LEWIS, LOUISE A. University of Connecticut, Department of Ecology and Evolutionary Biology, 75 North Eaglevile Rd., Storrs, Connecticut, 06269 USA. - Numerous transitions to land in green plants: the 'other' land plants.
In addition to the more conspicuous embryophyte group, numerous other
green plant lineages have made successful transitions to land.
Phylogenetic analyses using molecular data indicate that these
lineages are primarily derived from freshwater ancestors, and include
free-living and lichen photobiont algae in the class Trebouxiophyceae,
and several distinct lineages of free-living algae in the class
Chlorophyceae. In all cases, these independently-derived land plants
must possess adaptations for environments with reduced water
availability, oxidative stress, and different light regimes than
experienced by their aquatic ancestors. In the most extreme cases,
these algae are living in very arid habitats. Given the monophyly of
green plants and the evolution of independent terrestrial lineages
from aquatic ancestors, these lineages represent natural experiments
in the transition of green photosynthetic organisms to terrestrial
living, and offer a rich source of taxa that can be compared
experimentally with the embryophytes.
Key words: Chlorophyceae, photophysiology, phylogeny, terrestriality, Trebouxiophyceae