American Journal of Botany最新文献

{"title":"Beyond dry and fleshy: Hidden developmental and anatomical transitions in Solanaceae fruit evolution","authors":"Estefanía Elejalde-Baena,&nbsp;Santiago Pérez-Ospina,&nbsp;Natalia Pabón-Mora","doi":"10.1002/ajb2.70239","DOIUrl":"10.1002/ajb2.70239","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Premise</h3>\u0000 \u0000 <p>Classifying fruits based solely on mature morphology can obscure underlying developmental and anatomical diversity. Current fruit types described in Solanaceae inadequately capture the complexity of fruit evolution within the family.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Methods</h3>\u0000 \u0000 <p>We compared the anatomy of different fruit developmental stages across representative Solanaceae lineages encompassing dry, fleshy, and intermediate fruit types. We also optimized fruit types, cell division patterns, endocarp lignification, and mesocarp expansion in a recent Solanaceae phylogenetic framework to reconstruct evolutionary changes.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Results</h3>\u0000 \u0000 <p>Early pericarp organization and tissue patterning were found to be largely conserved across lineages of Solanaceae, regardless of the mature fruit type. Divergence among fruit types arose primarily from lineage-specific modifications in endocarp lignification, mesocarp expansion, and lacunae formation, which together determine fruit patterning. We identified fruits with intermediate anatomical features in <i>Lycianthes</i>, <i>Lycium</i>, and <i>Nolana</i>, that are characterized by discontinuous endocarp lignification or sclerosomes and mesocarp expansion. We identified contrasting anatomical bases for fruit dehiscence: Lineages outside Solanoideae rely on a continuously lignified endocarp, whereas members of Solanoideae have independent dehiscence mechanisms based on tissue tensions without endocarp lignification.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Conclusions</h3>\u0000 \u0000 <p>Solanaceae fruit diversity emerged through modifications of conserved developmental programs and independent evolution of novel anatomical mechanisms. The anatomical patterns and character optimizations support our interpretation that sclerosomes represent remnants of a formerly continuous lignified endocarp, indicating that fleshy fruit in the family may have evolved through developmental programs repressing lignification. Our findings highlight the importance of integrating anatomical and ontogenetic perspectives to better understand fruit evolution in the family.</p>\u0000 </section>\u0000 </div>","PeriodicalId":7691,"journal":{"name":"American Journal of Botany","volume":"113 8","pages":""},"PeriodicalIF":2.8,"publicationDate":"2026-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148597689","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":"Application of a novel schema for describing fossil fern foliage and investigating taxonomic and morphological change across the Cretaceous–Paleogene boundary in western North America","authors":"Fern B. Holian,&nbsp;Emily B. Sessa,&nbsp;Richard S. Barclay,&nbsp;Regan E. Dunn,&nbsp;Jacquelyn L. Gill,&nbsp;Kirk R. Johnson,&nbsp;S. Augusta Maccracken,&nbsp;Ian M. Miller,&nbsp;Jarmila Pittermann,&nbsp;Ellen D. Currano","doi":"10.1002/ajb2.70243","DOIUrl":"10.1002/ajb2.70243","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Premise</h3>\u0000 \u0000 <p>The Chicxulub asteroid impact at the Cretaceous–Paleogene (K–Pg) boundary triggered a mass extinction 66 million years ago. Ferns thrived in the aftermath of the extinction, evidenced by the well-documented “fern spore spike.” However, fern macrofossil records across the K–Pg boundary are less understood.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Methods</h3>\u0000 \u0000 <p>We analyzed 698 fern macrofossils from 19 Cretaceous and 83 Paleogene localities in the Raton (Colorado and New Mexico), Denver (Colorado), and Williston basins (North Dakota and Montana), grouping specimens into morphotypes using a newly developed descriptive schema. We examined familial affiliations and documented taxonomic and morphological turnover across the boundary. Additionally, herbivory and pathogen damage were categorized on each specimen.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Results</h3>\u0000 \u0000 <p>We identified 33 morphotypes: eight were found only in the Cretaceous, 12 in both the Cretaceous and Paleogene, and 13 only in the Paleogene. Two fern families were in the Cretaceous only, nine in both the Cretaceous and Paleogene, and five in the Paleogene only. Taxa that occur in both the Cretaceous and Paleogene occupied less morphospace than taxa that occur only in the Cretaceous or the Paleogene. Sixty-three specimens had herbivory or pathogen damage; one damage type was found in the Cretaceous only, nine in both the Cretaceous and Paleogene, and seven in the Paleogene only.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Conclusions</h3>\u0000 \u0000 <p>Our data indicate possible changes in morphotype composition, family representations, morphological disparity, and insect herbivory across the K–Pg boundary. This research is important for understanding K–Pg recovery dynamics, fern adaptation, and their relation to deep time and modern catastrophic events.