[dinosaur] Placental Mammal Diversification Across the K-Pg Boundary (free pdf)

Ben Creisler
[email protected]

A new paper in open access:

Free pdf:

Mark S. Springer, Nicole M. Foley, Peggy L. Brady, John Gatesy and William
J. Murphy (2019)
Evolutionary Models for the Diversification of Placental Mammals Across the
KPg Boundary.
Frontiers in Genetics 10: 1241
doi: https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.3389_fgene.2019.01241&d=DwIBaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=N5kwZ16l22YZ-qEdHhyIl3ICRnGPJM0rpXcJi4_AJzE&s=7n8FZyH2oYHVxLcj_CeI974C3uqja_IOb4joysKxQQo&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__www.frontiersin.org_articles_10.3389_fgene.2019.01241_full&d=DwIBaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=N5kwZ16l22YZ-qEdHhyIl3ICRnGPJM0rpXcJi4_AJzE&s=SZmLo7gxs3s04QaCl0dCIQaOFcfiJfl10SO161UrOQM&e= 


Deciphering the timing of the placental mammal radiation is a longstanding
problem in evolutionary biology, but consensus on the tempo and mode of
placental diversification remains elusive. Nevertheless, an accurate
timetree is essential for understanding the role of important events in
Earth history (e.g., Cretaceous Terrestrial Revolution, KPg mass
extinction) in promoting the taxonomic and ecomorphological diversification
of Placentalia. Archibald and Deutschman described three competing models
for the diversification of placental mammals, which are the Explosive, Long
Fuse, and Short Fuse Models. More recently, the Soft Explosive Model and
Trans-KPg Model have emerged as additional hypotheses for the placental
radiation. Here, we review molecular and paleontological evidence for each
of these five models including the identification of general problems that
can negatively impact divergence time estimates. The Long Fuse Model has
received more support from relaxed clock studies than any of the other
models, but this model is not supported by morphological cladistic studies
that position Cretaceous eutherians outside of crown Placentalia. At the
same time, morphological cladistics has a poor track record of
reconstructing higher-level relationships among the orders of placental
mammals including the results of new pseudoextinction analyses that we
performed on the largest available morphological data set for mammals
(4,541 characters). We also examine the strengths and weaknesses of
different timetree methods (node dating, tip dating, and fossilized
birth-death dating) that may now be applied to estimate the timing of the
placental radiation. While new methods such as tip dating are promising,
they also have problems that must be addressed if these methods are to
effectively discriminate among competing hypotheses for placental
diversification. Finally, we discuss the complexities of timetree
estimation when the signal of speciation times is impacted by incomplete
lineage sorting (ILS) and hybridization. Not accounting for ILS results in
dates that are older than speciation events. Hybridization, in turn, can
result in dates than are younger or older than speciation dates.
Disregarding this potential variation in "gene" history across the genome
can distort phylogenetic branch lengths and divergence estimates when
multiple unlinked genomic loci are combined together in a timetree analysis.