Polyploidy, alien species and invasiveness in Polish angiosperms

14 Pages·2014·0.41 MB·English

PlantSystEvol(2014)300:225–238
DOI10.1007/s00606-013-0875-x
ORIGINAL ARTICLE
Polyploidy, alien species and invasiveness in Polish angiosperms
Grzegorz Go´ralski • Andrzej Judasz •
Paulina Gacek • Aleksandra Grabowska-Joachimiak •
Andrzej J. Joachimiak
Received:28February2013/Accepted:8July2013/Publishedonline:27July2013
(cid:2)TheAuthor(s)2013.ThisarticleispublishedwithopenaccessatSpringerlink.com
Abstract Chromosome numbers, mainly for Polish flora, Introduction
were examined in order to investigate whether such fea-
tures as chromosome numbers and polyploid frequencies Polyploidy is usually defined as the occurrence of more
are correlated with a plant’s origin (native vs. alien) and than two genomes in a nucleus. Polyploid organisms
invasiveness. Polyploid frequencies were estimated using (polyploids) are formed as a result of polyploidization,
threemethods:the11and14thresholdsandthe3.5xvalue. which is believed to play a crucial role in plant evolution.
Comparisons of the 2n values were done on different lev- The two main types of this process are: autopolyploidiza-
els: in all angiosperms and in dicots and monocots sepa- tion, in which the multiplied genomes belong to the same
rately. Invasive and non-invasive plants were compared in species; and allopolyploidization, in which an increase in
the entire dataset and in alien species only. Significant the number of genomes is accompanied by hybridization.
differences in both chromosome numbers and polyploid The estimated fraction of polyploids or their descen-
frequencies between alien and native species were dants ranges from 30 to 80 % in about 250,000 species of
observed. In most cases, native plants had more chromo- angiosperms (Bennett 2004). Such a wide range of
somes and were more abundant in polyploids than in alien approximation is the result of the different methods and
species. Also, monocots had higher polyploid frequencies criteriathathavebeenusedinassigningtaxatodiploidsor
than dicots. Comparisons of invasive and non-invasive polyploids. Because polyploidization involves the multi-
plants done for all of the data and only for alien species plication of genomes, the easiest way to detect polyploids
showed that invasive species generally had more chromo- seems to be to set a threshold of a given number of chro-
somes and polyploids were more frequent in them than in mosomes as the level above which a taxon is regarded as
the latter group; however, these differences were not polyploid. Such a method is especially useful when it is
always statistically significant. Possible explanations for usedforlargesetsofdata—theonlycriterionneededisthe
these observations are discussed. chromosome number. Naturally, the result obtained
dependsentirelyonthethresholdvaluethatisapplied.The
Keywords Invasiveness (cid:2) Alien species (cid:2) most well-known estimations are n C 11, proposed by
Chromosomes (cid:2) Polyploidy (cid:2) Evolution (cid:2) Plants Goldblatt (1980) and n C 14, proposed by Grant (1981).
Wood et al. (2009), in their studies on the frequency of
polyploid speciation, proposed a modified threshold
method: species should be regarded as polyploid if the
G.Go´ralski(&)(cid:2)A.Judasz(cid:2)P.Gacek(cid:2)A.J.Joachimiak
somaticchromosomenumberisgreaterthanorequalto3.5
DepartmentofPlantCytologyandEmbryology,Jagiellonian
times the lowest haploid count of the host genus.
University,Grodzka52,31-044Cracow,Poland
e-mail:[email protected] A method based on knowing the x (basal set of chro-
mosomes) of taxa was recently used to estimate the poly-
A.Grabowska-Joachimiak
ploid fraction in Polish angiosperms, which were
CytogeneticsGroup,DepartmentofPlantBreeding
comparabletothethresholdsproposedbyGoldblatt,Grant
andSeedScience,UniversityofAgricultureinCracow,
Łobzowska24,31-140Cracow,Poland and Wood (Gacek et al. 2011). While the scores obtained
123
226 G.Go´ralskietal.
using the threshold methods gave polyploid frequencies at reachingthephaseofuncontrolledspreadingandbecoming
levels of 64.64, 50.89 and 42.89 %, respectively, calcula- aproblem(Richardson andPysˇek 2006;Williamson2006;
tions that were based on the generic basic chromosome Pysˇek et al. 2008). Therefore, the preconditions for a spe-
numbers showed 49.45 % of polyploids and 4.11 % of ciestobedefinedasinvasivemustincludethestageoftheir
diploid/polyploid cytotypes. naturalization. Understanding the features that influence a
More in-depth studies, including molecular analysis, plant’sabilitytobenaturalizedinanewecosystemmaybe
have revealed that some species, which due to their low crucialforunderstandingthephenomenonofinvasiveness.
