AIM: Phylogeographical studies of Eastern Mediterranean species are rare. We aim to fill a gap in the current understanding of the role of Eastern Mediterranean glacial refugia, and their connections ...with other refugia across Europe. To this end, we studied the genetic diversity distribution and genetic structure of the modern population of Quercus cerris in relation to its Quaternary demographic history and to more ancient events. LOCATION: Mediterranean Basin; Italian, Balkan, Anatolian peninsulas. METHODS: A total of 192 populations were genotyped with six polymorphic chloroplast microsatellites, and the genetic diversity and differentiation of the populations were evaluated. The geographical structure of genetic variation was analysed with a Bayesian clustering method using baps 5.2. The demographic history of Q. cerris was explored by an approximate Bayesian computation procedure using diyabc 2.0. To reconstruct the past distribution of Q. cerris, we also considered the chronology and geographical distribution of fossil records. RESULTS: Thirty‐five haplotypes were found, three of which (together) were found in 71.82% of individuals. Bayesian analysis resulted in three genetically and geographically distinct clusters: a Western group, a Central group, and an Eastern group. The approximate Bayesian computation analysis, together with fossil data, showed a possible bottleneck leading to the divergence of the Eastern and Central populations in the Early Pleistocene (Gelasian). The split into two groups of populations in the Italian and Balkan Peninsulas, respectively, was probably caused by a marked population contraction during a glacial phase of the Middle Pleistocene. MAIN CONCLUSIONS: This study provides information on the potential role of Eastern Europe and the Near East as refugia and as a source for ancient westward range expansions in the Mediterranean region. Our study covers a remarkable gap in European oak phylogeography, showing a putative eastern origin of Q. cerris and the presence of large amounts of genetic diversity in this region.
Past studies of the end-Permian extinction (EPE), the largest biotic crisis of the Phanerozoic, have not resolved the timing of events in southern high-latitudes. Here we use palynology coupled with ...high-precision CA-ID-TIMS dating of euhedral zircons from continental sequences of the Sydney Basin, Australia, to show that the collapse of the austral Permian Glossopteris flora occurred prior to 252.3 Ma (~370 kyrs before the main marine extinction). Weathering proxies indicate that floristic changes occurred during a brief climate perturbation in a regional alluvial landscape that otherwise experienced insubstantial change in fluvial style, insignificant reorganization of the depositional surface, and no abrupt aridification. Palaeoclimate modelling suggests a moderate shift to warmer summer temperatures and amplified seasonality in temperature across the EPE, and warmer and wetter conditions for all seasons into the Early Triassic. The terrestrial EPE and a succeeding peak in Ni concentration in the Sydney Basin correlate, respectively, to the onset of the primary extrusive and intrusive phases of the Siberian Traps Large Igneous Province.
New investigations performed with a multi-proxy approach provide a robust climate reconstruction for the Late-Glacial in the Massif Central, France. The temperature reconstruction from Coleoptera is ...obtained from the Mutual Climatic Range Method, or “MCR” method, based on the range of climates corresponding to the area occupied today by the species identified in fossil assemblages. The Weighthed Averaging Partial Least Squared (WA-PLS) method is used to produce mean July temperature estimates from Chironomid assemblages. Climate reconstruction from pollen data is performed using an assemblage approach, the Modern Analogue Technique. During the Late-Glacial the July temperature (Tmax) reconstructed from beetles (Coleoptera) was lower than the current Tmax of 18.9 °C. Summer conditions were close to the present at the beginning of the Oldest Dryas (17400–14600 cal. BP), and during most of the Allerød (13900–12800 cal. BP). During the Younger Dryas (12800–11700 cal. BP) Tmax estimates ranged from 12 to 13 °C, much lower than today. The Tmax increased at the onset of the Holocene (11700 cal. BP), reaching values close to the modern conditions from the beginning of the period. Tmax reconstructed from chironomids shows an initial warming around 15000 cal. BP, with a Tmax rise from 7 °C to 11 °C. A maximum (13.5 °C) was reached around 13800 cal. BP. A second optimum of 16 °C occurred after 10800 cal. BP. The Late-Glacial Interstadial (LGI) is marked by temperature decreases (from 13 to 12 to 10–9 °C) around 13200–12900 cal. BP. A second climate minimum was reached around 12600 cal. BP, during the Younger Dryas (Tmax about 10 °C). The end of the Younger Dryas seems to have been warmer, with a Tmax of about 13 °C, just before the early Holocene climate improvement. Pollen-inferred results showed that the Late-Glacial climate at Roustières was characterized by colder and drier winter and summer seasons than today, and by conditions close to the modern ones around 11700 cal. BP, at the onset of the Holocene. Climate conditions comparable to the modern ones were also evidenced at the end of the Allerød, with colder than today conditions evidenced from both Tmax and Tmin (January temperature). During the Oldest and Younger Dryas the coldest month showed a temperature of −13 °C, while summers appeared more moderate (warmest month around 16 °C). Cold conditions were also reconstructed during the Bølling, while temperatures comparable to present-day values were reached during the Allerød. A cold oscillation occurred around 13400 cal. BP. Particularly dry conditions were reconstructed during the Oldest Dryas (17000–15800 cal. BP). From 15800 to the end of the Younger Dryas, the precipitation oscillated around 750 mm, but increased during the Allerød and the Holocene periods. These climatic trends reconstructed by the three proxies allowed identifying the temperate periods (LGI and the Holocene) and the cold events (Younger Dryas) of the Late-Glacial period. However, difficulties due to different sampling resolutions emerged, and several discrepancies linked to the proxy or the methods used are discussed.
