Paleogene stable isotope events

The oxygen isotope record in Paleogene benthic Foraminifera shows that at the base of the Paleogene the ocean deep waters had a temperature of about 10°C, rising to about 12°C at the base of the Eocene and cooling between 51 Ma and 49 Ma to about 9°C. The most dramatic event occurred just after the Eocene/Oligocene boundary, at about 35.8 Ma, when ocean deep waters cooled by several degrees within 10⁴–10⁵ yr, probably in association with temporary glaciation in the Antarctic region. Another more intense glacial event in Antarctica may have occurred later in the Oligocene, at about 31 Ma and a third near the top of the Oligocene at 24 Ma.In the marine carbon isotope record a very rapid negative excursion occurred precisely at the Cretaceous/Tertiary boundary. A recovery to unusually positive values in the Late Paleocene was followed by a second negative excursion close to the Paleocene/Eocene boundary that was even more extreme in magnitude although it was not as rapid. These major carbon isotope events permit very accurate stratigraphic correlation; there are many other smaller features in the carbon isotope record that will also prove useful for this purpose.     

Primate origins: implications of a cretaceous ancestry

It has long been accepted that the adaptive radiation of modern placental mammals, like that of modern birds, did not begin until after the Cretaceous/Tertiary (K/T) boundary 65 million years (Ma) ago, following the extinction of the dinosaurs. The first undoubted fossil relatives of modern primates appear in the record 55 Ma ago. However, in agreement with evidence from molecular phylogenies calibrated with dates from denser parts of the fossil record, a statistical analysis of the primate record allowing for major gaps now indicates a Cretaceous origin of euprimates 80-90 Ma ago. If this interpretation is correct, primates overlapped with dinosaurs by some 20 Ma prior to the K/T boundary, and the initial radiation of primates was probably truncated as part of the major extinction event that occurred at the end of the Cretaceous. Following a review of evidence for an early origin of primates, implications of this are discussed with respect to the likely ancestral condition for primates, including a southern continental area of origin and moderately large body size. The known early Tertiary primates are re-interpreted as northern continental offshoots of a 'second wave' of primate evolution.     

Paleoecological patterns in molluscan extinctions and recoveries: comparison of the Cretaceous-Paleogene and Eocene-Oligocene extinctions in North America

Exposures across the Cretaceous-Tertiary (K-T) and Eocene-Oligocene (E-O) boundaries, in Texas and Mississippi, respectively, probably represent the most complete and best-preserved fossil molluscan sequences across these boundary intervals in the world. Outcrops from both boundaries contain pristine aragonitic and calcitic molluscan shells, which were deposited in fine-grained sediments from open marine environments. The K-T and the E-O extinctions exhibit very different recovery patterns, probably reflecting very different causes as well as magnitudes of extinction.The K-T sequence contains a molluscan fossil record that is consistent with an abrupt extinction event at the K-T boundary and a prolonged initial recovery in hostile oceanographic conditions. The uppermost 10 m of Upper Cretaceous sediments contain a diverse (approximately 40 species) molluscan fauna dominated by suspension feeders. The earliest Paleocene sediments immediately above the tsunami bed contain an impoverished fauna dominated by deposit feeders. The Paleocene fauna slowly climbs in diversity but remains relatively impoverished and dominated by deposit feeders for several hundred thousand years after the extinction in conjunction with anomalous δ¹³C values that suggest prolonged suppression of marine primary productivity. Diverse suspension-feeder dominated molluscan assemblages reappear with the resumption of normal conditions of primary production. In the long term, early to middle Paleocene gamma diversity includes evolutionary “bloom taxa,” families that exhibit unusual speciation bursts that subside in the Eocene. Total diversity for the Gulf Coast does not approach Cretaceous levels until the Late Eocene representing a total recovery interval of nearly 25 million years.While the E-O event also reflects a molluscan extinction rate of over 90% in the Gulf of Mexico, there are no signs of hostile environmental conditions in the recovery fauna. Early Oligocene molluscan assemblages are diverse and dominated by suspension feeders characteristic of normal marine conditions. The hiatus at the E-O boundary, however, could have obscured a short-term recovery fauna. There is also no sign of long-term perturbation by the E-O extinction. There are no bloom taxa and gamma diversity approaches pre-extinction levels within a few million years. The overall pattern of the E-O extinction is consistent with extinction (and/or migration) associated with long-term cooling.     