chromosome number are regarded as diploids, have a Features that are regarded as evolutionarily beneficial may
polyploid origin. One of the most well-known examples is be responsible for a plant’s ability to colonize new areas
maize. However, its chromosome number (n = 10) is and eventually become invasive; thus, a question that
below even Goldblatt’s threshold, its molecular data has naturally arose was whether polyploidization or just an
proveditstetraploidorigin(GautandDoebley1997).Even increase in genome size supports such capabilities. This
thegenomeofArabidopsisthaliana,whichisknownforits subject is not only interesting but also significant practi-
small genome (*157 Mb) (Bennett et al. 2003) and cally. Invasions of alien species are currently perceived as
chromosome number (2n = 10), might have been dupli- one of the most serious threats to global biodiversity
cated two to three times in the past (Vision et al. 2000; (Tokarska-Guzik et al. 2011). Although some studies have
Bowers et al. 2003). A recent analysis of genomic studies focused on searching for a correlation between these phe-
revealed that almost all angiosperms have polyploid nomena in selected taxa, the subject has not yet been well
ancestors, and therefore, according to some authors, the explored (Hull-Sanders et al. 2009).
question‘‘Whatproportionofangiospermsarepolyploid?’’ The influence of polyploidy on a single species, Cen-
should be replaced with ‘‘How many episodes of poly- taurea maculosa (syn. C. stoebe), was studied by Treier
ploidycharacterizeanygivenlineage?’’(Soltisetal.2005, et al. (2009), who analyzed the ploidy level in 93 native
2009). and48invasivepopulations.InEurope,whereitoriginates,
The discrepancies between the molecular data and the populations were dominated by diploids, whereas in North
‘‘conventional’’ methods mentioned above are mainly America, where it was introduced in the late nineteenth
caused by the changes in genomes that occurred after the century and became a highly invasive plant, tetraploids
polyploidization, including the rearrangements and loss of were much more frequent and diploids were found only in
chromosomes that result in comparatively low chromo- mixed populations. These results were later partially con-
some numbers. In light of these results, estimations of testedbyauthorswhodidnotfinddiploidsinthisareaand
polyploid frequencies based on conventional methods suggested that the polyploidy of N American populations
should be treated as frequencies of ‘‘recently’’ formed may be caused by their origin rather than as the result of
polyploids.However,althoughtheymaynotrevealthereal selection (Mra´z et al. 2012; Thebault et al. 2011).
number of taxa that ever had a polyploidization event in Ambiguous results were also obtained by Hull-Sanders
their evolutionary history, they may be useful in other et al. (2009), who investigated the occurrence of diploid,
types of studies, including research on the influence of tetraploidandhexaploidcytotypesofSolidagogiganteain
polyploidization on given features such as invasiveness. its native range in the USA and its introduced range in
Regardless of the method used in estimating polyploid Europe.Tetraploidswerethemostcommoninbothranges,
frequency,thereisnodoubtthatpolyploidyplaysacrucial but were more dominant in Europe. Hexaploids, however,
role in the evolution of angiosperms, and therefore, many were the most geographically restricted and were found in
studies are focused on this subject. One of the most inter- only two populations in the United States.
esting questions about polyploidy is whether the multipli- Lowry and Lester (2006) studied 60 taxa in the genus
cation of the genomes offers any evolutionary advantages. Clarkia in Western North America and showed that poly-
Authors usually mention such factors as the masking of ploid species have a significantly larger range size than
deleterious mutations, a reduction in the ‘‘inbreeding diploids. Simultaneous studies on the flora of Singapore,
depression effect’’, fixed heterozygosity, heterosis, addi- which is regarded as a global hotspot for invasive species,
tivity in gene expression, nuclear–cytoplasm interactions provedthatallofthehighlyinvasiveplantsinvestigatedon
and an enhanced phenotype, e.g., larger cells and organs this area were polyploids (Pandit et al. 2006). Pandit et al.
(Ronfort 1999; Otto and Whitton 2000; Soltis and Soltis (2011) not only compared invasive with non-invasive
2000; Levin 2002; Wang et al. 2006; Otto 2007; te Beest plants, but also included endangered species in their stud-
et al. 2012). ies. They collected worldwide data on the chromosome
Invasive plants are generally regarded as alien species numbers for 640 endangered species and their 9,005
that,afterpassingaseriesoftransitionalstages,escapeinto congeners and for 81 invasive species and their 2,356
the wild and form a stable population there, eventually congeners. Data analysis showed that while endangered
123
PolyploidyinPolishangiosperms 227
plants are usually diploids, invasive plants have more (Gacek et al. 2011) proved that polyploidy is more com-
chromosomes and they are more likely to be polyploids. monamongindigenousplantsinPolishflora.Inthispaper,
Recently,theroleofpolyploidyinplantinvasionswasalso we present more detailed results because the comparisons
reviewed by te Beest et al. (2012). were done on different levels: in all angiosperms and in
An interesting approach to the subject was presented dicots and monocots separately. In addition, invasive and
recently by Kubesˇova´ et al. (2010) who compared the non-invasive plants were compared in the entire dataset
genomesizeofnaturalizedandnativespeciesintheCzech and in alien species only. The results obtained for Polish
Republic. The authors also compared the genomes of plants may be compared to those obtained for the nuclear
invasive species with non-invasive but alien species. DNA content in the flora of our neighbor, the Czech
Genome sizes were determined using the flow cytometry Republic (Kubesˇova´ et al. 2010). The problems that were
technique, and therefore DNA amounts, not chromosome considered in both studies are similar, but different meth-
numbers, were analyzed. These studies resulted in the ods were applied and different features of genomes were
conclusion that naturalized species generally had smaller compared. So our approach may shed a different light on
genomes than their native congeners. These observations the problem of the influence of genome parameters on the
correspond with the idea that small genomes favor inva- naturalization and invasiveness of plants.
