Cytotypes 2n Research Articles

Evolution and taxonomic split of the model grass Brachypodium distachyon

Brachypodium distachyon is being widely investigated across the world as a model plant for temperate cereals. This annual plant has three cytotypes (2n = 10, 20, 30) that are still regarded as part of a single species. Here, a multidisciplinary study has been conducted on a representative sampling of the three cytotypes to investigate their evolutionary relationships and origins, and to elucidate if they represent separate species. Statistical analyses of 15 selected phenotypic traits were conducted in individuals from 36 lines or populations. Cytogenetic analyses were performed through flow cytometry, fluorescence in situ hybridization (FISH) with genomic (GISH) and multiple DNA sequences as probes, and comparative chromosome painting (CCP). Phylogenetic analyses were based on two plastid (ndhF, trnLF) and five nuclear (ITS, ETS, CAL, DGAT, GI) genes from different Brachypodium lineages, whose divergence times and evolutionary rates were estimated. The phenotypic analyses detected significant differences between the three cytotypes and demonstrated stability of characters in natural populations. Genome size estimations, GISH, FISH and CCP confirmed that the 2n = 10 and 2n = 20 cytotypes represent two different diploid taxa, whereas the 2n = 30 cytotype represents the allotetraploid derived from them. Phylogenetic analysis demonstrated that the 2n = 20 and 2n = 10 cytotypes emerged from two independent lineages that were, respectively, the maternal and paternal genome donors of the 2n = 30 cytotype. The 2n = 20 lineage was older and mutated significantly faster than the 2n = 10 lineage and all the core perennial Brachypodium species. The substantial phenotypic, cytogenetic and molecular differences detected among the three B. distachyon sensu lato cytotypes are indicative of major speciation processes within this complex that allow their taxonomic separation into three distinct species. We have kept the name B. distachyon for the 2n = 10 cytotype and have described two novel species as B. stacei and B. hybridum for, respectively, the 2n = 20 and 2n = 30 cytotypes.

Comparative micropropagation efficiency of diploid and triploid mulberry (Morus alba cv. S1) from axillary bud explants

Micropropagation ability of two cytotypes (2n = 2x = 28 and 2n = 3x = 42) of mulberry (variety S 1) was tested from axillary buds through organogenesis. Both shoot and rootlets development periods varied considerably with ploidy variations. The triploid shoots generally grew more vigorously in Murashige and Skoog (MS) medium fortified with 6-benzyl amino purine (6-BAP) than those of diploids. Maximum shoot initiation frequency (80%) was obtained with 4.4 µM of 6-BAP on 4.2 days of culture in triploid; whereas, the axillary buds sprouted within 3.5 days with 100% shoot initiation frequency in diploid cultures. Highest shoot length (4.8 and 5.6 cm per explant) was obtained at 8.8 and 4.4 µM 6-BAP supplementations in diploid and triploid cytotypes, respectively. Subsequently, regenerated shoots were transferred to auxin rich rooting media supplemented with either the different doses of indole acetic acid (IAA) or naphthalene acetic acid (NAA). Root initiation was more vigorous in diploid than triploids with both the tested growth regulators. Maximum number of rootlets per shoot (15) and root length (4.2 cm) were observed in MS basal medium supplemented with 4.0 µM NAA after 21 days of culture of diploid plants; while in triploid cytotype, maximum rootlets per shoot (8.3) were noticed with 4.4 µM NAA after 21 days of culture. Rooted plantlets were hardened in plastic cups containing sterile sand and soil mix (1:1; w/w) for 21 days and subsequently transferred to clay pots (l x b x h: 12 x 12 x 12 cm) in shade with a survival of 65 and 52% for diploid and triploid cytotypes, respectively. The time required for field establishment of micro-propagated triploid was about 60 days.

Effect of secondary associations on meiosis, pollen fertility and pollen size in cape gooseberry (Physalis peruviana L.)

