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The oak tree in Skjomendalen © Gerhard Sørensen-Fuglem and Cecilia Piccirilli Bjerkeset
An oak grows north of the Arctic Circle in Norway
Website Editor | Aug 14, 2023
Unusual symptoms linked to phytoplasma infection in Quercus humboldtiii, Colombia © Eric Boa
Symptoms linked to phytoplasma infection found in Quercus...
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Different names are being used for one species.
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Plant Focus

A small but mature Alabama sandstone oak producing acorns © Patrick Thompson
A Critically Endangered dwarf oak 

Disentangling the Phylogenetic Network of the California Red Oaks

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Richard S. Dodd and Prahlada Papper

Published May 2019 in International Oaks No. 30: 203–208


The Red Oaks of California form a clade of four species that is distinct from Eastern North American Red Oaks. Of these four species, the Quercus wislizeni/Q. parvula complex has posed greatest confusion. We conducted a phylogenetic study of the clade, including a number of individuals of the two named varieties of Q. parvula from different localities. To improve phylogenetic signal, we removed individuals with a signal of recent admixture. The resulting maximum likelihood tree identified all four named species and both varieties as distinct clusters. However, the Purisima population of Q. parvula var. parvula appeared to be more related to the Palo Colorado population of Q. parvula var. shrevei than to its putative sister population on Santa Cruz Island. The population tree based on branch concordance factors from gene trees supported the same topology, but concordance factors were low for the Q. parvula clade, suggesting possible incomplete lineage sorting.


Evolution, RADseq, phylogenetic networks, ancient hybridization, Quercus parvula var. shrevei, Quercus parvula var. parvula


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