American Journal of Botany最新文献

{"title":"Linking environmental and pollination-related factors to touch-sensitive stigma closure dynamics in Mazus miquelii","authors":"Xiao-Fang Jin,&nbsp;Tian Luo,&nbsp;Chun-Feng Yang,&nbsp;Zhong-Ming Ye","doi":"10.1002/ajb2.70174","DOIUrl":"10.1002/ajb2.70174","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Premise</h3>\u0000 \u0000 <p>Touch-sensitive stigmas (TSSs), specialized receptive structures in angiosperms, dynamically respond to mechanical stimulation or pollen deposition. The typical sequence comprises temporary closure, reopening, and permanent closure, which optimize pollen capture, retention, and fertilization success. However, the specific environmental and pollination-related factors regulating these phases are unexplored.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Methods</h3>\u0000 \u0000 <p>Here we systematically investigated the association of environmental (temperature and humidity) and pollination-related factors (amount of pollen deposited [load], position of pollen tube, and growth rate of pollen tube) with the temporal dynamics of stigma movements in <i>Mazus miquelii</i>, a species with TSS.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Results</h3>\u0000 \u0000 <p>Temporary closure and reopening were primarily associated with temperature and were independent of the pollen load. In contrast, permanent closure was strongly correlated with the pollen load and position and growth rate of pollen tube. Furthermore, temporary closure and reopening time were negatively correlated, although neither were significantly correlated with permanent closure time.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Conclusions</h3>\u0000 \u0000 <p>Rapid temporary closure and reopening events were primarily associated with environmental cues, whereas irreversible permanent closure was associated with pollination-related signals. These advances in our understanding of the ecological regulation of TSS behavior provide a foundation for future studies into the physiological and molecular mechanisms of touch sensitivity of stigmas.</p>\u0000 </section>\u0000 </div>","PeriodicalId":7691,"journal":{"name":"American Journal of Botany","volume":"113 3","pages":""},"PeriodicalIF":2.7,"publicationDate":"2026-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147375831","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":"Soil, competition, and niche shifts shape the floral mosaic of an annual plant diversity hotspot","authors":"Emma R. Fryer,&nbsp;Ryan O'Dell,&nbsp;Dena L. Grossenbacher,&nbsp;Alyssa Shon,&nbsp;Skyler McKinnon,&nbsp;Nishanta Rajakaruna","doi":"10.1002/ajb2.70171","DOIUrl":"10.1002/ajb2.70171","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Premise</h3>\u0000 \u0000 <p>Plant species with affinity for harsh substrates often have well-defined edaphic (soil) niches and are ideal for exploring questions of community assembly. Vertic clay soils are chemically and physically challenging to plant establishment and productivity, and annual plant communities associated with these soils of the San Joaquin Desert (California, USA) form a distinctive mosaic pattern of species that reflects differences in soil properties across the landscape.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Methods</h3>\u0000 \u0000 <p>We analyzed soil properties to determine how heterogeneous soils at two field sites in the San Joaquin Desert differed among the realized niches of 12 native annual forb species with an affinity for vertic clay soils. We then conducted a pot study with the same species to test if species differed in their realized and fundamental edaphic niches, and to examine the competition effects of an invasive annual grass (<i>Bromus rubens</i>) on these species’ edaphic niches.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Results</h3>\u0000 \u0000 <p>From our field study, we found some differences in the vertic clay soils between the realized niches of species at both sites. In our pot study, we found species had similar fundamental edaphic niche optima in our treatment soils and that several species’ competitive ability varied with the edaphic stress in our treatment soils. For some species, differences in competitive ability led to shifts in edaphic niche optima, likely contributing to more divergent realized niches.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Conclusions</h3>\u0000 \u0000 <p>The combination of competitive pressure and abiotic stress drove differences between the realized niche and fundamental niche for species in a novel, heterogeneous study system.