Pleistocene Sea-level Changes Research Articles

A review of the MIS 5e highstand deposits from Santa Maria Island (Azores, NE Atlantic): palaeobiodiversity, palaeoecology and palaeobiogeography

The privileged location of Santa Maria Island (Azores archipelago) in the middle of the North Atlantic makes the fossiliferous outcrops on this island of utmost importance to gain a better understanding of how coeval living communities relate to the broader evolutionary and biogeographic history of the Atlantic basin during the late Neogene and the Quaternary. Here we focus on this island's MIS 5e fossil record, offering a comprehensive review on the palaeobiodiversity, palaeoecology and palaeobiogeography of the biota living in the mid North Atlantic during this interglacial. Several studies in oceanic islands stress the huge impact of sea level changes on insular communities. Pleistocene sea-level changes occur during the short-time events known as “Terminations” (associated to glacial/interglacial shifts) as well as with the onset of glaciations (associated to interglacial/glacial shifts). Both are responsible for extinctions and local disappearance of species, bottleneck effects and formation of new species, resulting in community structure changes. This work increases the number of fossil marine taxa reported from the Last Interglacial deposits of Santa Maria to 143 species. All the 19 new records are molluscs (13 gastropods and 6 bivalves), thus increasing the number of fossil molluscs to 136 species. Although thermophilic members of the “Senegalese” tropical fauna were found in these deposits, many of the most emblematic species (e.g., Persististrombus latus (=Strombus bubonius), Cymbula safiana, Harpa doris, Cardita senegalensis, Barbatia plicata, Ctena eburnea or Hyotissa hyotis) are absent, suggesting that they did not reach the Azores. Our results indicate that the main differences between the species composition of the MIS 5e and the present-day shallow-water Azorean communities are probably due to the dropping of sea surface temperature associated with the onset of the last glaciation, which had both direct and indirect effects on species ecology. A group of 21 thermophilic species was directly affected by the lower sea surface temperature, whereas a group of four sand-associated species was indirectly but similarly affected by the lowering of the sea level. Both groups have locally disappeared from the Azores. However, none of the extant endemic species found on the studied MIS 5e outcrops was apparently affected by the lowering SST. In contrast to the biogeographical relationships of the recent Azorean shallow marine molluscs, which are predominantly with the Mediterranean Region, Portugal and with the Madeira and Canary Islands archipelagos, the palaeobiogeographical relationships of the MIS 5e Azorean marine molluscs are mainly with Canaries and West Africa. Despite the general low similarity of the biogeographical relationships between the Azores and Cape Verde Archipelago, on both the recent and the MIS 5e analysis, this similarity is nevertheless higher for the MIS 5e mollusc assemblages, emphasizing the role of Cape Verde as an important source of warm-water species during the Last Interglacial.

A tale of two seas: contrasting patterns of population structure in the small-spotted catshark across Europe

Elasmobranchs represent important components of marine ecosystems, but they can be vulnerable to overexploitation. This has driven investigations into the population genetic structure of large-bodied pelagic sharks, but relatively little is known of population structure in smaller demersal taxa, which are perhaps more representative of the biodiversity of the group. This study explores spatial population genetic structure of the small-spotted catshark (Scyliorhinus canicula), across European seas. The results show significant genetic differences among most of the Mediterranean sample collections, but no significant structure among Atlantic shelf areas. The data suggest the Mediterranean populations are likely to have persisted in a stable and structured environment during Pleistocene sea-level changes. Conversely, the Northeast Atlantic populations would have experienced major changes in habitat availability during glacial cycles, driving patterns of population reduction and expansion. The data also provide evidence of male-biased dispersal and female philopatry over large spatial scales, implying complex sex-determined differences in the behaviour of elasmobranchs. On the basis of this evidence, we suggest that patterns of connectivity are determined by trends of past habitat stability that provides opportunity for local adaptation in species exhibiting philopatric behaviour, implying that resilience of populations to fisheries and other stressors may differ across the range of species.

Effects of fragmentation and sea-level changes upon frog communities of land-bridge islands off the southeastern coast of Brazil.

