Fossil temporal dynamics of phenotypic selection & life history evolution

Collections of fossils are time capsules. They are archives with key information that can be used to reconstruct what life was like in the past. Darwin's theory of natural selection is one of the pillars of evolutionary theory. It has shaped the diversity of organisms we see both living today and preserved in the fossil record. However, even though fossils offer a direct window into selection in the deep past, many aspects of selection have only been studied in contemporary populations. The main obstacle to studying the "goodness of fit" of long extinct organisms to the environments in which they lived is the difficulty of measuring fitness. What traits should organisms have in order to produce the most offspring? Are these traits influenced by palaeoenvironmental changes, palaeoclimatic conditions and/or other organisms? How do fitness, traits and environment change over geological time scales? Using abundant fossil populations of a unique model system, a species-rich genus of a colonial marine invertebrate, cheilostome bryozoans, this project will overcome the barrier of studying selection in the deep past and answer previously intractable evolutionary questions. With cheilostome bryozoans, I will estimate fecundity (a fitness component) from fossilized skeletal traits. Aided by a new automated machine-learning algorithm I will ensure big datasets for robust statistical analyses. In summary, the overarching goal of SELECT is to dig deep into constraints and drivers of phenotypic evolution.

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.