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The mainly Australian grass genus Austrostipa (tribe Stipeae) comprising approximately 64 species represents a remarkable example of an evolutionary radiation. To investigate aspects of diversification, macro- and micromorphological variation in this genus, we conducted molecular phylogenetic and scanning electron microscopy (SEM) analyses including representatives from most of Austrostipa’s currently accepted subgenera. Because of its taxonomic significance in Stipeae, we studied the lemma epidermal pattern (LEP) in 34 representatives of Austrostipa. Plastid DNA variation within Austrostipa was low and only few lineages were resolved. Nuclear ITS and Acc1 yielded comparable groupings of taxa and resolved subgenera Arbuscula, Petaurista, and Bambusina in a common clade and as monophyletic. In most of the Austrostipa species studied, the LEP was relatively uniform (typical maize-like), but six species had a modified cellular structure. The species representing subgenera Lobatae, Petaurista, Bambusina as well as A. muelleri from subg. Tuberculatae were well-separated from all the other species included in the analysis. We suggest recognizing nine subgenera in Austrostipa (with number of species): Arbuscula (4), Aulax (2), Austrostipa (36), Bambusina (2), Falcatae (10), Lobatae (5), Longiaristatae (2), Petaurista (2) and the new subgenus Paucispiculatae (1) encompassing A. muelleri. Two paralogous sequence copies of Acc1, forming two distinct clades, were found in polyploid Austrostipa and Anemanthele. We found analogous patterns for our samples of Stipa s.str. with their Acc1 clades strongly separated from those of Austrostipa and Anemanthele. This underlines a previous hypothesis of Tzvelev (1977) that most extant Stipeae are of hybrid origin. We also prepared an up-to-date survey and reviewed the chromosome number variation for our molecularly studied taxa and the whole tribe Stipeae. The chromosome base number patterns as well as dysploidy and whole-genome duplication events were interpreted in a phylogenetic framework. The rather coherent picture of chromosome number variation underlines the enormous phylogenetic and evolutionary significance of this frequently ignored character.

The mainly Australian grass genusAustrostipawith ca. 64 species represents a remarkable example of an evolutionary radiation. To investigate aspects of diversification, macro- and micromorphological variation in this genus we conducted a molecular phylogenetic and scanning electron microscopy (SEM) analysis including representatives from all of its accepted subgenera.Plastid DNA variation withinAustrostipawas low and only few lineages were resolved. Nuclear ITS andAcc1yielded comparable groupings of taxa and resolved subgeneraArbuscula,Petaurista,Bambusinain a common clade and as monophyletic. In summary, we suggest recognizing nine subgenera inAustrostipa.Because of its taxonomic significance in Stipeae, we studied the lemma epidermal structure in 34 representatives ofAustrostipa.In most species, the lemma epidermal pattern (LEP) was relatively uniform (maize-like LEP), but in six species it was more similar to that ofStipas.str.,Neotrinia,PtilagrostisandOrthoraphium.The species representing subgeneraLobatae,Petaurista,BambusinaandA. muellerifrom subg.Tuberculataewere well-separated from all the other species included in the analysis.Two different sequence copies ofAcc1were found in polyploidAustrostipaandAnemanthele. Each of the copy types formed a single clade. This was also true of the sampled species ofStipas.str., but their clades were strongly separated from those ofAustrostipaandAnemanthele. This underlines the statement of Tzvelev (1977) that most if not all contemporary Stipeae are of hybrid origin and demonstrates it for the first time unambiguously on the molecular level.Chromosome number variation is surveyed and reviewed for the whole tribe Stipeae and interpreted in a molecular phylogenetic framework. The rather coherent picture of chromosome number variation underlines the phylogenetic and evolutionary significance of this character.The closest extant relatives ofAustrostipaandAnemantheleare in the clade ofAchnatherums.str.,Celtica,OloptumandStipellula. These genera are most abundant in Central and Eastern Asia, which makes a colonization of Australian and New Zealand from this region more likely, perhaps via long-distance dispersal, than colonization of Australia from southern South America via Antarctica as previously invoked.Supporting Informationmay be found online in the Supporting Information section at the end of the article.

