Opuntia of Life
digital graphic, 2020
for Biology of Algae, see further illustrations
When working on the textbook about cryptogams, Prof. Burkhard Büdel asked for a generalized, but largely complete phylogenetic overview containing any group of organisms. Usually, one would call this a tree of life, but the suggested shape of drop-like units – each stating a singular origin and unresolved diversification – led to an appearance resembling Opuntia, the prickly pear cactus.
There are multiple ways to arrange this set, even as a sequence of evolving diversity. One key message is the single origin of cellular life, as well as of Eukarya, but with a repeated origin of multicellular groups (against common misunderstandings like the one that fungi are plants or multicellular groups all form a single clade).
Another statement and core information of the entire book is the term algae. The authors defined them in a broad sense, including cyanobacteria. Due to the number of endosymbiotic connections as a major principle of macroevolution, the tree or our Opuntia of life is more of a network at this level. Algae are thus polyphyletic, and in case of the Archaeplastida form a paraphyletic stage leading to plants.