Natural selection is one of the pillars of evolution. It has shaped the diversity of organismal forms we see both today, among living organisms, and in the fossil record. However, although the fossil record offers a direct window into selection in the deep past, many aspects of selection have only been studied in extant populations. The main barrier remains to obtain estimates of fitness components and selection gradients from fossil populations to directly link evolutionary parameters and selective forces on macroevolutionary time scales. Which combination of phenotypic traits will produce the most offspring? Can we infer these using populations, long dead? Using a novel approach based on abundant fossil populations of a unique model system, a species-rich genus of encrusting cheilostome bryozoans, I will overcome the barrier of studying selection in the deep past. Using the model bryozoan genus, I will robustly estimate fecundity (a fitness component) from fossilized morphological traits and investigate the past selection gradients and the potential driving forces of phenotypic selection on a high resolution time series that spans the last 2.5 million years. Addressing key questions such as —Are selection gradients for the same traits for different, closely allied species similar or different during the same time periods, in the same habitats? How different are the strengths and mode of selection and what do these patterns say about evolutionary constraints and historical contingency? Do ecological interactions affect the evolution of phenotypic traits such that there are long-term, macroevolutionary consequences? What are the relationships between speciation/extinction rates and rates of phenotypic evolution?— this project will open research avenues that are to date impenetrable.
Project leader: Emanuela Di Martino
Institution: Naturhistorisk museum