Karyotype analyses in species of the family Marantaceae (550 species, 31 genera) were conducted to shed light on the reported strong variation of chromosome number and size and the occurrence of polyploidy. Special attention was paid to the alterations in basic chromosome numbers, karyotypes and ploidy levels. Taxon sampling covered the whole distribution area of Marantaceae in Africa, Asia and America. We applied mitotic chromosome counting using conventional rapid squash techniques in 43 accessions (39 species, 16 genera), evaluated literature records for 51 species and conducted karyotype analyses. Eleven different somatic chromosome numbers were found (2n = 20, 22, 24, 26, 28, 33, 44, 36, 52, 65, 72). Based on the presumed basic chromosome numbers ofx = 9, 10, 11, 12, 13, 14, this may correspond to diploid, triploid, tetraploid, pentaploid and octoploid levels, respectively. Dysploid variation, polyploidy and, to a lesser extend, hybridization may be the main factors in chromosome number evolution of the family. Our results also point to a certain degree of association with species diversification and geographical patterns.

To investigate the evolutionary diversification and morphological evolution of grass supertribe Poodae (subfam. Pooideae, Poaceae) we conducted a comprehensive molecular phylogenetic analysis including representatives from most of their accepted genera. We focused on generating a DNA sequence dataset of plastid matK gene–3’trnK exon and trnL– trnF regions and nuclear ribosomal ITS1–5.8S gene–ITS2 and ETS that was taxonomically overlapping as completely as possible (altogether 257 species). The idea was to infer whether phylogenetic trees or certain clades based on plastid and nuclear DNA data correspond with each other or discord, revealing signatures of past hybridization. The datasets were analysed using maximum parsimony, maximum likelihood and Bayesian approaches. Instances of severe conflicts between the phylogenetic trees derived from both datasets, some of which have been noted earlier, unambiguously point to hybrid origin of several lineages (subtribes, groups of genera, sometimes genera) such as Phalaridinae, Scolochloinae, Sesleriinae, Torreyochloinae; Arctopoa, Castellia, Graphephorum, Hyalopodium, Lagurus, Macrobriza, Puccinellia plus Sclerochloa, Sesleria, Tricholemma, American Trisetum, etc. and presumably Airinae, Holcinae and Phleinae. ‘Calamagrostis’ flavens appears to be an intergeneric hybrid between Agrostis and Calamagrostis. Most frequently there is good agreement of other regions of the trees, apart from intrinsic different phylogenetic resolution of the respective DNA markers. To explore the to date rather unclear morphological evolution of our study group a data matrix encompassing finally 188 characters was analysed for ancestral state reconstructions (ASR) using the tree from the combined molecular dataset as presumably best approximation to the species phylogeny. For 74 characters ASRs were feasible and yielded partly surprising results for the study group as a whole but also for some of their subdivisions. Considering taxonomy and classification it became evident, that many morphological characters show a very high degree of homoplasy and are seemingly able to change within comparatively short timespans in the evolution of our grasses. Most of the taxonomic units distinguished within our study group, e.g. as subtribes, are defined less by consistent morphological characters or character combinations and should be rather understood as clades revealed by molecular phylogenetic analysis. One reason for this extreme homoplasy concerning traditionally highly rated characters of inflorescences or spikelets and their components might be that they have little to do with pollination (always wind) or adaptation to pollinators as in other angiosperms but rather with dispersal and diaspores. Easily changing structure of spikelet disarticulation, of glume, lemma or awn characters might be advantageous in the rapid adaptation to different habitats and micro-habitats, which was evidently most successfully accomplished by these grasses. A partly revised classification of Poodae is presented, including a re-instatement of tribes Aveneae and Poeae s.str. Following a comparatively narrow delineation of preferably monophyletic subtribes, Antinoriinae, Avenulinae, Brizochloinae, Helictochloinae, Hypseochloinae are described as new. New genera are Arctohyalopoa and Hyalopodium. New combinations are Arctohyalopoa lanatiflora, A. lanatiflora subsp. ivanoviae, A. lanatiflora subsp. momica, Colpodium biebersteinianum, C. kochii, C. trichopodum, C. verticillatum, Deschampsia micrathera, Dupontia fulva, Festuca masafuerana, Hyalopodium araraticum, Paracolpodium baltistanicum, Parapholis cylindrica, P. ×pauneroi. Festuca masatierrae is a new name.Supporting Information may be found online in the Supporting Information section at the end of the article.

