Green reported at an international
botanical conference that DNA analysis indicates that all green
plants -- from the tiniest single-celled algae to the grandest
redwoods -- descended from a common single-celled ancestor a billion
years ago. Green plants, which include some 500,000 species, are
among the best-documented groups in the tree of life.
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