Michael S Barker
Associate Professor
Associate Professor, BIO5 Institute
Primary Department
(520) 621-2213
Research Interest
Michael Barker is an evolutionary biologist studying the origins of biological diversity, particularly how abrupt genomic changes such as polyploidy, chromosomal change, and hybridization have contributed to the evolution of plant diversity. Biologists have long been fascinated by these processes because they create unique opportunities for the evolution of ecological and phenotypic novelty with the potential for relatively rapid speciation. Although assessing the importance of these abrupt changes has historically been a difficult task, advances in genomics and bioinformatics have created new opportunities for addressing these longstanding questions. By integrating new computational and evolutionary genomic tools with traditional approaches such as molecular evolution, phylogenetics, mathematical modeling, and experimental work Barker's lab currently studies 1.) the contributions of recent and ancient polyploidy to eukaryotic diversity; 2.) the evolution of chromosome number and genome organization; and 3.) the impact of hybridization on speciation and novelty.


Barker, M., Arrigo, N., Albert, L. P., Mickelson, P. G., & Barker, M. S. (2012). Quantitative visualization of biological data in Google Earth using R2G2, an R CRAN package. Molecular ecology resources, 12(6).

We briefly introduce R2G2, an R CRAN package to visualize spatially explicit biological data within the Google Earth interface. Our package combines a collection of basic graph-editing features, including automated placement of dots, segments, polygons, images (including graphs produced with R), along with several complex three-dimensional (3D) representations such as phylogenies, histograms and pie charts. We briefly present some example data sets and show the immediate benefits in communication gained from using the Google Earth interface to visually explore biological results. The package is distributed with detailed help pages providing examples and annotated source scripts with the hope that users will have an easy time using and further developing this package. R2G2 is distributed on http://cran.r-project.org/web/packages.

Arrigo, N., & Barker, M. S. (2012). Rarely successful polyploids and their legacy in plant genomes. Current Opinion in Plant Biology, 15(2), 140-146.

PMID: 22480430;Abstract:

Polyploidy, or whole genome duplication, is recognized as an important feature of eukaryotic genome evolution. Among eukaryotes, polyploidy has probably had the largest evolutionary impact on vascular plants where many contemporary species are of recent polyploid origin. Genomic analyses have uncovered evidence of at least one round of polyploidy in the ancestry of most plants, fueling speculation that genome duplications lead to increases in net diversity. In spite of the frequency of ancient polyploidy, recent analyses have found that recently formed polyploid species have higher extinction rates than their diploid relatives. These results suggest that despite leaving a substantial legacy in plant genomes, only rare polyploids survive over the long term and most are evolutionary dead-ends. © 2012 Elsevier Ltd.

Dempewolf, H., Kane, N. C., Ostevik, K. L., Geleta, M., Barker, M. S., Lai, Z., Stewart, M. L., Bekele, E., M., J., C., Q., & Rieseberg, L. H. (2010). Establishing genomic tools and resources for Guizotia abyssinica (L.f.) Cass.-the development of a library of expressed sequence tags, microsatellite loci, and the sequencing of its chloroplast genome. Molecular Ecology Resources, 10(6), 1048-1058.

PMID: 21565115;Abstract:

We present an EST library, chloroplast genome sequence, and nuclear microsatellite markers that were developed for the semi-domesticated oilseed crop noug (Guizotia abyssinica) from Ethiopia. The EST library consists of 25-711 Sanger reads, assembled into 17-538 contigs and singletons, of which 4781 were functionally annotated using the Arabidopsis Information Resource (TAIR). The age distribution of duplicated genes in the EST library shows evidence of two paleopolyploidizations-a pattern that noug shares with several other species in the Heliantheae tribe (Compositae family). From the EST library, we selected 43 microsatellites and then designed and tested primers for their amplification. The number of microsatellite alleles varied between 2 and 10 (average 4.67), and the average observed and expected heterozygosities were 0.49 and 0.54, respectively. The chloroplast genome was sequenced de novo using Illumina's sequencing technology and completed with traditional Sanger sequencing. No large re-arrangements were found between the noug and sunflower chloroplast genomes, but 1.4% of sites have indels and 1.8% show sequence divergence between the two species. We identified 34 tRNAs, 4 rRNA sequences, and 80 coding sequences, including one region (trnH-psbA) with 15% sequence divergence between noug and sunflower that may be particularly useful for phylogeographic studies in noug and its wild relatives. © 2010 Blackwell Publishing Ltd.

Mayrose, I., Zhan, S. H., Rothfels, C. J., Arrigo, N., Barker, M. S., Rieseberg, L. H., & Otto, S. P. (2015). Methods for studying polyploid diversification and the dead end hypothesis: a reply to Soltis et al. (2014). The New phytologist, 206(1), 27-35.
Barker, M. S., Kane, N. C., Matvienko, M., Kozik, A., Michelmore, R. W., Knapp, S. J., & Rieseberg, L. H. (2008). Multiple paleopolyploidizations during the evolution of the compositae reveal parallel patterns of duplicate gene retention after millions of years. Molecular Biology and Evolution, 25(11), 2445-2455.

PMID: 18728074;PMCID: PMC2727391;Abstract:

Of the approximately 250,000 species of flowering plants, nearly one in ten are members of the Compositae (Asteraceae), a diverse family found in almost every habitat on all continents except Antarctica. With an origin in the mid Eocene, the Compositae is also a relatively young family with remarkable diversifications during the last 40 My. Previous cytologic and systematic investigations suggested that paleopolyploidy may have occurred in at least one Compositae lineage, but a recent analysis of genomic data was equivocal. We tested for evidence of paleopolyploidy in the evolutionary history of the family using recently available expressed sequence tag (EST) data from the Compositae Genome Project. Combined with data available on GenBank, we analyzed nearly 1 million ESTs from 18 species representing seven genera and four tribes. Our analyses revealed at least three ancient whole-genome duplications in the Compositae - a paleopolyploidization shared by all analyzed taxa and placed near the origin of the family just prior to the rapid radiation of its tribes and independent genome duplications near the base of the tribes Mutisieae and Heliantheae. These results are consistent with previous research implicating paleopolyploidy in the evolution and diversification of the Heliantheae. Further, we observed parallel retention of duplicate genes from the basal Compositae genome duplication across all tribes, despite divergence times of 33-38 My among these lineages. This pattern of retention was also repeated for the paleologs from the Heliantheae duplication. Intriguingly, the categories of genes retained in duplicate were substantially different from those in Arabidopsis. In particular, we found that genes annotated to structural components or cellular organization Gene Ontology categories were significantly enriched among paleologs, whereas genes associated with transcription and other regulatory functions were significantly underrepresented. Our results suggest that paleopolyploidy can yield strikingly consistent signatures of gene retention in plant genomes despite extensive lineage radiations and recurrent genome duplications but that these patterns vary substantially among higher taxonomic categories. © The Author 2008. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution. All rights reserved.