Proterozoic and early Cambrian protists: evidence for accelerating evolutionary tempo
1Botanical Museum, Harvard University, Cambridge, MA 02138.
Summary
Early eukaryotic microfossil diversity was low, but algal diversification and the Cambrian explosion of animals significantly increased protistan diversity and evolutionary rates across kingdoms.
Area of Science:
- Paleontology
- Evolutionary Biology
- Geology
Background:
- Eukaryotic microfossils from the Paleoproterozoic and Mesoproterozoic eras (1700-1000 million years ago) show low diversity and slow evolutionary turnover.
- Molecular phylogenies indicate a significant radiation of "higher" eukaryotic phyla near the Mesoproterozoic-Neoproterozoic boundary.
Purpose of the Study:
- To investigate the evolutionary history and diversification rates of early eukaryotic life.
- To understand the impact of major ecological events, such as the Cambrian explosion, on microbial evolution.
Main Methods:
- Analysis of microfossil assemblages from late Paleoproterozoic and Mesoproterozoic rock formations.
- Correlation of microfossil diversity and turnover rates with geological time and major evolutionary events.
- Integration of molecular phylogenetic data to infer eukaryotic evolutionary radiations.
Main Results:
- Algal diversification (red, green, chromophytic) occurred near 1000 million years ago, coinciding with increased protistan microfossil diversity and turnover.
- The Cambrian radiation of marine invertebrates led to a doubling of protistan microfossil diversity and a tenfold increase in turnover rates.
- Evidence suggests that the diversification of animals profoundly influenced evolutionary rates in co-existing eukaryotic clades.
Conclusions:
- The Cambrian explosion was not limited to animals but significantly impacted protistan evolution, demonstrating inter-kingdom ecological influence.
- Eukaryotic evolution accelerated through distinct phases, marked by algal radiation and later by animal diversification.
- Ecological interactions played a crucial role in driving evolutionary innovation during major biotic events like the Cambrian explosion.
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