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American Journal of Botany

Michelle L Gaynor, D Blaine Marchant, Douglas E Soltis, Pamela S Soltis
PREMISE OF THE STUDY: Autopolyploidy, or whole-genome duplication within a species, leads to closely related cytotypes in one geographic location. One hypothesized mechanism by which autopolyploids become established is climatic niche divergence from their diploid progenitor. Here we tested this hypothesis in diploid, triploid, and tetraploid Galax urceolata (Diapensiaceae) and predicted the effects of climate change on the relative distributions of these cytotypes. METHODS: We investigated whether climatic niche divergence has shaped the current distributions of Galax urceolata cytotypes in eastern North America using climatic niche modeling, multivariate analyses of environmental space, and geographic range analyses...
September 21, 2018: American Journal of Botany
Rob Massatti, Matthew T Belus, Shahed Dowlatshahi, Gerard J Allan
PREMISE OF THE STUDY: Astragalus sect. Humillimi is distributed across the southwestern United States and contains two endangered taxa, A. cremnophylax var. cremnophylax and A. humillimus. The former was originally described from the South Rim of the Grand Canyon. Analysis of individuals discovered on the North Rim of the Grand Canyon yielded some evidence that the population represented a distinct species. To enable effective conservation, we clarify the group's taxonomy and characterize the genetic diversity of A...
September 17, 2018: American Journal of Botany
Brian L Dorsey, Timothy J Gregory, Chodon Sass, Chelsea D Specht
PREMISE OF THE STUDY: Recent estimates of crown ages for cycad genera (Late Miocene) challenge us to consider what processes have produced the extant diversity of this ancient group in such relatively little time. Pleistocene climate change has driven major shifts in species distributions in Mexico and may have led to speciation in the genus Dioon by forcing populations to migrate up in elevation, thereby becoming separated by topography. METHODS: We inferred orthologs from transcriptomes of five species and sequenced these in 42 individuals representing all Dioon species...
September 2018: American Journal of Botany
(no author information available yet)
No abstract text is available yet for this article.
September 2018: American Journal of Botany
(no author information available yet)
No abstract text is available yet for this article.
September 2018: American Journal of Botany
Julie Messier, Cyrille Violle, Brian J Enquist, Martin J Lechowicz, Brian J McGill
PREMISE OF THE STUDY: General relationships among functional traits have been identified across species, but the forces shaping these relationships remain largely unknown. Adopting an approach from evolutionary biology, we studied similarities and differences in intrapopulation trait correlations among locally co-occurring tree species to assess the roles of constraints, phylogeny, and the environmental niche in shaping multivariate phenotypes. We tested the hypotheses (1) that intrapopulation correlations among functional traits are largely shaped by fundamental trade-offs or constraints and (2) that differences among species reflect adaptation to their environmental niches...
September 2018: American Journal of Botany
Zoe A Panchen, Mark O Johnston
PREMISE OF THE STUDY: Plant phenological responses to climate change now constitute one of the best studied areas of the ecological impacts of climate change. Flowering time responses to climate change of wind-pollinated species have, however, been less well studied. A novel source of flowering time data for wind-pollinated species is allergen monitoring records. METHODS: We studied the male flowering time response to climatic variables of two wind-pollinated genera, Betula (Betulaceae) and Populus (Salicaceae), using pollen count records over a 17-year period...
September 2018: American Journal of Botany
Peter W Fritsch, Camille F Nowell, Lila S T Leatherman, Wei Gong, Boni C Cruz, Dylan O Burge, Alfonso Delgado-Salinas
PREMISE OF THE STUDY: The North American Cercis clade spans dry to mesic climates and exhibits complex morphological variation. We tested various proposed species classifications of this group and whether aspects of leaf morphology, particularly the "drip-tip" in some regional populations, are adaptive and/or linked with phylogeny. METHODS: We made measurements on over 1100 herbarium specimens from throughout North America and analyzed the data with univariate and multivariate approaches...
September 2018: American Journal of Botany
Tan Bao, Gwendolyn Roy, James F Cahill
PREMISE OF THE STUDY: The rapid leaf movement of Mimosa pudica is expected to be costly because of energetic trade-offs with other processes such as growth and reproduction. Here, we assess the photosynthetic opportunity cost and energetic cost of the unique leaf closing behavior of M. pudica. METHODS: In the greenhouse, we employed novel touch-stimulation machines to expose plants to one of three treatments: (1) untouched control plants; (2) plants touch-stimulated to close their leaves during the day to incur energetic costs associated with leaf movement and reduced photosynthesis; (3) plants touched at night to assess the effects of touch alone...
September 2018: American Journal of Botany
Ryoko Imaichi, Nobuko Moritoki, Hiroko Kato Solvang
PREMISE OF THE STUDY: The apical meristem generates indeterminate apical growth of the stem and root of vascular plants. Our previous examination showed that shoot apical meristems (SAMs) can be classified into two types based on plasmodesmatal networks (PNs), which are important elements in symplasmic signaling pathways within the apical meristem. Here, we examined the PNs of root apical meristems (RAMs) in comparison with those of SAMs. METHODS: Root apical meristems of 18 families and 22 species of lycophytes and euphyllophytes were analyzed...
