This article was downloaded by: [CSK Himachal Pradesh Krishi Vishvavidyalaya] On: 05 March 2014, At: 20:18 Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK Caryologia: International Journal of Cytology, Cytosystematics and Cytogenetics Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/tcar20 An overview of chromosome and basic numbers diversity in cytologically investigated polypetalous genera from the Western Himalayas (India) Savita Rani a , Syed Mudassir Jeelani a , Sanjeev Kumar a , Santosh Kumari a & Raghbir Chand Gupta a a Department of Botany, Punjabi University Patiala, Punjab, 147 002, India Published online: 04 Mar 2014. To cite this article: Savita Rani, Syed Mudassir Jeelani, Sanjeev Kumar, Santosh Kumari & Raghbir Chand Gupta (2014): An overview of chromosome and basic numbers diversity in cytologically investigated polypetalous genera from the Western Himalayas (India), Caryologia: International Journal of Cytology, Cytosystematics and Cytogenetics, DOI: 10.1080/00087114.2013.856088 To link to this article: http://dx.doi.org/10.1080/00087114.2013.856088 PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http:// www.tandfonline.com/page/terms-and-conditions
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This article was downloaded by: [CSK Himachal Pradesh Krishi Vishvavidyalaya]On: 05 March 2014, At: 20:18Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954 Registered office: MortimerHouse, 37-41 Mortimer Street, London W1T 3JH, UK
Caryologia: International Journal of Cytology,Cytosystematics and CytogeneticsPublication details, including instructions for authors and subscription information:http://www.tandfonline.com/loi/tcar20
An overview of chromosome and basic numbersdiversity in cytologically investigated polypetalousgenera from the Western Himalayas (India)Savita Rania, Syed Mudassir Jeelania, Sanjeev Kumara, Santosh Kumaria & Raghbir ChandGuptaa
a Department of Botany, Punjabi University Patiala, Punjab, 147 002, IndiaPublished online: 04 Mar 2014.
To cite this article: Savita Rani, Syed Mudassir Jeelani, Sanjeev Kumar, Santosh Kumari & Raghbir Chand Gupta (2014):An overview of chromosome and basic numbers diversity in cytologically investigated polypetalous genera from theWestern Himalayas (India), Caryologia: International Journal of Cytology, Cytosystematics and Cytogenetics, DOI:10.1080/00087114.2013.856088
To link to this article: http://dx.doi.org/10.1080/00087114.2013.856088
PLEASE SCROLL DOWN FOR ARTICLE
Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) containedin the publications on our platform. However, Taylor & Francis, our agents, and our licensors make norepresentations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose ofthe Content. Any opinions and views expressed in this publication are the opinions and views of the authors,and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be reliedupon and should be independently verified with primary sources of information. Taylor and Francis shallnot be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and otherliabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to orarising out of the use of the Content.
This article may be used for research, teaching, and private study purposes. Any substantial or systematicreproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in anyform to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http://www.tandfonline.com/page/terms-and-conditions
Department of Botany, Punjabi University Patiala, Punjab, 147 002, India
Intensive exploration and evaluation of cytomorphological diversity has been carried out on 380 species of 127 generabelonging to 28 families of sub-class Polypetalae of flowering plants from Kashmir (Jammu and Kashmir) and Kangraand Sirmaur districts (Himachal Pradesh) of the Western Himalayas. The cytological investigations of these species overa period of three years revealed new and varied chromosome numbers for 100 species globally and 50 species in India,making a substantial addition to the knowledge of the genera to which these species belong. To obtain a comprehensivecytological picture of each of these genera, chromosomal data have been updated by compiling the literature on previouschromosomal numbers and supplementing it from the present studies. The final form is now ready to show the statusboth at global and Indian levels for various parameters like total number of taxonomically known species, number ofcytologically determined species along with intraspecifically added number of cytological taxa, presently inferred basicnumbers, level and frequency of polyploids, and information on number of species per genus carrying inter- andintraspecific euploid and aneuploid variability at the genus level. Of the total 127 genera, 39 genera have 75% or morecytologically worked out species. Addition of cytotypes in many cytologically known species has resulted in anenhanced number of chromosomal races/cytological taxa over such species, in the majority of genera, justifying the evergrowing need to make population based intensive studies of any plant species. The data show that monobasic anddibasic genera are less common than tribasic and polybasic ones. Genera with x = 8 are most common, followed by x =7 and x = 6. Of 127 genera, 47 genera exhibit polyploidy of up to 25%; 22 genera have 26–50%; 15 genera have51–70%; and 26 genera have 76–100% polyploidy, while 17 genera lack polyploidy altogether. Interspecific and/or intra-specific euploid cytotypes such as diploids plus polyploids or with “polyploid series” are present in most of the 107 gen-era. Intraspecific aneuploid chromosome numbers are also shown by 100 genera. Since these genera belong to differentfamilies, so no generalization can be made at family level. However, at genus level chromosomal observations show theactive role of various evolutionary processes responsible for chromosomal diversity in the majority of these generadistributed in the Western Himalayas of India.