This study deals with the detailed analysis on various meiotic abnormalities in the tetraploid cytotype (2n=4x=48) of Physalis peruviana L. The meiotic abnormalities include secondary associations of bivalents, stickiness of chromosomes, multivalents and univalents, and unoriented bivalents during metaphase-I, non-synchronization in the separation of some bivalents, laggards, chromatin bridges and cytomixis at various meiotic stages besides aberrant microsporogenesis. In spite of all these abnormalities, distribution of chromosomes at anaphases found to be normal. Microsporogenesis includes monads, dyads and tetrads with micronuclei besides normal tetrads, consequently reducing the pollen fertility (76%).

Polyploidy and new chromosome counts in Anaphalis (Asteraceae: Gnaphalieae) from the Qinghai‐Tibet Plateau of China

Abstract Anaphalis is one of the largest genera of the Asian Gnaphalieae (Asteraceae) and is most diversified on the Qinghai‐Tibet Plateau. The chromosome numbers and karyomorphology of six species from seven populations were investigated for the first time for this region. Chromosome numbers have been newly documented for four species: Anaphalis deserti (2n = 56 = 24 median [m]+ 24 submedian [sm]+ 8 acrocentric [st]); Anaphalis plicata (2n = 56 = 26m + 30sm); Anaphalis xylorhiza (2n = 28 = 2 median point [M]+ 14m + 12sm); and Anaphalis rhododactyla (2n = 56 = 32m + 24sm). Two further counts are in agreement with the previously reported numbers, that is, Anaphalis royleana (2n = 28 = 4M + 6m + 18sm) and Anaphalis margaritacea (2n = 28 = 12m + 16sm). A new polyploid cytotype (2n = 56 = 26m + 30sm) was found in the Zougong population of A. margaritacea. Polyploidy is for the first time reported for Anaphalis, with four out of seven counts being tetraploid. Our cytological results suggest that polyploids might have played an important role in the evolution of Anaphalis on the Qinghai‐Tibet Plateau.

Mitochondrial divergence between three cytotypes of the Anatolian Mole Rat, Nannospalax xanthodon (Nordmann, 1840)

The Blind Mole Rats of Anatolia (Nannospalax xanthodon (Nordmann, 1840)) are characterised by prolific chromosomal diversification. While the geographic distribution of various cytotypes is well documented, opinions on their taxonomic ranking varies amongst authorities. A partial sequence (630 bp) of mitochondrial cytochrome b gene in 13 Blind Mole Rats from the Konya basin, central Anatolia, which represented three distinct cytotypes (2n=40, 58, and 60) yielded nine cyt b haplotypes. Phylogenetic reconstructions recognized three well supported lineages which matched diploid number counts. Genetic divergences between cytotypes were high (K2P between 8.16% ± 1.19 and 11.33% ± 1.42) and application of the 2% divergence rate to the net divergence estimates suggests their divergence about 3.84 and 5.43 Mya (95% confidence interval=1.53–8.19 Mya). If one would rely on genetic operational criteria in species delimitation, there would be little doubt that the three Nannospalax cytotypes analysed in this study belong to distinct allopatric species. Before translating the results into formal taxonomy, more genetic information should be acquired on different Nannospalax cytotypes occupying the eastern Mediterranean.

Cytotaxonomy in distinct populations of Hoplias aff. malabaricus (Characiformes, Erythrinidae) from lower Paranapanema River basin

