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Michael Eason hiking in Anza-Borrego Desert State Park to observe Washingtonia filifera in situ
Currently at San Antonio Botanic Garden, Michael's work has...
Amy Byrne | Feb 15, 2023
An exhibition that beautifully depicts and locates oaks
Roderick Cameron | Feb 09, 2023
Burke Oak Collection at New York Botanical Garden
The Coleman and Susan Burke Oak Collection at The New York...
Todd Forrest | Feb 08, 2023

Plant Focus

Quercus xjackiana acorns
The hybrid of Q. alba and Q. bicolor

#Oaktober Readings

During the month of October, I am posting daily tweets referring to readings related to Quercus. These readings comprise 31 papers that have been important to my thinking on the origins, maintenance and implications of oak diversity. Because they are only 31, many important references have been missed, even papers by whole research groups who have influenced my thinking. The references are being posted chronologically, so if someone follows for the month, they get a sort-of-historical and somewhat idiosyncratic view of oak diversity research. I hope, however, that these readings provide a broader perspective on oak research in general, or provide enjoyment to others as they have to me. Follow me on Twitter (@AndrewLHipp) or the hashtag #Oaktober to get the daily updates.

[Click on the images below to access the readings]

#Oaktober reading #1

Trelease 1924, The American Oaks.

The greatest monographer of America's ca. 225 oaks, Trelease gave us insight into the species, their variation, the diagnostic characters, their relationships. Understanding American oaks starts here.


#Oaktober reading #2

Camus 1936, Les chênes.

The most comprehensive global monograph of the genus, Mme Camus' work laid the foundation for modern classification. Go to it for both the biology and the taxonomy.


#Oaktober reading #3

 Anderson, Introgressive Hybridization.

This slender monograph is a clear introduction to how introgression may shape species evolution, what it looks like, and how biologists can recognize and quantify it. Yet it never mentions oaks!


#Oaktober reading #4

Hardin 1975, Hybridization and introgression in Quercus alba.

A foundational study of the E. North American white oak syngameon, all interbreeding but still good species. The face that launched a thousand ships? Perhaps not, but a touchstone.


#Oaktober reading #5

 Van Valen 1976, Ecological Species, Multispecies, and Oaks.

“It may well be that Q. macrocarpa in Quebec exchanges many more genes with local Q. bicolor than it does with Q. macrocarpa in Texas" – ecology and selection maintain oak spp.

Van Halen

#Oaktober reading #6

Axelrod 1983, Biogeography of Oaks in the Arcto-Tertiary Province.

A key account of the northern origin of oaks, in situ diversification, and alliance between eastern North American and Eurasian white oaks. Axelrod is foundational oak biogeography.


#Oaktober reading #7

Manos and Fairbrothers 1987, Allozyme Variation in Populations of Six Northeastern American Red Oaks (Fagaceae: Quercus Subg. Erythrobalanus).

The first to investigate oak divergence using isozymes, demonstrated that genetic differences among species are much lower than morphology predicts . . . geneflow + ILS.


#Oaktober reading #8

Whittemore and Schaal 1991, Interspecific gene flow in sympatric oaks.

The first to demonstrate that chloroplasts are shared by geography, not species, in oaks . . .  1st confirmation of gene flow in oaks from nuclear and cpDNA sequencing.


#Oaktober reading #9

Kremer and Petit 1993, Gene diversity in natural populations of oak species.

This key isozyme review (33 species) shows high nuclear diversity + low chloroplast diversity within populations, with low among-population divergence, is universal in oaks.


#Oaktober reading #10

Sork et al 1993, Evidence for Local Adaptation in Closely Adjacent Subpopulations of Northern Red Oak (Quercus rubra L.) Expressed as Resistance to Leaf Herbivores.

Local adaptation for herbivore resistance among habitats within red oak, in a single 4 ha plot, in spite of rampant gene flow within the species. Selection beats gene flow . . . but when?


#Oaktober reading #11 

Nixon 1993, Infrageneric classification of Quercus (Fagaceae) and typification of sectional names.

Stabilized sectional nomenclature for North American oaks; provided a hypothesis for phylogenetic studies of the coming decade and the framework for the 1997 FNA treatment of North American oaks.


#Oaktober reading #12

Dow & Ashley 1996, Microsatellite analysis of seed dispersal and parentage of saplings in bur oak, Quercus macrocarpa.

Foundational demo that long-distance pollen-dispersal is key to parentage of bur oak seedlings, & the role of relatively few parent trees in forming the next gen.


#Oaktober reading #13

Dumolin-Lapegue et al 1997, Phylogeographic Structure of White Oaks Throughout the European Continent.

Reconstructs the history of European oak refugia and shows rampant chloroplast sharing among species. A personal favorite . . . see if the figure below doesn't give you chills


#Oaktober reading #14

Manos et al 1999, Phylogeny, Biogeography, and Processes of Molecular Differentiation in Quercus Subgenus Quercus (Fagaceae).

