Background: Flowering plants (angiosperms) dominate most global ecosystems today, but their rapid Cretaceous diversi cation has remained poorly understood ever since Darwin referred to it as an 'abominable mystery'. Although numerous Cretaceous fossil owers have been discovered in recent years, most are represented by incomplete charcoali ed fragments that do not preserve delicate structures such as complete petals and surface textures, which means that their similarity to living forms is often di cult to discern. The scarcity of information about the ecology of early angiosperms makes it di cult to test hypotheses about the drivers of their diversi cation. Among other factors, frequent res in the Cretaceous have been postulated as having possibly facilitated the rise of angiosperms. However, to date no early fossil angiosperms displaying re-adapted traits have been known, making the role of re in shaping Cretaceous oras uncertain.Results: We report the discovery of two exquisitely preserved fossil ower species, one identical to the in orescences of the extant crown eudicot genus Phylica and the other recovered as a sister group to Phylica, both preserved as inclusions in Cretaceous amber from northern Myanmar (~99 Ma). These specialized ower structures, named Phylica piloburmensis sp. nov. and Eophylica priscastellata gen. et sp. nov., were adapted to surviving frequent wild res, providing the earliest evidence of re-resistance in angiosperms. The fossils suggest that re was a signi cant selective force in Cretaceous angiosperm oras and that adaptations to re resistance in some eudicot clades have been conserved for at least 99 Ma. This morphological stasis encompasses a range of oral characters, including the production of 'pseudo-owers', and characteristic fruit and pollen architecture. Given its morphological distinctiveness,
The polygrammoid fern family Polypodiaceae represents one of the most diversified epiphytic fern groups, with more than 1600 species distributed on all continents except Antarctica, with the highest species diversity in tropical and subtropical regions. Despite progress in recent phylogenetic studies of Polypodiaceae, the infrafamilial classification of this group of ferns is still problematic. Here, we explore the phylogenetic relationship within Polypodiaceae using plastid genome (plastome) and nuclear ribosomal cistron genome data obtained from high-throughput sequencing. Although genome skimming data strongly support the monophyly of many genera and clades of Polypodiaceae, relationships within some clades and along the backbone of the phylogeny remain incongruent between plastome and nuclear data. The explanation is possibly a factor of complex evolutionary history found in these clades, such as rapid radiation, incomplete lineage sorting, ancient hybridization, and recent introgression. Based on the concatenated dataset, our phylogenetic analyses support nine major clades in Polypodiaceae, which merit the recognition as subfamilies, Crypsinoideae, Grammitidoideae, Loxogrammoideae, Microsoroideae, Platycerioideae, Polypodioideae, Adetogrammoideae, Campyloneuroideae, and Serpocauloideae, while the latter three are separated from Polypodioideae as new subfamilies. All of these infrafamilial divisions, identified with molecular data, are further supported by non-molecular features including leaf dissection, venation, scales and paraphyses, soral features, and geographical distributions. Systematic and taxonomic discussions on the subfamilial treatment are also provided.
Plants of the Selaginella tamariscina group are common rosette-forming species showing great morphological variability across their distribution range. Integrating chloroplast genome data and morphological evidence, we studied the species delimitation within this group. We newly sequenced the complete chloroplast genomes of 53 individuals representing almost the entire geographical distribution of this group. Our phylogenetic analyses yielded a consistent topology dividing the S. tamariscina group into five major clades, which is further supported by principal component analysis of 18 morphological characters taken from 80 herbarium specimens. Based on the results of molecular analyses and morphological studies combined with the distribution information, we finally recognize five species in the S. tamariscina group, including two new species (S. algida sp. nov., S. graniticola sp. nov.), and one new subspecies (S. pulvinata subsp. qinbashanica subsp. nov.).
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