Quaternary Events Research Articles

Fagus diversification in China in relation to East Asian monsoon evolution

When and how the extraordinary species diversity in subtropical East Asia formed is intensely debated, and the available evidence is often inconsistent. In this study, we evaluate the effects of pre- and post- Quaternary events on the evolutionary and biogeographic history of Chinese beech (Fagus species that now occur in China) to gain new insights into the historical establishment and future fate of the East Asian subtropical forest (EASF). A series of approaches and datasets were used to reconstruct biogeographic and evolutionary history of the Chinese beech. They include phylogeography based on the polymorphisms of the complete chloroplast genomes, species distribution models, and a large palaeobiogeographic dataset including 59 pre-Quaternary fossil records, 296 Quaternary fossil records and 3515 modern pollen records. Our multidisciplinary approach suggests that (i) Chinese beech has dispersed to subtropical East Asia and diversified in the early Miocene when the Asian monsoon (AM) intensified; (ii) the last post-glacial warming resulted in limited poleward displacement but significant contraction at southern and lower elevations; (iii) the poleward dispersal of Chinese beech was limited by drought in the early growing season in temperate China, controlled by the East Asian summer monsoon. Our results support the hypothesis that the establishment of the EASF is closely related to the evolution of the AM. More importantly, we suggest that with continued climate warming (e.g., during the last post-glacial period or under current climate change), the monsoon probably hindered rather than promoted the persistence of deciduous beech species, resulting in a decline in species richness.

Multi‐scale and multi‐parametric analysis of Late Quaternary event deposits within the active Corinth Rift (Greece)

AbstractA major challenge in subaqueous palaeoseismology is to understand the relationship between an earthquake/tsunami and a sedimentary event deposit recorded in drillcores. Expedition 381 of the International Ocean Discovery Program was dedicated to understanding the development of the Corinth Rift, Greece. Its drilled cores provide a potentially important resource to better understand depositional mechanisms of sedimentary event deposits within changing open marine to (semi‐)isolated environments. To achieve this, U‐channels and spatula samples were analysed from the topmost part (0–65 m below seafloor maximum depth) of holes M0078B and M0079A (ca 0–25 ka), using high‐resolution X‐ray microtomography in combination with grain‐size, magnetic and X‐ray fluorescence measurements. Structures and grain fabric are resolved down to 10 μm in voxel size, characterizing the geometry of the basal surface of ‘turbidite+homogenite’ sedimentary event deposits, and the internal base‐upward evolution at high‐resolution scale. This analysis suggests that these types of deposits are more complex than previously proposed, especially at the transition between the basal coarse turbidite sub‐unit and the fine‐grained homogenite upper sub‐unit, as well as within the homogenite. Combined with the other observations and parameters, X‐ray microtomography results are consistent with the interpretation of the Corinth ‘turbidite+homogenite’ deposits as having predominantly originated from seismic and/or aseismic slope failures followed by tsunami/seiche effects, despite subtle differences according to depositional environment.

Leguminosae endemic to the Chaco facing quaternary climate fluctuations

We investigated the influence of Quaternary climate fluctuations on the current distribution of three species of Leguminosae (Fabaceae) occurring in the Chaco. Potential distribution models of Bauhinia hagenbeckii, Muellera nudiflora and Neltuma rubriflora with a supposed endemism area were generated. The Last Interglacial, Last Glacial Maximum, Holocene Middle and current scenarios were used. The species showed a potential distribution according to the South American biogeographic history regarding the glacier regression and the formation of the Dry Diagonal. The models for each Quaternary event exhibited a tolerable AUC ≥ 0.9 for the validations. The LGM was the event that favoured the current species establishment areas in the Dry Diagonal. Quaternary climatic events were related to the current Leguminosae distribution. Bauhinia hagenbeckii and Neltuma rubriflora present similar areas of environmental suitability. Muellera nudiflora models with areas of environmental suitability were larger for the LIG and Holocene than for areas from other periods. All scenario models (LGM, HM and current scenario) highlighted the potential distribution of the three species concomitant with the glacier regression events and were consistent with the history of formation of South American dry areas.

