American Journal of Botany最新文献_第10页

Striking genetic homogeneity in the widespread South American bracken 广泛分布的南美洲蕨类植物具有惊人的遗传同质性。

IF 2.4 2区生物学 Q2 PLANT SCIENCES

American Journal of Botany

Pub Date : 2024-07-12 DOI: 10.1002/ajb2.16374

Agustina Yañez, Sylvia P. Kinosian, M. Mónica Ponce, Diego G. Gutierrez, Pedro B. Schwartsburd, Michael Sundue, Paul G. Wolf

Premise

Bracken (Pteridium, Dennstaedtiaceae) is a cosmopolitan genus of aggressive disturbance colonizers that are toxic to agricultural livestock. The taxonomy of Pteridium has been treated in multiple schemes, ranging from one to six species worldwide, with numerous subspecies and varieties. Recent work has focused on the worldwide distribution and systematics of the bracken fern, but South America has been poorly represented. We present the first continent-wide sampling and analysis of Pteridium esculentum, a Southern Hemisphere diploid species.

Methods

Within South America, P. esculentum has several morphotypes, distinguished into subspecies by variation in indument and lamina architecture. We used double digest restriction site-associated DNA sequencing (ddRADSeq) to assess the phylogenetic relationships of P. esculentum subspecies.

Results

We found a striking genetic homogeneity in the species, being able to support only two morphotypes from molecular data: P. e. arachnoideum and P. e. campestre. We had high confidence for shallow and deep phylogenetic relationships, but less support for relationships among crown groups.

Conclusions

We describe an east-west geographic pattern that would explain the relationships between populations; and, in contrast to previous studies, we detected differences with P. esculentum from Australia. These results will lay the foundations for studying variations in this species' behavior as a weed, as well as its impact on the production of agricultural livestock in South America.

前提：蕨类植物（Pteridium，Dennstaedtiaceae）是一种世界性的侵扰性定植属植物，对农业牲畜有毒。蕨类植物的分类有多种方案，在世界范围内有 1 到 6 种，还有许多亚种和变种。最近的研究主要集中在蕨类植物的全球分布和系统学方面，但对南美洲的研究很少。我们首次对南半球二倍体蕨类植物 Pteridium esculentum 进行了全大陆范围的取样和分析：在南美洲，P. esculentum 有多个形态型，根据毛被和叶片结构的变化分为亚种。我们使用双消化限制性位点相关 DNA 测序（ddRADSeq）来评估 P. esculentum 亚种的系统发育关系：结果：我们发现该物种具有显著的遗传同质性，分子数据只能支持两种形态：P. e. arachnoideum 和 P. e. campestre。我们对浅层和深层的系统发育关系有很高的信心，但对冠群间关系的支持度较低：结论：我们描述了一种东西向的地理模式，这种模式可以解释种群之间的关系；与之前的研究不同，我们发现了与来自澳大利亚的 P. esculentum 的差异。这些结果将为研究该物种作为杂草的行为变化及其对南美洲农业牲畜生产的影响奠定基础。

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引用次数: 0

High-intensity light promotes adaptive divergence of photosynthetic traits between sun-exposed and shaded populations in Saxifraga fortunei 高强度光促进了 Saxifraga fortunei 暴露于阳光和遮蔽于阳光的种群之间光合特性的适应性分化。

IF 2.4 2区生物学 Q2 PLANT SCIENCES

American Journal of Botany

Pub Date : 2024-07-12 DOI: 10.1002/ajb2.16371

Kana Magota, Eiji Gotoh, Shota Sakaguchi, Hajime Ikeda, Hiroaki Setoguchi

Premise

Light is essential for plants, and local populations exhibit adaptive photosynthetic traits depending on their habitats. Although plastic responses in morphological and/or physiological characteristics to different light intensities are well known, adaptive divergence with genetic variation remains to be explored. This study focused on Saxifraga fortunei (Saxifragaceae) growing in sun-exposed and shaded habitats.

