American Journal of Botany最新文献

{"title":"Exceptional anatomical preservation of Jurassic Austrohamia leaves from Patagonia reveals distinctive features of ancient Cupressaceae","authors":"Sebastian A. Molano,&nbsp;Giovanni C. Nunes,&nbsp;Ignacio H. Escapa,&nbsp;Josefina Bodnar,&nbsp;Juan L. García Massini,&nbsp;Diego Guido","doi":"10.1002/ajb2.70212","DOIUrl":"10.1002/ajb2.70212","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Premise</h3>\u0000 \u0000 <p>The Mesozoic fossil record of Cupressaceae is widespread and abundant, indicating that members of the family were dominant components of ancient ecosystems and that several cupressaceous lineages had higher species diversity in the past than they do today. Despite this extensive record, anatomical evidence remains critical to understanding the evolution of the group. This study provides new insights into the early evolutionary history of Cupressaceae and their adaptations to Jurassic environments through exceptionally preserved fossils from Patagonia.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Methods</h3>\u0000 \u0000 <p>Silicified leaves and twigs were collected from chert deposits at the Claudia and Cañadón Nahuel localities (La Matilde Formation, Santa Cruz Province). Samples were cut, polished, and analyzed using light microscopy and image-stacking techniques. Morphological, cuticular, and anatomical characters were compared with extant and fossil Cupressaceae to assess affinities.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Results</h3>\u0000 \u0000 <p>The leaves are dorsiventrally flattened and helically arranged with a semiplanar orientation. Anatomical features include a single abaxial resin canal and transfusion tissue surrounding the vascular bundle adaxially and expanding laterally into two rounded lobes. Cuticular traits include abaxial, monocyclic stomata with subsidiary cells resembling adjacent ordinary epidermal cells. These features align with <i>Austrohamia</i> and indicate affinity with Cupressaceae s.l.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Conclusions</h3>\u0000 \u0000 <p>The combination of vegetative, cuticular, and anatomical features supports assigning these Jurassic Patagonian fossils to <i>Austrohamia</i> and suggests a position near the root of Cupressaceae s.l. Their remarkable histological preservation provides new anatomical and biostratigraphic data, enhancing understanding of the early evolution of this family.</p>\u0000 </section>\u0000 </div>","PeriodicalId":7691,"journal":{"name":"American Journal of Botany","volume":"113 6","pages":""},"PeriodicalIF":2.8,"publicationDate":"2026-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147969629","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Two decades of resurrection studies: What have we learned about contemporary evolution of plant species?","authors":"Lillie K. Pennington,&nbsp;Seema N. Sheth,&nbsp;Steven J. Franks,&nbsp;Jill T. Anderson,&nbsp;Elena Hamann","doi":"10.1002/ajb2.70214","DOIUrl":"10.1002/ajb2.70214","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Premise</h3>\u0000 \u0000 <p>Global climate change has altered the eco-evolutionary trajectories of plant species, leading to observed shifts in phenotypes, such as earlier flowering. However, disentangling the contributions of plasticity and adaptation to trait changes remains challenging. The resurrection approach is a powerful method to study genetic and plastic responses by contrasting ancestral and descendant lineages from the same populations under common conditions.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Methods</h3>\u0000 \u0000 <p>We compiled a database of resurrection studies to examine plant evolutionary responses to global change using a meta-analysis (46 studies) and quantitative and qualitative review (61 studies). Studies varied widely in the number of focal populations and intervening years separating generations, yet most involved annual plant species in North America and Europe.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Results</h3>\u0000 \u0000 <p>We found evidence for rapid, contemporary evolution in over half of the cases. Moreover, evolution was often adaptive. As hypothesized, annuals showed greater magnitudes of evolutionary change than perennials. Across studies, annual descendants evolved earlier phenology and more resource-acquisitive leaf traits relative to ancestors. Under drought stress, annual and perennial species both evolved earlier phenology. Furthermore, in response to drought, annuals evolved increased plasticity in phenological and physiological traits but reduced plasticity in leaf traits, whereas perennials showed no evidence for evolution in plasticity.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Conclusions</h3>\u0000 \u0000 <p>Our study reveals that rapid evolution is common but not ubiquitous and highlights the key role of drought escape in plant responses to a warming world. Our review also suggests promising avenues for future resurrection research.