Not just pond scum

Be honest. What do you think of when you hear the word “algae.” I'll bet you think “pond scum.” I know I do, and I know that that's unfair. There's a lot more to algae than pond scum. And a paper in the most recent BioScience by several of my colleagues illustrates why.

Zoe Cardon, Dennis Gray, and Louise Lewis have been studying desert algae. Yes, you read that right desert algae. If you've ever been in a desert, you probably noticed that the ground is covered with a fragile crust that's easily damaged. That crust includes a wide variety of organisms, cyanobacteria, lichens, bryophytes, diatoms, and green algae. As the figure to the left shows, a lot of different kinds of algae are found in these crusts. The plants that most of us know (e.g., mosses, ferns, and flowering plants) are all derived from one lineage that invaded the land (the embryophyte lineage in the figure), but algae hae invaded the land at least twenty additional times. These multiple invasions of the land provide a wealth of interesting opportunities for investigating ecological and evolutionary questions.

[M]ultiple desert green algal lineages provide independent evolutionary units for the study of mechanisms that met the environmental challenges confronting the ancestor of embryophytes when it first made the leap from water to land. Such potential tolerance or avoidance mechanisms can be tested in an explicitly phylogenetic context, separating lineage-specific from habitat-specific traits. In this overview, we expand on these two major emerging themes.

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[C]rusts are a natural, ongoing laboratory featuring unrelated aquatic taxa that diversified to the desert habit. Ultimately, these evolutionary "experiments" could provide very interesting information about protection against the effects of extreme dehydration, a threat to all known forms of life, and photoprotection under environmental stress, a threat to major primary producers.

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Cardon, Z.G., Gray, D.W., Lewis, L.A. (2008). The Green Algal Underground: Evolutionary Secrets of Desert Cells. BioScience, 58(2), 114. DOI: 10.1641/B580206