Cytogenetic and morphometric analyses were carried out in Hoplias aff. malabaricus specimens from six distinct populations from the lower Paranapanema River basin, located between the states of Paraná and São Paulo, Brazil. Measurements were also taken from a specimen collected in Surinam. In a population from a fish farm station at Universidade do Norte do Parana (EPUNOPAR), two sympatric cytotypes (2n = 40 and 2n = 42 chromosomes) are found. A population from a fish farm station at Universidade Estadual de Londrina (EPUEL) shows 2n = 42 meta-submetacentric chromosomes for males and females with a simple sex chromosome system of XX/XY type. Populations from the Vermelho and Rancho Alegre Rivers, Três Bocas Stream and Paranapanema River have 2n = 39 chromosomes in males and 2n = 40 chromosomes in females, showing a multiple sex chromosome system of X(1)X(1)X(2)X(2)/X(1)X(2)Y type. Twenty morphological variables were studied. These measurements were used for an analysis of the canonical variables and standard analysis of proportional measurements. The most variable measurements among the specimens are the maxilla length (MXL) and the pre-dorsal distance (PDD). Analysis of canonical variables indicates three distinct groups in the first canonical axis formed by: (1) Três Bocas Stream, (2) Rancho Alegre + Vermelho River + EPUNOPAR and (3) EPUEL + Paranapanema River. This axis retained 79.4% of information from the original matrix. Analysis of morphometrics reveals differences among populations from the Paranapanema River basin and between these and the specimen from Surinam. The morphometric and cytogenetic differences among the studied populations suggest a species complex.

Cytotype-specific ISSR profiles and karyotypes in the Neotropical genus Eigenmannia (Teleostei: Gymnotiformes)

The genus Eigenmannia (Teleostei: Gymnotiformes), a widely distributed fish genus from the Neotropical region, presents very complex morphological patterns and many taxonomic problems. It is suggested that this genus harbors a species complex that is hard to differentiate using only morphological characteristics. As a result, many species of Eigenmannia may be currently gathered under a common name. With the objective of providing new tools for species characterization in this group, an analysis of the polymorphism of DNA inter-simple sequence repeats (ISSR), obtained by single primer amplification reaction (SPAR), combined with karyotype identification, was carried out in specimens sampled from populations of the Upper Paraná, São Francisco and Amazon river basins (Brazil). Specific ISSR patterns generated by primers (AAGC)(4) and (GGAC)(4) were found to characterize the ten cytotypes analyzed, even though the cytotypes 2n = 38 and 2n = 38 XX:XY, from the Upper Paraná basin, share some ISSR amplification patterns. The geographical distribution of all Eigenmannia specimens sampled was inferred, showing the cytotype 2n = 31/2n = 32 as the most frequent and largely distributed in the Upper Paraná basin. The cytotype 2n = 34 was reported for the first time in the genus Eigenmania, restricted to the São Francisco basin. Polymorphic ISSR patterns were also detected for each cytotype. Considering our results and the data reported previously in the literature, it is suggested that many of the forms of Eigenmannia herein analyzed might be regarded as different species. This work reinforces the importance of employing diverse approaches, such as molecular and cytogenetic characterization, to address taxonomic and evolutionary issues.

Genome size in Hieracium subgenus Hieracium (Asteraceae) is strongly correlated with major phylogenetic groups.

