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American Journal of Botany

Nicholas John Deacon, Jake Joseph Grossman, Anna Katharina Schweiger, Isabella Armour, Jeannine Cavender-Bares
PREMISE OF THE STUDY: Aspen groves along the Niobrara River in Nebraska have long been a biogeographic curiosity due to morphological differences from nearby remnant Populus tremuloides populations. Pleistocene hybridization between P. tremuloides and P. grandidentata has been proposed, but the nearest P. grandidentata populations are currently several hundred kilometers east. We tested the hybrid-origin hypothesis using genetic data and characterized putative hybrids phenotypically. METHODS: We compared nuclear microsatellite loci and chloroplast sequences of Niobrara River aspens to their putative parental species...
December 15, 2017: American Journal of Botany
Aysajan Abdusalam, Dunyan Tan, Shu-Mei Chang
PREMISE OF THE STUDY: Abiotic environmental factors are often considered to be important in the distribution and maintenance of variation in sexual systems in flowering plants. Associations between sexes and abiotic factors are well documented in dioecious systems, but much less is known about this relationship in other sexually polymorphic systems. Species that are highly variable in sexual expression and habitat distribution can provide insights into the role of abiotic factors in maintaining variation in sexual expression...
December 15, 2017: American Journal of Botany
Ghadeer Bukhari, Jingbo Zhang, Peter F Stevens, Wenheng Zhang
PREMISE OF THE STUDY: Observations of floral ontogeny indicated that floral organ initiation in pentapetalous flowers most commonly results in a median-abaxial (MAB) petal during early development, a median-adaxial (MAD) petal being less common. Such different patterns of floral organ initiation might be linked with different morphologies of floral zygomorphy that have evolved in Asteridae. Here, we provide the first study of zygomorphy in pentapetalous angiosperms placed in a phylogenetic framework, the goal being to find if the different patterns of floral organ initiation are connected with particular patterns of zygomorphy...
December 15, 2017: American Journal of Botany
Juan M Losada, Jose I Hormaza, Jorge Lora
PREMISE OF THE STUDY: The pawpaw, Asimina triloba, is an underutilized fruit crop native to North America that belongs to the mainly tropical, early-divergent family Annonaceae. Asimina is the only genus within the Annonaceae with species adapted to cold climates. A thorough analysis of its reproductive biology, specifically pollen-pistil interaction during the progamic phase, is essential to understand both its adaptation to cold climates and how to optimize its fertilization and fruit set...
December 7, 2017: American Journal of Botany
Charlotte Prieu, Hervé Sauquet, Pierre-Henri Gouyon, Béatrice Albert
PREMISE OF THE STUDY: Apertures in pollen grains are key structures of the wall, involved in pollen tube germination and exchanges with the environment. Aperture types in angiosperms are diverse, but pollen with one and three apertures (including monosulcate and tricolpate, respectively) are the two most common types. Here, we investigate the phylogenetic distribution in angiosperms of pollen with many round, scattered apertures called pantoporate pollen. METHODS: We constructed a morphological data set with species producing pantoporate pollen and representative angiosperm species with other pollen types, sampled from every angiosperm order, with a total of 1260 species distributed in 330 families...
December 7, 2017: American Journal of Botany
Dragomira N Markova, Jennifer J Petersen, Sarah E Yam, Adryanna Corral, Matthew J Valle, Wentao Li, Roger T Chetelat
PREMISE OF THE STUDY: Self-incompatibility (SI) prevents self-fertilization and reduces inbreeding. While SI is common in plants, transitions to self-compatibility (SC) occur frequently. Little is known about the genetic changes and evolutionary steps underlying these shifts. METHODS: In the Solanaceae, SI is gametophytic, with specificity determined by S-RNases in the pistil and S-locus F-box proteins (SLFs) in pollen. We examined the role of two pollen factors, Cullin1 (CUL1) and SLF-23, in SI → SC transitions in wild tomato species from the Arcanum species group (Solanum arcanum, S...
