bluuebunny/crossref_metadata_2025 huggingface dataset:
Reticulon-4A (Nogo-A) Redistributes Protein Disulfide Isomerase to Protect Mice from SOD1-Dependent Amyotrophic Lateral Sclerosis
Authors: Yang Yvonne S. , Harel Noam Y. , Strittmatter Stephen M.
Published: November 2009

Amyotrophic lateral sclerosis (ALS) is a fatal motor neuron disease inherited in a small subset of patients. The SOD1(G93A) transgenic mouse models this subset of patients, and studies of this strain have suggested that endoplasmic reticulum (ER) stress and deficits in ER chaperone function are contributors to ALS pathophysiology. Here, we demonstrate that the reticulon family of proteins is a novel regulator of the ER chaperone protein disulfide isomerase (PDI), and that through PDI, reticulon-4A (Nogo-A) can protect mice against the neurodegeneration that characterizes ALS. We show that overexpressing reticulon protein induces a punctate redistribution of PDI intracellularly, bothin vitroandin vivo. Conversely, reduction of endogenous NogoA expression causes a more homogeneous expression patternin vivo. These effects occur without induction of the unfolded protein response. To examine the effect of PDI redistribution on ALS disease progression, we conducted survival and behavior studies of SOD1(G93A) mice. Deletion of a single copy of the NogoA,B gene accelerates disease onset and progression, while deletion of both copies further worsens disease. We conclude that NogoA contributes to the proper function of the ER resident chaperone PDI, and is protective against ALS-like neurodegeneration. Our results provide a novel intracellular role for reticulon proteins and support the hypothesis that modulation of PDI function is a potential therapeutic approach to ALS.
Neuroligin-2 Deletion Selectively Decreases Inhibitory Synaptic Transmission Originating from Fast-Spiking but Not from Somatostatin-Positive Interneurons
Authors: Gibson Jay R. , Huber Kimberly M. , Südhof Thomas C.
Published: November 2009

Neuroligins are cell adhesion molecules involved in synapse formation and/or function. Neurons express four neuroligins (NL1–NL4), of which NL1 is specific to excitatory and NL2 to inhibitory synapses. Excitatory and inhibitory synapses include numerous subtypes. However, it is unknown whether NL1 performs similar functions in all excitatory and NL2 in all inhibitory synapses, or whether they regulate the formation and/or function of specific subsets of synapses. To address this central question, we performed paired recordings in primary somatosensory cortex of mice lacking NL1 or NL2. Using this system, we examined neocortical microcircuits formed by reciprocal synapses between excitatory neurons and two subtypes of inhibitory interneurons, namely, fast-spiking and somatostatin-positive interneurons. We find that the NL1 deletion had little effect on inhibitory synapses, whereas the NL2 deletion decreased (40–50%) the unitary (cell-to-cell) IPSC amplitude evoked from single fast-spiking interneurons. Strikingly, the NL2 deletion had no effect on IPSC amplitude evoked from single somatostatin-positive inhibitory interneurons. Moreover, the frequency of unitary synaptic connections between individual fast-spiking and somatostatin-positive interneurons and excitatory neurons was unchanged. The decrease in unitary IPSC amplitude originating from fast-spiking interneurons in NL2-deficient mice was due to a multiplicative and uniform downscaling of the amplitude distribution, which in turn was mediated by a decrease in both synaptic quantal amplitude and quantal content, the latter inferred from an increase in the coefficient of variation. Thus, NL2 is not necessary for establishing unitary inhibitory synaptic connections but is selectively required for “scaling up” unitary connections originating from a subset of interneurons.
Functional Clustering of Neurons in Motor Cortex Determined by Cellular Resolution Imaging in Awake Behaving Mice
Authors: Dombeck Daniel A. , Graziano Michael S. , Tank David W.
Published: November 2009

