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Alders (Alnus spp., Betulaceae) are keystone pioneer species in riparian habitats. In the Mediterranean Basin, where the diploid Alnus glutinosa coexists with the recently discovered tetraploid A. lusitanica , the distribution, diversity and genetic structure of alder species is unknown. The main objectives of this study were to report the distribution of A. glutinosa and A. lusitanica , quantify the local genetic diversity of populations and explore the presence of putative hybrids resulting from the coexistence of A. lusitanica and A. glutinosa individuals in Spain. We assessed 627 individuals from 22 natural alder populations by combining chromosome counts, flow cytometry and microsatellite markers (SSRs) analyses. The ploidy analysis, validated through chromosome counts, revealed the presence of 92 diploid and 535 tetraploid trees from three A. glutinosa and 18 A. lusitanica pure populations, respectively. Notably, no hybrids were detected, not even in Assa, the only population where both species co-occur. The occurrence of mixed ploidy level in alder is reported for the first time in Spain (Assa, Logroño, within the Ebro basin). SSR analysis revealed robust genetic differentiation between the two species and distinctive patterns of variation within A. glutinosa. The high level of differentiation observed was supported by the most probable population clustering determined through pca and structure analyses, along with the identification of a high number of private alleles. For A. lusitanica, the results revealed three distinct genetic groups, geographically distributed. Positive genetic and geographical distance correlations indicated that differentiation could have been driven by isolation by distance. In light of the results, A. lusitanica is the most representative, widespread and genetically variable alder species in Spain, and A. glutinosa is restricted to the north-east of the country. The Ebro riverbank is a contact zone between A. lusitanica and A. glutinosa species, in which no evidence of hybridization was detected yet. Finally, with focus on management, our findings may suggest considering A. lusitanica as a new species, which should be regulated by the forest reproductive material legislation. • Tetraploid A. lusitanica extends widely across southern, central and northwest Spain. • Diploid A. glutinosa is restricted to the northeast of Spain, only. • Ebro riverbank is a contact zone with mixed ploidy levels first reported in Spain. • Distribution, genetic diversity and structure of alders is first described in Spain. • Three distinct genetic groups in A. lusitanica were detected. [ABSTRACT FROM AUTHOR]

Background: The last taxonomic account of Olea recognises six subspecies within Olea europaea L., including the Mediterranean olive tree (subsp. europaea) and five other subspecies (laperrinei, guanchica, maroccana, cerasiformis, and cuspidata) distributed across the Old World, including Macaronesian islands. The evolutionary history of this monophyletic group (O. europaea complex) has revealed a reticulated scenario involving hybridization and polyploidization events, leading to the presence of a polyploid series associated with the subspecies. However, how the polyploids originated, and how the different subspecies contributed to the domestication of the cultivated olive are questions still debated. Tracing the recent evolution and genetic diversification of the species is key for the management and preservation of its genetic resources. To study the recent history of the O. europaea complex, we compared newly sequenced and available genomes for 27 individuals representing the six subspecies., Results: Our results show discordance between current subspecies distributions and phylogenomic patterns, which support intricate biogeographic patterns. The subspecies guanchica, restricted to the Canary Islands, is closely related to subsp. europaea, and shows a high genetic diversity. The subsp. laperrinei, restricted now to high mountains of the Sahara desert, and the Canarian subsp. guanchica contributed to the formation of the allotetraploid subsp. cerasiformis (Madeira islands) and the allohexaploid subsp. maroccana (western Sahara region). Our phylogenomic data support the recognition of one more taxon (subsp. ferruginea) for the Asian populations, which is clearly segregated from the African subsp. cuspidata., Conclusions: In sum, the O. europaea complex underwent several processes of hybridization, polyploidy, and geographical isolation resulting in seven independent lineages with certain morphological traits recognised into subspecies., (© 2023. The Author(s).)