Hieracium subgenus Hieracium is one of the taxonomically most intricate groups of vascular plants, due to polyploidy and a diversity of breeeding systems (sexuality vs. apomixis). The aim of the present study was to analyse nuclear genome size in a phylogenetic framework and to assess relationships between genome size and ploidy, breeding system and selected ecogeographic features. Holoploid and monoploid genome sizes (C- and Cx-values) of 215 cultivated plants from 89 field populations of 42 so-called 'basic' Hieracium species were determined using propidium iodide flow cytometry. Chromosome counts were available for all analysed plants, and all plants were tested experimentally for their mode of reproduction (sexuality vs. apomixis). For constructing molecular phylogenetic trees, the external transcribed spacer region of nuclear ribosomal DNA was used. The mean 2C values differed up to 2.37-fold among different species (from 7.03 pg in diploid to 16.67 in tetraploid accessions). The 1Cx values varied 1.22-fold (between 3.51 and 4.34 pg). Variation in 1Cx values between conspecific (species in a broad sense) accessions ranged from 0.24% to 7.2%. Little variation (not exceeding the approximate measurement inaccurracy threshold of 3.5%) was found in 33 species, whereas variation higher than 3.5% was detected in seven species. Most of the latter may have a polytopic origin. Mean 1Cx values of the three cytotypes (2n, 3n and 4n) differed significantly (average of 3.93 pg in diploids, 3.82 pg in triploids and 3.78 pg in tetraploids) indicating downsizing of genomes in polyploids. The pattern of genome size variation correlated well with two major phylogenetic clades which were composed of species with western or eastern European origin. The monoploid genome size in the 'western' species was significantly lower than in the 'eastern' ones. Correlation of genome size with latitude, altitude and selected ecological characters (light and temperature) was not significant. A longitudinal component was only apparent for the whole data set, but absent within the major lineages. Phylogeny was the most important factor explaining the pattern of genome size variation in Hieracium sensu stricto, species of western European origin having significantly lower genome size in comparison with those of eastern European origin. Any correlation with ecogeographic variables, including longitude, was outweighed by the divergence of the genus into two major phylogenetic lineages.

Chromatin Transfer during Male Meiosis Resulted into Heterogeneous Sized Pollen Grains in Anemone rivularis Buch.-Ham. ex DC. from Indian Cold Deserts

Presently, detailed cytological investigations have been carried out in 4 accessions of Anemone rivularis Buch.-Ham. ex DC, collected from the cold deserts of Lahaul-Spiti, Kinnaur, and Kullu districts of Himachal Pradesh (India). The phenomenon of cytomixis involving chromatin transfer among proximate pollen mother cells (PMCs) during male meiosis is recorded for the first time in the species. The effects of cytomixis on meiosis and pollen grains have also been discussed. In spite of the existence of intraspecific aneuploid and polyploid cytotypes (2n=14, 16, 24, 28, 48), all the accessions of the species unequivocally share the same diploid chromosome number, 2n=16. The accession studied from Kothi (Kullu) shows perfectly normal meiotic behaviour, cent per cent pollen fertility and uniform sized pollen grains. However, the accessions analyzed from Keylong and Kishori (Lahaul-Spiti) and Sangla (Kinnaur) show the phenomenon of cytomixis involving chromatin transfer among proximate PMCs, and associated meiotic abnormalities like chromosome stickiness, laggards and bridges at anaphase/telophase, micronuclei, some pollen malformation and pollen grains of heterogeneous sizes.

Proteins polymorphism of some populations of Lygeum spartum L. in Algeria

Lygeum spartum L. represent a natural barrier in the Algerian high plateaus against the advances of sand and turning into a desert. This species has two levels of ploA¯dy (diploA¯d cytotype 2n = 16 and polyploidy cytotype 2n = 40). Protein profile of several populations of this species have inter and intra specific variability. The polymorphic bands observed in the intermediate and slow zone have a molecular weight (MW) of 25.6, 30.1, 31.2, 37.3, 40.4, 69.3 and 82.7 kDa. This polymorphism exists not only between the polyploids samples (well 1 to 7) and diploids (well 8 and 9), but also inside the polyploids populations. These results showed that modifications of the electrophoretic profile of Lygeum spartum were concomitant with climatic and geographical external factors.

DISTRIBUTION AND GEOGRAPHIC LIMITS OF THE ALTERNATIVE CYTOTYPES OF TWO MICROTUS VOLES IN EUROPEAN RUSSIA

Chromosome data on the distributional limits of Microtus voles (M. subterraneus, M. arvalis) in the very east of Europe are presented. Wide border space reported formerly between the two subterraneus cytotypes (2n=54, 2n=52) as well as between the common vole cytotypes (arvalis and obscurus, both 2n=46) have been narrowed with the study progress, especially in the case of the common vole. For the first time, hybrid karyotypes were observed in a local sample, providing evidence of natural hybridization in the arvalis - obscurus contact zone.

