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Chromosome number of Orthophytum species (Bromeliaceae)
Abstract and Figures
The genus Orthophytum Beer comprises 53 species, all narrow endemics to south-eastern and north-eastern Brazil. In this study we present meiotic
and mitotic chromosome numbers of 12 species of this important genus in Bromeliaceae. For six of these taxa we are reporting
the first cytogenetic study. Orthophytum albopictum, O. amoenum and O. burle-marxii presented 2n = 100 chromosomes and O. hatschbachii, O. mucugense, O. vagans, O. supthutii, O. zanonii and O. ophiuroides showed 2n = 50 chromosomes. These results are consistent with the proposed basic number of x = 25 for Bromeliaceae family. In the genus Orthophytum, polyploidy seems to play an important role in chromosome evolution associated with habitat differentiation among diploid
and polyploid species.
KeywordsBromeliad-
Bromelioideae
-cytogenetics-meiotic behaviour-mitotic chromosome-polyploidy
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... The Bromeliaceae family is characterized by a base chromosome number of x = 25 chromosomes, with the majority of species being diploid (2n = 2× = 50) and rare cases of tetraploid (2n = 4× = 100) and hexaploid (2n = 6× = 150) species, e.g. within the genus Orthophytum (Louzada et al., 2010). Within the subfamily Tillandsioideae only some members of Tillandsia subgenus Diaphoranthema are reported as tetraploid (Till, 1992). ...
Epiarenic (sand-growing) Tillandsia vegetation in the hyperarid and arid region of the Chilean-Peruvian Atacama Desert represents an extreme case of adaptation in plant species-poor ecosystems. The involved species exist at the limit of terrestrial life and form mono/oligo-specific and very characteristic structures within the landscape. Covering thousands of square kilometers they represent the major carbon sink in the hyperarid Atacama core. The various Tillandsia species and respective vegetation may have evolved and adapted independently to this extreme environment. The most abundant vicariant diploid species are T. landbeckii in Chile and T. purpurea in Peru. Spatio-temporally varying distribution range overlaps may have caused potentially adaptive gene flow between different species leading to present day gene pools. Using species distribution modelling we explored the idea that from Last Glacial Maximum (LGM) onwards both species shifted their distribution ranges, which resulted in the formation of varying suture zones from Peru towards northern Chile. We further explored genetic data from a Tillandsia loma vegetation in Southern Peru with three sympatrically growing species exemplifying inter-species gene flow crossing even ploidy levels. This mechanism highlights a strategy to evolve and adapt more rapidly to environmental changes in extreme arid and hyperarid habitats and provides an opportunity for Tillandsia populations to efficiently conserve new genotypes via subsequent clonal propagation.
... Chromosome number databases are also an important characteristic for plant evolutionary studies and may provide information on polyploidy and other highly significant genome changes (21)(22) and are useful tools for systematic comparisons of geographical or taxonomical groups of plants (23). ...
A new genus, Aytacia Yıld. and a new species, A. turkica Yıld. (Asteraceae) based on Scorzonera s.l. Abstract A new monotypic genus from Turkey, Aytacia Yıld. is introduced to the scientific world. This new genus is based on partially S. boissieri Lipsch. of Scorzonera s.l. species with typical features such as dwarf, scapigerous, greyish, perennial plant; c. 8 x 2-3 cm, simple, linear-lanceolate to lanceolate, subfalcate leaves; 40-50 cm long, 1 per stem capitula with yellow flowers; 10 winged, glabrous achenes. Aytacia turkica Yıld. is described as a new species. The identification key of closely related genera of this new genus is provided. Türkiye'den Scorzonera L. s.l. kökenli yeni bir cins, Aytacia Yıld. ve yeni bir tür, A. turcica Yıld. (Asteraceae) Özet Türkiye'den yeni bir tek türlü cins, Aytacia Yıld. bilim dünyasına tanıtılmaktadır. Bu yeni cins, cüce, sibek, kül renkli, çok yıllık bitki; c. 8 x 2-3 cm boyutlu, yalın, şeritsi-mızrak uçsudan yalnızca mızrak uçsuya, yarı oraksı yapraklı; 40-50 cm boyunda her bir gövdede 1 kömeçli; sarı çiçekli; 10 kanatlı, tüysüz aken özellikleriyle Scorzonera'nın s.l. S. boissieri Lipsch. türüne kısmen dayanmaktadır. Aytacia turkica Yıld. yeni bir tür olarak betimlenmiştir. Bu cinsin, yakın cinslerine ilgin tanı buldurusu verilmiştir.