Niche segregation may prevent competitive exclusion and promote local coexistence. This typically results in the occupation of different habitats. In the freshwater ostracod Eucypris virens (Jurine, 1820), the distribution of sexual and parthenogenetic populations in the temporary Lake Caracuel, central Spain, was not homogeneous. Parthenogens were found everywhere including the littoral, whereas sexuals were restricted to the centre. We investigated the hypothesis that spatial distribution responded to ecological differences. We studied the ecological significance of this segregation by linking environmental data to male presence, sexual fraction, ploidy, and genetic structure of our model organism in 12 ponds in the lake basin. Hydro-chemical and biological data indicated that the observed segregation is not only spatial but also ecological, with sexual E. virens occurring in ponds with shorter and probably more unpredictable hydroperiod. The correlations between environmental gradients and E. virens population structure suggest that sexual and parthenogenetic lineages are ecologically segregated. Sexual populations appeared restricted to sufficiently unpredictable environments, while parthenogens dominated environments with longer hydroperiods. Local coexistence seems mediated by spatial heterogeneity in habitat stability. [ABSTRACT FROM AUTHOR]

Ranunculus L. represents the largest genus within Ranunculaceae, comprising more than 600 species with a worldwide distribution. However, there are still many gaps in our knowledge of the infrageneric taxonomy and evolution of Ranunculus. In this regard, intraspecific variation of the polyploid complex Ranunculus parnassiifolius remains under discussion. To reconstruct the biogeographical history of the polyploid complex R. parnassiifolius, 20 populations distributed throughout the Cantabrian Mountains, Pyrenees, and Alps were investigated. Phylogenetic studies were based on nuclear internal transcribed spacers ( ITS) and plastid ( rpl32- trnL, rps16- trnQ) sequence data, analysed using Bayesian approaches as well as the evolution of morphological characters. Additionally, biogeographical patterns were conducted using statistical dispersal-vicariance analysis. The analyses presented here support the recognition of two evolutionary independent units: R. cabrerensis sensu lato ( s. l.) and R. parnassiifolius s. l. Furthermore gradual speciation depending on the biogeographical territory is proposed, and optimal reconstructions have probably favoured the ancestor of Ranunculus parnassiifolius as originating in the Iberian Peninsula. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 107, 477-493. [ABSTRACT FROM AUTHOR]

Polyploidy and hybridisation are the basis of the evolution of Centaurea (Compositae). At the El Saler dune field (eastern Spain), the diploid Centaurea aspera ssp. stenophylla and the tetraploid C. seridis ssp. maritima form a polyploid complex in which C. × subdecurrens individuals occur. This polyploid complex was analysed morphologically and genetically, using random amplified polymorphic DNA (RAPD) and tubulin-based polymorphism (TBP) markers. Flow cytometry showed that the hybrids are triploid, which is a rare finding in Centaurea. Morphologically, in contrast to leaf characters, flowering characters clearly discriminated the three taxa. The genetic analyses confirm that C. × subdecurrens is a result of the hybridisation between Centaurea aspera ssp. stenophylla and C. seridis ssp. maritima, and suggest that backcrossing events and gene flow are very rare or absent. Although the hybrids likely represent true F1 offspring, they displayed some genetic diversity that is probably due to the combination of alleles. Genetic diversity was higher in diploid than in tetraploid individuals. This fact, and the high degree of sterility of the triploid hybrids, may reflect a cytotype minority exclusion effect. This may cause spatial segregation, which effectively takes place in the study area. Dune disturbance may lead to an overlapping of the parents' distribution areas, facilitating hybridisation. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The chromosome number and known karyological features (karyotype description, presence of secondary con- strictions, presence ofaccessory chromosomes, karyotype asymmetry) are reviewed for the sexually-reproducing endemic flora of the Balearic Islands (100 taxa), a continental archipelago in the Mediterranean. Chromosome numbers range from 2n = 8 (Crepis triasii) to 2n = 94 (Helictotrichon crass~foIizim), with 2n = 30 as the modal value. Overall, the number of inferred diploid taxa (57) predominates over polyploid ones (42). Intraspecific karyological variation accounts for about 10% of the whole endemic flora and includes within-individual poly- morphisms related to (1) euploid changes involving somatic segregation or endopolyploidy, (2) the presence of supernumerary (B) chromosomes, and (3) karyological variation in species showing holocentric chromosomes. True infraspecific cytological variation involving fixed euploid changes has been verified only in a single taxon, Ranunculuspaludosus subsp. barceloi. Overall, the documented patterns of infraspecific karyological variation in the endemic Balearic flora are oflimited evolutionary potential since (1) fixed number of accessory chromosomes within individuals has not been detected in any endemic species so far analyzed, and (2) the two ploidal cytotypes ofRanunculuspaludosus subsp. barce/oi are geographically structured (Eastern vs. Western Balearics), precluding the formation of hybrid zones. The available data (singularity of chromosome numbers and ploidy levels, as well as biosystematic and molecular evidence) strongly suggest that at least nine polyploid endeni ic species (Agrostis barceloi, A Ilium antonii-bolosii, A nthyllis hyxtrix, Brass ica balearica, Bupleurum harceloi, Centaurium bianoris, Coron il/a montserratii, Helictotrichon crass~foliuni, Polycarpon colomense) could have had autochthonous origins in the Balearic archipelago from diploid or low polyploid-level ancestors. This hypothesized polyploid element accounts for at least 26.2% of the endemic polyploid flora and contrasts with the low estimates of polyploid evolution reported from oceanic archipelagos. [ABSTRACT FROM AUTHOR]

