Periods Of Stasis Research Articles

Real-time monitoring of the growth of the nasal septal cartilage and the nasofrontal suture

The nasal septum is thought to be a primary growth cartilage for the midface and, as such, has been implicated in syndromes involving midfacial hypoplasia. However, this internal structure is difficult to study directly. The aims of this study were to provide direct, continuous measurements of the growth of the nasal septal cartilage and to compare these with similar measurements of the nasofrontal suture to test whether the growth of the cartilage precedes the growth of the suture and whether the growth of the septal cartilage is constant or episodic. Ten Hanford minipigs were used. Linear displacement transducers were implanted surgically in the septal cartilage and across the nasofrontal suture. Length measurements of the cartilage and suture were recorded telemetrically each minute for several days. The growth rate of the nasal septal cartilage (0.07% ± 0.03% length/h) was significantly higher than that of the suture (0.03% ± 0.02% length/h) (P = 0.004). The growth of both structures was episodic with alternating periods of growth (5-6 per day) and periods of stasis or shrinkage. No diurnal variation in growth of the cartilage was detected. These results are consistent with the notion that growth of the septal cartilage might drive growth of the nasofrontal suture. Growth of the midface is episodic rather than constant.

The most mysterious beetles: Jurassic Jurodidae (Insecta: Coleoptera) from China

Jurodidae are thought to be some of the world's most mysterious beetles and display an intriguing mixture of characters occurring in three different suborders. Hitherto, all known fossil and extant Jurodidae were extremely rare and restricted to Russian Siberia and the Far East. Here we describe two new species, Jurodes daohugouensis sp. nov. and Jurodes pygmaeus sp. nov. from the Middle Jurassic of Daohugou, China. A key to all species of Jurodidae and their research history are given, and the detailed morphology of fossil Jurodidae is also presented. Our results confirm the presence of three ocelli in fossil Jurodidae, and reveal that hind wings of J. pygmaeus sp. nov. possess well developed radial and oblong cells, and are very similar to those of extant Jurodidae (Sikhotealinia zhiltzovae). Male genitalia of fossil Jurodidae were described herein for the first time, showing a basal trilobate structure. The presence of exposed propleuron, three pairs of external trochantins, metanepisterna with ridges, primitive characters of wing venation further support the probable placement of Jurodidae in the suborder Archostemata. J. daohugouensis and J. pygmaeus are very similar to S. zhiltzovae in having the big protruding eyes, elevated median portion of frons bearing three ocelli, pubescent body, contiguous procoxae, exposed trachantion of all coxae, elytra with rows of punctures, and wing venation. Our results show that these key characters of extant Jurodidae can be traced back to the Middle Jurassic, revealing that the family has been in a period of evolutionary stasis for at least 160million years. Furthermore, our discoveries widen the paleogeographic distribution of fossil Jurodidae from Russian Siberia to northern China.

Cranial anatomy and variation inProsaurolophus maximus(Dinosauria: Hadrosauridae)

Prosaurolophus maximus Brown is a saurolophine hadrosaurid known from numerous complete, articulated skulls from the Dinosaur Park Formation (Campanian, Alberta, Canada) that range in size by approximately half a metre in total skull length. Therefore, it is an important taxon for understanding patterns of growth and variation in saurolophines. This study describes the cranial anatomy of P. maximus from the type locality of Dinosaur Provincial Park (Dinosaur Park Formation: Campanian) on the basis of ten articulated skulls, quantitatively examines its range of osteological variation, and provides the first hypothesized ontogenetic series for this taxon. A second species,Prosaurolophus blackfeetensis Horner, was named on the basis of geologically younger material from Montana (Two Medicine Formation: Campanian) that is diagnosed by putative morphological differences in the nasal crest. However, considerable nasal crest variation in the sample from the Dinosaur Park Formation does not permit quantitative differentiation of P. blackfeetensis from P. maximus. Furthermore, a species-level phylogenetic analysis of saurolophines that includes both P. maximus and P. blackfeetensis as originally defined recovers them as sister taxa that do not differ morphologically in the character matrix. Based on both the morphometric and phylogenetic data, this study supports the hypothesis that P. blackfeetensis is a junior synonym of P. maximus, thereby substantially increasing its temporal range to 1.6 million years, and a concomitant period of morphological stasis in this taxon.