L’Explosion cambrienne ou l’émergence des écosystèmes modernes

Marine ecosystems with complex trophic structure and dominated by animals started to build up in the Early Cambrian. Fossil evidence from exceptional fossil localities such as the Chengjiang Lagerstätte from South China indicate a high level of biological interactivity (e.g. prey–predator relationships) and the colonization of a wide range of pelagic and benthic niches by predators, scavengers, and detritus and suspension feeders. Swimmers are numerous, but there is no evidence for the extensive occupation of the water column by the Early Cambrian. On the contrary, animal life may have concentrated in hyperbenthic environments, close to the sea bottom. This would have been the initial step towards the colonization of the whole pelagic realm and the building-up of pelagic food chains. A chain of biotic innovations and events seems to have catalyzed both the animal diversification and the build-up of a completely new type of ecosytem, with: (1) the achievement of complex nervous systems, visual organs and motor functions; (2) the introduction of new selective pressure (e.g. predation and feed-back effects); and (3) the colonization of new niches. The role of environmental factors (e.g. oxygen, water chemistry, climate) may have been important in the early stages of metazoan evolution, but was probably negligible in the ecological turnover itself that takes place in the Early Cambrian. Close resemblances between the trophic structure of present-day ecosystems and that of Cambrian ones are confirmed by fossil data and recent mathematical models. This unprecedented increase of interdependence between animal species and trophic levels probably increased the general stability of marine ecosystems, but made them for the first time in their history, highly vulnerable to environmental perturbations. This will largely influence the post-Cambrian evolution of the marine world.     

Fish in Reservoirs

In all reservoirs the fish fauna is recruited from their riverine antecedents. The nature of the riverine environment, created by its unstable hydrological regime, favours the evolution of generalist species. Of these species, only a few are preadapted to lacustrine conditions. When riverine fish communities are trapped in a reservoir, most of the fish stay close to the shore, the mouth of tributaries and in shallows. The pelagic and deep waters are poorly utilized and the yield of fish is below the natural productivity of these water bodies, especially in the case of deep and large reservoirs. This occurs unless the dammed river contains fish species from families which are preadapted for lacustrine conditions. A positive correlation between the percentage of pelagic fish and the total yield of fish in reservoirs indicates that the pelagial represents a vacant habitat, only seldom invaded by riverine species. This situation probably applies to the deep water of reservoirs too, although sufficient data to demonstrate this are not available. The littoral region of reservoirs is utilized by some generalists of euryoecious species derived from the indigenous riverine fauna which may be preadapted for lacustrine conditions. If such preadapted lacustrine species are not present, the introduction of lacustrine species or those preadapted for the lacustrine environment is desirable under certain circumstances. However, caution must be exercised in any introduction.     

Nitrogen cycling in coastal marine ecosystems

It is generally considered that nitrogen availability is one of the major factors regulating primary production in temperate coastal marine environments. Coastal regions often receive large anthropogenic inputs of nitrogen that cause eutrophication. The impact of these nitrogen additions has a profound effect in estuaries and coastal lagoons where water exchange is limited. Such increased nutrient loading promotes the growth of phytoplankton and fast growing pelagic macroalgae while rooted plants (sea-grasses) and benthic are suppressed due to reduced light availability. This shift from benthic to pelagic primary production introduces large diurnal variations in oxygen concentrations in the water column. In addition oxygen consumption in the surface sediments increases due to the deposition of readily degradable biomass. In this review the physico-chemical and biological factors regulating nitrogen cycling in coastal marine ecosystems are considered in relation to developing effective management programmes to rehabilitate seagrass communities in lagoons currently dominated by pelagic macroalgae and/or cyanobacteria.     