Keywords: basic numbers; chromosome numbers; polypetalous; Western Himalayas
Introduction
As a part of our program to explore and evaluate geneticdiversity of Indian angiosperms in general, and polypet-alous plants in particular (Bir and Kumari 1979, 1981a,1981b; Kumari and Bir 1985, 1987, 1989, 1990), anincentive was received to carry out population-basedcytological studies on members of this group fromselected phytogeographical areas of the Western Himala-yas with altitude ranging from 400 to 4500 m. Plantmaterial has been collected from higher altitude localitiesof Kashmir and from Sirmaur and Kangra districts(Himachal Pradesh) for the first time. More than fouryears of continuous effort to collect the wild germplasmand study detailed population-based male meiosis in 380polypetalous species has provided vital cytological infor-mation, especially regarding the variability of intraspe-cific chromosome numbers. To understand this fully, ithas been decided to discuss first the overall chromosomenumbers of the genera to which these species belong.Therefore, the analysis of chromosome numbers of 127genera belonging to 28 families of Polypetalae ispresented in this paper on the basis of cumulative
worldwide information available from the previousliterature along with additions made from our presentinvestigations (Rani et al. 2010a, 2010b; Jeelani, Rani,et al. 2010, 2011a, 2011b, 2013; Rani, Kumari andGupta 2011a, 2011b; Jeelani, Kumari and Gupta 2011a,2011b, 2012a, 2012b; Kumar, Kumari, et al. 2011, 2012;Kumar, Jeelani, Rani, Gupta, et al. 2011, 2013a,2013b; Kumar, Jeelani, Rani, Kumari, et al. 2011, 2013;Rani, Kumar, Jeelani et al. 2011, 2012, 2013; Rani,Gupta and Kumari 2012; Rani, Kumari, Gupta et al.2013).
Number of taxonomically known species
It is important to assess the frequency of cytologicallydetermined species of each genus studied before analyz-ing their chromosomal data. To work out this parameterit is essential to have up-to-date data of taxonomicallyknown species at global and Indian levels for eachgenus. A perusal of floristic accounts given in differentFloras provides different figures for the number of taxo-nomic species in the genera, and an effort has been made
to include the latest version both at global and Indianlevels. Hence, the data given in column II of Table 1 isbased on taxonomic records available from different flo-ras and research papers. For world records, the informa-tion is obtained from different floras including efloras ofChina (http://www.efloras.org/flora_page.aspx?flora_id=2)and Pakistan (http://www.efloras.org/browse.aspx?floraid=5) as well as research papers, whereas data for Indiaare from Santapau and Henry (1973), Aswal andMehrotra (1994), Sharma and Balakrishnan (1993),Sharma and Sanjappa (1993), Sharma et al. (1993) andHajra et al. (1997) and many research papers.
Number of cytologically known species
The chromosome number data sources include chromo-somal atlases (Darlington and Wylie 1955; Fedorov 1974;Kumar and Subramaniam 1986; Khatoon and Ali 1993),chromosome number indexes (Ornduff 1968, 1969;Moore 1970–1977; Goldblatt 1981–1988; Goldblatt andJohnson 1990–2003), IAPT/IOPB and SOCGI chromo-some reports, as well as more recent findings of chromo-some numbers by us. This variety of sources highlightsthat chromosome number lists have multiplied tremen-dously since the time of Darlington and Wylie (1955).
From the literature it is clear that during the past fewdecades the number of chromosomally known species offlowering plants has rapidly increased. Likewise, therehave been major contributions to the cytology of poly-petalous plants. Important contributors from outside Indiainclude Zhou et al. (2002), Lihová et al. (2003), Ghaffari(2004), Yan-Jun et al. (2006), Wang et al. (2008), Shenget al. (2010), Gholipour and Sheidai (2010), Gömürgenet al. (2011), Ranjbar et al. (2012), Chung et al. (2013),and de Resende et al. (2013). Major contributions overthe past few decades from India include Sharma andSarkar (1967–1968), Sharma (1970), Roy and Sharma(1971), Chatterjee and Sharma (1972), Sanjappa (1979),Hore (1971, 1980), Panigrahi and Purohit (1984),Subramanian (1985), Govindarajan and Subramanian(1986) and Vaidya and Joshi (2003). Some of the recentcontributors for the Western Himalayan polypetalousplants in particular include Pimenov et al. (2006), Kumarand Singhal (2008, 2011, 2013), Singhal and Kumar(2008), Gupta et al. (2009), Singhal and Kaur (2009),Singhal et al. (2009, 2010, 2011), Kaur et al. (2010),and Kumar et al. (2010).
The number and frequency of cytologically deter-mined species, as shown in column III of Table 1,reflects the attention received from cytologists at theIndian level in the backdrop of the worldwide status ofthese genera. Considering a 75–100% frequency as anarbitrary threshold level of cytologically known species,it is seen that certain genera have achieved more atten-tion at global (39 genera) and Indian levels (54 genera).Frequencies of 50–75% can be taken as a moderatelevel, and are represented by 32 and 30 genera at globaland Indian levels, respectively. Genera with fewer than
50% cytologically reported species can be taken as alower frequency level, seeking more attention in 56 and43 genera at global and Indian levels, respectively. Sowhatsoever has been cytologically accomplished forthese genera till now is being analyzed here to estimatethe role of various evolutionary processes in this limitedstock of genera belonging to Polypetalae, met with inthe Western Himalayas (India).
