Amplified fragment length polymorphisms (AFLP) reveal details of polyploid evolution in Dactylorhiza (Orchidaceae)

The utility of the PCR-based AFLP technique (polymerase chain reaction; amplified fragment length polymorphisms) was explored in elucidating details of polyploid evolution in the Eurasian orchid genus Dactylorhiza. We emphasized Swedish taxa but also included some material from the British Isles and elsewhere in Europe. Three different sets of primers, amplifying different subsets of restriction fragments, independently revealed similar patterns for relationships among the Dactylorhiza samples investigated. The AFLP data support the general picture of polyploid evolution in Dactylorhiza, i.e., that allotetraploid derivatives have arisen repeatedly as a result of hybridization beween the two parental groups D. incarnata s.l. (sensu lato; diploid marsh orchids) and the D. maculata group (spotted orchids). Within the incarnata s.l. group, morphologically defined varieties were interdigitated. The D. maculata group consisted of two distinct subgroups, one containing autotetraploid D. maculata subsp. maculata and the other containing diploid D. maculata subsp. fuchsii. Allotetraploids showed a high degree of additivity for the putative parental genomes, and relationships among them were partly correlated to morphologically based entities, but also to geographic distribution. Thus, allotetraploid taxa from the British Isles clustered together, rather than with morphologically similar plants from other areas.     

Electrophoretic evidence for all otetraploid origin of Dactylorhiza purpurella (Orchidaceae)

Evidence from all ozyme markers suggests that the NW European Dactylorhiza purpurella (Orchidaceae) is an allotetraploid which originated from taxa closely related to the present-day D. incarnata s. I. and D. fuchsii/D. maculata . However, Dactylorhiza purpurella deviates more strongly from the allotetraploid condition than other taxa previously investigated in Dactylorhiza (i.e., D. majalis, D. traunsteineri, D. sphagnicola , and D. lapponica ), in that the characteristic incarnata alleles occur at lower frequencies than expected at two loci. It is suggested that D. purpurella arose from parents slightly different from those giving rise to the other allotetraploids, or that the tetraploid genome in D. purpurella has been modified by rare recombination events between homoeologous chromosomes, replacing segments of the incarnata chromosomes with the fuchsii/maculata genome.     

Patterns of polyploid evolution in Greek marsh orchids (Dactylorhiza; Orchidaceae) as revealed by allozymes, AFLPs, and plastid DNA data

Polyploidy is common in higher plants, and speciation in polyploid complexes is usually the result of reticulate evolution. We examined variation in nuclear AFLP fingerprints, nuclear isozymes, and hypervariable plastid DNA loci to describe speciation patterns and species relationships in the Dactylorhiza incarnata/maculata polyploid complex (marsh orchids; Orchidaceae) in Greece. Several endemic taxa with restricted distribution have been described from this area, and to propose meaningful conservation priorities, detailed relationships need to be known. We identified four independently derived allopolyploid lineages, which is a pattern poorly correlated with prevailing taxonomy. Three lineages were composed of populations restricted to small areas and may be of recent origins from extant parental lineages. One lineage with wide distribution in northern Greece was characterized by several unique plastid haplotypes that were phylogenetically related and evidently older. The D. incarnata/maculata polyploid complex in Greece has high levels of genetic diversity at the polyploid level. This diversity has accumulated over a long time and may include genetic variants originating from now extinct parental populations. Our data also indicate that the Balkans may have constituted an important refuge from which northern European Dactylorhiza were recruited after the Weichselian ice age.     