Recent Natural Hybridization between Two Allopolyploid Wheatgrasses (Elytrigia, Poaceae): Ecological and Evolutionary Implications

Natural hybridization was investigated between two predominantly allohexaploid wheatgrasses, weedy Elytrigia repens and steppic E. intermedia, with respect to habitats characterized by different degrees of anthropogenic disturbance. Using flow cytometry (relative DNA content), 269 plants from three localities were analysed. Hybrids were further analysed using nuclear ribosomal (ITS1-5.8S-ITS2 region) and chloroplast (trnT-F region) DNA markers in addition to absolute DNA content and chromosome numbers. Weedy E. repens was rare in a steppic locality whereas E. intermedia was almost absent at two sites of agricultural land-use. Nevertheless, hybrids were common there whereas none were found at the steppic locality, underlining the importance of different ecological conditions for hybrid formation or establishment. At one highly disturbed site, > 16 % of randomly collected plants were hybrids. Hexaploid hybrids showed intermediate genome size compared with the parents and additive patterns of parental ITS copies. Some evidence of backcrosses was found. The direction of hybridization was highly asymmetric as cpDNA identified E. intermedia as the maternal parent in 61 out of 63 cases. Out of nine nonaploid cytotypes (2n = 9x = 63) which likely originated by fusion of unreduced and reduced gametes of hexaploids, eight were hybrids whereas one was a nonaploid cytotype of E. repens. The progeny of one nonaploid hybrid demonstrated gene flow between hexaploid and nonaploid cytotypes. The results show that E. repens and E. intermedia frequently cross at places where they co-occur. Hybrid frequency is likely influenced by habitat type; sites disturbed by human influence sustain hybrid formation and/or establishment. Hexaploid and nonaploid hybrid fertility is not negligible, backcrossing is possible, and the progeny is variable. The frequent production of new at least partially fertile cyto- and genotypes provides ample raw material for evolution and adaptation.

Crossability and Characterization of Interspecific Hybrids between Sexual Pennisetum glaucum (Pearl Millet) and a New Cytotype (2n=56) of Apomictic P. squamulatum

Pennisetum squamulatum is an important species belonging to tertiary gene pool of cultivated pearl millet as potential donor of several genes. Recently a new cytotype with 2n=56 chromosmes has been identified. Crossability of this cytotype has been studied with diploid and induced tetraploid pearl millet. The hybrids produced with this novel cytotype were compared for their characteristics with the hybrids previously reported with widely reported 2n=54 P. squamulatum cytotypes. Strong incompatability barriers were observed between 2n=56 cytotype with diploid pearl millet, and hybrids could not be obtained even after embryo rescue. Limited crossability was obtained with tetraploid pearl millet and 2 successful hybrids were produced. Their hybridity was confirmed by morphology, flowcytometry and cytology. The hybrids were highly fertile, perennial and segregated for mode of reproduction. Segregation for other traits confirmed heterozygous nature of P. squamulatum 2n=56 cytotype. Cytological investigations suggested 2n=8x nature of this cytotype. Successful hybridization between pearl millet and this new cytotype shall be important for introgression of useful traits as well as to study inheritance of traits such as perenniality, apomixis and tolerance to stresses.

Somatic embryogenesis and plant regeneration in diploid and triploid Arachis pintoi

