1,721,003 research outputs found
FIGURE 3 in Carex ×payettei, a new hybrid of Carex sect. Racemosae described from subarctic Quebec, Canada (Cyperaceae)
No full textFIGURE 3. Distribution range of the studied parental species and hybrid in the Northern Québec and Labrador (north of 54°N). A, Carex atratiformis. B, Carex ×payettei. C, Carex media. Maps provided by the Flore nordique project, Herbier Louis-Marie (QFA), Laval University.Published as part of Cayouette, Jacques & Léveillé-Bourret, Étienne, 2021, Carex ×payettei, a new hybrid of Carex sect. Racemosae described from subarctic Quebec, Canada (Cyperaceae), pp. 139-148 in Phytotaxa 483 (2) on page 143, DOI: 10.11646/phytotaxa.483.2.6, http://zenodo.org/record/542069
FIGURE 2 in Carex ×payettei, a new hybrid of Carex sect. Racemosae described from subarctic Quebec, Canada (Cyperaceae)
No full textFIGURE 2. Perigynium beaks of the studied parental species and hybrid, in three vertical rows. A, Carex atratiformis (QFA 240451). B, Carex ×payettei (CAN 152624). C, Carex media (QFA 240538). Arrows indicate sharp barbs on the margins of the perigynium beak of Carex ×payettei.Published as part of Cayouette, Jacques & Léveillé-Bourret, Étienne, 2021, Carex ×payettei, a new hybrid of Carex sect. Racemosae described from subarctic Quebec, Canada (Cyperaceae), pp. 139-148 in Phytotaxa 483 (2) on page 142, DOI: 10.11646/phytotaxa.483.2.6, http://zenodo.org/record/542069
Challenge accepted: Evolutionary lineages versus taxonomic classification of North American shrub willows ( Salix )
No full textAbstract Premise The huge diversity of Salix subgenus Chamaetia/Vetrix clade in North America and the lack of phylogenetic resolution within this clade has presented a difficult but fascinating challenge for taxonomists to resolve. Here we tested the existing taxonomic classification with molecular tools. Methods In this study, 132 samples representing 46 species from 22 described sections of shrub willows from the United States and Canada were analyzed and combined with 67 samples from Eurasia. The ploidy levels of the samples were determined using flow cytometry and nQuire. Sequences were produced using a RAD sequencing approach and subsequently analyzed with ipyrad, then used for phylogenetic reconstructions (RAxML, SplitsTree), dating analyses (BEAST, SNAPPER), and character evolution analyses of 14 selected morphological traits (Mesquite). Results The RAD sequencing approach allowed the production of a well‐resolved phylogeny of shrub willows. The resulting tree showed an exclusively North American (NA) clade in sister position to a Eurasian clade, which included some North American endemics. The NA clade began to diversify in the Miocene. Polyploid species appeared in each observed clade. Character evolution analyses revealed that adaptive traits such as habit and adaxial nectaries evolved multiple times independently. Conclusions The diversity in shrub willows was shaped by an evolutionary radiation in North America. Most species were monophyletic, but the existing sectional classification could not be supported by molecular data. Nevertheless, monophyletic lineages share several morphological characters, which might be useful in the revision of the taxonomic classification of shrub willows
Plant-soil feedback and the maintenance of diversity in Mediterranean-climate shrublands
No full textSoil biota influence plant performance through plant-soil feedback, but it is unclear whether the strength of such feedback depends on plant traits and whether plant-soil feedback drives local plant diversity. We grew 16 co-occurring plant species with contrasting nutrient-acquisition strategies from hyperdiverse Australian shrublands and exposed them to soil biota from under their own or other plant species. Plant responses to soil biota varied according to their nutrient-acquisition strategy, including positive feedback for ectomycorrhizal plants and negative feedback for nitrogen-fixing and nonmycorrhizal plants. Simulations revealed that such strategy-dependent feedback is sufficient to maintain the high taxonomic and functional diversity characterizing these Mediterranean-climate shrublands. Our study identifies nutrient-acquisition strategy as a key trait explaining how different plant responses to soil biota promote local plant diversity.Fil: Teste, Francois. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi". Universidad Nacional de San Luis. Facultad de Ciencias Físico, Matemáticas y Naturales. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi"; Argentina. University of Western Australia; AustraliaFil: Kardol, Paul. Swedish University of Agricultural Sciences; SueciaFil: Turner, Benjamin L.. University of Western Australia; Australia. Smithsonian Tropical Research Institute; PanamáFil: Wardle, David A.. Swedish University of Agricultural Sciences; Suecia. Nanyang Technological University; SingapurFil: Zemunik, Graham. University of Western Australia; Australia. Smithsonian Tropical Research Institute; PanamáFil: Renton, Michael. University of Western Australia; AustraliaFil: Léveillé Bourret, Étienne. University of Western Australia; Australia. University of Montreal; Canad