Methods

We measured the leaf anatomical structure and photosynthetic rate of plants grown in their natural habitats and in a common greenhouse (high- and low-intensity light experimental sites). To assess differences in ecophysiological tolerance to high-intensity light between the sun and shade types, we evaluated the level of photoinhibition of photosystem II and the leaf mortality rate under high-intensity light conditions. In addition, population genetic analysis was conducted to investigate phylogenetic origins.

Results

Clear phenotypic differences were found between the sun and shade types despite their recent phylogenetic origin. The leaf anatomical structure and photosynthetic rate showed plastic changes in response to growing conditions. Moreover, the sun type had a well-developed palisade parenchyma and a higher photosynthetic rate, which were genetically fixed, and a lower level of photoinhibition under high-intensity light.

Conclusions

Our findings demonstrate that light intensity is a selective pressure that can rapidly promote phenotypic divergence between the sun and shade types. While phenotypic changes in multiple photosynthetic traits were plastic, genetic divergence in specific traits related to adaptation to high-intensity light would be fundamental for ecotypic divergence to different light regimes.

前提：光照对植物至关重要，当地种群会根据其栖息地的不同表现出适应性光合特征。虽然形态和/或生理特征对不同光照强度的可塑性反应已广为人知，但遗传变异带来的适应性差异仍有待探索。本研究的重点是生长在阳光照射和阴暗生境中的Saxifraga fortunei（虎耳草科）：方法：我们测量了在自然栖息地和普通温室（高强度和低强度光照实验场所）中生长的植物的叶片解剖结构和光合速率。为了评估遮阳和遮阴植物对高强度光照的生态生理耐受性差异，我们评估了高强度光照条件下光合系统 II 的光抑制水平和叶片死亡率。此外，我们还进行了种群遗传分析，以研究系统发育起源：结果：尽管阳光型和遮荫型的系统发育起源较近，但它们之间仍存在明显的表型差异。叶片解剖结构和光合速率随着生长条件的变化而发生可塑性变化。此外，在高强度光照下，向阳型具有发达的栅栏状实质和较高的光合速率，这些都是遗传固定的，而且光抑制水平较低：我们的研究结果表明，光照强度是一种选择性压力，可迅速促进阳光型和遮荫型之间的表型分化。虽然多种光合性状的表型变化是可塑的，但与适应高强度光有关的特定性状的遗传分化将是生态型分化适应不同光照制度的基础。

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引用次数: 0

Plastid genome evolution in leafless members of the orchid subfamily Orchidoideae, with a focus on Degranvillea dermaptera 兰花亚科兰属无叶植物的质体基因组进化，重点是Degranvillea dermaptera。

IF 2.4 2区生物学 Q2 PLANT SCIENCES

American Journal of Botany

Pub Date : 2024-07-11 DOI: 10.1002/ajb2.16370

Craig F. Barrett, Matthew C. Pace, Cameron W. Corbett

Premise

Leafless, heterotrophic plants are prime examples of organismal modification, the genomic consequences of which have received considerable interest. In particular, plastid genomes (plastomes) are being sequenced at a high rate, allowing continual refinement of conceptual models of reductive evolution in heterotrophs. However, numerous sampling gaps exist, hindering the ability to conduct comprehensive phylogenomic analyses in these plants.

Methods

Using floral tissue from an herbarium specimen, we sequenced and analyzed the plastome of Degranvillea dermaptera, a rarely collected, leafless orchid species from South America about which little is known, including its phylogenetic affinities.

Results

The plastome is the most reduced of those sequenced among the orchid subfamily Orchidoideae. In Degranvillea, it has lost the majority of genes found in leafy autotrophic species, is structurally rearranged, and has similar gene content to the most reduced plastomes among the orchids. We found strong evidence for the placement of Degranvillea within the subtribe Spiranthinae using models that explicitly account for heterotachy, or lineage-specific evolutionary rate variation over time. We further found evidence of relaxed selection on several genes and of correlations among substitution rates and several other “traits” of the plastome among leafless members of orchid subfamily Orchidoideae.

