580 Pflanzen (Botanik)
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An independent Taiwanese lineage of powdery mildew on the endemic host species Koelreuteria henryi
(2024)
Background: Powdery mildews (Erysiphaceae, Ascomycota) are common plant disease agents and also cause stress for forest and fruit trees worldwide as well as in Taiwan. The powdery mildew Erysiphe bulbouncinula on Koelreuteria host trees was considered an endemic species in China. While in China the host was K. paniculata and only the teleomorph stage found, the anamorph and the teleomorph were both recorded for the host in Taiwan, K. henryi. We aimed to clarify the relationship of the powdery mildews recorded under E. bulbouncinula with an apparently disjunct distribution.
Results: Specimens of powdery mildew on K. henryi from Taiwan were characterized based on the anamorph morphology and DNA sequences. They revealed a new record of Sawadaea koelreuteriae for this host species and Taiwan and a new species of Erysiphe, E. formosana, sister to E. bulbouncinula from China.
Conclusions: In Erysiphe on Koelreuteria hosts, speciation of plant parasitic fungi seems to be correlated with disjunct host and geographic distribution possibly shaped by extinction of potential host species which are known only as fossils. Two of the three extant East Asian species of Koelreuteria are now known as hosts of specific Erysiphe species. We may predict a further not yet discovered Erysiphe species on the third East Asian species, K. bipinnata, in South and Southwest China. In the speciation in Sawadaea, the extinction events in Koelreuteria can be excluded from being involved.
Highlights
• Floating ability facilitates water dispersal.
• Hydrochorous seed dispersal is more effective than wind dispersal.
• Storage in water induced germination rate.
Abstract
In many Central European countries Fraxinus pennsylvanica is an invasive species that spreads rapidly in floodplain forests. The aim of this study was to analyse anemochorous and hydrochorous dispersal distances and to compare the findings with dispersal data for the native Fraxinus excelsior. A simulation revealed that wind dispersal distances are similar for both species, reaching to 120–250 m. By contrast, the mean floating time (50% floating samaras) measured in an experiment was 2 days in the case of F. pennsylvanica and 0.5 days for F. excelsior. This high floating ability facilitates water dispersal over several kilometres in both species, but for the invasive species the modelled mean dispersal distance was 3.7 times higher. A germination test of F. pennsylvanica seeds revealed that the rate, onset and speed of germination increase with the duration of the inundation. After a maximum storage time in water of about 15 days the germination rate amounts to 78%, which was higher than the germination rate of seeds without storage in water (53%). We also found that regeneration was enhanced in flooded areas. Hydrochory, therefore, may be viewed as an important factor explaining the successful invasion of F. pennsylvanica in floodplain forests in Central Europe.
Seed dispersal is hard to measure, and there is still a lack of knowledge about dispersal-related traits of plant species. Therefore, we developed D3, the Dispersal and Diaspore Database (available at
www.seed-dispersal.info), which aims at simplifying ecological and evolutionary analyses by providing and integrating various items related to seed dispersal: empirical studies, functional traits, image analyses and ranking indices (quantifying the adaptation to dispersal modes).
Currently, the database includes data for more than 5000 taxa and 33 items as well as digital images of diaspores (i.e. the dispersal units), seeds, fruits and infructescences. The included items cover common traits like diaspore mass, size, shape, terminal velocity and seed number per diaspore. Furthermore, we present newly or further developed items like ecomorphological categorizations of the diaspore and fruit as well as information from literature on prevailing dispersal modes. Finally, we introduce several items which are not covered in other databases yet: surface structure and form of the diaspore, the exposure of the diaspores in the infructescence and dispersal rankings. Dispersal rankings allow estimations of how well certain species are adapted to a specific dispersal mode in comparison to a larger species set. They are calculated as the percentile rank of an indicator of species’ dispersal potential in relation to a larger species set.
Especially for the new and further developed items we outline the basic concepts in detail, describe the measurement and categorization methods and show how to interpret and integrate these data for single species as well as for larger species sets. Thereby, we calculate baseline statistics of seed dispersal of the Central European flora. We found that diaspores of 72% of the taxa show specializations related to long-distance dispersal, i.e. most often elongated appendages or nutrient-rich tissues. Diaspore masses, sizes and terminal velocities vary over several orders of magnitude and can be approximated by lognormal distributions.