We investigate the composition of anuran communities of land-bridge islands off the southeastern coast of Brazil. These islands provide natural long-term experiments on the effects of fragmentation in the Brazilian Atlantic Forest (BAF). We hypothesize that Pleistocene sea-level changes, in combination with other abiotic variables such as area and habitat diversity, has affected anuran species richness and community composition on these islands. Data from the literature and collections databases were used to produce species lists for eight land-bridge islands and for the mainland adjacent to the islands. We assess the effects of area, number of breeding habitats and distance to the mainland upon anuran species richness on land-bridge islands. Additionally we use nestedness analysis to quantify the extent to which the species on smaller and less habitat-diverse islands correspond to subsets of those on larger and more diverse ones. We found that area has both direct and indirect effects on anuran species richness on land-bridge islands, irrespective of distance to the mainland. However, on islands with comparable sizes, differences in species richness can be attributed to the number and quality of breeding habitats. Anuran communities on these islands display a nested pattern, possibly caused by selective extinction related to habitat loss. Common lowland pond-breeders were conspicuous by their absence. In the BAF, the conservation of fragments with a high diversity of breeding habitats could compensate for the generally negative effect of small area upon species richness. We suggest that sea-level changes have an important role in shaping composition of anuran species on coastal communities.

Morphotectonics of the Gorringe Bank summit, eastern Atlantic Ocean, based on high-resolution multibeam bathymetry

High-resolution swath bathymetry of the Gorringe Bank, located along the Europe–Africa obliquely convergent plate boundary offshore SW Portugal, allowed investigation of its shallow-depth morphotectonic structure as a contribution to understanding the interplay of sea-level changes and active deformation of the region. Dominant ENE–WSW to NNE–WSW, and subordinate NW–SE trending morphologic alignments were mapped on the Digital Terrain Model (DTM) built from multibeam data for both the Gettysburg and Ormonde summits of the bank. Based on appraisal of regional structural and seismological data, the dominant and subordinate sets are interpreted to reflect dip-slip to left-oblique reverse faults, and normal faults or dyke-like joints, respectively. Several terrace remnants were mapped on the DTM and were grouped into five orders at depths ranging from ∼40 to ∼120 m. Morphological features suggest that the terraces were formed in a coastal environment likely during Middle–Late Pleistocene sea-level changes. The terraces are probably polycyclic, implying minor vertical tectonic motion. However, the whole terrace set (except the deeper and younger one, which was mainly shaped during the LGM lowstand) is consistently up to ∼10 m lower at Ormonde in the east relative to Gettysburg in the west, suggesting displacement across a NNE–SSW striking fault mapped in the saddle between the two seamounts. The structure assemblage is argued to represent the shallow splay system of a crustal-scale fault ramp underlying the bank. The ENE–WSW reverse faults have a southward polarity and, together with the overall northwest tilt of the bank, point to displacement toward the Horseshoe Abyssal Plain to the south at least at upper crustal levels.

Phylogeographic analysis of introns and mitochondrial DNA in the clam Ruditapes decussatus uncovers the effects of Pleistocene glaciations and endogenous barriers to gene flow

Studies on the phylogeography of species inhabiting the Mediterranean and the nearby coasts of the NE Atlantic Ocean (MEDAT) have found subdivision and/or phylogeographic structure in one or more of the Atlantic, western Mediterranean and eastern Mediterranean basins. This structure has been explained as the result of past population fragmentation caused by Pleistocene sea level changes and current patterns of marine circulation. However, the increasing use of nuclear markers has revealed that these two factors alone are not enough to explain the phylogeographic patterns, and an additional role has been suggested for endogenous barriers to gene flow or natural selection. In this article we examined the role of these factors in Ruditapes decussatus, a commercial clam species native to MEDAT. A genetic analysis of 11 populations was carried out by examining 6 introns with a PCR-RFLP technique. We found subdivision in three regions: Atlantic (ATL), western Mediterranean plus Tunisia (WMED), and Aegean and Adriatic seas (AEGAD). Two introns (Ech and Tbp) showed alleles that were restricted to AEGAD. Sequencing a subsample of individuals for these introns indicated that AEGAD-specific alleles were separate clades, thus revealing a phylogeographic brake at the WMED-AEGAD boundary. Sequencing of the mitochondrial COI locus confirmed this phylogeographic break. Dating of the AEGAD mitochondrial haplotypes and nuclear alleles with a Bayesian MCMC method revealed that they shared common ancestors in the Pleistocene. These results can be explained in the framework of Pleistocene sea level drops and patterns of gene flow in MEDAT. An additional observation was a lack of differentiation at COI between the ATL and WMED, in sharp contrast with 4 introns that showed clear genetic subdivision. Neutrality tests did not support the hypothesis of a selective sweep acting on mtDNA to explain the contrasting levels of differentiation between mitochondrial and nuclear markers across the ATL-WMED transition, and we argue that the difference between markers is best explained by the existence of an endogenous genetic barrier, rather than by a physical barrier to larval migration alone.

