Polyploidy in plants an introduction
Polyploidy in plants an introduction
My credentials?
 selection of Washington
University for Ph.D. work; Walter
Lewis and International Conference
on Polyploidy: Biological
Relevance (May, 1979)
Polyploidy in plants an introduction
 selected to work with Barbara
Schaal & Peter Raven - expert on
polyploid evolution, especially in
California taxa
Polyploidy in plants an introduction
 lab mates with Jeff Doyle - Ph.D.
on polyploid Claytonia (spring
beauty) at Indiana with Charlie
Heiser
 but doing post-doc with Walter
Lewis and Roger Beachy on
polyploidy in Glycine (soybean)
Polyploidy in plants an introduction
 Jeff Doyle was the Ph.D. advisor
of Eve Emshwiller at Cornell
Polyploidy in plants an introduction
 while at Washington University,
Jeff Palmer (then a postdoc at
Stanford, now at Indiana) gave a talk
on molecular phylogenetics
 presented DNA evidence to solve
portions of U’s triangle on Brassica
polyploid evolution
 provided Washington U with
probes to do molecular phylogenetic
work
Polyploidy in plants an introduction
 I went onto Davis for a postdoc
with Les Gottlieb to look at DNA
based relationships of diploids and
polyploids in Clarkia
 for various reasons, other issues in
Clarkia became more important
 Cody Williams is now finishing the
original story first begun in Davis
(and earlier by Raven)
C. purpurea n=26
Polyploidy in plants an introduction
 in 1984, three people vied for the
first two plant molecular systematics
positions in the world at Madison
and Ithaca - myself, Jeff Doyle, and
Jonathan Wendel
Polyploidy in plants an introduction
 Jonathan Wendel now at Ames
switched over into more
evolutionary genomics questions —
e.g. Gossypium polyploidy
Polyploidy in plants an introduction
 Tom Osborn and Keming Song,
UW Agronomy, sat in on my Bot
563 to learn how to phylogenetically
analyze their Brassica data
Polyploidy in plants an introduction
 shortly thereafter, David Spooner
“rotated” in my lab for one year to
learn how to do DNA phylogenetic
analysis on Solanum sect. Petota
 he was kind enough to include me
as author on two papers dealing with
polyploid evolution in this group —
more on that story later
Polyploidy in plants an introduction
 David Baum joined my lab in 1990
as postdoc to do phylogenetic
analysis of Epilobium and relatives
to address chromosome number (and
polyploid) evolution
Polyploidy in plants an introduction
 Chris Pires, my graduate student
and now at U Missouri, does
postdocs with Soltis and Soltis on
Tragopogon and later with Osborn
on Brassica
Polyploidy - a history
 Polyploids - plants containing more than the normal
number (two) sets of chromosomes
 Aneuploids - plants containing fewer or more
chromosomes from the basic (x), or multiples of x,
number of chromosomes
 if x = 6, then a diploid would have 2n = 12 chromosomes
 Polyploids would have 2x = 12 or 2n = 24, for example
— tetraploid (4 sets)
 Aneuploids would have deviated from x = 6, to have 2n
= 10, 2n = 8, or 2n = 14, for example
Polyploidy - a history
 Hugo DeVries - published “Mutation Theory”
in 1901
 polyploid mutants in
Oenothera played an
important role in his work
Oenothera lamarckiana
on book face
Polyploidy - a history
 selected this species in 1886 because
appeared to be good candidate for
“saltational” mutants
 did large-scale greenhouse experiments
to find mutants
Polyploidy - a history
 of many, the ‘gigas’ mutant is
important here as it turned out to be a
spontaneously derived tetraploid (2n=14
is typical for Oenothera)
Polyploidy - a history
 DeVries and Gates had long argument
over the nature of ‘gigas’ in terms of
impact on everything from increase cell
size to more robust plant vigor
Polyploidy - a history
 Eduard Strasburger (1844-1912) founder of modern cytology - first coins
the term ‘polyploid’
Polyploidy - a history
 Winkler (1916) - earliest study of
polyploidy by forming chimaeras
between different species of
Solanum. Tissue of the anther wall
showing high-polyploid cells side
by side with diploid cells.