We examined the molecular phylogeny and chromosomal features of European Helictotrichon species to explore the relationships within the genus and to investigate the origin of several polyploids. Using both approaches, molecular and cytogenetic, revealed the strong impact of allopolyploidization on genome organization from chromosome structure to sequence level. Our research focused on Mediterranean and endemic species of the Alps. Altogether, the molecular phylogenetic analyses include a sample of 17 Helictotrichon species and subspecies, used DNA sequences from the nuclear ribosomal (nr) internal transcribed spacer region (ITS) and the single copy gene topoisomerase 6 (Topo6), and were analysed by maximum parsimony and Bayesian methods. Karyotype structures were investigated by fluorescence in situ hybridization (FISH) and fluorochrome banding. Cytogenetic characters were mapped on the combined phylogenetic tree. The absence or comparatively rare occurrence of different ITS sequence types in some (allo-)...

Polyploidy is a fundamental mechanism in evolution, but is hard to detect in taxa with agmatoploidy or aneuploidy. We tested whether a combination of chromosome counting, microsatellite analyses and flow cytometric measurements represents a suitable approach for the detection of basic chromosome numbers and ploidy in Kobresia (Cyperaceae). Chromosome counting resulted in 2n = 64 for Kobresia pygmaea and K. cercostachys, 2n = 58 and 64 for K. myosuroides, and 2n = 72 for K. simpliciuscula. We characterized eight microsatellite loci for K. pygmaea, which gave a maximum of four alleles per individual. Cross-species amplification was tested in 26 congeneric species and, on average, six of eight loci amplified successfully. Using flow cytometry, we confirmed tetraploidy in K. pygmaea. Basic chromosome numbers and ploidy were inferred from chromosome counts and the maximum number of alleles per locus. We consider the basic numbers as x = 16 and 18, with irregularities derived from agmatoploidy and aneuploidy. Across all Kobresia taxa, ploidy ranged from diploid up to heptaploid. The combination of chromosome counts and microsatellite analyses is an ideal method for the determination of basic chromosome numbers and for inferring ploidy, and flow cytometry is a suitable tool for the identification of deviating cytotypes. (C) 2014 The Linnean Society of London

To study the origin and evolution of naturally occurring polyploids, we performed phylogenetic analyses of nuclear ribosomal DNA spacers combined with molecular cytogenetics in 55 accessions of 27 taxa of the oat genus Helictochloa. A complex pattern of reticulate evolution was revealed with many diploid species and extensive polyploidy up to 20x. Altogether 11 groups of internal transcribed spacer (ITS) sequences can be distinguished. Sequences from 1-3 different ITS lineages were detected in polyploids. Cytogenetic data allow reconstruction of 8 basic monoploid chromosome sets. Six of these genomes occur in different combinations in the polyploid species. Two genomes are only found in diploids. Our sequence and karyological data highlight the occurrence of autopolyploidy and allopolyploidy, provide new information about the evolutionary history of taxa, and allow a more accurate systematic treatment of the concerned species. The geographical distribution of the 11 ITS lineages distinguished is highly structured and points to an origin of the genus in western Asia, presumably in grasslands like steppes or mountain steppes and meadows. The evolutionary basal lineages are of Asian, Minor Asian and east Mediterranean distribution and are present also in North America. The western and central parts of the Mediterranean and northern Europe harbor the modern lineages.

