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ITS 797 bp long, 161 parsimony informative characters

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P.angustifolia. P.glutinosa. P.minima. P.spectabilis. P.clusiana. P.palinuri. ITS 3F. Heterostyles. Leu F. P.nutans. Secondary Homostyles. ITS 4R. ITS 1F. ITS 2R. P.secundiflora. P. egaliksensis (4n) P. incana (6n) P. laurentia (8n) P. scotia (6n) P. scandinavica (8n)

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P.angustifolia

P.glutinosa

P.minima

P.spectabilis

P.clusiana

P.palinuri

ITS 3F

Heterostyles

Leu F

P.nutans

Secondary Homostyles

ITS 4R

ITS 1F

ITS 2R

P.secundiflora

P. egaliksensis (4n)

P. incana (6n)

P. laurentia (8n)

P. scotia (6n)

P. scandinavica (8n)

P. borealis (4n) Heterostyle

P. eximia (2n)

P. nutans (2n)

P. mistassinica (2n)

P. anvilensis (2n)

P. farinosa (2n)

P. modesta (2n)

P. tschuktchorum (2n)

P.tschuktschorum

P.eximia.1

P.eximia.2

?

P. stricta

P.borealis

C26A R

P.modesta

P.laurentiana

P.mistassinica

  • A diploid, heterostylic taxon of Primula occupied a contiguous area

P.incana

P.farinosa

P.stricta

P.frondosa

P.scandinavica

From Johnson & Soltis 1994

Boxed areas represent coding regions

P. farinosa

7

0

4

5

44

16

3

0

20

0

10

0

21

11

1

1

2

2

0

Primula

Phylogeny of the plant genus L.:

Implications for sectional circumscription, relationships and evolution of breeding systems

Suring, Erik,*1 Elena Conti1, Sylvia Kelso2

1University of Alaska Fairbanks 2Colorado College

Background

Traditional Classification

Over 400 species worldwide in 37 sections (Richards 1993)

Based on 15 taxonomic characters, the most informative include:

Chromosome number

Presence of multicellular hairs

Pollen type

Breeding system

Molecular techinques can provide many more informative characters that can improve resolution of relationships.

  • Regions Sequenced
  • Internal Transcribed Spacer (ITS)
    • Nuclear sequence
    • Non-coding region
  • maturase K gene (matK)
    • Chloroplast gene
    • Maternally inherited
  • Both have been used in other intrageneric plant studies
  • Evaluate congruence of chloroplast and nuclear phylogenies
  • Test molecular support of traditional sectional classifications
  • Test Kelso’s hybridization hypotheses
  • Explore distribution of breeding systems and chromosome number

Goals

  • Hybridization Hypothesis
  • An association between secondary homostyly, polyploidy, and extreme arctic or alpine conditions has been reported in Primula.
    • Kelso (1991, 1987) proposed an explanation based on the secondary contact hypothesis (Stebbins 1985).
  • Evidence of hybridization may be evaluated by statistical tests of congruence between nuclear and chloroplast trees
  • Breeding Systems
  • Three breeding systems, according to Richards (1993)
  • Primary homostyly
    • Self-fertile populations with a single morphology and mating type
  • Heterostyly
    • Populations a mix of two flower morphs
    • Morphology and a sporophytic self incompatibility system prevent intramorph fertilization
  • Secondary Homostyly
    • Self-fertile with a single floral morphology
    • Develop when hybridization, and most often polyploidy occurs and recombination disables the heterostyly supergene

P. veris

  • ITS
    • 797 bp long, 161 parsimony informative characters
    • Branch and bound search using parsimony criterion found 15 trees of length 419 and consistency index of 0.8258.
  • Bootstrap Analysis
    • Monophyly of sections Auricula (98%) and Aleuritia (100%) is strongly supported. The monophyly of section Crystallophlomis (55%) is less well supported.
    • Monophyly of subgenera Auriculastratum (98%) and Aleuritia (100%) is well supported.
    • Monophyly of clades based upon chromosome number 2n=22 (100%), 2n=18 (100%) and 2n=66 (98%) is strongly supported.
    • Intrasectional relationships were not well resolved.
  • matK
    • 872 bp long, 79 parsimony informative characters
    • Branch and bound search using parsimony criterion found 3 trees of length 147 and consistancy index of 0.939.
  • Boostrap Analysis
    • Monophyly of section Aleuritia (100%), subgenera Aleuritia (100%) and the clades based on chromosome number 2n=18 (100%) and 2n=22 (100%) are well supported.
    • Other clades suggested by the ITS topology are similar but are not well supported.
  • Preliminary phylogenetic analyses of ITS and matK sequences support:
    • Monophyly of sections Aleuritia and Auricula
    • Base chromosome number as a useful taxonomic character
  • Preliminary support of Kelso’s hypotheses
    • homostylous species grouped with proposed heterostylous progenitors
          • P.eximia with P. tschuktchorum
          • P. stricta with P. farinosa
          • P. incana and P. laurentiana with P. mistassinica
          • P. borealis with P. modesta
    • need increased matK and ITS sampling to further resolve the relationships
      • equal sample sizes would allow statistical tests of congruence

Results

Conclusions

  • Diploid, heterostylous populations of Primula became isolated because of habitat fragmentation caused by climate changes, for example Quaternary glacial peaks
  • Secondary homostylous taxa successfully colonized the new habitats opened by glacial retreat.
  • Glacial retreat allowed separated and partially differentiated diploid taxa to come into contact and hybridize, giving rise to polyploid taxa
  • Recombination in the heterostyly supergene gave rise to secondary homostylous taxa

Reciprocal herkogamy found in heterostylic primulas. Compatible pollinations are indicated by the arrows. Polymorphisms associated with distyly include anther and

stigma length, pollen size, and stigmatic papillae size (from Barret and Cruzan, 1994).

ITS

36

matK

Section

Auricula

22

2n=66

100

Subgenus

Auriculastrum

14

10

72

98

P.angustifolia

8

9

21

2n=198

17

P.borealis.1

99

2n=36

15

Armerina

Sikkimensis

Section

Aleuritia

P.borealis.2

88

100

13

18

2n=126

P.stricta

100

2n=18

2n=22

22

85

43

Section

Crystallophlomis

55

2n=72

4

P.laurentiana

Subgenus

Aleuritia

58

100

5

0

Armerina

P.nutans

1

0

85

2n=36

P.eximia

100

Section

Crystallophlomis

5

100

45

2n=22

P.tschuktschorum

9

Subgenus

Aleuritia

89

2n=72

10

0

Sikkimensis

P.secundiflora

2n=18

Section

Aleuritia

15

2n=54

P.glutinosa

100

2

50

Subgenus

Auriculastrum

Section

Auricula

82

Funding was provided by the UAF Office of Arctic Research Undergraduate Research Opportunities Program and The Research Foundation.

2n=66

46

P.palinuri

7

54

4

2n=126

10

P.minima

72

6

6

matK Maximum Parsimony Tree. The numbers on top of the branches are bootstrap values and the numbers below are distance values. Sectional, and subgeneric groupings are shown. Chromosomal and breeding system distributions are shown. Highlighted taxa are secondary homostyles.

4

2n=72

ITS Maximum Parsimony Tree. The numbers on top of the branches are bootstrap values and the numbers below are distance values. Sectional, and subgeneric groupings are shown. Chromosomal and breeding system distributions are shown. Highlighted taxa are secondary homostyles.

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