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Tree of Life Reveals Clock-Like Speciation and Diversification (free pdf) + Darwin and paleontology

Ben Creisler

Recent papers about evolution that may be of interest:

S. Blair Hedges, Julie Marin, Michael Suleski, Madeline Paymer, and
Sudhir Kumar (2015)
Tree of Life Reveals Clock-Like Speciation and Diversification.
Molecular Biology and Evolution 32 (4): 835-845
Free pdf:

Genomic data are rapidly resolving the tree of living species
calibrated to time, the timetree of life, which will provide a
framework for research in diverse fields of science. Previous analyses
of taxonomically restricted timetrees have found a decline in the rate
of diversification in many groups of organisms, often attributed to
ecological interactions among species. Here, we have synthesized a
global timetree of life from 2,274 studies representing 50,632 species
and examined the pattern and rate of diversification as well as the
timing of speciation. We found that species diversity has been mostly
expanding overall and in many smaller groups of species, and that the
rate of diversification in eukaryotes has been mostly constant. We
also identified, and avoided, potential biases that may have
influenced previous analyses of diversification including low levels
of taxon sampling, small clade size, and the inclusion of stem
branches in clade analyses. We found consistency in time-to-speciation
among plants and animals, ~2 My, as measured by intervals of crown and
stem species times. Together, this clock-like change at different
levels suggests that speciation and diversification are processes
dominated by random events and that adaptive change is largely a
separate process.





Warren D. Allmon (2015)
Darwin and palaeontology: a re-evaluation of his interpretation of the
fossil record.
Historical Biology (advance online publication)

Charles Darwin's empirical research in palaeontology, especially on
fossil invertebrates, has been relatively neglected as a source of
insight into his thinking, other than to note that he viewed the
fossil record as very incomplete. During the Beagle voyage, Darwin
gained extensive experience with a wide diversity of fossil taxa, and
he thought deeply about the nature of the fossil record. That record
was, for him, a major source of evidence for large-scale
transmutation, but much less so for natural selection or single
lineages. Darwin's interpretation of the fossil record has been
criticised for its focus on incompleteness, but the record as he knew
it was extremely incomplete. He was compelled to address this in
arguing for descent with modification, which was likely his primary
goal. Darwin's gradualism has been both misrepresented and
exaggerated, and has distracted us from the importance of the fossil
record in his thinking, which should be viewed in the context of the
multiple, sometimes competing demands of the multifaceted argument he
presented in the Origin of Species.