The geology and morphology of the Antakya Graben between the Amik Triple Junction and the Cyprus Arc

In southeastern Turkey, the NE-trending Antakya Graben forms an asymmetric depression filled by Pliocene marine siliciclastic sediment, Pleistocene to Recent fluvial terrace sediment, and alluvium. Along the Mediterranean coast of the graben, marine terrace deposits sit at different elevations ranging from 2 to 180 m above present sea level, with ages ranging from MIS 2 to 11. A multisegmented, dominantly sinistral fault lying along the graben may connect the Cyprus Arc in the west to the Amik Triple Junction on the Dead Sea Fault (DSF) in the east. Normal faults, which are younger than the sinistral ones, bound the graben’s southeastern margin. The westward escape of the continental İskenderun Block, delimited by sinistral fault segments belonging to the DSF in the east and the Eastern Anatolian Fault in the north caused the development of a sinistral transtensional tectonic regime, which has opened the Antakya Graben since the Pliocene. In the later stages of this opening, normal faults developed along the southeastern margin that caused the graben to tilt to the southwest, leading to differential uplift of Mediterranean coastal terraces. Most of these normal faults remain active. In addition to these tectonic movements, Pleistocene sea level changes in the Mediterranean affected the geomorphological evolution of the area.

Late Pleistocene beach deposits, tectonics and sea-level changes on Cyprus, and their possible association with Neolithic colonization and settlements

Late Pleistocene beach deposits, tectonics and sea-level changes on Cyprus, and their possible association with Neolithic colonization and settlements

Evolutionary history of a widespread Indo-Pacific goby: The role of Pleistocene sea-level changes on demographic contraction/expansion dynamics

Compared to endemics, widespread species are of particular interest to retrace recent evolutionary history. These species have a large population size which provides a clearer genetic signature of past events. Moreover, their wide geographic range increases the potential occurrence of evolutionary events (expansion, divergence, etc.). Here, we used several coalescent-based methods to disentangle the evolutionary history of a widespread amphidromous goby (Sicyopterus lagocephalus), in the light of sea-level variations during the Pleistocene. Using 75 samples recovered from three biogeographic regions (Western Indian Ocean, Melanesia and Polynesia), we analysed a portion of the cytochromeb gene and confirmed three major haplogroups, each specific to a region. Furthermore, we found that: (1) the Melanesian haplogroup was the oldest while the two peripheral regions hosted daughter haplogroups; (2) two centrifugal colonisation events occurred from Melanesia to the periphery, each synchronised with periods of strong paleo-ENSO episodes; (3) the demographic contraction–expansion events were linked to Pleistocene sea-level changes; (4) Melanesia and Polynesia acted as efficient refuges during the Last Glacial Maximum. These results highlight the importance of studying widespread species to better understand the role of climate changes and paleo-oceanography on the evolution of biodiversity.

Underpinning global biogeographical schemes with quantitative data

Underpinning global biogeographical schemes with quantitative data

Historical population connectivity and fragmentation in a tropical freshwater fish with a disjunct distribution (pennyfish,Denariusa bandata)