Rhodoscirpus (Cyperaceae: Scirpeae), a new South American sedge genus supported by molecular, morphological, anatomical and embryological data
Full text linkIn its broadest sense, Scirpus consists of a heterogeneous assemblage of up to 250 species, but modern circumscriptions suggest that only 40–50 species are part of the genus. Despite a narrower definition of the genus, atypical species continue to be segregated from Scirpus with a common pattern being the removal of Southern Hemisphere taxa to other genera and tribes. In South America, the morphology of remaining Scirpus species also suggests that they are not closely related to Scirpus s.str., but most of these taxa are only known from their types, making a detailed analysis of their generic affinities difficult. One notable exception is Scirpus asper, a species that is relatively common in the mountains and adjacent lowlands of Peru south to Argentina. Although this species possesses features used in the circumscription of Scirpus, such as cauline leaves, flat leaf blades and anthelate inflorescences, it is known to differ from Scirpus s.str. by its Schoenus-type embryo, and most of its presumed allies are now placed in different genera (e.g., Scirpus analecti ≡ Cypringlea analecta; Scirpus giganteus ≡ Androtrichum giganteum). In this study, we use DNA sequence data from the plastid (matK, ndhF) and nuclear (ETS-1f) genomes to demonstrate that Scirpus asper is not closely related to Scirpus s.str., but sister to Phylloscirpus within the predominantly South American Zameioscirpus clade (Amphiscirpus, Phylloscirpus, Zameioscirpus). When combined with morphological, anatomical and embryological data, results indicate that S. asper is best treated as the sole species of a new monotypic genus, Rhodoscirpus. The implications of these results on the taxonomy of tribe Scirpeae are discussed.Fil: Léveillé Bourret, Étienne. University of Ottawa; CanadáFil: Donadío, Sabina. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Botánica Darwinion. Academia Nacional de Ciencias Exactas, Físicas y Naturales. Instituto de Botánica Darwinion; ArgentinaFil: Gilmour, Claire N.. University of Ottawa; CanadáFil: Starr, Julian R.. University of Ottawa; Canad
How belowground interactions contribute to the coexistence of mycorrhizal and non-mycorrhizal species in severely phosphorus-impoverished hyperdiverse ecosystems
Full text linkBackground: Mycorrhizal strategies are very effective in enhancing plant acquisition of poorly-mobile nutrients, particularly phosphorus (P) from infertile soil. However, on very old and severely P-impoverished soils, a carboxylate-releasing and P-mobilising cluster-root strategy is more effective at acquiring this growth-limiting resource. Carboxylates are released during a period of only a few days from ephemeral cluster roots. Despite the cluster-root strategy being superior for P acquisition in such environments, these species coexist with a wide range of mycorrhizal species, raising questions about the mechanisms contributing to their coexistence. Scope: We surmise that the coexistence of mycorrhizal and non-mycorrhizal strategies is primarily accounted for by a combination of belowground mechanisms, namely (i) facilitation of P acquisition by mycorrhizal plants from neighbouring cluster-rooted plants, and (ii) interactions between roots, pathogens and mycorrhizal fungi, which enhance the plants’ defence against pathogens. Facilitation of nutrient acquisition by cluster-rooted plants involves carboxylate exudation, making more P available for both themselves and their mycorrhizal neighbours. Belowground nutrient exchanges between carboxylate-exuding plants and mycorrhizal N2-fixing plants appear likely, but require further experimental testing to determine their nutritional and ecological relevance. Anatomical studies of roots of cluster-rooted Proteaceae species show that they do not form a complete suberised exodermis. Conclusions: The absence of an exodermis may well be important to rapidly release carboxylates, but likely lowers root structural defences against pathogens, particularly oomycetes. Conversely, roots of mycorrhizal plants may not be as effective at acquiring P when P availability is very low, but they are better defended against pathogens, and this superior defence likely involves mycorrhizal fungi. Taken together, we are beginning to understand how an exceptionally large number of plant species and P-acquisition strategies coexist on the most severely P-impoverished soils.Fil: Lambers, Hans. University of Western Australia; AustraliaFil: Albornoz, Felipe. State University of Oregon; Estados UnidosFil: Kotula, Lukasz. University of Western Australia; AustraliaFil: Léveillé Bourret, Étienne. University of Western Australia; Australia. University of Montreal; CanadáFil: Ranathunge, Kosala. University of Western Australia; AustraliaFil: Teste, Francois. University of Western Australia; Australia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Matemática Aplicada de San Luis ; ArgentinaFil: Zemunik, Graham. Smithsonian Tropical Research Institute; Panam