Macroscopic (millimeter scale) functional clustering is a hallmark characteristic of motor cortex spatial organization in awake behaving mammals; however, almost no information is known about the functional micro-organization (∼100 μm scale). Here, we optically recorded intracellular calcium transients of layer 2/3 neurons with cellular resolution over ∼200-μm-diameter fields in the forelimb motor cortex of mobile, head-restrained mice during two distinct movements (running and grooming). We showed that the temporal correlation between neurons was statistically larger the closer the neurons were to each other. We further explored this correlation by using two separate methods to spatially segment the neurons within each imaging field: K-means clustering and correlations between single neuron activity and mouse movements. The two methods segmented the neurons similarly and led to the conclusion that the origin of the inverse relationship between correlation and distance seen statistically was twofold: clusters of highly temporally correlated neurons were often spatially distinct from one another, and (even when the clusters were spatially intermingled) within the clusters, the more correlated the neurons were to each other, the shorter the distance between them. Our results represent a direct observation of functional clustering within the microcircuitry of the awake mouse motor cortex.
Reliability and Precision of the Mouse Calyx of Held Synapse
Authors: Lorteije Jeannette A. M. , Rusu Silviu I. , Kushmerick Christopher , Borst J. Gerard G.
Published: November 2009

Traditionally, the calyx of Held synapse is viewed as a highly reliable relay in the sound localization circuit of the auditory brainstem, with every presynaptic action potential triggering a postsynaptic action potentialin vivo. However, this view is at odds with slice recordings that report large short-term depression (STD). To investigate the reliability and precision of this synapse, we compared slice andin vivorecordings from medial nucleus of the trapezoid body neurons of young adult mice. We show that the extracellularly recorded complex waveform can be used to estimate both presynaptic release and postsynaptic excitability. Whereas under standard slice conditions the synapse underwent large STD, both extracellular and whole-cell recordings indicated thatin vivothe size of the EPSPs was independent of recent history. The estimated quantal content was typically <20in vivo, much lower than in the resting synapse under standard slice conditions. However, due to the large quantal size and summation of EPSPs, the safety factor of this synapse was generally still sufficiently large and postsynaptic failures were observed only infrequentlyin vivo. When present, failures were typically due to stochastic fluctuations in EPSP size or postsynaptic spike depression.In vivo, the calyx of Held synapse thus functions as a tonic synapse. The price it pays for its low release probability is an increase in jitter and synaptic latency and occasional postsynaptic failures.
Enduring Reversal of Neuropathic Pain by a Single Intrathecal Injection of Adenosine 2A Receptor Agonists: A Novel Therapy for Neuropathic Pain
Authors: Loram Lisa C. , Harrison Jacqueline A. , Sloane Evan M. , Hutchinson Mark R. , Sholar Paige , Taylor Frederick R. , Berkelhammer Debra , Coats Benjamen D. , Poole Stephen , Milligan Erin D. , Maier Steven F. , Rieger Jayson , Watkins Linda R.
Published: November 2009

Previous studies of peripheral immune cells have documented that activation of adenosine 2A receptors (A2ARs) decrease proinflammatory cytokine release and increase release of the potent anti-inflammatory cytokine, interleukin-10 (IL-10). Given the growing literature supporting that glial proinflammatory cytokines importantly contribute to neuropathic pain and that IL-10 can suppress such pain, we evaluated the effects of intrathecally administered A2AR agonists on neuropathic pain using the chronic constriction injury (CCI) model. A single intrathecal injection of the A2AR agonists 4-(3-(6-amino-9-(5-cyclopropylcarbamoyl-3,4-dihydroxytetrahydrofuran-2-yl)-9H-purin-2-yl)prop-2-ynyl)piperidine-1-carboxylic acid methyl ester (ATL313) or 2-p-(2-carboxyethyl)phenethylamino-5′-N-ethylcarboxamido adenosine HCl (CGS21680), 10–14 d after CCI versus sham surgery, produced a long-duration reversal of mechanical allodynia and thermal hyperalgesia for at least 4 weeks. Neither drug altered the nociceptive responses of sham-operated controls. An A2AR antagonist [ZM241385 (4-(2-[7-amino-2-(2-furyl)(1,2,4)triazolo(2,3-a)(1,3,5)triazin-5-ylamino]ethyl)phenol)] coadministered intrathecally with ATL313 abolished the action of ATL313 in rats with neuropathy-induced allodynia but had no effect on allodynia in the absence of the A2AR agonist. ATL313 attenuated CCI-induced upregulation of spinal cord activation markers for microglia and astrocytes in the L4–L6 spinal cord segments both 1 and 4 weeks after a single intrathecal ATL313 administration. Neutralizing IL-10 antibodies administered intrathecally transiently abolished the effect of ATL313 on neuropathic pain. In addition, IL-10 mRNA was significantly elevated in the CSF cells collected from the lumbar region. Activation of A2ARs after intrathecal administration may be a novel, therapeutic approach for the treatment of neuropathic pain by increasing IL-10 in the immunocompetent cells of the CNS.
Two Classes of GABAergic Neurons in the Inferior Colliculus
Authors: Ito Tetsufumi , Bishop Deborah C. , Oliver Douglas L.
Published: November 2009