Pseudoasterophyllites cretaceus from the Cenomanian of Bohemia was recently recognized as an angiosperm by association with stamens containing monosulcate pollen of the Tucanopollis type. New ...material indicates that the stamens were borne in short spikes, with each stamen subtended by a bract, whereas the carpels were solitary and contained a single pendent, orthotropous ovule. We have investigated the phylogenetic position of Pseudoasterophyllites by including it in a morphological analysis of extant angiosperms using backbone constraint trees that represent the current range of hypotheses on relationships of the five mesangiosperm clades. With a backbone tree in which Chloranthaceae are linked with magnoliids and Ceratophyllum with eudicots, the most parsimonious position of Pseudoasterophyllites is sister to Chloranthaceae, but a sister-group relationship to Ceratophyllum is only one step less parsimonious. With a backbone tree in which Chloranthaceae and Ceratophyllum form a clade, Pseudoasterophyllites is sister to Ceratophyllum, based on derived features shared with both Chloranthaceae and Ceratophyllum plus solitary female flowers (as in Ceratophyllum). Similar results are obtained when Pseudoasterophyllites is added to the analysis with other fossils inferred to be related to Chloranthaceae and/or Ceratophyllum. If the plants that produced Tucanopollis pollen in the Barremian-Aptian of Africa–South America are related to Pseudoasterophyllites, these results suggest that Chloranthaceae and Ceratophyllum are relicts of one of the most important early radiations of angiosperms, which included not only colonizers of disturbed terrestrial habitats but also halophytes and aquatics.
Lesotho provides a unique context for palaeoclimatic research. The small country is entirely landlocked by South Africa, yet has considerable variation in topography, climate, and associated ...vegetation over an approximate east-west transect. The region has been of archaeological interest for over a century, and hosts many Early to Late Stone Age sites with occupation preceding 80 000 years before present. The eastern Lesotho highlands are of interest to periglacial and glacial geomorphologists because of their well-preserve drelict landforms and contentious evidence for permafrost and niche glaciation during the late Quaternary. However, continuous proxy records for palaeoenvironmental reconstructions for Lesotho are scarce and hampered by a range of methodological shortfalls. These challenges include uncertain ages, poor sampling resolution, and proxies extracted from archaeological excavations for which there may be bias in selection. Inferences on palaeoclimates are thus based predominantly on archaeological and palaeogeomorphological evidence for discrete periods during the late Quaternary. This review paper presents a more detailed multidisciplinary synthesis of late Quaternary conditions in Lesotho. We simultaneously considered the varying data that contribute to the under-studied palaeoenvironmental record for southern Africa. The collective palaeoenvironmental data for eastern Lesotho were shown to be relatively contradictory, with considerable variations in contemporaneous palaeoclimatic conditions within the study area. We argue that although methodological challenges may contribute to this variation, the marked changes in topography result in contrasting late Quaternary palaeoenvironments. Such environments are characterised by similar contrasting microclimates and niche ecologies as are witnessed in the contemporary landscape. These spatial variations within a relatively small landlocked country are of importance in understanding broader southern African palaeoenvironmental change.
Most remains of Carboniferous lyginopteridalean seed‐plant fronds used to be classified in a single fossil‐genus (Sphenopteris) based mainly on pinnule morphology. By incorporating additional ...characters linked to frond architecture and rachial features a more natural taxonomy has now been achieved. Eight fossil‐genera of lyginopteridalean fronds are now recognised (Sphenopteris, Calymmotheca, Eusphenopteris, Karinopteris, Mariopteris, Palmatopteris, Spathulopteris, Sphenopteridium) for which the diagnostic descriptions, nomenclatural types and stratigraphical/chronological distribution are clarified. This provides a more natural and therefore robust means of recording these fossils, which will help improve studies on past plant diversity and floristics. A by‐product of this revision is that some fossil‐species of fern fronds previously placed in Sphenopteris will need to be reclassified into fossil‐genera that are defined on reproductive structures.
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