Benthic-pelagic interactions in shallow water columns: an experimentalist's perspective

Shallow water column benthic and pelagic communities are thought to be linked by trophic relationships, through life history or ontogenetic links, and by biologically or physically-mediated resuspension or sedimentation processes. It is often confusing and sometimes misleading to focus only on benthic or only on pelagic components of aquatic food webs, even though the literature on shallow water column experiments contains few experiments that give a balanced view of these components, or interactions between components in different habitats. The rarity of balanced experiments is especially troublesome because the most common types of manipulations in shallow water column experiments (fish and nutrients) often have rapid, direct effects on both kinds of habitats, or easily recognized indirect links between the two habitats that go unevaluated. Despite a large experimental literature on pelagic and benthic foodwebs (with less on both in the same systems), there appears to be continuing uncertainty about the importance to pelagic productivity of nutrients released from resuspended sediments, the role of macrobenthos in controlling plankton, and the efficacy and interaction of trophic cascades between pelagic and benthic communities.     

Ostracodes bathyaux du Crétacé terminal - Éocène moyen en Atlantique tropical (Plateau de Demerara, Leg 207)

Ostracode faunal assemblages which lived in bathyal environments are analysed from uppermost Maastrichtian - middle Eocene sediments of sites 1260 and 1261, drilled on the distal margin of Demerara, off Surinam (Leg 207, western tropical Atlantic). As for numerous other groups, the Cretaceous/Tertiary mass extinction event led to the disappearance of numerous bathyal ostracode species and it was followed by a very slow recovery during the Palaeocene. It appears that this extinction event was more devastating for detritus-feeder ostracode species than for filter or silt-eater groups, which crossed the K/T boundary without any or little morphological change. This extinction selectivity may be explained by the drop in productivity of surface waters which took place at the K/T boundary. Finally, psychrospheric ostracode species were encountered in Middle Eocene sediments, confirming thus the general cooling of deep oceanic realm recognised in general for this time interval.     

Biogeochemical responses following coral mass spawning on the Great Barrier Reef: pelagic–benthic coupling

This study quantified how the pulse of organic matter from the release of coral gametes triggered a chain of pelagic and benthic processes during an annual mass spawning event on the Australian Great Barrier Reef. Particulate organic matter (POM) concentrations in reef waters increased by threefold to 11-fold the day after spawning and resulted in a stimulation of pelagic oxygen consumption rates that lasted for at least 1 week. Water column microbial communities degraded the organic carbon of gametes of the broadcast-spawning coral Acropora millepora at a rate of >15% h⁻¹, which is about three times faster than the degradation rate measured for larvae of the brooding coral Stylophora pistillata. Stable isotope signatures of POM in the water column reflected the fast transfer of organic matter from coral gametes into higher levels of the food chain, and the amount of POM reaching the seafloor immediately increased after coral spawning and then tailed-off in the next 2 weeks. Short-lasting phytoplankton blooms developed within a few days after the spawning event, indicating a prompt recycling of nutrients released through the degradation of spawning products. These data show the profound effects of coral mass spawning on the reef community and demonstrate the tight recycling of nutrients in this oligotrophic ecosystem.     

Phenology of dormancy in a Virginia population ofMesocyclops edax (Crustacea: Copepoda)

The abundance and age structure of a Virginia, USA population ofMesocyclops edax that undergoes dormancy in an eutrophic lake was investigated from October 1988 through March 1989. During the fall all instars ofM. edax were present in the water column. By early December, only CI-CIV instars were found. M. edax was not found in the water column in January, but sediment cores in February revealed the presence of CIV's and adult females distributed predominantly at 0–3 cm and in lesser abundance at 3–6 cm. NoM. edax were found below 6 cm. By early March animals in the sediments emerged from dormancy and colonized the water column; CIV's and adult females predominated while CV's and adult males were present in small numbers. Dormancy of both juvenile and adult instars within one population is unusual among animal species. Life histories including multiple dormant stages may be more important for the adaptive evolution of cyclopoid copepods than calanoid copepods in freshwater habitats.     