</p>\u0000 </section>\u0000 </div>","PeriodicalId":7691,"journal":{"name":"American Journal of Botany","volume":"113 3","pages":""},"PeriodicalIF":2.7,"publicationDate":"2026-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13003719/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147363819","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":"Phylogenetic systematics of Juncaceae","authors":"Reed J. Kenny,&nbsp;Lenka Záveská Drábková,&nbsp;Daniel Potter","doi":"10.1002/ajb2.70166","DOIUrl":"10.1002/ajb2.70166","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Premise</h3>\u0000 \u0000 <p>Juncaceae has needed taxonomic revision for some time. Specifically, the genus <i>Juncus</i> s.l. is known to be paraphyletic because five small southern-hemisphere genera have been shown repeatedly to be nested within it. In 2022, a new classification was proposed, based on phylogenies built from one nuclear and three plastid regions sequenced across much of Juncaceae, meant to resolve the paraphyletic nature of <i>Juncus</i> s.l. It created six new genera and was criticized on the basis that the genera proposed are not necessarily monophyletic, given the limited nature of the phylogenetic analyses available and the fact that the generic circumscriptions draw heavily on the morphology-based classifications in the latest monograph of Juncaceae from 2002.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Methods</h3>\u0000 \u0000 <p>We used the Angiosperms 353 target capture probe set to assemble a data set consisting of hundreds of plastid and nuclear loci to assess the monophyly of the newly proposed genera of Juncaceae.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Results</h3>\u0000 \u0000 <p>The proposed genera mostly represent monophyletic groups, but the proposed genus <i>Juncinella</i> is nested within the proposed genus <i>Boreojuncus</i>. Additionally, <i>Juncinella capitata</i> was placed as sister to either <i>Luzula</i> or <i>Oreojuncus</i> and should be recognized as a monotypic genus. Finally, <i>Australojuncus cyperoides</i> and <i>Verojuncus chlorocephalus</i> were recovered outside of their morphologically assigned genera and require further investigation to be placed confidently.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Conclusions</h3>\u0000 \u0000 <p>We proposed taxonomic revisions to rectify the stated issues, but further research is necessary, particularly to correctly place the South African annual taxa in <i>Juncus</i> s.l.</p>\u0000 </section>\u0000 </div>","PeriodicalId":7691,"journal":{"name":"American Journal of Botany","volume":"113 3","pages":""},"PeriodicalIF":2.7,"publicationDate":"2026-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13003717/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147269556","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":"Seeds as space-time travelers: How does evolution balance the joint benefits and trade-offs of dormancy and dispersal?","authors":"Sofia Backlund,&nbsp;Sean Stankowski,&nbsp;Rosina Soler","doi":"10.1002/ajb2.70175","DOIUrl":"10.1002/ajb2.70175","url":null,"abstract":"&lt;p&gt;Seeds face a fundamental challenge: once released, they enter environments that are highly variable in both space and time. Their ability to establish depends on escaping stressful conditions and encountering environments that are suitable for growth. Two strategies allow seeds to navigate unpredictability (Figure 1). Dispersal moves them through space via wind, animals, water, or other vectors, whereas dormancy—defined here as the delay of germination through the programmed shutdown of embryonic metabolism and growth—allows seeds to disperse through time.&lt;/p&gt;&lt;p&gt;Although often treated as distinct processes, dispersal and dormancy are deeply intertwined. Theory shows that both strategies can act jointly to buffer populations against environmental variability and local extinctions (Buoro and Carlson, &lt;span&gt;2014&lt;/span&gt;). Dispersal and dormancy can also shape gene flow and population dynamics (Saastamoinen et al., &lt;span&gt;2018&lt;/span&gt;), yet their combined effects remain poorly understood. Dormancy can reduce kin competition and promote altruistic behavior (Twyman and Gardner, &lt;span&gt;2023&lt;/span&gt;), echoing classic insights on spatial dispersal (Hamilton and May, &lt;span&gt;1977&lt;/span&gt;).&lt;/p&gt;&lt;p&gt;However, much remains to be learned about how dormancy and dispersal allow seeds to navigate environmental heterogeneity through space and time, whether these strategies can be optimized by selection, and when a joint strategy, involving a combination of dormancy and dispersal, might be optimal. Here, we highlight a few open questions that we see as the most important.&lt;/p&gt;&lt;p&gt;Evolutionary models assume that dormancy and dispersal are heritable, yet empirical support for this is uneven. Studies show substantial genetic variation in the depth of dormancy (Clerkx et al., &lt;span&gt;2004&lt;/span&gt;), yet most evidence comes from model or cultivated species studied in controlled environments. This highlights the need for more estimates from natural populations. By contrast, the heritability of seed dispersal is poorly understood. Dispersal is more difficult to measure and likely has a complex genetic basis (Saastamoinen et al., &lt;span&gt;2018&lt;/span&gt;). A few experimental studies, mainly in wind- or animal-dispersed species, show genetic variation in dispersal-related traits, but direct heritability estimates remain rare (Johnson et al., &lt;span&gt;2019&lt;/span&gt;).