Background: Phlomis lychnitis is a mostly endemic species of the Iberian Peninsula that frequently hybridizes with the narrow endemic P. crinita subsp. malacitana in southern Spain. Whenever they coexist they form homoploid hybrid zones. Unlike hybridization at the polyploid level, the process of hybridization at the homoploid level is much less well known., Methods and Results: In this study we report the development of 22 microsatellite markers through next-generation sequencing technologies for P. lychnitis. We characterize the genetic diversity for two populations of this species for the 10 markers that resulted to be polymorphic. Further, we check the transferability of these polymorphic markers to one population of P. crinita subsp. malacitana to verify the potential use of these markers for hybridization studies. The values of expected heterozygosity for P. lychnitis were higher than in P. crinita subsp. malacitana, and the three analyzed populations displayed negative values for the inbreeding coefficient which is compatible with the frequent instances of hybridization and introgression between species., Conclusions: This set of polymorphic markers are useful for further studies aiming at a deeper understanding of the homoploid hybrid process between these species. Additionally, this is the first panel of microsatellite markers developed for the genus Phlomis, a genus very rich in endemic species and with medicinal properties that could benefit from the use of these new markers., (© 2021. The Author(s), under exclusive licence to Springer Nature B.V.)

The conservation of a crop's wild relatives as genetic resources requires an understanding of the way genetic diversity is maintained in their populations, notably the effect of crop-to-wild gene flow. In this study, the amount of differentiation between natural and cultivated populations of Medicago sativa was analysed using random amplified polymorphic DNA (RAPD) markers and an extension of the AMOVA procedure adapted to autotetraploid organisms. Simulations of structured populations were performed to test whether AMOVA provides estimates of population structure in autotetraploids that can be directly compared to those obtained for allozyme data. Simulations showed that φ-statistics allow a good estimation of population differentiation when unbiased allelic frequencies are used to correct the conditional expectations of squared genetic distances. But such unbiased estimates can not be practically guaranteed, and population structure is notably overestimated when some populations are fixed for the presence of amplified fragments. However, removing fixed loci from the data set improves the statistical power of the test for population structure. The genetic variation of 15 natural and six cultivated populations of M. sativa was analysed at 25 RAPD loci and compared to estimates computed with allozymes on the same set of populations. Although RAPD markers revealed less within-population genetic diversity than allozymes, the quantitative and qualitative patterns of population structure were in full agreement with allozymes. This confirmed the conclusions drawn from the allozymic survey: crop-to-wild occurred in many locations, but some other mechanisms opposed cultivated traits to be maintained into natural populations. [ABSTRACT FROM AUTHOR]

The competitive ability of a tetraploid, and its morphologically indistinguishable progenitor diploid Dactylis glomerata L., from Galicia (Spain), was tested in a two-year study, using isolated plants and the same individuals grown at two densities (16 and 36 plants per pot, respectively). Inverse linear regression equations were used to quantify the response of the different ploidy levels (hereafter cytotypes) to density. For the diploids, inter-cytotype competition coefficients were significantly higher than intra-cytotype coefficients. The substitution rate increased from 18 in the first year to 19 in the second year, when most of the diploids failed to flower and some died. The competitive superiority of the tetraploids was associated with higher mean tiller weight, particularly in the mixed cultures. The tetraploids also had heavier seeds and faster leaf production in early spring, and they flowered earlier than the diploids. Several of these differences between cytotypes appear to be due to differences in ploidy level and may play a major role in the establishment of the tetraploids in Galician pastures, where competition is high. [ABSTRACT FROM AUTHOR]