... Chromosome number databases are also an important characteristic for plant evolutionary studies and may provide information on polyploidy and other highly significant genome changes (21)(22) and are useful tools for systematic comparisons of geographical or taxonomical groups of plants (23). ...
A new genus from Turkey, Bilgea Yıld. is introduced to the scientific world. This new genus is based on S. sandrasica Hartvig & Strid and S. ulrichii Parolly & N.Kilian of Scorzonera s.l. species with typical features such as dwarf, subscapigerous, greyish, perennial plant; 2-6 cm long, unbranched, densely lanate, sericeous with long hairy stem; 2-5 cm long, simple, shortly oblanceolate, rosetted leaves; 10-18 mm long, usually 1 per stem capitula with yellow flowers; lanate achenes. Some new combinations and synonyms are made. The identification keys of closely related genera and species of this new genus are provided.
... Chromosome number databases are also an important characteristic for plant evolutionary studies and may provide information on polyploidy and other highly significant genome changes (21)(22) and are useful tools for systematic comparisons of geographical or taxonomical groups of plants (23). ...
... Chromosome number databases are also an important characteristic for plant evolutionary studies and may provide information on polyploidy and other highly significant genome changes (32)(33) and are useful tools for systematic comparisons of geographical or taxonomical groups of plants (34). (17). ...
... Chromosome number is an important character used for evolutionary studies of plants, providing information about polyploidy and genome changes (Guerra, 2008;Louzada et al., 2010). Data generated from such studies are a useful tool for systematic comparisons of geographic and taxonomic groups of plants (Peruzzi et al., 2012). ...
Plant species may be classified according to their karyotype features. Variation in chromosome features is believed to have accompanied evolutionary divergence of many plant and animal species. The cytological characteristics of crop species vary with geographical location of plants. Knowledge of the karyotype relationships can be explored for effective genetic and breeding studies, especially in crops like the Hausa potato (Solenostemon rotundifolius) that have not received adequate research attention. This paper reports the results of the karyotype analysis of ten accessions of the Hausa potato cultivated in some parts of Nigeria. The accessions were raised in plastic bowls containing vermiculite soil, from which root-tips were harvested for slide preparation and karyotyping. The conventional squashing in aceto-orcein of root tissues after heating was used. The tissues were photographed under Nikon Universal Microscope, equipped with an MC 100 camera. The chromosomes were then measured under x400 magnification using a micrometer. Results showed that all the accessions were diploid with somatic chromosome number of 2n = 2x = 64. The total length of long-arms ranged from 108.80 µm in accession Pankshin to 118.14 µm in accession NRCRI (1). The total length of short arms ranged from 81.88 µm – 89.34 µm. The total length of long plus short arms ranged from 199.88 µm - 200.06 µm. The mitotic phases varied with accessions. Similarly, the arm ratio, r-value, centromeric index, coefficient of variation, total form, intra-chromosomal index and inter-chromosomal index varied with the accessions. The accessions were grouped into four clusters: accessions Hong (1), Hong (2), Manchok and Gembu in cluster I; accessions Pankshin and Langtang in cluster II; accessions NRCRI (1) and NRCRI (2) in cluster III; accessions Bokkos (1) and Bokkos (2) in cluster IV. The principal component analysis showed that variation in the complement length and the centromeric position accounted for 99.997% of the total variation amongst the accessions. The study demonstrated that cytological differences exist in the Hausa potato. Some accessions showed close phylogenetic relationship, but others were distantly related. These differences could be explored for the improvement of the Hausa potato accessions cultivated in Nigeria.