Continental drift, paleoclimatology, and the evolution and biogeography of birds

An analysis is presented of the influence that late Mesozoic and Tertiary paleogeography and paleoclimatology may have had on the evolution and biogeography of birds. Many intercontinental connections, especially in the Southern Hemisphere, persisted until the late Cretaceous and/or early Tertiary. Moreover, climates at these times were warmer and more equable than in the late Tertiary, and birds could breed in and disperse through high latitudes. It is concluded that a number of avian orders and families had their origin in Gondwanaland and predrift configurations of the continents were major determinants of their biogeography. Penguins, ratites, galliforms, and suboscines among others are the best examples. Tropical-subtropical Eurasia was probably the centre of origin for the oscines, and primitive stocks entered the New World mostly through Beringia and mostly prior to the Miocene (but also via a North Atlantic land connection prior to the early Eocene). Continental drift and paleoclimatology have clearly influenced the evolution and biogeography of birds, and future advances in the systematics of the higher taxa will undoubtedly provide further confirmation of this.     

豆科黄华族植物地理学的初步研究

在系统学业伦和地理分布及古植物学资源的基础上,利用形态－地理学的原理和方法,对豆科Papilionaceae黄华族和Tribe Thermopsideae进行了植物地理学的初步研究。结果表明,（１）黄华族可能是古地中海起源的,它的起源地在古北大陆的南岸,大约相当于现在的中纬度地区;（２）起源时间能早于第三纪,大约处白垩纪末和始新世之间。当时有一个所谓的“北热带植物群”Ｂoreotropical Flora发生;（３）本族６个属基本上构成一个比较自然的单元。它们是由原始槐族类祖先演化而来的;（４）木本类是本族原始的,早出的类群,它们基本上处于遗状态;草本类是本族进化的、晚出的类群,们种类多,分布区有扩大的趋势;（５）Ｔhermopsis间断分布于亚洲（包括中亚和东亚）、北美（包括北美东部和北美西部。东亚太平洋沿岸和北美大西洋沿岩最有可能是它的原始保存地,而不是起源地,它们主要是通过古地中海海道而发生联系的,造成原始类群星散分布的格局不是由一次,而是多次地史和气候变化的结果;（６）晚第三纪亚洲腹地造山运动引起的喜马拉雅山的降起和青藏高原的抬升,以及北美落基山山体抬升引起的水温条件的急剧变化是某些类群（包括Piptanthus和Thermopsis)物种局部分化的主要动力。     

Variable arrangement of 5S ribosomal genes within the ribosomal DNA repeats of arthropods.

The polymerase chain reaction and hybridization to genomic blots were used to investigate whether the previously observed inclusion of 5S ribosomal RNA genes in the 28S-18S ribosomal DNA intergenic regions of some crustacean species (copepods) could also be detected in other arthropods. Such an arrangement was found not only in other calanoid copepod species but also in a cirriped, an euphausid, and a spider. It is interesting that species from two different calanoid copepod genera do not have this type of arrangement. We conclude that the inclusion of 5S ribosomal RNA genes within the ribosomal DNA repeats has probably occurred repeatedly during the evolution of arthropod species and that the mechanism(s) responsible for these insertions could also be responsible for their loss.     