&lt;/p&gt;&lt;p&gt;A clearer picture of the genetic architecture of dormancy and dispersal is also needed to predict their joint responses to selection (Conner, &lt;span&gt;2002&lt;/span&gt;). If dormancy and dispersal are underpinned by largely independent genetic architectures, then it is possible for selection to optimize them independently. However, if they have a shared genetic architecture, then underlying genetic correlations will cause selection on one trait to generate an indirect evolutionary response in the other, potentially constraining adaptation (Conner, &lt;span&gt;2002&lt;/span&gt;). Spatially explicit pedigree studies designed to infer parent-offspring rel","PeriodicalId":7691,"journal":{"name":"American Journal of Botany","volume":"113 3","pages":""},"PeriodicalIF":2.7,"publicationDate":"2026-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13003715/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147429556","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":"Contrasting effects of experimental warming in the initiation year and the flowering year on flower phenology of boreal understory species","authors":"Christa P. H. Mulder,&nbsp;Eileen P. Schaub,&nbsp;Pamela K. Diggle","doi":"10.1002/ajb2.70160","DOIUrl":"10.1002/ajb2.70160","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Premise</h3>\u0000 \u0000 <p>High-latitude plants initiate flower primordia at least 1 year before flowering. While impacts of rising temperatures on phenology in the flowering year are well studied, the effects of warmer temperatures in the initiation year (IY; the year before flowering) are virtually unknown.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Methods</h3>\u0000 \u0000 <p>At 19 sites in interior Alaska, we experimentally warmed flower primordia of seven boreal species in the initiation year, flowering year, or both and tracked flowering phenology in the flowering year for two cohorts. For two species (<i>Vaccinium uliginosum</i> and <i>Vaccinium vitis-idaea</i>), we also tracked developmental stages of flower primordia.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Results</h3>\u0000 \u0000 <p>Warming in the flowering year resulted in earlier flowering for four species (<i>V. vitis-idaea</i>, <i>Rhododendron groenlandicum</i>, <i>Viburnum edule</i>, and <i>Rosa acicularis</i>), and in no change for two (<i>V. uliginosum</i>, and <i>Rubus chamaemorus</i>; not testable in <i>Shepherdia canadensis</i>). In contrast, warming in the IY resulted in delayed flowering for three species (<i>S. canadensis</i>, <i>R. groenlandicum</i>, and <i>V. vitis-idaea</i>), and no change for the others. Consistent with this pattern, <i>V. vitis-idaea</i> flower primordia at the end of the IY summer were less developed in warmed plots than in control plots, but for <i>V. uliginosum</i> there was no difference. Comparing phenology across all sites and years, early-flowering species had advanced flowering phenology following warm IY conditions, while late-flowering species had negative or nonlinear responses, with delays under the warmest IY temperatures.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Conclusions</h3>\u0000 \u0000 <p>The likely mechanism for delayed flowering in late-flowering plants following warm IY summers is early cessation of bud development at the end of the IY growing season.</p>\u0000 </section>\u0000 </div>","PeriodicalId":7691,"journal":{"name":"American Journal of Botany","volume":"113 2","pages":""},"PeriodicalIF":2.7,"publicationDate":"2026-02-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://bsapubs.onlinelibrary.wiley.com/doi/epdf/10.1002/ajb2.70160","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146155575","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":"Origins of the Macaronesian flora: Dispersal and diversification shape a meta-archipelago","authors":"Jonathan P. Price,&nbsp;Carlos García-Verdugo,&nbsp;Maria M. Romeiras,&nbsp;Rüdiger Otto,&nbsp;Juli Caujapé-Castells,&nbsp;Miguel Menezes de Sequeira,&nbsp;José María Fernández-Palacios","doi":"10.1002/ajb2.70161","DOIUrl":"10.1002/ajb2.70161","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Premise</h3>\u0000 \u0000 <p>Ancestors of oceanic insular floras arrived via long-distance dispersal as a function of the geographic location, climatic habitats, and geologic age of the island. As a result, these floras comprise a mix of lineages, derived from distinct colonization events with different continental and insular origins.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Methods</h3>\u0000 \u0000 <p>We assembled distributional data for native plant species in four Macaronesian archipelagoes (Azores, Madeira, Canary Islands, and Cabo Verde). Drawing from phylogenetic studies, we assigned each endemic species to a lineage. Five regions represent where the closest relatives of these lineages occur: American, temperate northern Europe, Mediterranean, Saharan, and African. We then estimated the total number of colonization events to Macaronesia as a whole and each constituent archipelago deriving from each region.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Results</h3>\u0000 \u0000 <p>The distribution of the origins of native non-endemic lineages broadly reflects the range of climates available in a given archipelago, such that a habitat filter model best explains their distributions. In contrast, for endemic lineages, combinations involving the Mediterranean region predominate across all four archipelagoes. The most species-rich lineages most commonly originate in the Canaries and subsequently disperse to younger, more isolated archipelagoes, reflecting a progression rule pattern.