They are young, and they are many: dating freshwater lineages in unicellular dinophytes.

Dinophytes are one of few protist groups that have an extensive fossil record and are therefore appropriate for time estimations. However, insufficient sequence data and strong rate heterogeneity have been hindering to put dinophyte evolution into a time frame until now. Marine-to-freshwater transitions within this group are considered geologically old and evolutionarily exceptional due to strong physiological constraints that prevent such processes. Phylogenies based on concatenated rRNA sequences (including 19 new GenBank entries) of two major dinophyte lineages, Gymnodiniaceae and Peridiniales, were carried out using an uncorrelated molecular clock and five calibration points based on fossils. Contrarily to previous assumptions, marine-to-freshwater transitions are more frequent in dinophytes (i.e. five marine-freshwater transitions in Gymnodiniaceae, up to ten but seven strongly supported transitions in Peridiniales), and none of them occurred as early as 140 MYA. Furthermore, most marine-to-freshwater transitions, and the followed diversification, took place after the Cretaceous-Paleogene boundary. Not older than 40 MYA, the youngest transitions within Gymnodiniaceae and Peridiniales occurred under the influence of the Eocene climate shift. Our evolutionary scenario indicates a gradual diversification of dinophytes without noticeable impact of catastrophic events, and their freshwater lineages have originated several times independently at different points in time.

Molecular phylogenetics of dinophytes harboring diatoms as endosymbionts (Kryptoperidiniaceae, Peridiniales), with evolutionary interpretations and a focus on the identity of Durinskia oculata from Prague.

Peridinialean dinophytes include a unique evolutionary group of algae harboring a diatom as an endosymbiont (Kryptoperidiniaceae), whose phylogenetic origin and internal relationships are not fully resolved at present. Several interpretations of the thecal plate pattern present in Durinskia oculata currently compete and lead to considerable taxonomic confusion. Moreover, it is unclear at present whether the species is restricted to freshwater habitats, or occurs in the marine environment as well. We collected material at the type locality of D. oculata in the Czech Republic and established monoclonal strains. Dinophyte cells were studied using light and electron microscopy, and we also determined DNA sequences of several rRNA regions (including the Internal Transcribed Spacers) for molecular characterization and phylogenetics. The morphology of strain GeoM∗662 indicated a plate formula of Po, X, 4', 2a, 6″, 5c, 5s, 5‴, 2⁗, which was sustained also in form of a microscopic slide serving as an epitype. In the molecular DNA tree based on a matrix composed of concatenated rRNA sequences, strain GeoM∗662 showed a close relationship to other species of Durinskia, and the freshwater species clearly differs from the marine members. Two independent colonization events from the marine into the freshwater environment can be inferred within the Kryptoperidiniaceae. We provide a summarizing cladogram of dinophytes harboring a diatom as endosymbiont with evolutionary novelties indicated as well as a morphological key to the 6 species of Durinskia that are currently accepted.

Global distribution, climatic preferences and photosynthesis-related traits of C4 eudicots and how they differ from those of C4 grasses.

C4 is one of three known photosynthetic processes of carbon fixation in flowering plants. It evolved independently more than 61 times in multiple angiosperm lineages and consists of a series of anatomical and biochemical modifications to the ancestral C3 pathway increasing plant productivity under warm and light-rich conditions. The C4 lineages of eudicots belong to seven orders and 15 families, are phylogenetically less constrained than those of monocots and entail an enormous structural and ecological diversity. Eudicot C4 lineages likely evolved the C4 syndrome along different evolutionary paths. Therefore, a better understanding of this diversity is key to understanding the evolution of this complex trait as a whole. By compiling 1207 recognised C4 eudicots species described in the literature and presenting trait data among these species, we identify global centres of species richness and of high phylogenetic diversity. Furthermore, we discuss climatic preferences in the context of plant functional traits. We identify two hotspots of C4 eudicot diversity: arid regions of Mexico/Southern United States and Australia, which show a similarly high number of different C4 eudicot genera but differ in the number of C4 lineages that evolved in situ. Further eudicot C4 hotspots with many different families and genera are in South Africa, West Africa, Patagonia, Central Asia and the Mediterranean. In general, C4 eudicots are diverse in deserts and xeric shrublands, tropical and subtropical grasslands, savannas and shrublands. We found C4 eudicots to occur in areas with less annual precipitation than C4 grasses which can be explained by frequently associated adaptations to drought stress such as among others succulence and salt tolerance. The data indicate that C4 eudicot lineages utilising the NAD-ME decarboxylating enzyme grow in drier areas than those using the NADP-ME decarboxylating enzyme indicating biochemical restrictions of the later system in higher temperatures. We conclude that in most eudicot lineages, C4 evolved in ancestrally already drought-adapted clades and enabled these to further spread in these habitats and colonise even drier areas.

