Early diversifications of angiosperms and their insect pollinators: Were they unlinked?

The present-day ubiquity of angiosperm-insect pollination has led to the hypothesis that these two groups coevolved early in their evolutionary history. However, recent fossil discoveries and fossil-calibrated molecular dating analyses challenge the notion that early diversifications of angiosperms and insects were inextricably linked. In this article we examine (i) the discrepancies between dates of emergence for major clades of angiosperm and insect lineages; (ii) the long history of gymnosperm–insect pollination modes, which likely shaped early angiosperm–insect pollination mutualisms; and (iii) how the K–Pg mass extinction event was vital in propelling modern angiosperm-insect mutualisms. We posit that the early diversifications of angiosperms and their insect pollinators were largely decoupled, until the end of the Cretaceous.

Angiosperm diversification in the Early Cretaceous of Primorye, Far East of Russia

The Partizansk and Razdolnaya coal basins of Primorye, Far East of Russia, contain diverse early angiosperm fossils (pollen, leaves, and fruits). In this paper, we revise the previous data on early angiosperms of this region and summarize the results of our latest research. Age of the plant-bearing deposits was clarified using isotopic U-Th-Pb LA-ICP-MS and U-Pb ID-TIMS methods. Age of the upper part of the Lipovtsy Formation is 118 ± 1.4 Ma, which corresponds to the late Aptian. The early Albian age (109 ± 1 Ma) is assigned to the upper part of the Frentsevka Formation. The diversification of angiosperms in the Early Cretaceous of Primorye region and their systematic affinity are analyzed. Early representatives of Laurales, Ranunculales, Platanaceae, and probable Cercidiphyllaceae are revealed. New combination Pandanites ahnertii (Krysht.) Golovn., comb. nov. is created, and new species Araliaephyllum vittenburgii Golovn. et Volynets, sp. nov. is described. Reconstructions of herbaceous angiosperms from autochthonous locality Bolshoy Kuvshin are proposed.

Integrated Metabolome and Transcriptome Analysis Uncovers the Role of Anthocyanin Metabolism in Michelia maudiae

Michelia maudiae Dunn is one of the important ornamental plants in the Magnoliaceae family, and the color of its flowers usually appears naturally pure white. The discovery of a rubellis flower named M. maudiae Dunn var. rubicunda provides an opportunity to reveal the metabolism of the flavonoids and anthocyanins of this “early angiosperm” plant. Combined metabolome and transcriptome analyses were applied using white and rubellis mutant tepals. Seven stages have been divided for flower development, and forty-eight differentially altered metabolites were identified between white and rubellis tepals at a later stage. The major anthocyanins including peonidin O-hexoside, cyanidin O-syringic acid, cyanidin 3,5-O-diglucoside, cyanidin 3-O-glucoside, and pelargonidin 3-O-glucoside were upregulated over 157-fold in the mutant. Conversely, the highly significant accumulation of the colorless procyanidin or the slightly yellow epicatechin and catechin was found in white flowers. Putative homologues of color-related genes involved in the phenylpropanoid and flavonoid biosynthesis pathway were identified in the transcriptome. The increasing expression of dihydroflavonol 4-reductase (DFR) might play an important role in the occurrence of rubellis pigments, while the overexpression of anthocyanidin reductase (ANR) in white flowers may promote the biosynthesis of proanthocyanidins. Additionally, several coloration-related repressor R2R3-MYB transcription factors showed different expression levels in the tepals of the rubellis mutant. This study provides a comprehensive analysis relating color compounds to gene expression profiles of the Magnoliids plant M. maudiae. The newly generated information will provide a profound effect on horticultural applications of Magnoliaceae.