Conclusions

Our findings advance knowledge on the phylogenetic relationships and paths of plastid genome evolution among the orchids, which have experienced more independent transitions to heterotrophy than any other plant family. This study demonstrates the importance of herbarium collections in comparative genomics of poorly known species of conservation concern.

前提：无叶异养植物是生物体改造的典型例子，其基因组后果已引起人们的极大兴趣。尤其是质粒基因组（质粒体）的测序速度很快，使得异养植物还原进化的概念模型不断完善。然而，由于存在大量取样空白，阻碍了对这些植物进行全面系统进化分析的能力：方法：利用标本馆标本中的花组织，我们对南美洲一种很少采集的无叶兰科植物 Degranvillea dermaptera 的质体进行了测序和分析：结果：在兰花亚科中，质体是已测序的质体中最小的。在 Degranvillea 中，它失去了叶状自养物种中的大部分基因，结构重新排列，基因含量与兰科植物中最退化的质体相似。通过使用明确考虑异型进化或特定品系随时间的进化速率变化的模型，我们发现了将 Degranvillea 放在 Spiranthinae 亚族中的有力证据。我们还发现了兰花亚科兰属无叶植物中几个基因的宽松选择以及质体的替代率和其他几个 "性状 "之间的相关性：我们的研究结果增进了人们对兰科植物系统发育关系和质体基因组进化路径的了解，兰科植物比其他任何植物科经历了更多独立的异营养过渡。这项研究证明了标本馆藏品在对鲜为人知的保护物种进行比较基因组学研究方面的重要性。

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引用次数: 0

Measuring leaf and root functional traits uncovers multidimensionality of plant responses to arbuscular mycorrhizal fungi 测量叶片和根系的功能特征可发现植物对假根菌根真菌反应的多维性。

IF 2.4 2区生物学 Q2 PLANT SCIENCES

American Journal of Botany

Pub Date : 2024-07-11 DOI: 10.1002/ajb2.16369

Katherine N. Stahlhut, Deannah G. Neupert, Josie E. Laing, Lydia J. Witt, Jonathan T. Bauer

Premise

While many studies have measured the aboveground responses of plants to mycorrhizal fungi at a single time point, little is known about how plants respond belowground or across time to mycorrhizal symbiosis. By measuring belowground responses and growth over time in many plant species, we create a more complete picture of how mycorrhizal fungi benefit their hosts.

Methods

We grew 26 prairie plant species with and without mycorrhizal fungi and measured 14 functional traits to assess above- and belowground tissue quality and quantity responses and changes in resource allocation. We used function-valued trait (FVT) modeling to characterize changes in species growth rate when colonized.

Results

While aboveground biomass responses were positive, the response of traits belowground were much more variable. Changes in aboveground biomass accounted for 60.8% of the variation in mycorrhizal responses, supporting the use of aboveground biomass response as the primary response trait. Responses belowground were not associated with aboveground responses and accounted for 18.3% of the variation. Growth responses over time were highly variable across species. Interestingly, none of the measured responses were phylogenetically conserved.

Conclusions

Mycorrhizal fungi increase plant growth in most scenarios, but the effects of these fungi belowground and across time are more complicated. This study highlights how differences in plant allocation priorities might affect how they utilize the benefits from mycorrhizal fungi. Identifying and characterizing these differences is a key step to understanding the effects of mycorrhizal mutualisms on whole plant physiology.

前提：虽然许多研究都是在单一时间点测量植物对菌根真菌的地上反应，但对于植物在地下或不同时间段对菌根共生的反应却知之甚少。通过测量多种植物的地下反应和不同时期的生长情况，我们可以更全面地了解菌根真菌如何使宿主受益：方法：我们种植了 26 种有菌根真菌和没有菌根真菌的草原植物，并测量了 14 种功能性状，以评估地上和地下组织的质量和数量反应以及资源分配的变化。我们使用功能值性状（FVT）模型来描述定殖时物种生长率的变化：结果：虽然地上生物量的反应是积极的，但地下性状的反应却多变得多。地上生物量的变化占菌根反应变化的 60.8%，支持将地上生物量反应作为主要反应性状。地下反应与地上反应无关，占变异的 18.3%。不同物种随时间变化的生长响应差异很大。有趣的是，所测量的反应都不具有系统发育上的保守性：结论：在大多数情况下，菌根真菌都能促进植物生长，但这些真菌在地下和不同时期的影响则更为复杂。这项研究强调了植物分配优先次序的差异可能会影响它们如何利用菌根真菌的益处。识别和描述这些差异是了解菌根互生对整个植物生理影响的关键一步。

