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Morphological and molecular taxonomy of the annual diploids Anthoxanthum aristatum and A. ovatum (Poaceae) in the Iberian Peninsula. Evidence of introgression in natural populations
Abstract
The morphologically diverse annual sweet vernal grasses, Anthoxanthum aristatum and Anthoxanthum ovatum, have been traditionally classified as separate species, each containing several infraspecific ranks. However, transitional forms between the species have been commonly found in sympatric populations that present a remarkably high morphological variability. Alternative hypotheses based on hybridization events between these two polymorphic Mediterranean species, or the existence of only one highly variable taxon, have been suggested as potential explanations for the presence of intermediate forms. In this study, we aimed at disentangling whether the integrity of the species is maintained in sympatric scenarios and at clarifying the taxonomic boundaries of the taxa described within this complex. For this, we analysed macro- and micromorphological and genetic data from 12 Iberian populations of A. aristatum and A. ovatum. Our results revealed the existence of two lineages in the A. aristatum/A. ovatum complex that were not consistent with the morphological circumscription of these species and suggested introgression between A. aristatum and A. ovatum. We also observed that morphological variability was not equally distributed between the lineages. Finally, we found some morphological and genetic support for the specific recognition of A. aristatum and A. ovatum, but the definition of any infraspecific category within these taxa does not seem to be justified. © 2010 The Linnean Society of London, Botanical Journal of the Linnean Society, 2010, 164, 53–71.
... A. aristatum shows considerable morphological variability and genetic differentiation in both its native and non-native ranges (Pimentel et al. 2010;Drapikowska 2013;Drapikowska et al. 2013). Its ability to colonize various non-native habitats in Poland may result from a high level of polymorphic isozyme loci and high morphological variability previously observed in A. aristatum populations from Central and western Poland (Drapikowska et al. 2012;Drapikowska 2013). ...
... (Pereira et al. 2007) and P = 87.96% (Pimentel et al. 2010), whereas the heterozygote frequency was H e = 0.66 (Pereira et al. 2007). In turn, investigations using microsatellite markers showed that H e ranged from 0.36 to 0.82, while the polymorphism information content (PIC) ranged from 0.33 to 0.80 (Lema-Suárez et al. 2016). ...
... Genetic variability of native populations of A. aristatum presents a different pattern. Investigations using AFLPs conducted in the Iberian Peninsula indicated that the interpopulation variability for this species was 77.34%, whereas the intrapopulation variability was 22.66% (Pereira et al. 2007;Pimentel et al. 2010). ...
Anthoxanthum aristatum Boiss. is native to southern and western Europe and North Africa. In Central Europe this species is recognized as invasive. Its ability to colonize various habitats may result from a high level of polymorphic isozyme loci and high morphological variability. The aim of this study was to recognize the degree of genetic diversity of the studied invasive species at its non-native range limit using molecular markers. The examined plant material consisted of 70 samples collected from 7 populations originating from various habitats: arable fields, recently abandoned field and sandy grassland. Ninety-six the Directed Amplification of Minisatellite-region DNA loci and 82 Sequence-Related Amplified Polymorphism loci were detected. The genetic diversity at the species level was high. The majority of genetic variation was present within populations (68% and 66%), while the remaining molecular variation was distributed among populations within and among habitat types. Specimens originating from sandy grassland populations were grouped together in one cluster that was genetically distinct from the arable field and fallow populations. The high genetic diversity populations at the A. aristatum non-native range limit in Central Europe and their marked diversity in arable field and sandy grassland habitats suggest that this species may systematically cross both geographical and ecological barriers.
... A key role for the Mediterranean area in the evolution of the relatively small grass genus Anthoxanthum (Pimentel et al., 2013), along with still-unresolved relationships among diploid taxa with uncertain taxonomic concepts (e.g. Sahuquillo, 2003, 2008;Pimentel et al., 2010;Chumov a et al., 2015Chumov a et al., , 2016, first led us to attempt to resolve diploid evolution in this genus, with a special emphasis on the Mediterranean. ...
... For instance, the taxonomic as well as phylogenetic position of the 'Mediterranean diploid' among its counterparts is completely uncertain, in spite of long-standing awareness of its existence (Briquet, 1910;Borrill, 1963;Jones, 1964;Hedberg, 1967;Teppner, 1970;Felber, 1987;Chumov a et al., 2015). Another example is the occasional lumping of the phenotypically similar annuals A. aristatum and A. ovatum into the A. aristatum/ovatum complex based on genetic data (Pimentel et al., 2007b(Pimentel et al., , 2010, salient morphological resemblance (Pimentel and Sahuquillo, 2003;Pimentel et al., 2007aPimentel et al., , 2010 and indistinguishable but extremely variable genome size (Chumov a et al., 2015(Chumov a et al., , 2016. The fact is that the origin of this complex still remains unknown, as does the origin of the diploid A. maderense. ...
... For instance, the taxonomic as well as phylogenetic position of the 'Mediterranean diploid' among its counterparts is completely uncertain, in spite of long-standing awareness of its existence (Briquet, 1910;Borrill, 1963;Jones, 1964;Hedberg, 1967;Teppner, 1970;Felber, 1987;Chumov a et al., 2015). Another example is the occasional lumping of the phenotypically similar annuals A. aristatum and A. ovatum into the A. aristatum/ovatum complex based on genetic data (Pimentel et al., 2007b(Pimentel et al., , 2010, salient morphological resemblance (Pimentel and Sahuquillo, 2003;Pimentel et al., 2007aPimentel et al., , 2010 and indistinguishable but extremely variable genome size (Chumov a et al., 2015(Chumov a et al., , 2016. The fact is that the origin of this complex still remains unknown, as does the origin of the diploid A. maderense. ...
Background and aims:
Knowledge of diploid phylogeny and ecogeography provide a foundation for understanding plant evolutionary history, diversification patterns and taxonomy. The genus Anthoxanthum (vernal grasses, Poaceae) represents a taxonomically intricate polyploid complex with large phenotypic variation and poorly resolved evolutionary relationships. The aims of the study were to reveal: (1) evolutionary lineages of the diploid taxa and their genetic differentiation; (2) the past distribution of the rediscovered 'Mediterranean diploid'; and (3) possible migration routes of diploids in the Mediterranean.
Methods:
A combined approach involving sequencing of two plastid regions ( trnL-trnF and rpl32-trnL ), nrDNA ITS, rDNA FISH analyses, climatic niche characterization and spatio-temporal modelling was used.
Key results:
Among the examined diploid species, only two well-differentiated evolutionary lineages were recognized: Anthoxanthum gracile and A. alpinum . The other taxa - A. aristatum, A. ovatum, A. maderense and the 'Mediterranean diploid' - form a rather intermixed group based on the examined molecular data. In situ rDNA localization enabled identification of the ancestral Anthoxanthum karyotype, shared by A. gracile and two taxa from the crown group. For the studied taxa, ancestral location probabilities for six discrete geographical regions in the Mediterranean were proposed and likely scenarios of gradual expansion from them were suggested. Modelling past and present distributions shows that the 'Mediterranean diploid' has already been occurring in the same localities for 120 000 years.