</p>\u0000 </section>\u0000 </div>","PeriodicalId":7691,"journal":{"name":"American Journal of Botany","volume":"113 8","pages":""},"PeriodicalIF":2.8,"publicationDate":"2026-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/ajb2.70243","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148629342","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":"Seasonal variation in wind speed and oceanic salt spray favors delayed reproduction in coastal yellow monkeyflowers","authors":"Katherine Toll,&nbsp;Chloe Crockett,&nbsp;Lauren Tocci,&nbsp;David B. Lowry","doi":"10.1002/ajb2.70249","DOIUrl":"10.1002/ajb2.70249","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Premise</h3>\u0000 \u0000 <p>The optimal timing of reproduction depends on the relative risk and benefit of continued growth. These risks and benefits depend on the local environment, which varies seasonally. While temperature and water availability are well-studied selective agents on reproductive timing, less is known about other seasonally variable factors.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Methods</h3>\u0000 \u0000 <p>To test whether seasonal variation in wind and salt spray influences selection on reproductive timing, we manipulated flowering time and ocean exposure in a coastal environment. Flowering plants from 12 yellow monkeyflower populations that span a coastal-to-inland gradient were placed on a coastal bluff in spring and summer. Inland populations typically flower in spring, which is much windier than the summer months when coastal populations usually flower, other plants were protected from wind and salt spray, and the rest were exposed to wind and salt spray.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Results</h3>\u0000 \u0000 <p>In the windier spring cohort, individuals exposed to the ocean had severe necrosis and produced few flowers and seeds, while protected plants had little to no necrosis, producing more flowers and seeds than ocean-exposed plants. In the calmer summer cohort, individuals exposed to the ocean had less severe necrosis and produced comparable numbers of flowers as plants protected from the ocean. However, only coastal populations produced appreciable numbers of seeds when exposed to the ocean, consistent with prior evidence that coastal ecotypes are locally adapted.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Conclusions</h3>\u0000 \u0000 <p>Overall, these results suggest that seasonal variation in wind and salt spray is a key selective factor in coastal populations contributing to population differences in flowering time.</p>\u0000 </section>\u0000 </div>","PeriodicalId":7691,"journal":{"name":"American Journal of Botany","volume":"113 8","pages":""},"PeriodicalIF":2.8,"publicationDate":"2026-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/ajb2.70249","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148672949","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":"Genomics is modifying our concepts of evolution in homosporous and heterosporous vascular plants","authors":"Sylvia P. Kinosian","doi":"10.1002/ajb2.70248","DOIUrl":"10.1002/ajb2.70248","url":null,"abstract":"<p>Across the tree of life, and particularly within land plants, there is a wide diversity and disparity of genome structure. The most well-studied are angiosperms, comprising mostly small and dynamic genomes, with a history of ancient whole genome duplications. Genome structure and evolution have historically been less clear in ferns and lycophytes, and the origin of their large genomes and high chromosome numbers has been debated for decades, centering on differences in reproductive mode (heterospory and homospory). Klekowski (1973) hypothesized that homosporous ferns and lycophytes were mainly inbreeding and that polyploidy allowed for higher genetic diversity via homoeologous heterozygosity. In contrast, Haufler (1987) and others proposed that homosporous ferns and lycophytes had diploid inheritance and outcrossed frequently, a theory supported by genetic crossing, isozymes, and modern comparative genomic analyses. This article summarizes past and current theories on the mechanisms of genome evolution in homosporous plants, highlights the contributions of comparative genomics to this field in the past two decades, and discusses what we may be able to learn by considering the role of meiosis in heterosporous and homosporous fern and lycophyte genome structure.</p>","PeriodicalId":7691,"journal":{"name":"American Journal of Botany","volume":"113 8","pages":""},"PeriodicalIF":2.8,"publicationDate":"2026-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/ajb2.70248","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148711087","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":"Phylogenomic insights into the genus Tulipa (Liliaceae): Taxonomy, evolution, and biogeography","authors":"Brett Wilson,&nbsp;Maarten J. M. Christenhusz,&nbsp;Nathanael Walker-Hale,&nbsp;Natalya Beshko,&nbsp;Mariyo Boboev,&nbsp;Colin Clubbe,&nbsp;Davron Dekhkonov,&nbsp;Aibek Dolotbakov,&nbsp;Mehmet Firat,&nbsp;Thomas Freeth,&nbsp;Sjaak de Groot,&nbsp;Avni Hajdari,&nbsp;Georgy A. Lazkov,&nbsp;Ormon Sultangaziev,&nbsp;Komiljon S. Tojibaev,&nbsp;Ben J. M. Zonneveld,&nbsp;Kaiyrkul T. Shalpykov,&nbsp;Samuel F. Brockington","doi":"10.1002/ajb2.70232","DOIUrl":"10.1002/ajb2.70232","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Premise</h3>\u0000 \u0000 <p>Tulips are one of the best-known geophytes, but their taxonomy remains convoluted and their evolutionary history poorly understood. Here, we used plastid genomes to identify some issues with current classification, understand the diversification history of the genus, and identify potential species linked to historical cultivation.