The cytogeographic distribution and morphology of Festuca taxa in sections Bovinae and Scariosae has been compared with the results of experimental hybridization between them. Two groups have been established, the first is predominantly Moroccan and includes F. mairei (2n = 28), F. arundinacea varieties atlantigena forma pseudo-mairei (2n = 56), letourneuxiana and cirtensis (2n = 70). These taxa are closely related to the diploid F. scariosa endemic in the Spanish Sierra Nevada. Their distinctive morphological features are due to the inclusion of the scariosa genome. The second group, predominantly European, including F. arundinacea var. glaucescens (2n = 28) and F. arundinacea var. genuina (2n = 42), is similarly associated with the diploid F. pratensis. It is suggested that evolution in this species complex involved opportunities in a previous era for hybridization between tetraploid taxa now separated geographically. From such hybrids the higher polyploids can be derived. [ABSTRACT FROM AUTHOR]

Background: Gene flow and polyploidy have been found to be important in Juniperus evolution. However, little evidence has been published elucidating the association of both phenomena in juniper taxa in the wild. Two main areas were studied in Spain (Eastern Iberian Range and Sierra de Baza) with both diploid and tetraploid taxa present in sympatry. Gene flow and ploidy level were assessed for these taxa and the resulted offspring. Results: Twenty-two allo-triploid hybrids between J. sabina var. sabina and J. thurifera were found in the Eastern Iberian Range population. However, in the Sierra de Baza population no triploids were found. Instead, 18 allo-tetraploid hybrids between two tetraploid taxa: J. sabina var. balkanensis and J. thurifera were discovered. High genetic diversity was exhibited among the tetraploid hybrids at Sierra de Baza, in contrast to the genetically identical triploid hybrids at the Eastern Iberian Range; this suggests meiotic difficulties within the triploid hybrids. In addition, unidirectional gene flow was observed in both studied areas. Conclusion: Polyploidy and hybridization can be complementary partners in the evolution of Juniperus taxa in sympatric occurrences. Juniperus was shown to be an ideal coniferous model to study these two phenomena, independently or in concert. [ABSTRACT FROM AUTHOR]

In more than 60 families of angiosperms, the self- and cross-fertilization is avoided through a complex widespread genetic system called self-incompatibility (SI). One of the major puzzling issues concerning the SI is the evolution of this system in species with complex polyploid genomes. Among plums, one of the first fruits species to attract human interest, polyploid species represent enormous genetic potential, which can be exploited in breeding programs. However, molecular studies in these species are very scarce due to the complexity of their genome. In order to study the SFB gene [the male component of gametophytic self-incompatibility system (GSI)] in plum species, 36 plum accessions belonging to diploid and hexaploid species were used. A total of 19 different alleles were identified; 1 of them was revealed after analyzing sequences. Peptide sequence analysis allowed identifying the five domains features of the SFB gene. Polymorphism analysis showed a subtle difference between domesticated and open pollinated Tunisian accessions and suggested a probable influence of the ploidy level. Divergence analysis between studied sequences showed that a new specificity may appear after 5.3% of divergence at synonymous sites between pairs of sequences in Prunus insititia, 6% in Prunus cerasifera, 8% and 9% in Prunus domestica and Prunus salicina respectively. Furthermore, sites under positive selection, the ones more likely to be responsible for specificity determination, were identified. A positive and significant Pearson correlation was found between the divergence between sequences, divergence time, fixed substitutions (MK test), and PSS number. These results supported the model assuming that functionally distinct proteins have arisen not as a result of chance fixation of neutral variants, but rather as a result of positive Darwinian selection. Further, the role that plays recombination can not be ruled out, since a rate of 0.08 recombination event per polymorphic sites was identified.

The Achillea millefolium aggregate is one of the most diverse polyploid complexes of the Northern hemisphere and has its western Eurasian boundary in the Iberian Peninsula. Four ploidy levels have been detected in A. millefolium, three of which have already been found in Iberia (diploid, hexaploid and octoploid), and a fourth (tetraploid) reported during the preparation of this paper. We collected a sample from 26 Iberian populations comprising all ploidy levels, and we used microsatellite markers analyzed as dominant in view of the high ploidy levels. Our goals were to quantify the genetic diversity of A. millefolium in the Iberian Peninsula, to elucidate its genetic structure, to investigate the differences in ploidy levels, and to analyse the dispersal of the species. The lack of spatial genetic structure recovered is linked to both high levels of gene flow between populations and to the fact that most genetic variability occurs within populations. This in turn suggests the existence of a huge panmictic yarrow population in the Iberian Peninsula. This is consistent with the assumption that recent colonization and rapid expansion occurred throughout this area. Likewise, the low levels of genetic variability recovered suggest that bottlenecks and/or founder events may have been involved in this process, and clonal reproduction may have played an important role in maintaining this genetic impoverishment. Indeed, the ecological and phenologic uniformity present in the A. millefolium agg. in Iberia compared to Eurasia and North America may be responsible for the low number of representatives of this complex of species present in the Iberian Peninsula. The low levels of genetic differentiation between ploidy levels recovered in our work suggest the absence of barriers between them.