from Briggs & Walters, 1997
Polyploidy - a history
 O. Winge (1917) - first classic paper on polyploid distinguishes two types of polyploids

autopolyploids - derived within a single individual

allopolyploids - polyploidy succeeding hybridization
 Kihara and Ono (1926) actually coin the terms
‘autopolyploidy’ and ‘allopolyploidy’
Polyploidy - a history
autopolyploidy
allopolyploidy
Polyploidy - a history
 Clausen & Goodsend (1925) form hexaploid tobacco
Nicotiana glutinosa
2n = 24
diploid - 1x
N. tabacum
X
2n = 48
tetraploid - 2x
=
2n = 72
hexaploid - 3x
Polyploidy - a history
 Karpechenko (1925) derives radish X cabbage polyploid
hybrid (Raphanobrassica)
Georgi Karpechenko
(1899-1941)
Polyploidy - a history
 A viable hybrid progeny individual was
produced from seed. However, this hybrid was
functionally sterile because the 9 chromosomes
from the cabbage parent were different enough
from the radish chromosomes that pairs did not
synapse and segregate normally.
 Eventually, one part of the hybrid plant
produced some seeds. On planting, these seeds
produced fertile individuals with 36
chromosomes. They had apparently been derived
from spontaneous, accidental chromosome
doubling to 2n1+2n2 in one region of the sterile
hybrid, presumably in tissue that eventually
became germinal and underwent meiosis.
Unfortunately for Karpechenko, his
allopolyploid had the roots of a
cabbage and the leaves of a radish
Karpechenko in the original ‘cabbage patch’
Polyploidy - formation
 doubled chromosomes in somatic cells (mitosis) or
unreduced gametes (meiosis) occur infrequently but do occur
 experimentally, this can be done by the addition of the
alkaloid colchicine
Polyploidy - formation
Colchicum autumnale meadow saffron
from Briggs & Walters, 1997
Polyploidy - reproductive isolation
Once formed, allopolyploids are
reproductively isolated from other
species of other ploidy levels
Polyploidy - reproductive isolation
Once formed, allopolyploids are
reproductively isolated from other
species of other ploidy levels
from Briggs & Walters, 1997
 Meiosis in a triploid hybrid.
Note mixtures of bivalents
(black) and univalents (white) at
metaphase I of meiosis.
Polyploidy - types
autopolyploidy
allopolyploidy
Polyploidy - types
Ramsey & Schemske 2002
 Polyploids are defined either by mode of origin (MO) or by cytological
criteria (CC)
 MO autopolyploids arise within single populations or between ecotypes of
a single species, whereas allopolyploids are derived from interspecific
hybrids
 Autopolyploids have only homologous chromosomes; allopolyploids have
two or more sets of homeologous chromosomes
 CC allopolyploids are expected to display bivalent pairing, lack of
allosyndesis and disomic inheritance, while CC autopolyploids will exhibit
multivalent configurations, nonpreferential pairing at metaphase, and
multisomic inheritance
Polyploidy - types
Ramsey & Schemske 2002
 The expected does not
always (usually) occur
 80% of recent
allopolyploids show some
amount of multivalents
Polyploidy - types
Therefore, strict allopolyploid
definition would exclude the
classical Primula kewensis
Chromosome pairing at meiotic metaphase in (a) Primula verticillata, (b) P.
verticillata X floribunda, and (c) the hybrid polyploid P. kewensis with some
multivalents
from Stebbins, 1971
Polyploidy - types
Ramsey & Schemske 2002
 The expected does not
always (usually) occur
 80% of recent
allopolyploids show some
amount of multivalents
 All recent autopolyploids
show no evidence of
preferential pairing or disomic
inheritance . .
 but later generation
autopolyploids can show
genic effects that lead to
“diplodized” autopolyploids
Polyploidy - types
Stebbins 1971 - argued for a continuum
I.
