Three representative species of Antirrhinum, in the wild (right) or grown together in a glasshouse (left). A. majus has been used as a genetic model since the 1900s1 and was domesticated from wild populations in SW France and NE Spain, where it grows in competition with other plants. A. charidemi is endemic to the driest place in mainland Europe - Cabo de Gata in SE Spain - and has very small leaves and flowers. A. molle is an alpine found on rock faces in the Pyrenees. Like many alpines, its leaves are covered with dense hairs, giving them a grey appearance and the plant its name (molle = soft).
We have made genetic recombination maps from hybrids between species2,3and used them to map genes responsible for differences in flower colour, different aspects of morphology including heteroblasty, leaf shape and size4, and that underlie the co-evolution of leaves and petals within the species group5. This has been done with collaborators that include Enrico Coen, JIC, and Andrew Bangham, UEA. We are using map-based cloning and Antirrhinum's endogenous transposons as tags to isolate genes that have major role in species differences.
To place these findings in a phylogenetic context, we have examined the evolutionary relationships between Antirrhinum species. Like many groups of Mediterranean plants, the species are young and show little sequence diversity6. Ancestral lineages can, however, be identified using populations and samples of populations and large numbers of nuclear and chloroplast markers. These further suggests that the ancestral forms (large, upright competitors or small prostrate alpines) have hybridised repeatedly, but that ancestal forms have been reselected from hybrids - a process that continues where the two forms grow in proximity7. Genetic analysis has suggested that ancestral combinations of many different genes are reselected and these genes are being identified in natural populations and artificial hybrids (supported by NERC).
Most of the characters that distinguish species are controlled by multiple genes. However, the density of leaf and stem trichomes (hairs) largely reflects variation at a single locus, which we have mapped to a short chromosome interval as the first steps in gene identification. Antirrhinum species also vary in trichome morphology - all trichomes are multicellular, but differ in length, cell number and the presence or absence of a secretory gland. We have mapped genes underlying this variation and are analysing how they affect morphogenesis at the cellular level.
 Schwarz-Sommer Z, Davies B, Hudson A (2003). An everlasting pioneer: the story of Antirrhinum research. Nature Rev. Genet. 4:657-666. PubMed pdf
 Schwarz-Sommer Z, de Andrade Silva E, Berntgen R, Lönnig W-E, Müller A, Nindl I, Stüber K, Wunder J, Saedler H, Gübitz T, Borking A, Golz JF, Ritter E, Hudson A (2003). A linkage map of an F2 hybrid population of Antirrhinum majus and A. molle. Genetics 163:699-701. PubMed pdf
 Schwarz-Sommer Z, Guebitz T, Weiss J, Gomex di-Marco P, Delgado Benarroch L, Hudson A, Egea-Cortines M (2010). A molecular recombination map for Antirrhinum majus. BMC Plant Biology 10:275 PubMed pdf
 Langlade NB, Feng X, Dransfield T, Copsey L, Hanna AI, Thébaud C, Bangham A, Hudson A, Coen ES (2005). Evolution through genetically controlled allometry space. Proc. Natl. Acad. Sci USA. 102:10221-6. PubMed pdf
 Feng X, Wilson Y, Bowers J, Kennaway R, Bangham A, Hannah A, Coen E, Hudson A (2009). Evolution of allometry in Antirrhinum. Plant Cell 21:2999-3007. PubMed pdf
 Gübitz T, Caldwell A, Hudson A (2003). Rapid molecular evolution of CYCLOIDEA-like genes in Antirrhinum and its relatives. Mol. Biol. Evol. 20:1537-44. PubMed pdf
 Wilson Y, Hudson A (2011). The evolutionary history of Antirrhinum suggests that ancestral phenotype combinations survived repeated hybridisation. The Plant Journal 66:1032-43. PubMed pdf
 Platt A, Horton M, Hwang YS, Li Y, Anastasio AE, Mulyati NW, Agren J, Bossdorf O, Byers D, Donohue K, Dunning M, Holub EB, Hudson A, Le Corre V, Loudet O, Roux F, Warthmann N, Weigel D, Rivero L, Scholl R, Nordborg M, Bergelson J, Borevitz JO (2010). The scale of population structure in Arabidopsis thaliana. PLoS Genetics 6: PubMed pdf