Redox proteins in mammalian cell death: an evolutionarily conserved function in mitochondria and prokaryotes

Mammalian cell mitochondria are believed to have prokaryotic ancestry. Mitochondria are not only the powerhouse of energy generation within the eukaryotic cell but they also play a major role in inducing apoptotic cell death through release of redox proteins such as cytochrome c and the apoptosis-inducing factor (AIF), a flavoprotein with NADH oxidase activity. Recent evidence indicates that some present day prokaryotes release redox proteins that induce apoptosis in mammalian cells through stabilization of the tumour suppressor protein p53. p53 interacts with mitochondria either directly or through activation of the genes for pro-apoptotic proteins such as Bax or NOXA or genes that encode redox enzymes responsible for the production of reactive oxygen species (ROS). The analogy between the ancient ancestors of present day bacteria, the mitochondria, and the present day bacteria with regard to their ability to release redox proteins for triggering mammalian cell death is an interesting example of functional conservation during the hundreds of millions of years of evolution. It is possible that the ancestors of the present day prokaryotes released redox proteins to kill the ancestors of the eukaryotes. During evolution of the mitochondria from prokaryotes as obligate endosymbionts, the mitochondria maintained the same functions to programme their own host cell death.     

The Submarine Volcano Eruption off El Hierro Island: Effects on the Scattering Migrant Biota and the Evolution of the Pelagic Communities

The submarine volcano eruption off El Hierro Island (Canary Islands) on 10 October 2011 promoted dramatic perturbation of the water column leading to changes in the distribution of pelagic fauna. To study the response of the scattering biota, we combined acoustic data with hydrographic profiles and concurrent sea surface turbidity indexes from satellite imagery. We also monitored changes in the plankton and nekton communities through the eruptive and post-eruptive phases. Decrease of oxygen, acidification, rising temperature and deposition of chemicals in shallow waters resulted in a reduction of epipelagic stocks and a disruption of diel vertical migration (nocturnal ascent) of mesopelagic organisms. Furthermore, decreased light levels at depth caused by extinction in the volcanic plume resulted in a significant shallowing of the deep acoustic scattering layer. Once the eruption ceased, the distribution and abundances of the pelagic biota returned to baseline levels. There was no evidence of a volcano-induced bloom in the plankton community.     

First Evidence for a Massive Extinction Event Affecting Bees Close to the K-T Boundary

Bees and eudicot plants both arose in the mid-late Cretaceous, and their co-evolutionary relationships have often been assumed as an important element in the rise of flowering plants. Given the near-complete dependence of bees on eudicots we would expect that major extinction events affecting the latter would have also impacted bees. However, given the very patchy distribution of bees in the fossil record, identifying any such extinctions using fossils is very problematic. Here we use molecular phylogenetic analyses to show that one bee group, the Xylocopinae, originated in the mid-Cretaceous, coinciding with the early radiation of the eudicots. Lineage through time analyses for this bee subfamily show very early diversification, followed by a long period of seemingly no radiation and then followed by rapid diversification in each of the four constituent tribes. These patterns are consistent with both a long-fuse model of radiation and a massive extinction event close to the K-T boundary. We argue that massive extinction is much more plausible than a long fuse, given the historical biogeography of these bees and the diversity of ecological niches that they occupy. Our results suggest that events near the K-T boundary would have disrupted many plant-bee relationships, with major consequences for the subsequent evolution of eudicots and their pollinators.     

Inferring the biogeographic origins of inter‐continental disjunct endemics using a Bayes‐DIVA approach

The arcto‐Tertiary relictual flora is comprised of many genera that occur non‐contiguously in the temperate zones of eastern Asia, Europe, eastern North America, and western North America. Within each distributional area, species are typically endemic and may thus be widely separated from closely related species within the other areas. It is widely accepted that this common pattern of distribution resulted from of the fragmentation of a once more‐continuous arcto‐Tertiary forest. The historical biogeographic events leading to the present‐day disjunction have often been investigated using a phylogenetic approach. Limitations to these previous studies have included phylogenetic uncertainty and uncertainty in ancestral range reconstructions. However, the recently described Bayes‐DIVA method handles both types of uncertainty. Thus, we used Bayes‐DIVA analysis to reconstruct the stem lineage distributions for 185 endemic lineages from 23 disjunct genera representing 17 vascular plant families. In particular, we asked whether endemic lineages within each of the four distributional areas more often evolved from (1) widespread ancestors, (2) ancestors dispersed from other areas, or (3) endemic ancestors. We also considered which of these three biogeographic mechanisms may best explain the origins of arcto‐Tertiary disjunct endemics in the neotropics. Our results show that eastern Asian endemics more often evolved from endemic ancestors compared to endemics in Europe and eastern and western North America. Present‐day endemic lineages in the latter areas more often arose from widespread ancestors. Our results also provide anecdotal evidence for the importance of dispersal in the biogeographic origins of arcto‐Tertiary species endemic in the neotropics.     