II.
Autopolyploids
1.
Strict autopolyploid
AAAA
2.
Interracial autopolyploid
AAAA
Amphidiploids
1.
Segmental allopolyploid
AsAsAtAt
2.
Genomic allopolyploid
AABB
3.
Autoallopolyploid
AAAABB
Polyploidy - how common?
 rare in animals
 rare in fungi (but its an animal)
 common in plants

gymnosperms - rare

non-seed vascular plants - common

flowering plants - common
 actual species counts difficult to get
Polyploidy - how common?
actual species counts difficult to get - why?
 what constitutes a “species”?
 tropical flora (upwards of 1/3 - 1/2 of all species) little
sampled — extrapolation required
 incorrect published chromosome numbers
 Chromosomes in Myosotis checked by Merxmuller & Grau
Myosotis stricta
from Briggs & Walters, 1997
Polyploidy - how common?
Estimates in flowering plants
(& author’s rationale)
 Stebbins (1971)
30-35%
(obvious polyploid series)
 Grant (1971)
47%
( > x = 13 )

43% dicots & 58% monocots
 Goldblatt (1980)
70% (monocots)
 Lewis (1980)
70-80% (dicots)
( n = 11, 10 (9) )
Polyploidy - high numbers
from Grant, 1981
Ophioglossum (adder’s-tongue fern) 2n = 1440 (96 ploid) in O. reticulatum
Polyploidy - high numbers
Sedum suaveolens - 2n = ca. 640
(80 ploid)
dicot
Voanioala gerardii - 2n = ca. 596
(50 ploid)
monocot
Polyploidy - life form correlation
Stebbins, 1971 Chromosomal evolution in higher plants
Polyploidy - latitude correlation
Frequency of polyploids (black %) in
the floras of various territories in the
Northern Hemisphere (from Love and
Love, 1974)
from Briggs & Walters, 1997
Polyploidy - latitude correlation
Spitsbergen
from Grant, 1981
Polyploidy - latitude correlation
Chamerion angustifolium - fireweed (Onagraceae)
Both diploid and tetraploid individuals are found in North America, with diploids generally
occurring at higher altitudes and more northerly latitudes. An overlap zone where both diploids and
tetraploid fireweed co-occur is located at intermediate altitudes in the Canadian Rockies and along
the southern border of the boreal forest. http://www.uoguelph.ca/botany/research/evollab/rockies.htm
Polyploidy - size correlation
Stebbins, 1971 Chromosomal evolution in higher plants
Polyploidy - size correlation
Ramsey & Schemske, 2002
Polyploidy - size correlation
Stebbins 1971, Fig. 6.11
Sequoia sempervirens (2n=66) - relictual
hexaploid; fossils appear to be diploid —
no close relatives. Sequoiadendron
giganteum in another genus is diploid.
Polyploidy - range extension
Stebbins 1971, Fig. 6.5
Map of western North America
and distributions of diploid and
tetraploid Zauschneria (=
Epilobium)
Polyploidy - range extension
C. purpurea n=26
C. tenella n=17
reversed!
