Modeling evolutionary tempo and mode using morphological formal spaces and Markov-chain principles.

GABRIELA FONTANARROSA; ABDALA, VIRGINIA; DOS SANTOS, DANIEL ANDRÉS

Congreso; I Congreso Latinoamericano de Evolución (CLEVOL I); 2021

Asociaciones Argentina, Colombiana y Chilena de Evolución

Tempo and mode (T&M) of evolution summarize ancient and controversial subjects of Evolutionary Biology such as gradualism, punctuationism, convergence, contingence, trends, and entrenchment. Quantifying morphological changes through an evolutionary trajectory (ET) is useful to detect T&M patterns. We develop a novel and integrative methodological approach for T&M modeling. This proposal addresses simultaneously phenetic and phylogenetic information and ends up with a diagram accounting for the recurrence of phylogenetic paths across morphospace. Among some properties of this methodological proposal we can mention: 1) it is deeply rooted in Markov-Chain principles translated to evolutionary concepts, 2) includes the historical reconstruction of phenotypes across the phylogeny, 3) frames the entire phylogenetic tree within an evolutionary pseudo-time window ranging from the root to the terminals, and 4) provides an explicit metric of morphospace occupation. We modeled the ET of the phalangeal formulas (PF) in Lepidosauria as our study case. Our dataset included PFs compiled from 649 taxa (35 families of Lepidosauria including fossils) from which there exists a unique repertoire of 53 formulations. Among some of the results that this model offers, we found that: (i) PF evolution exhibits a clear trend toward reduction in the phalangeal count, and that (ii) evolutionary change tends to occur significantly between morphologically similar PFs. Notwithstanding, although minor but not trivial, transitions between distant formulas -jumps- occur.