The inferior colliculus (IC) is unique, having both glutamatergic and GABAergic projections ascending to the thalamus. Although subpopulations of GABAergic neurons in the IC have been proposed, criteria to distinguish them have been elusive and specific types have not been associated with specific neural circuits. Recently, the largest IC neurons were found to be recipients of somatic terminals containing vesicular glutamate transporter 2 (VGLUT2). Here, we show with electron microscopy that VGLUT2-positive (VGLUT2+) axonal terminals make axosomatic synapses on IC neurons. These terminals contain only VGLUT2 even though others in the IC have VGLUT1 or both VGLUT1 and 2. We demonstrate that there are two types of GABAergic neurons: larger neurons with VGLUT2+axosomatic endings and smaller neurons without such endings. Both types are present in all subdivisions of the IC, but larger GABAergic neurons with VGLUT2+axosomatic terminals are most prevalent in the central nucleus. The GABAergic tectothalamic neurons consist almost entirely of the larger cells surrounded by VGLUT2+axosomatic endings. Thus, two types of GABAergic neurons in the IC are defined by different synaptic organization and neuronal connections. Larger tectothalamic GABAergic neurons are covered with glutamatergic axosomatic synapses that could allow them to fire rapidly and overcome a slow membrane time constant; their axons may be the largest in the brachium of the IC. Thus, large GABAergic neurons could deliver IPSPs to the medial geniculate body before EPSPs from glutamatergic IC neurons firing simultaneously.
Brain Gray Matter Decrease in Chronic Pain Is the Consequence and Not the Cause of Pain
Authors: Rodriguez-Raecke Rea , Niemeier Andreas , Ihle Kristin , Ruether Wolfgang , May Arne
Published: November 2009

Recently, local morphologic alterations of the brain in areas ascribable to the transmission of pain were reported in patients suffering from chronic pain. Although some authors discussed these findings as damage or loss of brain gray matter, one of the key questions is whether these structural alterations in the cerebral pain-transmitting network precede or succeed the chronicity of pain. We investigated 32 patients with chronic pain due to primary hip osteoarthritis and found a characteristic gray matter decrease in patients compared with controls in the anterior cingulate cortex (ACC), right insular cortex and operculum, dorsolateral prefrontal cortex (DLPFC), amygdala, and brainstem. We then investigated a subgroup of these patients (n= 10) 6 weeks and 4 months after total hip replacement surgery, monitoring whole brain structure. After surgery, all 10 patients were completely pain free and we observed a gray matter increase in the DLPFC, ACC, amygdala, and brainstem. As gray matter decrease is at least partly reversible when pain is successfully treated, we suggest that the gray matter abnormalities found in chronic pain do not reflect brain damage but rather are a reversible consequence of chronic nociceptive transmission, which normalizes when the pain is adequately treated.
Range-Adapting Representation of Economic Value in the Orbitofrontal Cortex
Authors: Padoa-Schioppa Camillo
Published: November 2009