December 6, 2017: American Journal of Botany
Camila Martínez
PREMISE OF THE STUDY: The plant fossil record for the neotropics is still sparse and temporally discontinuous. The location and description of new fossil material are fundamental for understanding evolutionary and biogeographic patterns of lineages. A new fossil record of Passifloraceae from the late Eocene of Colombia is described in this study. METHODS: Plant fossils were collected from a new locality from the Eocene Esmeraldas Formation. Eighteen fossil seeds were selected, described, and compared with fossil and extant angiosperm seeds based on the literature and herbarium collections...
December 6, 2017: American Journal of Botany
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No abstract text is available yet for this article.
December 1, 2017: American Journal of Botany
Elsa A Cousins, Courtney J Murren
PREMISE OF THE STUDY: Studies on phenotypic plasticity and plasticity of integration have uncovered functionally linked modules of aboveground traits and seedlings of Arabidopsis thaliana, but we lack details about belowground variation in adult plants. Functional modules can be comprised of additional suites of traits that respond to environmental variation. We assessed whether shoot and root responses to nutrient environments in adult A. thaliana were predictable from seedling traits or population-specific geologic soil characteristics at the site of origin...
December 1, 2017: American Journal of Botany
Sybil G Gotsch, Kenneth Davidson, Jessica G Murray, Vanessa J Duarte, Danel Draguljić
PREMISE OF THE STUDY: Tropical Montane Cloud Forests (TMCFs) are important ecosystems to study and preserve because of their high biodiversity and critical roles in local and regional ecosystem processes. TMCFs may be particularly affected by changes in climate because of the narrow bands of microclimate they occupy and the vulnerability of TMCF species to projected increases in cloud base heights and drought. A comprehensive understanding of the structure and function of TMCFs is lacking and difficult to attain because of variation in topography within and across TMCF sites...
December 1, 2017: American Journal of Botany
Eric S Menges, Sarah J H Crate, Pedro F Quintana-Ascencio
PREMISE OF THE STUDY: Areas lacking dominant plants, or gaps, can support high diversity and specialist species. Previous chronosequence research in Florida rosemary scrub showed indistinct gap area patterns with fire and the dependence of certain species on gaps. We hypothesized that fire and gap size would affect extinction, colonization, diversity, and vegetation composition. METHODS: In 2011-12, we revisited gaps first sampled in 2003, recording vascular plant and ground lichen occurrence by species, gap area, and burn history...
December 1, 2017: American Journal of Botany
C Matt Guilliams, Kristen E Hasenstab-Lehman, Makenzie E Mabry, Michael G Simpson
PREMISE OF THE STUDY: American amphitropical disjunction (AAD) is an important but understudied New World biogeographic pattern in which related plants occur in extratropical North America and South America, but are absent in the intervening tropics. Subtribe Amsinckiinae (Boraginaceae) is one of the richest groups of plants displaying the AAD pattern. Here, we infer a time-calibrated molecular phylogeny of the group to evaluate the number, timing, and directionality of AAD events, which yields generalizable insights into the mechanism of AAD...
November 23, 2017: American Journal of Botany
Laura A Frost, Sarah McAdams Tyson, Patricia Lu-Irving, Nataly O'Leary, Richard G Olmstead
PREMISE OF THE STUDY: Verbenaceae originated and initially diversified in South America in wet forest habitats. They have diversified extensively in arid habitats in both South and North America. This study aims to understand the origin of the North American arid-land members of Verbenaceae. METHODS: A phylogenetic approach is used to examine four genera (Aloysia, Citharexylum, Glandularia, Verbena) in three distinct clades with representatives in North American deserts and disjunct South and North American distributions...