Background and Aims: Limonium is a well-known example of a group of plants that is taxonomically complex due to certain biological characteristics that hamper species' delineation. The closely related polyploid species Limonium vulgare Mill., L. humile Mill. and L. narbonense Mill. are defined species and can be used for studying patterns of morphological and reproductive variation. The first two taxa are usually found in Atlantic Europe and the third in the Mediterranean region, but a number of intermediate morphological forms may be present alongside typical examples of these species. This study attempts to elucidate morphological, floral and karyological diversity representative of these taxa in the Iberian Peninsula., Methods: The extent of morphological differentiation was tested through comparison of 197 specimens from both Portugal and Spain using 17 descriptive morphological characters and 19 diagnostic morphometric characters. Analyses of floral morphisms (heterostyly and pollen-stigma dimorphism) and karyological determinations were also conducted., Key Results and Conclusions: Discriminant analysis using morphometric variables reliably assigned individuals in natural populations to their respective groups. In addition, the results provide the first direct evidence that L. narbonense and a new species, LIMONIUM MARITIMUM: Caperta, Cortinhas, Paes, Guara, Espírito-Santo and Erben, SP NOV: , related to L. vulgare are present on Portuguese coasts. Most of these species are found together in mixed populations, especially L. vulgare and L. narbonense. It is hypothesized that taxonomic biodiversity found in sites where distinct species co-occur facilitates the evolutionary processes of hybridization, introgression and apomixis. This study therefore contributes to the elucidation of the taxonomic diversity in L. vulgare-related species and may also help in implementing future conservation programmes to maintain the evolutionary processes generating biodiversity., (© The Author 2014. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Appropriate management of species of conservation concern requires designing strategies that should include genetic information as small population size and restricted geographic range can reduce genetic variation. We used AFLPs to investigate genetic variation within and among populations of the endangered narrow endemic Centaurea borjae, and found no evidence for genetic impoverishment despite its <40 km range and potential for vegetative propagation. Genetic variation was comparable to other plants with similar life history (88 % occurring within populations) and potential clone mates were less frequent than expected. Nonetheless, populations separated by few hundred meters showed signs of significant genetic differentiation suggesting low gene flow between them. Our results suggested that the three geographically closer populations located at the center of the range might be treated as a single management unit, while the remaining ones could be considered independent units. We found evidence of fine-scale spatial genetic structure up to 80 m indicating that the collection of germplasm for ex-situ conservation should focus on individuals separated >80 m to maximize genetic variation.

• The ecological and adaptive significance of plant polyploidization is not well understood and no clear pattern of association between polyploid frequency and environment has emerged. Climatic factors are expected to predict cytotype distribution. However, the relationship among climate, cytotype distribution and variation of abiotic stress tolerance traits has rarely been examined. • Here, we use flow cytometry and root-tip squashes to examine the cytotype distribution in the temperate annual grass Brachypodium distachyon in 57 natural populations distributed across an aridity gradient in the Iberian Peninsula. We further investigate the link between environmental aridity, ploidy, and variation of drought tolerance and drought avoidance (flowering time) traits. • Distribution of diploids (2n = 10) and allotetraploids (2n = 30) in this species is geographically structured throughout its range in the Iberian Peninsula, and is associated with aridity gradients. Importantly, after controlling for geographic and altitudinal effects, the link between aridity and polyploidization occurrence persisted. Water-use efficiency varied between ploidy levels, with tetraploids being more efficient in the use of water than diploids under water-restricted growing conditions. • Our results indicate that aridity is an important predictor of polyploid occurrence in B. distachyon, suggesting a possible adaptive origin of the cytotype segregation., (© 2011 The Authors. New Phytologist © 2011 New Phytologist Trust.)