</p>\u0000 </section>\u0000 </div>","PeriodicalId":7691,"journal":{"name":"American Journal of Botany","volume":"113 6","pages":""},"PeriodicalIF":2.8,"publicationDate":"2026-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/ajb2.70214","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148215977","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Fossil fruits of a new Attaleinae (Cocoseae, Arecaceae): Evidence of a palm grove community during the Early Miocene in northern Patagonia, Argentina","authors":"Luciana Muci,&nbsp;Mauro G. Passalia,&nbsp;Ari Iglesias","doi":"10.1002/ajb2.70220","DOIUrl":"10.1002/ajb2.70220","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Premise</h3>\u0000 \u0000 <p>Palms can develop a wide variety of fruit shapes and sizes. Species in the Cocoseae tribe possess an evident synapomorphy: the presence of three “eyes” or germination pores in their endocarp, probably best known by the widespread monotypic extant <i>Cocos nucifera</i>. There is little consensus on the biogeographic history of the cocosoid palms, there being few previous world-spread fossil records, some of which require further study in order to establish a clear taxonomic assignment.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Methods</h3>\u0000 \u0000 <p>Anatomy of permineralized fruits (pyrenes) from the Miocene in northern Patagonia, Argentina, was studied using thin sectioning and polished surfaces observed under transmitted and epifluorescence microscopy. Some fossils were analyzed under X-ray micro-tomography.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Results</h3>\u0000 \u0000 <p>We report a new palm fruit fossil record based on anatomical studies of &gt;30 specimens. These were assigned to a new fossil taxon within the subtribe Attaleinae (Tribe Cocoseae, Arecoideae). Furthermore, the presence of an unusual character as endocarp intrusions suggests a close anatomical relationship with the extant <i>Syagrus romanzoffiana</i>.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Conclusions</h3>\u0000 \u0000 <p>The new fossil taxon is one of the best-preserved fossils of the Cocoseae worldwide and is the first unambiguous fossil record for Attaleinae from southern South America. The extremely high concentration (hundreds to thousands) of pyrenes within several strata of the basal section of the Chichinales Formation and their wide distribution in the study area allow for the interpretation of a palm grove community. This record represents the most austral occurrence of the Attaleinae in South America, indicating that subtropical climatic conditions extended into northern Patagonia almost to the Early Miocene.</p>\u0000 </section>\u0000 </div>","PeriodicalId":7691,"journal":{"name":"American Journal of Botany","volume":"113 6","pages":""},"PeriodicalIF":2.8,"publicationDate":"2026-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148222647","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Exploring the lichenization continuum through the marine tripartite symbiosis of Collemopsidium pelvetiae","authors":"Sergio Pérez-Ortega,&nbsp;Rúdiger Ortiz-Álvarez,&nbsp;Jacek Wierzchos,&nbsp;Miguel Blázquez,&nbsp;Alain Gérault,&nbsp;Asunción de los Ríos","doi":"10.1002/ajb2.70210","DOIUrl":"10.1002/ajb2.70210","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Premise</h3>\u0000 \u0000 <p>Symbioses between lichen-forming fungi and brown algae (phaeophytes) are extremely rare. We investigated the interactions between the marine fungus <i>Collemopsidium pelvetiae</i> and its two photosynthetic partners, the brown alga <i>Pelvetia canaliculata</i> and a cyanobacterial symbiont to address questions on symbiosis biology, lichenization, and the diversity of fungal–photosynthetic associations in marine environments.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Methods</h3>\u0000 \u0000 <p>We combined light microscopy, fluorescence microscope in structural illumination microscopy mode (SIM), and transmission electron microscopy (TEM) to characterize thallus architecture, symbiont interfaces, and ultrastructural interactions. Amplicon-based 16S rRNA sequencing profiled cyanobacteria and heterotrophic bacteria from two regions (northern Spain and Brittany, France).</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Results</h3>\u0000 \u0000 <p><i>Collemopsidium pelvetiae</i> had distinct interactions with its two photosynthetic partners and with heterotrophic bacteria. Interactions with <i>Pelvetia canaliculata</i> were restricted to the region beneath the perithecia, where hyphae penetrated the outer amorphous cell-wall layer, without any evident host defense response. In contrast, the interaction with cyanobacteria involved the formation of intracellular haustoria, which ultimately lead to the death of the cyanobionts, suggesting a controlled parasitic relationship or a transitional stage toward lichenization. Unexpectedly, <i>C. pelvetiae</i> also produced haustorium-like projections into heterotrophic bacterial cells, a structure not previously reported in lichen symbioses. Microbiome analysis identified <i>Pleurocapsa</i> as the most likely cyanobiont genus associated with <i>C. pelvetiae</i> and revealed consistent heterotrophic bacterial communities, suggesting a species-specific assemblage.