Molecular cytogenetic and phylogenetic analysis of alpine endemic wild oats of genus Helictotrichon represents a remarkable example of speciation and diversification through homoploid hybridisation and polyploidisation. Results suggest a primary centre of species establishment in the eastern regions of the Alps, with the westward expansion and subsequent ice age interruption resulting in a recently disjunct distribution between populations of the southwestern and southeastern Alps., Hybridization and polyploidization can radically impact genome organization from sequence level to chromosome structure. As a result, often in response to environmental change and species isolation, the development of novel traits can arise and will tend to result in the formation of homoploid or polyploid hybrid species. In this study we focus on evidence of hybridization and polyploidization by ascertaining the species parentage of the endemic alpine Helictotrichon parlatorei group. This group comprises five taxa; the diploids H. parlatorei, Helictotrichon setaceum subsp. setaceum and subsp. petzense, their putative hybrid Helictotrichon ×krischae and the hexaploid Helictotrichon sempervirens. For molecular analyses, cloned nuclear Topoisomerase VI genes of H. sempervirens and H. ×krischae were sequenced and compared with sequences of the diploids to estimate the evolutionary history in this group. In addition, detailed chromosome studies were carried out including fluorescence in situ hybridization (FISH) with 5S and 45S ribosomal and satellite DNA probes, and fluorochrome staining with chromomycin and DAPI. Two distinct types of Topoisomerase VI sequences were identified. One of them (SET) occurs in both subspecies of H. setaceum, the other (PAR) in H. parlatorei. Both types were found in H. ×krischae and H. sempervirens. Karyotypes of H. parlatorei and H. setaceum could be distinguished by chromosomes with a clearly differentiated banding pattern of ribosomal DNAs. Both patterns occurred in the hybrid H. ×krischae. Hexaploid H. sempervirens shares karyotype features with diploid H. parlatorei, but lacks the expected chromosome characteristics of H. setaceum, possibly an example of beginning diploidization after polyploidization. The geographic origin of the putative parental species and their hybrids and the possible biogeographical spread through the Alps are discussed.

Polyploidy belongs to the most striking factors in plant evolution. To address the role of allo- versus autopolyploid speciation in natural polyploids, we studied species of the oatlike genus Avenula, which contains diploids and polyploids with up to 22x valence. We conducted DNA sequence analyses of plasmid-cloned ITS repeats of nuclear ribosomal (nr) 35S DNA, complemented by cytogenetic studies including fluorescence in situ hybridization (FISH) with nr and satellite (sat) DNAs in 12–18x polyploid species from SE Europe and Asia Minor. Altogether, four different ITS repeat types are involved in their parentage. One is confined to Avenula armeniaca and the second shared between A. armeniaca and Avenula blaui, none of which is known from extant diploid species. The latter repeat type is characteristic of A. blaui but prevails also in one of the A. armeniaca accessions, as a result of hybridization and/or genetic introgression with an ongoing process of sequence change in favor of A. blaui repeats. The two...

The small pooid grass tribe Hainardieae comprises six genera with approximately ten species; however, this tribe was not accepted by all previous taxonomic treatments. To study the relationships among these genera and to infer the phylogeny and evolutionary patterns, we used sequence variation of the internal transcribed spacers (ITS) of nuclear ribosomal and chloroplast (cp) matK DNA and morphology. Many genera of the Aveneae/Poeae tribe complex additionally were included. Both molecular datasets showed Hainardieae to be highly polyphyletic, and its genera to branch with different groups of the Aveneae/Poeae. Parapholis and Hainardia are corroborated as being closely related, and belonging to a firmly supported Eurasian clade together with Catapodium incl. Scleropoa, Cutandia, Desmazeria, Sphenopus, Vulpiella (subtribe Parapholiinae) and with Cynosurus as sister to this assemblage. The other genera of traditionally recognised Hainardieae are positioned phylogenetically distant: Mediterranean Narduroides is verified as more or less related to Festuca and relatives (subtribe Loliinae), whereas the west Eurasian Pholiurus is close to the lineage of Poa and relatives (subtribe Poinae). North American Scribneria is sister to Deschampsia and both genera should be unified under a common subtribe (Aristaveninae or Holcinae). The phylogenetic position of the Algerian genus Agropyropsis (close to Narduroides and within the Loliinae) is suggested on morphology only, because no molecular data was obtained for it. Considering classification, we support the abandonment of tribe Hainardieae and argue to abandon Poeae subtribe Scribneriinae. Poeae subtribe Parapholiinae is redefined with a novel genus content, due to the exclusion of Agropyropsis and Pholiurus and the inclusion of Vulpiella.