sivenessbecausethismaycorrespondwithsuchfeaturesas
light seeds (which facilitate a species spreading), a short
minimum generation time and a relatively high growth
Materials and methods
rate of seedlings, etc. (Rejma´nek and Richardson 1996;
Grotkopp et al. 2002; Rejma´nek et al. 2005).
Data sources
As was described above, there are different approaches
forinvestigatingtheconnectionsbetweenploidylevelsand
Chromosome numbers were obtained mainly from the
invasiveness.Somestudiesarefocused onrelatedinvasive
‘‘Chromosome Number Database’’ (Go´ralski et al. 2009),
and non-invasive species, and others on the different spe-
which contains all of the known chromosome numbers for
cies represented in a given area. In addition, a global
Polish angiosperms. In cases where the chromosome
approachispossibleaswaspresentedinthepaperofPandit
number was not known from Poland, it was acquired from
et al. (2011), who collected and analyzed data for thou-
other sources: Index to Plant Chromosome Numbers
sands of taxa from around the world.
(GoldblattandJohnson1979),Karyologicaldatabaseofthe
Our study concerns the invasive and non-invasive taxa
ferns and flowering plants of Slovakia (Marhold et al.
inPolishflora.PolandisaCentralEuropeancountrywitha
2012), Chromosome numbers for the Italian flora (Bedini
temperateclimate.Itsterritoryismainlycovered byplains
et al. 2010), the database of the Botanical Society of the
(*90 %) without any natural barriers that could hinder
British Isles (BSBI), BIOLFLOR—Eine Datenbank zu bi-
plant migrations on the east–west axis. During the Pleis-
ologisch-o¨kologischen Merkmalen der Gefa¨ßpflanzen in
tocene, almost the entire area of the country was covered
Deutschland (Klotz et al. 2002) and Mo`dul Flora i Vege-
by a glacier and therefore Polish flora is relatively young
tacio´.BancdeDadesdeBiodiversitatdeCatalunya(Simon
and was formed mainly in the Holocene (Szafer and Zar-
and Blanche´ 2012).
zycki 1977). Studies done by Chytry´ et al. (2009) showed
For all of the comparisons, angiosperm families that
that West and Central European lowland plains are regar-
belonged to monocots and core eudicots (later named
ded as highly exposed to invasions. Moreover, this tradi-
‘‘dicots’’) with alien and native species were chosen. For
tionally agricultural country has undergone intensive
comparisons of invasive and non-invasive species, only
industrialization in recent decades, which was accompa-
families with both invasive and non-invasive plants were
nied by the degradation of many natural habitats. Urban,
used.Wealsorejectedonecytotypethatachievedover100
industrial and degraded areas are also known to be sus-
chromosomes from the calculations.
ceptible to invasions (Chytry´ et al. 2009; Tokarska-Guzik
Only cytotypes from Poland were used for the non-
etal.2011).ThesefeaturesmakePolishfloraaninteresting
invasivespecies, while analgorithmwas used for invasive
and important area for studies on alien plant settlements
species:
and invasions, and it has therefore become the subject of
many studies and data collections (INC PAS 2009; 1. If cytotypes from Poland were known only these were
Tokarska-Guzik et al. 2012). used.
The main subject of our research was to investigate 2. If cytotypes from Poland were not known, cytotypes
whether such features as chromosome numbers and poly- from the closest geographical origin were used. The
ploid frequencies are correlated with a plant’s origin closestoriginwaschosenfromplacesinthefollowing
(native vs. alien) and invasiveness. Our previous studies order: neighbor countries (Germany, the Czech
123
228 G.Go´ralskietal.
Republic, Slovakia, Ukraine, Byelorussia, Russia and Table1 Alienspecies
the countries of the former Soviet Union), other
Species Invasiveness 2n
European countries and the rest of the world.
Acerginnala - 26
Also, for some additional comparisons, only cytotypes
Acernegundo ? 26
from Poland were used (indicated in the text).
Acersaccharinum - 52
Knownxvaluesforspecieswereobtainedmainlyfrom:
Achilleacrithmifoliaet - 36
Darlington and Janaki Ammal (1945), Darlington and
Acoruscalamus ? 36
Wylie(1955),Holubetal.(1971),DobesandVitek(2000)
Aesculushippocastanum - 40
and Klotz et al. (2002).