Conclusions:
Highly congruent results were obtained and dated the origin and first diversification of Anthoxanthum to the Miocene. The later divergence probably took place in the Pleistocene and started polyploid evolution within the genus. The most recent diversification event is still occurring, and incomplete lineage sorting prevents full diversification of taxa at the molecular level, despite clear separation based on climatic niches. The 'Mediterranean diploid' is hypothesized to be a possible relic of the most recent common ancestor of Anthoxanthum due to their sharing of ancestral features.
... Whereas perennials (comprising A. amarum BROT., A. alpinum A. LÖVE et D. LÖVE, A. maderense TEPP-NER, and A. odoratum L.) are widely distributed and show variation in ploidy levels, their annual counterparts (comprising A. aristatum BOIS., A. gracile BIV., and A. ovatum LAG.) are exclusively diploid and largely restricted to the Mediterranean basin [31,33]. Several attempts have been made in recent years to clarify the taxonomy of European Anthoxanthum by using molecular and/or morphometric approaches [29,[34][35][36]. These authors, among others, lumped the phenotypically similar annuals A. aristatum and A. ovatum into the A. aristatum/ovatum complex and stated that, based on genetic data, A. alpinum would better be regarded as a subspecies of A. odoratum. ...
... Although the European species of Anthoxanthum have recently been subjected to a series of morphometric and genetic investigations (e.g., [29,[34][35][36]48]), many questions surrounding their evolutionary history have not been satisfactorily resolved. In addition, several published papers (e.g. ...
... Plants (see S1 Appendix for some scans) were identified on the basis of their morphology, following determination keys provided by [31][32][49][50]. We treated A. aristatum and A. ovatum as one species complex, based on the results of [34,36]. In addition to species appearing in the abovementioned taxonomic literature, we recognized one more group (tentatively called "Mediterranean diploid"), which we found in SE Europe and encompassed perennial diploids morphologically resembling A. odoratum occurring there. ...
The genus Anthoxanthum (sweet vernal grass, Poaceae) represents a taxonomically intricate polyploid complex with large phenotypic variation and its evolutionary relationships still poorly resolved. In order to get insight into the geographic distribution of ploidy levels and assess the taxonomic value of genome size data, we determined C- and Cx-values in 628 plants representing all currently recognized European species collected from 197 populations in 29 European countries. The flow cytometric estimates were supplemented by conventional chromosome counts.
In addition to diploids, we found two low (rare 3x and common 4x) and one high (~16x–18x) polyploid levels. Mean holoploid genome sizes ranged from 5.52 pg in diploid A. alpinum to 44.75 pg in highly polyploid A. amarum, while the size of monoploid genomes ranged from 2.75 pg in tetraploid A. alpinum to 9.19 pg in diploid A. gracile. In contrast to Central and Northern Europe, which harboured only limited cytological variation, a much more complex pattern of genome sizes was revealed in the Mediterranean, particularly in Corsica. Eight taxonomic groups that partly corresponded to traditionally recognized species were delimited based on genome size values and phenotypic variation. Whereas our data supported the merger of A. aristatum and A. ovatum, eastern Mediterranean populations traditionally referred to as diploid A. odoratum were shown to be cytologically distinct, and may represent a new taxon. Autopolyploid origin was suggested for 4x A. alpinum. In contrast, 4x A. odoratum seems to be an allopolyploid, based on the amounts of nuclear DNA. Intraspecific variation in genome size was observed in all recognized species, the most striking example being the A. aristatum/ovatum complex.
Altogether, our study showed that genome size can be a useful taxonomic marker in Anthoxathum to not only guide taxonomic decisions but also help resolve evolutionary relationships in this challenging grass genus.
... This methodology has been successfully applied to other complex groups of plants (e.g. Repka, 2003;Ospina, Sylvester & Sylvester, 2016), including those in Anthoxanthinae (Pimentel, Estévez & Sahuquillo, 2007;Pimentel, Catalán & Sahuquillo, 2010). Thirdly, we sequenced several commonly used plastid and ribosomal nuclear DNA markers (e.g. ...
... Discordance in topologies is common in plants and can be due to different causes, most commonly hybridization and incomplete lineage sorting (Renoult et al., 2009). The frequency of reticulate evolution in Hierochloë and in Anthoxanthinae (Pimentel et al., 2010(Pimentel et al., , 2013Chumová et al., 2017;Tusiime et al., 2017) and the variation of ploidy found in the section suggest hybridization as a likely explanation. Nevertheless, specific t e s t s u s i n g m o r e s a m p l e s s h o u l d b e m a d e to confirm this hypothesis for H. quebrada. ...
An integrative approach combining morphological, molecular and cytological information was used to assess the taxonomy and biogeography of Hierochloë section Monoecia. More specifically, we aimed to evaluate (1) if the morphological and molecular data are in concert with the current taxonomy of the group and (2) if speciation in this exclusively South American group could be linked to the formation of the Andes. Our analysis of 31 macro- and micromorphological characters, four plastid and nuclear DNA regions, and nuclear DNA content suggests that the taxonomic status of several of the species in the section is not justified based on either the phylogenetic (apomorphic) or the phenetic species concepts. We propose that only four out of the eight species in the section (H. pusilla, H. juncifolia, H. quebrada and H. redolens) should be recognized and the remaining taxa (H. altissima, H. gunckelii, H. spicata and H. utriculata) should be reduced to varieties of the widespread H. redolens. In addition, we recover a biogeographical scenario for section Monoecia including genetic exchange between the southern and the central Andes, recent and incomplete diversification in the southern Andes, and longer isolation history for those species in the section with restricted ecological and/or geographical ranges
... Ripe caryopses were collected from seven A. aristatum/ ovatum populations (we treated A. aristatum Boiss. and A. ovatum Lag. as a single species complex, based on the results of Pimentel et al. 2007Pimentel et al. , 2010 in France, Portugal and Spain during the years 2008-2009 (Table 1). They were sown in 2013 and 2014, and allowed to grow under controlled conditions in growth chambers and a greenhouse at the CEITEC centre (Kamenice 753/5, Brno, Czech Republic). ...
... However, this contradiction might be caused by heterogeneity of the material under investigation because our data come from populations of two weakly differentiated taxa, A. ovatum and A. aristatum, that might be of hybrid origin and whose taxonomic complexity is as yet unresolved (e.g. Pimentel et al. 2010). On the other hand, a relatively high degree of intraspecific genome size variability in other members of the genus Anthoxanthum has been found to be associated with A-chromosomes only (Chumová et al. 2015). ...
Nuclear genome size is strongly influenced by the number, size and morphology of chromosomes, and there is often a good correlation between genome size and total chromosome length within a karyotype. Because aneuploidy or the presence of accessory chromosomes has repeatedly been reported within the Anthoxanthum
aristatum/ovatum complex (Poaceae), both phenomena have to be considered as potential sources of genome size variability within this group. This variability in nuclear genome size reaches 40 %, not only within the complex but also within single populations. Genome size variation, however, does not necessarily correlate positively with the number of chromosomes, as our data also indicate. Although our karyological survey revealed the presence of at least one B-chromosome in 44 % of individuals, we found almost no correlation between the number of B-chromosomes and genome size variability. The presence of B-chromosomes usually increases individual genome size, but does not affect substantially the extent of variability within the complex or population regardless of whether individuals with accessory chromosomes are included. These findings indicate that changes mainly in A-chromosomes are responsible for a huge fraction of genome size variability in the A. aristatum/ovatum complex.