Phylogenetic trouble unleashed
The first part of my thesis deals with a comprehensive phylogeny of the Bromelioideae subfamily. The family Bromeliaceae is subdivided into eight subfamilies, one of them is the Bromelioideae. Phylogenetic relationships among the Bromelioideae are still poorly understood and many of the extant genera are suspected to be not monophyletic. Especially Aechmea, the largest and most polymorphic genus constitutes many questions and the genus was used as a depot for taxonomically problematic species. The phylogenetic study presented here is the most comprehensive one so far, covering about half of the known species (434 of 965, Table 1) of Bromelioideae. The phylogeny was generated using plastid (atpB-rbcL, matK, rps16, ycf1_1, ycf1_6) and nuclear (AGT1_exon, ETS, G3PDH, PHYC, RPB2) genetic markers. The markers were analysed individually as well as combined using maximum likelihood and Bayesian analysis. The comparison of plastid vs. nuclear data revealed significant differences which were discussed in detail and hypothesised to indicate hybridisation in certain lineages. Nevertheless, the combination of both datasets increased the overall resolution of the phylogeny and was used to discuss the results in the light of previous studies. The entire phylogeny was divided into 32 groups for discussion. These groups represent potential genera or starting points for further studies in order to reorganise the polyphyletic genera of Bromelioideae into monophyletic lineages. Many extant genera of the eu-Bromelioideae were found to be not monophyletic. Monophyly was observed for the genera Acanthostachys, Billbergia, Cryptanthus, Disteganthus, Hoplocrypanthus, Lapanthus, Orthocryptanthus, Orthophytum, Rokautskyia, Ronnbergia, Sincoraea, Wittmackia and the monotypic ones (Deinacanthon, Eduandrea, Fascicularia, Hohenbergiopsis, Pseudananas). The genus concept proposed by Smith and Downs (1979) is therefore rejected, as well as the taxonomic utility of petal appendages, which were mainly used to delimit genera. In summary, this study and recent studies highlighted other morphological characters (e.g. pollen morphology, stigma type) as much more informative. However, no single character should be used to delimit genera and combinations of relevant characters are required. Even the petal appendages can pose a taxonomical important character at certain taxonomic level.
The combination of biogeography and phylogeny revealed that species of some groups which co- occur in a biome or region are also phylogenetically closely related. These groups were not recognised before because the misinterpretation of homoplastic characters led to wrong taxonomical conclusion. For example, the recent re-organisation of the Cryptanthoid group and the re-establishment of Wittmackia with the former Hohenbergia subgen. Wittmackiopsis species highlighted, among other characters, the importance of biogeography. Another case is the subgenus Neoregelia subgen. Hylaeaicum which is geographically and phylogenetically separated from the Nidularioid group and therefore has to be excluded.
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The large phylogeny presented here gives evidence for multiple invasions of the Brazilian biomes (Amazon Forest, Atlantic Forest, Cerrado, Caatinga) as well as of Central America and the Greater Antilles. It is important to note that the phylogeny is lacking resolution in the deeper nodes. Confident assumptions are therefore hindered and the historical biogeography of Bromelioideae remains cryptic. Anyway, the Atlantic Forest is nowadays the diversity hotspot of the core Bromelioideae and critically endangered. Extensive conservation efforts are required to protect the diverse flora, including the bromeliads.
The genetic markers used so far in bromeliad phylogenies provided only limited variation resulting in often unresolved complexes. The search for additional suitable genetic markers in bromelioid phylogenies yielded the nuclear marker AGT1. The amplified fragment consists of one well conserved exon region as well as a highly variable intron. The intron was too variable for aligning it across the entire bromelioid set. On the other hand, the intron provides relevant information for inferring phylogenies of closely related species groups (e.g. in Ananas, Cryptanthoid group). Furthermore, AGT1 is proposed as a genetic barcode in Bromelioideae because it poses much more information then the commonly used ones (e.g. matK).
Does size matter?
The second part of this thesis deals with the genome size evolution within the family Bromeliaceae. Samples from seven subfamilies were screened with the emphasis on the subfamily Bromelioideae. The data were combined with data from literature and the observed patterns were discussed in relation to known phenomena (e.g. correlations to environment and life form). In the second sub-chapter I have chosen the species Tillandsia usneoides to study the intraspecific genome size variation in combination with morphology and biogeography. Genome size and base composition were measured using the flow cytometry technique.