Pennyfish, Denariusa bandata, are small freshwater fish widely distributed in northern Australia in 4 highly disjunct regions and in the Fly River and Bensbach River drainages in southern Papua New Guinea (PNG). Alternating phases of exposure of the Australia-New Guinea Continental Shelf (ANGCS) during stands of lowered sea levels during Pleistocene glacial phases created a land bridge and fresh/ brackish water habitats that intermittently connected Australia and PNG. Some biogeographic theories and empirical evidence for several freshwater crustaceans suggest that wetlands on the exposed ANGCS during the last glacial maximum were an important conduit for dispersal and gene flow in freshwater species between Australia and PNG and across northern Australia and that connectivity was severed by the most recent sea level rise in the region (,6-8 thousand years before present). We used mitochondrial deoxyribonucleic acid (mtDNA) sequence data to test phylogeographic hypotheses concerning the origin of the disjunct distribution in D. bandata in relation to dispersal-vicariant processes and exposure of the ANGCS during Pleistocene sea level changes. Rather than a late Pleistocene origin associated with the last glacial maximum, the coalescence of the regional populations was in the early- to mid-Pleistocene, and the molecular data indicated that the eastern regional populations split before the northern populations split (i.e., sequential vicariance), whereas the northern populations split contemporaneously (i.e., simultaneous vicariance). The complex mtDNA genealogy for D. bandata also indicated a phylogeographic history in which ancestral lineages were retained in the northwestern part of its distribution, and ancestral haplotype diversity was retained in the Fly River (PNG) population because several divergent clusters of PNG haplotypes were more closely related to Australian haplotypes than to each other.

Molecular inference of a Late Pleistocene diversification shift inNigellas. lat. (Ranunculaceae) resulting from increased speciation in the Aegean archipelago

AbstractAim To infer the temporal course and geographical mode of speciation in Mediterranean/Southwest AsianNigellas. lat.Location Mediterranean Basin, Aegean archipelago.Methods Phylogenies forNigellaL. andGaridellaL. (= Nigellas. lat.) were obtained from maximum‐likelihood analyses of internal transcribed spacer (ITS) sequences. Diversification through time was analysed by log lineages‐through‐time (LTT) plots and survival analyses. Relative node age estimates were regressed against the degree of sympatry between sister clades to infer the predominant mode of geographical speciation inNigellas. lat.Results The Late Pleistocene radiation of theNigella arvensiscomplex in the Aegean region caused a significant departure from a stochastic speciation/extinction process of diversification during the evolution ofNigellas. lat., a lineage of (at least) Late Miocene origin. Speciation withinNigellas. lat. predominantly took place in allopatry.Main conclusions No significant effect on diversification rate was found regarding the establishment of a Mediterranean‐type climate, or the onset of the Quaternary climatic oscillations. Rather, the accelerated rate of speciation in theN. arvensiscomplex is plausibly related toincreasedopportunities for allopatric speciation afforded by the (palaeo)geographical complexity of the Aegean archipelago combined with Late Pleistocene changes in climate and sea level. The evolution of self‐pollination and associated changes in habitat preference and flowering time further augmented speciation and niche differentiation within the complex, but these changes did not act as the primary promoters of the radiation process.

Pleistocene raised marine deposits of the Cap Bon peninsula (N–E Tunisia): Records of sea-level highstands, climatic changes and coastal uplift

Morphostratigraphic and sedimentological studies were undertaken in the Cap Bon peninsula, north-eastern Tunisia. These studies have identified a series of middle to late Pleistocene–age marine deposits discontinuously cropping out on three raised platforms (Pf I, Pf II and Pf III). These stepped marine platforms (terraces) were related to the interplay between Pleistocene sea-level changes and progressive uplift movement during Quaternary period. We present here a description of facies organization and stratigraphic characteristics of the platform deposits, and their relation with eustatic and climatic variations. All the marine platforms unconformably overlie a Mio-Pliocene and Quaternary slope succession. The sedimentary sequences represented by mixed carbonate and siliciclastic bodies are related to the succession of highstand shorelines and contrasting climate conditions. The intercalated soils and calcretization occurred during episodes of relative sea-level fall. The oldest platforms (Pf I and Pf II), found at an elevation of about + 100 m and + 60 m respectively, have so far no equivalent in the northern, in the eastern or in the southern coasts of Tunisia. They are correspondingly attributed to MIS 11/13 and MIS 9/11. The youngest and lowest platform (Pf III) attains an altitude of + 40 m and shows three high-frequency cycles of sea-level rise and fall, probably associated with Marine Isotope Stage (MIS) 5e and MIS 7.