The evolution of Dactylorhiza (Orchidaceae) allotetraploid complex: insights from nrDNA sequences and cpDNA PCR-RFLP data

Sequence data from a portion of the external transcribed spacer (ETS) and from the internal transcribed spacers (ITS1 and ITS2) of 18S-26S nuclear ribosomal DNA were used together with chloroplast DNA PCR-RFLP data to unravel patterns of allotetraploid speciation within the Western European Dactylorhiza polyploid complex. A maximum likelihood tree based on combined ETS and ITS sequences suggests that the Western European Dactylorhiza allotetraploids have evolved by hybridization between four main diploid lineages. Cloned sequences and the topology of the ITS plus ETS tree indicate that the allotetraploid species D. elata, D. brennensis, and D. sphagnicola have originated from the autotetraploid D. maculata together with the diploid D. incarnata, while D. majalis, D. traunsteineri, and D. angustata seem to have evolved by hybridization between the D. fuchsii s.str and D. incarnata lineages. Finally, the diploid D. saccifera lineage seems to have been involved together with the D. incarnata lineage in the formation of the allotetraploid D. praetermissa. The observed congruence between the chloroplast tree and the ITS/ETS tree suggests a directional evolution of the nrDNA after polyploidization in favor of the maternal genome. Considered together with morphological, biogeographical, and ecological evidence, the molecular analysis leads us to recognize four species within the investigated allotetraploid complex, namely D. majalis, D. praetermissa, D. elata, and D. sphagnicola.     

Genetic diversity and differentiation of allopolyploid Dactylorhiza (Orchidaceae) with particular focus on the Dactylorhiza majalis ssp. traunsteineri/lapponica complex

Genetic differentiation of Dactylorhiza majalis ssp. traunsteineri from the Alps, Scandinavia, and Britain was studied and compared with other allotetraploid members of the systematically challenging genus Dactylorhiza . One-hundred and eleven populations from altogether 18 taxa were analysed for eight polymorphic plastid markers and two size-variable fragments from the nuclear internal transcribed spacer (ITS) region. In total, 60 plastid haplotypes and six ITS alleles were found among the 737 individuals analysed. No clear differentiation between populations of ssp. traunsteineri from the three regions was revealed. However, ssp. traunsteineri was genetically differentiated from Dactylorhiza baumanniana , Dactylorhiza elata , and D. majalis ssp. sphagnicola , although the majority of allotetraploid taxa remained inseparable. Judging from the degree of concerted evolution in ITS, D. majalis ssp. alpestris may be regarded as a relatively old allotetraploid, whereas ssp. baltica and ssp. purpurella may be considerably younger. Based on plastid data, the Alp region had the highest genetic diversity followed by Scandinavia and Britain. The geographic distribution of haplotypes provided support for possible refugial areas around the Alps and for several independent immigration routes into Scandinavia after the last ice age.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 97 , 52–67.     

Polyploid evolution and plastid DNA variation in the Dactylorhiza incarnata/maculata complex (Orchidaceae) in Scandinavia

The Dactylorhiza incarnata/maculata complex (Orchidaceae) was used as a model system to understand genetic differentiation processes in a naturally occurring polyploid complex with much of ongoing diversification and wide distribution in recently glaciated areas in northern Europe. Data were obtained for 12 hypervariable regions in the plastid DNA genome. A total of 166 haplotypes were found in a sample of 1099 plants. Allopolyploid taxa have inherited their plastid genomes from D. maculata s.l. Overall haplotype diversity of the combined group of allopolyploid taxa was comparable to that of maternal D. maculata s.l., but populations of allopolyploids were also more strongly differentiated from each other and contained lower numbers of haplotypes than populations of D. maculata s.l. In addition to haplotypes found in extant D. maculata s.l., the allopolyploids also contained several distinct and widespread haplotypes that were not found in any of the parental lineages. Some of these haplotypes were shared between widespread allopolyploids. Divergent allopolyploids with small distributions did not seem to originate from local polyploidization events, but rather as segregates of already existing allopolyploids. Genetic diversification of allopolyploid Dactylorhiza is the result of repeated polyploid formation, secondary hybridization and introgression between already existing polyploids and extant representatives of parental lineages, hybridization between independently derived polyploid lineages, and phyletic diversification in the group of allopolyploids. Although some polyploid taxa must have evolved after the last glaciation, genetic material from the parental lineages has been transferred continuously for longer periods of time. This combination of processes may explain the taxonomic complexity encountered in Dactylorhiza and other polyploid complexes distributed in previously glaciated parts of Europe.     

