Successive Extinction Research Articles

Biological Interaction as a Possible Ultimate Driver in the Local Extinction of Cedrus atlantica in the Iberian Peninsula

The presence of Cedrus atlantica on the European continent, including, especially, the determination of the time of its disappearance from the Iberian Peninsula, is one of the most controversial issues in recent decades regarding the successive extinction of conifers in the Western Mediterranean. This work propounds the possibility that C. atlantica and Pinus nigra could have co-habited in the past, mutually excluding each other in the areas with suitable conditions for both species, where, ultimately, the one that was the most competitive would have remained. The niche overlap in the two-dimensional ecological space was analyzed. In addition, the potential distribution of both species in the Western Mediterranean today and two past periods (Last Glacial Maximum and Mid-Holocene) was modeled to identify their common geographic area of distribution. The species showed very well differentiated niches and a distribution of their habitats virtually segregated by continents since the Mid-Holocene (P. nigra in Europe and C. atlantica in Africa), which responds to differences in climatic affinities. However, the contact of the bordering areas of their distributions in the Baetic mountain range suggests that C. atlantica could have maintained its presence in the Iberian Peninsula until recent times. P. nigra would have displace it in later stages due to its greater prevalence on the continent, so it would have had greater opportunities to occupy the available space.

Proposal for the Global Boundary Stratotype Section and Point (GSSP) for the Priabonian Stage (Eocene) at the Alano section (Italy)

Claudia Agnini, Jan Backman, Flavia Boscolo-Galazzo, Daniel J. Condon, Eliana Fornaciari, Simone Galeotti, Luca Giusberti, Paolo Grandesso, Luca Lanci, Valeria Luciani, Simonetta Monechi, Giovanni Muttoni, Heiko Pälike, Maria Letizia Pampaloni, Cesare A. Papazzoni, Paul N. Pearson, Johannes Pignatti, Isabella Premoli Silva, Isabella Raffi, Domenico Rio, Lorenzo Rook, Diana Sahy, David J.A. Spofforth, Cristina Stefani, Bridget S. Wade. Episodes 2021;44:151-73. https://doi.org/10.18814/epiiugs/2020/020074

Behavioral momentum and resistance to extinction across repeated extinction tests.

The present experiments assessed whether resistance to extinction of pigeons' key pecking decreased across repeated extinction tests. An additional impetus for this research was to determine how the quantitative framework provided by behavioral momentum theory might be used to describe any such changes across tests. Pigeons pecked keys in two-component multiple schedules (one component associated with a higher reinforcer rate and the other with a lower rate) in which baseline and extinction conditions alternated. In Experiment 1, baseline and extinction conditions alternated every session, and, in Experiment 2, these conditions lasted for 10 and 7 sessions, respectively. Resistance to extinction decreased across successive extinction conditions in both experiments. Fits of the behavioral-momentum based model of extinction to the data returned uncertain results in Experiment 1 but implicated both generalization decrement and response-reinforcer contingency termination as the possible mechanisms responsible for behavior change in Experiment 2. Thus, these data suggest that experimental manipulations that affect discrimination of changes in reinforcement contingencies may influence resistance to extinction by modulating the disruptive impacts of removing reinforcers from the experimental context and of suspending response-reinforcer contingencies.

The last 1 million years of the extinct genus Discoaster: Plio–Pleistocene environment and productivity at Site U1476 (Mozambique Channel)

A detailed paleoenvironment reconstruction from the Mozambique Channel, western Indian Ocean, based on the calcareous nannoplankton assemblages was conducted for the interval between 2.85 and 1.85 Myr. This study covers the period during which the successive extinction of the last five species of discoasters occurred. New productivity data obtained from the abundances of the Discoaster species (Discoaster brouweri, D. triradiatus, D. pentaradiatus, D. surculus, and D. tamalis) and other indicative calcareous nannoplankton taxa showed abundance variations, which were at paced with the 100, 41, and 23 kyr astronomical periodicities. A shift in the productivity and water-column stratification proxies occurred at ~2.4 Ma, after the onset of the Northern Hemisphere glaciation. Here we propose that the variability recorded at International Ocean Discovery Program Site U1476 reflects the interplay between forcing associated with warm tropical Pacific and cold southern ocean influences. The former is shown by consistent occurrence of warm water taxa (Calcidiscus leptoporus, Oolithotus spp., Rhabdosphaera clavigera, Syracosphaera spp., Umbellosphaera spp.), typical of Indonesian Throughflow surface waters. On the other hand, the occurrence of Coccolithus pelagicus indicates the influence of cold, nutrient-rich sub-Antarctic surface waters. A more mixed water column initiated at ~2.4 Ma, and a consequent productivity increase led to the gradual reduction of the Discoaster species, until their extinction at 1.91 Ma. This period was characterized by the low values of the Florisphaera profunda index and high abundances of upper photic zone flora, indicative of nutrient-rich surface water conditions. High productivity at the location during this period could have also been amplified by localized upwelling events driven by the Mozambique Channel eddies.