... The genus Anthoxanthum is distributed mainly in temperate and arctic-alpine regions of northern Eurasia, the Mediterranean, Macaronesia, and East Africa. The delimitation of several species within the genus is controversial (e.g., [2,[4][5][6][7]), but the most traditional taxonomic concepts [5,6,8] recognize seven Anthoxanthum species in Europe, three annuals (A. aristatum Bois., A. gracile Biv., and A. ovatum Lag.) and four perennials (comprising A. alpinum A. Löve et D. Löve, A. maderense Teppner, A. odoratum L., and A. amarum Brot.). ...
Polyploidy has played a crucial role in the evolution of many plant taxa, namely in higher latitudinal zones. Surprisingly, after several decades of an intensive research on polyploids, there are still common polyploid species whose evolutionary history is virtually unknown. Here, we addressed the origin of sweet vernal grass (Anthoxanthum odoratum) using flow cytometry, DNA sequencing, and in situ hybridization-based cytogenetic techniques. An allotetraploid and polytopic origin of the species has been verified. The chromosome study reveals an extensive variation between the European populations. In contrast, an autopolyploid origin of the rarer tetraploid vernal grass species, A. alpinum, has been corroborated. Diploid A. alpinum played an essential role in the polyploidization of both European tetraploids studied.
... Una inspecció detallada de les plantes a Ses Fonts Rodones ha revelat l'existència de l'altra espècie anual en la Mediterrània: A. ovatum. Estudis recents (Pimentel et al., 2010) avalen el reconeixement dels dos tàxons emprant els caràcters morfològics florals que indiquen alguns autors (p. ex. ...
New chorological data and taxonomic observations referring to the vascular flora of Menorca are reported for 23 taxa. 8 taxa provide a new record for the flora of the Balearic Islands: Anthoxanthum ovatum Lag., Filago lutescens Jord., Juncus tenageia Ehrh. ex L.f., Serapias olbia Verg., Setaria viridis subsp. pycnocoma (Steud.) Tzvelev, Trifolium michelianum Savi, Trifolium resupinatum var. majus Boiss and Vinca major L. And 4 taxa make a new record for the flora of Menorca: Asplenium azomanes Rosselló, Cubas & Rebassa, Crucianella latifolia L., Hypecoum procumbens L., Sedum stellatum L., Five taxa with an uncertain presence on the island are confirmed: Adonis microcarpa DC., Medicago rigidula (L.) All., Mentha spicata L., Prunella vulgaris L., Teucrium scordium L. subsp. scordium. Other records are of taxa that are considered as very rare in the island (less than 5 populations known).
Es donen a conèixer noves dades corològiques i observacions taxonòmiques per a la flora de Menorca referents a 23 tàxons. D'aquests 8 són novetat per a la flora de les Balears: Anthoxanthum ovatum Lag., Filago lutescens Jord., Juncus tenageia Ehrh. ex L.f., Serapias olbia Verg., Setaria viridis subsp. pycnocoma (Steud.) Tzvelev, Trifolium michelianum Savi, Trifolium resupinatum var. majus Boiss i Vinca major L. Altres 4 ho són per la flora de Menorca: Asplenium azomanes Rosselló, Cubas & Rebassa, Crucianella latifolia L., Hypecoum procumbens L., Sedum stellatum L., Les altres citacions corresponen a taxons dels que la seva presència a l'illa era poc precisa o no s'havien citat des de feia anys: Adonis microcarpa DC., Medicago rigidula (L.) All., Mentha spicata L., Prunella vulgaris L., Teucrium scordium L. subsp. scordium, o d'altres dels que es coneixien poques localitats.
... aristatum, A. ovatum and the Macaronesian species) and one Eurasian group (A. odoratum, A. alpinum and A. amarum; Pimentel et al., 2007b Pimentel et al., , 2010 Sahuquillo, 2007, 2008 ). The differentiation among species within these groups was, however, weak. ...
Background and Aims Repeated hybridization and/or polyploidization confound classification and phylogenetic inference, and multiple colonizations
at different time scales complicate biogeographical reconstructions. This study investigates whether such processes can explain
long-term controversies in Anthoxanthum, and in particular its debated relationship to the genus Hierochloë, the evolution of its conspicuously diverse floral morphology, and the origins of its strikingly disjunct occurrences. A
hypothesis for recurrent polyploid formation is proposed.
Variation of 9 isozyme systems was studied in Polish populations of 3 species of the genus Anthoxanthum: the native A. odoratum s. str. L. and A. alpinum Á. Löve & D. Löve, as well as the alien A. aristatum Boiss. Results of this study show that A. odoratum is characterized by a high isozyme variability of lowland populations, weakly correlated with habitat type, and partial genetic distinctness of montane populations. Moreover, 5 isozyme markers have been identified (Pgi-2, Dia-2, Mdh, Idh, Pgm) for the allopolyploid A. odoratum. Populations of A. aristatum are highly polymorphic (P = 98%). The observed isozyme differentiation of its populations (FST = 0.087) is low and gene flow between them (Nm = 5.314) is high. The genetic variation reflects environmental variation only to a small extent and is not significantly related to the phase of chorological expansion of this species. Altitudinal vicariants, A. alpinum and A. odoratum, are characterized by morphological and isozymatic distinctness, indicating their reproductive isolation. In populations of A. alpinum, polymorphism is high (P = 76.92%), differentiation among populations is moderate (FST = 0.198), and gene flow between populations along the altitudinal transect (Nm = 1.709) is relatively low
Premise of the study: Non-plastid microsatellite primers were developed for the first time in the Eurosiberian complex of Anthoxanthum L., a genus of temperate grasses in which reticulate evolution is common.
Methods and Results: A microsatellite-enriched genomic DNA library allowed the detection of 500 fragments containing a microsatellite motif. Fifteen primer pairs were selected for an extended primer test. A preliminary analysis was conducted on the Eurasian diploid lineages of Anthoxanthum, with special emphasis on three populations of the Mediterranean A. aristatum Boiss./A. ovatum Lag. complex. Thirteen out of 15 markers tested were polymorphic in the complex, with successful cross-amplification in A. odoratum L. (93% of polymorphic loci, PL), A. amarum Brot (73% PL), A. alpinum Löve & Löve (73% PL), and A. maderense (60% PL).
Conclusions: These microsatellite markers will enable the analysis of evolution and phylogeography in diploid and polyploid lineages of this important genus.
Populations of Anthoxanthum odoratum from Wielkopolska Lowland growing in different habitats (natural, semi-natural and synanthropic) were examined in respect of 24 morphological traits of panicle. Morphological diversity of Anthoxanthum odoratum populations were not correlated with habitats they occupied.