Elucidating geological and biological processes underlying the diversification of Sulawesi tarsiers

Because of their exceptionally long independent evolution, a range diminution of their Eocene relatives, and a remarkable subsequent diversification in Southeast Asia, tarsiers are of particular importance to evolutionary primatologists. Little is known, however, on the processes shaping the radiation of these small enigmatic primates-especially on the Indonesian island of Sulawesi, their center of endemism. Geological reconstructions and progress in applying DNA sequence information to divergence dating now provide us with the tools and background to comprehend tarsier dispersal. Here, we describe effects of plate-tectonic movements, Pleistocene sea level changes, and hybridization on the divergence of central Sulawesi tarsiers. We analyzed 12 microsatellites, the cytochrome b gene, the hypervariable region I of the mitochondrial control region, and the sex-determining region on the Y-chromosome from 144 specimens captured along a transect crossing a species boundary and a contact zone between 2 microplates. Based on these differentially inherited genetic markers, geographic information, and recordings of vocalizations, we demonstrate that the species boundary coincides with a tectonic suture. We estimate the most recent common ancestor of the 2 taxa to have lived 1.4 Mya, we describe asymmetrical introgressive hybridization, and we give evidence of unbiased dispersal in one species and male-biased dispersal in another species. This study exemplifies that the distribution of tarsier acoustic forms on Sulawesi is consistent with the allocation of genetic variability and that plate-tectonic and glacial events have left traceable marks in the biogeography of this island's unique fauna.

Preface: The Heidelberg Basin Drilling Project

Abstract. Since Late Pliocene / Early Pleistocene, the River Rhine, as one of the largest European rivers, has acted as the only drainage system that connected the Alps with Northern Europe, especially the North Sea. Along its course from the Alps to the English Channel the river passes several geomorphological and geological units, of which the Upper Rhine Graben acts as the major sediment trap. Whereas the potential of sediment preservation of the alpine foreland basins is low due to the high dynamics of the system, and the area of deposition close to the North Sea was significantly affected several times by Pleistocene sea level changes, the ongoing subsidence of the Upper Rhine Graben offers a unique potential for a continuous sediment accumulation and preservation.

What for the future of the Jardine River Painted Turtle?

The Painted Turtle Emydura subglobosa is widely distributed in southern Papua New Guinea and Irian Jaya, where it inhabits the permanent freshwater swamps of adjacent coastal river systems (Lovich et al. 1983; Georges et al. 2006). Emydura subglobosa has also been recorded on mainland Australia, but only from the Jardine River in far northern Cape York Peninsula where it is colloquially named the Jardine River Painted Turtle (Cann 1998). The separation of these two disjunct populations is presumed to be due to Pleistocene sea level changes about 12,000?18,000 years BP (Georges and Thomson 2006). The taxonomic affinities of this species complex remain unresolved (Georges and Adams 1996).

Overpressure within upper continental slope sediments from CPTU data, Gulf of Lion, NW Mediterranean Sea

Data from in situ piezocone tests (CPTU) and laboratory analyses are utilized for the interpretation of the stress history of Quaternary sedimentary sequences in the upper continental slope of the Gulf of Lion, northwestern Mediterranean Sea. A CPTU based preconsolidation pressure profile referenced to the current effective stress indicates that the deposit is underconsolidated from 12 meters below the seafloor (mbsf) down to at least 150 mbsf. Excess pore pressure below 12 mbsf is further supported by results from oedometer and dissipation tests. Subseafloor pockmarks and indications of free gas in seismic reflection profiles reveal four main overpressure sources (SI–SIV) with overpressure ratios >0.3 at subseafloor depths coinciding with levels where the dominantly silty-clayey sediment contains increased proportions of sand. We relate the excess pore pressure related to free gas due to gas exsolution processes and sea level variations driven by Pleistocene sea level changes.

Archaeology of the continental shelf: Marine resources, submerged landscapes and underwater archaeology

