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American Journal of Botany

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February 17, 2017: American Journal of Botany
Zhe Wang, Xin Liu, Maaike Y Bader, Defeng Feng, Weikai Bao
PREMISE OF THE STUDY: Tradeoffs among functional traits of vascular plants are starting to be better understood, but it is unclear whether bryophytes possess similar tradeoffs or how trait relationships, or the 'economic spectrum', differ between the two groups. METHODS: We determined functional-trait values [including shoot mass per area (SMA), light-saturated assimilation rate (Amass), dark respiration rate (Rdmass), N and P concentrations (Nmass and Pmass), and photosynthetic N and P use efficiency (PNUE and PPUE)] and their bivariate relationships for 28 bryophytes growing in a subalpine old-growth fir forest on the eastern Tibetan Plateau...
February 17, 2017: American Journal of Botany
Ignacio Escapa, Andrew Leslie
PREMISE OF THE STUDY: Plants preserved in different fossil modes provide complementary data concerning the paleobiology and evolutionary relationships among plant groups. New material from the Early Jurassic of Patagonia shows the importance of combining these sources of information, as we describe the first compression/impression fossils of Pararaucaria, a genus of the extinct conifer family Cheirolepidiaceae previously known from permineralized fossils. These fossils extend the temporal range of this genus and may allow its wider recognition in the fossil record...
February 17, 2017: American Journal of Botany
Shimpei Oikawa, Koya Suno, Noriyuki Osada
PREMISE OF THE STUDY: Leaf life span (LLS) has long been hypothesized to plastically increase with decreasing nitrogen (N) supply from soil to maximize N retention, carbon assimilation, and fitness; however, accumulating evidence shows no consistent trend. The apparent inconsistencies are explained by a recent model that assumes LLS has a hump-shaped quadratic response to the N-supply gradient. The available evidence mostly originates from comparisons of LLS at only two levels of N availability, and the hypothesis remains unanswered...
February 15, 2017: American Journal of Botany
Thais C De Barros, Giseli D Pedersoli, Juliana V Paulino, Simone P Teixeira
PREMISE OF THE STUDY: Pentaclethra and Dimorphandra (Leguminosae) have long been considered a possible enigmatic link between caesalpinioids and mimosoids because they both have an imbricate calyx and heteromorphic androecium, floral features that are rare among mimosoids but common among caesalpinioids. This study compared the developing flowers of Dimorphandra mollis and Pentaclethra macroloba to determine whether the shared floral conditions also have the same ontogenetic origin. METHODS: Buds of different sizes and flowers were processed for surface (scanning electron microscopy) and histological (light microscopy) examination...
February 15, 2017: American Journal of Botany
Melissa K Ha, Christopher T Ivey
PREMISE OF THE STUDY: Local ecological conditions influence the impact of species interactions on evolution and community structure. We investigated whether pollinator-mediated interactions between coflowering plants vary with plant density, coflowering neighbor identity, and flowering season. METHODS: We conducted a field experiment in which flowering time and floral neighborhood were manipulated in a factorial design. Early- and late-flowering Clarkia unguiculata plants were placed into arrays with C...
February 15, 2017: American Journal of Botany
William B Sanders, Asunción de Los Ríos
PREMISE OF THE STUDY: Lichen-forming fungi produce diverse vegetative tissues, some closely resembling those of plants. Yet it has been repeatedly affirmed that none is a true parenchyma, in which cellular compartments are subdivided from all adjacent neighbors by cross walls adjoining older cross walls. METHODS: Using transmission electron microscopy (TEM), we tested this assumption by examining patterns of septum formation in the parenchyma-like cortex of three lichens of different phylogenetic affinities: Sticta canariensis, Leptogium cyanescens, and Endocarpon pusillum...