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引用次数: 0

Evidence for human-caused founder effect in populations of Solanum jamesii at archaeological sites: II. Genetic sequencing establishes ancient transport across the Southwest USA 考古遗址中茄科植物种群的人类始祖效应证据：II.基因测序确定了跨越美国西南部的古代迁移。

IF 2.4 2区生物学 Q2 PLANT SCIENCES

American Journal of Botany

Pub Date : 2024-07-11 DOI: 10.1002/ajb2.16365

Bruce M. Pavlik, Alfonso del Rio, John Bamberg, Lisbeth A. Louderback

Premise

The domestication of wild plant species can begin with gathering and transport of propagules by Indigenous peoples. The effect on genomic composition, especially in clonal, self-incompatible perennials would be instantaneous and drastic with respect to new, anthropogenic populations subsequently established. Reductions in genetic diversity and mating capability would be symptomatic and the presence of unique alleles and genetic sequences would reveal the origins and ancestry of populations associated with archaeological sites. The current distribution of the Four Corners potato, Solanum jamesii Torr. in the Southwestern USA, may thus reflect the early stages of a domestication process that began with tuber transport.

Methods

Herein genetic sequencing (GBS) data are used to further examine the hypothesis of domestication in this culturally significant species by sampling 25 archaeological and non-archaeological populations.

Results

Archaeological populations from Utah, Colorado and northern Arizona have lower levels of polymorphic loci, unique alleles, and heterozygosity than non-archaeological populations from the Mogollon region of central Arizona and New Mexico. Principle components analysis, Fst values, and structure analysis revealed that genetic relationships among archaeological populations did not correspond to geographic proximity. Populations in Escalante, Utah were related to those on the Mogollon Rim (400 km south) and had multiple origins and significant disjunctions with those populations in Bears Ears, Chaco Canyon, and Mesa Verde sites.

Conclusions

Movement of tubers from the Mogollon region may have occurred many times and in multiple directions during the past, resulting in the complex genetic patterns seen in populations from across the Four Corners region.

前提：野生植物物种的驯化可以从土著居民采集和运输繁殖体开始。对基因组组成的影响，尤其是对克隆性、自相容性多年生植物的影响，将是瞬间的，而且对随后建立的新的人为种群影响巨大。遗传多样性和交配能力的降低将是症状性的，而独特等位基因和遗传序列的存在将揭示与考古遗址相关的种群的起源和祖先。因此，四角马铃薯（Solanum jamesii Torr.）目前在美国西南部的分布可能反映了从块茎运输开始的驯化过程的早期阶段。方法：本文通过对25个考古和非考古种群进行取样，利用基因测序（GBS）数据进一步研究了这一具有重要文化意义的物种的驯化假说：来自犹他州、科罗拉多州和亚利桑那州北部的考古种群的多态位点、独特等位基因和杂合度水平低于来自亚利桑那州中部和新墨西哥州莫格伦地区的非考古种群。主成分分析、Fst 值和结构分析表明，考古种群之间的遗传关系与地理上的接近程度并不相符。犹他州埃斯卡兰特的种群与莫格伦边缘（向南 400 公里）的种群有亲缘关系，与熊耳、查科峡谷和梅萨维德遗址的种群有多个起源和明显的分离：结论：过去，莫格伦地区的块茎可能曾多次向多个方向移动，导致整个四角地区的种群出现复杂的遗传模式。

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引用次数: 0

An evolutionary disruption of the buzz pollination syndrome in neotropical montane plants 新热带高山植物嗡嗡授粉综合征的进化破坏。