The Early Cretaceous Mesofossil Flora of Torres Vedras (Ne of Forte Da Forca), Portugal: A Palaeofloristic Analysis of an Early Angiosperm Community

An Early Cretaceous mesofossil flora is described from the lower part of the Almargem Formation (late Barremian-early Aptian) from Torres Vedras (NE of Forte da Forca), Portugal. The flora is the oldest mesofossil flora containing angiosperm remains to be described in detail based on well-preserved flower, fruit and seed remains. In addition to angiosperms, the mesofossil flora also includes megaspores, sporangia and tiny leaves of spore-bearing plants. There are also twigs, cone fragments and seeds of conifers and seeds assigned to the BEG group. In total about 100 species have been distinguished. Most abundant in terms of plant fragments identified, are spore-bearing plants and conifers. Although only about 18 % of the specimens can be attributed to angiosperms, angiosperm diversity is unexpected high considering the age of the flora. Angiosperms account for about 62 % of all species recognized. Angiosperm diversity is mainly at the level of ANA-grade angiosperms, eumagnoliids and in a few cases early diverging lineages of monocots. Eudicots are subordinate. Twenty new genera and 28 new species of angiosperms are established (Anaspermum operculatum gen. et sp. nov., Appofructus nudus gen. et sp. nov., Appomattoxia minuta sp. nov., Burgeria striata gen. et sp. nov., Canrightia elongata sp. nov., Choffaticarpus compactus gen. et sp. nov., Dejaxia brevicolpites gen. et sp. nov., Dinisia portugallica gen. et sp. nov., Eckhartia brevicolumella gen. et sp. nov., Eckhartia longicolumella sp. nov., Eckhartia intermedia sp. nov., Eckhartianthus lusitanicus gen. et sp. nov., Eckhartiopsis parva gen. et sp. nov., Gastonispermum antiquum sp. nov., Goczania rugosa gen. et sp. nov., Goczania inaequalis sp. nov., Goczania punctata sp. nov., Ibrahimia verminculata gen. et sp. nov., Juhaszia portugallica gen. et sp. nov., Kempia longicolpites gen. et sp. nov., Kvacekispermum costatum sp. nov., Mcdougallia irregularis gen. et sp. nov., Nicholsia brevicolpites gen. et sp. nov., Piercipollis simplex gen. et sp. nov., Reyanthus lusitanicus gen. et sp. nov., Samylinaea punctata gen. et sp. nov., Teebacia hughesii gen. et sp. nov., Vedresia elliptica gen. et sp. nov.). Comparison with results of a palynological study from the same horizon that yielded the mesofossil flora shows a marked underestimation of angiosperm diversity in the palynoflora, a pattern that has also been recognized elsewhere.

Retracing the contours of the early angiosperm environmental niche

Background and Aims Our aim was to understand the environmental conditions of the emergence and radiation of early angiosperms. Such a question has long remained controversial because various approaches applied in the past have drawn conflicting images of early angiosperm ecology. Methods We provided a new perspective on the question by using support vector machines to model the environmental niche of 51 species belonging to ten genera of extant lineages that diverged early during angiosperm evolution (basal angiosperms). Then, we analysed the resulting pattern of niche overlap and determined whether this pattern deviates from what would be expected on the basis of a null model or whether it might mirror a legacy of a common primitive niche based on a phylogenetic reconstruction. Key Results The niche of three-quarters of the species and all genera converged towards tropical montane cloud forests (TMCFs). The latitudinal pattern of basal angiosperm richness indeed culminated in the tropics, and the elevational pattern revealed a humpback curve peaking between 2000 m and 3500 m when accounting for the effect of area. At first glance, this diversity pattern does not significantly differ from null predictions. However, we revealed a tendency for the basal-most taxa to occur in TMCFs so that phylogenetic reconstructions indicated that the niche of the common ancestor of the sampled basal angiosperms had a probability of 0.85–0.93 to overlap with TMCFs. Conclusions Our new approach indicates that the environmental convergence of extant basal angiosperms towards TMCFs would reflect a legacy of an ancestral niche from which the least basal taxa would have diverged following a random pattern under geometric constraints.