Number of cytological taxa/cytotypes
In column number VII of Table 1, the number ofcytotypes/chromosomal races is given against the totalnumber of cytologically known species of the genus(column III), pointing out the increasing number of cyto-logical taxa for each genus. Further, segregation of thenumber of the total cytological taxa of any genus leads toan insight into the range and frequency of increasing orderof 2n chromosome numbers with number of cytotypescarrying particular chromosome numbers given inparenthesis. This information is a collective measure ofinter- and intraspecific variability of the genera at globaland Indian levels. It is further witnessed that most of thegenera have predominantly 2n chromosome number vari-ability, except for seven genera with a single cytotypeeach and lacking variation: Bergenia, Coronopus, Dalber-gia, Ferula, Myricaria, Parochetus and Selenium at theglobal level. It is interesting to note that there are 26 othergenera with chromosome number variability in speciesfrom outside India, however, in India these are repre-sented by a single cytotype for each genus (see Table 1).
Variability of chromosome numbers
From the literature, nine genera have the lowest 2nchromosome numbers, of less than 10; however thesereports have not been confirmed and hence may beconsidered exceptional. These include Viola modesta2n = 4 (Erben 1996), Arabidopsis thaliana 2n = 6 (Titova1935), Impatiens leschenaultia 2n = 6 (Zinoveva-Stahevith and Grant 1982), Hypericum undulatum 2n = 8(Guillén et al.1997), Impatiens latifolia 2n = 8 (Rao et al.1986; Ayyangar et al. 1987), Indigofera richardsiae 2n =8 (Frahm Leliveled 1966), Pelargonium elongatum 2n = 8(Gibby and Westfold 1986), Sanicula rupiflora 2n = 8(Dobeš et al. 1997), Trifolium longipes 2n = 8 (Darlingtonand Wylie 1955), Viola dirimliensis 2n = 8 (Parolly andEren 2006); and Lathyrus pratensis, 2n = 9 (Dobeš et al.1997).
Taking lower chromosome numbers as establishedcommon diploid numbers for calculating the primarybasic numbers, 87 genera are recognized with lowestchromosome number, as 2n = 10 (eight genera), 2n = 11(one genus, Sesbania, with an odd and exceptionalnumber, hence not to be counted for calculating basicnumbers), 2n = 12 (19 genera), 2n = 14 (25 genera),2n = 16 (21 genera), and 2n = 18 (13 genera).The remaining 31 genera with similar details and lowest
Some genera have a wide range of chromosome num-bers. In such genera chromosome numbers reached as 2n= 100 or more than this previously. In certain genera somespecies have higher chromosome numbers, e.g. Acacia(A. heburclada 2n = 208), Arenaria (A. ciliate 2n = 100,120, 160, 200); Geranium (G. anemonifolium 2n = 68,128; G. regelii 2n = 52,128), Meconopsis (M. grandis 2n= 164), Palargonium (P. roseum 2n = 154), Ranunculus(R. glabrifolius 2n = 144), Sedum (S. farinosum 2n =c.384; S. ebracteatum 2n = 40 + 1B, 80 + 0 – 2B, 160,180, 200, 210; S. rupestre 2n = 56, 122, 140, 168,S. sexangulare 2n = 74, 111, 148, 185), Silene (S. ciliata2n = 24, 25, 26, 36, 48, 120, 149–165, 155, 192, 228,264, 312); Stellaria (S. palustris 2n = 198) andThalictrum (T. dasycarpumi 2n = 168). Detailed explana-tion for these high numbers is not always available inthe literature, although some may represent naturalpolyploids, and others may be the result of tissue culturematerial studies or artificially produced polyploids, etc.
Basic numbers of genera
Before discussing the ploidy level, it is essential to knowthe basic chromosome numbers of the taxa. An inferenceof an accurate basic numbers is little cumbersome in thosegenera which are marked with large amount of chromo-some numbers variability. From the cytological literature,generally the basic numbers are based on gametic numbersof the species with the lowest 2n chromosome numbers inthe genus. However, in some of the genera, high chromo-some numbers are presumed to be multiples of lowernumbers which do not actually exist (Stebbins 1958), andthus considered for taking their gametic numbers to beaccepted as basic numbers. To help further, sometimesother criteria are also used, e.g. the number of nucleolarchromosomes in a complement (Gates 1942), or the num-ber of chromosomes with secondary constrictions percomplement (cf. Sharma 1976) or secondary associationsof the chromosomes during meiosis-I (Darlington andMoffett 1930; Lawrence 1931; Moffett 1931), but eachsuch method has its own limitation. Raven (1975) has sug-gested that a prerequisite for calculating the original basicnumber of any group is a wide knowledge of its phylog-eny. In line with a proposal given by Grant (1982a,1982b), that sufficient data pertaining to chromosomenumbers is a prerequisite for calculating the basic chromo-some numbers of a genus and consideration has to begiven to the maximum number of species showing the par-ticular gametic number and due importance is to be givento those chromosome numbers on which intraspecificeuploid series are formed.