Fan morphology evidence on Late Quaternary deformation in the southern front of the Central and Eastern Alborz Mountains in the Eyvanekey, Garmsar, Semnan areas, Northern Iran

Although numerous studies have been done on the Alborz Mountains, few have examined Quaternary events based on alluvial fans which are located in front of the southern limb of the Central and Eastern Alborz Mountains. This study analyzed the morphometric indexes for 131 alluvial fans (three generations) in the Eyvanekey, Garmsar, and Semnan areas (As, WLF, Bull, Fa, Fs, Fg, Fc, R) as well as for basins (Da, AF, T, Bs), mountain fronts (Fmf, Smf, Vf, Fd), and rivers (Sl). The morphometry results show that a young deformation in this area has caused on uplift in the crust along structures in the Alborz. The Garmsar area is more active than the Semnan area in which both are more active than the Eyvanekey area. All of the alluvial fan evolution in this area relate to the Quaternary events. The study on the information obtained from the exploitation wells and geoelectric profiles of the region shows that the Alborz uplift in the north is associated with the erosion and deposition of the new deposits in the form of alluvial fans. The bedrock behavior at the base of the fans has a direct effect on the formation of the second- and third-generation fans. The effect of the continual compressional tectonics in the Late Quaternary is associated with the uplifting evaporite masses, the uplifting hanging walls of the reverse faults, and the growth of the folded structures.

Dating late Quaternary events by the combined U‐Pb LA‐ICP‐MS and (U‐Th)/He dating of zircon: A case study on Omachi Tephra suite (central Japan)

AbstractDating of young (<1 Ma) geological events has long been a challenge for geochronologists. Combining (U‐Th)/He with U‐Pb or U‐Th‐disequilibrium dating methods offers a unique dating tool that can address this important period. We present a new methodology that combines U‐Pb LA‐ICP‐MS and (U‐Th)/He dating of zircon and use it to date two Pleistocene marker tephras (A1Pm and DPm) from the Omachi Tephra suite (Japan). A1Pm and DPm yield U‐Pb ages in the range of 350–850 and ~140–630 ka, respectively, documenting protracted periods of zircon crystallisation (100's of k.y.) prior to eruption. (U‐Th)/He ages constrain the eruption ages of the A1Pm and DPm tephras to 375 ± 13 and 97.1 ± 7.3 ka, respectively, and are in agreement with published estimates. This study demonstrates the potential of combined zircon U‐Pb LA‐ICP‐MS and (U‐Th)/He dating to constrain magmatic and eruption events in the critical ~100 ka–1 Ma interval.

The relative changes of a sea surface temperature in the South China Sea since the Pliocene

The reconstruction of sea surface temperature (SST) is a key issue in research on paleoceanography. The recently related studies are mainly concentrated on the Quaternary. The skeletons of a typical species of benthonic foraminifer (Amphistegina radiata) in the top 0–375.30 m interval of Well “Xike-1” reef core, Shidao Island, the Xisha Islands, are uniformly selected. The ratios of magnesium to calcium concentrations and other indicators are analyzed by an electron microprobe analysis (EMPA) with the purpose of estimating the paleo-SSTs since the Pliocene and further investigating the periodic change law of paleoclimate in the South China Sea (SCS). Meanwhile, the geologic significance of paleoclimatic events in the SCS is discussed with global perspectives. The results indicate that the paleo-SSTs reconstructed by the ratios of magnesium to calcium concentrations in the SCS show a general periodic trend of “high–low–high–low” in values changes since the Pliocene. By comparison, the fluctuations of reconstructed paleo-SSTs are much stronger in the Quaternary. Moreover, the variations of the ratios of magnesium to calcium concentrations in the A. radiata skeletons have recorded a series of major paleoclimatic events since the Pliocene, of which the Quaternary glaciation events and the Arctic ice cap forming events during the late Pliocene are more significant. Thus, using the changes of the ratios of magnesium to calcium concentrations in the A. radiata skeletons from Well “Xike-1” reef core to reflect the relative changes of paleo-SSTs is a relatively feasible and reliable way in the SCS, which is also proved by the correlation of drilling cores characteristics in this area.