Politics and ‘shock’: reactionary anti-doping policy objectives in Canadian and international sport

This article addresses dramatic changes in anti-doping that have occurred since the 1960s internationally and since the early 1980s in Canada. We demonstrate first that in the Olympic movement, the use of performance-enhancing substances became a problem primarily because of the ‘sportive nationalism’ that pervaded the cold war. Second, a form of ‘politics of appearance’ played an important role in the creation of anti-doping policies; we show that the International Olympic Committee (IOC) created anti-doping policies largely as a reactionary measure to political concerns and to certain ‘shocks’ or ‘focusing events’ that brought the issue to the fore. Third, and most importantly, major Canadian initiatives, beginning with policy created following the 1983 Pan American Games, have been a reflection of the same ‘politics and shock’ measures that took place at the international level. This point relates to our final objective: to demonstrate that in Canada anti-doping policies evolved from being non-existent to being some of the most stringent in the world in just over two decades. We consider these major international and Canadian events through the lens of punctuated equilibrium theory, which explains both extended periods of stasis and dramatic changes in policy systems.

From mush to eruption in centuries: assembly of the super-sized Oruanui magma body

The magmatic systems that give rise to voluminous crystal-poor rhyolite magma bodies can be considered to operate on two contrasting timescales: Those governed by longer-term processes by which a magma acquires its chemical and isotopic characteristics (e.g., fractional crystallisation and assimilation), and those operating at shorter timescales during the physical accumulation of the melt-dominant magma body that finally erupts. We explore the compositional and textural relationships between amphibole and orthopyroxene crystals from the 25.4 ka, 530 km3 (magma) Oruanui eruption products (Taupo volcano, New Zealand) to investigate how processes related to the physical assembly of the pre-eruptive magma body are represented in the crystal record. Over 90 % of orthopyroxenes from the volumetrically dominant high-SiO2 (>74 wt%) rhyolite pumices record textural evidence for a significant disequilibrium event (partial dissolution ± resorption of cores and interiors) prior to the growth of 40–500 μm thick rim zones. This dissolution/regrowth history of orthopyroxene is recorded in the chemistry of co-crystallising amphiboles as a prominent inflection in the concentrations of Mn and Zn, two elements notably enriched in orthopyroxene relative to amphibole. Textural and chemical features, linked with in situ thermobarometric estimates, indicate that a major decompression event preceded the formation of the melt-dominant body. The decompression event is inferred to represent the extraction of large volumes of melt plus crystals from the Oruanui crystal mush/source zone at pressures of 140–300 MPa (~6–12 km depth). Orthopyroxene underwent partial dissolution during ascent before reestablishing in the melt-dominant magma body at pressures of 90–140 MPa (~3.5–6 km). We model Fe–Mg diffusion across the core-rim boundaries along the crystallographic a or b-axes to constrain the timing of this decompression event, which marked establishment of the melt-dominant magma body. Maximum modelled ages indicate that this event did not begin until ~1,600 years before eruption, consistent with constraints from zircon model-age spectra. Once extraction began, it underwent runaway acceleration with a peak extraction age of ~230 years, followed by an apparent period of stasis of ~60 years prior to eruption. The rapidity of the extraction and accumulation processes implies the involvement of a dynamic driving force which, in the rifted continental arc setting of the Taupo Volcanic Zone, seems likely to be represented by magma-assisted extensional tectonic processes.