Regarding the genera under consideration, the basicnumbers were suggested a long time ago and are clearly
shown in the chromosome atlas of Darlington and Wylie(1955), except for Pleurosperum, Vicatia, Alysicarpus,Flemingia, Uraria and Abelmoschus, which were proba-bly not determined at that time. Fernandes and Franca(1975) cited basic numbers of the genera pertaining todifferent families studied from Mozambique and in 1978gave similar information regarding legumes fromPortugal. Later on, Grant (1982a) published a mono-graphic work, “Periodicities in the chromosome numbersof the angiosperms”, on the basis of extensive informa-tion available from chromosome number compilationsappearing up to 1974. He suggested the basic numbersfor polyploid series in monocotyledonous and dicotyle-donous genera by taking into account a particular basicnumber and the genus along with its related family in aclear form. In this way, on the basis of 7952 cytologi-cally determined species of dicotyledons alone andgametic chromosome numbers given for these taxa rang-ing from n = 2 to n = 250, he evaluated data separatelyfor herbaceous and woody species in the paper, and thepicture is very clear for each genus to know which basicnumber(s) makes euploid series. From India, Kumari andBir (1987) compiled the chromosome numbers of alllegumes and then worked out the basic numbers of allthe 337 genera that were cytologically known by thattime globally. Since then, there have been a large num-ber of studies adding to the information on chromosomenumbers of these flowering plants. Recently, Garbariet al. (2012) presented a concise history of chromosomenumbers of the Italian flora from 1925 to the present.Such studies, however, provide knowledge on chromo-some numbers mostly of selected groups of plants fromparticular areas only and hence result in scattered infor-mation. So, it is necessary to revise the basic numbers inall the polypetalous genera worked out at present in thelight of currently updated chromosomal data before accu-rately assessing the role of evolutionary processes suchas polyploidy in these genera.
Having a fresh look on the range of 2n chromo-some numbers and number of species or cytologicaltaxa of 127 genera belonging to 28 families sharingthese numbers, it is realized that basic numbers of allthese genera cannot be calculated or described uni-formly by using any single criterion. One thing is clearfrom the literature that generally basic chromosomenumbers have been deciphered mathematically and thebasic numbers making euploid series, however, aredefinitely taken as established numbers. At the sametime, there are chromosome numbers in certain generawhich do not fit in this measure, including diploids andsingled out polyploids, and in many cases these arecoupled with aneuploid variations. In such cases thebasic chromosome numbers of any plant group need tobe more accurately inferred after adding factors such asinterrelationships with allied taxa, especially at intraspe-cific levels through population-based study covering awide range of altitudes and habitats. The criteriaadopted here are explained below.
Caryologia: International Journal of Cytology, Cytosystematics and Cytogenetics 15
(1) Regarding primary basic number(s), it is importantto see the frequency of cytological taxa based onparticular basic numbers to deduce these, which isdecided on the basis of maximum species/cytolog-ical taxa supporting such number(s). Out of these,one basic number with maximum depiction isregarded as common basic number as shown byunderlying such numbers in column X of Table 1.However, in some of the genera, more than onebasic number finds very high representation mak-ing the situation complex and has to be acceptedas another common basic number. There is nodoubt that in certain genera, the high frequency ofmore successful cytological taxa are available withbasic numbers which are secondarily derived,along with relatively less frequent taxa markedwith primary basic numbers.
(2) There are nine genera as discussed earlier andmarked with very low 2n chromosome numbers,even lower than commonly accepted numbers as2n = 10. Further, it is noted from the literature thatsuch cytotypes are represented mostly by single ora few taxa. An overview of chromosome numbersvariations in these, otherwise cytologically well-studied genera give only one option to considerthese extremely low chromosome numbers possi-bly either to be of haploid plants or some experi-mentally handled materials or some unique plants.Hence, the status of low chromosome numbers insuch cases is to be taken with caution and their“half numbers taken as basic numbers” are shownwith question mark in column X of Table 1. Infact, for consideration of level of ploidy, these “2nnumbers” are straightway considered as “equiva-lent to basic numbers”. Some of the basic numbersarbitrarily calculated from stray/sporadic associ-ated chromosome numbers, in certain species areto be taken with caution and casually regarded asdoubtful as shown in parenthesis in column X ofTable 1.