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Conclusions</h3>\u0000 \u0000 <p>This marine tripartite symbiosis involves distinct interaction modes, challenging strict lichen definitions. We propose that lichen symbioses form a multidimensional continuum of strategies rather than a single mutualistic model.</p>\u0000 </section>\u0000 </div>","PeriodicalId":7691,"journal":{"name":"American Journal of Botany","volume":"113 6","pages":""},"PeriodicalIF":2.8,"publicationDate":"2026-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/ajb2.70210","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148142513","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Long-term demography and spatial genetic structure reveal mechanisms of Sassafras albidum population persistence through clonality","authors":"J. T. Michel,&nbsp;Jonathan P. Evans,&nbsp;Skyler J. Fox,&nbsp;Ashley B. Morris","doi":"10.1002/ajb2.70215","DOIUrl":"10.1002/ajb2.70215","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Premise</h3>\u0000 \u0000 <p>Vegetative regeneration is a key mechanism of woody plant persistence in forest ecosystems, and the coupled roles of basal sprouting and clonal growth in shaping long-term population dynamics have been understudied. Basal sprouting replaces stems at fixed ramet locations, whereas clonal growth via root suckering produces spatially distinct ramets that promote genet-level persistence across space. <i>Sassafras albidum</i>, a clonal understory tree native to eastern North America, employs both mechanisms, making it an excellent system for evaluating how sprouting and clonality interact to structure populations.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Methods</h3>\u0000 \u0000 <p>We combined over two decades of demographic data with spatially explicit microsatellite analyses to examine population structure, spatial genetic organization, and persistence mechanisms in an upland oak–hickory forest on the Cumberland Plateau, Tennessee.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Results</h3>\u0000 \u0000 <p>Within a 1-ha plot, we identified 31 genets, ranging from single-ramet individuals to large clones exceeding 100 ramets and spanning more than 8000 m². Clonal richness was low, indicating that most ramets were derived from clonal growth, yet clonal dominance was moderate to low, reflecting extensive intermingling of genets. Short and tall stems were spatially clustered and persistent through time, whereas intermediate stems were spatially and temporally unstable, revealing a demographic bottleneck. Genets differed markedly in their representation across size classes, indicating asynchronous demographic trajectories.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Conclusions</h3>\u0000 \u0000 <p>We propose that the combined effects of basal sprouting and clonal growth generate persistent regenerative ramet locations, allowing genets to maintain advance regeneration across heterogeneous environments. These processes decouple stem turnover from genet turnover and facilitate long-term persistence in resource-poor upland forests.</p>\u0000 </section>\u0000 </div>","PeriodicalId":7691,"journal":{"name":"American Journal of Botany","volume":"113 6","pages":""},"PeriodicalIF":2.8,"publicationDate":"2026-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/ajb2.70215","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148196903","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Linking community structure and climate vulnerability in desert plant assemblages of southern California.","authors":"Hector Zumbado-Ulate, Luis E Barrios, Danelle A Baronia, G Darrel Jenerette, Lynn C Sweet","doi":"10.1002/ajb2.70224","DOIUrl":"https://doi.org/10.1002/ajb2.70224","url":null,"abstract":"<p><strong>Premise: </strong>Desert plant assemblages in southern California provide an opportunity to link patterns of community structure with climate-driven vulnerability in a rapidly changing environment. California sustains an exceptionally diverse flora of approximately 4300 plant species, with 31% identified as endemic. However, desert ecosystems remain comparatively understudied, and additional work is needed to better understand how plant communities may respond to ongoing climate change.</p><p><strong>Methods: </strong>We compiled a large occurrence-only data set (~214,000 records) representing 1352 angiosperm species across the Coachella Valley, a heterogeneous region encompassing four desert ecoregions. Using spatial analyses, joint species distribution models, and ecological niche modeling, we evaluated patterns of community structure and projected changes in climatic suitability for representative species under future climate scenarios.