Agropyroncristatum - 14
Ifxwasnotknownforagivenspecies,itwascalculated
Agrostemmagithago - 48
using an algorithm:
Amaranthusbouchonii - 32
1. If no x value is known for genera: Amaranthuschlorostachys - 32
Amaranthuslividus - 34
a. Ifthereisaseriesof2nvaluesthataremultiplesof
Amaranthusretroflexus - 34
an integer, this number was used as x.
b. In other cases, the species was not used in Ambrosiaartemisiifolia ? 36
calculations. Anagallisarvensisformaarvensis - 40
Anagallisfoemina - 40
2. If many x numbers were known for a genera and
Anethumgraveolens - 22
among them was a number that is a divisor for the
Anthemiscotula - 18
2n of a given species, this x was used.
Anthoxanthumaristatum - 10
3. If there were 2n values that did not have divisors
Aperaspica-venti - 14
between the known x0s then:
Aphanesarvensis - 48
a. Ifonlyonexwasknownforagenus,thisonewas Aphanesmicrocarpa - 16
used. Armoraciarusticana - 32
b. Ifthereweremanyxvalues,theclosestvaluewas Artemisiaabrotanum - 18,36
used with the exception of those x values that Artemisiaannua - 18
wouldhavemeantthatthe2nwashaploidnumber. Artemisiaaustriaca - 16
c. If the above did not provide a clear answer, the Artemisiadracunculus - 90
highest x for a genus was used. Asclepiascornuti - 22
Asterlanceolatus ? 64
The Alien Species in Poland (INC PAS 2009) database
Asternovae-angliae ? 10
was used as the source of invasive and alien plants in
Asternovi-belgii ? 54
Poland. A species was regarded as invasive when it was
Astertradescantii ? 16
described as invasive or post-invasive. All alien species
Atriplexhortensis - 18
usedinthestudyalongwiththestatusoftheirinvasiveness
Atriplexnitens - 18
are listed in Table 1.
Atriplextatarica - 18
Avenafatua - 42
Comparisons and groups tested
Avenasativa - 42
Ballotanigra - 22,20
Two types of comparisons between groups were applied:
Barbareaintermedia - 16
chromosome numbers and polyploid frequency. Three
Bidensfrondosa ? 48
methods were used for ploidy classification. Two were the
Boragoofficinalis - 16
thresholdmethodswiththevaluesn C 11(Goldblatt1980)
Brassicaelongata - 22
and n C 14 (Grant 1981). The third was the modified
Bromusarvensis - 14
method described by Wood et al. (2009) and referred to
Bromuscarinatuset - 56
laterasthe‘‘3.5xmethod’’.Inthiscase,3.5xvalueswere
Bromussecalinus - 28
counted for cytotypes using x values ordered to cytotypes
Bromussterilis - 14
as described above and those for which the 2n achieved a
Bromustectorum - 14
3.5 of x value or more were counted as polyploids.