The Rate of Molecular Adaptation in a Changing Environment

It is currently unclear whether the amino acid substitutions that occur during protein evolution are primarily driven by adaptation, or reflect the random accumulation of neutral changes. When estimated from genomic data, the proportion of adaptive amino acid substitutions, called α, was found to vary greatly across species, from nearly zero in humans to above 0.5 in Drosophila. These variations have been interpreted as reflecting differences in effective population size, adaptation being supposedly more efficient in large populations. Here, we investigate the influence of effective population size and other biological parameters on the rate of adaptive evolution by simulating the evolution of a coding sequence under Fisher's geometric formalism. We explicitly model recurrent environmental changes and the subsequent adaptive walks, followed by periods of stasis during which purifying selection dominates. We show that, under a variety of conditions, the effective population size has only a moderate influence on α, and an even weaker influence on the per generation rate of selective sweeps, modifying the prevalent view in current literature. The rate of environmental change and, interestingly, the dimensionality of the phenotypic space (organismal complexity) affect the adaptive rate more deeply than does the effective population size. We discuss the reasons why verbal arguments have been misleading on that subject and revisit the empirical evidence. Our results question the relevance of the "α" parameter as an indicator of the efficiency of molecular adaptation.

Phenotypic evolution in a fossil gastropod species lineage: Evidence for adaptive radiation?

Detecting speciation in the fossil record is a particularly challenging matter. Palaeontologists are usually confronted with poor preservation and limited knowledge on the palaeoenvironment. Even in the contrary case of adequate preservation and information, the linkage of pattern to process is often obscured by insufficient temporal resolution. Consequently, reliable documentations of speciation in fossils with discussions on underlying mechanisms are rare. Here we present a well-resolved pattern of morphological evolution in a fossil species lineage of the gastropod Melanopsis in the long-lived Lake Pannon. These developments are related to environmental changes, documented by isotope and stratigraphical data. After a long period of stasis, the ancestral species experiences a phenotypic change expressed as shift and expansion of the morphospace. The appearance of several new phenotypes along with changes in the environment is interpreted as adaptive radiation. Lake-level high stands affect distribution and availability of habitats and, as a result of varied functional demands on shell geometry, the distribution of phenotypes. The ongoing divergence of the morphospace into two branches argues for increasing reproductive isolation, consistent with the model of ecological speciation. In the latest phase, however, progressively unstable conditions restrict availability of niches, allowing survival of one branch only.

Beyond black shales: The sedimentary and stable isotope records of oceanic anoxic events in a dominantly oxic basin (Silurian; Appalachian Basin, USA)