Systematics and conservation genetics of Dactylorhiza majalis ssp. elatior (Orchidaceae) on Gotland

A tall allotetraploid member of the Dactylorhiza incarnata/maculata complex with unspotted leaves and large pinkish flowers from the island of Gotland in the Baltic was examined for molecular variation patterns at five nuclear microsatellite loci, nuclear ITS and in plastid haplotypes. The allotetraploid was well separated from allopatric allotetraploids of similar appearance, including the western European D. majalis ssp. integrata (syn. D. praetermissa) and forms of D. majalis ssp. lapponica from mainland Sweden. It also differed from other allotetraploids distributed in the Baltic Sea region, including D. majalis ssp. baltica and D. majalis ssp. lapponica. It is here recognized as D. majalis ssp. elatior (Fr.) Hedrén & H. A. Pedersen. Dactylorhiza osiliensis Pikner, described from Saaremaa (Estonia) is regarded as a synonym. The distribution covers Gotland, Saaremaa and possibly Hiiumaa. Dactylorhiza majalis ssp. elatior may have one or several recent origins within its present distribution area, and it contains no other molecular markers than those found in the parental D. incarnata var. incarnata and D. maculata ssp. fuchsii in the same area. It appears to have weak barriers towards secondary hybridization with its parental lineages. The situation is reminiscent to that of other young allotetraploids in the D. majalis s.l. complex, suggesting that introgression may be an underestimated process explaining the accumulation of genetic diversity in evolving allopolyploid plants.     

Dactylorhiza (Orchidaceae) in European Russia: combined molecular and morphological analysis

Four plastid and two nuclear (internal transcribed spacer [ITS] ribosomal DNA) markers were used in this study of the Dactylorhiza maculata and D. incarnata complexes (Orchidaceae: Orchidinae) to determine diversity and taxonomic distribution of haplotypes, hybridization frequencies, and maternal parentage of hybrids in 125 samples from 78 populations from European Russia and the Caucasus. A morphometric study of all populations revealed significant correspondence between morphological and plastid DNA data. Most D. maculata sensu stricto (s.s.) specimens from Russia have D. fuchsii haplotypes; this could be evidence for introgression or widespread hybridization between these species in northern Russia. Heterogeneity within populations is much higher for ITS data and is strongly correlated with latitude. Both plastid and nuclear data are significantly correlated with distribution along a south-north axis. Several haplotypes and ITS alleles uncommon in western Europe are more widely distributed in Russia, whereas some frequent haplotypes from western Europe are absent.     

Evolution,phylogeography and taxonomy of allopolyploid Dactylorhiza (Orchidaceae) and its implications for conservation

This review is based on recent molecular studies of Dactylorhiza (Orchidaceae). Most of the studies have focused on the allotetraploid members of the genus in general and on D. majalis ssp. lapponica in particular. It was concluded that most of the allotetraploid taxa have derived from hybridizations between the parental lineages D. maculata s.l. and D. incarnata s.l., with D. maculata s.l. serving as the seed parent. Evidence of multiple origins was found both among northern European allotetraploids as well as among Greek allotetraploids. Introgression from both parental lineages and hybridizations between independently derived polyploid lineages was also detected. The three morphologically similar taxa D. majalis ssp. traunsteineri, ssp. lapponica and ssp. russowii should be treated as one and most of the Greek allotetraploids should be regarded as regional variants of the southeastern European D. majalis ssp. cordigera. The Balkans and the Alps most probably served as refugia for the genus during the last glaciations and at least two waves of immigration reached Scandinavia. Finally, we suggest that the conservation of allotetraploid Dactylorhiza should emphasize important geographic areas and habitats and that the allopolyploids should have the same conservation status as the diploids.     