Remote Sensing and Geo-Archaeological Data: Inland Water Studies for the Conservation of Underwater Cultural Heritage in the Ferrara District, Italy

In the southern area of the Ferrara District, Italy, remote sensing investigations associated with geo-archaeological drilling in underwater archaeological studies, have helped to broad our understanding of the historical evolution and cultural heritage of inland waterways. In working on prototype sites, we have taken a multidisciplinary approach of surveillance and preventive archaeology, and have collaborated with archaeologists, geologists, hydro-biologists, and engineers. In this area of research, often lakes, lagoons, and rivers are characterized by low visibility. Some Quaternary events have deeply modified Ferrara’s landscape. Analysis of preserved samples from micro-drillings, underwater direct and indirect surveys, and the cataloguing of historical artefacts, are giving to the researchers a remarkable ancient chronology line. Recent studies confirmed anthropization sequences from the 1st Century B.C. to the 6th Century A.D. Waterscape archaeology, a multidisciplinary science devoted to the study of the human use of wetlands and anthropological connection with the water environment, testifies the ways in which people, in the past, constructed and used the water environment. In this article, we describe underwater cultural heritage research using 3D side scan sonar surveys and artifacts analysis, comparing data from direct diving investigations and stratigraphic data from micro-geological drillings on sites of Lago Tramonto, Gambulaga, Portomaggiore (Ferrara).

A short-range endemic species from south-eastern Atlantic Rain Forest shows deep signature of historical events: phylogeography of harvestmen Acutisoma longipes (Arachnida: Opiliones)

The Brazilian Atlantic Rain Forest is amongst the most diverse biomes in the world, but the processes that shaped its biodiversity are still poorly understood. We used one mitochondrial and two nuclear markers to evaluate the phylogeographic patterns of the endemic harvestman Acutisoma longipes and its closely related species to investigate the biogeographic history of this biome. The results showed low intrapopulation diversity and strong population structure, suggesting poor dispersion amongst locations. Phylogenetic analyses pointed to three main mitochondrial lineages congruent with the geomorphology of the south-eastern region of Brazil (Serra do Mar, Serra da Mantiqueira, and interior plateau). These older divergences occurred in the middle-Neogene, suggesting that events in this period drove the diversification of the species, but Quaternary events also affected the populations locally. We detected some congruence between A. longipes demographic patterns and the areas of endemism delimited for harvestmen, suggesting that some regions of the distribution could have been more stable in the past (especially in Serra da Mantiqueira). Our findings corroborate that harvestmen are a suitable group for the study of ancient biogeographic events in the Atlantic Rain Forest, even at small-scale ranges. Acutisoma hamatum is here considered as a new junior synonym of A. longipes.

Role of tectonic inheritance in the instauration of Tunisian Atlassic fold-and-thrust belt: Case of Bouhedma – Boudouaou structures

Tectonic inversion in the Bouhedma-Boudouaou Mountains was investigated through recent field work and seismic lines interpretation calibrated with petroleum well data. Located to the Central-Southern Atlas of Tunisia, this area signed shortened intra-continental fold-and-thrust belts. Two dissymmetric anticlines characterize Bouhedma – Boudouaou major fold. These structures show a strong virgation respectively from E-W to NNE-SSW as a response to the interference between both tectonic inversion and tectonic inheritance.This complex geometry is driven by Mesozoic rifting, which marked an extensional inherited regime. A set of late Triassic-Early Jurassic E-W and NW-SE normal faults dipping respectively to the North and to the East seems to widely affect the overall geodynamic evolution of this domain. They result in major thickness changes across the hanging wall and the footwall blocks in response with the rifting activity.Tectonic inversion is inferred from convergence between African and European plates since late Cretaceous. During Serravalian - Tortonian event, NW-SE trending paroxysm led to: 1) folding of pre-inversion and syn-inversion strata, 2) reactivation of pre-existing normal faults to reverse ones and 3) orogeny of the main structures with NE-SW and E-W trending.The compressional feature still remains active during Quaternary event (Post-Villafranchian) with N-S trending compression. Contraction during inversion generates folding and internal deformation as well as Fault-Propagation-Fold and folding related strike.