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Methods</h3>\u0000 \u0000 <p>We gathered a large number of tulip specimens from living collections, herbaria, and online sources and through extensive fieldwork to infer maximum likelihood phylogenies of the plastid genomes of <i>Tulipa</i> (Liliaceae), representing ~86% of accepted species alongside a range of occasionally accepted synonyms. We used BEAST and secondary calibration points to date the tree, before assessing the biogeographical history of the genus using BioGeoBEARS.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Results</h3>\u0000 \u0000 <p>Based on our results, we described a fifth subgenus, <i>Eduardoregelia</i>, and identified a range of species where our results do not align with current taxonomy. Our data suggests the genus diverged from a clade containing <i>Amana</i> and <i>Erythronium</i> around 32.5 million years ago (Mya), with the most recent common ancestor existing around 22.8 Mya in the broader Central Asia region, a period that saw rapid uplift of mountain ranges and associated aridification in the region. The genus primarily diversified in Central Asia with rapid radiations within the last 10 My, possibly as a response to further orogenesis. Several migrations outside of the ancestral region have occurred, primarily via the steppes of Kazakhstan and Russia and along the Caucasus and Iranian and Anatolian Mountains to the eastern Mediterranean region. We also provide evidence that the maternal lineage of the garden tulip involved several species including <i>T. scardica</i> and <i>T. suaveolens</i>.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Conclusions</h3>\u0000 \u0000 <p>Many tulip species present limited diagnostic characters, making their taxonomy difficult, compounded by their long use in horticulture and widespread hybridization, especially in gardens. We provide an up-to-date phylogenetic framework for this genus that may help resolve many taxonomic issues in the future, while highlighting further work to be done. We reinforce the importance of Central Asia in the evolutionary history of this genus and provide an important foundation for further study of <i>Tulipa</i> and more effective conservation of wild tulip species.</p>\u0000 </section>\u0000 </div>","PeriodicalId":7691,"journal":{"name":"American Journal of Botany","volume":"113 8","pages":""},"PeriodicalIF":2.8,"publicationDate":"2026-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/ajb2.70232","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148672904","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":"The biomechanical consequences of the internode biomass inequality in Phyllostachys culms","authors":"Xiaonan Liu,&nbsp;Linlin Lu,&nbsp;Guohua Liu,&nbsp;Christian F. Damgaard,&nbsp;Karl J. Niklas,&nbsp;Peijian Shi","doi":"10.1002/ajb2.70247","DOIUrl":"10.1002/ajb2.70247","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Premise</h3>\u0000 \u0000 <p>Node-internode modular units characterize the construction of many herbaceous stems such as those of bamboo culms, providing hydraulic conductance and mechanical support such that internode biomass inequality observed within a culm significantly influences growth and structural stability. However, this inequality has not been studied. Traditional metrics, such as the coefficient of variation (CV), and the Gini coefficient (GC), can obscure sources of variation.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Methods</h3>\u0000 \u0000 <p>To address this analytical gap, we used the performance equation (PE) and its generalized version (GPE) to fit the rotated and right-shifted Lorenz curve (RRLC) of the internode mass distribution to quantify the inequality of each of 835 culms of 14 <i>Phyllostachys</i> species. The adjusted root mean square error and corrected Akaike information criterion were used to compare contending equations. Based on the better model fit, the Lorenz asymmetry coefficient (LAC) was calculated to determine whether many large (or a few large) internodes contribute to the within-culm inequality of the internode mass distribution.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Results</h3>\u0000 \u0000 <p>The GPE was significantly better than the PE in describing the RRLC. The mean LAC was 0.6436 (±0.0273 SD), which was significantly greater than 0.5, indicating that the inequality in internode mass is primarily driven by many rather than a few large internodes.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Conclusions</h3>\u0000 \u0000 <p>These findings highlight a mechanical reinforcement strategy in bamboo whereby biomass is preferentially allocated to lower internodes to enhance flexural stiffness to deal with gravitational and wind-induced dynamic loads. The RRLC−LAC framework is shown to be effective in elucidating the biomass allocation strategies that balance growth with structural support.