Respuestas de observación y resistencia a la extinción

The resistance to extinction of observing behavior was determined by removing the primary reinforcer and presenting only a stimulus associated with reinforcement (S+), only a stimulus associated with extinction (S-), and only a neutral stimulus. In three training conditions of 30 sessions each, lever pressing by rats was reinforced on a mixed random ratio 50 extinction. Each press on a second lever (observing) produced for 5 s an S+ during the reinforcement component and an S- during extinction. After each training condition, rats were exposed to 10 sessions of extinction in which the mixed schedule was discontinued. In each of the three successive extinction conditions, each press on the observing lever produced only the S+, only the S-, or only the neutral stimulus. The order of exposure was different for each rat. Presenting the S+ increased and presenting the S- decreased resistance to extinction relative to the neutral stimulus. These findings suggest that the concept of conditioned reinforcement is still a necessary one in behavior analysis.

Jurassic–Cretaceous boundary ammonite Blanfordiceras (Mollusca: Cephalopoda) from Fortissimo-1 Wildcat Well, Browse Basin, Northwest Shelf, Australia

Jurassic–Cretaceous ammonites are particularly robust fossil tools in global stratigraphy and correlation. The successive evolution and extinction of these cephalopod mollusks was so rapid that many ammonite zones are no more than one million years in duration. A well-preserved ammonite specimen from the Fortissimo-1 core, Browse Basin, NW Australia is assignable to the widespread latest Jurassic dimorphic berriaselline genus, Blanfordiceras Cossmann, recorded previously from the Spiti area, Nepal, Tibet, Madagascar, Papua-New Guinea, Antarctica, and southern South America. This is the first report of ammonites of this age in the Australian region. The evolute shell of an estimated 90-100 mm diameter (when extrapolated) and pronounced ornamentation of variably bifurcating, curvilinear and flexuous ribs, intercalated with simple, non-bifurcating ribs, is consistent with Blanfordiceras wallichi (Gray, 1832), which has traditionally been restricted to the uppermost Tithonian Stage, ca. 146.5-145.5 Ma, but may well have survived into the earliest part of the Berriasian. The first recorded occurrence of this ammonite in Australia fills an anomalous absence in the paleobiogeographic distribution of Jurassic–Cretaceous boundary ammonites in the Indo-SW Pacific Subrealm with important implications for the calibration of offshore rocks and wells in Australia.

Calcareous nannofossil biostratigraphy and paleoecology of the Cenomanian – Turonian transition in the Tarfaya Basin, southern Morocco

An abundant and diverse nannoflora occurs across the Cenomanian/Turonian (C/T) boundary at Tazra in the Tarfaya Basin of southern Morocco. The nannoflora of this sequence permits recognition of three biozones (CC10-CC12), three subzones (CC10a, CC10b and CC10c), and thirteen important nannolith bioevents previously reported from this interval elsewhere. The floral record shows erratic species abundance fluctuations that clearly vary with lithology and reflect at least in part preservational bias and diagenetic processes. In general, four dissolution resistant taxa are dominant: Watznaueria barnesae, Eiffellithus turriseiffelii, Eprolithus floralis, and Zeugrhabdotus spp. The late Cenomanian Zone CC10 marks a rapid excursion in ∂ 13C and is characterized by the successive extinction of four taxa, which are widely recognized as reliable biomarkers: Corollithion kennedyi, Axopodorhabdus albianus, Lithraphidites acutus, and Helenea chiastia. This interval is also marked by high species richness and high abundance of the tropical species Watznaueria barnesae, suggesting warm tropical waters. The subsequent ∂ 13C plateau and organic carbon-rich black shale deposition of the oceanic anoxic event (OAE2) is characterized by low species richness, but high nannofossil abundance, and peak abundance of the cool water and high productivity indicator Zeugrhabdotus spp., followed by the first peak abundance of cool water Eprolithus floralis. This interval correlates with the planktic foraminiferal diversity minimum and the Heterohelix shift, which marks the expansion of the oxygen minimum zone (OMZ). The C/T boundary is identified based on the FO of Quadrum gartneri, which is <1 m below the FO of the planktic foraminifer C/T marker Helvetoglobotruncana helvetica. In the early and middle Turonian, the two dominant species, tropical W. barnesae and cool water E. floralis, alternate in abundance and suggest fluctuating climatic conditions.