Paleoseismology of the Mount Narryer fault zone, Western Australia: A multistrand intraplate fault system

Our paleoseismological study of faults and fault-related folds comprising the Mount Narryer fault zone reveals a mid- to late Quaternary history of repeated morphogenic earthquakes that have influenced the planform and course of the Murchison, Roderick, and Sanford Rivers, Western Australia. The dominant style of deformation involves folding of near-surface sediments overlying discrete basement faults. Carbon-14, optically stimulated luminescence, and in situ–produced 10 Be constrain the timing of the events and late Quaternary slip rates associated with fault propagation folds in tectonically uplifted and deformed alluvial channel deposits. A flight of five inset fluvial terraces is preserved where the Murchison River flows across the Roderick River fault. These terraces, which we infer to be coseismic, are consistent with at least four late Quaternary seismic events on the order of moment magnitude (M w ) 7.1 within the last ~240 k.y. Secondary shears expressed on the folds indicate a component of dextral strike-slip displacement. Quaternary slip rates on the underlying faults range from 0.01 to 0.07 mm yr –1 , with a total slip rate for the zone between 0.04 and 0.11 mm yr –1 . These rates are intermediate to those in the adjacent Mesozoic basin (>0.1 mm yr –1 ) and Precambrian craton ( –1 ) and so provide insight into how tectonic strain is partitioned and transferred across a craton margin.

Phylogeography of the sand dune ant Mycetophylax simplex along the Brazilian Atlantic Forest coast: remarkably low mtDNA diversity and shallow population structure.

BackgroundDuring past glacial periods, many species of forest-dwelling animals experienced range contractions. In contrast, species living outside such moist habitats appear to have reacted to Quaternary changes in different ways. The Atlantic Forest represents an excellent opportunity to test phylogeographic hypotheses, because it has a wide range of vegetation types, including unforested habitats covered predominantly by herbaceous and shrubby plants, which are strongly influenced by the harsh environment with strong wind and high insolation. Here, we investigated the distribution of genetic diversity in the endemic sand dune ant Mycetophylax simplex across its known range along the Brazilian coast, with the aim of contributing to the understanding of alternative phylogeographic patterns. We used partial sequences of the mitochondrial gene cytochrome oxidase I and nuclear gene wingless from 108 specimens and 51 specimens, respectively, to assess the phylogeography and demographic history of this species. To achieve this we performed different methods of phylogenetic and standard population genetic analyses.ResultsThe observed genetic diversity distribution and historical demographic profile suggests that the history of M. simplex does not match the scenario suggested for other Atlantic Forest species. Instead, it underwent demographic changes and range expansions during glacial periods. Our results show that M. simplex presents a shallow phylogeographic structure with isolation by distance among the studied populations, living in an almost panmictic population. Our coalescence approach indicates that the species maintained a stable population size until roughly 75,000 years ago, when it underwent a gradual demographic expansion that were coincident with the low sea-level during the Quaternary. Such demographic events were likely triggered by the expansion of the shorelines during the lowering of the sea level.ConclusionsOur data suggest that over evolutionary time M. simplex did not undergo dramatic range fragmentation, but rather it likely persisted in largely interconnected populations. Furthermore, we add an important framework about how both glacial and interglacial events could positively affect the distribution and diversification of species. The growing number of contrasting phylogeographic patterns within and among species and regions have shown that Quaternary events influenced the distribution of species in more ways than first supposed.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-015-0383-4) contains supplementary material, which is available to authorized users.

The three main steps of the Marrakech High Atlas building in Morocco: Structural evidences from the southern foreland, Imini area

The timing of Cenozoic deformation in the intraplate orogen of the High Atlas of Morocco is still a matter of debate. In this work, the deformation calendar has been studied in the southern foreland of the Marrakech High Atlas. Using a structural approach and the mapping of the Cenomanian–Turonian reference layer, we propose a coherent chronology of deformation that proceeded in three stages: (i) a Late Eocene event that set local and minor structures, barely visible nowadays, but important enough to trigger the record of a first detrital pulse; (ii) an Early(?)–Middle Miocene event that is not related to important shortening, setting gravity “sheets” that provoke cover deformation and feed a second detrital pulse; (iii) a Late Pliocene–Quaternary event that is mainly observed through the activity of basement features like the South Atlas Front of the Imini Fault in our studied area and reworks earlier structures. This calendar can partially fit to the geodynamic changes occurring in the western Mediterranean realm during the Cenozoic. Specifically, the Early(?)–Middle Miocene stage of deformation is suggested to be intrinsic to Morocco.