Vertical Migrations of a Deep-Sea Fish and Its Prey

It has been speculated that some deep-sea fishes can display large vertical migrations and likely doing so to explore the full suite of benthopelagic food resources, especially the pelagic organisms of the deep scattering layer (DSL). This would help explain the success of fishes residing at seamounts and the increased biodiversity found in these features of the open ocean. We combined active plus passive acoustic telemetry of blackspot seabream with in situ environmental and biological (backscattering) data collection at a seamount to verify if its behaviour is dominated by vertical movements as a response to temporal changes in environmental conditions and pelagic prey availability. We found that seabream extensively migrate up and down the water column, that these patterns are cyclic both in short-term (tidal, diel) as well as long-term (seasonal) scales, and that they partially match the availability of potential DSL prey components. Furthermore, the emerging pattern points to a more complex spatial behaviour than previously anticipated, suggesting a seasonal switch in the diel behaviour mode (benthic vs. pelagic) of seabream, which may reflect an adaptation to differences in prey availability. This study is the first to document the fine scale three-dimensional behaviour of a deep-sea fish residing at seamounts.     

Journey through the past: 150 million years of plant genome evolution

The genome sequence of the plant model organism Arabidopsis thaliana was presented in December of the year 2000. Since then, the 125 Mb sequence has revealed many of its evolutionary secrets. Through comparative analyses with other plant genomes, we know that the genome of A. thaliana, or better that of its ancestors, has undergone at least three whole genome duplications during the last 120 or so million years. The first duplication seems to have occurred at the dawn of dicot evolution, while the later duplications probably occurred <70 million years ago (Ma). One of those younger genome-wide duplications might be linked to the K-T extinction. Following these duplication events, the ancestral A. thaliana genome was hugely rearranged and gene copies have been massively lost. During the last 10 million years of its evolution, almost half of its genome was lost due to hundreds of thousands of small deletions. Here, we reconstruct plant genome evolution from the early angiosperm ancestor to the current A. thaliana genome, covering about 150 million years of evolution characterized by gene and genome duplications, genome rearrangements and genome reduction.     

Vertical ecology of the pelagic ocean: classical patterns and new perspectives

Applications of acoustic and optical sensing and intensive, discrete‐depth sampling, in concert with collaborative international research programmes, have substantially advanced knowledge of pelagic ecosystems in the 17 years since the 1996 Deepwater Fishes Symposium of the Fisheries Society of the British Isles. Although the epipelagic habitat is the best‐known, and remote sensing and high‐resolution modelling allow near‐synoptic investigation of upper layer biophysical dynamics, ecological studies within the mesopelagic and deep‐demersal habitats have begun to link lower and upper trophic level processes. Bathypelagic taxonomic inventories are far from complete, but recent projects (e.g. MAR‐ECO and CMarZ, supported by the Census of Marine Life programme) have quantitatively strengthened distribution patterns previously described for fishes and have provided new perspectives. Synthesis of net and acoustic studies suggests that the biomass of deep‐pelagic fishes may be two to three orders of magnitude greater than the total global commercial fisheries landings. Discrete‐depth net sampling has revealed relatively high pelagic fish biomass below 1000 m in some regions, and that gelatinous zooplankton may be key energy vectors for deep‐pelagic fish production. Lastly, perhaps, the most substantive paradigm shift is that vertical connectivity among fishes across classical depth zones is prevalent– suggesting that a whole‐water column approach is warranted for deep ocean conservation and management.