Case Study Clarkia Clarkia tenella Rachel Jabaily Cody Williams 3 27 2007 Outline The genus Clarkia Origin of gracilis Origin of rhomboidea A couple of general origins and implications of polyploids aneuploids Clarkia Onagraceae Genus of 42 species of annual flowering plants Endemic to temperate Western North america except one species Clarkia tenella which occurs in South America Studied extensively gene duplications speciation pollination biology floral development Wide range of chromosome numbers From diploids of n 5 9 to allo and autopolyploids of n 12 14 17 18 and 26 Lewis Lewis 1955 The origin of Clarkia gracilis Clarkia gracilis ssp albicaulis Dean Wm Taylor Parental diploids C gracilis s 14 chromosomes suggests allotetraploid formation from two n 7 diploid parents H kansson suggested that one parent was likely C amoena Hiorth suggested based on morphological data that the other parent was C arcuata This was later ruled out by H kansson using cytological evidence Lewis Lewis suggested that C lassenensis was the second parent Distribution Clarkia Gracilis Clarkia gracilis is divided into 4 subspecies Sympatric distributions and hybridization commonthough not universal C arcuata C lassenensis C a ssp huntiana Geographical relationship to putative parents C amoena ssp Huntiana and C lassenensis C lassenensis and C amoena ssp huntiana Abdel Hameed Snow 1971 Inferred relationships In nature Inferred relationships Greenhouse progeny Abdel Hameed Snow 1971 Cytological observations Clarkia concinna Bart and Susan Eisenberg Pairs Chains and Rings Ring Chain Bivalents Lewis Raven 1958 Snow Imam 1964 Translocations Forming a chain Species A Species B Translocations Forming a ring Species A Species B Cytological observations Interspecific hybrids Examined crosses between species C amoena and C lassenensis with C gracilis amoena X gracilis highly successful 7 amoena chromosomes paired very regularly with one set of 7 chrmomosomes in gracilis Other set of 7 chromosomes in gracilis left as univalents or occasionally pairing nonhomologously Cytological observations Interspecific hybrids Examined crosses between species C amoena and C lassenensis with C gracilis lassenensis X gracilis Difficult to obtain and relatively unsuccessful Best association was a chain of 5 chromosomes also found a 3 chromosome chain Largest number of bivalents found was 5 Others merely formed 21 univalents Formation of 3c and 5c suggests some relatedness of some chromosomes of the genomes but less than would be expected for homologous genomes also suggests at least 2 translocations Cytological observations Interspecific hybrids Examined crosses between species C amoena and C lassenensis with C gracilis amoena X lassenensis Putative parents of Clarkia gracilis Both are n 7 diploids Strong isolationg mechanisms Cytological observations Synthetic alloploids Amphidiploids of F1 hybrids formed by selfpollination as well as by crosses between F1s Selfings of F1 plants 1000 selfings of F1 hybrids produced only one capsule with three normal seeds only two germinated and only one grew to maturity The mature plant was shown to posses 27 chromosomes fertilization between 13 and 14 chromosome gametes Cytological observations Synthetic alloploids Amphidiploids of F1 hybrids formed by selfpollination as well as by crosses between F1s Crosses between F1 plants several hundred crosses produced only one seed which set and grew to maturity The mature plant possessed 28 chromosomes and was found to have been produced by fertilization between two unreduced gametes Meiotic pairing at M1 was excellent Cytological observations Diploid F1 X C gracilis Desired crosses between the synthetic and natural tetrapliods but colchicine treatments of diploid F1s failed So hybrids were obtained by crossing F1 hybrids with the four gracilis subspecies Proved much more successful than crosses between F1 hybrids Many bivalents Several 3c Conclusions Little homology between C amoena ssp huntiana and C lassenensis Supported by irregular meiotic behavior and difficulty in obtaining F1 hybrids sterility of F1s Poor pairing observed between C lassenensis and C gracilis suggest significant differences between the two Pairing that occured differed from standard C lassenensis by at least two translocations Conclusions C gracilis combines one subgenome of C amoena ssp huntiana and another from a diploid Clarkia in the section Flexicaulis What species is the donor of the second subgenome Two hypotheses C lassenensis IS the donor Would suggest that the lassenensis genome has undergone significant rearrangement Pre gracilis C lassenensis is cytologically very uniform in natural populations Post gracilis inter intragenome changes Consistently found 7 bivalents with C amoena X C gracilis crosses Would have seen multiple associations Could argue that sympatric associations between C amoena C gracilis resulted in a closer structural arrangement An extinct member of Flexicaulis Supported by several observations low homology between Clarkia gracilis and the extant species of Flexicaulis Morphological similarity of Clarkia gracilis to Clarkia arcuata especially Clarkia gracilis ssp albicaulis Geographical location of Clarkia gracilis and members of Flexicaulis Ecological preference for serpentine soils which is a characteristic edaphic feature of Clarkia arcuata Clarkia amoena ssp huntiana Clarkia arcuata Br Alfred Brousseau Saint Mary s College F l e x i c a u l i s George W Hartwell Clarkia lassenensis Steve Matson Clarkia gracilis ssp albicaulis Jo Ann Ordano CAS The origin of Clarkia rhomboidea Clarkia rhomboidea Steve Matson Lewis Lewis 1955 Clarkia rhomboidea Haploid chromosome number of n 12 Wide distribution as well as several disjunct populations Wide range of habitats Wide range of flower pollination Lewis lewis 1955 proposed that parents were C mildrediae n 7 and C virgata n 5 Mosquin 1963 Clarkia virgata Clarkia mildrediae Dean Wm Taylor Dean Wm Taylor Clarkia mildrediae Michelle Cloud Hughes Hybrids C mildrediae X C rhomboidea 25 7 pr 5 un other 75 chains of 3 4 and 5 chromosomes C virgata X C rhomboidea Regular 5 pr 7 un Hybrids the sequel C mildrediae X C virgata Produced sterile F1 hybrids These hybrids were morphologically indistinguishable from C rhomboidea Further supports origin of rhomboidea Extensive bivalent pairing as well as chain formation Hybrids completing the trilogy Hybrids of 26 total populations of C rhomboidea Used a strain from Shaver
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