Three Anthoxanthum species are found in Poland: the native A. odoratum L. s. str. and A. alpinum Á. Löve & D. Löve, and the alien A. aristatum Boiss. Major problems within this genus concern: (1) population variation of the native A. odoratum, representing various phases of ecological expansion to anthropogenic habitats; (2) population variation of A. odoratum and A. alpinum along the altitudinal transect; and (3) variation between populations of A. aristatum colonizing new areas and habitats outside its natural range of distribution (chorological expansion). In this study, morphological and anatomical variation of the three Polish Anthoxanthum species was analysed in detail. The variation of A. odoratum and A. aristatum was analysed in respect of environmental differences: habitat types and soil parameters. In the Babia Góra massif, variability distribution along the altitudinal transect was analysed for two vicariants: A. odoratum and A. alpinum. A odoratum in this massif does not cross the upper forest limit (i.e. forest line), and lower montane populations are morphologically very similar to lowland populations. Morphological and anatomical differences were detected between populations of A. alpinum along the altitudinal transect in the Babia Góra massif, with distinct upper montane populations. Moreover, clear morphological differences were found between the two altitudinal vicariants. Lowland populations of A. odoratum are characterized by great morphological variation, only weakly correlated with the type of occupied habitat and the phase of ecological expansion. The detected morphological variation reflects only to a limited extent the environmental variation of occupied habitats, and is not significantly correlated with the phase of chorological expansion. Some soil parameters are significantly correlated with some morphological characters studied in all the Anthoxanthum species. The analysed anatomical features of stems and leaves show continuous variation in the three species.
Results of research on relics of cultivation in Central Europe are presented, based on the example of Malva alcea L. (hollyhock mallow). Species from this group were cultivated in the past for various purposes, but are no longer utilized.
Thanks to the detailed studies conducted in Mecklenburg (NW Germany) and in Wielkopolska (W Poland), M. alcea is one of the best-studied relics of cultivation. This paper presents the available information on its former uses, general
and regional distribution, and habitat preferences.
Descriptive “keys”, including definitions and diagrams, for standardizing and simplifying the description of grass leaf structure as seen in transverse section are given. Over 500 characters are included with the possibility for expansion to 999. Notes on variation and taxonomic importance of the characters are also included.
Descriptive “keys”, including definitions and explanatory diagrams, are given for the standardization and simplification of anatomical descriptions of the epidermides of grass leaf blades as seen in surface view. About 340 characters of the epidermis are included with ample room for expansion. Notes on variation and taxonomic importance of the characters are also included.
In this review, we discuss findings from studies carried out over the past 20+ years that document the occurrence of asymmetric introgressive hybridization in a plant clade. In particular, analyses of natural and experimental hybridization have demonstrated the consistent introgression of genes from Iris fulva into both Iris brevicaulis and Iris hexagona. Furthermore, our analyses have detected certain prezygotic and postzygotic barriers to reproduction that appear to contribute to the asymmetric introgression. Finally, our studies have determined that a portion of the genes transferred apparently affects adaptive traits.
We used a combined molecular and morphological approach to solve a long-term controversy in the taxonomically complex genus Draba L. (Brassicaceae): the delimitation of Draba lactea Adams versus Draba fladnizensis Wulfen. We also tested hypotheses on the origin of D. lactea, which has been reported as hexaploid and possibly derived from the diploids D. fladnizensis, Draba nivalis Liljeblad, and (or) Draba subcapitata Simmons. In an initial analysis of large population samples of three of these autogamous species, intrapopulational isozyme variation was low or absent (mean genotypic diversity, D, was 0.10), the diploids were almost invariably homozygous, and D. lactea was highly fixed-heterozygous. In the main analysis, we examined 3547 populations of the four tentative species from the arctic archipelago of Svalbard for variation in isozymes, random amplified polymorphic DNAs (RAPDs), and 36 morphological characters. Multivariate analyses of the RAPD data revealed four very distinct groups of multilocus phenotypes. These groups also differed in several morphological characters and corresponded to the four tentative species. The species were less differentiated at isozyme loci, in particular the diploids D. fladnizensis and D. subcapitata, but D. lactea was clearly distinguished from D. fladnizensis based on all three data sets. Contrary to most earlier suggestions, the hexaploid D. lactea was genetically more similar to D. subcapitata than to D. nivalis, but our analyses of the material from Svalbard did not give conclusive evidence on the origin of this widespread arctic hexaploid.Key words: arctic, Draba, isozymes, morphology, polyploidy, RAPDs.
A systematic revision of the Epipetrum group of Dioscorea (Dioscoreaceae), which traditionally included three taxa endemic to Chile, is presented. We evaluated the taxonomic value of macro- and micromorphological traits to delimit generic boundaries with respect to other yams and to identify and separate its taxa. The comprehensive survey included 10 qualitative and 43 quantitative traits related to all plant organs and new microanatomical features of leaf, fruits, seeds, and pollen. Discriminant analyses were conducted with three accumulative morphological data sets to test seven taxonomic hypotheses of differentiation among taxa. Our results indicate that these taxa are characterized by the combination of prominent pistillodes in male flowers and a base chromosome number of x = 7, which separate it from all other Dioscoreaceae, plus different sets of morpho-anatomical traits that differentiate it from other putatively closely related yams with unwinged seeds in Dioscorea (the Borderea group, the Nanarepenta group, the Tamus group, etc.). Dioscorea biloba is the most distinctive species. Our analyses revealed significant morphological differences between northern and southern populations of this species resulting in the recognition of two subspecies, the northern D. biloba subsp. biloba, and the new southern D. biloba subsp. coquimbana. Dioscorea humilis and D. polyanthes are morphologically similar and only differ in qualitative leaf traits. This minor variation is better treated by reducing D. polyanthes to subspecific rank in D. humilis, and the combination D. humilis subsp. polyanthes is made herein.
In the present study, several multivariate analyses were carried out to assess the taxonomic relationships among European species of the genus Anthoxanthum. A total of 1787 Anthoxanthum specimens representing all European taxa were analyzed. Thirty macro-morphological (13 quantitative and 17 qualitative) and 29 micro-morphological (7 quantitative and 22 qualitative) characters were considered. First, resemblances between specimens were established independently for macro- and micro-morphological characters using Gower's similarity coefficient, and were represented by means of principal coordinates and cluster analyses. Subsequently, different multivariate analyses were applied to quantitative and qualitative macromorphological data to determine the most discriminant characters and the accuracy of the present taxonomic structure of the genus. Finally, dissimilarities among groups of individuals –species and populations- were estimated using the information radius measure and then represented in different dendrograms. Within annuals, Anthoxanthum gracile is clearly differentiated morphologically, yet no compelling morphological differentiation can be found between Anthoxanthum aristatum and Anthoxanthum ovatum. Moreover, the definition of subspecies in the annual taxa is not supported by our results. Then, within perennials, although the morphological relationships among Anthoxanthum amarum, Anthoxanthum odoratum and Anthoxanthum alpinum have also been resolved, further research is needed to assess the taxonomic position of the Macaronesian endemic Anthoxanthum maderense.
We used a combination of amplified fragment length polymorphisms (AFLP) and morphological data from 272 individuals from 59 populations to investigate the species-level taxonomy of Carex roanensis and allied species. There were two taxonomic problems in this group: identifying the appropriate taxonomic status for Carex roanensis, and clarifying the distinctions (if any) between C. virescens and C. swanii. Principal coordinate analysis of the morphological data suggested four entities corresponding to C. aestivalis, C. roanensis, C. swanii, and C. virescens, but clear discrimination was not possible. In contrast, the AFLP data showed marked discontinuities among these four species, placing even morphological intermediates into one of four groups. Analysis of molecular variance revealed significant population differentiation within each species, but only C. virescens had any detectable differentiation between geographic regions. This study confirms the species-level distinction between the common and widespread taxa C. swanii and C. virescens, as well as that of the globally rare Appalachian endemic C. roanensis.