Basic numbers and categorization of genera
1. As recorded in most genera (86 of a total of 127 gen-era), the most authentic way remains the same as previ-ously adopted as a general and popular method by variousscientists i.e., the gametic number(s) of the species withlowest 2n chromosome number or a few conjunctive lowernumbers of the euploid series to be taken as basic number(s). These are further subcategorized (a) typical ones as allthose fitting strictly to this basic rule and (b) those whichalso carry some other aneuploid chromosome numbers incertain species, existing mostly as associated numbersalong with regular numbers, and thus, ignored for inferringbasic numbers. These are given below.1a. Monobasic. In all, 16 genera are strictly monobasic,i.e. the species existing mainly as diploids or also having
polyploids, but based on single basic number. Thisinformation is available in the literature, and here thesame basic numbers are just confirmed but on the basisof revised data. These genera are Agrimonia (x = 14),Albizia (x = 13), Berberis (x = 14), Bergenia (x = 17),Coronopus (x = 16), Dalbergia (x = 10), Ferula(x = 11), Geum (x = 7), Grewia (x = 9), Murraya(x = 9), Myricaria (x = 12), Parochetus (x = 8), Sanicula(x = 8), Selinum (x = 11), Sibbaldia (x = 7) and Urena(x = 7).
2. In the case of 12 genera with relatively fewer cytolog-ically determined species per genus, some new basicnumbers are added here to the already established basicnumbers, as follows.
2a. In nine genera, proposed basic numbers are thosewhich either (i) make euploid series or (ii) have beenreported independently in one or more than one speciesas listed in Table 2.
2b. The basic numbers proposed here are half of someof the 2n dysploid numbers existing independently assuccessful cytotypes in some species. (Some odd chro-mosome numbers occurring only associated with estab-lished numbers in the same species are ignored forcalculating basic numbers.) Two examples of such gen-era include Acacia (x = 13, 14, 19, 20) with only18.11% species being determined with the establishedbasic number x = 13, where proposed basic numbers arex = 14, 19, 20 (ignored 2n chromosome numbers are 39,44) and Thlaspi (x = 7, 9, 12, 13) with common basicnumber x = 7, where proposed basic numbers are x = 9,12, 13 (ignored chromosome number is 2n = 40).
2c. In case of one genus Epilobium, having x = 9, 10, 12,13, 16, the proposed basic numbers are x = 10, 12, 13,16, showing a common basic number of x = 9. EarlierRaven (1988) proposed an ancestral number x = 18 forthis genus. However, due to the availability of 2n = 18 infour species (Table 1), x = 9 has to be taken as basicnumber on the basis of the lowest gametic number whichalso makes euploid series. Further, due to occurrence ofpolyploid series as 2n = 20, 30 as well as 2n = 26 presentindependently in three species, x = 10 and x = 13, respec-tively are to be retained. Basic numbers x = 12 for 2n =24 and x = 16 for 2n = 32 are doubtful and need to betaken with caution because these chromosome numbershave never been confirmed again for any species.
3. There are 14 genera exhibiting a dysploid series of 2nchromosome numbers, thus with a polybasic nature in
the form of dysploid basic numbers, which existindependently. Further, variable trends are there and maybe noted as ascending or descending or either bothascending and descending series in relation to mostcommon basic chromosome numbers of these genera.The examples are Arenaria x = 7, 8, 9, 10, 11, 12, 13(common basic numbers x = 10, 11); Arabidopsis x = 5,6, 7, 8, 9, 10, 11, 13 (common basic number x = 8; afew higher numbers might be the result of hybridizationfollowed by diploidization of the lower numbers);Astragalus x = 6, 7, 8, 11, 12, 13 (common basic num-ber x = 8); Caltha x = 8, 10, 12, 14 (common basicnumber x = 8); Cardamine x = 6, 7, 8, 9, 10, 17(common basic number x = 8); Geranium x = 9, 10, 11,12, 13, 14, 15, 16, 17, 23 (common basic number x =14); Hypericum x = 7, 8, 9, 10, 12, 19 (common basicnumbers x = 8, 9); Impatiens x = 5, 6, 7, 8, 9, 10(common basic numbers x = 7, 8, 9 in agreement withthe proposal of Song et al. [2003] that frequent basicnumbers are x = 7, 8, 9 and 10); Lupinus x = 7, 9, 12,16, 17, 19, 20, 21, 22, 25, 26 (common basic number x= 12). Oxalis x = 5, 6, 7, 8, 9 (common basic number x= 7); Pelargonium x = 7, 8, 9, 10, 11, 12, 15 (commonbasic number x = 11); Saxifraga x = 5, 6, 7, 8, 9, 10, 13(common basic number x = 8, supporting the earlierobservation by Kumar Jeelani, Rani, Gupta, et al.[2011]); Sedum x = 5, 6, 7, 8, 9, 10, 11, 13 (commonbasic numbers x = 7, 8, 9, supporting the earlier postula-tions of Ehrendorfer [1963] that dysploid changes of thebasic chromosome numbers in Sedum are probably dueto chromosome fusion or fission rather than to aneu-ploidy, and also supporting t’Hart [1991] that cytologicalvariations in Sedum are due to dysploid changes at thediploid as well as at the polyploid levels); and Viola x =5, 6, 7, 8, 9, 11, 13, 17 (common basic numbers x = 5,9, 13).