The fragrant orchid Gymnadenia conopsea s.l. is a controversial taxon with two commonly distinguished species, G. conopsea s.str. and G. densiflora. Despite morphological similarity, differentiation between the taxa has been reported for several characters; however, character variation within taxa has obviated a clear consensus. We assessed ITS sequences, microsatellite variation and chromosome numbers on the European scale (1,420 samples) and conducted morphological analyses for 626 samples from Germany. ITS analysis revealed a 2% nucleotide divergence between the taxa, similar to the divergence between other Gymnadenia species. The ITS sequences of G. densiflora form a well-supported monophyletic group sharing a most recent common ancestor with G. nigra and G. austriaca. Thus, G. conopsea and G. densiflora are not sister species, and a species rank is supported for G. densiflora (Wahlenb.) Dietrich and G. conopsea (L.) R.Br. s.str. This was confirmed by the microsatellite analysis, which revealed a strong genetic differentiation between the taxa because of largely non-overlapping sets of alleles. Chromosome numbers showed that G. conopsea was either diploid or tetraploid, whereas G. densiflora was diploid throughout. Morphologically, the taxa differed significantly in the mean value of a number of diagnostic characters. However, a discriminant analysis showed that the morphological variability is substantial, and on the individual level an unequivocal assignment is not possible as 96% of G. conopsea, but only 77% of G. densiflora could be assigned correctly. Further studies are needed on character variation within and among species and ploidy levels to allow for a better identification of the genetically differentiated but morphologically similar taxa.

The phylogeny of Pooideae, one of the largest subfamilies of grasses, has been intensively studied during the past years. To investigate the early evolutionary splits in Pooideae we used a broad sample of genera with uncertain placement, some of which have not been studied in molecular phylogenetics before, complemented by representatives from other lineages of this subfamily. Morphological, cytogenetic and biogeographical analyses were added to the molecular sequence work on chloroplast matK–3’trnK and nuclear ITS. According to chloroplast DNA data, a new and well-supported lineage was identified among the early branches. It consisted of Phaenosperma and a larger group of genera encompassing Anisopogon, Danthoniastrum, Duthiea, Metcalfia, Pseudodanthonia (inclusion resting on ITS and morphology), Sinochasea and Stephanachne. Based on structural characters we suggest to keep Phaenosperma under the monotypic tribe Phaenospermateae and to accommodate the other genera under a new tribe Duthieeae, which is mo...

Aim The Aegean is a hotspot of plant biodiversity, with its island biota harbouring a large number of endemic taxa. To investigate the relationship between biogeography, polyploid speciation and genomics in the Aegean we used the biogeographically isolated highly polyploid eastern Mediterranean grass species Avenula agropyroides (2n = 70) as an example of complicated polyploid origin. Location Mediterranean, Aegean. Methods To clarify the origin of A. agropyroides, we conducted chromosome studies using repetitive DNAs as hybridization probes in fluorescent in situ hybridization experiments, chromosome banding methods and DNA sequence analyses of plasmid-cloned nuclear ribosomal (nr) ITS1–5.8S–ITS2 DNA. Results Decaploid A. agropyroides had near-autopolyploid karyotype structure and contained characteristic sequence motifs of nrDNA repeats not encountered in any of the diploids studied. Special repeat types found in one of its accessions (Crete) showed that A. agropyroides originated from a diploid species with a hybrid background. One of the genomes involved was close to both that of extant species (Avenula aetolica, Avenula compressa, Avenula hookeri, Avenula schelliana, Avenula versicolor) distributed mostly in the eastern Mediterranean to Asia and North America and also to the west Mediterranean (Avenula bromoides). The other resembled that of exclusively western Mediterranean species (Avenula albinervis, Avenula levis, Avenula marginata, Avenula sulcata). Main conclusions Avenula agropyroides represents a remarkable polyploid in the eastern Mediterranean, conserving the genome structure of a diploid species that no longer exists. This highlights how the Aegean has been less affected than other Eurasian regions by the repeated shifts of climatic zones and vegetation belts since the Late Tertiary.

