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1.
Ann Bot ; 124(2): 255-268, 2019 Sep 24.
Artigo em Inglês | MEDLINE | ID: mdl-31185073

RESUMO

BACKGROUND AND AIMS: Polyploidy is an important driver of plant diversification and adaptation to novel environments. As a consequence of genome doubling, polyploids often exhibit greater colonizing ability or occupy a wider ecological niche than diploids. Although elevation has been traditionally considered as a key driver structuring ploidy variation, we do not know if environmental and phenotypic differentiation among ploidy cytotypes varies along an elevational gradient. Here, we tested for the consequences of genome duplication on genetic diversity, phenotypic variation and habitat preferences on closely related diploid and tetraploid populations that coexist along approx. 2300 m of varying elevation. METHODS: We sampled and phenotyped 45 natural diploid and tetraploid populations of Arabidopsis arenosa in one mountain range in Central Europe (Western Carpathians) and recorded abiotic and biotic variables at each collection site. We inferred genetic variation, population structure and demographic history in a sub-set of 29 populations genotyped for approx. 36 000 single nucleotide polymorphisms. KEY RESULTS: We found minor effects of polyploidy on colonization of alpine stands and low genetic differentiation between the two cytotypes, mirroring recent divergence of the polyploids from the local diploid lineage and repeated reticulation events among the cytotypes. This pattern was corroborated by the absence of ecological niche differentiation between the two cytotypes and overall phenotypic similarity at a given elevation. CONCLUSIONS: The case of A. arenosa contrasts with previous studies that frequently showed clear niche differentiation between cytotypes. Our work stresses the importance of considering genetic structure and past demographic processes when interpreting the patterns of ploidy distributions, especially in species that underwent recent polyploidization events.

2.
Am J Bot ; 105(12): 1995-2007, 2018 12.
Artigo em Inglês | MEDLINE | ID: mdl-30552673

RESUMO

PREMISE OF THE STUDY: Genome duplication is associated with multiple changes at different levels, including interactions with pollinators and herbivores. Yet little is known whether polyploidy may also shape belowground interactions. METHODS: To elucidate potential ploidy-specific interactions with arbuscular mycorrhizal fungi (AMF), we compared mycorrhizal colonization and assembly of AMF communities in roots of diploid and tetraploid Centaurea stoebe s.l. (Asteraceae) co-occurring in a Central European population. In a follow-up greenhouse experiment, we tested inter-cytotype differences in mycorrhizal growth response by combining ploidy, substrate, and inoculation with native AMF in a full-factorial design. KEY RESULTS: All sampled plants were highly colonized by AMF, with the Glomeraceae predominating. AMF-community composition revealed by 454-pyrosequencing reflected the spatial distribution of the hosts, but not their ploidy level or soil characteristics. In the greenhouse experiment, the tetraploids produced more shoot biomass than the diploids did when grown in a more fertile substrate, while no inter-cytotype differences were found in a less fertile substrate. AMF inoculation significantly reduced plant growth and improved P uptake, but its effects did not differ between the cytotypes. CONCLUSIONS: The results do not support our hypotheses that the cytotype structure in a mixed-ploidy population of C. stoebe is mirrored in AMF-community composition and that ploidy-specific fungal communities contribute to cytotype co-existence. Causes and implications of the observed negative growth response to AMF are discussed.


Assuntos
Centaurea/genética , Centaurea/microbiologia , Micorrizas/crescimento & desenvolvimento , Diploide , Fertilizantes , Tetraploidia
3.
PLoS One ; 13(12): e0208307, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30576314