Corrigendum: A low-relief hill in eastern Ontario, Canada, covered by the easily erodible Queenston Formation and derived sediments — probably the result of Quaternary tectonic uplift

The Upper Ordovician Queenston Formation is predominantly a brick red, easily erodible, fine-grained clastic sedimentary rock that is not expected to form topographic highs. Nevertheless, the Queenston, overlain by a relatively thin cover of red unconsolidated sediments derived from it, blankets two low-relief hills. Their combined presence at the top of those hills is curious; therefore, Cholowski Hill, the larger of the two, and its surroundings were studied to try to resolve that apparent contradiction. Cholowski Hill is elongated nearly north–south and overlies a similarly shaped, north–south magnetic anomaly, which is a spur off a generally north-northeast-trending magnetic high. The spatial and geometric relationships of the hill to the magnetic anomaly, a feature of the Precambrian basement, suggest that the hill resulted from repeated tectonic uplift along faults that propagated upward from the basement, though many of them show no surface expression. Two notable exceptions are the North Russell and East Ridge faults that are topographically expressed at the surface and extend along the spine of Cholowski Hill. Their presence and that of Cholowski Hill imply geologically recent uplift. Glacial erratics on, and the smooth character of, the hill imply that it had been overridden by continental ice and was an upland prior to at least the last major glacial advance. Champlain Sea sediments surrounding and encroaching on the lowest part of the hill, but absent from the higher elevations, intimate that Cholowski Hill was not completely covered by those sediments, though it is conceivable that deposited sediments were washed away. The precise age of uplift is unknown, but the characteristics of the hill suggest a Quaternary event.

A low-relief hill in eastern Ontario, Canada, covered by the easily erodible Queenston Formation and derived sediments — probably the result of Quaternary tectonic uplift

The Upper Ordovician Queenston Formation is predominantly a brick red, easily erodible, fine-grained clastic sedimentary rock that is not expected to form topographic highs. Nevertheless, the Queenston, overlain by a relatively thin cover of red unconsolidated sediments derived from it, blankets two low-relief hills. Their combined presence at the top of those hills is curious; therefore, Cholowski Hill, the larger of the two, and its surroundings were studied to try to resolve that apparent contradiction. Cholowski Hill is elongated nearly north–south and overlies a similarly shaped, north–south magnetic anomaly, which is a spur off a generally north-northeast-trending magnetic high. The spatial and geometric relationships of the hill to the magnetic anomaly, a feature of the Precambrian basement, suggest that the hill resulted from repeated tectonic uplift along faults that propagated upward from the basement, though many of them show no surface expression. Two notable exceptions are the North Russell and East Ridge faults that are topographically expressed at the surface and extend along the spine of Cholowski Hill. Their presence and that of Cholowski Hill imply geologically recent uplift. Glacial erratics on, and the smooth character of, the hill imply that it had been overridden by continental ice and was an upland prior to at least the last major glacial advance. Champlain Sea sediments surrounding and encroaching on the lowest part of the hill, but absent from the higher elevations, intimate that Cholowski Hill was not completely covered by those sediments, though it is conceivable that deposited sediments were washed away. The precise age of uplift is unknown, but the characteristics of the hill suggest a Quaternary event.

Thermoluminescence age of quartz xenocrysts in basaltic lava from Oninomi monogenetic volcano, northern Kyushu, Japan

Abstract We determined the eruption age of basaltic rocks by application of thermoluminescence (TL) method, which is often used for TL dating, to quartz. Mafic magma only rarely includes quartz because of their mutual disequilibration. The basaltic lavas reported herein include quartz as xenocrysts, as corroborated by their rounded or anhedral shape. The basaltic lava used for this study is from the Oninomi monogenetic volcano in northern Kyushu, Japan. The volcano eruption was estimated as occurring 7.3–29 ka because the lava exists between two widespread tephras: Aira-Tanzawa ash (26–29 ka) and Kikai-Akahoya ash (7.3 ka). We succeed-ed in collecting ca. 200 mg of quartz by decomposition of 30 kg of the lava samples. TL measurements for the lava indicate the eruption age as 15.8 ± 2.5 ka, which is fairly consistent with the stratigraphical estimation. Although the TL method has played a considerable part in constraining the timescale of Quaternary events, its application has been limited to silicic samples. The present result demonstrates the availability of quartz for dating even of mafic rock.