Bromuswilldenowii - 42
Tests were performedonall angiospermsand twoofits
Buniasorientalis ? 14
classes:monocotsanddicots.Theseclasseswerecompared
123
PolyploidyinPolishangiosperms 229
Table1 continued Table1 continued
Species Invasiveness 2n Species Invasiveness 2n
Calendulaofficinalis - 32 Euphorbiapeplus - 16
Camelinarumelica - 12 Fagopyrumesculentum - 16
Camelinasativa - 40 Fagopyrumtataricum - 16
Cannabissativa - 20 Fallopiaconvolvulus - 40
Capsellabursa-pastoris - 32 Fraxinuspennsylvanica - 46
Caraganaarborescens - 16 Galinsogaparviflora - 16
Carduusacanthoides - 22 Galinsogaquadriradiata - 32
Carduusnutans - 16 Geraniumdissectum - 22
Centaureacyanus - 24 Geraniumdivaricatum - 28
Chamomillarecutita - 18 Geraniummolle - 26
Chamomillasuaveolens - 18 Geraniumpusillum - 26
Chenopodiumaristatum - 18 Geraniumpyrenaicum - 26,28
Chenopodiumbonus-henricus - 36 Geraniumsibiricum - 28
Chenopodiumficifolium - 18 Glauciumflavum - 12
Chenopodiumhybridum - 18 Gleditsiatriacanthos - 28
Chenopodiummurale - 18 Helianthusannuus - 34
Chenopodiumsuecicum - 18 Helianthusdecapetalus - 34
Chrysanthemumsegetum - 18 Helianthustuberosus ? 102
Cichoriumintybus - 18 Helianthusxlaetiflorus - 102
Clematisvitalba ? 16 Heracleummantegazzianum ? 22
Consolidaregalis - 16 Heracleumsosnovskii ? 22
Conyzacanadensis - 18 Herniariahirsuta - 36
Corispermumhyssopifolium - 18 Hesperismatronalis - 24
Corispermumnitidum - 18 Hordeummurinum - 28
Cornusmas - 18 Humulusscandens - 16,17
Cornussericea ? 22 Hyoscyamusniger - 34
Crepisaurea ? 10 Impatienscapensis ? 20
Crocusvernus - 16 Impatiensparviflora ? 26
Cymbalariamuralis - 14 Impatiensroylei ? 18
Daturastramonium - 24 Inulahelenium - 20
Descurainiasophia - 28 Ivaxanthifolia - 36
Digitariasanguinalis - 36 Juncustenuis - 40
Diplotaxismuralis - 42 Kochiascoparia - 18
Echinaceapurpurea - 22 Lactucaserriola - 18
Echinochloacrus-galli ? 54 Lamiumalbum - 18
Echinopscommutatus - 30 Lamiumamplexicaule - 18
Echinopssphaerocephalus ? 30,32 Lamiumpurpureum - 18
Elaeagnusangustifolia - 28 Lathyrustuberosus - 14
Elaeagnuscommutata - 28 Leonuruscardiaca - 18
Elodeacanadensis ? 48 Lepidiumcampestre - 16
Elodeanuttallii - 48 Lepidiumdensiflorum - 32
Elsholtziaciliata - 16 Lepidiumlatifolium - 24
Epilobiumadenocaulon - 36 Lepidiumperfoliatum - 16
Eragrostispilosa ? 20 Lepidiumruderale - 32
Erigeronannuus - 27 Lepidiumsativum - 24
Erucavesicariasubsp.sativa - 22 Lepidiumvirginicum - 32
Euphorbiaexigua - 16,24 Levisticumofficinale - 22
Euphorbiahelioscopia - 42 Linumaustriacum - 18
123
230 G.Go´ralskietal.
Table1 continued Table1 continued
Species Invasiveness 2n Species Invasiveness 2n
Linumperenne - 18 Oenotheraturoviensis - 14
Linumusitatissimum - 30 Oenotheravratislaviensis - 14
Lithospermumarvense - 28 Oenotherawienii - 14
Loliummultiflorum ? 14 Onobrychisviciifolia ? 28
Loliumremotum - 14 Onopordumacanthium - 34
Lupinusangustifolius - 40 Ornithogalumnutans - 42
Lupinusluteus - 52 Oxalisstricta - 24
Lupinuspolyphyllus - 48 Oxycoccusmacrocarpus - 24
Lychniscoronaria - 24 Padusserotina ? 32
Lyciumhalimifolium - 48,24 Panicummiliaceum - 36
Malopetrifida - 44 Parietariaofficinalis - 14
Malvaalcea - 84 Petroselinumcrispum - 22
Malvacrispa - 120,112 Phalariscanariensis - 12
Malvamoschata - 42 Phleumrhaeticum - 14
Malvaneglecta - 42 Physalisalkekengi - 24
Malvapusilla - 42 Physocarpusopulifolius - 18
Malvasilvestris - 42 Pimpinellaanisum - 20
Malvaverticillata - 84 Polygonumorientale - 22
Marrubiumvulgare - 34 Potentillaintermedia - 56
Matricariamaritima - 18,36 Quercuscerris ? 24
Medicagosativa ? 32 Quercusrubra - 24
Melandriumnoctiflorum - 24 Raphanusraphanistrum - 18
Mentharotundifolia - 54 Raphanussativus - 18
Menthaxgentilis(=spicataxarvensis) - 60 Reynoutriajaponica ? 88
Mercurialisannua - 16 Reynoutriasachalinensis ? 44,66,88
Mimulusguttatus ? 28 Reynoutriaxbohemica ? 66,44,88
Mimulusmoschatus ? 32 Robiniapseudacacia ? 20
Misopatesorontium - 16 Rosablanda - 14
Myosotisarvensis - 52 Rosaglauca - 28
Myrrhisodorata ? 22 Rosapimpinellifolia - 28
Nepetacataria - 36 Rosarugosa - 14
Nigellaarvensis - 12 Rubusodoratus - 14
Oenotheraacutifolia - 14 Rubusxanthocarpus - 14
Oenotheraalbipercurva - 14 Rudbeckiahirta - 38
Oenotherafallax - 14 Rudbeckialaciniata - 76,38
Oenotheraglazioviana - 14 Rumexconfertus - 60
Oenotherahoelscheri - 14 Scleranthusannuus - 44
Oenotheraissleri - 14 Scorzonerahispanica - 14
Oenotherajueterborgensis - 14 Scrophulariavernalis - 40
Oenotheraparadoxa - 14 Senecioinaequidens ? 40
Oenotheraparviflora - 14 Seneciovulgaris - 40
Oenotherapseudochicaginensis - 14 Setariaglauca - 36
Oenotherapycnocarpa - 14 Setariaitalica - 18
Oenotherarenneri - 14 Sherardiaarvensis - 22
Oenotherasalicifolia - 14 Silenedichotoma - 24
Oenotherasilesiaca - 14 Silybummarianum - 34
Oenotherasuaveolens - 14 Sinapisalba - 24
Oenotherasyrticola - 14 Sinapisarvensis - 18
123
PolyploidyinPolishangiosperms 231
Table1 continued thosecontainingfewerthantencytotypesandtheresultsof
v2 test with the Yates correction for small samples
Species Invasiveness 2n
(chisq.test from stats library). Confidence intervals were
Sisymbriumloeselii - 14 calculated using the test of equal or given proportions
Sisymbriumofficinale - 14 (prop.test from stats library).
