The tree of life is inherently fractal. Look
closely at one lineage of a phylogeny and it dissolves into many
separate lineages, and so on down to a very fine scale. There is
now a great body of phylogenetic research that has provided numerous
tools applicable at particular, usually fairly constrained, scales.
These tools have left many phylogenetic questions unanswered. We
think these questions will remain unanswered until it is possible
to do analyses across multiple scales.
We believe that the green plant lineage represents the most suitable
system for such research. It is one of the oldest and most diverse
branches of the tree of life, and it contains good examples of the
known phylogenetic problems. Investigations on it may draw on a
tradition of interdisciplinary collaborative research, facilitated
by the Green Plant Phylogeny Research Coordination Group (GPPRCG
or "Deep Green").
Many interesting questions remain to be tested in the green plants,
once a better resolved phylogeny is available, such as: How many
times was land colonized from the water by "green algae?"
Where did the key adaptive features for life on land come from?
How many times has multicellularity arisen in the green plants?
Did multicellularity ever reverse? How many times did alternation
of generations and diploid-dominant life-cycles arise? How has tempo
and mode of macroevolution changed during diversification?
Our overall objective is to resolve the primary pattern of evolutionary
diversification among green plants and establish a model for doing
so that will be applicable to other groups of organisms with long
evolutionary histories. A solid backbone based on genomic and ultrastructural
data for relatively few taxa will enable the integration of previous
and ongoing studies of many more taxa into a comprehensive picture
of green plant phylogeny.
We gratefully acknowledge funding (details
here) by the National Science Foundation under the Assembling
the Tree of Life Program.