On the distinction of Dactylorhiza baltica and D. pardalina (Orchidaceae) and the systematic affinities of geographically intermediate populations

The eastern European Dactylorhiza baltica (Klinge) N. I. Orlova and the western European D. pardalina (Pugsl.) Aver. (= D. praetermissa var. junialis (Verm.) Sengh) are usually considered to have non-overlapping geographic distributions, for which reason it has rarely been realized that they are morphologically similar. They have not previously been thoroughly compared by molecular methods, and no existing flora or revision has convincingly demonstrated that they can be distinguished by morphological characters. In reality, they might be 'political' rather than natural taxa. Prompted by the recent discovery of geographically intermediate populations (in eastern Denmark), originally identified as D. baltica , we have addressed this problem by analysis of morphometric data as well as molecular data from allozyme markers, plastid haplotypes, nuclear ITS alleles and nuclear microsatellites. Dactylorhiza baltica and D. pardalina turned out to be clearly distinguished genetically, and although they are morphologically similar, a few characters were identified that distinguish with 81–85% certainty between the two taxa. Molecular and morphometric data place the geographically intermediate populations in D. pardalina . Both taxa were confirmed to be allotetraploids combining diploid genomes from the D. incarnata s.l. and D. maculata s.l. lineages, and they should therefore be recognized as infraspecic taxa under D. majalis s.l. Thus, D. baltica should be called D. majalis subsp. baltica ; D. pardalina is identical with D. praetermissa var. junialis , but the nomenclatural consequences for D. praetermissa , if treated as subspecies under D. majalis , are still unresolved.     

Geographical variation and systematics of the tetraploid marsh orchid Dactylorhiza majalis subsp. sphagnicola (Orchidaceae) and closely related taxa

Dactylorhiza majalis subsp. sphagnicola is an allotetraploid marsh orchid derived from parents closely similar to present‐day D. incarnata and the western European form of D. maculata subsp. maculata, suggesting that it has a postglacial origin. It extends from northwestern continental Europe into areas formerly covered by the Weichselian ice sheet in mid‐Scandinavia. Here, we studied the variation at both the plastid and nuclear marker systems to describe the geographical variation in subsp. sphagnicola and its evolutionary history. We investigated whether subsp. sphagnicola is affected by secondary hybridization and gene flow from its parental lineages or from other allotetraploid marsh orchids, and we also compared subsp. sphagnicola with other allotetraploids of similar origins. We analysed 492 plants from 50 populations. Thirty‐seven populations were collected as potential Dactylorhiza majalis subsp. sphagnicola, five as subsp. sesquipedalis (D. elata), one as D. elata subsp. brennensis, one as subsp. calcifugiens, one as subsp. occidentalis and the remaining five as populations with some affinity to subsp. lapponica (including D. traunsteineri). All populations were analysed for plastid haplotypes and nuclear internal transcribed spacer (ITS) allele frequencies, and a subset of 43 populations was analysed for five nuclear microsatellite loci. Dactylorhiza majalis subsp. sphagnicola was dominated by a single plastid haplotype that was also dominant in western European D. maculata subsp. maculata, and most of the alternative haplotypes differed by only one mutation from the dominant one. There was more variation in nuclear microsatellites and ITS, and the variation was geographically structured in these markers. Subspecies occidentalis and calcifugiens shared haplotypes with subsp. sphagnicola, whereas subsp. sesquipedalis and brennensis had other haplotypes. Dactylorhiza majalis subsp. sphagnicola may have a postglacial origin within its present continental distribution. It has incorporated genetic material from D. maculata subsp. maculata by secondary hybridization and introgression, and some northern populations have assimilated strongly divergent haplotypes from the northeastern form of D. maculata subsp. maculata. Subspecies sphagnicola has also evolved morphologically divergent local populations in the north that do not differ from the typical populations in genetic markers. It may form mixed populations with other allotetraploid subspecies of D. majalis and, at least at one site, it has become integrated with subsp. lapponica, demonstrating that independently derived allotetraploids may contribute to a common gene pool. Subspecies calcifugiens seems to be derived from subsp. sphagnicola, and further studies based on a larger sample may confirm that it is better recognized as a variety. The so‐called D. elata subsp. brennensis is of hybrid origin and combines markers from subsp. sesquipedalis with markers from the D. majalis core complex, possibly subsp. majalis. The new combination Dactylorhiza majalis subsp. sesquipedalis (Willd.) H.A.Pedersen & Hedrén comb. nov. is provided. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 168 , 174–193.     