Solanumnigrum - 72
Solidagocanadensis ? 18
Solidagogigantea ? 36 Results
Sonchusasper - 18
Sonchusoleraceus - 36 Chromosome numbers
Spergulaarvensis - 18
Symphoricarposalbus ? 54 The results of the most important statistical tests are pre-
Symphyotrichumciliatum - 14 sented in Tables 2 and 3. Table 2 contains the results for
Syringajosikaea - 44 the chromosome numbers of invasive and non-invasive
taxa in angiosperms, dicots and monocots as well as
Syringavulgaris - 44
comparisons of native and alien taxa. The results of the
Thlaspiarvense - 14
comparisonsofthediploidandpolyploidfractionsinthese
Trifoliumpatens - 14
groups are presented in Table 3.
Trifoliumresupinatum - 16
In total, 1,428 cytotypes were investigated. Chromo-
Trigonellacoerulea - 16
some numbers ranged from 6 to 96. The most frequent
Urticacannabina - 52
chromosomenumber(mode)was28.Chromosomenumber
Urticaurens - 24
frequencies are displayed in Fig. 1.
Veronicaarvensis - 16
Forty-two of the cytotypes investigated belonged to
Veronicafiliformis - 14
invasive species (4.3 %) and 927 to non-invasive species
Veronicapersica - 28
(95.7 %). The minimum, mean and median values of the
Veronicapolita - 14
2n were higher for invasive angiosperms than for non-
Veronicatriphyllos - 14
invasive ones (Table 2). The mean 2n value for the first
Viciadasycarpa - 14
groupwasmorethansixchromosomeshigher,whereasthe
Viciagrandiflora - 14
mediandifferencewassmaller(4).TheMann–Whitneytest
Viciahirsuta - 14
indicated thatthedifference betweengroupsisstatistically
Viciasativa - 12
significant(p\0.05).Generally,alloftheparametersthat
Viciatetrasperma - 14
were checked were the same or almost the same for non-
Viciavillosa - 14
invasiveangiospermsandforallofthenativeangiosperms
Violaarvensis - 34
that were tested. Chromosome number distributions for
Vitisvinifera - 38
both groups are shown in Fig. 2b.
Xanthiumalbinum ? 36
Most of the plants studied were dicots (81.7 %).
Xanthiumspinosum - 36
Comparisons of monocots and dicots showed that the
Xanthiumstrumarium - 36 mode and median were equal and was the same for both
groups (28). Monocots had a higher mean (32.5 vs. 30.8)
but the statistical test did not prove that the difference is
as being non-invasive to invasive and native to alien spe- statistically significant (p = 0.39). The span of 2n num-
cies in angiosperms and in both classes. bers was wider indicots (6–96) than inmonocots(10–94).
The parameters for Polish-only cytotypes were nearly the
Statistics tools and procedures same.
The almost twofold difference in the frequency of
All of the analyses and graphs were done in the R envi- invasive plants in dicots (4.8 %) and in monocots (2.6 %)
ronment for statistical computing (R Development Core was found not to be statistically significant (p = 0.18).
Team 2012). For testing differences between chromosome Invasive plants had a higher mean chromosome number
numbers in groups, the non-parametric Mann–Whitney thannon-invasiveonesinthecaseofdicots(36.6vs.29.0)
U (Wilcoxon) test was used (wilcox.test function from the andmonocots;however,inthelatteritwaslesssignificant
stats library). Diploid and polyploid frequencies and fre- (34.4 vs. 33.4). Higher medians were also noted for inva-
quencies of invasive plants in the groups studied were siveplantsthanfornon-invasiveonesinbothdicots(32vs.
compared using the Pearson’s v2 test for small samples, 28) and monocots (36 vs. 28). The Mann–Whitney test
123
232 G.Go´ralskietal.
Table2 Statisticalcomparisonofthegroupsstudied
Cytotypes Numberofcytotypes Chromosomenumbers(2n) Mann–Whitneytest(p)
Min. Max. Mean(SD) Mode(number) Median
Angiosperms 1,428 6 96 31.1(16.5) 28(167) 28 –
Angiospermsnon-invasive 927 6 96 29.9(15.6) 28(137) 28 \0.05
Angiospermsinvasive 42 10 88 36.4(20.7) 22,32,36(4) 32
Angiospermsnative 1,020 6 96 31.9(16.6) 28(139) 28 \0.05
Angiospermsalien 275 10 90 27.9(15.6) 14(48) 24
Angiospermsaliennon-invasive 128 10 90 25.7(13.5) 14(26) 22 \0.05
Angiospermsalieninvasive 42 10 88 36.4(20.7) 22,32,36(4) 32
Dicots 1,166 6 96 30.8(16.1) 28(113) 28 0.39
Monocots 262 10 94 32.5(17.8) 28(54) 28
Dicotsnon-invasive 738 6 96 29,0(14.5) 28(89) 28 \0.05
Dicotsinvasive 37 10 88 36.6(21.3) 32(4) 32
Dicotsnative 814 6 96 31.5(16.1) 28(95) 28 \0.05
Dicotsalien 247 10 90 27.8(15.7) 14(40) 22
Dicotsaliennon-invasive 108 12 90 25.5(13.3) 14(19) 22 \0.05
Dicotsalieninvasive 37 10 88 36.6(21.3) 22,32(4) 32
Monocotsnon-invasive 189 10 94 33.4(19.0) 28(48) 28 0.74
Monocotsinvasive 5 14 54 34.4(17.3) – 36
Monocotsnative 206 10 94 33.2(18.6) 28(44) 28 0.29
Monocotsalien 28 10 56 28.6(14.8) 14(8) 28
Monocotsaliennon-invasive 10 10 18 13.8(2.0) 14 7 0.05
Monocotsalieninvasive 3 14 36 23(11.4) – 20
proved that these differences were statistically significant Mann–Whitney result, the difference was statistically sig-
onlyfordicots(p\0.05).Themostfrequentchromosome nificant (p\0.05). Similar differences were observed in
number in dicots was higher in invasive plants (32 vs. 28) the group of alien dicots (p\0.05). The group of alien
(Fig. 2d). The medians for invasive monocots are not monocots,especiallyinvasiveplants,wastoosmalltodraw
shown because all five cytotypes had different 2n values. any reliable statistical conclusions.