Plants of two cytotypes (2n=2x=20, and 2n=3x=30) of pinto peanut (Arachis pintoi Krapov. & W.C. Gregory) were regenerated through somatic embryogenesis. Embryogenic calli were induced from shoot tips or immature leaves dissected from in vitro growing plants. In the case of the diploid peanut the best somatic embryogenesis was achieved when shoot tips were cultured on Murashige and Skoog (MS) medium supplemented with 10 mg dm-3 Picloram (PIC) and 0.1 mg dm-3 6-benzylaminopurine (BAP) or when explants from immature leaves were cultured on MS + 10 mg dm-3 PIC + 0.01 mg dm-3 BAP. In the case of triploid peanut the highest number of somatic embryos was obtained when shoot tips were cultured on MS + 10 mg dm-3 PIC + 0.01 mg dm-3 BAP or when immature leaves were cultured on MS + 20 mg dm-3 PIC + 0.01 mg dm-3 BAP. Somatic embryos were converted into plants by culture on MS + 0.01 mg dm-3 naphthaleneacetic acid + 0.01 mg dm-3 BAP. Plants were successfully transferred to pots in greenhouse.

Chromosome polymorphism in Astyanax fasciatus (Teleostei, Characidae). 1. Karyotype analysis, Ag-NORs and mapping of the 18S and 5S ribosomal genes in sympatric karyotypes and their possible hybrid forms

Astyanax fasciatus may be characterized as a chromosomally diversified ‘species’ presenting distinct cytotypes, each with its specific variants. The sympatric and syntopic occurrence of different cytotypes reinforces the hypothesis in which A. fasciatus may represent a group of species currently placed under a single common designation. Specimens from three collection points spread along the Mogi-Guaçu River in southeast Brazil were examined in the present work: (1) near its headwaters (Ouro Fino – MG), (2) in the middle region of the river (Cachoeira de Emas, Pirassunun ga – SP) and (3) close to its confluence with the Pardo River (Barrinha – SP). The 2n = 48 chromosomes cytotype was found in all sampling points, while cytotype 2n = 46 was only encountered in Barrinha and Cachoeira de Emas. In the latter locality, cytotype 2n = 46 predominated; nevertheless, other karyotype forms with 2n = 45 and 47 chromosomes also occurred, besides a structural variant of cytotype 2n = 46. One specimen with 2n = 47 chromosomes was also found in Ouro Fino. The Ag-NOR analysis, as well as the location of the 18S and 5S ribosomal genes, were conserved in all cytotypes. The data indicate that the variant karyotypes are a consequence of interbreeding between the standard cytotypes (2n = 46 and 48) and/or its descendants. This suggests a karyotype plasticity for this species, where at least a few variant karyotypes would not have deleterious effects on their bearers.

Esterase-D and chromosome patterns in Central Amazon piranha (Serrasalmus rhombeus Linnaeus, 1766) from Lake Catalão

This study presents additional genetic data on piranha (Serrasalmus rhombeus Linnaeus, 1766) complex previously diagnosed due to the presence of distinct cytotypes 2n = 58 and 2n = 60. Three esterase-D enzyme loci (Est-D1, Est-D2 and Est-D3) were examined and complemented with chromosomal data from 66 piranha specimens collected from Lake Catalao. For all specimens the Est-D1 and Est-D2 loci were monomorphic. In contrast, the Est-D3 locus was polymorphic with genotypes and alleles being differentially distributed in the previously described cytotypes and served as the basis for detecting a new cytotype (2n = 60 B). In cytotype 2n = 58 the Est-D3 locus was also polymorphic and presented Mendelian allelic segregation with four genotypes (Est-D3 11 , Est-D3 12 , Est-D3 22 and Est-D3 33 ) out of six theoretically possible genotypes, presumably encoded by alleles Est-D3 1 (frequency = 0.237),

Genome size discriminates between closely related taxaElytrigia repens andE. intermedia (Poaceae: Triticeae) and their hybrid

Flow cytometric and karyological investigations were performed on the closely related taxaElytrigia repens andE. intermedia (Poaceae: Triticeae) from the Czech Republic. DNA-hexaploids clearly prevailed among 238 examined plants and amounted to 96.2% of all samples. 2C-values ± s.d. for hexaploidElytrigia repens andE. intermedia were estimated at 23.27 ± 0.20 pg and 27.04 ± 0.24 pg respectively. Genome size thus allowed reliable separation of the two species (difference ca. 16%) as well as the identification of hybrid individuals. Natural hybridization inE. repens — E. intermedia alliance seems to be quite a common phenomenon as indicated from a large proportion (one sixth) of hexaploid samples with intermediate 2C-values. Previously, the crosses were most probably overlooked or misidentified due to their weak morphological differentiation. New nonaploid cytotypes (2n=9x=63) were revealed for both species as well as for the hybrid (determined on the basis of morphological characters only), representing the first records from the field. Fusion of unreduced and reduced gametes of the hexaploids is the most plausible mode of nonaploid origin.

