Spotted knapweed is a short-lived perennial native to eastern Europe (http://www.invasivespeciesinfo.gov/plants/spotknapweed.shtml). Recent classifications place it in subfamily Carduoideae, tribe Cardueae, and subtribe Centaureinae. In the early 1900s the species was introduced to North America, where it has degraded millions of hectares of pastures and rangeland, reducing forage and out-competing native species. European populations include both diploid (n=18) and tetraploid (n=36) cytotypes (http://www.tropicos.org/Project/IPCN), whereas North American populations appear to be exclusively tetraploid. The genome size of the diploid cytotype is circa 861 Mbp (http://data.kew.org/cvalues/).

Unfortunately, in most American literature the name C. maculosa Lamarck has been misapplied to the North American tetraploid cytotype, C. stoebe subsp. micranthos. As a consequence, searches for genomic tools and resources for spotted knapweed should employ both names.

• Nucleotide sequences on GenBank as of 12/2012: link to C. maculosa (427 total) and link to C. stoebe (337 total)
• ESTs (44,886 Sanger reads) on GenBank as of 12/2012: click here (C. maculosa)
• 4-plex NimbleGen microarray (34,343 unigenes; 68,686 features). Note that the NimbleGen array includes 24,545 unigenes from yellow starthistle and 9,798 from spotted knapeed)

We generated the Sanger ESTs described above, which we have used to (1) determine the distribution of whole genome duplications in the Compositae; and (2) explore the extent of hybridization and introgression between diffuse and spotted knapweed.

Barker MS, NC Kane, A Kozik, RW Michelmore, M Matvienko, SJ Knapp, and LH Rieseberg. 2008. Multiple paleopolyploidizations during the evolution of the Asteraceae reveal parallel patterns of duplicate gene retention after millions of years. Molecular Biology and Evolution 25:2445-2455.

Lai Z, NC Kane, A Kozik, KA Hodgins, KM Dlugosch, MS. Barker, M Matvienko, Q Yu, KG Turner, SA Pearl, GDM Bell, Y Zou, C Grassa, A Guggisberg, KL Adams, JV Anderson, DP Horvath, RV Kesseli, JM Burke, RW Michelmore, and LH Rieseberg. 2012. Genomics of Compositae weeds: EST libraries, microarrays, and evidence of introgression. American Journal of Botany, In review.