Among the 1,295 cytotypes, 78.8 % belonged to native
speciesand21.2 %toalienspecies.Statisticalcomparisons Polyploid frequencies
of the 2n values showed that plants from the latter group
have a lower mean (27.9 vs. 31.9), mode (14 vs. 28) and Polyploid frequencies were examined in the same groups
median(22vs24)(Table 2;Fig. 2a).Thedifferenceinthe of species as above. In order to estimate the number of
chromosome numbers between these groups was signifi- polyploids, two threshold methods (n C 11 and n C 14)
cant (p\0.05). Similar tendencies were observed in and the 3.5 x method were used. The results of these
dicots, where the parameters mentioned above had the comparisons are shown in Table 3; Figs. 3, 4, 5.
same or almost the same values, except for the median for The highest polyploid frequencies in almost all of the
aliendicots,whichwastwochromosomeslower(p\0.05) groups tested were generally noted for the n C 11 thresh-
(Table 2; Fig. 2c). The results obtained for monocots dis- old, rather than for the n C 14 threshold and the lowest
played similar tendencies. The mean (28.6 vs. 33.2) and were noted for the 3.5 x method. The exceptions are some
mode(14vs.28)werelowerinalienspeciesthaninnative groupsofmonocotsthathadequalresultsforsomeorallof
ones, but the medians were the same (28) and the differ- the methods. When all of the alien monocots were exam-
ence was not statistically significant (p = 0.29) (Table 2). ined using all three methods, the proportions between
Chromosomenumbersinthegroupofalienspecieswere diploids and polyploids were the same (44.4–55.6 %); in
compared between invasive and non-invasive plants. In the within-group (alien non-invasive and invasive mono-
alien angiosperms, invasive species had a higher mean cots), the probes were too small to draw any reliable sta-
(36.4 vs. 25.7), modes (22, 32 and 36 vs. 14) and median tistical conclusions and therefore they were omitted from
(32 vs. 22) than non-invasive ones and according to the later considerations.
123
PolyploidyinPolishangiosperms 233
Table3 Ploidyinthegroupsstudied
3.5xmethod Threshold11 Threshold14
Diploids Polyploids v2test Diploids Polyploids v2test Diploids Polyploids v2test
(%) (%) (p) (%) (%) (p) (%) (%) (p)
Angiosperms 705(49.7) 714(50.3) – 453(31.7) 975(68.3) – 652(45.7) 776(54.3) –
Angiospermsnon-invasive 466(50.6) 455(49.4) 0.94 316(34.1) 611(65.9) 0.17 431(46.5) 496(53.5) 0.44
Angiospermsinvasive 21(50.0) 21(50.0) 10(23.8) 32(76.2) 17(40.5) 25(59.5)
Angiospermsnative 473(46.4) 547(53.6) \0.05 296(29.0) 724(71.0) \0.05 438(42.9) 582(57.1) \0.05
Angiospermsalien 176(64.0) 99(36.0) 121(44.0) 154(56.0) 161(58.5) 114(41.5)
Angiospermsaliennon- 85(66.4) 43(33.6) 0.09 63(49.2) 65(50.8) \0.05 79(61.7) 49(38.3) \0.05
invasive
Angiospermsalien 21(50.0) 21(50.0) 10(23.8) 32(76.2) 17(40.5) 25(59.5)
invasive
Dicots 604(52.2) 554(47.8) \0.05 267(34.5) 508(65.5) 0.28 378(48.8) 397(51.2) \0.05
Monocots 101(38.7) 160(61.3) 59(40.4) 135(69.6) 70(36.1) 124(63.9)
Dicotsnon-invasive 399(54.4) 334(45.6) 0.49 259(35.1) 479(64.9) 0.13* 363(47.6) 375(52.4) 0.30
Dicotsinvasive 18(48.6) 19(51.4) 8(21.6) 29(78.4) 15(40.5) 22(59.5)
Dicotsnative 393(48.3) 421(51.7) \0.05 234(28.7) 580(71.3) \0.05 358(44.0) 456(56.0) \0.05
Dicotsalien 163(66.0) 84(34.0) 108(43.7) 139(56.3) 148(59.9) 99(40.1)
Dicotsaliennon-invasive 75(69.4) 33(30.6) \0.05 53(49.1) 55(50.9) \0.05* 69(63.9) 39(36.1) \0.05
Dicotsalieninvasive 18(48.6) 19(51.4) 8(21.6) 29(78.4) 15(40.5) 22(59.5)
Monocotsnon-invasive 67(37.2) 113(62.8) 0.57* 57(30.2) 132(69.8) 1.00* 68(36.0) 121(64.0) 1.00*
