Abstracts of volume 82, 2010
Loureiro J., Trávníček P., Rauchová J., Urfus T., Vít
P., Štech M., Castro S. & Suda J. (2010): The use of flow cytometry in the
biosystematics, ecology and population biology of homoploid plants. –
Preslia 82: 3–21.
Over the last decade there has been a tremendous increase in the use of
flow cytometry (FCM) in studies on the biosystematics, ecology and population
biology of vascular plants. Most studies, however, address questions related
to differences in genome copy number, while the value of FCM for studying
homoploid plant groups has long been underestimated. This review summarizes
recent advances in taxonomic and ecological research on homoploid plants that
were made using FCM. A fairly constant amount of nuclear DNA within each
evolutionary entity together with the often large differences between species
means that genome size is a useful character for taxonomic decision-making.
Regardless of the number of chromosomes, genome size can be used to delimit
taxa at various taxonomic levels, resolve complex low-level taxonomies, assess
the frequency of interspecific hybridization or infer evolutionary
relationships in homoploid plant groups. In plant ecology and evolutionary
biology, variation in genome size has been used for prediction purposes
because genome size is associated with several phenotypic, physiological
and/or ecological characteristics. It is likely that in the future the use
of FCM in studies on taxonomy, ecology and population biology of homoploid
plants will increase both in scope and frequency. Flow cytometry alone, but
especially in combination with other molecular and phenotypic approaches,
promises advances in our understanding of the functional significance of
variation in genome size in homoploid plants.
Krahulcová A. & Rotreková O. (2010): Use of flow
cytometry in research on apomictic plants. – Preslia 82: 23–39.
This paper reviews recent use of flow cytometry in studies on apomictic
plant taxa. The most of apomictic angiosperms are polyploid, often differing
in ploidy level from their sexual counterparts within the agamic complex. Flow
cytometry is widely used for screening the ploidy levels of mature plants and
their seed generated both in the field and in experiments. Routine ploidy
screening often accompanied by molecular markers distinguishing individual
genotypes are used to reveal novel insights into the biosystematics and
population biology of apomictic taxa. Apomixis (asexual seed formation) is
mostly facultative, operating together with other less frequent reproductive
pathways within the same individual. The diversity in modes of reproduction in
apomicts is commonly reflected in the ploidy structure of their progeny in
mixed-cytotype populations. Thus, flow cytometry facilitates the detection and
quantification of particular progeny classes generated by different
reproductive pathways. The specific embryo/endosperm ploidy ratios, typical of
the different reproductive pathways, result from modifications of double
fertilization in sexual/apomictic angiosperms. Thus, the reproductive origin
of seed can be identified, including autonomous or pseudogamous apomixis,
haploid parthenogenesis and sexual reproduction, involving either reduced or
unreduced gametes. Collectively, flow cytometry has been used to address the
following research topics: (i) assessing the variation in ploidy levels and
genome sizes in agamic complexes, (ii) detection and quantification of
different reproductive modes in facultative apomicts, (iii) elucidation of
processes in populations with coexisting sexual and apomictic biotypes, (iv)
evolution of agamic complexes, and (v) genetic basis of apomixis. The last
topic is of paramount importance to crop breeding: the search for candidate
gene(s) responsible for apomixis is the main objective of many research
programmes. A list of the angiosperm taxa that could provide model systems for
such research is provided.
Šmarda P. & Bureš P. (2010): Understanding intraspecific
variation in genome size in plants. – Preslia 82: 41–61.