RESUMO

Habitats with alkaline edaphic substrates are often associated with plant speciation and diversification. The tribe Alysseae, in the family Brassicaceae, epitomizes this evolutionary trend. In this lineage, some genera, like Hormathophylla, can serve as a good case for testing the evolutionary framework. This genus is centered in the western Mediterranean. It grows on different substrates, but mostly on alkaline soils. It has been suggested that diversification in many lineages of the tribe Alysseae and in the genus Hormathophylla is linked to a tolerance for high levels of Mg+2 in xeric environments. In this study, we investigated the controversial phylogenetic placement of Hormathophylla in the tribe, the generic limits and the evolutionary relationships between the species using ribosomal and plastid DNA sequences. We also examined the putative association between the evolution of different ploidy levels, trichome morphology and the type of substrates. Our analyses demonstrated the monophyly of the genus Hormathophylla including all previously described species. Nuclear sequences revealed two lineages that differ in basic chromosome numbers (x = 7 and x = 8 or derived 11, 15) and in their trichome morphology. Contrasting results with plastid genes indicates more complex relationships between these two lineages involving recent hybridization processes. We also found an association between chloroplast haplotypes and substrate, especially in populations growing on dolomites. Finally, our dated phylogeny demonstrates that the origin of the genus took place in the mid-Miocene, during the establishment of temporal land bridges between the Tethys and Paratethys seas, with a later diversification during the upper Pliocene.


Assuntos
Álcalis/química , Brassicaceae/genética , Núcleo Celular/genética , Magnésio/química , Filogenia , Plastídeos/genética , Solo/química , Sequência de Bases , Teorema de Bayes , Brassicaceae/ultraestrutura , Cromossomos de Plantas/genética , Variação Genética , Haplótipos/genética , Funções Verossimilhança , Região do Mediterrâneo , Filogeografia , Ploidias , Ribossomos/genética , Especificidade da Espécie , Fatores de Tempo , Tricomas/ultraestrutura
4.
Zookeys ; (629): 51-81, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27920597

RESUMO

Morphological variation in three rarely collected European species of the genus Lasiochernes Beier, 1932 is thoroughly examined in the present study. Detailed descriptions of previously ignored morphological characters of Lasiochernes cretonatus Henderickx, 1998, Lasiochernes jonicus (Beier, 1929) and Lasiochernes pilosus (Ellingsen, 1910) are presented. The female of Lasiochernes cretonatus and the nymphs of Lasiochernes pilosus are described for the first time. Multivariate morphometric techniques (principal coordinate analysis and discriminant analyses) were employed to confirm morphological differentiation of the three Lasiochernes species and to identify the most reliable characters for their separation. The usefulness of particular body parts for species identification was evaluated. An identification key for the females of the Lasiochernes species studied is provided. Geographic distribution and habitat preferences of the three species are summarized.

5.
Am J Bot ; 103(7): 1348-57, 2016 07.
Artigo em Inglês | MEDLINE | ID: mdl-27206461

RESUMO

PREMISE OF THE STUDY: After decades of interest, the contribution of hybridization to ecological diversification remains unclear. Hybridization is a potent source of novelty, but nascent hybrid lineages must overcome reproductive and ecological competition from their parental species. Here, we assess whether hybrid speciation is advantageous over alternative modes of speciation, by comparing the geographical and ecological ranges and climatic niche evolutionary rates of stabilized allopolyploid vs. autopolyploids in the Alyssum montanum species complex. METHODS: We combined an extensive review of studies addressing the systematics and genetic diversity of A. montanum s.l., with flow cytometry and cloning of nuclear markers, to establish the ploidy level and putative hybrid nature of 205 populations. The respective geographic distribution and climatic niche evolution dynamics of the allo- and autopolyploids were investigated using multivariate analyses and comparative phylogenetic approaches. KEY RESULTS: As expected by theory, allopolyploids occur mainly along contact zones and are generally spatially overlapping with their diploid counterparts. However, they demonstrate higher rates of niche evolution and expand into different climatic conditions than those of their diploid congeners. In contrast, autopolyploids show lower rates of niche evolution, occupy ecological niches similar to their ancestors and are restricted to less competitive and peripheral geographic areas. CONCLUSIONS: Hybridization thus seems advantageous by promoting ecological niche evolution and more readily allowing escape from competitive exclusion.


