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American Journal of Botany

Jeremy B Yoder
Decades of research on the evolution of mutualism has generated a wealth of possible ways whereby mutually beneficial interactions between species persist in spite of the apparent advantages to individuals that accept the benefits of mutualism without reciprocating - but identifying how any particular empirical system is stabilized against cheating remains challenging. Different hypothesized models of mutualism stability predict different forms of coevolutionary selection, and emerging high-throughput sequencing methods allow examination of the selective histories of mutualism genes and, thereby, the form of selection acting on those genes...
October 18, 2016: American Journal of Botany
Jeff J Doyle
No abstract text is available yet for this article.
October 18, 2016: American Journal of Botany
Luis Abdala-Roberts, Johnattan Hernández-Cumplido, Luis Chel-Guerrero, David Betancur-Ancona, Betty Benrey, Xoaquín Moreira
PREMISE OF STUDY: Although there is increasing recognition of the effects of plant intraspecific diversity on consumers, the mechanisms by which such effects cascade-up to higher trophic levels remain elusive. METHODS: We evaluated the effects of plant (lima bean, Phaseolus lunatus) intraspecific diversity on a suite of insect herbivores (leaf-chewers, aphids, and seed-eating beetles) and their third trophic-level associates (parasitoids and aphid-tending ants)...
October 18, 2016: American Journal of Botany
Marta R Pereira, Cristian S Dambros, Charles E Zartman
PREMISE OF THE STUDY: Resource allocation is difficult to characterize in plants because of the challenges of quantifying gametes and propagules. We surveyed six sympatric, unisexual species in the family Calymperaceae (Bryophyta) to test for trade-offs in prezygotic sexual and asexual expression and density-dependent survivorship of female gametangia. METHODS: We tallied gametangial and asexual propagule output for 1820 shoots from 17 populations of six species at monthly intervals during one year (2010-2011) in a central Amazonian forest...
October 7, 2016: American Journal of Botany
Lynn S Adler, Lissa M Leege, Rebecca E Irwin
PREMISE OF THE STUDY: Floral evolution is frequently ascribed to selection by pollinators, but may also be shaped by antagonists. However, remarkably few studies have examined geographic mosaics in resistance to floral antagonists or the consequences for other floral interactions. METHODS: Gelsemium sempervirens experiences frequent nectar robbing in northern Georgia, but rarely in southern Georgia. We conducted common-garden experiments in both locations using genotypes from each region and measured robbing, pollinator attraction, floral attractive and defensive traits, and plant reproduction...
October 7, 2016: American Journal of Botany
David H Hembry, David M Althoff
Brood pollination mutualisms-interactions in which specialized insects are both the pollinators (as adults) and seed predators (as larvae) of their host plants-have been influential study systems for coevolutionary biology. These mutualisms include those between figs and fig wasps, yuccas and yucca moths, leafflowers and leafflower moths, globeflowers and globeflower flies, Silene plants and Hadena and Perizoma moths, saxifrages and Greya moths, and senita cacti and senita moths. The high reciprocal diversity and species-specificity of some of these mutualisms have been cited as evidence that coevolution between plants and pollinators drives their mutual diversification...
October 7, 2016: American Journal of Botany
Michael A Grillo, John R Stinchcombe, Katy D Heath
PREMISE OF THE STUDY: Resource mutualisms such as the symbiosis between legumes and nitrogen-fixing rhizobia are context dependent and are sensitive to various aspects of the environment, including nitrogen (N) addition. Mutualist hosts such as legumes are also thought to use mechanisms such as partner choice to discriminate among potential symbionts that vary in partner quality (fitness benefits conferred to hosts) and thus impose selection on rhizobium populations. Together, context dependency and partner choice might help explain why the legume-rhizobium mutualism responds evolutionarily to N addition, since plant-mediated selection that shifts in response to N might be expected to favor different rhizobium strains in different N environments...
September 26, 2016: American Journal of Botany
Anne M Royer, Matthew A Streisfeld, Christopher Irwin Smith
PREMISE OF THE STUDY: Speciation is a complex process that can be shaped by many factors, from geographic isolation to interspecific interactions. In Joshua trees, selection from pollinators on style length has been hypothesized to contribute to the maintenance of differentiation between two hybridizing sister species. We used population genomics approaches to measure the extent of genetic differentiation between these species, test whether selection maintains differences between them, and determine whether genetic variants associated with style length show signatures of selection...
September 26, 2016: American Journal of Botany
Georgiana May
No abstract text is available yet for this article.
September 26, 2016: American Journal of Botany
Glenn P Svensson, Robert A Raguso, Ramona Flatz, Christopher I Smith
PREMISE OF THE STUDY: The role of floral scent in facilitating reproductive isolation between closely related plants remains poorly understood. Yucca brevifolia and Yucca jaegeriana are pollinated by different moth species in allopatry, but in a narrow contact zone, pollinator-host specificity breaks down, resulting in hybridization between species. We explored the chemical basis for reproductive isolation and hybridization in these Joshua trees by characterizing the floral scent of each species in allopatry, analyzing scent profiles from trees in the contact zone, and matching these data with genotypic and phenotypic data...
August 30, 2016: American Journal of Botany
Adrian F Powell, Jeff J Doyle
PREMISE OF THE STUDY: Previous studies have shown that polyploidy can alter biotic interactions, and it has been suggested that these effects may contribute to the increased ability for colonization of new habitats shown by many allopolyploids. Little is known, however, about the effects of allopolyploidy, which combines hybridity and genome doubling, on symbiotic interactions with rhizobial bacteria. METHODS: We examined interactions of the allopolyploid Glycine dolichocarpa (designated T2) with novel rhizobial partners, such as might occur in a context of colonization, and compared these with the responses of its diploid progenitors, G...