Intraspecific variation in genome size makes it possible to study ongoing
processes of genome size evolution. Although there are over 200 papers on
intraspecific variation in genome size, there is still limited understanding
of this phenomenon, especially as many of these papers are based on weak
methodology and therefore report biased or false evidence of the extent of
intraspecific variation. In this paper the recent progress in understanding
the spatio-temporal dynamics of intraspecific variation in genome size caused
by the gradual accumulation of mutations is reviewed. The results of the case
studies on Microseris douglasii, Zea mays, Silene latifolia,
Hordeum spontaneum and Lolium hybrids, and in particular that on
Festuca pallens, are discussed. The variation in genome size that
occurs within species is caused mainly by differences in the content of
repetitive DNA, in particular it is a consequence of the dynamics of
transposable elements. Variation may be induced and maintained
polytopically.We assume that it is probably more frequent in groups of young
radiating species. Even in the initial stages, the variation in genome size
generated within a population seems to be restricted by selection, which is
also important in stabilizing genome size within species. The long-term
persistence of the variation within a population and its further accumulation
may be enhanced by gametes with different genome sizes, produced by the
segregation of unequally sized homeologous chromosomes. Over large
geographical scales and across contrasting environmental gradients, the
distribution of genome sizes within species may be influenced by the
nucleotype effect, with smaller genomes being more successful at higher
latitudes and altitudes and under stressful conditions. However, the small
differences in genome size within species seem generally to be of minor
importance relative to other components of plant fitness that may be
selectively favourable under particular environmental or habitat conditions.
The processes generating variation in genome size may be associated with
phenotypic variation. While the shift in the genome size of a population
through selection enables adaptive evolution of genome size in a newly arising
species, the spatio-temporal variation in genome size within an ancestral
species allows for a rapid multiple genome size divergence of related species
through random drift in genome size (founder effect, bottleneck effect) during
range fragmentation, hybridization and/or polyploidization.
Temsch E. M., Greilhuber J. & Krisai R. (2010):
Genome size in liverworts. – Preslia 82: 63–80.
Liverworts are poorly represented in the record of DNA C-values. Data for
not more than nine species are reported in the literature. Here we present
flow cytometric measurements of genome size for 32 foliose and 11 thallose
species from 22 out of 83 families. The main method used in this study was
flow cytometry using propidium iodide as the DNA stain. Feulgen
densitometrywas applied as a supplementary method but it proved less suitable
because the rigid cellwalls of liverwort tissue are resistant to maceration
and apparently often inhibit the diffusion of reagents, which results in low
estimates of DNA content. The precise or approximate number of chromosomes
were counted, where possible. Among the thallose liverworts, the lowest
1C-value was recorded for Marchantia polymorpha (0.293 pg) and the
highest for diploid Pellia epiphylla (7.401 pg). Haploid
P. epiphylla (1C = 3.803 pg) had the largest genome among the haploid
thalloid liverworts. Among the foliose liverworts, Lejeunea cavifolia
with a value of 0.211 pg (1C) was ranked the lowest and Mylia taylorii, a
haploid with 7.966 pg (1C) and a large amount of dense heterochromatin,
concentrated in one big spherical chromocentre, the highest. This 38-fold
variation covers the extremes of the whole sample and exceeds the ca 12-fold
variation recorded in mosses (0.174–2.160 pg, 1C). This variation is
nevertheless low compared to the 2000-fold interspecific variation found in
angiosperms. Several instances of intraspecific variation in DNA ploidy (x and
2x) were found – in Radula complanata, Pellia epiphylla
and Metzgeria furcata. In Lophocolea heterophylla, accessions
differed 3.37-fold in C-value at haploid chromosome number. This points to
cryptic taxonomic differentiation and warns against premature statements about
ploidy levels based only on DNA measurements. Significant intraspecific
intraploidal variation in C-value was also observed in certain instances. In
Frullania dilatata, female plants with two large heterochromatic
sex-chromosomes have a 1.35-fold higher C-value than male plants with only one
sex chromosome. In most other cases of intraspecific variation the role of sex
differences remains to be clarified.
Kubešová M., Moravcová L., Suda J., Jarošík V. &
Pyšek P. (2010): Naturalized plants have smaller genomes than their
non-invading relatives: a flow cytometric analysis of the Czech alien flora.
– Preslia 82: 81–96.
