Scientists at the University of Southampton have developed a new way of analysing fossils allowing them to see how creatures from millions of years ago were shaped by their environment on a day-to-day basis for the first time.
The research published today in Proceedings of the National Academy of Sciences could revolutionise our understanding of how character traits driven by environmental changes shaped evolutionary history and life on earth.
It could help scientists to understand how much of a species’ evolutionary journey is down to ‘nature vs nurture’.
Researchers from the University of Southampton studied the fossilised remains of prehistoric plankton using high-resolution 3D scanning, like a medical CT scan, to examine tiny fossil shells about the size of a grain of sand.
These plankton, called foraminifera or ‘forams’ for short, are tiny floating seashells that still live in the ocean today. Their shells are made of calcium carbonate and grow every few days by adding a new chamber to their shell in a spiralling pattern.
These chambers act a little like the rings of a tree trunk, providing a permanent record of the growth and lived environment of forams over time.
The shells’ chemical composition also tells us about the conditions the organism lived in, including the chemistry, depth and temperature of the water.
“The fossil record provides the most powerful evidence of biodiversity change on Earth, but it traditionally does so at a scale of thousands and millions of years,” says Dr Anieke Brombacher , lead author of the paper how carried out the research at the University of Southampton and now works at the National Oceanography Centre.
“These fossils however act a bit like chapter summaries of a species’ evolutionary story. This new way of analysing them lets us read the pages within each chapter – allowing us to see how individual organisms adapted to their changing environment, not over the course of generations but within an individual life span at day-to-day resolution.”
The key advance the researchers developed was to combine highly advanced CT scanning with chemical analysis by laser ablation techniques. This combination of methods meant the team was able to ‘zoom in’ and ‘read’ the individual pages of those chapters to reveal how the forams grew and estimate the environment they experienced while growing.
The growth rates of all three species were similar at low temperatures, but one species grew much faster in higher temperatures despite reaching the same average size.
“If you’re a foram, temperature appears to be a bigger determinant of your growth rate than even how old you are,” says Dr Brombacher.
“Temperatures change throughout the depth of the ocean water column so being able to optimise growth at different temperatures would have allowed each foram to live in a greater variety of habitats.”
James Mulqueeney a PhD researcher from the University of Southampton and co-author of the study said: “We also found that of the two species with similar environmental sensitivities, one was able to reach the same size but with a thinner shell, indicating a lower energetic cost and potential evolutionary advantage.”
Researchers say the same analysis techniques could be applied to other creatures which preserve their environmental and lifespan information including ammonoids, corals and bivalves like clams, oysters and mussels.
“This sort of data is routine in how we study adaptation in modern populations but has only now been gathered for fossils. By bringing together experts and facilities across the University of Southampton, we’ve been able to make progress on a foundational question in biology that wouldn’t have been possible within a single discipline,” says Prof Thomas Ezard , supervising author on the paper from the University of Southampton.
The research is part of a wider project which aims to scale up the analysis across a wider sample of two thousand plankton specimens to determine if a species’ adaptive flexibility is likely to lead it to diverge into separate, distinct species over time.
Detecting environmentally dependent developmental plasticity in fossilised individuals is published in Proceedings of the National Academy of Sciences and is available online.
The study was funded by the Natural Environment Research Council (NERC).