Climate forecasts show that in many regions the temporal distribution of precipitation events will become less predictable. Root traits may play key roles in dealing with changes in precipitation predictability, but their functional plastic responses, including transgenerational processes, are scarcely known. We investigated root trait plasticity of Papaver rhoeas with respect to higher versus lower intra-seasonal and inter-seasonal precipitation predictability (i.e., the degree of temporal autocorrelation among precipitation events) during a four-year outdoor multi-generation experiment. We first tested how the simulated predictability regimes affected intra-generational plasticity of root traits and allocation strategies of the ancestors, and investigated the selective forces acting on them. Second, we exposed three descendant generations to the same predictability regime experienced by their mothers or to a different one. We then investigated whether high inter-generational predictability causes root trait differentiation, whether transgenerational root plasticity existed and whether it was affected by the different predictability treatments. We found that the number of secondary roots, root biomass and root allocation strategies of ancestors were affected by changes in precipitation predictability, in line with intra-generational plasticity. Lower predictability induced a root response, possibly reflecting a fast-acquisitive strategy that increases water absorbance from shallow soil layers. Ancestors’ root traits were generally under selection, and the predictability treatments did neither affect the strength nor the direction of selection. Transgenerational effects were detected in root biomass and root weight ratio (RWR). In presence of lower predictability, descendants significantly reduced RWR compared to ancestors, leading to an increase in performance. This points to a change in root allocation in order to maintain or increase the descendants’ fitness. Moreover, transgenerational plasticity existed in maximum rooting depth and root biomass, and the less predictable treatment promoted the lowest coefficient of variation among descendants’ treatments in five out of six root traits. This shows that the level of maternal predictability determines the variation in the descendants’ responses, and suggests that lower phenotypic plasticity evolves in less predictable environments. Overall, our findings show that roots are functional plastic traits that rapidly respond to differences in precipitation predictability, and that the plasticity and adaptation of root traits may crucially determine how climate change will affect plants.
Phyllanthus novofriburgensis J.C.R.Mendes, J.M.A.Braga & Fraga sp. nov. and P. pedrosae J.C.R.Mendes, J.M.A.Braga & Fraga sp. nov. are new species of Phyllanthaceae described from the Brazilian Atlantic Forest and Brazilian Cerrado, respectively. Phyllanthus novofriburgensis resembles P. acutifolius Poir. ex Spreng., P. hypoleucus Müll.Arg. and P. lilliputianus J.C.R.Mendes, J.M.A.Braga & Fraga, sharing ovate, elliptical, and lanceolate leaf blades. However, it can be distinguished by its pendulous habit, often with sinuous branches and lanceolate leaf blades with characteristically revolute margins. Phyllanthus pedrosae exhibits morphological similarities with P. claussenii Müll.Arg. due to its subshrubby and prostrate habit. It is distinghuished by the unisexual inflorescence with cymules composed of one or two staminate flowers proximally positioned in the axil of the branches and solitary pistillate flowers distally situated, and the 5-merous calyx in the staminate and pistillate flowers. Both new species are classified in Phyllanthus subgen. Phyllanthus sect. Phyllanthus subsect. Clausseniani G.L.Webster, primarily due to the deeply emarginate anthers. Notes on their geographical distribution and habitat are provided, as well as a key to the species of Phyllanthus from Southeastern Brazil.
The fossil record of the diverse subfamily Passifloroideae (>750 species and 17 genera) is relatively poor. Despite the distinctiveness of its leaves (glandular and often emarginate), most of the fossils from this group have been described from seeds. Fossil seeds have been recovered from Europe, and North and South America. A lack of information on seed morphology for all the genera and tribes of this subfamily has prevented a tribe-level identification of the fossils and a better understanding of their biogeographic patterns. The Passifloroideae is divided into three tribes: Passifloreae with 10 genera, Paropsieae with six genera and the monotypic Jongkindieae. This study provides new descriptions for 15 species from 5 genera from the mostly Afrotropical tribe Paropsieae based on herbarium material, and introduces an online seed database and a key for 100 species of Passifloroideae compiled from literature and direct observations. Our study shows a low morphological diversity among the seeds of Paropsieae in comparison to a much larger diversity within Passifloreae. Some rare morphologies are only present in Passifloreae and can be used to assign seeds to this tribe. Within the Paropsieae, Androsiphonia has seed that are very distinct from those in the other genera in the tribe and also from the rest of the subfamily. The genus Paropsia exhibits two main morphotypes, while the genera Barteria, Paropsiopsis and Smeathmannia have very similar seeds with a highly conserved morphology. These results suggest that living or fossil Paropsieae cannot be identified confidently based solely on seed characters.
Forest wildflowers bloom earlier as Europe warms: lessons from herbaria and spatial modelling
(2022)
Today plants often flower earlier due to climate warming. Herbarium specimens are excellent witnesses of such long-term changes. However, the magnitude of phenological shifts may vary geographically, and the data are often clustered. Therefore, large-scale analyses of herbarium data are prone to pseudoreplication and geographical biases.
We studied over 6000 herbarium specimens of 20 spring-flowering forest understory herbs from Europe to understand how their phenology had changed during the last century. We estimated phenology trends with or without taking spatial autocorrelation into account.
On average plants now flowered over 6 d earlier than at the beginning of the last century. These changes were strongly associated with warmer spring temperatures. Flowering time advanced 3.6 d per 1°C warming. Spatial modelling showed that, in some parts of Europe, plants flowered earlier or later than expected. Without accounting for this, the estimates of phenological shifts were biased and model fits were poor.
Our study indicates that forest wildflowers in Europe strongly advanced their phenology in response to climate change. However, these phenological shifts differ geographically. This shows that it is crucial to combine the analysis of herbarium data with spatial modelling when testing for long-term phenology trends across large spatial scales.