Genome size has been suggested as one of the traits associated with
invasiveness of plant species. To provide a quantitative insight into the role
of this trait, we estimated nuclearDNAcontent in 93 alien species naturalized
in the Czech Republic, belonging to 32 families, by using flow cytometry, and
compared it with the values reported for non-invading congeneric and
confamilial species from the Plant DNA C-values database. Species naturalized
in the Czech Republic have significantly smaller genomes than their congeners
not known to be naturalized or invasive in any part of the world. This trend
is supported at the family level: alien species naturalized in the Czech flora
have on average a smaller genome than is the mean value for non-invading
confamilials. Moreover, naturalized and non-invading species clearly differed
in the frequency of five genome size categories; this difference was mainly
due to very small genomes prevailing and intermediate to very large genomes
underrepresented in the former group. Our results provide the first
quantitative support for association of genome size with invasiveness, based
on a large set of alien species across a number of plant families. However,
there was no difference in the genome size of invasive species compared to
naturalized but non-invasive. This suggests that small genome size provides
alien plants with an advantage already at the stage of naturalization and need
not be necessarily associated with the final stage of the process, i.e.
invasion.
Suda J., Trávníček P., Mandák B. &
Berchová-Bímová K. (2010): Genome size as a marker for identifying the
invasive alien taxa in Fallopia section Reynoutria. –
Preslia 82: 97–106.
DAPI and propidium iodide flow cytometry were used to determine the
variation in genome size in 166 samples and of all taxa and ploidy levels of
Fallopia section Reynoutria (knotweeds) recorded in the Czech
Republic. Significant differences were detected in the amount of nuclear DNA,
associated with the ploidy levels and taxonomic identity of the material. At
each ploidy level, F. sachalinensis showed the lowest and F. japonica
the highest fluorescence intensities. The fluorescence values for the
hybridogenous F. ×bohemica were located in-between these two
levels. In most cases, there was at least a four-percent gap in fluorescence
values between the nearest neighbours belonging to a different taxon.
Intraspecific variation in genome size was very low in all taxa except
hexaploid F. ×bohemica; this could be due to the complex
evolutionary history of this taxon. Our results indicate that the amount of
nuclear DNA can be used as a reliable marker for the identification of
homoploid knotweed species and their hybrids. Different evolutionary pathways
for the origin of high polyploids and/or hybridogenous taxa are proposed based
on genome size.
Šafářová L. & Duchoslav M. (2010):
Cytotype distribution in mixed populations of polyploid Allium oleraceum
measured at a microgeographic scale. – Preslia 82: 107–126.
Despite the substantial knowledge of the variation in cytotypes at large
spatial scales for many plants, little is known about the rates at which novel
cytotypes arise or the frequencies and distributions of cytotypes at local
spatial scales. The frequency distribution, local spatial structure, and role
of habitat differentiation of tetra-, penta- and hexaploid cytotypes of the
bulbous geophyte Allium oleraceum were assessed in 21 populations
sampled in the Czech Republic. The ploidy levels determined by flow cytometry
confirmed that there was a mixture consisting of two or three cytotypes (i.e.
4x+5x, 4x+6x, 5x+6x, 4x+5x+6x). In addition, mixtures of cytotypes were found
at sites previously considered to be cytotype-homogeneous. At all sites
previously found to contain a mixture of two cytotypes, no plants with the
third ploidy level were found. Although the relative frequencies of cytotypes
varied considerably both among and within populations, mixed populations
consisting of tetra- and hexaploids were usually dominated by tetraploids.
This suggests that there are secondary contacts among cytotypes but there is
little gene flow among them except for the rare formation of hexaploids in
tetraploid populations. Cytotypes were not randomly distributed over the study
area but were spatially segregated at either 47.6% or 61.9% of the sites
investigated, depending on the statistical test (Mantel test or average
distance test) used. When the composition of habitats at each of the sites is
taken into account, cytotypes were more frequently spatially segregated at
sites with a heterogeneous environment than a homogeneous environment. This
implies that the cytotypes are ecologically differentiated. The frequent
co-occurrence of cytotypes, with or without significant spatial segregation,
at many sites with heterogeneous or homogeneous environments, however,
suggests that niche differentiation alone is probably ineffective in
determining co-occurrence. It is supposed that the prevailing vegetative
reproduction associated with local dispersal, a high population density of the
species in a landscape, and non-equilibrial processes influencing the
establishment and extinction of A. oleraceum populations can also
support the local co-occurrence of cytotypes.