While making economic choices, individuals assign subjective values to the available options. Values computed in different behavioral conditions, however, can vary substantially. The same person might choose some times between goods worth a few dollars, and other times between goods worth thousands of dollars, or more. How does the brain system that computes values—the “valuation system”—handle this large variability? Here we show that the representation of value in the orbitofrontal cortex (OFC), an area implicated in value assignment during economic choice, adapts to the behavioral condition of choice and, more specifically, to the range of values available in any given condition. In the experiments, monkeys chose between different juices and their choice patterns provided a measure of subjective value. Value ranges were varied from session to session and, in each session, OFC neurons encoded values in a linear way. Across the population, the neuronal sensitivity (defined as the change in neuronal activity elicited by the increase in one value unit) was inversely proportional to the value range. Conversely, the neuronal activity range did not depend on the value range. This phenomenon of range adaptation complements that of menu invariance observed in a previous study. Indeed, the activity of each neuron adapts to the range values it encodes but does not depend on other available goods. Our results thus suggest that the representation of value in the OFC is at one time instantiative of preference transitivity (menu invariance) and computationally efficient (range adaptation).
Retinotopic Mapping Requires Focal Adhesion Kinase-Mediated Regulation of Growth Cone Adhesion
Authors: Woo Stephanie , Rowan Daniel J. , Gomez Timothy M.
Published: November 2009

Adhesion controls growth cone motility, yet the effects of axon guidance cues on adhesion site dynamics are poorly understood. Here we show that ephrin-A1 reduces retinal ganglion cell (RGC) axon outgrowth by stabilizing existing adhesions and inhibiting new adhesion assembly. Ephrin-A1 activates focal adhesion kinase (FAK) in an integrin- and Src-dependent manner and the effects of ephrin-A1 on growth cone motility require FAK activation. We also find that FAK is expressed in a high temporal to low nasal gradient in RGCs, similar to EphA receptors, and that balanced FAK activation is necessary for optimal axon outgrowth. Last, we find that FAK is required for proper topographic positioning of retinal axons along the anterior–posterior axis of the optic tectum in bothXenopusand zebrafish, a guidance decision mediated in part by A-type ephrins. Together, our data suggest that ephrin-A1 controls growth cone advance by modulating adhesive point contacts through FAK activation and that graded FAK signaling is an important component of ephrin-A-mediated retinotopic mapping.
Sleep Deprivation Differentially Impairs Cognitive Performance in Abstinent Methylenedioxymethamphetamine (“Ecstasy”) Users
Authors: McCann Una D. , Wilson Michael J. , Sgambati Francis P. , Ricaurte George A.
Published: November 2009

Methylenedioxymethamphetamine (MDMA; “Ecstasy”) is a popular recreational drug and brain serotonin (5-HT) neurotoxin. Neuroimaging data indicate that some human MDMA users develop persistent deficits in brain 5-HT neuronal markers. Although the consequences of MDMA-induced 5-HT neurotoxicity are not fully understood, abstinent MDMA users have been found to have subtle cognitive deficits and altered sleep architecture. The present study sought to test the hypothesis that sleep disturbance plays a role in cognitive deficits in MDMA users. Nineteen abstinent MDMA users and 21 control subjects participated in a 5 d inpatient study in a clinical research unit. Baseline sleep quality was measured using the Pittsburgh Sleep Quality Inventory. Cognitive performance was tested three times daily using a computerized cognitive battery. On the third day of admission, subjects began a 40 h sleep deprivation period and continued cognitive testing using the same daily schedule. At baseline, MDMA users performed less accurately than controls on a task of working memory and more impulsively on four of the seven computerized tests. During sleep deprivation, MDMA users, but not controls, became increasingly impulsive, performing more rapidly at the expense of accuracy on tasks of working and short-term memory. Tests of mediation implicated baseline sleep disturbance in the cognitive decline seen during sleep deprivation. These findings are the first to demonstrate that memory problems in MDMA users may be related, at least in part, to sleep disturbance and suggest that cognitive deficits in MDMA users may become more prominent in situations associated with sleep deprivation.
Transgenerational effects of the endocrine disruptor vinclozolin on the methylation pattern of imprinted genes in the mouse sperm
Authors: Stouder Christelle , Paoloni-Giacobino Ariane
Published: November 2009