A story from the Miocene: Clock-dated phylogeny of Sisymbrium L. (Sisymbrieae, Brassicaceae).

Morphological variability and imprecise generic boundaries have hindered systematic, taxonomical, and nomenclatural studies of Sisymbrium L. (Brassicaceae, Sisymbrieae DC.). The members of this almost exclusively Old-World genus grow mostly on highly porous substrates across open steppe, semidesert, or ruderal habitats in the temperate zone of the Northern Hemisphere and African subtropics. The present study placed the biological history of Sisymbrium L. into time and space and rendered the tribus Sisymbrieae as monotypic. Five nuclear-encoded and three chloroplast-encoded loci of approximately 85% of all currently accepted species were investigated. Several accessions per species covering their whole distribution range allowed for a more representative assessment of intraspecific genetic diversity. In the light of fossil absence, the impact of different secondary calibration methods and taxon sets on time spans was tested, and we showed that such a combinatorial nested dating approach is beneficial. Multigene phylogeny accompanied with a time divergence estimation analysis placed the onset and development of this tribus into the western Irano-Turanian floristic region during the Miocene. Continuous increase in continentality and decrease in temperatures promoted the diversity of the Sisymbrieae, which invaded the open grasslands habitats in Eurasia, Mediterranean, and South Africa throughout the Pliocene and Pleistocene. Our results support the assumption of the Irano-Turanian region as a biodiversity reservoir for adjacent regions.

Pleistocene dynamics of the Eurasian steppe as a driving force of evolution: Phylogenetic history of the genus Capsella (Brassicaceae).

Capsella is a model plant genus of the Brassicaceae closely related to Arabidopsis. To disentangle its biogeographical history and intrageneric phylogenetic relationships, 282 individuals of all five currently recognized Capsella species were genotyped using a restriction digest-based next-generation sequencing method. Our analysis retrieved two main lineages within Capsella that split c. one million years ago, with western C. grandiflora and C. rubella forming a sister lineage to the eastern lineage consisting of C. orientalis. The split was attributed to continuous latitudinal displacements of the Eurasian steppe belt to the south during Early Pleistocene glacial cycles. During the interglacial cycles of the Late Pleistocene, hybridization of the two lineages took place in the southwestern East European Plain, leading to the allotetraploid C. bursa-pastoris. Extant genetic variation within C. orientalis postdated any extensive glacial events. Ecological niche modeling showed that suitable habitat for C. orientalis existed during the Last Glacial Maximum around the north coast of the Black Sea and in southern Kazakhstan. Such a scenario is also supported by population genomic data that uncovered the highest genetic diversity in the south Kazakhstan cluster, suggesting that C. orientalis originated in continental Asia and migrated north- and possibly eastwards after the last ice age. Post-glacial hybridization events between C. bursa-pastoris and C. grandiflora/rubella in the southwestern East European Plain and the Mediterranean gave rise to C. thracica. Introgression of C. grandiflora/rubella into C. bursa-pastoris resulted in a new Mediterranean cluster within the already existing Eurasian C. bursa-pastoris cluster. This study shows that the continuous displacement and disruption of the Eurasian steppe belt during the Pleistocene was the driving force in the evolution of Capsella.