February 15, 2017: American Journal of Botany
David M Spooner, Holly Ruess, Massimo Iorizzo, Douglas Senalik, Philipp Simon
PREMISE OF THE STUDY: We explored the phylogenetic utility of entire plastid DNA sequences in Daucus and compared the results with prior phylogenetic results using plastid and nuclear DNA sequences. METHODS: We used Illumina sequencing to obtain full plastid sequences of 37 accessions of 20 Daucus taxa and outgroups, analyzed the data with phylogenetic methods, and examined evidence for mitochondrial DNA transfer to the plastid (DcMP). KEY RESULTS: Our phylogenetic trees of the entire data set were highly resolved, with 100% bootstrap support for most of the external and many of the internal clades, except for the clade of D...
February 15, 2017: American Journal of Botany
Jannice Friedman, Katherine S Hart, Meghan C den Bakker
PREMISE OF THE STUDY: The stigmas of several species are touch sensitive and respond to pressure by closing. Previous research suggests that stigma closure could prevent self pollination within a flower during a pollinator's visit or enhance male function by increasing pollen export. Both factors could be favored in outcrossers, and neither would be beneficial in selfers. METHODS: We investigated variation in stigma-closing and the duration of closure in annual and perennial populations of the variable species Mimulus guttatus and whether four closely related selfing species (M...
February 15, 2017: American Journal of Botany
Melvin R Duvall, Shrirang R Yadav, Sean V Burke, William P Wysocki
PREMISE OF THE STUDY: We investigated the little-studied Arundinoideae/Micrairoideae clade of grasses with an innovative plastome phylogenomic approach. This method gives robust results for taxa of uncertain phylogenetic placement. Arundinoideae comprise ∼45 species, although historically was much larger. Arundinoideae is notable for the widely invasive Phragmites australis. Micrairoideae comprise nine genera and ∼200 species. Some are threatened with extinction, including Hubbardia, some Isachne spp...
February 9, 2017: American Journal of Botany
Keir M Wefferling, Sílvia Castro, João Loureiro, Mariana Castro, Daniela Tavares, Sara B Hoot
PREMISE OF THE STUDY: Unrecognized variation in ploidy level can lead to an underestimation of species richness and a misleading delineation of geographic range. Caltha leptosepala (Ranunculaceae) comprises a complex of hexaploids (6x), rare nonaploids (9x), and dodecaploids (12x), all with unknown distributions. We delineate the geographic distribution and contact zones of the cytotypes, investigate morphologies of cytotypes and subspecies, and discuss the biogeography and evolutionary history of the polyploid complex...
February 9, 2017: American Journal of Botany
Naoko Ishikawa, Hirokazu Takahashi, Mikio Nakazono, Hirokazu Tsukaya
PREMISE OF THE STUDY: The aboveground part of one-leaf plants (Gesneriaceae) consists of a unique shoot-like unit called a phyllomorph, which is composed of a growing lamina and one petiolode (a stem- and petiole-like organ). The phyllomorph has three meristems: a basal meristem (BM; involved in lamina growth), a petiolode meristem (PM; required for midrib and petiolode growth), and a groove meristem (GM; contributes to inflorescence and new phyllomorph development). Although the GM has a tunica-corpus structure like a conventional shoot apical meristem (SAM), the vegetative GM of a one-leaf plant does not form any organ primordia and has been considered a defective or suppressed SAM...
February 9, 2017: American Journal of Botany
Luis Abdala-Roberts, Víctor Parra-Tabla, Xoaquín Moreira, José Ramos-Zapata
PREMISE OF STUDY: The factors driving variation in species interactions are often unknown, and few studies have made a link between changes in interactions and the strength of selection. METHODS: We report on spatial variation in functional responses by a seed predator (SP) and its parasitic wasps associated with the herb Ruellia nudiflora. We assessed the influence of plant density on consumer responses and determined whether density effects and spatial variation in functional responses altered natural selection by these consumers on the plant...
February 9, 2017: American Journal of Botany
Leandro G Roser, Laura I Ferreyra, Mauricio Ewens, Juan C Vilardi, Beatriz O Saidman
PREMISE OF THE STUDY: Gene flow through dispersal of seeds and pollen is a fundamental determinant of spatial genetic structure (SGS) in natural populations of trees at different spatial scales. Within continuous populations, restrictions to gene flow should be manifested in a process of local genetic differentiation, known as isolation by distance. The present work examines the SGS of a Prosopis alba population in a patchy region where urban, forest, and agricultural areas coexist. The analysis discussed here expands our knowledge about the processes affecting the distribution of the genetic variability in populations of disturbed landscapes...