IF 2.4 2区生物学 Q2 PLANT SCIENCES

American Journal of Botany

Pub Date : 2024-07-02 DOI: 10.1002/ajb2.16367

Eduardo K. Nery, Mayara K. Caddah, Fabian A. Michelangeli, Anselmo Nogueira

Premise

Under pollinator limitations, specialized pollination syndromes may evolve toward contrasting responses: a generalized syndrome with increased pollinator attraction, pollinator reward, and pollen transfer capacity; or the selfing syndrome with increased self-pollen deposition, but reduced pollinator attraction and pollen transfer capacity. The buzz-pollination syndrome is specialized to explore female vibrating bees as pollinators. However, vibrating bees become less-active pollinators at montane areas of the Atlantic Forest (AF) domain. This study investigated whether the specialized buzz-pollination syndrome would evolve toward an alternative floral syndrome in montane areas of the AF domain, considering a generalized and the selfing syndromes as alternative responses.

Methods

We utilized a lineage within the buzz-pollinated Miconia as study system, contrasting floral traits between montane AF-endemic and non-endemic species. We measured and validated floral traits that were proxies for pollinator attraction, reward access, pollen transfer capacity, and self-pollen deposition. We inferred the evolution of floral trait via phylogenetic comparative methods.

Results

AF-endemic species have selectively evolved greater reward access and more frequently had generalist pollination. Nonetheless, AF-endemic species also have selectively evolved toward lower pollen transfer capacity and greater self pollination. These patterns indicated a complex evolutionary process that has jointly favored a generalized and the selfing syndromes.

Conclusions

The buzz pollination syndrome can undergo an evolutionary disruption in montane areas of the AF domain. This floral syndrome is likely more labile than often assumed, allowing buzz-pollinated plants to reproduce in environments where vibrating bees are less-reliable pollinators.

前提：在授粉者受限的情况下，专门的授粉综合征可能会朝着截然不同的反应方向进化：一种普遍的综合征，具有更强的授粉者吸引力、授粉者奖励和花粉转移能力；或者是自花授粉综合征，具有更强的自身花粉沉积能力，但授粉者吸引力和花粉转移能力下降。嗡嗡授粉综合征专门探索雌性振动蜂作为授粉者。然而，在大西洋森林（AF）地区的高山地带，振动蜂的授粉活性较低。本研究调查了在大西洋森林区的山地地区，特化的嗡嗡授粉综合征是否会向另一种花卉综合征演化，并将广义综合征和自交综合征作为替代反应：方法：我们利用嗡嗡授粉的Miconia中的一个品系作为研究系统，对比了山地AF特有种和非特有种的花特征。我们测量并验证了花的性状，这些性状是授粉者吸引力、奖励获取、花粉传递能力和自花粉沉积的替代物。我们通过系统进化比较方法推断了花朵性状的进化过程：结果：非洲花卉特有物种选择性地进化出了更高的报酬获取能力，并更频繁地进行通性授粉。然而，AF 特有物种也有选择性地进化出较低的花粉传递能力和较强的自花授粉能力。这些模式表明了一个复杂的进化过程，该过程共同促进了泛化和自花授粉综合征：结论：嗡嗡授粉综合征在 AF 领域的高山地区可能会发生进化中断。嗡嗡授粉综合征可能比通常认为的更加易变，它允许嗡嗡授粉的植物在振动蜂是不太可靠的授粉者的环境中繁殖。

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引用次数: 0

Nitrogen-fixing bacteria boost floral attractiveness in a tropical legume species during nutrient limitation 固氮细菌在热带豆科植物养分受限期间提高了花的吸引力。

IF 2.4 2区生物学 Q2 PLANT SCIENCES

American Journal of Botany

Pub Date : 2024-07-02 DOI: 10.1002/ajb2.16363

Caroline Souza, Lorena B. Valadão-Mendes, Isadora Schulze-Albuquerque, Pedro J. Bergamo, Douglas D. Souza, Anselmo Nogueira

Premise

Legumes establish mutualistic interactions with pollinators and nitrogen (N)-fixing bacteria that are critical for plant reproduction and ecosystem functioning. However, we know little about how N-fixing bacteria and soil nutrient availability affect plant attractiveness to pollinators.

