While roots and leaves have evolved independently in lycophytes, ferns and seed plants, there is still confusion regarding the morphological evolution of ferns, especially in whisk ferns, which lack true leaves and roots and instead only exhibit leaf-like appendages and absorptive rhizoids. In this study, analyses of comparative transcriptomics on positively selected genes were performed to provide insights into the adaptive evolution of whisk fern morphologies. Significantly clustered gene families specific to whisk ferns were mainly enriched in Gene Ontology (GO) terms “binding proteins” and “transmembrane transporter activity”, and positive selection was detected in genes involved in transmembrane transporter activities and stress response (e.g., sodium/hydrogen exchanger and heat shock proteins), which could be related to the adaptive evolution of tolerance to epiphytic environments. The analysis of TF/TR gene family sizes indicated that some rapidly evolving gene families (e.g., the GRF and the MADS-MIKC families) related to the development of morphological organs were commonly reduced in whisk ferns and ophioglossoid ferns. Furthermore, the WUS homeobox-containing (WOX) gene family and the knotted1-like homeobox (KNOX) gene family, both associated with root and leaf development, were phylogenetically conserved in whisk ferns and ophioglossoid ferns. In general, our results suggested that adaptive evolution to epiphytic environments might have occurred in whisk ferns. We propose that the simplified and reduced leaf and root system in whisk ferns is the result of reduction from the common ancestor of whisk ferns and ophioglossoid ferns, rather than an independent origin.
Although taxonomists target the remote wild regions to discover new species, taxa lacking a comprehensive and modern systematic treatment may be the new hotspot for biodiversity discovery. The development of molecular systematics integrated with microscopic observation techniques has greatly improved the ability of taxonomists to identify species correctly. Vittaria centrochinensis Ching ex J.F. Cheng, regarded as a synonym of Haplopteris fudzinoi (Makino) E.H.Crane, remained hidden from the eyes of fern taxonomists for more than 20 years. Herein, we collected several population samples of V. centrochinensis by performing molecular phylogenetic analysis of five cpDNA regions (rbcL, atpA, matK, ndhF, and trnL-trnF) and through micromophological observation of specimens which differs from H. fudzinoi by lamina width and exospores. Considering the differences in morphology, geographical range, and genetic distance between these two species, we formally recognized V. centrochinensis as an authentic species and proposed a new combination Haplopteris centrochinensis (Ching ex J.F.Cheng) Y.H.Yan, Z.Y.Wei & X.C.Zhang, comb. nov. Our findings demonstrate that several taxa in synonyms are missing, and nowadays taxonomy should also include re-evaluation of the past taxonomy.
Cryptic species comprise two or more taxa that are grounded under a single name because they are more-or-less indistinguishable morphologically. These species are potentially important for detailed assessments of biodiversity, but there now appear to be many more cryptic species than previously estimated. One taxonomic group likely to contain many cryptic species is Dicranopteris, a genus of forked ferns that occurs commonly along roadsides in Asia. The genus has a complex taxonomical history, and D. linearis has been particularly challenging with many intra-specific taxa dubiously erected to accommodate morphological variation that lacks clear discontinuities. To resolve species boundaries within Dicranopteris, we applied a molecular phylogenetic approach as complementary to morphology. Specifically, we used five chloroplast gene regions (rbcL, atpB, rps4, matK, and trnL-trnF) to generate a well-resolved phylogeny based on 37 samples representing 13 taxa of Dicranopteris, spanning the major distributional area in Asia. The results showed that Dicranopteris consists of ten highly supported clades, and D. linearis is polyphyletic, suggesting cryptic diversity within the species. Further through morphological comparison, we certainly erected Dicranopteris austrosinensis Y.H. Yan & Z.Y. Wei sp. nov. and Dicranopteris baliensis Y.H. Yan & Z.Y. Wei sp. nov. as distinct species and proposed five new combinations. We also inferred that the extant diversity of the genus Dicranopteris may result from relatively recent diversification in the Miocene based on divergence time dating. Overall, our study not only provided additional insights on the Gleicheniaceae tree of life, but also served as a case of integrating molecular and morphological approaches to elucidate cryptic diversity in taxonomically difficult groups.
Aim: Whole-genome duplication (WGD) plays a positive role in speciation in vascular plants and is considered to be an important mechanism for species adaptation to the extreme environments. Dating whole-genome duplication events in different species is essential for understanding the adaptive evolution of organisms. However, the role that these mechanisms play in vascular plants, especially ferns, is still poorly understood. Method: Based on the synonymous substitution rates (Ks) and absolute dating of the WGD event, this study used three different transcriptome sequences of Angiopteris fokiensis to analyze the contribution of polyploidy to the evolution of plants, and the silent substitution rate. Gene annotation and functional enrichment were carried out to elucidate the biological processes, molecular function, and cellular component for the genes retained after the WGD. Results: We found that there was at least one WGD event in A. fokiensis at 159-165 Mya, and most duplicated genes were often related to nutrient metabolism, signal transduction, adaptive regulation and anatomical structure development. The silent substitution rate of A. fokiensis is 1.66 × 10 -9 synonymous substitutions per site per year. Based on the above results, we speculate that the WGD event was associated with gymnosperms flourishing and the emergence of core angiosperms, or the Toarcian extinction event. The retention of particular genes after the WGD may have promoted genetic and morphological innovation in Angiopteris, thus helping it adapt to the drastic changes in environmental conditions. At present, A. fokiensis is the slowest evolving group of land plants except gymnosperms, which may relate to the long generation time, large genome and stable living habitat.
Conclusion:In this study, we analyzed the whole-genome duplication history and the patterns of retention of duplicated genes in A. fokiensis, suggesting that WGD events are of great influence in promoting the adaptation to extreme environmental changes of plants with slower evolutionary rates. These results provide more inspiration for understanding the adaptive evolution of other land plants.
English teaching can be carried out on the basis of the theory of humanism, whose feasible and effective application in English teaching proves to be true by means of the following three aspects-the students-centered teaching, the equal relationship between the teachers and students, and students' self-evaluation.
Abstract. Conceptual integration (blending) provides a way of the mental processes of mappings between languages and thoughts. If a source text is treated as the blends of the source language structures and schemata of the communicative events, in translating, when translators digest the source text, translators are actually disintegrating the text, and disclose the schemata of the communicative events integrated by the ST, and when actually translating, translators integrate the digested schemata from the source text with the target language structures.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.