4. There are six genera showing relatively higher basicchromosome numbers. It is sometimes supposed thathigher basic numbers arise from lower numbers of pre-sumed diploids which do not exist, hence these higherbasic numbers are regarded to be paleobasic in nature,arising through hybridization coupled with diploidizationof lower numbers as proposed earlier by Grant (1982b)for Erythrina and Hebe (x = 21), Fraxinus and Osman-thus (x = 23), Doronicum (x = 30), and Tilia (x = 41).At present, such genera include: Malva x = 12, 18, 20,21 (these might have arisen from x = 6, 9, 10, 11); Mal-vastrum x = 12, 15, 16, 17, 18, 21, 22 (the commonnumber is x = 12 and paleoploids are also coupled withdysploid ascending numbers); Prinsepia x = 14, 16(possibly paleobasic because x = 7, 8 is a common basenumber in the many allied genera of the family); Pyrus x= 17, 21 (possibly paleobasic because x = 7 is acommon base number in the many allied genera of thefamily); Abelmoschus x = 18, 20 (these might havearisen from x = 9, 10); and Gypsophila x = 6, 10, 12,13, 15, 17 (this shows a normal basic number of x = 6
Caryologia: International Journal of Cytology, Cytosystematics and Cytogenetics 17
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plus other discontinuous ascending basic numbers withthe most prevalent numbers being x = 15 and 17).
5. There are three genera that show the presence of taxawith diploid numbers for which basic numbers are takenas their half numbers, but that also carry taxa with poly-ploid numbers which are not the multiples of the samebasic numbers; these can be explained only by presum-ing supplementary basic numbers on the basis of nonex-istent hypothetical diploid taxa. In Abutilon with x = 7,8, 9, diploid and polyploid taxa suggest x = 7 and x = 8as basic numbers, but a cytotype with 2n = 36 can beexplained as tetraploid only on the basis of a presumedadditional basic number of x = 9. In Heracleum with x =10, 11, the count of 2n = 40 reported in three species asindividual numbers or associated with 2n = 20, can beexplained as tetraploid only on the basis of presumedbasic number as x = 10. In Rorippa with x = 6, 8, achromosome number of 2n = 28 is reported indepen-dently in four different species; this can be explained astetraploid only on the basis of a presumed basic numberof x = 7.
6. There are four genera with miscellaneous details asfollows.
6a. Cerastium shows x = 9, 10, 17, 19, where morecommon basic numbers are x = 9, 10, and less com-mon basic numbers are x = 17, 19. x = 17 is calculatedon the basis that 2n = 34 is found in a significantnumber of species. Similarly, 2n = 38, is also noted in18 species; hence, to be based on x = 19. Further, thesehigher numbers are likely to be paleobasic, arisingthrough hybridization of the lower numbers 9 and 10.Boşcaiu et al. (1999), however, suggested x = 18 to bethe main and secondary evolved basic number forthis genus, giving a clear statement that there is noCerastium species with 2n = 18. While making thestatement, perhaps they did not take into account2n = 18 already reported in C. lethospermifolium(Krogulevich 1971), which was later confirmed as oneof the cytotypes in C. semidecandrum, i.e. 2n = 18, 36,37 (Dmitrieva 2000).
6b. For Trigonella with x = 7, 8, 9, 11, there is no doubtthat x = 8 is the most common basic number, but it isproposed that the number x = 7 also supports the serieswith 2n = 21 and 2n = 28, both cytotypes being presentin two different species. Another basic number (x = 9) isinferred from two different species exhibiting 2n = 18.Since seven cytotypes have 2n = 44, these are supposedto be paleoploids based on x = 11. However, some oddchromosome numbers (2n = 17, 31) associated with reg-ular euploid chromosome reports seem to be an outcomeof frequent hybridization and cultivation in a fewspecies. For Meconopsis with x = 7, 11, on the basis ofprevious information alone, variations in the chromo-some numbers are shown ranging from 2n = 22 to 164.Interestingly, the present study reports for the first time
the diploid cytotype of M. latifolia from Kashmir with2n = 14. This settles the debate of whether x = 7 or x =14 is the primary basic number of the genus, in favor ofx = 7. Some ambiguous chromosome numbers, e.g. 2n =74, 76, 82, and even higher numbers such as c.118 and164, are found to be associated with higher regular chro-mosomes numbers, hence such numbers can be ignoredfor deciding the basic chromosome numbers. However,earlier, x = 7 and x = 8 (Ernst 1965; Ratter 1968) as wellas x = 7 and x = 11 (Darlington and Wylie 1955) weresuggested to be the most common basic numbers in thegenus.
6c. For Alchemilla there have been problems in deter-mining the exact chromosome numbers, the basic num-bers and karyograms (Izmailow 1982). The basicnumbers of Alchemilla are suggested to be x = 8, 10, 17at present. Otherwise, x = 7 being also the basic numberof the Rosoideae, has been accepted well earlier for thisgenus (see Gentcheff and Gustafsson 1940). Löve andLöve (1975) and Raven (1975), however, assumed a pri-mary basic number of x = 8, which has been acceptedby most authors since then. Here, x = 8 is also seen tobe the most common basic number. The basic number ofx = 10 seems to be coming from lower numbers as evi-dent from making series only in polyploids. The otherchromosome number x = 17 is decided, since it makeseuploid series in nine species.
