Case Study: ClarkiaPowerPoint PresentationOutlineClarkia (Onagraceae)Slide 5The origin of Clarkia gracilisParental diploidsDistribution Clarkia GracilisSlide 9Cytological observationsSlide 11Translocations: Forming a chainTranslocations: Forming a ringCytological observations: Interspecific hybridsSlide 15Slide 16Cytological observations: Synthetic alloploidsSlide 18Cytological observations: Diploid F1 X C. gracilisConclusionsSlide 21C.lassenensis IS the donorAn extinct member of FlexicaulisSlide 24The origin of Clarkia rhomboideaSlide 26Clarkia rhomboideaSlide 28Slide 29Slide 30HybridsHybrids: the sequelHybrids:completing the trilogySlide 34Slide 35Distribution of arrangementsResults of the hybridizationsSummary of arrangementsSlide 39Slide 40Slide 41Effects of rearrangements: Pollen fertilitySlide 43Effects of polyploidy on C.rhomboideaSlide 45Origin of Clarkia rhomboideaSlide 47Distribution change since Wisconsin glaciationGeneral polyploidy and aneuploidySlide 50Distribution and habitatSpeciationPolyploidyPolyploids and rangeSlide 55Slide 56Slide 57Slide 58Case Study: ClarkiaCody Williams3.27.2007Rachel JabailyClarkia tenellaOutlineThe genus ClarkiaOrigin of gracilisOrigin of rhomboideaA couple of general origins and implications of polyploids/aneuploidsClarkia (Onagraceae)Genus of 42 species of annual flowering plantsEndemic 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 26Lewis & Lewis, 1955The origin of Clarkia gracilisDean Wm. TaylorClarkia gracilisssp. albicaulisParental diploidsC. gracilis’s 14 chromosomes suggests allotetraploid formation from two n=7 diploid parentsHåkansson suggested that one parent was likely C.amoenaHiorth suggested (based on morphological data) that the other parent was C.arcuataThis was later ruled out by Håkansson using cytological evidenceLewis & Lewis suggested that C.lassenensis was the second parentDistribution Clarkia GracilisClarkia gracilis is divided into 4 subspeciesSympatric distributions and hybridization common-though not “universal”Geographical relationship to putative parents-C. amoena ssp. Huntiana and C.lassenensisC.lassenensis and C.amoena ssp. huntiana Abdel-Hameed & Snow, 1971C. a. ssp. huntianaC. lassenensisC. arcuataAbdel-Hameed & Snow, 1971Inferred relationships:In natureInferred relationships:Greenhouse progenyCytological observationsClarkia concinna Bart and Susan EisenbergLewis & Raven, 1958ChainPairs, Chains and RingsBivalentsRingSnow & Imam, 1964Translocations: Forming a chainSpecies ASpecies BTranslocations: Forming a ringSpecies ASpecies BCytological observations:Interspecific hybridsamoena X gracilis highly successful7 amoena chromosomes paired very regularly with one set of 7 chrmomosomes in gracilisOther set of 7 chromosomes in gracilis left as univalents or occasionally pairing non-homologouslyExamined crosses between species: C.amoena and C.lassenensis with C.gracilisCytological observations:Interspecific hybridslassenensis X gracilis Difficult to obtain and relatively unsuccessfulBest association was a chain of 5 chromosomes (also found a 3 chromosome chain) Largest number of bivalents found was 5Others merely formed 21 univalentsFormation 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)Examined crosses between species: C.amoena and C.lassenensis with C.gracilisCytological observations:Interspecific hybridsamoena X lassenensis Putative parents of Clarkia gracilisBoth are n=7 diploidsStrong isolationg mechanismsExamined crosses between species: C.amoena and C.lassenensis with C.gracilisCytological observations:Synthetic alloploidsAmphidiploids of F1 hybrids formed by self-pollination as well as by crosses between F1sSelfings of F1 plants1000 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)70% pollen viability and high seed setCytological observations:Synthetic alloploidsAmphidiploids of F1 hybrids formed by self-pollination as well as by crosses between F1sCrosses between F1 plantsseveral hundred crossesproduced only one seed which set and grew to maturityThe mature plant possessed 28 chromosomes and was found to have been produced by fertilization between two unreduced gametesMeiotic pairing at M1 was excellentCytological observations:Diploid F1 X C. gracilisDesired 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 subspeciesProved much more successful than crosses between F1 hybridsMany bivalentsSeveral (3c)ConclusionsLittle homology between C.amoena ssp. huntiana and C.lassenensisSupported by irregular meiotic behavior and difficulty in obtaining F1 hybrids, sterility of F1sPoor 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 translocationsConclusionsC.gracilis combines one subgenome of C.amoena ssp. huntiana and another from a diploid Clarkia in the section FlexicaulisWhat species is the “donor” of the second subgenome?--Two hypotheses--C.lassenensis IS the donorWould suggest that the lassenensis genome has undergone significant rearrangementPre-gracilis- C.lassenensis is cytologically very uniform in natural populationsPost-gracilis- inter/intragenome changesConsistently found 7 bivalents with C.amoena X C.gracilis crossesWould have seen multiple associationsCould argue that sympatric associations between C.amoena/C.gracilis resulted in a closer structural arrangementAn extinct member of FlexicaulisSupported by several observations:low homology between Clarkia gracilis and the extant species of FlexicaulisMorphological similarity of Clarkia gracilis to Clarkia arcuata (especially Clarkia gracilis ssp. albicaulis)Geographical location of Clarkia gracilis and members of FlexicaulisEcological preference for serpentine soils which is a characteristic
View Full Document
Unlocking...