Episodes of instability in the global climato-oceanic system have become the hallmark of the Silurian Period. These events are marked by six large positive carbon isotope excursions associated with major extinctions. The widespread environmental consequences of these perturbations of the global carbon cycle remain poorly documented. A high-resolution chronostratigraphic reconstruction of the Appalachian foreland basin (AFB) provides a framework to evaluate environmental signatures of two of these carbon isotope excursions (Valgu and Ireviken events; Telychian–Sheinwoodian) at a regional scale. Integration of published biostratigraphic range data, mapping of sequence stratigraphic surfaces and facies, and generation of high-resolution carbon isotope profiles for several transects provides precise correlation of the basin stratigraphy yielding a high-resolution temporal framework. This chronostratigraphic reconstruction of the AFB highlights the importance of time-specific facies (TSF) during these intervals. For instance, packages of red, green, and gray marine rocks separately occupied discrete time intervals—cutting across “local” facies belts indicative of shallow to deep marine environments. Similarly, widespread iron mineralization occurred during discreet time slices as “bathtub rings” rimming the margins of the basin. Changes from one time-specific facies to the next are coincident with changes in carbon isotope values, indicating a genetic link between fractionation of the global carbon reservoir and redox changes from generally oxic to anoxic oceanic conditions in parts of the AFB.The basal part of the study interval was deposited during the Valgu Event. This first event begins with an unconformity marking global lowstand. This fall in sea level was coincident with rising carbon isotope values as recorded in adjacent basins. A slight sea level rise and flooding of the subaerial unconformity occurred near the peak in carbon isotope values. Oxidized iron minerals were deposited in a zone that extended from the lower shoreface into the basin center—pinching out into shallower parts of the basin. Thin pyrite–phosphorite–glauconite layers, associated with black shales in the basin center, were deposited over these ferruginous strata. As the event ended and carbon isotope values shifted negatively to a more stable baseline, temperatures warmed, sea level reached a Silurian high, and oxic conditions associated with very low rates of organic carbon (OC) burial were established. These conditions were relatively stable for nearly four million years. This long period of stasis was punctuated by the Ireviken Event, which displays a strikingly similar progression of TSF patterns, yet more intense and longer lived than the preceding Valgu Event.With the first positive shift in carbon isotopes at the onset of the Ireviken Event, the basin redox system changed from largely oxidizing to reducing, coincident with a rapid drop in sea level and an abrupt reappearance of iron mineralization on the basin margins. The sea level fall associated with the shift to peak values of the carbon isotope excursion is marked by the progradation of a significant body of sand well out into the basin. During this sea level drop, conditions in the basin center became highly reducing and periodically sulfidic. Widespread ironstones and ankeritic carbonates were deposited isochronously, rimming the shallow basin margins where they alternated with light gray pyritic shales, indicating fluctuating redox conditions. A large negative carbon isotope excursion of ~3‰ is coincident with a shift from regression to transgression, suggesting glacial melting via methane release. Continued deposition of ironstones through this time interval suggests a primary link to shallow marine redox processes rather than large-scale transgression or regression of the shoreline. The ironstones are overlain by gray to black pyritic shales deposited across all environments, revealing a final stage of redox progression into sustained sulfidic conditions as peak values of the carbon isotope excursion returned to a high stable baseline near +4‰.The similar expression of TSFs within the AFB of these two global events demonstrates that fractionation of the global atmospheric and oceanic carbon reservoirs had a predictable, cascading impact on shallow sea floor environments. The associated redox processes reveal the dynamic regional interactions of a shallow oxic epicontinental water mass with a broader anoxic oceanic water mass, providing valuable insight into the origin of some of the largest extinctions in the Silurian Period.

Degeneracy allows for both apparent homogeneity and diversification in populations

Trait diversity – the substrate for natural selection – is necessary for adaptation through selection, particularly in populations faced with environmental changes that diminish population fitness. In habitats that remain unchanged for many generations, stabilizing selection maximizes exploitation of resources by reducing trait diversity to a narrow optimal range. One might expect that such ostensibly homogeneous populations would have a reduced potential for heritable adaptive responses when faced with fitness-reducing environmental changes. However, field studies have documented populations that, even after long periods of evolutionary stasis, can still rapidly evolve in response to changed environmental conditions. We argue that degeneracy, the ability of diverse population elements to function similarly, can satisfy both the current need to maximize fitness and the future need for diversity. Degenerate ensembles appear functionally redundant in certain environmental contexts and functionally diverse in others. We propose that genetic variation not contributing to the observed range of phenotypes in a current population, also known as cryptic genetic variation (CGV), is a specific case of degeneracy. We argue that CGV, which gradually accumulates in static populations in stable environments, reveals hidden trait differences when environments change. By allowing CGV accumulation, static populations prepare themselves for future rapid adaptations to environmental novelty. A greater appreciation of degeneracy's role in resolving the inherent tension between current stabilizing selection and future directional selection has implications in conservation biology and may be applied in social and technological systems to maximize current performance while strengthening the potential for future changes.

Clinical utility of EEG in attention-deficit/hyperactivity disorder: a research update.