Methods

In a two-factorial greenhouse experiment to assess the impact of N-fixing bacteria and soil types on floral traits and attractiveness to pollinators in Chamaecrista latistipula (Fabaceae), plants were inoculated with N-fixing bacteria (NF+) or not (NF-) and grown in N-rich organic soil (+N organic soil) or N-poor sand soil (-N sand soil). We counted buds and flowers and measured plant size during the experiment. We also measured leaf, petal, and anther reflectance with a spectrophotometer and analyzed reflectance curves. Using the bee hexagon model, we estimated chromatic contrasts, a crucial visual cues for attracting bees that are nearby and more distant.

Results

NF+ plants in -N sand soil had a high floral display and color contrasts. On the other hand, NF- plants and/or plants in +N organic soil had severely reduced floral display and color contrasts, decreasing floral attractiveness to bee pollinators.

Conclusions

Our findings indicate that the N-fixing bacteria positively impact pollination, particularly when nutrients are limited. This study provides insights into the dynamics of plant–pollinator interactions and underscores the significant influence of root symbionts on key floral traits within tropical ecosystems. These results contribute to understanding the mechanisms governing mutualisms and their consequences for plant fitness and ecological dynamics.

前提：豆科植物与传粉昆虫和固氮（N）细菌建立了互利互动关系，这对植物繁殖和生态系统功能至关重要。然而，我们对固氮菌和土壤养分供应如何影响植物对传粉昆虫的吸引力知之甚少：在一项评估固氮菌和土壤类型对 Chamaecrista latistipula（豆科）花朵特征和对传粉昆虫吸引力影响的双因子温室实验中，植物接种了固氮菌（NF+）或未接种固氮菌（NF-），并在富含氮的有机土壤（+N 有机土壤）或贫氮的沙土（-N 沙土）中生长。在实验过程中，我们对花蕾和花朵进行了计数，并测量了植株的大小。我们还用分光光度计测量了叶片、花瓣和花药的反射率，并分析了反射率曲线。利用蜜蜂六边形模型，我们估算了色度对比，这是吸引近处和远处蜜蜂的重要视觉线索：结果：-N 沙土中的 NF+ 植物具有较高的花朵显示度和色彩对比度。另一方面，NF-植物和/或+N有机土壤中的植物的花朵显示度和色彩对比度严重下降，降低了花朵对蜜蜂授粉者的吸引力：我们的研究结果表明，固氮细菌对授粉有积极影响，尤其是在养分有限的情况下。这项研究深入揭示了植物与授粉者之间的互动动态，并强调了根系共生体对热带生态系统中关键花卉性状的重要影响。这些结果有助于理解互作机制及其对植物适应性和生态动态的影响。

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引用次数: 0

Linking the macroclimatic niche of native lithophytic ferns and their prevalence in urban environments 将本地石生蕨类植物的宏观气候生态位与它们在城市环境中的分布联系起来。

IF 2.4 2区生物学 Q2 PLANT SCIENCES

American Journal of Botany

Pub Date : 2024-07-01 DOI: 10.1002/ajb2.16364

Tammo Reichgelt

Premise

Vertical surfaces in urban environments represent a potential expansion of niche space for lithophytic fern species. There are, however, few records of differential success rates of fern species in urban environments.

Methods

The occurrence rates of 16 lithophytic fern species native to the northeastern USA in 14 biomes, including four urban environments differentiated by percentage of impervious surfaces, were evaluated. In addition, the natural macroclimatic ranges of these species were analyzed to test whether significant differences existed in climatic tolerance between species that occur in urban environments and species that do not.

Results

Three species appear to preferentially occur in urban environments, two species may facultatively occur in urban environments, and the remaining 11 species preferentially occur in nondeveloped rural environments. The natural range of fern species that occur in urban environments had higher summer temperatures than the range of species that do not, whereas other macroclimatic variables, notably winter temperatures and precipitation, were less important or insignificant.