November 23, 2017: American Journal of Botany
Adam C Schneider, Abigail J Moore
PREMISE OF THE STUDY: Aphyllon is a clade of holoparasites that includes closely related North American and South American species parasitic on Grindelia. Both Aphyllon (Orobanchaceae) and Grindelia (Asteraceae) have amphitropical disjunctions between North America and South America; however, the timing of these patterns and the processes to explain them are unknown. METHODS: Chronograms for the Orobanchaceae and Grindelia and their relatives were constructed using fossil and secondary calibration points, one of which was based on the inferred timing of horizontal gene transfer from a papilionoid legume into the common ancestor of Orobanche and Phelipanche...
November 23, 2017: American Journal of Botany
Fabiano R Maia, Patricia S Sujii, Viviane Silva-Pereira, Renato Goldenberg
PREMISE OF THE STUDY: The genetic structure of organisms results from the interactions between life history traits and the ecological and demographic characteristics of the landscape that shape the intra- and interpopulation genetic variation in space and time. In this study, we used a species restricted to islands of grassland vegetation in southern Brazil to investigate the effects of its naturally fragmented distribution on diversity and genetic structure patterns. METHODS: Diversity and intra- and interpopulational genetic structure were analyzed using polymorphisms of eight nuclear microsatellite markers in 205 individuals of T...
November 22, 2017: American Journal of Botany
John J Schenk, Kelsey Saunders
PREMISE OF THE STUDY: A repeated pattern of American amphitropical disjunct species or sister species distributed on either side of the equator has long-fascinated botanists, but the modes of these disjunctions remain untested. We evaluated diaspore morphology to generate hypotheses on probable dispersal mechanisms. METHODS: The sizes and structures of diaspores, habit, habitat, distribution, and dispersal units were collected for 108 species from literature searches and herbarium specimens...
November 22, 2017: American Journal of Botany
Rachel B Spigler, Susan Kalisz
No abstract text is available yet for this article.
November 22, 2017: American Journal of Botany
Tamara Villaverde, Pablo González-Moreno, Francisco Rodríguez-Sánchez, Marcial Escudero
PREMISE OF THE STUDY: Bipolar species represent the greatest biogeographical disjunction on Earth, raising many questions about the colonization and adaptive processes behind such striking distribution. We investigated climatic niche differences of five Carex bipolar species in North and South America to assess niche shifts between these two regions. Moreover, we assessed potential distribution changes with future climate change. METHODS: We used 1202 presence data points from herbarium specimens and 19 bioclimatic variables to assess climatic niche differences and potential distributions among the five species using ordination methods and Maxent...
November 22, 2017: American Journal of Botany
Donald R Farrar, Mary C Stensvold
Peter Raven, in 1963, included two fern taxa of the genus Botrychium in his list of plant species exhibiting American amphitropical bipolar disjunctions. He attributed the southern hemisphere occurrences to post-Pleistocene long-distance dispersal from counterparts in the northern hemisphere, probably assisted by annual bird migrations between the disjunct areas. Using genetic evidence gathered through worldwide analyses of phylogenetic relationship in Botrychium, we now review and reconsider Raven's conclusions...
November 22, 2017: American Journal of Botany
Tamara Villaverde, Marcial Escudero, Santiago Martín-Bravo, Pedro Jiménez-Mejías, Isabel Sanmartín, Pablo Vargas, Modesto Luceño
Bipolar disjunct distributions are a fascinating biogeographic pattern exhibited by about 30 vascular plants, whose populations reach very high latitudes in the northern and southern hemispheres. In this review, we first propose a new framework for the definition of bipolar disjunctions and then reformulate a list of guiding principles to consider how to study bipolar species. Vicariance and convergent evolution hypotheses have been argued to explain the origin of this fragmented distribution pattern, but we show here that they can be rejected for all bipolar species, except for Carex microglochin Instead, human introduction and dispersal (either direct or by mountain-hopping)-facilitated by standard and nonstandard vectors-are the most likely explanations for the origin of bipolar plant disjunctions...
November 22, 2017: American Journal of Botany
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