August 25, 2016: American Journal of Botany
K Charlotte Jandér, Edward Allen Herre
PREMISE OF THE STUDY: Fig trees and their pollinators, fig wasps, present a powerful model system for studying mutualism stability: both partners depend on each other for reproduction, cooperation levels can be manipulated, and the resulting field-based fitness quantified. Previous work has shown that fig trees can severely reduce the fitness of wasps that do not pollinate by aborting unpollinated figs or reducing the number and size of wasp offspring. Here we evaluated four hypotheses regarding the mechanism of sanctions in four Panamanian fig species...
August 25, 2016: American Journal of Botany
David M Althoff
PREMISE OF THE STUDY: Specialized brood pollination systems involve both mutualism and antagonism in the overall interaction and have led to diversification in both plants and insects. Although largely known for mutualism, the role of the antagonistic side of the interaction in these systems has been overlooked. Specialization may be driven by plant defenses to feeding by the insect larvae that consume and kill developing plant ovules. The interaction among yuccas and yucca moths is cited as a classic example of the importance of mutualism in specialization and diversification...
August 23, 2016: American Journal of Botany
(no author information available yet)
No abstract text is available yet for this article.
September 2016: American Journal of Botany
Neil F Adams, Margaret E Collinson, Selena Y Smith, Marion K Bamford, Félix Forest, Panagiota Malakasi, Federica Marone, Dan Sykes
PREMISE OF THE STUDY: Fossilized seeds similar to Cissus (Vitaceae) have been recognized from the Miocene of Kenya, though some were previously assigned to the Menispermaceae. We undertook a comparative survey of extant African Cissus seeds to identify the fossils and consider their implications for the evolution and biogeography of Cissus and for African early Miocene paleoenvironments. METHODS: Micro-computed tomography (µCT) and synchrotron-based X-ray tomographic microscopy (SRXTM) were used to study seed morphology and anatomy...
September 2016: American Journal of Botany
Helen I Holmlund, Victoria M Lekson, Breahna M Gillespie, Nicole A Nakamatsu, Amanda M Burns, Kaitlyn E Sauer, Jarmila Pittermann, Stephen D Davis
PREMISE OF THE STUDY: California experienced severe drought between 2012 and 2016. During this period, we compared seasonal changes in tissue-water relations among eight fern species in the Santa Monica Mountains of southern California to elucidate differential mechanisms of drought survival and physiological performance during extreme water deficits. METHODS: We monitored seasonal changes in water potential (Ψmd) and dark-adapted chlorophyll fluorescence (Fv/Fm), assessed tissue-water relations including osmotic potential at saturation and the turgor loss point (Ψπ, sat and Ψπ, tlp), and measured, for two evergreen species, xylem-specific and leaf-specific hydraulic conductivity (Ks and Kl) and vulnerability of stem xylem to water stress-induced embolism (water potential at 50% loss hydraulic conductivity, Ψ50)...
September 2016: American Journal of Botany
Takahiro Yagame, Yuki Ogura-Tsujita, Akihiko Kinoshita, Koji Iwase, Tomohisa Yukawa
PREMISE OF THE STUDY: Few previous studies have examined how mycobionts change during the evolution from autotrophy to mycoheterotrophy based on phylogenetic hypotheses. Neottia (Orchidaceae) comprises leafy species that are autotrophic and related leafless mycoheterotrophic species, and the phylogenetic relationships among them have been clarified. Accordingly, Neottia is a suitable taxon for investigating the question above. Here we clarified the diversity of mycobionts in Neottia plants and elucidated changes in the character of symbiotic associations during the evolution of mycoheterotrophy...
September 2016: American Journal of Botany
Guy W Atchison, Bruno Nevado, Ruth J Eastwood, Natalia Contreras-Ortiz, Carlos Reynel, Santiago Madriñán, Dmitry A Filatov, Colin E Hughes
PREMISE OF THE STUDY: The Andean highlands are a hotspot of domestication, yet our understanding of the origins of early Andean agriculture remains fragmentary. Key questions of where, when, how many times, and from what progenitors many Andean crops were domesticated remain unanswered. The Andean lupine crop tarwi (Lupinus mutabilis) is a regionally important pulse crop with exceptionally high seed protein and oil content and is the focus of modern breeding efforts, but its origins remain obscure...
September 2016: American Journal of Botany
Jonathan P Evans, Ashley B Morris
PREMISE OF THE STUDY: Sprouting in woody plant species allows for the long-term persistence of small, isolated populations experiencing changing environments and can preserve genetic diversity in these populations despite the infrequent recruitment of sexually produced individuals. We examined demographic data collected over a 10-yr period for Tilia americana var. caroliniana populations in the context of genetic structure as an empirical case study of this concept. METHODS: Two back-barrier islands on the Georgia coast of the United States were completely censused for Tilia americana var...
September 2016: American Journal of Botany
Kohtaroh Shutoh, Shingo Kaneko, Kenji Suetsugu, Yuichi I Naito, Takahide Kurosawa
PREMISE OF THE STUDY: Although the evolution of full mycoheterotrophy has attracted many plant researchers, molecular phylogenetic studies that focus on the transition from partial to full mycoheterotrophy are limited to a few taxa. Pyrola japonica sensu lato is an ideal model for examining the evolution of mycoheterotrophy, owing to its variable leaf size, which suggests that the species comprises several transitional stages. METHODS: To elucidate the molecular and morphological changes that occur during the evolutionary transition between partial and full mycoheterotrophy in P...
September 2016: American Journal of Botany
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