Monocotsinvasive 3(60.0) 2(40.0) 2(40.0) 3(60.0) 2(40.0) 3(60.0)
Monocotsnative 80(38.8) 126(61.2) 0.44 62(30.1) 144(69.9) 0.08 80(38.8) 126(61.2) 0.58
Monocotsalien 13(46.4) 15(53.6) 13(46.4) 15(53.6) 13(46.4) 15(53.6)
Monocotsaliennon- 10(100) 0(0) – 10(100) 0(0) 0.51* 10(100) 0(0) 0.35*
invasive
Monocotsalieninvasive 3(100) 0(0) 2(66.7) 1(33.3) 2(66.7) 1(33.3)
*TestwithYatescorrection
12
11
10
%] 9
y [ 8
c
n
e 7
u
eq 6
e fr 5
p
oty 4
Cyt 3
2
1
0
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100
Chromosome numbers [2n]
Fig.1 Distributionofchromosomenumbersinangiosperms.Verticallinesindicatepolyploidythresholdsforthe2nvalues:n=11(dottedline)
andn=14(dashedline)
123
234 G.Go´ralskietal.
a
b
100 angiosperms alien angiosperms native 100 angiosperms invasive angiosperms non-invasive
95 95
90 90
85 85
2n] 80 2n] 80
ers [ 7705 ers [ 7705
mb 65 mb 65
u 60 u 60
me n 5505 me n 5505
o 45 o 45
os 40 os 40
om 35 om 35
hr 30 hr 30
C 25 C 25
20 20
15 15
10 10
5 5
0 0
20 15 10 5 0 5 10 15 20 20 15 10 5 0 5 10 15 20
Cytotype frequency [%] Cytotype frequency [%]
c d
100 dicots alien dicots native 100 dicots invasive dicots non-invasive
95 95
90 90
85 85
n] 80 n] 80
2 2
s [ 75 s [ 75
er 70 er 70
b 65 b 65
m m
u 60 u 60
me n 5505 me n 5505
o 45 o 45
s s
o 40 o 40
m m
o 35 o 35
hr 30 hr 30
C 25 C 25
20 20
15 15
10 10
5 5
0 0
20 15 10 5 0 5 10 15 20 20 15 10 5 0 5 10 15 20
Cytotype frequency [%] Cytotype frequency [%]
Fig.2 Frequenciesofcytotypesinsomeofthegroupsstudied.Pairs non-invasive dicots. Horizontal lines indicate polyploidy thresholds
ofdatasetscompared:aalienandnativeangiosperms,binvasiveand forthe2nvalues:n=11(dottedline)andn=14(dashedline)
non-invasive angiosperms, c alien and native dicots, d invasive and
Two classes of angiosperms differ in the abundance of Discussion
polyploids. Monocots have about 1.5–13.9 % more poly-
ploid cytotypes than dicots, but the difference is statisti- Because a plant invasion is preceded by the process of
cally insignificant for the n C 11 threshold (p = 0.28). naturalization (Richardson and Pysˇek 2006; Williamson
Comparisons of polyploid frequencies between non-inva- 2006; Pysˇek et al. 2008), the features that enable plants to
siveandinvasivespeciesshowedthatinmostcases(except survive and establish a stable population in a new area are
formostofthemethodsformonocots),theywerehigherin important for their ability toinvade and prosper. One such
the cytotypes of invasive plants and that these differences feature is genome size, although there are two opposite
were statistically significant (p\0.05) for alien angio- processes that can be regarded as promoting plant natu-
sperms (except for the 3.5 x method) and alien dicots. ralization and invasiveness. The first is the process of
When native and alien taxa were compared, the v2 test polyploidization, which may support a plant through ben-
proved that the differences were statistically significant efits that have been described by many authors and that
(p\0.05), with the exception of the comparisons of were briefly summarized in the introduction of this paper.
monocots. In the rest of the groups tested (angiosperms, Polyploidization, which is the process of genome multi-
dicots)andforallthreemethodsthatwereusedtoestimate plication, results in genomes with a higher DNA content
the frequency of polyploids, alien plants generally had a and higher chromosome numbers. The second process is
lower fraction of polyploids than native ones. the loss of genetic material, which may also be beneficial,
123