D-Cycloserine Facilitates Extinction of Conditioned Alcohol-Seeking Behaviour in Rats

The aim of the present study was to examine the influence of partial NMDA receptor agonist d-cycloserine (DCS) on the extinction of conditioned alcohol-seeking behaviour. For this purpose, rats were administered with DCS 60 min before each successive extinction session. Resumption of alcohol responding was carried out 1 day after the final extinction session. We demonstrate that treatment of rats with 5 mg/kg of DCS was capable in facilitating extinction of conditioned alcohol-seeking behaviour, which subsequently reduced the resumption of extinguished operant responding. Our study suggests a good rationale for the development of new add-on medications for exposure-based psychotherapy so as to extinguish drug-conditioned appetitive memories in alcohol-dependent patients.

X-ray spherical wave scattering patterns of the epitaxial Si/GeSi/Si (001) heterosystem

The interference effects of x-ray diffraction topography in the Si/GeSi/Si (001) heterosystem have been investigated. This heterosystem is a film interferometer in which the GeSi solid solution layer of variable thickness serves as a separating gap. A topograph obtained for a 004 reflection (CuK α radiation) using a spherically bent monochromator demonstrates both maxima of the pendulum solution observed for the case of a thin crystal (1) and interference fringes due to the variable thickness of the separation layer (2). The correlation of effects (1) and (2) with the successive extinction effect of interference maxima on the slope of the diffraction reflection curve is shown by the calculated topographs obtained for the different ranges of the angle of radiation incidence θ (200 and 1400″). The possibility of precisely determining the thickness of the crystal separation layer of an interferometer based on the indicated effect is demonstrated.

Dynamics of odour learning in Leptopilina boulardi, a hymenopterous parasitoid

We investigated the dynamics of odour learning involved in host location by a parasitoid insect,Leptopilina boulardi (Hymenoptera: Figitidae). Females of this species find their Drosophila host larvae by probing fruits with their ovipositor. They can be conditioned to respond to an odour when the odour exposure is associated with oviposition. We investigated the effect of the number of conditioning trials, sensitization tests and extinction tests on the retention of the conditioned response. Results showed that: (1) a single odour–oviposition association produced a strong short-term memory (1–2h), which rapidly decayed over 24 h; (2) multiple odour–oviposition associations produced a memory trace that was strong in both the short term and the longer term (24h); (3) sensitization to the odour through mere oviposition experience (without odour) was low after a single trial and high after multiple trials, but was only observed for a short period; (4) all memory traces were erased by three successive extinction tests, regardless of the intertest interval. We conclude that the probing behaviour of a Drosophila parasitoid is characterized by great plasticity shaped in the short term by sensitization, and in the longer term by associative learning. We compare olfactory plasticity in this parasitoid foraging for hosts and that of the honeybee foraging for food, suggesting common underlying processes in the central nervous system. Finally our results may relate to the dynamics of the foraging activity of L.boulardi. Copyright 2003 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

The Persistence of Abnormal Sex Ratios in the African Butterfly, Acraea Encedon

1. The African butterfly, Acraea encedon, contains a directly inherited, all-female strain. Elementary population genetics predicts that this strain should lead to the eventual extinction of the species, but in fact the strain appears to have reached equilibrium. 2. Several hypotheses have been put forward to explain the maintenance of the sex ratio polymorphism in this species, but so far none has appeared convincing. 3. Two previously suggested hypotheses, one involving a selective advantage for the normal females by virtue of their time of emergence and the other involving successive extinction and recolonization of discrete populations, are combined. It is shown by means of a simulation that these two hypotheses together lead to a greater degree of stability than either separately.

Cues to Decreasing Resistance to Extinction in Successive Acquisitions and Extinctions

Four groups of rats were used in a successive acquisition and extinction situation to determine which conditions, if any, produce a decrease in resistance to extinction across successive acquisitions and extinctions. Two groups experienced long N-R transitions (time from extinction to the subsequent acquisition) with all remaining transitions being short. The short transitions were: R-R (time between acquisition trials), R-N (time from the end of an acquisition until the subsequent extinction), and N-N (time between extinction trials). Two groups experienced long R-N and short N-R, N-N, and R-R transitions. Rats in one long N-R transition and one long R-N transition group had acquisitions and extinctions delineated by distinctive cues (blinking lights during acquisition or extinction trials). The other two groups had no such cues. The disparity in N-N versus N-R transition times combined with additional visual cues during extinction produced decreasing resistance to extinction across successive extinctions.