Bromeliaceae comprises mostly diploid species with predominantly 50 small chromosomes (2n), small genome sizes (0.59-4.11 pg) and normal GC content (36.46-42.21 %) compared to other families. Polyploidy was observed so far in the subfamilies Bromelioideae, Tillandsioideae and Pitcairnioideae. Triploids, tetraploids and potential hexaploids were identified. The genera show significant differences in holoploid genome size and base composition throughout the entire family. GC content is weakly positively correlated with genome size. Significant intraspecific genome size variation has been observed, including polyploidization, but no endopolyploidy and no variation in dioecious species. Within the subfamily Bromelioideae, the observed genome size between the early diverging lineages and the core Bromelioideae supports this division. The differences are due to a higher proportion of polyploids in the early diverging lineages and a significant higher
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GC content in the core Bromelioideae. Both groups differ in their life strategies and occupy principally different habitats with corresponding morphological adaptations. Hence, the early diverging lineages are predominantly terrestrial and xeromorphic. In contrast, the prevailing epiphytic core Bromelioideae are characterised by a tank habit and mostly adapted to more humid environments. Across the family and the subfamily Bromelioideae in particular, significant genome size differences between the different life forms have been observed, but no correlation to biomes within Brazil.
Tillandsia usneoides is the most widely distributed species of the family Bromeliaceae. It ranges from the southeastern United States to Argentina and Chile. Tillandsia usneoides grows epiphytic and is dispersed by seeds as well as by fragments of the plant. Within the species striking morphological differences can be observed as far as size characters are concerned. Morphotypes have shown to be stable in cultivation while growing under the same conditions. In order to investigate possible reasons for the variation the relative genome size of 75 specimens covering the whole distribution range was measured and combined with morphological, distribution and climatic data. Significant variation in the relative genome size corresponded to the morphological differences and reflected the north-south distribution gradient. Genome size and morphotypes showed a positive correlation, as well as with the mean temperature of the driest and coldest quarter and the minimal temperature of the coldest month.
The subfamily Bromelioideae is one of the most diverse groups among the neotropical Bromeliaceae. Previously, key innovations have been identified which account for the extraordinary radiation and species richness of this subfamily, especially in the so-called core Bromelioideae. However, in order to extend our understanding of the evolutionary mechanisms, the genomic mechanisms (e.g. polyploidy, dysploidy) that potentially underlie this accelerated speciation also need to be tested. Here, using PI and DAPI staining and flow cytometry we estimated genome size and GC content of 231 plants covering 30 genera and 165 species and combined it with published data. The evolutionary and ecological significance of all three genomic characters was tested within a previously generated dated phylogenetic framework using ancestral state reconstructions, comparative phylogenetic methods, and multiple regressions with climatic variables. The absolute genome size (2C) of Bromelioideae varied between 0.59 and 4.11 pg, and the GC content ranged between 36.73 and 41.43%. The monoploid genome sizes (Cx) differed significantly between core and early diverging lineages. The occurrence of dysploidy and polyploidy was, with few exceptions, limited to the phylogenetically isolated early diverging tank-less lineages. For Cx and GC content Ornstein–Uhlenbeck models outperformed the Brownian motion models suggesting adaptive potential linked to the temperature conditions. 2C-values revealed different rates of evolution in core and early diverging lineages also related to climatic conditions. Our results suggest that polyploidy is not associated with higher net diversification and fast radiation in core bromelioids. On the other hand, although coupled with higher extinction rates, dysploidy, polyploidy, and resulting genomic reorganizations might have played a role in the survival of the early diverging bromelioids in hot and arid environments.
Orthophytum Beer (Flora 37: 347, 1854). Type:
Prantleia glabra Mez [typification according to
L. B. Smith & Downs, Fl. Neotrop. 14(3): 1696,
1979]. — Bromelioideae — Lit: Smith & Downs
(1979: 1696-1710, Fl. Neotropica); Leme (2008:
key to the mello-barretoi-complex); Louzada &
al. (2010: cytology); Louzada & Wanderley
(2010: partial monograph of the vagans-clade);
Louzada (2012: unpublished monograph, with
key); Louzada & al. (2014: molecular phylogeny);
Leme & al. (2017: classification). Distr: E Brazil;
Atlantic Forest, Cerrado and Caatinga vegetations,
usually saxicolous. Etym: Gr. ‘orthos’, erect,
straight; and Gr. ‘phyton’, plant; for the erect
stems with well-spaced leaves of the type species.
