The flourishing diversity of models in theoretical morphology: from current practices to future macroevolutionary and bioenvironmental challenges

For decades, theoretical morphological studies of different groups of organisms have been successfully pursued in biological, paleontological, and computational contexts, often with distinct modeling approaches and research questions. A regular influx of new perspectives and varied expertise has contributed to the emergence of a veritable multidisciplinary outlook for theoretical morphology. The broadening of this discipline is reflected in a substantial increase in the number of models, leading to a bewildering diversity that has yet to be scrutinized. In this work, we tackle this issue in a synthetic fashion, with a quantitative meta-analysis that allows an objective comparison of theoretical morphological models treated as entities. By analogy with empirical morphospace analyses of actual organisms, we performed a multivariate ordination of a representative sample of models, producing a metaspace of models in which patterns of similarity and difference are visualized. A phenetic tree was used to characterize the relationships between models. Four major groups have been identified, and their disparity analyzed. We suggest this typology as a useful starting point to identify a core set of fundamental principles and protocols for better interpretation of the plethora of current models and for more efficient construction of models in the future. This in turn can help in diversifying the scope of macroevolutionary, developmental, and bioenvironmental questions in theoretical morphology.