Dušková E., Kolář F., Sklenář P., Rauchová J.,
Kubešová M., Fér T., Suda J. & Marhold K. (2010): Genome size correlates
with growth form, habitat and phylogeny in the Andean genus Lasiocephalus
(Asteraceae). – Preslia 82: 127–148.
Variation in genome size in a particular taxonomic group can reflect
different evolutionary processes including polyploidy, hybridization and
natural selection but also neutral evolution. Using flow cytometry, karyology,
ITS sequencing and field surveys, the causes of variation in genome size in
the ecologically and morphologically diverse high-Andean genus
Lasiocephalus (Asteraceae, Senecioneae) were examined. There
was a 1.64-fold variation in holoploid genome size (C-values) among 189
samples belonging to 20 taxa. The most distinct was a group of plants with
large genomes corresponding to DNA triploids. Disregarding the DNA triploids,
the remaining samples exhibited a pronounced (up to 1.32-fold) and rather
continuous variation. Plants with the smallest genomes most likely represent
intergeneric hybrids with the closely related and sympatric Culcitium
nivale, which has a smaller genome than Lasiocephalus. The
variation in genome size in samples of diploid Lasiocephalus was
strongly correlated with several environmental and life history traits
(altitude, habitat and growth form). However, all these factors, as well as
genome size itself, were correlated with phylogeny (main split into the
so-called ‘forest’ and ‘páramo’ clades), which most
probably represents the true cause of the differentiation in intrageneric
genome size. In contrast, relationships between genome size and phylogeny were
not apparent at lower divergence levels. Instead, here we suggest that
ecological conditions have played a role in driving shifts in genome size
between closely related species inhabiting different environments.
Collectively, this study demonstrates that various evolutionary forces and
processes have shaped the variation in genome size and indicates that there is
a need for multi-approach analyses when searching for the causes and
consequences of changes in genome size.
Trávníček P., Eliášová A. & Suda J. (2010): The
distribution of cytotypes of Vicia cracca in Central Europe: the
changes that have occurred over the last four decades. – Preslia 82:
149–163.
The formation and maintenance of polyploids (via the development of
various reproductive barriers) rank among the central questions of studies on
polyploid evolution. However, the long time scale of most evolutionary
processes makes the study of the dynamics of diploid-polyploid groups
difficult. A suitable candidate for a targeted comparative study is Vicia
cracca (Fabaceae), which in the late 1960s was subjected to a
detailed cytotype screening in Central Europe. Re-sampling the original
localities offers a unique opportunity to assess changes in the ploidy
structure of the populations, which should reflect the cumulative effect of
all the evolutionary forces acting on the plants. Using flow cytometry, the
DNA ploidy levels of more than 6,500 individuals of V. cracca collected
at 257 localities in Austria, the Czech Republic, Germany and the Slovak
Republic were estimated. Three different cytotypes (2x, 3x and 4x) were
detected. While tetraploids predominated in the western part of the area
investigated (179 populations), the diploids had a more easterly distribution
(62 populations). There is a secondary zone of cytotype contact near the
boundary between the Czech and Slovak Republics. Sixteen populations (~6%)
consisted of a mixture of 2x and 4x cytotypes. Triploids are very rare; only
seven individuals were found in two otherwise diploid populations, indicating
the existence of breeding barriers between diploids and tetraploids. The
distribution of cytotypes is similar to that determined four decades ago using
chromosome counts. Nevertheless, there are some discrepancies, namely the
current absence of: (i) the diploid cytotype in southern Bohemia and (ii) the
altitudinal segregation in the distribution of cytotypes, including two
formerly recognized chromosomal races of diploids, perhaps a result of more
representative sampling. Identical monoploid genome sizes (1Cx-values) of both
the majority ploidy levels support an autopolyploid origin of the
tetraploids.