(Taxonomic notes and a new species of the genus Orthophytum Beer (Bromeliaceae) from Chapada Diamantina,
Bahia, Brazil) – A new species of Orthophytum from “Parque Municipal Sempre-viva” (Mucugê, Chapada Diamantina,
Bahia, Brazil) is described and illustrated and its taxonomic relationship with O. humile L.B. Sm. and O. navioides (L.B.
Sm.) L.B. Sm. are discussed. In addition, new records and more complete description of O. navioides (L.B. Sm.) L.B. Sm.
are provided. A key to scapeless species of Orthophytum occurring in the Chapada Diamantina is also included.
The Bromeliaceae is characterized by a 2n chromosome number of 50, but exceptions have been reported. These include scattered polyploids and presumed aneuploid reductions in isolated species from subfamilies Tillandsioideae and Bromelioideae, and 2n = 34 or 36 for all species of Cryptanthus (Bromelioideae) thus far examined. Two hypotheses have been proposed that address the origin of the low chromosome number (2n = 34 or 36, compared to 50) in Cryptanthus. We have attempted to test these hypotheses using quantification of nuclear DNA by flow cytometry. DNA quantifications for examined Cryptanthus species fell into two groups. In one there was no significant difference between Cryptanthus and selected bromeliad species known to have 2n = 50. In the second, Cryptanthus species had approximately twice as much 2C nuclear DNA. Results partially support the hypothesis that the Cryptanthus chromosome number (2n = 34) originated by descending aneuploidy, a derived condition which, with other apomorphies, supports the hypothesis that Cryptanthus is derived within the subfamily Bromelioideae. First chromosome number reports are presented for two species of Cryptanthus and one species of Orthophytum. Communicating Editor: Alan Whittemore
Detailed karyotype studies have been carried out on 15 different species and varieties belonging to 7 genera of Bromeliaceae, viz. Ananas, Bilbergia, Caraguata, Cryptanthus, Dyckia, Neoregelia and Pitcairnia.Although gross homogeneity in the karyotype among the members of the 7 genera is noticed, yet a critical analysis shows that each species and variety is characterised by the distinctive karyotype of its own, particularly in nature of secondary constriction-so structural alteration of chromosomes has been the prime factor in evolution within the family.Out of the 4 tribes within this family, in Tillandsieae, the prevalent chromosome series is 8 or 16; in Bromelieae it is 9, 18 and 25 and in Pitcairnieae it is 25. It has been suggested that 8 represents the basic set for this family from which other numbers might have been derived. On the basis of past report and present investigations a rearrangement of different tribes is suggested-Tillandsieae with its basic set of 8 should represent primitive whereas Pitcairnieae with a series of 25 forms the present climax of evolution. The intermediate stages are possibly represented by Bromelieae some of which are common to Tillandsieae and others with Pitcairnieae.
... In Plant Speciation , Grant (1981) devoted five chapters (15% of the total text) to polyploidy, reflecting the importance of the topic both to the author and to plant biologists. We update Grant's (1981) coverage by highlighting some ...
Since chromosome doubling usually is associated with hybridization, the effects of doubling are difficult to uncouple from those of hybridity and recombination. Synthetic polyploids in crops typically are inferior to their diploid counterparts, under conditions to which the diploids are adapted. This has suggested to many that chromosome doubling is a hindrance to progressive evolution. Evidence is presented from biochemical, physiological, developmental, and genetic sources which indicates that the nucleotypic effects of chromosome doubling are not necessarily negative. Indeed chromosome doubling may 'propel' a population in to a new adaptive sphere, and render it capable of occupying habitats beyond the limits of its diploid progenitor. This postulate is consistent with what is known of the ecological tolerances of diploids and related polyploids. As the establishment of a polyploid subpopulation may occur within a short time span, chromosome doubling may bring about abrupt, transgressive, and conspicuous changes in the adaptive gestalt of populations within microevolutionary time. -from Author