January 31, 2017: American Journal of Botany
Hans-Jürgen Ensikat, Adeel Mustafa, Maximilian Weigend
PREMISE OF THE STUDY: Plants of the family Loasaceae are characterized by a usually dense indument of various trichome types, including two basically different types of mineralized, unicellular trichomes (stinging hairs or setae and scabrid-glochidiate trichomes). Mineralized trichomes have long been known to have silicified or calcified walls, but recent studies demonstrated that trichomes of Loasaceae may also contain calcium phosphate. The current study investigates the distribution of different biominerals in the mineralized trichomes across several different taxa...
January 31, 2017: American Journal of Botany
Daniel Chamorro, Belén Luna, José M Moreno
PREMISE OF THE STUDY: Species differ in their temperature germination niche. Populations of a species may similarly differ across the distribution range of the species. Anticipating the impacts of climate variability and change requires understanding the differential sensitivity to germination temperature among and within species. Here we studied the germination responses of four hard-seeded Cistaceae seeders to a range of current and future temperatures. METHODS: Seeds were collected at sites across the Iberian Peninsula and exposed or not exposed to a heat shock to break dormancy, then set to germinate under four temperature regimes...
January 19, 2017: American Journal of Botany
Nora Mitchell, Paul O Lewis, Emily Moriarty Lemmon, Alan R Lemmon, Kent E Holsinger
PREMISE OF THE STUDY: Estimating phylogenetic relationships in relatively recent evolutionary radiations is challenging, especially if short branches associated with recent divergence result in multiple gene tree histories. We combine anchored enrichment next-generation sequencing with species tree analyses to produce a robust estimate of phylogenetic relationships in the genus Protea (Proteaceae), an iconic radiation in South Africa. METHODS: We sampled multiple individuals within 59 out of 112 species of Protea and 6 outgroup species for a total of 163 individuals, and obtained sequences for 498 low-copy, orthologous nuclear loci using anchored phylogenomics...
January 19, 2017: American Journal of Botany
Ivan Prieto, Isabelle Litrico, Cyrille Violle, Philippe Barre
PREMISE OF THE STUDY: Current ecological theory can provide insight into the causes and impacts of plant domestication. However, just how domestication has impacted intraspecific genetic variability (ITV) is unknown. We used 50 ecotypes and 35 cultivars from five grassland species to explore how selection drives functional trait coordination and genetic differentiation. METHODS: We quantified the extent of genetic diversity among different sets of functional traits and determined how much genetic diversity has been generated within populations of natural ecotypes and selected cultivars...
January 12, 2017: American Journal of Botany
Meng Wu, Jamicia Lewis, Richard C Moore
PREMISE OF THE STUDY: The red flesh of some papaya cultivars is caused by a recessive loss-of-function mutation in the coding region of the chromoplast-specific lycopene beta cyclase gene (CYC-b). We performed an evolutionary genetic analysis of the CYC-b locus in wild and cultivated papaya to uncover the origin of this loss-of-function allele in cultivated papaya. METHODS: We analyzed the levels and patterns of genetic diversity at the CYC-b locus and six loci in a 100-kb region flanking CYC-b and compared these to genetic diversity levels at neutral autosomal loci...
January 12, 2017: American Journal of Botany
Rachel Rock-Blake, Melissa K McCormick, Hope E A Brooks, Cynthia S Jones, Dennis F Whigham
PREMISE OF THE STUDY: Symbioses are almost universal, but little is known about how symbiont abundance can affect host performance. Many orchids undergo vegetative dormancy and frequent and protracted dormancy have been associated with population declines. If mycorrhizal fungi affect host plant performance, those effects are likely to alter patterns of vegetative dormancy. The goal of this study was to determine whether the abundance of mycorrhizal fungi is related to the likelihood of entering dormancy and whether fungal abundance varied with dormancy duration in the federally listed threatened orchid Isotria medeoloides...
January 6, 2017: American Journal of Botany
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