Endocrine-disrupting chemicals (EDCs), among which is the antiandrogen vinclozolin (VCZ), have been reported to affect the male reproductive system. In this study, VCZ was administered to pregnant mice at the time of embryo sex determination, and its possible effects on the differentially methylated domains (DMDs) of two paternally (H19andGtl2) and three maternally (Peg1,Snrpn, andPeg3) imprinted genes were tested in the male offspring. The CpGs methylation status within the five gene DMDs was analyzed in the sperm, tail, liver, and skeletal muscle DNAs by pyrosequencing. In the sperm of controls, the percentages of methylated CpGs were close to the theoretical values of 100 and 0% in paternally or maternally imprinted genes respectively. VCZ decreased the percentages of methylated CpGs ofH19andGtl2(respective values 83.1 and 91.5%) and increased those ofPeg1,Snrpn, andPeg3(respective values 11.3, 18.3, and 11.2%). The effects of VCZ were transgenerational, but they disappeared gradually from F1 to F3. The mean sperm concentration of the VCZ-administered female offspring was only 56% of that of the controls in the F1 offspring, and it was back to normal values in the F2 and F3 offspring. In the somatic cells of controls, the percentages of methylated CpGs were close to the theoretical value of 50% and, surprisingly, VCZ altered the methylation ofPeg3. We propose that the deleterious effects of VCZ on the male reproductive system are mediated by imprinting defects in the sperm. The reported effects of EDCs on human male spermatogenesis might be mediated by analogous imprinting alterations.
A Case of Advanced Medullary Thyroid Carcinoma Successfully Treated with Sunitinib
Authors: Bugalho Maria João , Domingues Rita , Borges Alexandra
Published: November 2009

Context.

Medullary thyroid carcinoma (MTC) is a neuroendocrine tumor arising from “C” cells of the thyroid; it is a RET associated cancer that can be sporadic or familial in origin. Advances in understanding the genetic changes associated with the development of MTC explain the growing interest in the therapeutic potential of tyrosine kinase inhibitors. Sunitinib is an orally administered multikinase inhibitor likely to target multiple pathways in the tumor, stromal, and endothelial compartments. Its role in the treatment of MTC patients has not yet been established.

Objective.

To present the case of a patient with a sporadic and unresectable MTC who was successfully treated with sunitinib.

Patient and Results.

A 55-year-old man with locally advanced MTC, without germinal and/or somatic RET mutations, was started on sunitinib (50 mg/day for 28 days, followed by 14 days of no treatment). At the time of writing, he had received four consecutive cycles. At the end of the first cycle, his serum calcitonin level had dropped by 81%. In the following cycles, a long-lasting minor response was observed. An early and dramatic tumor reduction, particularly of a cervical lymph node conglomerate, was observed and confirmed by the Response Evaluation Criteria in Solid Tumors.

Conclusion.

Sunitinib may play a role in the management of patients with locally advanced MTC or distant metastatic disease, for which no effective systemic therapy exists. Moreover, the absence of RET mutations does not seem to be an exclusion criterion for sunitinib treatment.
Statistical performance and information content of time lag analysis and redundancy analysis in time series modeling
Authors: Angeler David G. , Viedma Olga , Moreno JoséM.
Published: November 2009

Time lag analysis (TLA) is a distance‐based approach used to study temporal dynamics of ecological communities by measuring community dissimilarity over increasing time lags. Despite its increased use in recent years, its performance in comparison with other more direct methods (i.e., canonical ordination) has not been evaluated. This study fills this gap using extensive simulations and real data sets from experimental temporary ponds (true zooplankton communities) and landscape studies (landscape categories as pseudo‐communities) that differ in community structure and anthropogenic stress history. Modeling time with a principal coordinate of neighborhood matrices (PCNM) approach, the canonical ordination technique (redundancy analysis; RDA) consistently outperformed the other statistical tests (i.e., TLAs, Mantel test, and RDA based on linear time trends) using all real data. In addition, the RDA‐PCNM revealed different patterns of temporal change, and the strength of each individual time pattern, in terms of adjusted variance explained, could be evaluated. It also identified species contributions to these patterns of temporal change. This additional information is not provided by distance‐based methods. The simulation study revealed better Type I error properties of the canonical ordination techniques compared with the distance‐based approaches when no deterministic component of change was imposed on the communities. The simulation also revealed that strong emphasis on uniform deterministic change and low variability at other temporal scales is needed to result in decreased statistical power of the RDA‐PCNM approach relative to the other methods. Based on the statistical performance of and information content provided by RDA‐PCNM models, this technique serves ecologists as a powerful tool for modeling temporal change of ecological (pseudo‐) communities.
Estimating dispersal from genetic isolation by distance in a coral reef fish (Hypoplectrus puella)
Authors: Puebla Oscar , Bermingham Eldredge , Guichard Frédéric
Published: November 2009