Background and Aims: Although there is evidence that both allopolyploid and homoploid hybridization lead to rapid genomic changes, much less is known about hybrids from parents with different basic numbers without further chromosome doubling. Two natural hybrids, Narcissus × alentejanus (2n = 19) and N. × perezlarae (2n = 29), originated by one progenitor (N. cavanillesii, 2n = 28) and two others (N. serotinus, 2n = 10 and N. miniatus, 2n = 30, respectively) allow us to study how DNA content and composition varies in such hybrids., Methods: Flow cytometry measurements with two staining techniques, PI and DAPI, were used to estimate 2C values and base composition (AT/GC ratio) in 390 samples from 54 wild populations of the two natural hybrids and their parental species. In addition, 20 synthetic F(1) hybrid individuals were also studied for comparison., Key Results: Natural hybrids presented 2C values intermediate between those found in their parental species, although intra-population variance was very high in both hybrids, particularly for PI. Genome size estimated from DAPI was higher in synthetic hybrids than in hybrids from natural populations. In addition, differences for PI 2C values were detected between synthetic reciprocal crosses, attributable to maternal effects, as well as between natural hybrids and those synthetic F(1) hybrids in which N. cavanillesii acted as a mother., Conclusions: Our results suggest that natural hybrid populations are composed of a mixture of markedly different hybrid genotypes produced either by structural chromosome changes, consistent with classic cytogenetic studies in Narcissus, or by transposon-mediated events.

Understanding the population structure, population dynamics and processes that give rise to polyploidy and helps to maintain it is central to our knowledge of the evolution of asexual vertebrates. Previous studies revealed high genetic diversity and several reproductive pathways in the southern populations of the Squalius alburnoides hybrid complex. In contrast, lower genetic variability and the associated limited chance of introducing new genetic combinations may threaten the survival of the northern Mondego populations. We analysed the genetic diversity and structure of nine populations of S. alburnoides in the Iberian Peninsula using microsatellite loci to provide further insights on the evolutionary history of this complex. Special attention was given to the less-studied northern populations (Mondego and Douro basins). Marked population structure, a high frequency of private alleles and a high diversity of some biotypes in the Douro basin indicate that some northern populations may not be at high risk of extinction, contrary to what was expected. The genetic diversity found in the northern Douro populations contradicts the general trend of remarkable genetic impoverishment northwards that occurs in other species and regions. The results indicate the possible existence of a glacial refugium in the Rabaçal River, corroborating findings in other species of this region. Historical events seem to have affected the geographical patterns of genetic variability found among and within the northern and southern populations of this complex and contributed to different patterns of genome composition. Therefore, historical events might have a major role in the long-term persistence of some polyploid hybrid taxa.

Summary: *The micro-evolutionary mechanisms that drive large-scale radiations are not completely understood, partly because of a shortage of population-level studies aimed at identifying putative causes of rapid evolutionary change. The Dianthus broteri complex, representing the largest polyploid series known to date for any species in the genus (2x, 4x, 6x and 12x cytotypes), belongs to a lineage that was recently found to have diversified at unusually rapid rates. *We used a combination of genome sequencing (internal transcribed spacer (ITS), plus chloroplast DNA (cpDNA) regions trnH-psbA, psbA-trnK and trnK-matK) and amplified fragment length polymorphism (AFLP) fingerprinting in 25 populations to infer the evolutionary history of extant polyploid races. *The haplotype, ribotype and AFLP reconstructions showed a star-shaped arrangement suggesting a pattern of radiative evolution. The major, widespread haplotype occurred at all ploidy levels, whereas 20 minor haplotypes were restricted to single populations and cytotypes. In addition, AFLP analyses retrieved well-supported cytogeographic groups: six clades were clearly differentiated in terms of ploidy level and geography. Molecular data indicate that gene flow among different cytotypes is rare or nonexistent. *Our study supports a scenario of rapid diversification in carnations in which autopolyploidy and allopolyploidy, in interaction with geography and/or isolation, have played prominent roles.

Geographical isolation and polyploidization are central concepts in plant evolution. The hierarchical organization of archipelagos in this study provides a framework for testing the evolutionary consequences for polyploid taxa and populations occurring in isolation. Using amplified fragment length polymorphism and simple sequence repeat markers, we determined the genetic diversity and differentiation patterns at three levels of geographical isolation in Olea europaea: mainland-archipelagos, islands within an archipelago, and populations within an island. At the subspecies scale, the hexaploid ssp. maroccana (southwest Morocco) exhibited higher genetic diversity than the insular counterparts. In contrast, the tetraploid ssp. cerasiformis (Madeira) displayed values similar to those obtained for the diploid ssp. guanchica (Canary Islands). Geographical isolation was associated with a high genetic differentiation at this scale. In the Canarian archipelago, the stepping-stone model of differentiation suggested in a previous study was partially supported. Within the western lineage, an east-to-west differentiation pattern was confirmed. Conversely, the easternmost populations were more related to the mainland ssp. europaea than to the western guanchica lineage. Genetic diversity across the Canarian archipelago was significantly correlated with the date of the last volcanic activity in the area/island where each population occurs. At the island scale, this pattern was not confirmed in older islands (Tenerife and Madeira), where populations were genetically homogeneous. In contrast, founder effects resulted in low genetic diversity and marked genetic differentiation among populations of the youngest island, La Palma.