Assuntos
Brassicaceae/genética , Variação Genética , Hibridização Genética , Ploidias , Evolução Biológica , Clima , Diploide , Ecologia , Geografia , Filogenia
6.
Ann Bot ; 113(5): 817-30, 2014 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-24577071

RESUMO

BACKGROUND AND AIMS: Recently formed allopolyploid species represent excellent subjects for exploring early stages of polyploid evolution. The hexaploid Cardamine schulzii was regarded as one of the few nascent allopolyploid species formed within the past ∼150 years that presumably arose by autopolyploidization of a triploid hybrid, C. × insueta; however, the most recent investigations have shown that it is a trigenomic hybrid. The aims of this study were to explore the efficiency of progenitor-specific microsatellite markers in detecting the hybrid origins and genome composition of these two allopolyploids, to estimate the frequency of polyploid formation events, and to outline their evolutionary potential for long-term persistence and speciation. METHODS: Flow-cytometric ploidy-level screening and genotyping by progenitor-specific microsatellite markers (20 microsatellite loci) were carried out on samples focused on hybridizing populations at Urnerboden, Switzerland, but also including comparative material of the parental species from other sites in the Alps and more distant areas. KEY RESULTS: It was confirmed that hybridization between the diploids C. amara and C. rivularis auct. gave rise to triploid C. × insueta, and it is inferred that this has occurred repeatedly. Evidence is provided that C. schulzii comprises three parental genomes and supports its origin from hybridization events between C. × insueta and the locally co-occurring hypotetraploid C. pratensis, leading to two cytotypes of C. schulzii: hypopentaploid and hypohexaploid. Each cytotype of C. schulzii is genetically uniform, suggesting their single origins. CONCLUSIONS: Persistence of C. schulzii has presumably been achieved only by perennial growth and clonal reproduction. This contrasts with C. × insueta, in which multiple origins and occasional sexual reproduction have generated sufficient genetic variation for long-term survival and evolutionary success. This study illustrates a complex case of recurrent hybridization and polyploidization events, and highlights the role of triploids that promoted the origin of trigenomic hybrids.


Assuntos
Evolução Biológica , Cardamine/genética , DNA de Plantas , Hibridização Genética , Repetições de Microssatélites , Poliploidia , Citometria de Fluxo , Marcadores Genéticos , Dados de Sequência Molecular , Filogenia , Análise de Sequência de DNA , Suíça
7.
Ann Bot ; 110(3): 615-27, 2012 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-22730023

RESUMO

BACKGROUND AND AIMS: In a mixed-ploidy population, strong frequency-dependent mating will lead to the elimination of the less common cytotype, unless prezygotic barriers enhance assortative mating. However, such barriers favouring cytotype coexistence have only rarely been explored. Here, an assessment is made of the mechanisms involved in formation of mixed-ploidy populations and coexistence of diploid plants and their closely related allotetraploid derivates from the Centaurea stoebe complex (Asteraceae). METHODS: An investigation was made of microspatial and microhabitat distribution, life-history and fitness traits, flowering phenology, genetic relatedness of cytotypes and intercytotype gene flow (cpDNA and microsatellites) in six mixed-ploidy populations in Central Europe. KEY RESULTS: Diploids and tetraploids were genetically differentiated, thus corroborating the secondary origin of contact zones. The cytotypes were spatially segregated at all sites studied, with tetraploids colonizing preferentially drier and open microhabitats created by human-induced disturbances. Conversely, they were rare in more natural microsites and microsites with denser vegetation despite their superior persistence ability (polycarpic life cycle). The seed set of tetraploid plants was strongly influenced by their frequency in mixed-ploidy populations. Triploid hybrids originated from bidirectional hybridizations were extremely rare and almost completely sterile, indicating a strong postzygotic barrier between cytotypes. CONCLUSIONS: The findings suggest that tetraploids are later immigrants into already established diploid populations and that anthropogenic activities creating open niches favouring propagule introductions were the major factor shaping the non-random distribution and habitat segregation of cytotypes at fine spatial scale. Establishment and spread of tetraploids was further facilitated by their superior persistence through the perennial life cycle. The results highlight the importance of non-adaptive spatio-temporal processes in explaining microhabitat and microspatial segregation of cytotypes.


