@article{barrier_bustamante_yu_purugganan_2003, title={Selection on rapidly evolving proteins in the Arabidopsis genome}, volume={163}, number={2}, journal={Genetics}, author={Barrier, M. and Bustamante, C. D. and Yu, J. Y. and Purugganan, M. D.}, year={2003}, pages={723–733} }
 @article{barrier_robichaux_purugganan_2001, title={Accelerated regulatory gene evolution in an adaptive radiation}, volume={98}, ISSN={["0027-8424"]}, DOI={10.1073/pnas.181257698}, abstractNote={The disparity between rates of morphological and molecular evolution remains a key paradox in evolutionary genetics. A proposed resolution to this paradox has been the conjecture that morphological evolution proceeds via diversification in regulatory loci, and that phenotypic evolution may correlate better with regulatory gene divergence. This conjecture can be tested by examining rates of regulatory gene evolution in species that display rapid morphological diversification within adaptive radiations. We have isolated homologues to theArabidopsis APETALA3(ASAP3/TM6) andAPETALA1(ASAP1) floral regulatory genes and theCHLOROPHYLL A/B BINDING PROTEIN9(ASCAB9) photosynthetic structural gene from species in the Hawaiian silversword alliance, a premier example of plant adaptive radiation. We have compared rates of regulatory and structural gene evolution in the Hawaiian species to those in related species of North American tarweeds. Molecular evolutionary analyses indicate significant increases in nonsynonymous relative to synonymous nucleotide substitution rates in theASAP3/TM6andASAP1regulatory genes in the rapidly evolving Hawaiian species. By contrast, no general increase is evident in neutral mutation rates for these loci in the Hawaiian species. An increase in nonsynonymous relative to synonymous nucleotide substitution rate is also evident in theASCAB9structural gene in the Hawaiian species, but not to the extent displayed in the regulatory loci. The significantly accelerated rates of regulatory gene evolution in the Hawaiian species may reflect the influence of allopolyploidy or of selection and adaptive divergence. The analyses suggest that accelerated rates of regulatory gene evolution may accompany rapid morphological diversification in adaptive radiations.}, number={18}, journal={PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA}, author={Barrier, M and Robichaux, RH and Purugganan, MD}, year={2001}, month={Aug}, pages={10208–10213} }
 @article{barrier_friar_robichaux_purugganan_2000, title={Interspecific evolution in plant microsatellite structure}, volume={241}, ISSN={["0378-1119"]}, DOI={10.1016/S0378-1119(99)00463-1}, abstractNote={Several intragenically linked microsatellites have been identified in the floral regulatory genes A. sandwicense APETALA1 (ASAP1) and A. sandwicense APETALA3/TM6 (ASAP3/TM6) in 17 species of the Hawaiian and North American Madiinae (Asteraceae). Thirty-nine microsatellite loci were observed in the introns of these two genes, suggesting that they are hotspots for microsatellite formation. The sequences of four of these microsatellites were mapped onto the phylogenies of these floral regulatory genes, and the structural evolution of these repeat loci was traced. Both nucleotide substitutions and insertion/deletion mutations may be responsible for the formation of perfect microsatellites from imperfect repeat regions (and vice versa).}, number={1}, journal={GENE}, author={Barrier, M and Friar, E and Robichaux, R and Purugganan, M}, year={2000}, month={Jan}, pages={101–105} }
 @article{barrier_baldwin_robichaux_purugganan_1999, title={Interspecific hybrid ancestry of a plant adaptive radiation: Allopolyploidy of the Hawaiian silversword alliance (Asteraceae) inferred from floral homeotic gene duplications}, volume={16}, ISSN={["0737-4038"]}, DOI={10.1093/oxfordjournals.molbev.a026200}, abstractNote={The polyploid Hawaiian silversword alliance (Asteraceae), a spectacular example of adaptive radiation in plants, was shown previously to have descended from North American tarweeds of the Madia/Raillardiopsis group, a primarily diploid assemblage. The origin of the polyploid condition in the silversword alliance was not resolved in earlier biosystematic, cytogenetic, and molecular studies, apart from the determination that polyploidy in modern species of Madia/Raillardiopsis arose independent of that of the Hawaiian group. We determined that two floral homeotic genes, ASAP3/TM6 and ASAP1, are found in duplicate copies within members of the Hawaiian silversword alliance and appear to have arisen as a result of interspecific hybridization between two North American tarweed species. Our molecular phylogenetic analyses of the ASAP3/TM6 loci suggest that the interspecific hybridization event in the ancestry of the Hawaiian silversword alliance involved members of lineages that include Raillardiopsis muirii (and perhaps Madia nutans) and Raillardiopsis scabrida. The ASAP1 analysis also indicates that the two species of Raillardiopsis are among the closest North American relatives of the Hawaiian silversword alliance. Previous biosystematic evidence demonstrates the potential for allopolyploid formation between members of the two North American tarweed lineages; a vigorous hybrid between R. muirii and R. scabrida has been produced that formed viable, mostly tetraporate (diploid) pollen, in keeping with observed meiotic failure. Various genetic consequences of allopolyploidy may help to explain the phenomenal evolutionary diversification of the silversword alliance.}, number={8}, journal={MOLECULAR BIOLOGY AND EVOLUTION}, author={Barrier, M and Baldwin, BG and Robichaux, RH and Purugganan, MD}, year={1999}, month={Aug}, pages={1105–1113} }