The spatial scale of dispersal in coral reef fishes eludes ecologists despite the importance of this parameter for understanding the dynamics of ecological and evolutionary processes. Genetic isolation by distance (IBD) has been used to estimate dispersal in coral reef fishes, but its application in marine systems has been limited by insufficient sampling at different spatial scales and a lack of information regarding population density. Here, we present an analysis of IBD in the barred hamlet (Hypoplectrus puella, Serranidae) at spatial scales ranging from 10 to 3200 km complemented with SCUBA surveys of population densities covering 94 000 m2 of reef. We used 10 hypervariable DNA markers to genotype 854 fish from 15 locations, and our results establish that IBD in H. puella emerges at a spatial scale of 175 km and is preserved up to the regional scale (3200 km). Assuming a normal or a Laplace dispersal function, our data are consistent with mean dispersal distances in H. puella that range between 2 and 14 km. Such small mean dispersal distances is a surprising result given the three‐week pelagic larval duration of H. puella and the low level of genetic structure at the Caribbean scale (Wright's fixation index, FST, estimate = 0.005). Our data reinforce the importance of considering population density when estimating dispersal from IBD and underscore the relevance of sampling at local scales, even when genetic structure is weak at the regional scale.
Habitat‐specific breeder survival of Florida Scrub‐Jays: inferences from multistate models
Authors: Breininger David R. , Nichols James D. , Carter Geoffrey M. , Oddy Donna M.
Published: November 2009

Quantifying habitat‐specific survival and changes in habitat quality within disturbance‐prone habitats is critical for understanding population dynamics and variation in fitness, and for managing degraded ecosystems. We used 18 years of color‐banding data and multistate capture–recapture models to test whether habitat quality within territories influences survival and detection probability of breeding Florida Scrub‐Jays (Aphelocoma coerulescens) and to estimate bird transition probabilities from one territory quality state to another. Our study sites were along central Florida's Atlantic coast and included two of the four largest metapopulations within the species range. We developed Markov models for habitat transitions and compared these to bird transition probabilities. Florida Scrub‐Jay detection probabilities ranged from 0.88 in the tall territory state to 0.99 in the optimal state; detection probabilities were intermediate in the short state. Transition probabilities were similar for birds and habitat in grid cells mapped independently of birds. Thus, bird transitions resulted primarily from habitat transitions between states over time and not from bird movement. Survival ranged from 0.71 in the short state to 0.82 in the optimal state, with tall states being intermediate. We conclude that average Florida Scrub‐Jay survival will remain at levels that lead to continued population declines because most current habitat quality is only marginally suitable across most of the species range. Improvements in habitat are likely to be slow and difficult because tall states are resistant to change and the optimal state represents an intermediate transitional stage. The multistate modeling approach to quantifying survival and habitat transition probabilities is useful for quantifying habitat transition probabilities and comparing them to bird transition probabilities to test for habitat selection in dynamic environments.
Direct and indirect effects of giant kelp determine benthic community structure and dynamics
Authors: Arkema Katie K. , Reed Daniel C. , Schroeter Stephen C.
Published: November 2009