Psychiatric research applications of electroencephalography (EEG), the earliest approach to imaging human cortical brain activity, are attracting increasing scientific and clinical interest. For more than 40years, EEG research has attempted to characterize and quantify the neurophysiology of attention-deficit/hyperactivity disorder (ADHD), most consistently associating it with increased frontocentral theta band activity and increased theta to beta (θ/β) power ratio during rest compared to non-ADHD controls. Recent reports suggest that while these EEG measures demonstrate strong discriminant validity for ADHD, significant EEG heterogeneity also exists across ADHD-diagnosed individuals. In particular, additional studies validating the use of the θ/β power ratio measure appear to be needed before it can be used for clinical diagnosis. In recent years, the number and the scientific quality of research reports on EEG-based neurofeedback (NF) for ADHD have grown considerably, although the studies reviewed here do not yet support NF training as a first-line, stand-alone treatment modality. In particular, more research is needed comparing NF to placebo control and other effective treatments for ADHD. Currently, after a long period of relative stasis, the neurophysiological specificity of measures used in EEG research is rapidly increasing. It is likely, therefore, that new EEG studies of ADHD using higher density recordings and new measures drawn from viewing EEG as a 3-dimensional functional imaging modality, as well as intensive re-analyses of existing EEG study data, can better characterize the neurophysiological differences between and within ADHD and non-ADHD subjects, and lead to more precise diagnostic measures and effective NF approaches.

Analysis of weaning‐induced stress in Saanen goat kids

In young ruminants' life, weaning often coincides with a period of growth stasis and poor welfare. The present study aimed at evaluating the effect of coping with the new diet on behavioural and haematological stress indicators in goat kids subjected to a commonly adopted weaning practice. Immediately after birth, male Saanen goat kids were divided into two groups: MILK and WMIX. All were fed colostrum for the first 3 days and then goat milk to the age of 29 days. After that, MILK kids continued to receive milk, while the WMIX kids underwent weaning and were completely weaned by day 48. Animal behaviour was recorded daily. From day 23-50, blood samples were taken weekly and analysed for indicators of stress and immune function. No abnormal behaviour, such as injurious behaviours or stereotypies, was observed in either of the experimental groups throughout the experimental period. During the last week, fasting plasma cortisol level was significantly lower, whereas plasma activity of both alanine aminotransferase (ALT) and aspartate aminotransferase (AST) was significantly higher in WMIX kids, in relation to the MILK ones. Anyway, data were within the normal physiological range and no difference was observed neither in plasma haptoglobin, ceruloplasmin, albumin and antithrombin III, nor in plasma immunoglobulin A and G, at any time, signalling no stressful condition. Therefore, differences observed in cortisol, ALT and AST could be the consequence of the metabolic changes that occur during the transition from pre-ruminant to ruminant state. The gradual weaning at 48 days of age did not result in any stressful condition and had no negative effect on weight gain. Results suggest that parameters commonly adopted to provide information on animal stress, such as cortisol and aminotransferase activity, can vary in relation to the physiological status of the animals and may bias stress assessment.

Using palaeontological data to assess mammalian community structure: Potential aid in conservation planning

Taxon-free metrics of biodiversity health are crucial for present and future conservation efforts in the face of current global change. We investigated the distribution of species in combined diet and body size functional groups over the past 16Ma in the Northern Great Plains to establish a pre-Holocene (before 11,000ya, when humans arrived in North America) and pre-industrial baseline (11,000–500ya) of this measure of community structure. Functional group distributions were compared on two scales to gauge the impact of time-averaging on patterns of community structure change: 1) North American Land Mammal Ages (NALMAs), and 2) individual diverse localities. Distributions were statistically compared using pairwise Fisher's exact tests with Monte Carlo P-value simulations and Holm P-value adjustment, and qualitatively assessed using correspondence analysis. When averaged over entire NALMAs, major changes in functional group distribution only take place in the Hemphillian, and at the start of the Holocene. Locality-level patterns also indicate long periods of stasis in the metric (Barstovian–Clarendonian and Hemphillian–Holocene). A threshold of global climate change is one possible explanation for the change that began in the Hemphillian, but further study is needed in that regard. Extinction of megaherbivores (>44kg) is the primary driver of apparent differences between the Holocene and previous time periods. Although the extent of time-averaging and other taphonomic biases affect the details of observable patterns per time period, overall, proportional diversity of functional groups is a promising metric for assessing mammalian community health because it is remarkably stable through time and changes only with major external perturbations to ecosystems.