Molecular and molecular‐cytogenetic studies reveal that allopolyploidisation can dramatically impact genome organisation from sequence level to chromosome structure. To clarify the origin of polyploids in the Mediterranean Helictotrichon bromoides species complex (Poaceae, grass family) detailed chromosome studies were carried out including fluorescence in situ hybridisation with different repetitive DNA probes and various types of chromosome staining. Cloned nuclear ribosomal ITS1–5.8S‐ITS2 repeats were sequenced to estimate their molecular diversity in diploids and polyploids. The results concordantly suggest that 2× H. bromoides is one genome donor of all polyploids. Two further genomes were involved in their origin. The polyploids show unidirectional homogenisation of rDNA consistently at the cost of repeats from the H. bromoides genome. Frequent occurrence of mosaic and chimerical sequences points to slow sequence homogenisation. Parental chromosomal sites of nucleolar organisers are maintai...

Karyotype structures revealed by in situ hybridization with ribosomal and satellite DNAs and fluorochrome staining of AT- or GC-rich regions are reported for 23 diploid to tetraploid taxa of Aveneae genera Arrhenatherum , Avena , Helictotrichon , and Pseudarrhenatherum . Chromosomal features are compared with a molecular phylogeny generated on nuclear ribosomal (ITS, 5S) and chloroplast (matK) DNA sequences. Ancestral chromosomal character states are (1) two satellite chromosomes per set of x = 7, (2) 5S rDNA localized in nonsatellite chromosomes, (3) large chromosomes with (4) rather equal lengths of their respective chromosome arms, (5) sets with strong variance of chromosome lengths, (6) absence or small amounts of heterochromatin, and (7) absence or no detectable amplification of the satellite DNAs tested. Overall, most karyotype characteristics are species specific, but common patterns were found for the species of two large subgenera of Helictotrichon. Pseudarrhenatherum, although nested in the molecular phylogeny within Helictotrichon subgenus Helictotrichon, deviates strongly in karyotype characters such as Arrhenatherum as sister of Avena. The karyotype of Helictotrichon jahandiezii , sister to the clade of Helictotrichon subgenera Helictotrichon, Avena, and Arrhenatherum, strongly resembles that of Avena macrostachya . Karyotype features suggest that perennial A. macrostachya and H. jahandiezii are close to the C-genome species of annual Avena, whereas the Avena A genome resembles that of Arrhenatherum.

The chromosomal loci of 5S and 45S ribosomal DNAs (rDNAs) and the activity of nucleolar-organizing regions (NORs) were analysed in perennial oats of the genera Ammophila, Amphibromus, Arrhenatherum, Avena, Deschampsia, and Helictotrichon s.l. (Poaceae: Aveneae) using fluorescence in situ hybridization, staining with chromomycin/4′,6-diamidino-2-phenylindole (DAPI), and silver impregnation. All chromosomes with a secondary constriction were nucleolar active. In chromosomes without a secondary constriction, NORs corresponded exclusively to broad bands of 45S rDNA with chromomycin-positive, DAPI-negative, and silver-positive stainability. Additional minor bands of 45S rDNA showed no nucleolar activity. 5S rDNA was localized mostly in loci different from the nucleolar-active 45S rDNA. If both rDNAs occurred within the same chromosome, they were at largely corresponding distances from the centromere, irrespective of their particular localization in either the same chromosome arm or in opposite arms. In the latter case, 5S rDNA was never more distal to the centromere than 45S rDNA. A new model was devised to explain this non-random distribution of both rDNAs in nucleolar-organizing chromosomes, which identified the Rabl orientation of chromosomes as ensuring a spatial proximity of 5S to 45S rDNA in interphase nuclei, even if they were localized in opposite arms. The possible role of the Rabl orientation in determining the spread and accumulation of 5S rDNA sequences in further chromosomes of the genome was discussed. B chromosomes were devoid of 5S rDNA, but most contained 45S rDNA and were nucleolar active. In some large groups of species, the number and arrangement of 5S and 45S rDNA sites in the chromosomes were remarkably uniform, especially in Helictotrichon subgenus Helictotrichon and Helictotrichon subgenus Pratavenastrum. Such distribution patterns have survived many speciation processes and have also remained widely unchanged in polyploids. © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society, 2007, 155, 193–210.