C. williamsonii n=9
Limits of distributions of diploids, tetraploids,
and hexaploids in Clarkia sect. Godetia
Stebbins 1971, Fig. 6.10
Polyploidy - apomixis
Sexual and apomictic
species in Sorbus
from Briggs & Walters, 1997
Polyploidy - Systematic Tests
Asplenium - flavonoids
A. platyneuron
A. rhizophyllum
A. montanum
A. X kentuckiense
(trigenomic polyploid)
from Briggs & Walters, 1997
Polyploidy - Systematic Tests
Bommeria hispida - copper fern
Haufler, 1985 - Isozymes
2n=60 to 90 species all show
isozyme loci number typical of
diploids
Polyploidy - Systematic Tests
Equisetum 2n =216
Psilotum 2n =104-416
Polyploidy - Systematic Tests
Tribe Astereae n = 2 to n = 9, with n = 4, 5 very common
 Raven et al. (1960) — all diploid numbers with aneuploid
reduction
 Turner et al. (1961) — n = 9 are allopolyploids from
diploid n = 4 and n = 5
Gottlieb (1971) showed that all have
the same number of isozymes and thus
all diploids in Machaeranthera (3
species with n = 4, 5, 9) and Aster (2
species with n = 5, 9)
Machaeranthera
coloradensis
Polyploidy - Systematic Tests
Epilobium n = 9, 10, 12, 13, 15, 18
 Stebbins (1971 & Raven) — original basic
number is x = 6 or 9, x = 18 is of secondary
polyploid origin
Polyploidy - Systematic Tests
Epilobium n = 9, 10, 12, 13, 15, 18
 Baum, Sytsma, Hoch (1994) — DNA sequence
evidence does not support the Stebbins’ model
most parsimonious
Polyploidy - Systematic Tests
Epilobium n = 9, 10, 12, 13, 15, 18
 Baum, Sytsma, Hoch (1994) — DNA sequence
evidence does not support the Stebbins’ model
but possible
Polyploidy - Systematic Tests
Genomic in situ hybridization (GISH)
or Flourescent in situ hybrization
(FISH)
Tragopogon - goat’s beard
Polyploidy - Systematic Tests
C. arenosa
A. suecica - naturally occurring allopolyploid in Europe
http://comailab.genomecenter.ucdavis.edu/polyploidy.htm
Polyploidy - Systematic Tests
http://comailab.genomecenter.ucdavi
s.edu/polyploidy.htm
Multiple copies of the red and green
genomes are visible in this picture of
tapetum cells from Arabidopsis suecica
allopolyploids
Image Credits
Arabidopsis suecica
http://linnaeus.nrm.se/flora/di/brassica/arabs/arabsue3.jpg
Bommeria hispida
http://botany.cs.tamu.edu/FLORA/swts/pter002.jpg
Cardaminopsis arenosa
http://www.ruhr-uni-bochum.de/boga/html/Cardaminopsis_arenosa_Foto.html
Clarkia purpurea winecup clarkia
http://www.kenbowles.net/SDWildflowers/FamilyIndexes/Onagraceae/OnagraceaeKey.htm
Clarkia williamsonii Fort Miller clarkia
http://www.timetotrack.com/jay/mtns/clarkw.htm
Clarkia tenella
http://www.chilebosque.cl/herb/ctene01.jpg
Colchicum
© Peter v. Sengbusch - b-online@botanik.uni-hamburg.de
Epilobium cana
http://www.coepark.org/wildflowers/red/epilobium-canum.jpg
Epilobium polyploid
http://www.uoguelph.ca/botany/research/evollab/rockies.htm
Machaeranthera coloradensis tansy aster
http://www.conps.org
Myosotis stricta
http://www.atlas-roslin.pl/foto/ji/ji-20040501265.jpg
Image Credits
Nasturtium microphylla
http://www.plant-identification.co.uk/skye/cruciferae/nasturtium-microphyllum.htm
Ophioglossum reticulatum
http://cookislands.bishopmuseum.org/
http://moorea.berkeley.edu/flora/fernphotos/ophioglossum_retic1.jpg
Primula kewensis
http://homepage3.nifty.com/wako3/saibaisousyun/Primulakewensis/Primulakewensis.htm
Primula verticillata (Abyssinian primrose)
http://www.botanic.jp/plants-ha/priver.htm
Sorbus aucuparia
http://www.kuleuven-kortrijk.be/bioweb/
Sorbus torminalis
http://www.saxifraga.de/europa/gesamtartenliste.html
Spitsbergen flora poppy
http://upload.wikimedia.org/wikipedia/commons/thumb/4/49/Poppy3.jpg/300px-Poppy3.jpg
Spitsbergen flora Silene
http://www.digitalnature.org/flora/silene%20furcata%20kl.jpg