</p>\u0000 </section>\u0000 </div>","PeriodicalId":7691,"journal":{"name":"American Journal of Botany","volume":"113 8","pages":""},"PeriodicalIF":2.8,"publicationDate":"2026-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148683145","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":"Foliar salt spray exclusion and tissue tolerance underlie local adaptation to oceanic salt spray","authors":"Madison L. Plunkert,&nbsp;P. Camilla Durant,&nbsp;Katherine Egeler,&nbsp;David B. Lowry","doi":"10.1002/ajb2.70251","DOIUrl":"https://doi.org/10.1002/ajb2.70251","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Premise</h3>\u0000 \u0000 <p>Surviving the effects of oceanic salt spray is critical for plants in coastal ecosystems, yet the mechanisms of coastal plant resilience to salt spray are not well understood. We investigated mechanisms of salt spray adaptation by comparing five latitudinal pairs of yellow monkeyflower accessions locally adapted to coastal and inland habitats.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Methods</h3>\u0000 \u0000 <p>We measured sodium levels in coastal and inland leaves exposed to experimental salt spray in the laboratory and compared leaf surface traits that may contribute to differences in sodium uptake between ecotypes. We assayed tissue tolerance by allowing sodium to enter leaf discs through the cut edges and recording time to necrosis for coastal and inland accessions.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Results</h3>\u0000 \u0000 <p>The leaf surface of coastal accessions took up less sodium from the experimental salt spray than the inland accessions, which may contribute to local adaptation to oceanic salt spray in coastal habitats. Higher water content per unit leaf area and less water loss under salt spray further reduced sodium concentrations in salt-sprayed coastal leaves compared to inland accessions. The coastal ecotype also had greater tissue tolerance to sodium than the inland ecotype.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Conclusions</h3>\u0000 \u0000 <p>Coastal monkeyflowers employ salt spray exclusion and tissue tolerance mechanisms for salt spray resilience. Our results suggest that plant adaptation to coastal habitats may often involve the evolution of multiple mechanisms to survive stress imposed by oceanic salt spray.</p>\u0000 </section>\u0000 </div>","PeriodicalId":7691,"journal":{"name":"American Journal of Botany","volume":"113 8","pages":""},"PeriodicalIF":2.8,"publicationDate":"2026-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/ajb2.70251","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148784103","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":"Reproductive stages in lowbush blueberry (Vaccinium angustifolium) occur earlier with increasing temperature.","authors":"Jenna Floyd, Elise Cadiou, Alain G Belliveau, Zoe A Panchen, Terrell T Roulston, Zoë Migicovsky","doi":"10.1002/ajb2.70240","DOIUrl":"https://doi.org/10.1002/ajb2.70240","url":null,"abstract":"<p><strong>Premise: </strong>Climate change is altering the timing of many plant phenological events, yet most studies focus on flowering, with less attention given to later reproductive stages such as fruit development and ripening. Vaccinium angustifolium (lowbush blueberry) is an important perennial berry species that may be sensitive to these changes. Shifts in fruit availability could affect ecological interactions (e.g., with frugivores) and economic and cultural activities, including harvest timing.</p><p><strong>Methods: </strong>We examined digitized and physical herbarium specimens and crowd-sourced iNaturalist images of V. angustifolium. Each plant was scored into one or more of five phenological stages: bud, flower, fruit pre-veraison (green berries), fruit post-veraison (blue berries), and vegetative only. A total of 928 observations were retained, with plants spanning eight ecoregions across northeastern North America and dating from 1901 to 2023. We used multiple linear regression models to assess phenological responses to monthly temperature and shifts over time.</p><p><strong>Results: </strong>Warmer spring and early summer temperatures shifted the timing of all V. angustifolium reproductive stages earlier, with budding having the strongest response to temperature. In addition, we estimated a shift of approximately 7 days earlier in the timing of fruit pre-veraison over the last century.</p><p><strong>Conclusions: </strong>Lowbush blueberry has a strong phenological response to early season temperatures, and the development of green berries has shifted earlier over the last century. These findings contribute to a broader understanding of how reproductive phenology of V. angustifolium may respond to climate change, with potential ecological and socioeconomic impacts.