This study analyzes the morphological and genetic characteristics of three sympatric populations of Prosopis from Argentina. Although morphological and geographical data suggest that Prosopis chilensis var. riojana is an interspecific hybrid of Prosopis chilensis var. chilensis and Prosopis flexuosa var. flexuosa, no correlation was found between morphological traits and genetic distances generated by random amplified polymorphic DNA - polymerase chain reaction (RAPD-PCR). Genetic similarity is greater among P. chilensis var. chilensis and P. flexuosa var. flexuosa than between either of these two taxa with P. chilensis var. riojana. Also, P. chilensis var. riojana has unique genetic markers that are absent from its putative parents. Additionally, dendrograms generated by unweighted pair group method with arithmetic means (UPGMA) and Neighbor-Joining clustering criteria group P. chilensis var. chilensis and P. fexuosa var. flexuosa apart from P. chilensis var. riojana. Possibilities for the lack of congruence between morphology and RAPD markers are discussed. The results obtained are insufficient to conclusively establish the origin of P. chilensis var. riojana; however, the morphological and genetic traits observed suggest this taxon is well differentiated from P. chilensis var. chilensis and P. fexuosa var. fexuosa.
Multivariate analysis tools are exploited on a data set composed of quantitative characteristics collected on 35 populations of plants of theDactylorhiza maculata (L.)So group from Western-Europe. These samples lead to four well-defined clusters; this, together with qualitative, cytological and ecological arguments, allows for the recognition of four specific entities:D. maculata s.str.,D. fuchsii (Druce)So,D. saccifera (Brongn.)So andD. caramulensis (Vermeulen)Tyteca. It is concluded that the floral characters play an essential role in the taxonomical distinction. It also appears that the set of characters measured, as well as the methods exploited, are especially well-suited and valuable tools for the morphological study of the genusDactylorhiza.
We describe extensions to the method of Pritchard et al. for inferring population structure from multilocus genotype data. Most importantly, we develop methods that allow for linkage between loci. The new model accounts for the correlations between linked loci that arise in admixed populations (“admixture linkage disequilibium”). This modification has several advantages, allowing (1) detection of admixture events farther back into the past, (2) inference of the population of origin of chromosomal regions, and (3) more accurate estimates of statistical uncertainty when linked loci are used. It is also of potential use for admixture mapping. In addition, we describe a new prior model for the allele frequencies within each population, which allows identification of subtle population subdivisions that were not detectable using the existing method. We present results applying the new methods to study admixture in African-Americans, recombination in Helicobacter pylori, and drift in populations of Drosophila melanogaster. The methods are implemented in a program, structure, version 2.0, which is available at http://pritch.bsd.uchicago.edu.
This second volume completes a project, begun by Cambridge University Press, to produce an up-to-date detailed Greek flora. A team of 25 botanists from several European countries catalogue the flora and endemic species found in the Greek mountain region. Each entry gives name and bibliography reference, synonomy, a description of the species, notes on nomenclature and typification, ecology and flowering time, distribution, chromosome number and special features.
We describe a model-based clustering method for using multilocus genotype data to infer population structure and assign individuals to populations. We assume a model in which there are K populations (where K may be unknown), each of which is characterized by a set of allele frequencies at each locus. Individuals in the sample are assigned (probabilistically) to populations, or jointly to two or more populations if their genotypes indicate that they are admixed. Our model does not assume a particular mutation process, and it can be applied to most of the commonly used genetic markers, provided that they are not closely linked. Applications of our method include demonstrating the presence of population structure, assigning individuals to populations, studying hybrid zones, and identifying migrants and admixed individuals. We show that the method can produce highly accurate assignments using modest numbers of loci—e.g., seven microsatellite loci in an example using genotype data from an endangered bird species. The software used for this article is available from http://www.stats.ox.ac.uk/~pritch/home.html.
Molecular markers derived from PCR amplification of genomic DNA are an important part of the toolkit of evolutionary geneticists. RAPDs, AFLPs, and ISSR polymorphisms allow analysis of species for which prior DNA sequence information is lacking, but dominance makes it impossible to apply standard techniques to calculate F-statistics. We describe a Bayesian method that allows direct estimates of Fst from dominant markers. In contrast to existing alternatives, we do not assume prior knowledge of the degree of within-population inbreeding. In particular, we do not assume that genotypes within populations are in Hardy-Winberg proportions. Our estimate of Fst incorporates uncertainty about the magnitude of within-population inbreeding. Simulations show that samples from even a relatively small number of loci and populations produce reliable estimates of Fst. Moreover, some information about the degree of within population inbreeding (Fis) is available from data sets with a large number of loci and populations. We illustrate the method with reanalysis of RAPD data from 14 populations of a North American orchid, Platanthera leucophaea.
Morphological variation of Carex muricata from 232 localities in the Czech Republic was analysed. The plants were preliminarily classified using qualitative characters into six species: C. contigua, C. muricata, C. pairae, C. chabertii, C divulsa, and C. leersiana. Of 27 quantitative characters, all were used in a principal components analysis and 25 in a discriminant analysis. Both analyses were done using the data for all the species and then separately for the taxonomically complicated species pairs. In the discriminant analysis, the most useful characters for separating particular species were selected; they included the distance between the first and second lowermost spike of the infructescence, infructescence length, glume length in pistillate flower, achene length, length of perigynium beak and spike size. In the classification discriminant analysis, with the six most important characters, 94.4% of plants were correctly classified to the designated groups. The analysis showed that some species pairs (C. muricata - C. pairae, C. chabertii - C leersiana) are only partially distinguished by quantitative morphological characters. Some other species (C contigua C. divulsa), however, are well differentiated and easily identified.
A method is presented by which the gene diversity (heterozygosity) of a subdivided population can be analyzed into its components, i.e., the gene diversities within and between subpopulations. This method is applicable to any population without regard to the number of alleles per locus, the pattern of evolutionary forces such as mutation, selection, and migration, and the reproductive method of the organism used. Measures of the absolute and relative magnitudes of gene differentiation among subpopulations are also proposed.
1 Phenotypic plasticity and genetic differentiation may influence how natural populations colonize variable environments, and thus help explain differences in distribution of closely related taxa. The response to shading in woodland and open habitat populations of endemic diploid and widespread tetraploid Arrhenatherum elatius was studied. 2 Two questions were examined. (i) Does the widespread tetraploid A. elatius ssp. elatius show greater phenotypic homeostasis in fitness-related traits than the related Mediterranean endemic diploid ssp. sardoum? (ii) Do the two ploidy levels differ in patterns of population differentiation related to the original habitat? 3 For each ploidy level, 10 genotypes from each of three populations from woodland and three from open habitats were grown in a garden environment at two light intensity levels. 4 No differences in phenotypic plasticity of morphological, phenological and fitness-related traits studied were observed between the ploidy levels. Tetraploids showed greater vegetative and inflorescence size. 5 Tetraploid populations showed evidence of differentiation in relation to original habitat conditions: plants from open habitats had higher seed production, were taller and flowered earlier than populations from woodland habitats in both garden environments, but phenotypic plasticity did not differ between the two habitat types. No variation in phenotypic plasticity or population differentiation was observed among diploid populations from either habitat. 6 The lack of differences in plasticity between diploids and tetraploids, and the greater differentiation between woodland and open populations in tetraploids, are discussed in relation to the geographical distribution of the two ploidy levels.