Diversification across the New World within the ‘blue’ cardinalids (Aves: Cardinalidae)

AbstractAimTo examine the history of diversification of ‘blue’ cardinalids (Cardinalidae) across North and South America.LocationNorth America (including Middle America) and South America.MethodsWe collected 163 individuals of the 14 species of blue cardinalids and generated multilocus sequence data (3193 base pairs from one mitochondrial and three nuclear genes) to infer phylogeographical structure and reconstruct time‐calibrated species trees. We then estimated the ancestral range at each divergence event and tested for temporal shifts in diversification rate.ResultsTwenty‐five lineages of blue cardinalids clustered into two major clades: one confined to North America, and a second concentrated in South America. Blue cardinalids probably originated in North America, but reconstructions were influenced by how migrant taxa were assigned to biogeographical regions. Most of the pre‐Pleistocene divergences between extant taxa occurred in the North American clade, whereas most divergences in South America and adjacent Middle America occurred during the Pleistocene. Despite these differences, the rate of diversification for both clades has been similar and relatively constant over the past 10 million years, with little geographical exchange between North and South America outside the Panamanian isthmus region.Main conclusionsOur reconstruction of the diversification history of blue cardinalids indicates a role of both Neogene and Quaternary events in generating biotic diversity across North and South America. Although ancestral area reconstruction suggests a possible North American origin for blue cardinalids, the occurrence of seasonal migration in this group and their relatives limits inference. Our study highlights the importance of considering ecological and behavioural characteristics together with palaeogeological events in order to gain an understanding of the diversification history of widespread, mobile taxonomic groups.

Comparative phylogeography of two sympatric beeches in subtropical China: Species‐specific geographic mosaic of lineages

In subtropical China, large-scale phylogeographic comparisons among multiple sympatric plants with similar ecological preferences are scarce, making generalizations about common response to historical events necessarily tentative. A phylogeographic comparison of two sympatric Chinese beeches (Fagus lucida and F. longipetiolata, 21 and 28 populations, respectively) was conducted to test whether they have responded to historical events in a concerted fashion and to determine whether their phylogeographic structure is exclusively due to Quaternary events or it is also associated with pre-Quaternary events. Twenty-three haplotypes were recovered for F. lucida and F. longipetiolata (14 each one and five shared). Both species exhibited a species-specific mosaic distribution of haplotypes, with many of them being range-restricted and even private to populations. The two beeches had comparable total haplotype diversity but F. lucida had much higher within-population diversity than F. longipetiolata. Molecular dating showed that the time to most recent common ancestor of all haplotypes was 6.36 Ma, with most haplotypes differentiating during the Quaternary. [Correction added on 14 October 2013, after first online publication: the timeunit has been corrected to ‘6.36’.] Our results support a late Miocene origin and southwards colonization of Chinese beeches when the aridity in Central Asia intensified and the monsoon climate began to dominate the East Asia. During the Quaternary, long-term isolation in subtropical mountains of China coupled with limited gene flow would have lead to the current species-specific mosaic distribution of lineages.

Cladistic biogeography of the Neotropical region: identifying the main events in the diversification of the terrestrial biota.

A cladistic biogeographical analysis was undertaken to identify the main events in the biotic diversification of the terrestrial Neotropical biota. For the 36 animal and plant taxa analysed, a component×area matrix was constructed, associating geographical data only with informative nodes, and it was analysed under implied weights using the software TNT. The general area cladogram obtained shows that the Neotropical region constitutes a monophyletic unit, with a first split separating the Antilles and a second one dividing the continental areas into a north-western and a south-eastern component. Within the north-western component the areas split following the sequence northern Amazonia, south-western Amazonia, north-western South America, and Mesoamerica. Within the south-eastern component the areas split following the sequence south-eastern Amazonia, Chaco, and Parana. The three main components are treated as subregions: Antillean, Amazonian (northern Amazonian, south-western Amazonian, Mesoamerican, and north-western South American dominions), and Chacoan (south-eastern Amazonian, Chacoan, and Parana dominions). Dispersal and vicariant events postulated to explain these pattens might have occurred during the Cretaceous, when the Caribbean plate collided with the Americas, a combination of eustatic sea-level changes and tectonic deformations of the continental platform exposed large parts of South America to episodes of marine transgressions, and the Andean uplift reconfigured the Amazonian area. Tertiary and Quaternary events are assumed to have later induced the diversification within these large biogeographical units.