Evolution and Classification of the Cariceae-Dulichieae-Scirpeae Clade (Cyperaceae)
No full textFor over a century, the origins and mechanisms underlying the diversification of the enormous cosmopolitan genus Carex (>2,100 species; Cariceae, Cyperaceae or sedge family) have remained largely speculative. Although its unique morphology (e.g., unisexual flowers, perigynia) clearly indicated it was a natural group, it obscured its relationships to all other Cyperaceae because the morphological gap between it and the rest of the family was so wide. Consequently, no plausible sister group to Carex has ever been proposed. Early molecular analyses narrowed the problem by placing Carex within a strongly-supported clade with the enigmatic monospecific genus Khaosokia, and tribes Dulichieae and Scirpeae (hereafter CDS), a group consisting of 2,250 species, or approximately 41% of all Cyperaceae. However, poor taxonomic sampling and the limited number of molecular markers used in these studies meant that the sister group to Carex remained a mystery. The goals of this thesis were to resolve evolutionary relationships within the CDS clade, to identify the sister group to Carex, and to develop a new natural tribal classification of CDS that could be used in future biogeographic and comparative analyses of Carex and its relatives.
Initial phylogenetic analyses using two plastid markers (matK, ndhF) identified seven major CDS lineages, and suggested that Carex could be nested within a paraphyletic Scirpeae. However, backbone support for these relationships was low due to an ancient rapid radiation (~10 million years) followed by long divergence of the seven major lineages (~40 million years). The addition of conventional sequence-based markers from the plastid genome (rps16) and nuclear ribosomal region (ETS-1f, ITS) indicated that a traditional molecular approach would not resolve these key backbone nodes. Consequently, a recently developed flowering-plant-specific anchored enrichment probe kit targeting hundreds of conserved nuclear genes combined with next generation sequencing was used to resolve the CDS backbone.
Although the resulting phylogenomic dataset was able to resolve the CDS backbone with high support, the topology and branch lengths only reaffirmed the isolated position of Carex. However, comparative morphological analyses of specimens at key herbaria not only suggested that Sumatroscirpus, a rare genus thought to be endemic to Sumatra, could be sister to Carex, but they also provided an easily accessible site to collect DNA in Northern Vietnam. Subsequent phylogenetic analyses of plastid (matK, ndhF, rps16) and nuclear ribosomal (ETS-1f, ITS) markers strongly supported Sumatroscirpus as the sister to Carex, and molecular dating estimates suggested they shared a common ancestor in the late Eocene (~36 million years ago). Comparative studies and ancestral state estimates of key morphological characters were congruent with this hypothesis, suggesting that the perigynium is not unique to Carex, but in fact a synapomorphy shared with Sumatroscirpus. This means that the initial key innovation in the remarkable diversification of Carex is not the perigynium, but could be the release of mechanical constraints that permitted the evolution of the remarkable morphological diversity of Carex perigynia seen today.
A taxonomic revision of Sumatroscirpus revealed that this purportedly monospecific genus actually consisted of four species, and it extended its range over 2,400 km to the north into Northern Vietnam, Myanmar, and Southwestern China. The phylogenetic framework provided by the previous studies enabled a new tribal and generic classification of CDS to be proposed. Seven monophyletic tribes are recognised including four new tribes (Calliscirpeae, Khaosokieae, Sumatroscirpeae, Trichophoreae), and a new genus (Rhodoscirpus). Morphological synapomorphies are identified for all recognized tribes, and a worldwide treatment, including identification keys, is provided for Sumatroscirpus species, CDS genera, and Cyperaceae tribes
Rare species of dodder (Cuscuta L.; Convolvulaceae) in Quebec and a plea for their search in the wild
Full text linkWe report three rare dodders (Cuscuta L.) from Quebec: Buttonbush Dodder (Cuscuta cephalanthi Engelmann), Hazel Dodder (Cuscuta coryli Engelmann), and Smartweed Dodder (Cuscuta polygonorum Engelmann). Detailed descriptions of their morphological characteristics, ecology, and host range are discussed. The genus Cuscuta is severely under-collected in Quebec and elsewhere, and targetted fieldwork is needed to better assess the distribution and conservation status of the three rare (or overlooked) species reported here. An identification key to all Cuscuta species from Quebec is provided to aid botanists in accurately identifying these challenging species
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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