Interdisciplinary Initiatives Program Round 5 – 2010

Jan Skotheim, Biology    
Jonathan Payne, Geological & Environmental Sciences

Size and function are inseparable in biology. The ecology, physiology, and cell biology (e.g. cellular DNA) of species all scale with size. Consequently, identifying variables that constrain cell and genome size and the mechanisms by which they operate can shed light on critical aspects of evolutionary biology, including controls on the evolution of large, complex, and intelligent organisms. Despite their importance, environmental controls on the evolution of both cell and genome size remain poorly understood.

In our study, we are investigating environmental controls on cell and genome size in single-celled eukaryotes, which represent the earliest macroscopic life forms on Earth and the progenitors of all animal and plant diversity. As a case study, we are considering the marine protists Foraminifera, which are an ideal study group because they have been abundant in the oceans for the past 400 million years (My) and are represented by more than 30,000 fossil and 5,000 living species. The extensive fossil record and high modern diversity of foraminifera provide an unparalleled system for studying geological influences on the evolution of cell biology. Combined analysis of living and fossil material is critical because historical data allow us to assess evolutionary response to environments not represented on our planet today (e.g., 35% atmospheric oxygen; 2000 ppm CO2) while living specimens provide the opportunity to investigate cell biological traits not preserved in fossils.

Our initial findings indicate that the size and shape of both fossil and living foraminifera is sensitive to environmental conditions, especially oxygen availability. In fact, our study provides the first quantitative confirmation that atmospheric hyperoxia can explain widespread instances of gigantism during the Carboniferous and Permian periods (360-250 million years ago). This interdisciplinary collaboration would not be possible without the joint expertise linking cell biological and paleontological techniques. This study will shed light on how environmental change can impact fundamental cell biological properties.