Polyploidy
Incidence
Polyploidy in angiosperms has been studied for almost acentury now, dating back to the work of De Vries (seeGates 1909). The importance of polyploidy in evolutionand speciation of plants has been emphasized byKuwada (1915), Müntzing (1936), Darlington (1937),Löve and Löve (1949), Stebbins (1950, 1971, 1985),Wendel and Doyle (2005), Cui et al. (2006), Otto(2007), Wood et al. (2009) and Meng et al. (2012). Poly-ploidy is an important process in the evolutionary historyof plants and has a profound impact on biodiversitydynamics and ecosystem functioning (Wendel 2000;Ainouche and Jenczewski 2010). Polyploidy and itsoccurrence within one species is a common phenomenonamong plant groups (Soltis and Soltis 1993; Wendel2000; Soltis et al. 2004; Hodálová et al. 2007; Ojiewoet al. 2007). Following the work of Stebbins (1940,1950) in particular, polyploidy became a major focus ofbiosystematic research. Manton (1932) and Stebbins(1950) have said that polyploidy may induce diversity ofform and speciation, but has no significance in the originof new major taxonomic groups. Further, polyploidy issupposed to protect plants against immediate deleteriouseffects of most gene mutations (Aase 1935) and therebyit allows greater polymorphism and thus polyploidsattain greater adaptability (Stebbins 1950). As a result,plant scientists have long recognized that polyploid
lineages may have complex relationships with each otherand their diploid ancestors, making application of speciesconcepts problematic (reviewed in Rieseberg and Willis2007; Soltis et al. 2007). As polyploidy is so importantit has been thoroughly investigated in the genera studiedherein. In Table 1 the number and frequency (based ontotal number of chromosomally reported species) ofpolyploid species of each genus are shown in column Vand the level of euploids is shown in column VI. Fromthe analysis of this data on world-wide basis, it is cate-gorized further, to have deeper insight of this parameteras presented in Table 3 providing information on all the127 genera.’ It is noted that there are 17 genera lackingpolyploidy; 47 with up to 25% polyploidy; 22 with26–50% polyploidy; 15 with 51–75% polyploidy; and 26with 76–100% polyploidy. Thus there are more genera
with up to 25% polyploidy. The most commonpolyploidy level shared by almost all the genera istetraploid, except for in genus Berberis (at hexaploidlevel) and another unique example of genus Murraya (at12x level). The highest polyploidy level is quite varied,exhibited at different levels in different genera as 4x, 6x,8x, 10x, 11x, 12x, 14x, 16x, 18x, 26x, 28x and 48x(Table 3). The lowest level, 4x, belongs to generaMomordica and Podophyllum, and the highest level, 48x,belongs to genus Sedum (also see Table 1).
Polyploidy and habit correlation
According to Stebbins (1971) and de Wet (1980), theorigin and success of polyploidy quite often dependsupon habit–habitat relationship and breeding system.
Table 3. The information pertaining to 127 polypetalous genera studied at present with details of polyploidy.
Serialno. Name of family
Numberof generastudied
Number of polyploid genera (habit*)Level ofpolyploidy
Nil < 25% 26–50% 51–75% 76–100%Most
common Highest
1. Apiaceae 13 3B 9(7B+1A+1C)
1B — — 4x 8x
2. Balsaminaceae 1 — — 1 C — — 4x 11x3. Berberidaceae 1 — 1 F — — — 4x 4x4. Brassicaceae 11 — 3 C 4 C 2 C 2 C 4x 18x5. Caesalpiniaceae 3 — 1 G — — 2 G 4x 8x6. Caryophyllaceae 6 — 1 C 1 B 2 C 3 C 4x 26x7. Crassulaceae 1 — — — — 1 C 4x 48x8. Curcurbitaceae 1 — — 1 C — — 4x 4x9. Fabaceae 30 9
(6D+1G+2B)16
(7 D+1 G+2A+2F+3C+1E)
2C 1 C 2 D 4x 22x
10. Fumariaceae 2 — 1 C — — 1 C 4x 18x11. Geraniaceae 2 — 1 C — 1 C — 4x 14x12. Hypericaceae 1 — — 1 E — — 4x 6x13. Malvaceae 7 — — 2 D 1 D 4
22. Rutaceae 2 1 B — 1 G — — 12x** 12x23. Saxifragaceae 2 1 B — — — 1 C 4x 22x24. Tamaricaceae 1 1 F — — — — — —25. Tiliaceae 3 — 1 G — 1 D 1 E 4x 10x26. Violaceae 1 — — — 1 D — 4x 16x27. Vitaceae 1 1 F — — — — — —28. Zygophyllaceae 1 — 1 C — — — 4x 8xTotal 127 17 47 22 15 26
*Symbols for habit: A – annual herbs; B – perennial herbs; C – annual, biennial and perennial herbs (annual biennial less in number but perennialmore); D – herbs and shrubs; E – herbs, shrubs and trees; F – shrubs; G – shrubs and trees.**In Rutaceae, only single polyploid report of genus.