Plastid DNA haplotype diversity and morphological variation in the Dactylorhiza incarnata/maculata complex (Orchidaceae) in northern Poland

To gain an overview of the variation in the Dactylorhiza incarnata/maculata complex in northern Poland, ten plastid DNA regions (seven microsatellite and three indel loci) and 23 morphometric characters were used. In total, 972 and 480 samples from 64 and 31 populations were utilized for the genetic and morphometric analyses, respectively. One hundred and forty‐one haplotypes that have not been reported previously were recognized. The continuity of morphological characters between the studied species and the impact of post‐glacial colonization on the observed complexity in the Dactylorhiza incarnata/maculata complex were concluded. It was confirmed that the allotetraploid group of D. majalis s.s. has inherited its plastid genome from D. maculata s.l., specifically from D. maculata ssp. fuchsii. In addition, some of the haplotypes found in D. majalis s.s. were distinct and evidently not present in the preserved D. maculata s.l. Although possible gene flow and introgression between two subspecies of the D. maculata s.l. group were indicated, we suggest that they should be treated as separate evolutionary units. Both the common and rare haplotypes show a similar pattern of geographical distribution for all four taxa analysed, which suggests that hybridization took place relatively recently, shortly after the retreat of the ice sheet. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 178 , 121–137.     

Evolutionary history of the Dactylorhiza maculata polyploid complex (Orchidaceae)

Taxonomic complexity may be associated with migration history and polyploidy. We used plastid and nuclear DNA markers to investigate the evolutionary history of the systematically challenging Dactylorhiza maculata polyploid complex. A total of 1833 individuals from 298 populations from throughout Europe were analysed. We found that gene flow was limited between the two major taxa, diploid ssp. fuchsii (including ssp. saccifera) and tetraploid ssp. maculata. A minimum of three autotetraploid lineages were discerned: (1) southern/western ssp. maculata; (2) northern/eastern ssp. maculata; and (3) Central European ssp. fuchsii. The two ssp. maculata lineages, which probably pre‐date the last glaciation, form a contact zone with high genetic diversity in central Scandinavia. Intermediate plastid haplotypes in the contact zone hint at recombination. Central Europe may have been a source area for the postglacial migration for the southern/western lineage of ssp. maculata, as well as for ssp. fuchsii. The northern/eastern lineage of ssp. maculata may have survived the LGM in central Russia west of the Urals. The tetraploid lineage of ssp. fuchsii is indistinguishable from diploid ssp. fuchsii, and is probably of postglacial origin. The Mediterranean region and the Caucasus have not contributed to the northward migration of either ssp. fuchsii or ssp. maculata. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101 , 503–525.     

