It's a protist-eat-protist world: recalcitrance, predation, and evolution in the Tonian–Cryogenian ocean

2018 ◽  
Vol 2 (2) ◽  
pp. 173-180 ◽  
Author(s):  
Phoebe A. Cohen ◽  
Leigh Anne Riedman
Keyword(s):  
Molecular Clock ◽  
Fossil Record ◽  
Critical Role ◽  
Indirect Evidence ◽  
Tree Of Life ◽  
Current Understanding ◽  
Evolutionary Transitions ◽  
Ecological Interaction ◽  
Fossil Evidence ◽  
Multiple Metrics

Predation, and how organisms respond to it, is an important ecological interaction across the tree of life. Much of our understanding of predation focuses on modern metazoa. However, predation is equally important in single-celled eukaryotes (commonly referred to as protists). In the fossil record, we see evidence of protists preying on other protists beginning in the Tonian Period (1000–720 Ma). In addition, the first evidence of eukaryotic biomineralization and the appearance of multiple unmineralized but recalcitrant forms are also seen in the Tonian and Cryogenian (720–635 Ma), potentially indirect evidence of predation. This fossil evidence, coupled with molecular clock analyses, is coincident with multiple metrics that show an increase in the diversity of eukaryotic clades and fossil assemblages. Predation, thus, may have played a critical role in the diversification of eukaryotes and the evolution of protistan armor in the Neoproterozoic Era. Here, we review the current understanding of predation in the Tonian and Cryogenian oceans as viewed through the fossil record, and discuss how the rise of eukaryotic predation upon other eukaryotes (eukaryovory) may have played a role in major evolutionary transitions including the origins of biomineralization.

scholarly journals Diversification dynamics of total-, stem-, and crown-groups are compatible with molecular clock estimates of divergence times

2021 ◽  
Vol 7 (24) ◽  
pp. eabf2257
Author(s):  
Alan J. S. Beavan ◽  
Davide Pisani ◽  
Philip C. J. Donoghue
Keyword(s):  
Time Scales ◽  
Molecular Clock ◽  
Fossil Record ◽  
Divergence Times ◽  
Evolutionary Time ◽  
Crown Group ◽  
Total Group ◽  
Fossil Evidence ◽  
Evolutionary Radiations ◽  
Birth Death

Molecular evolutionary time scales are expected to predate the fossil evidence, but, particularly for major evolutionary radiations, they can imply extremely protracted stem lineages predating the origin of living clades, leading to claims of systematic overestimation of divergence times. We use macroevolutionary birth-death models to describe the range of total-group and crown-group ages expected under constant rates of speciation and extinction. We extend current predictions on origination times for crown- and total-groups, and extinction of stem-groups, demonstrating that there is broad variance in these predictions. Under constant rates of speciation and extinction, we show that the distribution of expected arthropod total-group ages is consistent with molecular clock estimates. The fossil record cannot be read literally, and our results preclude attempts to interpret the antiquity of clades based on the co-occurrence of stem- and crown-representatives.

The fossil record of Phasmida (Insecta: Neoptera)

2000 ◽  
Vol 31 (4) ◽  
pp. 473-480 ◽  
Author(s):  
Erich Tilgner
Keyword(s):  
Dominican Republic ◽  
Molecular Clock ◽  
Fossil Record ◽  
Sister Group ◽  
Baltic Amber ◽  
Molecular Clock Dating

AbstractA review of the Phasmida fossil record is provided. No fossils of Timema Scudder are known. Euphasmida fossils include: Agathemera reclusa Scudder, Electrobaculum gracilis Sharov, Eophasma oregonense Sellick, Eophasma minor Sellick, Eophasmina manchesteri Sellick, Pseudoperla gracilipes Pictet, Pseudoperla lineata Pictet and various unclassified species from Grube Messel, Baltic amber, and Dominican Republic amber. The oldest documented Euphasmida fossils are 44-49 million years old; molecular clock dating underestimates the origin of the sister group Timema by at least 24 million years.

scholarly journals Flying rocks and flying clocks: disparity in fossil and molecular dates for birds

2014 ◽  
Vol 281 (1788) ◽  
pp. 20140677 ◽  
Author(s):  
Daniel T. Ksepka ◽  
Jessica L. Ware ◽  
Kristin S. Lamm
Keyword(s):  
Analytical Methods ◽  
Fossil Record ◽  
Tree Of Life ◽  
Temporal Information ◽  
Molecular Dating ◽  
Critical Nodes ◽  
Molecular Divergence ◽  
Divergence Dates ◽  
Divergence Estimates ◽  
Age Estimates

Major disparities are recognized between molecular divergence dates and fossil ages for critical nodes in the Tree of Life, but broad patterns and underlying drivers remain elusive. We harvested 458 molecular age estimates for the stem and crown divergences of 67 avian clades to explore empirical patterns between these alternate sources of temporal information. These divergence estimates were, on average, over twice the age of the oldest fossil in these clades. Mitochondrial studies yielded older ages than nuclear studies for the vast majority of clades. Unexpectedly, disparity between molecular estimates and the fossil record was higher for divergences within major clades (crown divergences) than divergences between major clades (stem divergences). Comparisons of dates from studies classed by analytical methods revealed few significant differences. Because true divergence ages can never be known with certainty, our study does not answer the question of whether fossil gaps or molecular dating error account for a greater proportion of observed disparity. However, empirical patterns observed here suggest systemic overestimates for shallow nodes in existing molecular divergence dates for birds. We discuss underlying biases that may drive these patterns.

scholarly journals Giant Viruses and the Tree of Life

2021 ◽  
Vol 6 (2) ◽  
Author(s):  
Patrick Forterre
Keyword(s):  
Tree Of Life ◽  
Current Understanding ◽  
Giant Virus ◽  
Giant Viruses