Taxonomy and cytogeography of Cardamine raphanifolia and C. gallaecica (Brassicaceae) in the Iberian Peninsula

For a long time it was considered that Cardamine raphanifolia is widely distributed with several infraspecific taxa in the Mediterranean region. Recent studies showed that C. raphanifolia is restricted to the northern Iberian Peninsula. Cardamine gallaecica from NW Spain was regarded to be closely related, but was originally regarded as C. amara, and later described as C. raphanifolia subsp. gallaecica. In this study, we validate the treatment of C. raphanifolia and C. gallaecica as distinct species, and show their clear differentiation based on morphometric and molecular AFLP analyses. Moreover, both species are clearly distinct from C. amara subsp. pyrenaea, which has an overlapping distributional range with C. raphanifolia. Hexaploid (2n = 48) and octoploid cytotypes (2n = 64) of C. raphanifolia, and tetraploid (2n = 32) and hexaploid (2n = 48) cytotypes of C. gallaecica were found. Due to their weak morphological and genetic differentiation, these polyploid races are not classified as separate taxa.

Comparative cytogenetic analysis in the species Uroderma magnirostrum and U. bilobatum (cytotype 2n = 42) (Phyllostomidae, Stenodermatinae) in the Brazilian Amazon

The genus Uroderma includes two species: U. magnirostrum and U. bilobatum. These species are characterized by their high degree of karyotypic evolution, diverging from most other species of the subfamily Stenodermatinae, which have a lower degree of chromosomic evolution. The present study reports the first banding patterns of U. magnirostrum (G-, C-banding and Ag-NOR) and U. bilobatum (C-banding and Ag-NOR). The chromosomic data in conventional staining of U. magnirostrum (2n = 36, NF = 62) and U. bilobatum (cytotype 2n = 42, NF = 50) are equivalent to that described in the literature. When compared, chromosomal homeologies are found in both karyotypes, as well as differences, confirming that karyotypic evolution in the Uroderma genus is intense. Fission, fusion, inversion or translocation events are required to explain the karyotypic evolution of this genus. The comparison of karyotype, described here, to one of the species of the genus Artibeus (2n = 30/31), suggests that some chromosomic forms are apomorphic and shared between the two species of Uroderma. This confirms the monophyly of the genus, and that U. magnirostrum presents a more primitive karyotype when compared to U. bilobatum.

Cytotypes of Andropogon gerardii Vitman (Poaceae): fertility and reproduction of aneuploids

In many North American prairies, populations of Andropogon gerardii Vitman (Poaceae) are composed of hexaploid and enneaploid cytotypes (2n = 60, 90), with intermediates occurring occasionally. Under controlled pollination, the two common cytotypes can be crossed, producing progeny with a range of chromosome numbers. In an investigation of fertility and compatibilities of intermediate cytotypes, individuals with chromosome numbers between 60 and 90 were crossed with each other, with the 2n = 60 and 90 cytotypes, and with South American Andropogon species having 60 chromosomes. Regardless of cytotype, all A. gerardii plants had some fertility and virtually all crosses produced seeds. Cytotype is only partially predictive of fertility. Inter-specific hybrids between A. gerardii and South American hexaploid species were vigorous but sterile. Gene flow in natural A. gerardii populations of mixed cytotype probably involves plants of all cytotypes.