Conclusions

Vertical surfaces in urban environments may represent novel niche space for some native lithophytic fern species in northeastern USA. However, success in this environment depends, in part, on tolerance of the urban heat island effect, especially heating of impervious surfaces in summer.

前提：城市环境中的垂直表面可能会扩大石生蕨类植物的生态位空间。然而，有关蕨类物种在城市环境中不同成功率的记录却很少：方法：评估了原产于美国东北部的 16 种石生蕨类植物在 14 个生物群落中的出现率，其中包括按不透水表面百分比区分的 4 个城市环境。此外，还分析了这些物种的自然宏观气候范围，以检验出现在城市环境中的物种与不出现在城市环境中的物种在气候耐受性方面是否存在显著差异：结果：有 3 个物种似乎更喜欢出现在城市环境中，有 2 个物种可能暂时出现在城市环境中，其余 11 个物种则更喜欢出现在不发达的农村环境中。出现在城市环境中的蕨类物种的自然分布区夏季温度高于不出现在城市环境中的物种，而其他宏观气候变量，特别是冬季温度和降水量，则不那么重要或不重要：城市环境中的垂直表面可能是美国东北部一些本地石生蕨类植物的新生态位空间。然而，在这种环境中能否成功部分取决于对城市热岛效应的耐受性，特别是夏季不透水表面的加热。

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引用次数: 0

Naturally diverse plant communities do not resist invasion by the strong competitor, Microstegium vimineum 自然多样化的植物群落无法抵御强大的竞争者--Microstegium vimineum 的入侵。

IF 2.4 2区生物学 Q2 PLANT SCIENCES

American Journal of Botany

Pub Date : 2024-06-28 DOI: 10.1002/ajb2.16362

Griffin Lee Williams, J. Stephen Brewer

Premise

Theory predicts and empirical studies have shown that ecologically manipulated communities with high species diversity are resistant to invasion, but do these predictions and results hold true when applied to highly competitive invaders in natural communities? Few studies of diversity-mediated invasion resistance have measured both invasion resistance and invader impact in the same study.

Methods

We used a two-year field experiment to test: (1) diversity-mediated competitive resistance to patch expansion by the grass, Microstegium vimineum; and (2) the competitive effect of M. vimineum on resident plant diversity. We examined responses of M. vimineum to two native plant density-reduction treatments that had opposite effects on species diversity: (1) reducing species richness via the removal of rare species; and (2) reducing dominance by reducing the density of the dominant resident species. We examined the effects of M. vimineum reduction by pre-emergent herbicide on resident diversity in the second year of the study.

Results

Neither rare species removal nor dominant species reduction significantly increased M. vimineum density (relative growth rate). The pre-emergent herbicide dramatically reduced M. vimineum in year 2 of the study, but not most resident plants, which were perennials and indirectly benefited from the herbicide at a more productive site, presumably due to reduced competition from M. vimineum.

Conclusions

Diversity-mediated resistance did not effectively deter invasion by a highly competitive invader. In the case of M. vimineum and at more productive sites, it would appear that nearly complete removal of this invader is necessary to preserve plant species diversity.

前提：理论预测和实证研究表明，物种多样性高的生态操纵群落具有抵抗入侵的能力，但这些预测和结果适用于自然群落中高度竞争的入侵者时是否成立？很少有关于多样性介导的入侵抵抗力的研究在同一研究中同时测量入侵抵抗力和入侵者的影响：我们利用为期两年的野外实验来测试：（1）多样性介导的对禾本科植物微囊禾草（Microstegium vimineum）斑块扩张的竞争性抵抗；（2）微囊禾草（M. vimineum）对常住植物多样性的竞争性影响。我们研究了微囊禾本科植物对两种降低本地植物密度处理的反应，这两种处理对物种多样性的影响截然相反：（1）通过移除稀有物种降低物种丰富度；（2）通过降低优势常住物种的密度降低优势度。我们在研究的第二年考察了通过萌芽前除草剂减少薇甘菊对常住物种多样性的影响：结果：无论是清除稀有物种还是减少优势物种，都没有明显增加薇甘菊的密度（相对生长率）。在研究的第二年，萌芽前除草剂大幅减少了薇甘菊，但大多数常绿植物却没有减少，这些常绿植物是多年生植物，在产量更高的地点间接受益于除草剂，这可能是由于薇甘菊的竞争减少所致：结论：多样性介导的抗性并不能有效阻止高竞争力入侵者的入侵。就 M. vimineum 而言，在产量较高的地点，要想保护植物物种多样性，就必须几乎完全清除这种入侵者。