Field work in the Kibira National Park (Burundi), located in the Kivu-Ruwenzori system of the Afromontane Region, revealed the existence of a new species clearly belonging to the Argocoffeopsis-Calycosiphonia clade (Coffeeae, Rubiaceae). The species shows striking heterophylly: the plagiotropous branches have several nodes bearing reduced or even scaly leaves. For the rest, it shares characters with Calycosiphonia and Kupeantha. Therefore, a morphological comparison with the clade is done, as well as molecular phylogenetic analyses. The morphology of the novelty is closer to Kupeantha than to Calycosiphonia, inter alia because the anthers have no transverse septa, in contrast to the multilocellate anthers of Calycosiphonia. However, the molecular data advocate for a position in Calycosiphonia – a result weakening the morphological distinction between Calycosiphonia and Kupeantha. The former genus is no longer restricted to species with transverse septa in the anthers and with placental outgrowths around the seed. The new species is formally described as Calycosiphonia albertina Ntore & Robbr. sp. nov. Nomenclaturally, this placement is also the most conservative option. A taxonomic treatment, illustrations, a geographical distribution map, and a preliminary conservation assessment are provided. The previous inclusion of Calycosiphonia pentamera in Kupeantha based on morphology is here corroborated by molecular analyses.
Diospyros L. is a large genus of flowering plants predominantly distributed in the tropics. It comprises over 700 species globally and around 300 are believed to occur in South-East Asia. Many species are economically important and exploited for the production of ebony wood and persimmons, yet taxonomic information on the genus is incomplete and inconsistent due to its morphological and nomenclatural complexity. Revisions of Diospyros in continental and insular South-East Asia were conducted independently by different authors, occasionally with different names used for the same species, or different species being given the same name in different countries. During our ongoing study of the genus Diospyros in Indochina (Cambodia, Laos, Thailand and Vietnam), we identified several such instances. Here, we clarify the most commonly misidentified species, including 1) D. apiculata Hiern, D. strigosa Hemsl. and D. tamiriensis Lecomte; 2) D. bejaudii Lecomte and D. retrofracta Bakh.; 3) D. dictyoneura Hiern and D. hasseltii Zoll.; 4) D. borneensis Hiern and D. fecunda H.R.Fletcher. Lectotypifications are also made for D. brachiata King & Gamble var. lanceolata H.R.Fletcher, D. fecunda, D. similis Craib and D. strigosa.
Abstract
Natural plant populations often harbour substantial heritable variation in DNA methylation. However, a thorough understanding of the genetic and environmental drivers of this epigenetic variation requires large-scale and high-resolution data, which currently exist only for a few model species. Here, we studied 207 lines of the annual weed Thlaspi arvense (field pennycress), collected across a large latitudinal gradient in Europe and propagated in a common environment. By screening for variation in DNA sequence and DNA methylation using whole-genome (bisulfite) sequencing, we found significant epigenetic population structure across Europe. Average levels of DNA methylation were strongly context-dependent, with highest DNA methylation in CG context, particularly in transposable elements and in intergenic regions. Residual DNA methylation variation within all contexts was associated with genetic variants, which often co-localized with annotated methylation machinery genes but also with new candidates. Variation in DNA methylation was also significantly associated with climate of origin, with methylation levels being lower in colder regions and in more variable climates. Finally, we used variance decomposition to assess genetic versus environmental associations with differentially methylated regions (DMRs). We found that while genetic variation was generally the strongest predictor of DMRs, the strength of environmental associations increased from CG to CHG and CHH, with climate-of-origin as the strongest predictor in about one third of the CHH DMRs. In summary, our data show that natural epigenetic variation in Thlaspi arvense is significantly associated with both DNA sequence and environment of origin, and that the relative importance of the two factors strongly depends on the sequence context of DNA methylation. T. arvense is an emerging biofuel and winter cover crop; our results may hence be relevant for breeding efforts and agricultural practices in the context of rapidly changing environmental conditions.
Author summary
Variation within species is an important level of biodiversity, and it is key for future adaptation. Besides variation in DNA sequence, plants also harbour heritable variation in DNA methylation, and we want to understand the evolutionary significance of this epigenetic variation, in particular how much of it is under genetic control, and how much is associated with the environment. We addressed these questions in a high-resolution molecular analysis of 207 lines of the common plant field pennycress (Thlaspi arvense), which we collected across Europe, propagated under standardized conditions, and sequenced for their genetic and epigenetic variation. We found large geographic variation in DNA methylation, associated with both DNA sequence and climate of origin. Genetic variation was generally the stronger predictor of DNA methylation variation, but the strength of environmental association varied between different sequence contexts. Climate-of-origin was the strongest predictor in about one third of the differentially methylated regions in the CHH context, which suggests that epigenetic variation may play a role in the short-term climate adaptation of pennycress. As pennycress is currently being domesticated as a new biofuel and winter cover crop, our results may be relevant also for agriculture, particularly in changing environments.