Fossil Records in the Lythraceae

The Lythraceae (Myrtales) are a family of 28 genera and ca. 600 species constituting with the Combretaceae and sister family Onagraceae a major lineage of the Myrtales and including the former Sonneratiaceae, Duabangaceae, Punicaceae, and Trapaceae. The fossil record of the family is extensive and significant new discoveries have been added to the record in recent years. This review provides a vetted summary of fossils attributed to the Lythraceae, their geographic distributions, and their stratigraphic ranges. It anticipates the use of the information to generate robustly dated molecular phylogenies to accurately reconstruct the evolutionary and biogeographic history of the family. Fossils of 44 genera or form genera have been attributed to the Lythraceae; 24 are accepted here as lythracean. Fourteen of the 28 modern genera have fossil representatives: Adenaria, Crenea, Cuphea, Decodon, Duabanga, Lafoensia, Lagerstroemia, Lawsonia, Lythrum, Pemphis, Punica, Sonneratia, Trapa, and Woodfordia. Ten extinct genera are recognized. The most common kinds of fossil remains are seeds and pollen. The only fossil flower confidently accepted in the family is the extinct genus Sahnianthus from the Early Paleocene of India. The oldest confirmed evidence of the Lythraceae is pollen of Lythrum/Peplis from the Late Cretaceous (early Campanian, 82−81 Ma) of Wyoming. Seeds of Decodon from the late Campanian (73.5 Ma) of northern Mexico are next oldest. Sonneratia, Lagerstroemia, and extinct Sahnianthus first appear in the Paleocene of the Indian subcontinent; extinct Hemitrapa fruits first occur in the Paleocene of northwestern North America. Diversification of the Lythraceae occurred primarily during two major periods of global temperature change, during the Paleocene-Eocene Thermal Maximum and from the middle Miocene forward when temperatures decreased markedly and seasonality and dry-adapted vegetation types became more prominent. Fossils of the Lythraceae from South America and Africa are limited in number. The few dates available for South American genera are comparatively young and diversification of the largest genus, Cuphea (ca. 240 species), was mainly a Quaternary event. A phylogeny of the family is briefly explored and examples of specialized characters occurring in the oldest known genera are noted. The fossil record of the Lythraceae is presently too fragmentary to confidently reconstruct the early history of the family. The record indicates, however, that the family was well-diversified and widely dispersed globally over a wide latitudinal range by the end of the Paleocene.

Phylogenetic analysis and phylogeography of the tetraploid rodentTympanoctomys barrerae(Octodontidae): insights on its origin and the impact of Quaternary climate changes on population dynamics

The allotetraploid Tympanoctomys barrerae has a broad, patchy distribution around salt flats in western Argentina. To gain insights into its phylogenetic relationships, phylogeographical patterns, and origin, seven populations of T. barrerae and its allied taxa were studied through a 1075-bp fragment of cytochrome b and cytochrome oxidase I. Matrilineal phylogenetic relationships were explored with maximum likelihood and Bayesian approaches. The intraspecific genealogy was inferred by median-joining networks. The populational structure was assessed by molecular variance, and the demographic history through coalescence. The tree topology depicted sister-group relationship between Octomys mimax to the pair T. barrerae–Pipanacoctomys aureus, suggesting P. aureus belongs to the maternal lineage that gave rise to T. barrerae. High degrees of intrapopulational variation and the several instances of interpopulational polyphyly suggest range shifts and secondary contact. Consistent with the phylogenetic results, the network analysis revealed two haplotypic lineages depicting genetic admixtures unrelated to the current geographical distribution, and a deep split with the southernmost lineage of Chubut. The origin of T barrerae was estimated at approximately 2.52 Mya, whereas the divergence estimate for Chubut coincides with the end of largest Patagonian glaciation, at 1.47 Mya. Apparently, this population remained isolated during a northward Pleistocenic range shift. The historical demographic patterns of the lineages of T. barrerae fit with a contraction–expansion model coincident with Quaternary cycling events. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 108, 453–469.