Limited, episodic diversification and contrasting phylogeography in a New Zealand cicada radiation.

BackgroundThe New Zealand (NZ) cicada fauna contains two co-distributed lineages that independently colonized the isolated continental fragment in the Miocene. One extensively studied lineage includes 90% of the extant species (Kikihia + Maoricicada + Rhodopsalta; ca 51 spp.), while the other contains just four extant species (Amphipsalta – 3 spp. + Notopsalta – 1 sp.) and has been little studied. We examined mitochondrial and nuclear-gene phylogenies and phylogeography, Bayesian relaxed-clock divergence timing (incorporating literature-based uncertainty of molecular clock estimates) and ecological niche models of the species from the smaller radiation.ResultsMitochondrial and nuclear-gene trees supported the monophyly of Amphipsalta. Most interspecific diversification within Amphipsalta-Notopsalta occurred from the mid-Miocene to the Pliocene. However, interspecific divergence time estimates had large confidence intervals and were highly dependent on the assumed tree prior, and comparisons of uncorrected and patristic distances suggested difficulty in estimation of branch lengths. In contrast, intraspecific divergence times varied little across analyses, and all appear to have occurred during the Pleistocene. Two large-bodied forest taxa (A. cingulata, A. zelandica) showed minimal phylogeographic structure, with intraspecific diversification dating to ca. 0.16 and 0.37 Ma, respectively. Mid-Pleistocene-age phylogeographic structure was found within two smaller-bodied species (A. strepitans – 1.16 Ma, N. sericea – 1.36 Ma] inhabiting dry open habitats. Branches separating independently evolving species were long compared to intraspecific branches. Ecological niche models hindcast to the Last Glacial Maximum (LGM) matched expectations from the genetic datasets for A. zelandica and A. strepitans, suggesting that the range of A. zelandica was greatly reduced while A. strepitans refugia were more extensive. However, no LGM habitat could be reconstructed for A. cingulata and N. sericea, suggesting survival in microhabitats not detectable with our downscaled climate data.ConclusionsUnlike the large and continuous diversification exhibited by the Kikihia-Maoricicada-Rhodopsalta clade, the contemporaneous Amphipsalta-Notopsalta lineage contains four comparatively old (early branching) species that show only recent diversification. This indicates either a long period of stasis with no speciation, or one or more bouts of extinction that have pruned the radiation. Within Amphipsalta-Notopsalta, greater population structure is found in dry-open-habitat species versus forest specialists. We attribute this difference to the fact that NZ lowland forests were repeatedly reduced in extent during glacial periods, while steep, open habitats likely became more available during late Pleistocene uplift.

Turkey's Path to EU Membership: An Historical Institutionalist Perspective

Scholars have drawn heavily on new institutionalist approaches in the study of comparative European politics and European integration. However, these approaches have been neglected in the study of Turkey–EU relations, resulting in a significant gap in the academic literature. In particular, the extant literature fails to question the significance of domestic political institutional settings and also fails to ask what role Turkey's National Security Council (MGK) played in shaping Turkey's path towards EU membership. The Historical Institutionalist approach, and the associated concepts of path dependence and punctuated equilibrium, can help address these failures by highlighting the importance of two significant phases of Turkey's European policy: the MGK's tendency to rule through states of emergency and its incompatibility with EU membership criteria (1983–1997); and the curtailment of the MGK's powers and the EU's decision to begin accession negotiations (1997–2004). To substantiate the value of historical institutionalism, I will first discuss the utility of the approach and justify its selection as a framework for explaining Turkey–EU relations. I will then discuss, in general terms, the ways in which institutions shape political action and maintain long periods of stasis. I will then demonstrate the utility of the concept of path dependence in researching the interaction between the MGK's use of state of emergency legislation and Turkey's path towards EU membership. The final part argues that the changes in the MGK and in Turkey–EU relations can be best understood with the historical institutionalist concept of punctuated equilibrium