Assuntos
Centaurea/genética , Diploide , Ecossistema , Hibridização Genética , Tetraploidia , Áustria , Evolução Biológica , Fluxo Gênico , Variação Genética , Filogeografia , Dinâmica Populacional , Eslováquia
8.
Am J Bot ; 98(11): 1887-904, 2011 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-22052961

RESUMO

PREMISE OF THE STUDY: The Apennine Peninsula, one of the three peninsulas of the European Mediterranean, is an important hotspot of genetic and species diversity, but studies devoted to plant evolution are still very scarce in this region. We studied the diploid-polyploid complex of Alyssum montanum-A. repens, focusing on Apennine and adjacent southwestern Alpine populations from southeastern France, with the aim of examining their taxonomic position and evolutionary patterns. METHODS: We employed AFLP markers and cpDNA sequences, along with cytotype determination using flow cytometry, and a multivariate morphometric approach. KEY RESULTS: The Italian and French populations formed two well-delimited groupings within the studied complex that were, in contrast to previous taxonomic treatments, clearly distinct from A. montanum. Populations from southeastern France represent A. orophilum, a previously described but abandoned species. Those from central and southern Italy correspond to A. diffusum, exhibiting high, geographically structured variation (central Apennines, Gargano, and southern Apennines/Calabria). This pattern coincides with hotspot refugial regions, in congruence with the "refugia-within-refugia" hypothesis, and is reflected here in the recognition of three subspecies within A. diffusum. CONCLUSIONS: We provide evidence for the presence of Mediterranean refugia for the studied Alyssum montanum-A. repens complex located in central and southern Italy, which, however, did not contribute to the postglacial colonization of Central Europe. Past extinctions, genetic bottlenecks, and recent expansion were inferred in Central Europe, while long-term accumulation of diversity as well as polyploidization occurred in the Apennines.


Assuntos
Brassicaceae/classificação , Brassicaceae/genética , Evolução Molecular , Variação Genética , Análise do Polimorfismo de Comprimento de Fragmentos Amplificados , DNA de Cloroplastos , França , Genética Populacional , Itália , Filogeografia , Poliploidia , Análise de Sequência de DNA
9.
Ann Bot ; 105(2): 249-64, 2010 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-20007978

RESUMO

BACKGROUND AND AIMS: Intraspecific ploidy-level variation is an important aspect of a species' genetic make-up, which may lend insight into its evolutionary history and future potential. The present study explores this phenomenon in a group of eastern Asian Cardamine species. METHODS: Plant material was sampled from 59 localities in Japan and Korea, which were used in karyological (chromosome counting) and flow cytometric analyses. The absolute nuclear DNA content (in pg) was measured using propidium iodide and the relative nuclear DNA content (in arbitrary units) was measured using 4,6-diamidino-2-phenylindole fluorochrome. KEY RESULTS: Substantial cytotype diversity was found, with strikingly different distribution patterns between the species. Two cytotypes were found in C. torrentis sensu lato (4x and 8x, in C. valida and C. torrentis sensu stricto, respectively), which displays a north-south geographical pattern in Japan. Hypotheses regarding their origin and colonization history in the Japanese archipelago are discussed. In Korean C. amaraeiformis, only tetraploids were found, and these populations may in fact belong to C. valida. C. yezoensis was found to harbour as many as six cytotypes in Japan, ranging from hexa- to dodecaploids. Ploidy levels do not show any obvious geographical pattern; populations with mixed ploidy levels, containing two to four cytotypes, are frequently observed throughout the range. C. schinziana, an endemic of Hokkaido, has hexa- and octoploid populations. Previous chromosome records are also revised, showing that they are largely based on misidentified material or misinterpreted names. CONCLUSIONS: Sampling of multiple populations and utilization of the efficient flow cytometric approach allowed the detection of large-scale variation in ploidy levels and genome size variation attributable to aneuploidy. These data will be essential in further phylogenetic and evolutionary studies.


Assuntos
Cardamine/citologia , Cardamine/genética , Genoma de Planta/genética , Cardamine/classificação , Cromossomos de Plantas/genética , Citometria de Fluxo , Japão , Coreia (Geográfico) , Poliploidia
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