Geometric morphometrics as a tool for understanding Dactylorhiza (Orchidaceae) diversity in European Russia

Geometric morphometric techniques were employed to assess the diversity of lip shapes (305 samples from 83 populations) in flowers of European Russian Dactylorhiza (Orchidaceae: Orchidinae). We found significant agreement between the results from geometric morphometrics, classic morphometrics and the distribution of certain nuclear DNA markers. The lip shapes from Arctic Dactylorhiza samples occupied an intermediate position between D. maculata and D. fuchsii samples from Central Russia, supporting a hybrid origin of 'northern tetraploids'. Lip shapes of the taxonomically controversial allotetraploid D. baltica were found to form a distinct group, with members having definite relationships with diploid D. incarnata samples from the same localities, indicating either their local origin or introgression with D. incarnata . In addition to demonstrating the value of geometric morphometric methods in studies of plant taxonomy and hybridization, we suggest future applications designed to explore pollinator-driven directional selection, developmental constraints and fluctuating asymmetry.  © 2005 The Linnean Society of London, Biological Journal of the Linnean Society , 2005, 85 , 1–12.     

Dynamics of polyploid formation and establishment in the allotetraploid rock fern Asplenium majoricum

Background and Aims

Successful establishment of newly formed polyploid species depends on several interlinked genetic and ecological factors. These include genetic diversity within and among individuals, chromosome behaviour and fertility, novel phenotypes resulting from novel genomic make-up and expression, intercytotypic and interspecific competition, and adaptation to distinct habitats. The allotetraploid rock fern Asplenium majoricum is known from one small population in Valencia, Spain, and several larger populations on the Balearic island of Majorca. In Valencia, it occurs sympatrically with its diploid parents, A. fontanum subsp. fontanum and A. petrarchae subsp. bivalens, and their diploid hybrid A. × protomajoricum. This highly unusual situation allowed the study of polyploid genetic diversity and its relationship to the formation and establishment of nascent polyploid lineages.

Methods

Genetic variation for isozyme and chloroplast DNA markers was determined for A. majoricum and A. × protomajoricum sampled thoroughly from known sites in Majorca and Valencia. Results were compared with variation determined previously for the diploid parent taxa.

Key Results

A highly dynamic system with recurring diploid hybrid and allotetraploid formation was discovered. High diversity in the small Valencian A. majoricum population indicates multiple de novo origins from diverse parental genotypes, but most of these lineages become extinct without becoming established. The populations on Majorca most probably represent colonization(s) from Valencia rather than an in situ origin. Low genetic diversity suggests that this colonization may have occurred only once.

Conclusions

There is a striking contrast in success of establishment of the Majorcan and Valencian populations of A. majoricum. Chance founding of populations in a habitat where neither A. fontanum subsp. fontanum nor A. petrarchae subsp. bivalens occurs appears to have been a key factor enabling the establishment of A. majoricum on Majorca. Successful establishment of this polyploid is probably dependent on geographic isolation from diploid progenitor competition.     

Genetic characterization of an arctic zooplankter: insights into geographic polyploidy

Species of Bosmina from the temperate regions of North America and Europe are diploid and reproduce by cyclical parthenogenesis. By contrast, this study provides evidence that the dominant bosminid taxon in High Arctic lakes reproduces by obligate parthenogenesis and is a polyploid derived from interspecific hybridization. Sinobosmina liederi, a species common in temperate North America, is likely to have been one parent of these hybrids, but the other parent is unknown. As neither parent was detected in the Arctic, it seems unlikely that the hybrid clones that now occupy arctic lakes were synthesized locally. Most habitats contained only one or two clones, despite a total of 38 clones in the region, suggesting that priority effects have been important in restricting diversity within single lakes. The high regional diversity of arctic bosminids could reflect either repeated hybridization between the parent taxa or the genetic instability of newly formed polyploid lineages. These processes would produce hybrid polyploids that are considerably more diverse than their sexual parent taxa, and this difference in genetic diversity may confer an advantage to the polyploid biotype. As many zooplankton taxa from the arctic possess genetic characteristics similar to those of bosminids, these processes may provide a general explanation for the widespread occurrence of polyploids in the Arctic.     