Island endemism, morphological stasis, and possible cryptic speciation in two coral reef, commensal Leucothoid amphipod species throughout Florida and the Caribbean

Coral reefs are believed to be one of the most diverse ecosystems, but the true magnitude of their biodiversity and patterns of endemism is uncertain. This uncertainty stems partly from the relative paucity of investigations on the small, difficult to collect taxa (cryptofauna) that may make up the majority of reef biodiversity and require specialized expertise for morphological identification. To assess the extent of diversity in some of the reef micro-cryptofauna, we analyzed 414 bp of the mitochondrial cytochrome oxidase subunit I gene from 556 individuals representing two brooding amphipod species (Leu- cothoe ashleyae and Leucothoe kensleyi). These amphipods are commensal inside the branching vase sponge Callyspongia vaginalis, and were sampled throughout Florida and the Caribbean. Phylogenetic analyses revealed 11 deeply divergent, strongly supported lineages (seven L. ashleyae and four L. kensleyi) each with very narrow geographic ranges. The level of intraspecific lineage divergence for both morphospecies was among the highest reported for any marine crustacean (12.4-26.0% uncorrected), and exceeded that of congeners from nine diverse amphipod families, as well as the patristic genetic distance suggested as a threshold for crustacean species delineation. These findings suggest a his- tory of cryptic speciation within each morphospecies, concomitant with a pronounced period of morphological stasis involving each of the morphotypes. The observation of multiple, highly divergent, evolutionary significant units, each endemic to Florida and Caribbean island locations, supports the emerging view that coral reef biodiversity, especially in the cryptofaunal component, is likely vastly underestimated.

Cretaceous origin and repeated tertiary diversification of the redefined butterflies.

Although the taxonomy of the ca 18 000 species of butterflies and skippers is well known, the family-level relationships are still debated. Here, we present, to our knowledge, the most comprehensive phylogenetic analysis of the superfamilies Papilionoidea, Hesperioidea and Hedyloidea to date based on morphological and molecular data. We reconstructed their phylogenetic relationships using parsimony and Bayesian approaches. We estimated times and rates of diversification along lineages in order to reconstruct their evolutionary history. Our results suggest that the butterflies, as traditionally understood, are paraphyletic, with Papilionidae being the sister-group to Hesperioidea, Hedyloidea and all other butterflies. Hence, the families in the current three superfamilies should be placed in a single superfamily Papilionoidea. In addition, we find that Hedylidae is sister to Hesperiidae, and this novel relationship is supported by two morphological characters. The families diverged in the Early Cretaceous but diversified after the Cretaceous-Palaeogene event. The diversification of butterflies is characterized by a slow speciation rate in the lineage leading to Baronia brevicornis, a period of stasis by the skippers after divergence and a burst of diversification in the lineages leading to Nymphalidae, Riodinidae and Lycaenidae.

Punctuated equilibrium in the energy regime complex

The concept of a regime complex has proved fruitful to a burgeoning literature in international relations, but it has also opened up new questions about how and why they develop over time. This article describes the history of the energy regime complex as it has changed over the past 40 years, and interprets this history in light of an interpretive framework of the sources of institutional change. One of its principal contributions is to highlight what Stephen Krasner referred to as a pattern of “punctuated equilibrium” reflecting both periods of stasis and periods of innovation, as opposed to a gradual process of change. We show that the timing of innovation depends on dissatisfaction and shocks and that the nature of innovation—that is, whether it is path-dependent or de novo—depends on interest homogeneity among major actors. This paper is the first to demonstrate the empirical applicability of the punctuated equilibrium concept to international regime complexes, and contributes to the eventual development of a dynamic theory of change in regime complexes.