The physical mapping of three abundant tandemly repeated DNA sequences, CON1, CON2, and COM2, and the distributional pattern of AT- and GC-rich regions in the chromosomes of 32 species of the grass family Poaceae have been established by means of fluorescence in situ hybridization and fluorochrome banding with chromomycin and DAPI. Additionally, locations of 5S, 35S rDNA, and the C-banding pattern were examined. All satellite DNAs (satDNA) tested are situated predominantly subtelomerically in the chromosomes, but occur also colocalized with 35S and 5S ribosomal DNAs (rDNA). Especially, CON2 is most often colocalized with the 5S rDNA, but is evolutionarily not derived from it. Subtelomeric heterochromatin bands are frequently, but not always correlated with satDNA bands. Moreover, the DAPI- or rarely chromomycin-positive stainability of heterochromatin is not caused by these satDNAs as revealed by their sequence organization, showing too few clusters of AT or GC base pairs as required for binding of the fluorochromes. The occurrence of satDNAs is not correlated with that of other components of the heterochromatin. Proportions of satDNAs and other sequences of the heterochromatin relative to the entire genome appear subjected to a much faster evolutionary change than the rather stable proportions of the rDNAs. Heteromorphism in banding patterns found in many species is related in most instances with breeding system and life form. The independent evolution and amplification of different satDNAs is discussed in relation to molecular phylogenetic data. The value and limitations of satDNA data in addressing systematic questions in grasses is exemplified for several grass subfamilies and tribes.

5S rDNA repeats studied in five genera of Aveneae have lengths between 285 and 329 bp (Avena sativa, Avena macrostachya, 26 species of Helictotrichon, Pseudarrhenatherum longifolium, Lagurus ovatus, and Trisetum spicatum). In only a single species (Helictotrichon aetolicum) an additional repeat of 456 bp occurs infrequently. Variation is largely due to insertions or deletions in the nontranscribed spacer as determined from sequences of 163 independent clones. The 5S gene of the Aveneae studied is conserved in length and sequence except for Helictotrichon bromoides and Helictotrichon marginatum in which duplications occur at two different sites. This new type of duplication and all duplications reported to date in 5S genes of angiosperms are shown to center on defined palindromic sequences. The “uncommon” 5S gene sequences detected in some Aveneae are not necessarily nonfunctional as pseudogenes because the essential features of the internal control region are maintained even after such duplication events. In each instance such gene sequences have spacers with unmodified structure, indicating that change in gene sequence is not necessarily coupled with change in adjacent spacers. The value of 5S spacer sequences for genomic identifications in Aveneae is exemplified in A. macrostachya (perennial), A. sativa (annual), and several diploid taxa of the genus Helictotrichon.

Mitotic metaphase chromosomes were counted in 29 taxa, representing 11 subgenera of Austrostipa, and in 11 species from nine related genera of the grass subfamily Pooideae. Karyotype features were also measured. The cytogenetic data were mapped on molecular phylogenetic trees based on nuclear ITS and plastid 3ʹtrnK DNA sequence data. The trees showed four different main lineages within Austrostipa, but supported only two of the 13 acknowledged subgenera. The phylogenetic positions of the genera Anemanthele, Achnatherum, Nassella and Oloptum indicated paraphyly of the genus Austrostipa. In nuclear-sequence data, Anemanthele was nested within Austrostipa; however, in plastid-sequence data, both were sisters. The newly obtained chromosome counts in Austrostipa showed that most species have 2n = 44, the other 2n = 66. Presuming a chromosome base number of x = 11, the counts corresponded with ploidy levels of 4x and 6x respectively. Karyotype data of Austrostipa and Anemanthele were very similar. Chromosome counting in further genera suggested chromosome base numbers of x = 9, 10, 11, 12 and 13. Chromosome sizes of the phylogenetically derived tribe Stipeae were smaller than those of the earliest diverging Pooideae lineages Nardeae, Meliceae and Phaenospermateae. The mechanisms of chromosome evolution and the origin of the considerable variation in chromosome base numbers in the subfamily Pooideae are discussed in the context of chromosome evolution and biosystematics.