</p><p><strong>Results: </strong>Plant diversity hotspots were strongly associated with steep elevational gradients, whereas cold spots were concentrated in lowland and environmentally extreme areas. Representative species exhibited strong co-occurrence patterns, capturing associations with 88% of annual species and 95% of perennial species. Invasive species occurrences were most frequent in highly populated areas across the study region. Future projections indicated substantial declines in suitable habitat for 90% of representative species, with many species predicted to shift northward within the Coachella Valley.</p><p><strong>Conclusions: </strong>Declines in representative species under future climate scenarios are likely to be accompanied by concurrent reductions in many co-occurring taxa. These findings provide a community-level perspective on climate vulnerability in desert plant assemblages and highlight the value of integrating community structure and species distribution models to assess ecological responses to climate change.</p>","PeriodicalId":7691,"journal":{"name":"American Journal of Botany","volume":" ","pages":"e70224"},"PeriodicalIF":2.8,"publicationDate":"2026-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148275624","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Hurricane disturbance and local temperature are associated with growth and disease patterns in the endangered Florida torreya.","authors":"Xingwen Loy, Ashlynn Smith, Lilly Anderson-Messec, Ian Sabo, John Evans, Joseph Stockert, Laurie Blackmore, Emily E D Coffey","doi":"10.1002/ajb2.70222","DOIUrl":"https://doi.org/10.1002/ajb2.70222","url":null,"abstract":"<p><strong>Premise: </strong>Climate refugia endemics have persisted through past environmental shifts, but their responses to modern severe weather remain poorly understood. Torreya taxifolia (Taxaceae), a critically endangered conifer endemic to steephead ravines of Florida and Georgia, has declined for decades due to fungal canker diseases. Hurricane Michael, a Category 5 storm in 2018, caused extensive forest damage in its refugial habitat. We investigated how natural variation in disturbance was linked to tree health and microclimatic conditions relevant to disease.</p><p><strong>Methods: </strong>We monitored the health and habitat of 40 wild T. taxifolia individuals for 4 years after the hurricane by measuring branch growth and mortality and temperature and light around each T. taxifolia. We assessed the abundance and area of fungal cankers. Hurricane disturbance was characterized using complementary metrics of forest structural change (basal area) and the size-weighted abundance of fallen and standing trees.</p><p><strong>Results: </strong>Tree fall was associated with increased branch growth when quantified with summed diameter at breast height (DBH) metrics, but not with basal area metrics. Neither metric of tree fall was significantly associated with branch mortality. Local temperatures were positively associated with canker abundance, though not with total canker area, and were not directly linked to measures of forest change.</p><p><strong>Conclusions: </strong>Hurricane disturbance was associated with short-term after-storm growth responses among surviving T. taxifolia individuals, while warmer local conditions were linked to increased canker disease symptoms. Together, these results suggest that torreya growth was more closely associated with neighborhood-scale disturbance intensity than with broad reductions in stand-level biomass.</p>","PeriodicalId":7691,"journal":{"name":"American Journal of Botany","volume":" ","pages":"e70222"},"PeriodicalIF":2.8,"publicationDate":"2026-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148275558","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"","authors":"","doi":"","DOIUrl":"","url":null,"abstract":"","PeriodicalId":7691,"journal":{"name":"American Journal of Botany","volume":"113 5","pages":""},"PeriodicalIF":2.7,"publicationDate":"2026-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148089226","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"","authors":"","doi":"","DOIUrl":"","url":null,"abstract":"","PeriodicalId":7691,"journal":{"name":"American Journal of Botany","volume":"113 5","pages":""},"PeriodicalIF":2.7,"publicationDate":"2026-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148089225","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"","authors":"","doi":"","DOIUrl":"","url":null,"abstract":"","PeriodicalId":7691,"journal":{"name":"American Journal of Botany","volume":"113 5","pages":""},"PeriodicalIF":2.7,"publicationDate":"2026-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148089227","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}