The assignment of collections belonging to the genus Trema has been reassessed using numerical taxonomy methods. Observation in the field in Togo, West Africa, confirmed high phenotypic variation but not the previously asserted lack of character concordance within the T. guineensis complex. This study was carried out to assess the circumscription of taxa in the area. Distance between specimens was computed using the Gower's general coefficient of similarity and the non-parametric MODECLUS cluster analysis was used to discover how the specimens segregated. The existence of three clusters in the 158 specimen dataset using 44 morphological characters was suggested by MODECLUS. Canonical discriminant analysis supported the recognition of those three clusters using 40 morphological characters. Classificatory discriminant analysis showed that all specimens except one are identified correctly by the discriminant function. We suggest that three species be recognized in Togo and the neighboring countries: T. orientalis, T. africana, and T. nitens. A key to the species is included and the advantages of the method suggested here are discussed.
The amount and pattern of genetic variation was surveyed in two Swedish and three Czech populations of the rare perennial forest plantVicia pisiformis. This species has a mainly easterly-continental European distribution and has few and small populations in Sweden. It is classified as «vulnerable» on the Swedish Red Data list. Seeds from natural populations were collected and grown under controlled conditions in growth chambers. The variation was estimated in growth and fecundity traits and with Random Amplified Polymorphic DNA, RAPD. Low inter- and intra-population variation in RAPD-markers was found using 11 primers, with a similarity index (Wetton) for the families of 0.98. In contrast, multivariate analysis of variance showed significant morphological differences within and between populations. Also in the univariate ANOVAs, a number of the traits showed significant between- and/or within population differentiation. Cluster analysis for the morphological traits and RAPDs (UPGMA) did not structure the variation of families in accordance with their geographical distance. A Mantel test based on comparisons between Mahalonobı́s and Jaccard distance for morphological and RAPD data, respectively, did not reveal any significant correlation between the two matrices. It is concluded that if a genetic conservation program is to be applied onVicia pisiformis, different sampling strategies are needed to capture morphological vs RAPD variation. This is, to our knowledge, the first investigation that compares RAPD and morphological variation in a threatened plant species.
Minimum spanning trees (MST) and single linkage cluster analysis (SLCA) are explained and it is shown that all the information required for the SLCA of a set of points is contained in their MST. Known algorithms for finding the MST are discussed. They are efficient even when there are very many points; this makes a SLCA practicable when other methods of cluster analysis are not. The relevant computing procedures are published in the Algorithm section of the same issue of Applied Statistics. The use of the MST in the interpretation of vector diagrams arising in multivariate analysis is illustrated by an example.
Chase, M. W. & Hills, H. H.: Silica gel: An ideal material for field preservation of leaf samples for DNA studies. ‐ Taxon 40: 215–220. 1991. ‐ ISSN 0040‐0262.
Silica gels an inexpensive and reliable substance to preserve field‐collected leaves for molecular studies of variation in DNA. A method for its utilization is explained, and results are presented, comparing total cellular DNA samples extracted from a set of fresh and silica‐gel dried samples of the same species, as well as examining the efficiency of endonuclease restriction and intactness of DNA from of a set of field‐collected leaves preserved with silica gel.
The chapter introduces the idea that the relationships between natural conditions and the outcome of an observation may be deterministic, random, strategic or chaotic, and that numerical ecology addresses the second type of data; it describes the role of numerical ecology among the various phases of an ecological research. The chapter includes discussion of the following topics: spatial structure, spatial dependence, and spatial correlation (independent observations, independent descriptors, linear independence, independent variable of a model, independent samples, origin of spatial structures, tests of significance in the presence of spatial correlation, and classical sampling and spatial structure), statistical testing by permutation (classical tests of significance, permutation tests, alternative types of permutation tests), computer programs and packages, ecological descriptors (i.e. variables: mathematical types of descriptors, and intensive, extensive, additive, and non-additive descriptors), descriptor coding (linear transformation, nonlinear transformations, combining descriptors, ranging and standardization, implicit transformation in association coefficients, normalization, dummy variable coding, and treatment of missing data (delete rows or columns, accommodate algorithms to missing data, estimate missing values). The chapter ends on a description of relevant software implemented in the R language.
While researching Cardamine (Brassicaceae) in the Pyrenees, putative hybrid plants were found at two natural sites. Pollen grain viability, AFLP, and multivariate morphometric analyses were performed in order to assess the plants’ presumed hybrid origin, establishing that natural hybridization between the diploids C. crassifolia and C. amara ssp. pyrenaea had occurred. A new diploid nothospecies, C.×enriquei (2n = 2x = 16), is described. Examination of 18 morphological characters showed the intermediacy of the hybrid between the parental taxa in most characters. AFLP analyses of C. amara ssp. amara, ssp. austriaca, ssp. olotensis and C. raphanifolia, demonstrated the close position of the hybrid to C. crassifolia, and revealed that the highest number of markers were shared with the parents. Polymorphism found in the AFLP pattern of the hybrid suggested recurrent origin, segregation and/or backcrosses, although assessment of pollen viability indicated high male sterility. The hybridization event reported here represents the second documented case between the C. pratensis group and C. amara. An account of the nomenclature of C. crassifolia is also presented, including lectotypification of relevant names. © 2002 The Linnean Society of London, Botanical Journal of the Linnean Society, 2002, 139, 275–294.
Hybridization reveals the close affinity ofAnthoxanthum odoratum and the Mediterranean annualA. ovatum. A. alpinum is genetically somewhat more isolated; occasional sterile hybrids withA. ovatum can be obtained.
Morphology reveals an affinity betweenA. odoratum andA. ovatum. There are nodiagnostic characters linkingA. odoratum toA. alpinum.
The perennial nature of the generality ofA. odoratum, plus phenotypic flexibility and an ability to behave as an annual in particular habitats, suggest an affinity both toA. alpinum (winter-hardy perennial) andA. ovatum (variable annual or occasional biennial).
The artificial allotetraploid based on the sterile hybrid betweenA. alpinum andA. ovatum simulatesA. odoratum, more closely than do either of the diploids.
Experimental observations suggest a very reasonable possibility that a similar sequence of events perhaps occurring on several occasions under natural conditions could have given rise to the tetraploid speciesA. odoratum.
An autopolyploid series comprising 2x, 3x and 4x was obtained by colchicining the diploid speciesA. ovatum Lag. The autotriploid, used as seed and pollen parent, was back-crossed to diploid and tetraploid. No significant overall difference was observed in fertility, but there was a tendency for particular pair crosses to the diploid as female parent to show higher levels of seed-setting. This may be associated with the relatively large proportion of haploid pollen that functions when the triploid is used as the male parent.