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引用次数: 0

Challenge accepted: Evolutionary lineages versus taxonomic classification of North American shrub willows (Salix) 接受挑战：北美灌木柳（Salix）的进化世系与分类学分类。

IF 2.4 2区生物学 Q2 PLANT SCIENCES

American Journal of Botany

Pub Date : 2024-06-25 DOI: 10.1002/ajb2.16361

Pia Marinček, Étienne Léveillé-Bourret, Ferris Heiduk, Jing Leong, Stéphane M. Bailleul, Martin Volf, Natascha D. Wagner

Premise

The huge diversity of Salix subgenus Chamaetia/Vetrix clade in North America and the lack of phylogenetic resolution within this clade has presented a difficult but fascinating challenge for taxonomists to resolve. Here we tested the existing taxonomic classification with molecular tools.

Methods

In this study, 132 samples representing 46 species from 22 described sections of shrub willows from the United States and Canada were analyzed and combined with 67 samples from Eurasia. The ploidy levels of the samples were determined using flow cytometry and nQuire. Sequences were produced using a RAD sequencing approach and subsequently analyzed with ipyrad, then used for phylogenetic reconstructions (RAxML, SplitsTree), dating analyses (BEAST, SNAPPER), and character evolution analyses of 14 selected morphological traits (Mesquite).

Results

The RAD sequencing approach allowed the production of a well-resolved phylogeny of shrub willows. The resulting tree showed an exclusively North American (NA) clade in sister position to a Eurasian clade, which included some North American endemics. The NA clade began to diversify in the Miocene. Polyploid species appeared in each observed clade. Character evolution analyses revealed that adaptive traits such as habit and adaxial nectaries evolved multiple times independently.

Conclusions

The diversity in shrub willows was shaped by an evolutionary radiation in North America. Most species were monophyletic, but the existing sectional classification could not be supported by molecular data. Nevertheless, monophyletic lineages share several morphological characters, which might be useful in the revision of the taxonomic classification of shrub willows.

前言：北美沙柳亚属 Chamaetia/Vetrix 支系的多样性非常丰富，而该支系内部缺乏系统发育解析，这给分类学家带来了一个难以解决但又引人入胜的挑战。在这里，我们用分子工具检验了现有的分类法：在这项研究中，我们分析了来自美国和加拿大的灌木柳树 22 个描述部分的 132 个样本（代表 46 个物种），并将其与来自欧亚大陆的 67 个样本进行了合并。使用流式细胞仪和 nQuire 测定了样本的倍性水平。采用 RAD 测序方法生成序列，然后用 ipyrad 进行分析，最后用于系统发育重建（RAxML、SplitsTree）、年代分析（BEAST、SNAPPER）以及 14 种选定形态特征的特征演化分析（Mesquite）：结果：RAD 测序方法可以建立一个清晰的灌木柳树系统发育关系。结果表明，灌木柳树的系统发生树显示，北美支系是欧亚支系的姊妹支系，其中包括一些北美特有种。北美支系在中新世开始分化。每个观察到的支系中都出现了多倍体物种。特征进化分析表明，习性和正面蜜腺等适应性特征是多次独立进化的：结论：灌木柳树的多样性是由北美洲的进化辐射形成的。结论：灌木柳树的多样性是由北美洲的进化辐射形成的。大多数物种是单系的，但现有的科系分类无法得到分子数据的支持。不过，单系物种具有一些共同的形态特征，这些特征可能有助于修订灌木柳树的分类学分类。

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引用次数: 0