Recent advances in molecular phylogenetics and a series of important palaeobotanical discoveries have revolutionized our understanding of angiosperm diversification. Yet, the origin and early evolution of their most characteristic feature, the flower, remains poorly understood. In particular, the structure of the ancestral flower of all living angiosperms is still uncertain. Here we report model-based reconstructions for ancestral flowers at the deepest nodes in the phylogeny of angiosperms, using the largest data set of floral traits ever assembled. We reconstruct the ancestral angiosperm flower as bisexual and radially symmetric, with more than two whorls of three separate perianth organs each (undifferentiated tepals), more than two whorls of three separate stamens each, and more than five spirally arranged separate carpels. Although uncertainty remains for some of the characters, our reconstruction allows us to propose a new plausible scenario for the early diversification of flowers, leading to new testable hypotheses for future research on angiosperms.

BackgroundHybridization and polyploidy are potent forces that have regularly stimulated plant evolution and adaptation. Dactylorhiza majalis s.s., D. traunsteineri s.l. and D. ebudensis are three allopolyploid species of a polyploid complex formed through unidirectional (and, in the first two cases, recurrent) hybridization between the widespread diploids D. fuchsii and D. incarnata. Differing considerably in geographical extent and ecological tolerance, the three allopolyploids together provide a useful system to explore genomic responses to allopolyploidization and reveal their role in adaptation to contrasting environments.ResultsAnalyses of cDNA-AFLPs show a significant increase in the range of gene expression of these allopolyploid lineages, demonstrating higher potential for phenotypic plasticity than is shown by either parent. Moreover, allopolyploid individuals express significantly more gene variants (including novel alleles) than their parents, providing clear evidence of increased biological complexity following allopolyploidization. More genetic mutations seem to have accumulated in the older D. majalis compared with the younger D. traunsteineri since their respective formation.ConclusionsMultiple origins of the polyploids contribute to differential patterns of gene expression with a distinct geographic structure. However, several transcripts conserved within each allopolyploid taxon differ between taxa, indicating that habitat preferences shape similar expression patterns in these independently formed tetraploids. Statistical signals separate several transcripts - some of them novel in allopolyploids - that appear correlated with adaptive traits and seem to play a role favouring the persistence of individuals in their native environments. In addition to stabilizing the allopolyploid genome, genetic and epigenetic alterations are key determinants of adaptive success of the new polyploid species after recurrent allopolyploidization events, potentially triggering reproductive isolation between the resulting lineages.

Attempts at historical reconstruction are based on limited data. We are more likely to produce accurate historical reconstructions by utilizing information from diverse sources and pooling data within the relevant research communities which will allow us to build up a moving picture of the geological, climatic, and biological evolution of our planet. We suggest that dated phylogenies of plants can contribute greatly to a better understanding of Earth history. Timing of phylogenetic splits of lowland restricted lineages on either side of the Andes could provide information on the timing of montane uplift and associated climatic changes. The timing of the arrival and diversification of organisms restricted to specific climatic regimes at a particular altitude can provide information on the age at which mountains reached a height adequate for that climate once corrected for global climate changes. As a model for study, we discuss how dated phylogenies in biome rich Colombia may contribute to an understanding of geological and climatic change in north‐western South America. Lowland wet forest restricted lineages separated from the mid‐Miocene, whereas lineages primarily restricted to mid‐altitude cloud forests began to diversify from the mid‐ to late‐Miocene and the majority of high‐altitude Páramo lineages began to diversify during the Pliocene. The age of diversification of altitudinally restricted lineages therefore gives an indication of the age at which particular altitudes may have been reached.

Abstract—Cyrtandromoea is a genus consisting of about 12 species of perennial caulescent herbs with a distribution in China, India, Myanmar, Thailand, and western Malesia. The genus has previously been associated with either Gesneriaceae or the tribe Mimuleae in Phrymaceae (in former Scrophulariaceae) with morphology in favor of the latter and molecular plastid ndhF data the former. We addressed the placement of this genus by assembling a four gene dataset (matK, ndhF, rps16, and trnL-F) comprising 270 ingroup samples representing 270 species and 51 families of the core asterids, including all families of Lamiales currently recognized. These included 111 species representing 66 genera of Gesneriaceae. We used maximum parsimony, maximum likelihood, and Bayesian inference analyses to reconstruct phylogenies that showed Cyrtandromoea to be placed in Phrymaceae. A fine-scale analysis focusing on Phrymaceae using ITS and trnL-F and 79 samples revealed that Cyrtandromoea is most closely related to a clade of genera in Phrymaceae that included Mimulus s. s. A combination of morphological synapomorphies such as cymose inflorescences, 5-angled toothed calyx, flowers with bilocular ovary with axile placentation with numerous small seeds with endosperm, and loculicidal dehiscing capsule support this placement. Our results strongly support the placement of Cyrtandromoea in Phrymaceae.