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Conclusions</h3>\u0000 \u0000 <p>Different theoretical models apply depending on the scale of endemism. One pattern that transcended existing models involved instances where an archipelago that promotes ecological diversification serves as a stepping stone for the colonization of more distant archipelagoes that otherwise may not have been suitable for ancestral continental taxa, which we term the island springboard effect.</p>\u0000 </section>\u0000 </div>","PeriodicalId":7691,"journal":{"name":"American Journal of Botany","volume":"113 2","pages":""},"PeriodicalIF":2.7,"publicationDate":"2026-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146155591","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":"The sleeping giant needs coffee: Overlooked areas for integrating plant ecophysiology and evolutionary biology","authors":"Haley A. Branch","doi":"10.1002/ajb2.70164","DOIUrl":"10.1002/ajb2.70164","url":null,"abstract":"<p>Interpretations of evolutionary outcomes are limited without incorporation of physiological ecology, and ecophysiological interpretations would benefit from incorporating evolutionary perspectives. Although there has been a rise of studies in the last 20 years between these fields, evolutionary studies that incorporate plant physiology have largely focused on the same traits (e.g., flowering time, specific leaf area), neglecting cellular and developmental traits. This neglect is largely due to the high throughput demands in evolutionary studies and the lack of technological advancements in ecophysiology. However, this bias in measured traits has resulted in limiting our understanding of the evolution of plant form and function. On the other hand, most detailed studies on plant physiological and anatomical responses to the environment are either in applied sciences, focused on economically important plants, or examine model organisms rather than wild populations. These detailed ecophysiological studies generally do not incorporate evolutionary discourse, even though they often study adaptation. The aim of this synthesis is to offer a comprehensive resource, building upon previous works, for researchers to bridge the gap between ecophysiology and evolutionary ecology.</p>","PeriodicalId":7691,"journal":{"name":"American Journal of Botany","volume":"113 2","pages":""},"PeriodicalIF":2.7,"publicationDate":"2026-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://bsapubs.onlinelibrary.wiley.com/doi/epdf/10.1002/ajb2.70164","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146130805","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 effect of drought stress on the limits and costs of plasticity in floral longevity in response to pollinator decline","authors":"Caelen McCabe,&nbsp;Christina M. Caruso","doi":"10.1002/ajb2.70163","DOIUrl":"10.1002/ajb2.70163","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Premise</h3>\u0000 \u0000 <p>Declines in pollinator populations can reduce pollination services to plants, resulting in lower seed production. In response to these reductions, plants could increase the probability of pollinator visitation by plastically extending floral longevity. However, whether extended floral longevity increases seed production as pollinators decline depends on the limits to and costs of plasticity in longevity, both of which could be affected by drought stress.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Methods</h3>\u0000 \u0000 <p>To test whether drought stress affects the limits to and costs of plasticity in floral longevity in response to pollinator decline, we exposed <i>Lobelia siphilitica</i> to droughted and well-watered treatments and measured floral longevity and the number of seeds produced by flowers pollinated on day 1 vs. day 5 of the female phase. If floral longevity is shorter in the droughted treatment, then drought stress could limit the expression of extended longevity. If delaying pollination until day 5 reduces seed production more in the droughted treatment, then drought stress could increase the cost of extended longevity.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Results</h3>\u0000 \u0000 <p>The droughted treatment reduced floral longevity by ~18% but did not affect the number of seeds produced by flowers pollinated on day 1 vs. day 5. Instead, delaying pollination until day 5 reduced the number of seeds by ~24% in both the droughted and well-watered treatments.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Conclusions</h3>\u0000 \u0000 <p>Drought stress does not affect the cost of plasticity in floral longevity but could limit the expression of extended longevity. Consequently, whether extended floral longevity could increase seed production as pollinators decline may depend on human-induced changes in precipitation.