The effectiveness, in part, of the freely liberated pollen of autotriploidAnthoxanthum in producing progeny, contrasts with the total failure of manually liberated allotriploidDactylis pollen. Triploid sterility may well relate to degree of hybridity.
Genetic unbalance induced by aneuploidy was considered to be more relevant than the “genetic ratio” in seeds, as an explanation of the type of interploid progeny obtained inAnthoxanthum.
Epidermal peels were made from specimens chosen from a wide range of different locations selecting 10 collections of each of the three species recognized by J. Looman and K. F. Best as being in the Canadian rough fescue complex. Cell measurements and observations on wall shape were made on cells from the intercostal zones. The results of this study are consistent with the suggestion that there are three taxa in the rough fescue complex. The mean values for cell length and wall shape showed that, statistically, the taxa differ significantly from each other; in a single specimen the characters showed a wide range of variation and none could be used reliably to confirm identification.
In recent years molecular data, especially from DNA, have provided more precise estimates of relationships among vascular plants. Different types of data have been used efficaciously at different levels of the taxonomic hierarchy from ordinal and familial classifications to genetic variation within populations. The impact on systematics has been enormous, often confirming previous hypotheses established through morphological or other data, but sometimes offering novel and surprising insights. Although it is far from clear which genes or intergenic regions will eventually be known to contain the most helpful phylogenetic information for general and special classification, it is abundantly clear that a genetic yardstick will be used routinely. The impact of molecular data on plant systematics is now having a similar import in biogeography. Sequence data, as well as DNA fingerprinting of various types, are now being employed to assess patterns of isolation and speciation, timing of changes of distributions and speciation events, routes of migration and/or dispersal, population-level divergence, and hybridization. Systematics and biogeography, therefore, are melding together more closely than ever before, because the same kinds of data can be used to address questions regarding evolutionary relationships as well as patterns of distribution in space and time. Data at the populational level are especially helpful in a multidisciplinary context for answering questions regarding infraspecific affinities and for explaining distributions resulting from recent historical and ecological factors. Examples from the genus Hypochaeris (Asteraceae) from southern South America, using DNA sequence and AFLP data, are used to illustrate these points. The genus appears to have originated in Eurasia, dispersed to South America during the past several million years, and radiated into more than 45 species that are adapted to many different ecological regimes.
The study of hybrids and their evolutionary significance is often based on a number of tacit assumptions regarding character expression in hybrids. This article examines morphological, chemical, and molecular character expression in hybrids to determine whether traditionally recognized properties of hybrid plants, such as hybrid intermediacy and character coherence, are actually supported by empirical evidence, and also examines the impact of hybrids on phylogenetic analyses. We show that hybrids are a mosaic of both parental and intermediate morphological characters rather than just intermediate ones, and that a large proportion of first (64%) and later generation hybrids (89%) exhibit extreme or novel characters. Chemical character expression in hybrids is more predictable, with predominantly additive or complementary expression for both first generation hybrids (68%) and hybrid taxa (54%). Likewise, the genetic basis, and thus the expression of molecular characters, is well-worked out and predictable, although non-Mendelian inheritance has been reported in a few instances for molecular markers as well.There is even less empirical support for the concept of character coherence than hybrid intermediacy. Although morphological character coherence has been reported in both artificial and natural hybrid populations, it appears to be the exception rather than the rule. This idiosyncratic relationship among morphological characters is shown to be the norm for the relationship of morphological to molecular characters, as well as for the relationship among molecular characters.Hybrids are shown to have little impact on the topology of nonhybrid taxa in phylogenetic trees. However, the expression of primitive vs. derived character states, the placement of hybrids in cladograms, the number of equally parsimonious trees produced, and the effects of hybrids on phylogenetic topology do not appear to be predictable. Thus, cladistic identification of hybrid taxa is difficult and may not be possible based on phenotypic data, regardless of the analytical tools used.
The present study attempts to review the systematics of Semele (Ruscaceae) in Madeira, based on phenotypic diversity. The variation in some vegetative (climbing shoot, second-order branches or ‘phylloclades’) and sexual (inflorescence and flowers) characters was analysed in 115 plant specimens from 30 field populations, herbaria of the Costa collection and Madeira Botanical Garden (MADJ) and certain gardens. Thirty-one quantitative and qualitative characters have been utilized in the analysis. Kaiser–Meyer–Olkin (KMO) analysis indicates adequate sampling. Principal component analysis (PCA) reveals that the spatial distribution of individuals has a discontinuous behaviour. Principal coordinate analysis (PCO) utilizing the Gower coefficient on standardized data revealed a significantly discontinuous distribution of individuals, such that two different clusters can be defined. The Student's t-test and Tukey test on separate characters, when individuals were classified according to the Costa classification, confirms the significant differences between grouping accessions. This leads to the recognition of two species within the genus in Madeira. Literature and herbarium studies show that these two taxa are conspecific with Semele androgyna (L.) Kunth sensu stricto (s.s.) and Semele menezesi Costa sensu lato (s.l.). A separated statistical analysis of the S. androgyna cluster shows the possible existence of additional subgroups. Based on field population distribution, ecological behaviour and variation in features, we propose the recognition of two species, S. androgyna (L.) Kunth and S. menezesi (Costa) Pinheiro de Carvalho, and two subspecies S. androgyna (L.) Kunth androgyna Pinheiro de Carvalho and S. androgyna (L.) Kunth pterygophora Pinheiro de Carvalho. © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society, 2004, 146, 483–497.
A new nothosubspecies Cirsium × vivantii is described after a molecular and morphological characterization of eight individuals collected in two separate valleys of the French central Pyrenees. Both hypervariable Amplified Fragment Length Polymorphism (AFLP) markers and nuclear rDNA (ITS) and plastid (trnL-F, TRNT-L) DNA sequences were analysed. The profiles of these hybrid samples were compared to those of 43 individuals belonging to their presumed parental taxa C. carniolicum ssp. rufescens and C. palustre. A total of 133 AFLP bands were scored from three primer-pair combinations. All 130 AFLP bands that amplified in the hybrid samples were present in either C. carniolicum ssp. rufescens, C. palustre or both taxa, supporting the participation of these plant genomes in the resulting hybrids. Several Additive Polymorphic Sites (APS) detected in the ITS sequences of the hybrid samples also confirmed their derived origins from ribotypes of the two parental taxa. The lack of exclusive AFLP markers and the nonconcerted evolution of rDNA polymorphisms towards either of the parental ribotypes indicated their recent origin. Plastid trnT-L sequences were used to identify C. palustre as the maternal parent of six of these hybrid individuals; either parent could have acted as the plastid genome donor for the other two individuals. The morphological study revealed that all hybrid individuals were morphologically intermediate between their parents showing largely lobed and less spiny basal leaves as in C. carniolicum ssp. rufescens and decurrent leaf bases and pinkish corollas as in C. palustre. © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society, 2007, 154, 421–434.