We provide a critical review of the evidence for the long-term use of marine resources and coastal environments in human evolution and later development. We emphasise the importance of the coastal archaeological record in understanding patterns of human settlement and dispersal and draw attention to the large potential biases introduced by the destructive or obscuring effects of Pleistocene sea-level change. We note that lowered sea levels have been the norm for most of the Pleistocene and that periods of high sea level have been too short-lived to provide other than a fragmentary coastal record and one that is beset with ambiguities and uncertainties. We examine the geological processes of coastal uplift and underwater preservation that may help to mitigate these biases. Coastlines elevated by isostatic and tectonic processes, or with very steep offshore drop-offs at plate boundaries, are important in providing a potential window into coastal landscapes and archaeology formed during periods of lowered sea level. However, we conclude that the opportunities afforded by these geological factors are too limited to obviate the need for underwater exploration. We review the evidence now available from submerged landscapes across the Africa–Eurasia interface from the Atlantic coastlines of Northwest Europe to the southern Red Sea. We show that geomorphological conditions for the preservation of archaeological and palaeoenvironmental data are commonly present, that much material has already been discovered, and that new techniques, technologies and projects are providing the momentum for a rapidly expanding field of investigation. The results do not simply add to what we already know from sites on land, but are likely to produce qualitatively different evidence for coastal adaptations and landscapes that have no analogue on present-day coastlines. We note the strong probability that many coastal landscapes exposed at lowered sea level provided relatively fertile and productive refugia for plants, land mammals and humans at a time when increased aridity would have reduced or deterred hinterland occupation. We conclude that underwater investigation is essential if hypotheses of early human adaptation and dispersal are to be fully tested.

Origin of the eastern brownsnake, Pseudonaja textilis (Dumeril, Bibron and Dumeril) (Serpentes: Elapidae: Hydrophiinae) in New Guinea: evidence of multiple dispersals from Australia, and comments on the status of Pseudonaja textilis pughi Hoser 2003

Pseudonaja textilis is a widespread and common snake in eastern parts of Australia, but its distribution in New Guinea is poorly understood, and the origin of the New Guinea populations and its timing have been the subject of much speculation. Phylogenetic analysis of mitochondrial DNA sequences from three New Guinea populations of P. textilis indicates that New Guinea was colonised from two independent eastern and western migration routes most likely in the Pleistocene. One dispersal event from northern Queensland led to the populations in eastern New Guinea (Milne Bay, Oro and Central Provinces, Papua New Guinea), whereas another, from Arnhem Land to central southern New Guinea, led to the populations from the Merauke area, Indonesian Papua. The results are consistent with the effects of Pleistocene sea level changes on the physical geography of Australasia, and are thus suggestive of a natural rather than anthropogenic origin of the New Guinea populations. The taxonomic status of the New Guinean populations is discussed.

Coastlines, Submerged Landscapes, and Human Evolution: The Red Sea Basin and the Farasan Islands

ABSTRACT We examine some long-standing assumptions about the early use of coastlines and marine resources and their contribution to the pattern of early human dispersal, and focus on the southern Red Sea Basin and the proposed southern corridor of movement between Africa and Arabia across the Bab al-Mandab Straits. We reconstruct relative sea levels in light of isostatic and tectonic effects, and evaluate their paleogeographical impact on the distribution of resources and human movement. We conclude that the crossing of the Bab al-Mandab posed little significant or long-lasting physical or climatic barrier to human transit during the Pleistocene and that the emerged continental shelf during periods of low sea level enhanced the possibilities for human settlement and dispersal around the coastlines of the Arabian Peninsula. We emphasize the paleogeographical and paleoenvironmental significance of Pleistocene sea-level change and its relationship with changes in paleoclimate, and identify the exploration of the submerged continental shelf as a high priority for future research. We conclude with a brief description of our strategy for underwater work in the Farasan Islands and our preliminary results.

Molecular signatures of Pleistocene sea‐level changes that affected connectivity among freshwater shrimp in Indo‐Australian waters

A major paradigm in evolutionary biology asserts that global climate change during the Pleistocene often led to rapid and extensive diversification in numerous taxa. Recent phylogenetic data suggest that past climatic oscillations may have promoted long-distance marine dispersal in some freshwater crustacea from the Indo-Australian Archipelago (IAA). Whether this pattern is common, and whether similar processes are acting on diversification below the species level is unknown. We used nuclear and mitochondrial molecular variation in a freshwater-dependent decapod crustacean (Macrobrachium rosenbergii), sampled widely from the IAA, to assess the impact of Pleistocene sea-level changes on lineage diversification in this species. Fitting of an isolation with migration model enabled us to reject ongoing migration among lineages, and results indicate that isolation among both mainland-mainland and mainland-island lineages arose during the mid-Pleistocene. Our data suggest a scenario of widespread marine dispersal during Pleistocene glacial maxima (in support of the 'Pleistocene marine dispersal hypothesis') when sea levels were low, and geographical distances between fresh watersheds were greatly reduced, followed by increased isolation as sea levels subsequently rose.