What are land plants and animals

18.04.2011 15:00

Ancestors of the land plants determined

Anette Hartkopf Press and communication
University of Cologne

Plant scientists identify freshwater green algae as the stem form of all land plants

Today's land plants all descend from the ancestors of the freshwater green algae of the Zygnematales group (ornamental algae). This is the result of a study by scientists from the Botanical Institute of the University of Cologne, the Fritz Lipmann Institute in Jena and the Université de Montrèal in Montréal, Canada. The result of the study refutes previous assumptions about the origin of land plants. So far, the representatives of the Charales (candelabrum algae) had been regarded as the closest related sister group of the land plants, because they are the morphologically most complex algae representatives of the freshwater algae and also have structural similarities to the land plants. The result of the investigations is an important step in understanding the evolution of land plants. The study was published in the journal BMC Evolutionary Biology. The head of the project is the Cologne botanist Dr. Burkhard Becker.

The aim of the study was to elucidate the relationships within the algae groups that led to the land plants. This was intended to identify the so-called sister group of land plants - the group of algae whose representatives today are most closely related to land plants. To do this, the biologists examined the DNA of forty species of green algae and land plants. The scientists determined the sequence of 129 proteins. By comparing these proteins from land plants and green algae, they were able to draw conclusions about the phylogeny, the tribal history, of the algae examined. "And then the surprising result came out that not the candelabrum algae (Charales) but the ornamental algae (Zygnematales) are the sister group to the land plants", says Burkhard Becker.

The new finding is important for evolutionary biology: "If you want to understand the biology of today's plants, you can only understand them in their evolutionary context," explains the botanist. “The evolutionary history is important for the properties that land plants have today.” Because if you want to understand this evolutionary history correctly, you have to know which algae groups are most closely related, because these algae groups already have many properties that the further developments decisively influenced in the country.

The study is also interesting because it corrects the widespread misunderstanding that evolution leads to increasingly complex organisms. In the case of the Zygnematales algae, you can see that this does not necessarily have to be the case. “Today's ornamental algae are built much more simply than candelabrum algae,” says Burkhard Becker. "In evolutionary science, it is seen more and more frequently that there is a 'reductive evolution' in which the complexity has been simplified again in evolution." Because of their beautiful shapes, ornamental algae have long been popular objects, even among amateurs of microscopy.

The researchers want to stay tuned to the topic in the future too, because the exciting question is what made these groups of algae so special that land plants could develop from them. Since the land plants originated monophyletically, that is, only once, the properties of the ornamental algae are of particular importance, says Becker: "Can one explain why this group of algae in particular was so well suited to producing such complex land plants and others not?"

If you have any questions: PD Dr. Burkhard Becker, 0221 470-7022,
[email protected]

Responsible: Dr. Patrick Honecker

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research results