</p>\u0000 </section>\u0000 </div>","PeriodicalId":7691,"journal":{"name":"American Journal of Botany","volume":"113 2","pages":""},"PeriodicalIF":2.7,"publicationDate":"2026-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://bsapubs.onlinelibrary.wiley.com/doi/epdf/10.1002/ajb2.70163","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146123620","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":"Pollinator-mediated fitness differences do not fully explain the maintenance of gynodioecy in Sidalcea campestris","authors":"Brooklyn A. Richards,&nbsp;Thomas N. Kaye,&nbsp;F. Andrew Jones","doi":"10.1002/ajb2.70154","DOIUrl":"10.1002/ajb2.70154","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Premise</h3>\u0000 \u0000 <p>The maintenance of gynodioecy, female and hermaphroditic coexistence in plants, requires females to have a reproductive advantage over hermaphrodites in offspring quality, quantity, or both. Pollinators can influence this by mediating the reproductive success of females and hermaphrodites. We measured differences in pollinator-mediated fitness components between female and hermaphroditic plants in <i>Sidalcea campestris</i> to evaluate the role of pollinator-mediated selection in maintaining gynodioecy.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Methods</h3>\u0000 \u0000 <p>We studied sex-biased pollinator dynamics across 28 gynodioecious populations of <i>S. campestris</i> and conducted pollen supplementation experiments in 20 of these populations. Using pollinator surveys and pollen supplementation experiments, we tested for differences in pollinator visitation rates, pollinator community composition, seed production, and pollen limitation between sexes.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Results</h3>\u0000 \u0000 <p>Hermaphrodites received an average of 2.24 times more visits than females, although pollinator community composition was similar for both sexes. The estimated average probability of female seed set was 1.7 times higher than hermaphrodites for open-pollinated flowers and 2.0 times higher for hand-pollinated flowers, providing evidence of a female reproductive advantage. Seed set in both sexes was pollen limited, and females were not more limited than hermaphrodites. Female pollen limitation was unaffected by population-level female frequency.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Conclusions</h3>\u0000 \u0000 <p>These results revealed complex pollinator-mediated fitness differences between females and hermaphrodites. While our study demonstrated that females achieve the expected reproductive advantage for cytonuclear gynodioecy, the lack of differential pollen limitation and frequency-dependent female fitness are inconsistent with expectations of stable gynodioecy. Additional environmental, ecological, and genetic factors may regulate population dynamics in this gynodioecious system.</p>\u0000 </section>\u0000 </div>","PeriodicalId":7691,"journal":{"name":"American Journal of Botany","volume":"113 2","pages":""},"PeriodicalIF":2.7,"publicationDate":"2026-02-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146103369","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":"Why six and seven are implausible ancestral angiosperm chromosome numbers","authors":"Susanne S. Renner","doi":"10.1002/ajb2.70162","DOIUrl":"10.1002/ajb2.70162","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Premise</h3>\u0000 \u0000 <p>There is an ongoing shift about how best to infer ancestral chromosome numbers in plants. From 1938 to 2020, this was done by focusing on meiotic counts in extant species and using them to infer a hypothetical base chromosome number for larger clades, even when not found empirically. Since 2017, comparative-genomic studies provide a different approach that focuses on syntenic blocks in chromosome-level genome assemblies. For flowering plants, the two approaches have yielded drastically different results, namely either a base number around <i>n</i> = 7 or instead around 16.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Methods</h3>\u0000 \u0000 <p>Here I review how hypothetical base numbers and an assumed general evolutionary progression from lower to higher numbers—ideas that go back to benchmark papers by G. L. Stebbins—have hampered botanists’ inference of plausible ancestral chromosome numbers.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Results</h3>\u0000 \u0000 <p>Model-based studies of chromosome number evolution into the 2020 s have perpetuated some of the traditional biases by constraining numbers near or at the root of angiosperm phylogenies to be low, which may explain the discrepancies between their low inferred ancestral number (e.g., <i>n</i> = 7) and the higher number inferred from in silico comparison of syntenic blocks in chromosome-level genome assemblies (<i>n</i> = 16).</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Conclusions</h3>\u0000 \u0000 <p>Data available at this point, including from chromosome counts in early-diverging lineages (which were not known in Stebbins's time), argue against the long-assumed general low-to-high trend for changes in chromosome number across flowering plants.</p>\u0000 </section>\u0000 </div>","PeriodicalId":7691,"journal":{"name":"American Journal of Botany","volume":"113 2","pages":""},"PeriodicalIF":2.7,"publicationDate":"2026-02-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146103406","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}