The phylogeographic history of Krascheninnikovia reflects the development of dry steppes and semi-deserts in Eurasia.

Constituting one of Earth's major biomes, steppes are characterised by naturally treeless extra-tropical vegetation. The formation of the Eurasian steppe belt, the largest steppe region in the world, began in Central Asia during the Neogene. In the glacial stages of the Pleistocene, steppe displaced forest vegetation, which in turn recolonised the area during the warmer interglacial periods, thus affecting the distribution of plants adapted to these habitats. Krascheninnikovia ceratoides (Chenopodiaceae) is a plant characteristic of dry steppe and semi-desert formations. Earlier studies showed that the ancestor of this autochthonous steppe element originated in Central Asia during the Miocene/Pliocene, i.e., in the same region and at the same time as the first appearance of steppe vegetation. However, as the extant lineages of Krascheninnikovia ceratoides diversified only 2.2 ± 0.9 Mya, it may represent a modern element of current dry steppe and semi-desert formations, rather than a component of the first steppe precursors of the Miocene. As such, it may have capitalised on the climatic conditions of the cold stages of the Quaternary to expand its range and colonise suitable habitats outside of its area of origin. To test this hypothesis, phylogeographic methods were applied to high-resolution genotyping-by-sequencing data. Our results indicate that Krascheninnikovia originated in western Central Asia and the Russian Altai, then spread to Europe in the West, and reached North America in the East. The populations of eastern Central Asia and North America belong to the same clade and are genetically clearly distinct from the Euro-Siberian populations. Among the populations west of the Altai Mountains, the European populations are genetically distinct from all others, which could be the result of the separation of populations east and west of the Urals caused by the Pleistocene transgressions of the Caspian Sea.

Zero Intercalary Plates in Parvodinium (Peridiniopsidaceae, Peridiniales) and Phylogenetics of P. elpatiewskyi, comb. nov.

Parvodinium elpatiewskyi, comb. nov., is a common freshwater dinophyte without intercalary plates and with various spines on hypothecal sutures. However, the taxonomy of the species has had a complex history, and its systematic placement remained unclear. The conserved type of P. elpatiewskyi, comb. nov., illustrated here for the first time using electron microscopy, is an environmental sample. Based on the newly collected material from Berlin (Germany) we provide a morphological description using light and electron microscopy as well as new molecular rRNA sequence data to specify the phylogenetic position of P. elpatiewskyi, comb. nov. This species belongs to Peridiniopsidaceae, more precisely to Parvodinium, which usually possesses two intercalary plates. However, evolutionary inference indicates the loss of such plates in P. elpatiewskyi, comb. nov. Other traits that are of taxonomic importance and have not received enough attention in the past are the large Sd plate converging the second antapical plate and the presence of cellular hypocystal opening during replication.

The Hot Spot in a Cold Environment: Puzzling Parvodinium (Peridiniopsidaceae, Peridiniales) from the Polish Tatra Mountains.

Because of a great variety of remote localities and cold habitats, the Tatra Mountains are home to many freshwater protist lineages. Dinophytes have been subjected to a number of studies from this area dating mostly to the first half of the 20th century, but their true diversity remains elusive until today. We collected water tow samples at five lakes in the Tatra Mountains in order to establish monoclonal strains. We found four lineages that were distinctive in terms of morphology and DNA sequence data and that could be assigned to peridinialean Parvodinium. These four species can be readily distinguished based on a general shape, size, thecal plate tabulation pattern and presence or absence of an antapical protuberance. The plate overlap pattern is considered conserved at higher taxonomic levels, and the divergent keystone Plate 3' in Parvodinium marciniakii, sp. nov., thus appears as a striking diagnostic character. For taxonomic conclusion, we describe two species new to science and validate three old scientific names (i.e., one species and two varieties). Our study underlines that the biodiversity assessment, particularly of species adapted to cold environments, is anything but completed as shown from remote and unexplored European landscapes such as the Tatra Mountains.