When the first giant virus, the mimivirus, was discovered in 1992, it was misidentified as a bacterium because it was too large to have been a virus by the current understanding. Ever since, biologists have been debating how viruses should be categorized and described. Are they living? Are they something else? What is their place on the tree of life?

scholarly journals Major features of protistan evolution: controversies, problems and a few answers

2006 ◽  
Vol 29 (1) ◽  
pp. 55-80
Author(s):  
Jere H Lipps
Keyword(s):  
Fossil Record ◽  
Molecular Data ◽  
Trophic Levels ◽  
Early Earth ◽  
Huge Number ◽  
Geologic Time ◽  
Earth History ◽  
Important Development ◽  
Fossil Evidence

The major features of protist evolution are fraught with controversies, problems and few answers, especially in early Earth history. In general they are based on molecular data and fossil evidence that respectively provide a scaffold and details of eukaryotic phylogenetic and ecologic histories. 1. Their origin, inferred from molecular sequences, occurred very early (>;3Ga). They are a chimera of different symbiont-derived organelles, including possibly the nucleus. 2. The initial diversification of eukaryotes may have occurred early in geologic time. Six supergroups exist today, each with fossils known from the Proterozoic and Phanerozoic. 3. Sex, considered an important development, may have been inherited from bacteria. 4. Precambrian protists were largely pelagic cyst-bearing taxa, but benthic forms were probably quite diverse and abundant. 5. Protists gave rise to animals long before 600 Ma through the choanoflagellates, for which no fossil record exists. 6. Acritarchs and skeletonized protists radiated in the Cambrian (544-530 my). From then on, they radiated and became extinct at all the major events recorded in the metazoan fossil record. 7. Protists dominated major environments (shelves and reefs) starting with a significant radiation in the Ordovician, followed by extinctions and other radiations until most died out at the end of the Permian. 8. In the Mesozoic, new planktic protozoa and algae appeared and radiated in pelagic environments. 9. Modern protists are important at all trophic levels in the oceans and a huge number terrestrial, parasitic and symbiotic protists must have existed for much of geologic time as well. 10. The future of protists is likely in jeopardy, just like most reefal, benthic, and planktic metazoans. An urgent need to understand the role of protists in modern threatened oceans should be addressed soon.

An Aerobic Walking Program to Promote Physical Fitness in Older Blind Adults

1985 ◽  
Vol 79 (3) ◽  
pp. 97-99 ◽  
Author(s):  
Donald Mark Weitzman
Keyword(s):  
Physical Fitness ◽  
Critical Role ◽  
Indirect Evidence ◽  
Well Being ◽  
Fitness Program ◽  
Fast Walking ◽  
The Past ◽  
Walking Program ◽  
Group Fitness

Both direct and indirect evidence gathered over the past 40 years strongly suggest that personal exercise can play a critical role in one's emotional and physical well-being. This article describes a unique group fitness program that combines Fast walking with safe calisthenics. The program is especially suitable for older blind adults who get very little healthful exercise and experience considerable depression.

Perspectives on the Evolution and Diversification of the Diatoms

2007 ◽  
Vol 13 ◽  
pp. 1-12 ◽  
Author(s):  
Matthew L. Julius
Keyword(s):  
Molecular Clock ◽  
Fossil Record ◽  
Early Jurassic ◽  
Late Triassic ◽  
Evolutionary Relationships ◽  
Data Sets ◽  
Diatom Species ◽  
Generic Level ◽  
Existing Data

The understanding of diatom evolution has progressed greatly over the last two decades. Existing data sets have been reanalyzed, new data sets have been generated, and new tools have been employed. Hindering progress is the seemingly endless number of diatom species remaining to be described and relative small number of investigators active in the field. This problem is further confounded by the dramatic reorganization of generic level classification in the group. Despite these problems, many conclusions can be made about prior hypotheses concerning the group's development. Most notably, the origin of the diatoms can be bracketed between the Late Triassic and Early Jurassic using fossil record and molecular clock estimates. This combination of techniques has also provided consensus and clarification to the origin and duration of specific lineages enhancing our understanding of the group's diversification, early ecology, and evolutionary relationships.

scholarly journals Diversity-dependence brings molecular phylogenies closer to agreement with the fossil record

2011 ◽  
Vol 279 (1732) ◽  
pp. 1300-1309 ◽  
Author(s):  
Rampal S. Etienne ◽  
Bart Haegeman ◽  
Tanja Stadler ◽  
Tracy Aze ◽  
Paul N. Pearson ◽  
...  
Keyword(s):  
Standard Model ◽  
Fossil Record ◽  
Evolutionary Dynamics ◽  
Planktonic Foraminifera ◽  
Fossil Evidence ◽  
Rate Of Increase ◽  
The Standard Model ◽  
Molecular Phylogenies ◽  
Biological Realism

The branching times of molecular phylogenies allow us to infer speciation and extinction dynamics even when fossils are absent. Troublingly, phylogenetic approaches usually return estimates of zero extinction, conflicting with fossil evidence. Phylogenies and fossils do agree, however, that there are often limits to diversity. Here, we present a general approach to evaluate the likelihood of a phylogeny under a model that accommodates diversity-dependence and extinction. We find, by likelihood maximization, that extinction is estimated most precisely if the rate of increase in the number of lineages in the phylogeny saturates towards the present or first decreases and then increases. We demonstrate the utility and limits of our approach by applying it to the phylogenies for two cases where a fossil record exists (Cetacea and Cenozoic macroperforate planktonic foraminifera) and to three radiations lacking fossil evidence ( Dendroica , Plethodon and Heliconius ). We propose that the diversity-dependence model with extinction be used as the standard model for macro-evolutionary dynamics because of its biological realism and flexibility.

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