Successive Acquisitions and Extinctions with Goldfish (Carassius Auratus) in a Swimway Situation

Goldfish were trained in a successive acquisition and extinction shuttle-swimway situation. Groups of 12 fish experienced alternating days of acquisition and extinction, extinction following immediately after each daily acquisition session, and acquisition following immediately after each daily extinction session. None of the groups produced decreasing resistance to extinction across extinctions within eight successive acquisitions and extinctions. A group of fish given 16 successive acquisitions and extinctions with alternating days of acquisition and extinction learned to decrease swimming speeds after eight successive extinctions. However, these fish also decreased acquisition speeds across the last 8 successive acquisitions.

Repeated Acquisition and Extinction of Barpressing in Rats and Guinea Pigs

On each of 10 days rats and guinea pigs first barpressed for 15 reinforcements on a CRF schedule and then were immediately extinguished during an unsignalled 10-min. extinction session. Analysis of the number of bar-presses during each of 10 extinction sessions indicated a significant reduction for rats but not for guinea pigs because the level of barpressing remained consistently high immediately following reinforcement for the guinea pigs but declined progressively faster within successive extinction sessions for rats. Results support the idea that organisms with well developed sensory-motor capacities at birth are less able to inhibit previously rewarded responses than those with slower development.

Determinants of rate of extinction in successive acquisitions and extinctions

Rats were used in an investigation of the conditions that are necessary to obtain a decrease in resistance to extinction across extinctions in a successive acquisition and extinction paradigm. Long breaks (23.5 h) after extinction coupled with a short intertrial interval within extinction sessions (long N-R transition) resulted in a decrease in resistance to extinction across the successive extinctions. Long breaks after acquisition sessions (long R-N transition), or in the middle of acquisition sessions (long R-R transition), yielded an increase in resistance to extinction across the successive extinction sessions. When extinction sessions followed immediately after acquisition sessions (N-R), Ss decreased their running speeds within each of the successive extinctions. When acquisition sessions followed immediately after extinction sessions (R-N), Ss decreased their running speeds within the first few successive extinctions. The R-N Ss learned to increase their running speed within extinctions during the later successive extinctions.

Sequential contrast effects with human subjects.

Institutionalized retardates were exposed to a multiple variable-interval: extinction schedule of reinforcement in which 5-min periods of variable-interval reinforcement and 5-min periods of extinction were presented in a random order. This schedule was found to generate sequential contrast effects: response rates during variable-interval reinforcement were higher when a variable-interval period followed an extinction period than when it followed another variable-interval period. The rate of responding within a variable-interval period also was affected by the number of extinction periods preceding a variable-interval period. As the number of successive extinction periods that preceded a variable-interval period increased, the rate of responding during that variable-interval period increased. The sequential contrast effects were transient, being most evident during the early sessions and generally disappearing by the tenth session.

Effect of a Successive Conditioning-Extinction Procedure on Light Contingent Bar-Pressing

The experiment tests conflicting implications of the conditioning and the facilitation hypothesis of the increase in bar pressing observed under light-onset contingency conditions. Female hooded rats were first given 5 operant test sessions. These were followed by 10 sessions under a successive conditioning-extinction procedure; thereafter, after each light-onset session two successive extinction sessions were given (12 sessions); Ss were then trained under a fixed ratio procedure (6 sessions) and finally were placed under a successive fixed ratio conditioning-extinction procedure. The prediction from a conditioning hypothesis that extinction rates would be consistently higher than during the operant test sessions was confirmed.

The Real Meaning of the New Conception of Time

THE fascinating presidential address of Dr. Jeans to the Royal Astronomical Society, published in NATURE for February 27, with its poetical allusions to children chasing a rainbow over the hills, and to what seems the successive extinction of the shires as one gazes at the country from the windows of an express, must have helped many of us to make fast our hold upon the principles of the general theory of relativity. Yet it is doubtful whether the full implications for the doctrine are generally realised—of such a statement, for example, as “The year 1927 has the same sort of existence as the county of Cornwall.” The legitimate inference surely amounts to nothing less momentous than this: that everything that has ever existed or happened, or that ever will exist or happen, in the universe, is immanent in physical space-time or ‘ether’; and that what to us participators in the drama being enacted on the space-time stage appears to be the special differentiation of the present—of now—from the past and the future, is merely an illusion due to our experiencing changes in a certain dimension of the four-dimensional continuum, which imparts the impression of travelling along that dimension and hence the idea of flowing time.