Systematics of the Dactylorhiza euxina/incarnata/maculata polyploid complex (Orchidaceae) in Turkey: evidence from allozyme data

 Material of Dactylorhiza were sampled from 49 localities in Turkey and investigated for allozyme variation at ten loci (nine enzyme systems). Among diploids, the Anatolian D. osmanica and D. umbrosa were allozymically variable, but not distinct from each other or from D. incarnata. Dactylorhiza saccifera contained the same alleles as the European D. fuchsii. Dactylorhiza iberica and D. euxina were distinct from each other and the other diploids. On basis of allozyme patterns three distinct allotetraploid genotypes were distinguished, and each of them could be treated as a separate species. Dactylorhiza nieschalkiorum is similar to European allotetraploids, and may have arisen from hybridization between D. incarnata s.l. and D. saccifera. Dactylorhiza urvilleana may have arisen from parents related to present-day D. saccifera and D. euxina, but it also contains additional alleles that have not been found in any of the diploids investigated. A third allotetraploid known from four populations in the Ardahan and Kars provinces of north-eastern Turkey combines the allozyme patterns found in material of D. incarnata s.l. from the same area with those from D. euxina. It is here described for the first time as D. armeniaca. Received November 14, 2000 Accepted June 20, 2001     

Nuclear ribosomal DNA sequence variation and evolution of spotted marsh-orchids (Dactylorhiza maculata group)

Sequences of both internal and external transcribed spacers of nuclear ribosomal DNA were sequenced for four species belonging to the Dactylorhiza maculata group or "spotted marsh-Orchids". These four species are D. fuchsii, D. saccifera, D. foliosa, and D. maculata. Extensive nuclear ribosomal DNA polymorphism was uncovered within the diploid D. fuchsii and the putative autotetraploid D. maculata. Within the phylogenetic trees reconstructed using parsimony and Bayesian analyses, four main lineages (A, B, C, and D) were well supported. While D. saccifera, D. maculata, and D. foliosa were confined to clades B, C, and D, respectively, D. fuchsii accessions were spread over three clades (A, B, and C). Lineage C, which included accessions of the diploid D. fuchsii and the tetraploid D. maculata, was closely related to the lineage of D. foliosa (lineage D), an endemic diploid species from Madeira. Moreover, intra-individual polymorphism was found within accessions of D. maculata, D. fuchsii, and D. saccifera. It is shown that in some instances two lineages, contributed to the observed intra-individual polymorphism (C and A in D. maculata, A and B in D. fuchsii and D. saccifera). Evolutionary scenarios leading to this extensive nuclear ribosomal DNA polymorphism are discussed in the light of results from maternally inherited chloroplast DNA markers and an autopolyploid origin of D. maculata from a D. foliosa-like ancestor is postulated.     

Diversity and evolution of the Hordeum murinum polyploid complex in Algeria

Population diversity and evolutionary relationships in the Hordeum murinum L. polyploid complex were explored in contrasted bioclimatic conditions from Algeria. A multidisciplinary approach based on morphological, cytogenetic, and molecular data was conducted on a large population sampling. Distribution of diploids (subsp. glaucum) and tetraploids (subsp. leporinum) revealed a strong correlation with a North-South aridity gradient. Most cytotypes exhibit regular meiosis with variable irregularities in some tetraploid populations. Morphological analyses indicate no differentiation among taxa but high variability correlated with bioclimatic parameters. Two and three different nuclear sequences (gene coding for an unspliced genomic protein kinase domain) were isolated in tetraploid and hexaploid cytotypes, respectively, among which one was identical with that found in the diploid subsp. glaucum. The tetraploids (subsp. leporinum and subsp. murinum) do not exhibit additivity for 5S and 45S rDNA loci comparative with the number observed in the related diploid (subsp. glaucum). The subgenomes in the tetraploid taxa could not be differentiated using genomic in situ hybridization (GISH). Results support an allotetraploid origin for subsp. leporinum and subsp. murinum that derives from the diploid subsp. glaucum and another unidentified diploid parent. The hexaploid (subsp. leporinum) has an allohexaploid origin involving the two genomes present in the allotetraploids and another unidentified third diploid progenitor.