Caryologia: International Journal of Cytology, Cytosystematics and Cytogenetics 19
According to Stebbins (1938, 1950, 1971), “higher per-centages of polyploidy within a modern genus are foundin perennial herbs and lowest in annuals. The figures forwoody plants are intermediate but approach more nearlythose for annual than for perennial herbs”. de Wet(1980) explained this by suggesting that a high rate ofpolyploidy in perennials could be their characteristichabit, providing repeated chances to sort out desirablecombinations in the newly found polyploids so as tocompete better with available habitat. Wright (1976),however, rejected the concept of polyploidy–habit corre-lation. The genera studied here conform to the growthhabit shown for each genus in Table 1 and are catego-rized as: annual herbs with all five genera being polyp-loids; of 33 perennial herb genera 26 are polyploids; of39 annual, biennial and perennial herb genera 37 arepolyploids; of 22 genera with both herb and shrub habit17 are polyploids; all eight genera including herbs,shrubs and trees are polyploids; of seven genera repre-sented only by shrubs four are polyploids; and of 13woody genera (shrubs and trees only), 12 are polyploids.Regarding the frequency of genera with different habitsrepresented by different symbols from A–G as shown inthe footnote of Table 3, it is inferred that overall perenni-als have a higher level of polyploidy and genera with awoody habit show frequency of polyploidy which lies inbetween the genera marked with annual and perennialherbs. These observations conform to those of Stebbins(1971).
Euploid variations
Euploid variations are prevalent in most of the genera, asevident from the presence of diploids along withpolyploids or only polyploid complexes in 890 speciesbelonging to 107 genera of 26 families globally, and 99species belonging to 49 genera of 22 families in India,as shown in column VIII of Table 1. The list of suchspecies cannot be provided here, therefore only the num-ber of species with more than one intraspecific euploidcytotype with their basic numbers are mentioned for eachgenus. In fact this column represents the story of moresuccessful base numbers responsible for producingcytotypes of euploid series within any species belongingto such genera at India level in the background of theglobal picture.
Aneuploid variations
Aneuploid differentiation at the diploid level contributesgreatly to species diversification in a genus (Wang et al.2013). According to Stebbins (1950, 1971, 1974), aneu-ploidy is the result of series of unequal translocations.Jones (1978) has attributed aneuploidy to centric fusions.In Grant’s (1982b) aneuploid–polyploid hypothesis, atlower levels of chromosome numbers paleopolyploidybecomes a less likely factor and basic aneuploidybecomes more important. Levin (2002) also discussed
the role of aneuploidy in relation to a shift in life historyand asexual mode of reproduction. Aneuploidy is oftencorrelated to the asexual mode of reproduction (apo-mixis). Nassar (2003) studied cytological and embryo-logical details of the apomictic clones of Manihotesculenta and correlated its occurrence to the aneuploidnature of the clones. According to De La Casa-Esperonand Sapienza (2003) and Bean et al. (2004) aneuploidymight be alleviated by the epigenetic silencing ofunpaired chromosomes. Meiotic irregularities and a highrate of non-disjunction may also lead to production ofaneuploids. According to Bandel (1974), aneuploid vari-ations form a series in which the gametic numbers ofrelated species form consecutive series. The data on theexistence of aneuploidy in 127 genera under consider-ation at present is given in column IX of Table 1. A totalof 746 species of 104 genera globally and 118 species of47 genera from India show chromosome numbers in theform of irregular multiplication of base numbers, andmay be diploid or polyploid or both diploid and poly-ploid. These aneuploid variations at intraspecific levelgiven here for a specific number of species per genusshows the frequency of such variants found in India inthe light of global data, thereby supplementing thegenetic diversity revealed through euploid variability.
Conclusion
For the first time, chromosome numbers of polypetalousplants from cytologically explored area of the WesternHimalayas have been compiled. The complete chromo-somal database is prepared not only on the basis of theliterature but also substantiated from present detailedpopulation-based meiotic studies from a vast area of thehigher altitudinal Himalayas of Kashmir and HimachalPradesh. The complete variability in chromosome num-bers at Indian and global level revels the genetic diver-sity at intraspecific level within each genus, along withinterspecific variability. The base numbers for all thegenera have been reconsidered in the light of updatedchromosomal data and presented in the most acceptableform. An exact assessment of the role of polyploidy andaneuploidy has been made available to ascertain theirrole in evolution of species belonging to these genera.An effort has been made to present the completeknowledge regarding chromosome number informationfor these 127 genera, for future use by researchers indifferent taxonomic treatments.
AcknowledgmentsThe authors are grateful to the University Grants Commission,New Delhi, for the award of Dr. D.S. Kothari Post-DoctoralFellowship to Dr. Syed Mudassir Jeelani and Rajiv GandhiNational Fellowship to Dr. Sanjeev Kumar. We are also obligedto Department of Science and Technology, New Delhi, for thehonour of Young Scientist Fellowship to Dr. Savita Rani.Thanks are also due to the Head, Department of Botany,Punjabi University, Patiala, for the library facilities.
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