Polyploidy, hybridization and variation in mating systems are central issues for a deeper understanding of animal evolution. The Iberian species Squalius alburnoides represents an example combining all three phenomena. Previous studies showed that S. alburnoides populations are mainly composed of triploid and diploid hybrid forms (mainly females), and that the tetraploid forms are rare or absent. Both populations from the Douro drainage reveal a distinct scenario: tetraploid individuals represent 85.6-97.5% of the population, with no sex ratio bias observed. Based on the flow cytometry measurements of blood and spermatozoa cells, microsatellite loci and experimental crosses, we describe here, for the first time, two symmetric allotetraploid populations (CCAA) that resumed normal meiosis after undergoing intermediate processes of non-sexual reproduction to give rise to a new sexually reproducing polyploid species. Prezygotic (habitat selection and assortative mating) and postzygotic mechanisms (nonviable embryos) are responsible for the reproductive isolation from other forms of the S. alburnoides complex (e.g. CA, CAA). This example illustrates how hybrid polyploid complexes may lead to speciation.

Background and Aims: Hybridization is an important evolutionary phenomenon, and therefore a detailed understanding of the dynamics of interspecific gene flow and resulting morphological and genetic patterns is of widespread interest. Here hybridization between the polyploids Cardamine pratensis and C. raphanifolia at four localities is explored. Using different types of data, the aim is to provide simultaneous and direct comparisons between genotype and phenotype variation patterns in the studied hybrid populations., Methods: Evidence of hybridization has been gathered from morphology, molecular markers (amplified fragment length polymorphism and chloroplast DNA sequences), pollen viability, karyology and nuclear DNA content., Key Results: All data support extensive gene flow occurring in the hybrid populations. A wide range of morphological and genetic variation is observed, which includes both parental and intermediate types. Unbalanced pollen fertility and several ploidy levels are recorded., Conclusions: Incongruence reported between genotype and phenotype suggests that parental phenotypes are affected by introgression, and intermediate hybrid phenotypes can be genetically closer to one of the parents. Thus, it is evident that morphology, when used alone, can be misleading for interpreting hybridization, and critical evaluation of other data is needed.

Contrasts between related diploid and polyploid taxa can serve as windows into the evolution of sexual systems. A recent study of a moving diploid-polyploid contact zone explores this topic in novel ways.

Interspecific hybridization is recognized as a potentially destructive process that represents a major threat to biodiversity. The rate of population displacement by hybridization can be rapid, but underlying mechanisms are often obscure. One hypothesis is that a species may be driven to extinction by interspecific gene flow, or pollen swamping, when hybrids are inviable or sterile. Here, we document the rapid movement of two zones of contact between monoecious hexaploid and dioecious diploid populations of the wind-pollinated plant Mercurialis annua (Euphorbiaceae) in northeastern and northwestern Spain, where diploids have displaced hexaploids by about 80 and 200 km, respectively, over a period of four decades. By using experimental mating arrays, we show that hybridization is highly asymmetrical in favor of the diploids, mainly because they disperse substantially more pollen, as expected in a comparison between an obligate outcrosser and a facultative selfer. Self-fertilization, which is expected to reduce the proportion of sterile hybrids produced in mixed ploidy populations, allowed the hexaploids to avoid the effects of pollen swamping only slightly, and in a density-dependent manner. Our results thus provide a mechanistic explanation for the rapid movement of both contact zones of M. annua in Spain.