Uneven rise in N inputs to the Lake Michigan Basin over the 20th century corresponds to agricultural and societal transitions

By constructing nitrogen (N) budgets from 1880 to 2002 for watersheds that have undergone urbanization, intensive agricultural specialization or experienced minimal change, we document an uneven timeline of increase in anthropogenic N inputs. N loading to the watersheds of the Lake Michigan Basin grew six-fold from 1880 to 2002, peaking in 1987. Human activities influenced N inputs as early as 1880, and the magnitude and timing of increase differed markedly across regions in accord with population growth, land use, and type of agriculture. The greatest increase occurred from 1950 to 1980, corresponding with rapidly accelerating use of artificial fertilizers, but increases in atmospheric deposition and shifting patterns in crop and livestock production also affected trends. Net anthropogenic N inputs have changed little since about 1980, showing a modest decline due to a leveling out of fertilizer use and greater export of animal feed and products. Using a model that predicts riverine N export from watershed N loadings and river discharge, we found that river TN fluxes from all tributaries increased approximately threefold from 1900 to 2000 but have stabilized or declined over the past two decades, consistent with national surveys that show near-constant or declining riverine TN concentrations. For the LMB, the past two decades has been a period of relative stasis in N inputs to its terrestrial systems and N export from watersheds. This retrospective analysis also points to the challenge of forecasting future trends in N budget terms, which can both increase and decline in response to policy and societal transitions.

Investigating the drivers of maturation dynamics in Barents Sea haddock ( Melanogrammus aeglefinus)

Changes in size and age at maturation of many exploited fish stocks have been investigated and the influences of environmental factors and exploitation have often been inferred, but not explicitly investigated. Here we determine probabilistic maturation reaction norms (PMRNs) for Barents Sea haddock ( Melanogrammus aeglefinus) using generalized linear models (GLMs) and mixed effect models (GLMMs), which account for the correlation among samples within a tow station, and investigate the effects of fishing mortality, environmental factors (NAO, water temperature, and salinity), and potential density dependence or species interaction effects. We found little evidence of a consistent trend in maturation tendencies for Barents Sea haddock for cohorts 1983–2003, ages 4–6 years. Female haddock matured at larger lengths for a given age than males, but overall patterns were similar for both sexes. The GLMM approach gave consistently higher PMRN midpoint estimates than the GLM approach, which indicated that PMRNs that do not account for correlations within the data may bias estimates. Environmental factors, rather than exploitation, density dependence, or species interactions, were responsible for the observed changes in size and age at maturation in Barents Sea haddock during the late 1980s through early 2000s. Little evidence of fisheries-induced evolution was found in these fish over the time period investigated. The lack of a significant temporal trend in maturation may be due to several challenges in estimating representative population parameters for this stock, the trait change being in a period of stasis or reversal, or adaptation by the fish to higher exploitation in the past resulting in negligible evolutionary selection during the study period when exploitation has been more moderate.

The stratigraphic filter and bias in measurement of geologic rates

[1] Erosion and deposition rates estimated from the stratigraphic record frequently exhibit a power-law dependence on measurement interval. This dependence can result from a power-law distribution of stratigraphic hiatuses. By representing the stratigraphic filter as a stochastic process called a reverse ascending ladder, we describe a likely origin of power-law hiatuses, and thus, rate scaling. While power-law hiatuses in certain environments can be a direct result of power-law periods of stasis (no deposition or erosion), they are more generally the result of randomness in surface fluctuations irrespective of mean subsidence or uplift. Autocorrelation in fluctuations can make hiatuses more or less heavy-tailed, but still exhibit power-law characteristics. In addition we show that by passing stratigraphic data backward through the filter, certain statistics of surface kinematics from their formative environments can be inferred.