Visualizing Macroevolution: From Adaptive Landscapes to Compositions of Multiple Spaces

The adaptive landscape is an important diagrammatic concept that was conceived in population genetics. During the Modern Synthesis, in the first half of the twentieth century, the landscape imagery was used to represent evolution on a large scale, aiding in the construction of a common language for a new evolution- ary biology. Not only historic adaptive landscapes by Dobzhansky, Simpson, and others are a record of how macroevolution was thought of in those decades; they stimulate reflection on “combination spaces” that underlie them. In fact, any land- scape diagram is the three-dimensional transposition of a multidimensional space of combinations of genes, morphological traits, or other kinds of variables. This is an important and enduring general point of awareness: The diagram displays some aspects of the considered space while hiding others, exposing the author and the user to incomplete understanding and to conflating different spaces. Today, macroevolution is studied as a multifarious exploration of spaces of possibilities of all different sorts, interconnected in complex ways: genotype spaces, molecu- lar spaces, morphospaces, geographical spaces, ecological spaces, and genea- logical spaces. Actual macroevolutionary stories and outcomes are a subset of the universes of possible combinations—of genes, nucleotides, morphological traits, and environmental variables. Visualizations of macroevolution are a challenge of showing both distinction and correlation between spaces of possibilities.