The phylogeny that started it all: reality of the American oak clade, American origin of Eurasian white oaks, ancient phylogenetic split in the golden-cup oaks and hybridization with the white oaks . . .


#Oaktober reading #15

Muir et al 2000, Species status of hybridizing oaks.

A singular demonstration that widely distributed European white oaks clustered genetically by species, not geography; the cleanest example at that time of oak species cohesion.


#Oaktober reading #16

Petit et al. 2004, Hybridization as a mechanism of invasion in oaks.

Used landscape genetics and post-glacial migration history to argue that widespread European white oaks leap-frog across the continent, moving through hybridization.


#Oaktober reading #17

Cavender‐Bares et al 2004, Phylogenetic Overdispersion in Floridian Oak Communities.

Demonstrated ecological divergence within white and red oaks and convergence both shape co-occurrence patterns in species-rich North Central Florida. Key in development of phyloecology.


#Oaktober reading #18

Dodd & Afzal-Rafii 2004, Selection and Dispersal in a a Multispecies Oak Hybrid Zone.

Multispecies introgression in CA red oaks, with alleles well outside parental range and climate shaping admixture proportions. Important early suggestion of adaptive gene flow.


#Oaktober reading #19

Scotti-Santaigne et al. 2004, Genome Scanning for Interspecific Differentiation Between Two Closely Related Oak Species [Quercus robur L. and Q. petraea (Matt.) Liebl.]

Used genetically mapped markers to show that divergence between closely related oak species is genomically heterogeneous, and widespread but clustered.


#Oaktober reading #20

Valencia 2004, Diversidad del género Quercus en México. 

Landmark study of Mexican Quercus, summarizing taxonomic rearrangements that establish our current view of Mexican oak diversity. So much left to do in this hyper-diverse flora!


#Oaktober reading #21

Pearse and Hipp 2009, Phylogenetic and trait similarity to a native species predict herbivory on non-native oaks.

An early well-supported species-level phylogeny of oaks demonstrates that phylogeny trumps traits in explaining oak insect herbivory. 


#Oaktober reading #22

le Hardy de Beaulieu & Lamant 2010, Guide illustré des chênes.

Most comprehensive modern guide to the oaks, richly illustrated with field photos, mostly by the authors. Indispensable to the global oak enthusiast.


#Oaktober reading #23

Peñaloza-Ramírez et al 2010, Interspecific gene flow in a multispecies oak hybrid zone in the Sierra Tarahumara of Mexico.

Demonstrates multispecies hybridization among 3 differentiated Mexican red oaks with morphometric and genetic data. We need more studies at this scale.

Penaloza Ramirez

#Oaktober reading #24

Rodriguez-Correa et al 2015. How Are Oaks Distributed in the Neotropics? A Perspective from Species Turnover, Areas of Endemism, and Climatic Niches.

High species turnover and biogeographic barriers shape broad scale diversity patterns of Mexican oaks. Making sense of high diversity in a rich landscape.


#Oaktober reading #25

Chassé 2016, Eating Acorns: What Story do the Distant, Far, and Near Past Tell Us, and Why?

Acorns have likely been an important human food source for most of our history, even in the Fertile crescent. Not a famine food: a food of choice.


#Oaktober reading #26

Truffaut et al 2017, Fine‐scale species distribution changes in a mixed oak stand over two successive generations.

Reproductive output shapes shift toward Quercus petraea. Two successive generations in a densely-sampled 2-species stand. Key to understanding succession with climate change.


#Oaktober reading #27

McVay et al 2017, A genetic legacy of introgression confounds phylogeny and biogeography in oaks.

Rigorous study of genomic incongruence demonstrates ancient introgression between Eurasian white oaks and distantly related Quercus pontica, and Eastern North American origins of the former.


#Oaktober reading #28

Denk et al 2017, An Updated Infrageneric Classification of the Oaks: Review of Previous Taxonomic Schemes and Synthesis of Evolutionary Patterns.

Summarizing molecular phylogenetic studies, morphology and fossils, this book chapter provides the most robust and current classification of the genus, the subgenera and sections to use.


#Oaktober reading #29

Plomion et al 2018, Oak genome reveals facets of long lifespan.

The first published, well-annotated oak genome (~26K genes) demonstrating the expansion of disease-resistance genes in trees and quantifying the rate of somatic mutations in long-lived oaks.


#Oaktober reading #30

Cavender-Bares 2019, Diversification, adaptation, and community assembly of the American oaks (Quercus), a model clade for integrating ecology and evolution.

A great review of ecological and genetic work demonstrating how important oaks are to temperate terrestrial biodiversity. If you read only one oak paper this month, make it this one.


#Oaktober reading #31

Leroy et al 2019, Adaptive introgression as a driver of local adaptation to climate in European white oaks.

Addresses one of the key questions for the coming decade: how does hybridization shape adaptation? Introgression may be the sharpest arrow in the Quercus quiver.