Background and Aims: Vella pseudocytisus subsp. paui (Cruciferae) is a narrow endemic plant to the Teruel province (eastern Spain), which is listed in the National Catalogue of Endangered Species. Two distinct ploidy levels (diploid, 2n = 34, and tetraploid, 2n = 68) have been reported for this taxon that belongs to the core subtribe Vellinae, a western Mediterranean group of shrubby taxa with a chromosome base number of x = 17. Allozyme and AFLP analyses were conducted (a) to test for the ploidy and putative palaeo-allopolyploid origin of this taxon, (b) to explore levels of genetic diversity and spatial structure of its populations, and (c) to address in-situ and ex-situ strategies for its conservation., Methods: Six populations that covered the entire geographical range of this taxon were sampled and examined for 19 allozyme loci and three AFLP primer pair combinations. In addition, the gametic progenies of five individuals were analysed for two allozyme loci that showed fixed heterozygosity., Key Results: Multiple banded allozyme profiles for most of the surveyed loci indicated the polyploidy of this taxon. Co-inherited fixed heterozygous patterns were exhibited by the gametophytic tissues of the mother plants. Both allozyme and AFLP markers detected high levels of genetic diversity, and a strong micro-spatial genetic structure was recovered from AFLP phenetic analyses and Mantel correlograms., Conclusions: Allozyme data support the hypothesis of an allotetraploid origin of Vella pseudocytisus subsp. paui that could be representative of other taxa of the core Vellinae group. AFLP data distinguished three geographically distinct groups with no genetic interaction among them. Allotetraploidy and outcrossing reproduction have probably contributed to maintenance of high levels of genetic variability of the populations, whereas habitat fragmentation may have enhanced the high genetic isolation observed among groups. In-situ microgenetic reserves and a selective sampling of germplasm stocks for ex-situ conservation of this taxon are proposed.

Gynogenesis was assessed by different methods in 2 families of gynogenetic offspring in turbot ( Scophthalmus maximus). Karyotype analysis in embryos and larvae demonstrated high accuracy in estimation of ploidy level, but performance was uneven given the low quality and number of plates obtained. The use of silver staining to estimate the number of nucleoli per nucleus resulted in a straightforward and easy method to evaluate the ploidy of the samples studied. However, the existence of a nucleolus organizer region polymorphism in turbot determined a small error in ploidy estimation, important when checking ploidy in specific individuals. The use of a set of 11 highly variable microsatellite loci proved to be a powerful method to confirm the exclusive maternal inheritance to gynogenetic offspring in turbot, with probabilities of detection of putative paternal genetic contribution above 99.99%.

Isozymes were the first widely used molecular markers in plant population analysis. They yielded valuable information on the amount and the structure of genetic variability. DNA technology has provided new types of markers based on DNA sequence, which make it possible to study polymorphisms in a much greater proportion of the genome. This is the reason why the use of isozymes is less popular nowadays. This effect would be justified if all markers provided the same type of information on polymorphism and genetic relationships among populations; otherwise, it would be necessary to use different markers to obtain the complete picture of the genetic structure of populations and species. In this study, we compared data of isozyme and RAPD markers in the populations of two tetraploid species of wild oats: Avena barbata populations collected in Argentina, and Avena murphyi populations collected in Spain and Morocco. The samples were evaluated for 9 isozymatic systems and 10 primers. The structure of genetic variability was studied using Nei's method, and the relationships between populations were estimated using Hedrick and Jaccard's similarities for isozymes and RAPDs, respectively. As expected, RAPDs were more polymorphic than isozymes, but the information obtained from both markers was weakly correlated. The various reasons for this observation are discussed, but our conclusion is that in order to study the structure of genetic variability, several types of markers should be used.

Avena barbata, a tetraploid grass, is much more widely adapted and successful in forming dense stands than its diploid ancestors. The success of such polyploids has often been attributed to heterosis associated with ability to breed true for a highly heterozygous state in which allelic differences between the parents are fixed in the polyploid by chromosome doubling. We have examined the relationship between genetic diversity and adaptedness for 14 allozyme loci in A. barbata and its diploid ancestors in samples collected from diverse habitats in Israel and Spain. The relationship varied from locus to locus: superior adaptedness was associated with genetic uniformity for five loci, in part with genetic uniformity and in part with genetic diversity (monomorphism for a single heteroallelic quadriplex) for one locus, and with allelic diversity in the form of heteroallelic quadriplexes combined with genotypic diversity in the form of complex polymorphisms among different homoallelic and/or heteroallelic quadriplexes for the eight remaining loci. These results indicate that allelic diversity fixed in nonsegregating form through chromosome doubling was an important factor in the evolution of adaptedness in A. barbata. However, it is unlikely that heterosis associated with heterozygosity contributed significantly to superior adaptedness in either the diploids or the tetraploid because virtually all loci (approximately 99%) were homozygous in the Avena diploids and tetraploid.