THE ADAPTIVE POWER OF DEVELOPMENTAL PLASTICITY

Environmental cues affect phenotypic traits at the life stage when they occur, but can also canalise later development in particular directions. The fossil record documents the journey of life over vast tracts of time, yet is often analysed via static snapshots. Many organisms with life cycles as diverse as zooplankton, bivalves, trilobites and trees nevertheless contain records of their dynamic ontogenetic development that are extractable via modern imaging technology. Drawing data from experiments on planktonic foraminifera and developing feature extraction software for x-ray computed tomography, I'll use an integral projection model (IPM) to motivate studies of how developmental plasticity evolved in deep time. IPMs are increasingly common in population ecology for studying the evolution of a continuously structured trait (such as size) that regulates rates of survival and fertility. According to the IPM, the strongest influence on foraminiferal population growth rate is somatic growth rate, which is morphologically visible in diverse fossil systems. The IPM also predicts that greater plasticity during development increases population mean fitness. In other words, ecologically dominant species should be more labile in their growth rates. The fossil record can make a strong contribution, especially empirically, to contemporary arguments into the evolution of size-structured populations spanning micro- and macroevolution.