</p>","PeriodicalId":7691,"journal":{"name":"American Journal of Botany","volume":" ","pages":"e70240"},"PeriodicalIF":2.8,"publicationDate":"2026-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148597356","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":"Taxonomic reassessment of fossil Sequoia and Protosequoia from the Upper Miocene of Central Honshu, Japan, with implications for leaf morphological variation in extant S. sempervirens","authors":"Shun Ikeda,&nbsp;Arata Momohara","doi":"10.1002/ajb2.70227","DOIUrl":"10.1002/ajb2.70227","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Premise</h3>\u0000 \u0000 <p>Since its emergence in the Mesozoic, <i>Sequoia</i> (Cupressaceae) has been considered to possess conserved leaf morphology. However, recent studies have shown that the leaves of extant <i>S. sempervirens</i> become smaller, with a scale form, with increasing tree height. The fossil-genus <i>Protosequoia</i> has a similar scale leaf morphology, but its relationship to co-occurring <i>Sequoia</i> fossils, which bear linear leaves, remains unresolved.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Methods</h3>\u0000 \u0000 <p>To resolve this relationship, we re-examined specimens of two fossil species of <i>Sequoia</i> and <i>Protosequoia</i> from the Upper Miocene of Japan, focusing on leaf epidermal morphology and vascular bundle structure in the bract–scale complexes of seed cones.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Results</h3>\u0000 \u0000 <p>We identified fossil specimens with two types of shoots that were preserved in organic connection, but they had previously been classified as different genera. As the leaf shape changed from linear to scale, stomatal orientation shifted from parallel to the midrib to irregular, and epidermal cells gradually became shorter. Seed cones contained fewer than 30 bract–scale complexes with rhombic distal surfaces marked by horizontal grooves. In cross section, scales had rhombically arranged vascular bundles and several abaxial resin canals. Seeds had broad wings, and male strobili were mostly spherical.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Conclusions</h3>\u0000 \u0000 <p>The connected shoots, which shift in leaf stomatal features, and similarities in reproductive structure of the fossils suggest that the two genera represent the same species. Therefore, we propose a new <i>Sequoia</i> species characterized by densely branched twigs bearing smaller scale leaves, possibly reflecting an adaptation to different climatic conditions, compared to other species.</p>\u0000 </section>\u0000 </div>","PeriodicalId":7691,"journal":{"name":"American Journal of Botany","volume":"113 7","pages":""},"PeriodicalIF":2.8,"publicationDate":"2026-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/ajb2.70227","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148306589","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":"A case of budding speciation in the California Floristic Province and infraspecific divergence in Abronia villosa","authors":"Eli J. Allen,&nbsp;Eric F. LoPresti,&nbsp;Matthew G. Johnson,&nbsp;Oscar M. Vargas","doi":"10.1002/ajb2.70234","DOIUrl":"10.1002/ajb2.70234","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Premise</h3>\u0000 \u0000 <p>Budding speciation occurs when peripheral populations adapt to local ecological conditions and “bud” off from a widespread progenitor species. Traditionally regarded as rare because of its sympatric and parapatric nature, budding speciation is largely understudied. Moreover, recent evidence signals that this type of speciation is prevalent in plants, especially in biodiversity hotspots. In this study, we tested for budding speciation in the narrow endemic <i>Abronia villosa</i> var. <i>aurita</i> from the California Floristic Province (CFP).</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Methods</h3>\u0000 \u0000 <p>We used high-resolution phylogenetics, biogeography, and niche modeling to test the predictions of budding speciation for <i>A. villosa</i> var. <i>aurita</i> from its putative progenitor, the more widespread <i>A. villosa</i> var. <i>villosa</i>. Specifically, we tested for nested phylogenetic relationships of sister taxa, asymmetrical range size, and ecological divergence.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Results</h3>\u0000 \u0000 <p>Our results revealed that <i>A. villosa</i> var. <i>aurita</i> is a recently budded taxon, which phylogenetically nested within another variety of the same species. <i>Abronia villosa</i> var. <i>aurita</i> showed a clear signal of niche divergence into a montane environment and signals of genetic structure between two geographically divided populations, indicating further local adaptation and divergence potential.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Conclusions</h3>\u0000 \u0000 <p>We elucidated a case of budding speciation in the CFP, adding evidence to a growing number of studies that support budding speciation as a prevalent driver of diversification in plants. Furthermore, our analyses uncovered a nuanced history of within-species divergence, illustrating the importance of bridging microevolutionary and macroevolutionary mechanisms.</p>\u0000 </section>\u0000 </div>","PeriodicalId":7691,"journal":{"name":"American Journal of Botany","volume":"113 7","pages":""},"PeriodicalIF":2.8,"publicationDate":"2026-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/ajb2.70234","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148395595","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}