Dúbravková D., Chytrý M., Willner W., Illyés E.,
Janišová M. & Kállayné Szerényi J. (2010): Dry grasslands in the Western
Carpathians and the northern Pannonian Basin: a numerical classification.
– Preslia 82: 165–221.
A syntaxonomical revision of dry grasslands of the alliances Bromo
pannonici-Festucion pallentis, Festucion valesiacae and
Koelerio-Phleion phleoidis (class Festuco-Brometea) in the natural
biogeographical region of the Western Carpathians and northern Pannonian Basin
is presented. A geographically stratified data set of 2686 relevés from the
south-eastern Czech Republic, northeastern Austria, Slovakia and northern
Hungary was divided into 25 clusters using a modified TWINSPAN algorithm. The
proposed classification simplifies and unifies the previous syntaxonomical
systems, which differ in these four countries. Main environmental gradients
responsible for variation in species composition of theses grasslands were
revealed by detrended correspondence analysis and interpreted using indicator
values. The major pattern of variation reflects soil nutrient availability and
moisture, which are negatively correlated with soil reaction.
Dudová L., Hájek M. & Hájková P. (2010): The
origin and vegetation development of the Rejvíz pine bog and the history of
the surrounding landscape during the Holocene. – Preslia 82: 223–246.
The Rejvíz bog is an extensive mire complex in Central Europe, with up to
7 m deep sediments and two natural lakes. Recent vegetation is one of the best
preserved examples of Pinus uncinata subsp. uliginosa (syn.
P. rotundata) bog woodland in Central Europe. The origin and development
of the mire and changes in the surrounding landscape vegetation are
reconstructed using sediment stratigraphy, radiocarbon dating, pollen analysis
and plant-macrofossils analysis, with particular emphasis on the processes
that resulted in the origin of Rejvíz bog and on pine woodland dynamics. Based
on identified species the water level changes were reconstructed. The sediment
started to accumulate more than 9000 years ago at an open mixed-woodland
spring with Dichodontium palustre. Later, poor fen vegetation with
sedges and horsetails developed. Around 6170 cal. yr BC the fen became
inundated for 2000 years and (semi)aquatic vegetation thrived. Next step in
the succession followed a decline in water level which resulted in the
development of drier oligothrophic vegetationwith a high representation of
pine and dwarf shrubs. After ca 1020 cal. yr BC the mire became the bog it is
now. Three wooded stages appeared in both the minerotrophic and ombrotrophic
developmental phases: before 6720 cal. yr BC, during ca 1960–1020 cal.
yr BC and recently. The vegetation in the surrounding landscape developed
without marked human interventions up till ca the last six or five centuries,
when deforestation and later settlement took place. Comparison with published
data from the Góry Bystrzyckie/Orlické hory Mts suggests that not only
regional, but also local vegetation changed in a similar way across the
middle-altitude eastern Sudetes, following oscillations in climate rather than
local changes in mire water regime.
Csiky J., Mesterházy A., Szalontai B. & Pótóné
Oláh E. (2010): A morphological study of Ceratophyllum tanaiticum, a
species new to the flora of Hungary. – Preslia 82: 247–259.
Ceratophyllum tanaiticum Sapjegin, a species new to the flora of
Hungary, was discovered at two localities in the Hungarian part of the Drava
Plain in 2008. These are the westernmost, disjunct localities of this
Pontic-Caspian endemic species. For characterization of the Hungarian
specimens, nine morphological features of nine Ceratophyllum taxa were
used in PCA, CVA analyses and UPGMA classification. In these analyses
Hungarian and other C. tanaiticum samples always formed a cluster distinct
from other Ceratophyllum taxa. These results confirm an earlier concept
in which the character peduncle length contributed the highest loading value
for separating C. tanaiticum from other 3–4 leaf-ordered species.
Microscopic morphological features, including the number of longitudinally
arranged lacunae in one row of parenchymatic tissue between the first and the
second dichotomic branching, the length of the sequence between the first and
second branching of leaves; number, morphology and width of bracts under the
fruit of fresh Hungarian material are identified as new characters for C.
tanaiticum, C. submersum and C. demersum.
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