September 2018: American Journal of Botany
Sarel Munitz, Yishai Netzer, Ilana Shtein, Amnon Schwartz
PREMISE OF THE STUDY: The stem of Vitis vinifera, a climbing vine of global economic importance, is characterized by both wide and narrow vessels and high specific hydraulic conductivity. While the effect of drought stress has been studied in 1- and 2-yr-old stems, there are few data documenting effects of drought stress on the anatomical structure of the mature, woody stem near the base of the vine. Here we describe mature wood anatomical responses to two irrigation regimes on wood anatomy and specific hydraulic conductivity in Vitis vinifera Merlot vines...
September 2018: American Journal of Botany
Gerardo Arceo-Gómez, Conchita Alonso, Tia-Lynn Ashman, Victor Parra-Tabla
PREMISE OF THE STUDY: There is growing interest in understanding plant-plant interactions via pollen transfer at the community level. Studies on the structure and spatial variability of pollen transfer networks have been valuable to this understanding. However, there is high variability in the intensity of sampling used to characterize pollen transfer interactions, which could influence network structure. To date, there is no knowledge of how sampling effort influences the richness of pollen on stigmas and thereby transfer interactions observed, nor how this may vary across species and study sites...
September 2018: American Journal of Botany
Li-Yaung Kuo, Xinping Qi, Hong Ma, Fay-Wei Li
PREMISE OF THE STUDY: Filmy ferns (Hymenophyllales) are a highly specialized lineage, having mesophyll one-cell layer thick and inhabiting particularly shaded and humid environments. The phylogenetic placement of Hymenophyllales has been inconclusive, and while over 87 whole fern plastomes have been published, none was from Hymenophyllales. To better understand the evolutionary history of filmy ferns, we sequenced the first complete plastome for this order. METHODS: We compiled a phylogenomic plastome data set encompassing all 11 fern orders, and reconstructed phylogenies using different data types (nucleotides, codons, and amino acids) and partition schemes (codon positions and loci)...
September 2018: American Journal of Botany
Andrew B Leslie, Jeremy Beaulieu, Garth Holman, Christopher S Campbell, Wenbin Mei, Linda R Raubeson, Sarah Mathews
PREMISE OF THE STUDY: Conifers are an important living seed plant lineage with an extensive fossil record spanning more than 300 million years. The group therefore provides an excellent opportunity to explore congruence and conflict between dated molecular phylogenies and the fossil record. METHODS: We surveyed the current state of knowledge in conifer phylogenetics to present a new time-calibrated molecular tree that samples ~90% of extant species diversity. We compared phylogenetic relationships and estimated divergence ages in this new phylogeny with the paleobotanical record, focusing on clades that are species-rich and well known from fossils...
September 2018: American Journal of Botany
Jessica L Allen, Sean K McKenzie, Robin S Sleith, S Elizabeth Alter
PREMISE OF THE STUDY: Lichenized fungi are evolutionarily diverse and ecologically important, but little is known about the processes that drive their diversification and genetic differentiation. Distributions are often assumed to be wholly shaped by ecological requirements rather than dispersal limitations. Furthermore, although asexual and sexual reproductive structures are observable, the lack of information about recombination rates makes inferences about reproductive strategies difficult...
September 2018: American Journal of Botany
Lee A Dyer
No abstract text is available yet for this article.
September 2018: American Journal of Botany
Kenji Suetsugu, Tamihisa Ohta, Ichiro Tayasu
PREMISE OF THE STUDY: The evolution of full mycoheterotrophy is one of the most interesting topics within plant evolution. The leafless orchid Cymbidium macrorhizon is often assumed to be fully mycoheterotrophic even though it has a green stem and fruit capsule. Here, we assessed the trophic status of this species by analyzing the chlorophyll content and the natural 13 C and 15 N abundance in the sprouting and the fruiting season. METHODS: The chlorophyll content was measured in five sprouting and five fruiting individuals of C...
September 2018: American Journal of Botany
Steven K Rice, Thomas A Gagliardi, Rebecca A Krasa
PREMISE OF THE STUDY: Nonvascular plants play important roles in exchange of water and heat at the soil-atmosphere interface. Differential evaporative cooling may cause temperature gradients within bryophyte canopies, influencing convective heat and mass transport. Understanding mechanisms that affect fluxes through moss layers should improve models of forest floor function. METHODS: A three-dimensional thermal imaging system measured temperature distributions within moss shoot systems that were used to explore relationships among canopy structure, temperature gradients, evaporation, and conductance to water vapor (gs )...
September 2018: American Journal of Botany
Wei Shi, Qiongdao Zhang, Xinghua Sui, Buhang Li, Fangliang He, Chengjin Chu
PREMISE OF THE STUDY: Habitat filtering and non-habitat processes are two major processes affecting spatial distributions of species. Because trees at different life stages perform differently, the life stage of tree species could play an important role in shaping the spatial distribution of species and community assembly. Here, we examined the possible changes of spatial distributions of species and evaluated the shifts in the relative importance of habitat filtering and non-habitat processes across life stages in a 50-ha subtropical forest plot in China...
September 2018: American Journal of Botany
Gar W Rothwell, Ignacio H Escapa, Alexandru M F Tomescu
No abstract text is available yet for this article.
August 2018: American Journal of Botany
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