High morphological and ecological diversity has been observed in the north-west Iberian Peninsula endemic Anthoxanthum amarum Brot., for which two different morphotypes (northern and southern) have been described on the basis of qualitative traits and geographical origin. In the present study, a combined molecular and morphological method was applied to ten populations of this species with the following aims: (1) to assess whether the variation observed was taxonomically meaningful; (2) to assess the influence of the environment on the variation in the morphological characters; and (3) to track the potential phylogeographical information deduced from our random amplified polymorphic DNA marker (RAPD) data in order to draw inferences about the past history of this species in the north-west Iberian Peninsula. To achieve these aims, 26 macromorphological characters were recorded in 279 specimens, and 77 RAPD phenotypes were identified in the 79 plants studied. The association analyses performed using the morphological and molecular data showed that no clear separation existed between the morphs, and a strong correlation between qualitative characters and the environment was detected. Moreover, both the multivariate analyses and the assignment test based on RAPD data revealed that the genetic variation was hierarchically structured, and three genetically distinct groups could be identified. Two of these clusters might correspond to different expansion routes proposed in the literature for different plant species in the north-west Iberian Peninsula. © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society, 2007, 155, 179–192.
Anthoxanthum alpinum Löve & Löve has been described as a diploid perennial distributed in northern Eurasia and the high mountains of central and eastern Europe. Difficulties in finding reliable morphological differences between this taxon and the widespread tetraploid Anthoxanthum odoratum L. have resulted in taxonomists treating them as conspecific, despite the cytological differentiation. The purpose of this study was to use different approaches to assess the relationships between close congeners, such as the pair A. odoratum/A. alpinum. Macromorphological, micromorphological, and molecular data were gathered and analysed for 14 populations representing both taxa from Scandinavia and the Iberian Peninsula. Different cluster analyses were performed to study the relatedness between individuals and populations. Subsequently, a principal components analysis was computed on the basis of macromorphological quantitative traits, and principal coordinates analysis was used to analyse qualitative, micromorphological, and random amplification of polymorphic DNA (RAPD) data. An analysis of molecular variance was applied to the molecular data, and the genetic differentiation between samples was measured using the FST estimator. The results showed that the geographical origin was more important than the ploidy level in explaining the relatedness between specimens and populations. Moreover, a strong correlation was found between the micromorphological traits and environmental parameters. The results of the analyses do not support the assignment of a specific taxonomic rank to A. alpinum. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 156, 237–252.
The amount and pattern of genetic variation was surveyed in two Swedish and three Czech populations of the rare perennial forest plant Vicia pisiformis. This species has a mainly easterly-continental European distribution and has few and small populations in Sweden. It is classified as ‘vulnerable’ on the Swedish Red Data list. Seeds from natural populations were collected and grown under controlled conditions in growth chambers. The variation was estimated in growth and fecundity traits and with Random Amplified Polymorphic DNA, RAPD. Low inter- and intra-population variation in RAPD-markers was found using 11 primers, with a similarity index (Wetton) for the families of 0.98. In contrast, multivariate analysis of variance showed significant morphological differences within and between populations. Also in the univariate ANOVAs, a number of the traits showed significant between-and/or within population differentiation. Cluster analysis for the morphological traits and RAPDs (UPGMA) did not structure the variation of families in accordance with their geographical distance. A Mantel test based on comparisons between Mahalonobfs and Jaccard distance for morphological and RAPD data, respectively, did not reveal any significant correlation between the two matrices. It is concluded that if a genetic conservation program is to be applied on Vicia pisiformis, different sampling strategies are needed to capture morphological vs RAPD variation. This is, to our knowledge, the first investigation that compares RAPD and morphological variation in a threatened plant species.
Hybridization between plant species occurs frequently but hybrids are often restricted to ecotones or disturbed habitats. In this study we show that introgressive hybrids between the tetraploid Viola riviniana and the diploid V. reichenbachiana invaded pine forests of the Dübener Heide (central Germany), an area affected by calcareous pollutants. The spread of these violet populations was correlated with the impact of pollution on habitat conditions. We compared morphology, cytology and random amplified polymorphic DNA (RAPD) bands among six Viola populations from the Dübener Heide and three populations of each pure species. RAPD analysis using 12 primers revealed 141 scorable bands. We considered bands as species specific if they occurred in at least 75% of the plants in one pure violet species but in none of the other. Seven bands were specific to V. riviniana and 11 bands were specific to V. reichenbachiana. Two plants of a V. reichenbachiana population were identified as hybrids. Of the Viola populations from the Dübener Heide, one was diploid and could be classified as V. reichenbachiana by morphology and RAPD markers. However, the majority of the Dübener Heide populations were tetraploid, and of a more variable morphology than V. riviniana and V. reichenbachiana, showing different combinations of intermediate characters, characters of the pure species and extreme characters. Despite their overall genetic similarity to V. riviniana, these plants could be identified as introgressive hybrids between V. riviniana and V. reichenbachiana by species-specific RAPD bands. Therefore, we propose that recurrent hybridization and backcrossing resulted in novel genotypes adapted to the changed environment of polluted pine forests.
A contribution to the knowledge of Tylosema (Schweinf.) Torre & Hillc. is presented. The main objectives of this revision were: (1) to elucidate the taxonomic position of the specimens collected in south Angola, (2) to provide a review of species boundaries in the genus, especially between T. fassoglense (Schweinf.) Torre & Hillc. and T. esculentum (Burch.) A.Schreib. and (3) to evaluate the contribution of pollen morphology for delimitation of the species in this genus. Numerical analyses were performed based on morphometric data taken from herbarium specimens. Principal component analysis and cluster analysis divided specimens of Tylosema into four major groups, corresponding to three recognized species and a new taxon. A new micromorphometric character (swollen base of hairs) was found that further contributes to the distinction of T. humifusum (Pic.Serm. & Roti Mich.) Brenan from other species. A new species, T. angolense P. Silveira & S. Castro sp. nov., is described and illustrated. A taxonomic key and distribution map of studied taxa is also provided. The analyses of pollen morphology allowed for the distinction of the taxonomic groups. © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society, 2005, 147, 99–115.
1.
The analysis of the karyotype morphology of Anthoxanthum odoratum L. (2n=20) and the diploid A. alpinum A. et D. Lve has shown that: a) There is an extra-ordinary degree of inter-plant variation in the tetraploid. b) There are marked differences in the karyotypes of the two species.
2.
It is concluded that odoratum is not autotetraploid but a species of hybrid origin. This denies the diploid-autotetraploid relationship of alpinum and odoratum suggested by earlier workers and substantiates their separate classification.
3.
The karyotypes of the diploids A. aristatum, A. ovatum and an un-named species from Crete, suggest, that odoratum could have evolved from such crosses as alpinum ovatum, alpinum Cretean 2x or ovatum Cretean 2x.
4.
Meiotic analysis of odoratum shows that quadrivalent pairing is prevelant with some associations of six, eight or ten also present in each of the 20 plants studied. Ninety per cent of the multivalents are alternately orientated.
5.
Pairing in the F1 alpinum aristatum is very poor. In the F1 alpinum ovatum pairing is appreciable though erratic and gives evidence of inter-change heterozygosity.
6.
The colchicine amphidiploid of the latter hybrid has complete pairing with some quadrivalents and higher multiples.
7.
It is concluded that odoratum could have evolved from such a plant with selection for increased quadrivalent pairing.
8.
In odoratum and other segmental allotetraploids quadrivalent formation is considered to have a positive role in controlling the qualitative segregation of the ancestral sets.