Indirect facilitation can occur when a species positively affects another via the suppression of a shared competitor. In giant kelp forests, shade from the canopy of the giant kelp, Macrocystis pyrifera, negatively affects understory algae, which compete with sessile invertebrates for space. This raises the possibility that giant kelp indirectly facilitates sessile invertebrates, via suppression of understory algae. We evaluated the effect of giant kelp on the relative abundance of algae and invertebrates by experimentally manipulating kelp abundance on large artificial reefs located off San Clemente, California, USA. The experiments revealed a negative effect of giant kelp on both light availability and understory algal abundance and a positive effect on the abundance of sessile invertebrates, which was consistent with an indirect effect mediated by shade from the kelp canopy. The importance of these processes to temporal variability in benthic community structure was evaluated at 16 locations on natural reefs off Santa Barbara, California, over an eight‐year period. Interannual variability in the abundance of understory algae and in the abundance of sessile invertebrates was significantly and positively related to interannual variability in the abundance of giant kelp. Analysis of these observational data using Structural Equation Modeling (SEM) indicated that the magnitude of the indirect effect of giant kelp on invertebrates was six times larger than the direct effect on invertebrates. Results suggest that the dynamics of this system are driven by variability in the abundance of a single structure‐forming species that has indirect positive, as well as direct negative, effects on associated species.
Wolverine gene flow across a narrow climatic niche
Authors: Schwartz Michael K. , Copeland Jeffrey P. , Anderson Neil J. , Squires John R. , Inman Robert M. , McKelvey Kevin S. , Pilgrim Kristy L. , Waits Lisette P. , Cushman Samuel A.
Published: November 2009

Wolverines (Gulo gulo) are one of the rarest carnivores in the contiguous United States. Effective population sizes in Montana, Idaho, and Wyoming, where most of the wolverines in the contiguous United States exist, were calculated to be 35 (credible limits, 28–52) suggesting low abundance. Landscape features that influence wolverine population substructure and gene flow are largely unknown. Recent work has identified strong associations between areas with persistent spring snow and wolverine presence and range. We tested whether a dispersal model in which wolverines prefer to disperse through areas characterized by persistent spring snow cover produced least‐cost paths among all individuals that correlated with genetic distance among individuals. Models simulating large preferences for dispersing within areas characterized by persistent spring snow explained the data better than a model based on Euclidean distance. Partial Mantel tests separating Euclidean distance from spring snow‐cover‐based effects indicated that Euclidean distance was not significant in describing patterns of genetic distance. Because these models indicated that successful dispersal paths followed areas characterized by spring snow cover, we used these understandings to derive empirically based least‐cost corridor maps in the U.S. Rocky Mountains. These corridor maps largely explain previously published population subdivision patterns based on mitochondrial DNA and indicate that natural colonization of the southern Rocky Mountains by wolverines will be difficult but not impossible.
Bayesian inference in camera trapping studies for a class of spatial capture–recapture models
Authors: Royle J. Andrew , Karanth K. Ullas , Gopalaswamy Arjun M. , Kumar N. Samba
Published: November 2009

We develop a class of models for inference about abundance or density using spatial capture–recapture data from studies based on camera trapping and related methods. The model is a hierarchical model composed of two components: a point process model describing the distribution of individuals in space (or their home range centers) and a model describing the observation of individuals in traps. We suppose that trap‐ and individual‐specific capture probabilities are a function of distance between individual home range centers and trap locations. We show that the models can be regarded as generalized linear mixed models, where the individual home range centers are random effects. We adopt a Bayesian framework for inference under these models using a formulation based on data augmentation. We apply the models to camera trapping data on tigers from the Nagarahole Reserve, India, collected over 48 nights in 2006. For this study, 120 camera locations were used, but cameras were only operational at 30 locations during any given sample occasion. Movement of traps is common in many camera‐trapping studies and represents an important feature of the observation model that we address explicitly in our application.
Species–area relationships explained by the joint effects of dispersal limitation and habitat heterogeneity
Authors: Shen Guochun , Yu Mingjian , Hu Xin-Sheng , Mi Xiangcheng , Ren Haibao , Sun I-Fang , Ma Keping
Published: November 2009

Species–area relationships (SARs) characterize the spatial distribution of species diversity in community ecology, but the biological mechanisms underlying the SARs have not been fully explored. Here, we examined the roles of dispersal limitation and habitat heterogeneity in shaping SARs in two large‐scale forest plots. One is a 24‐ha subtropical forest in Gutianshan National Nature Reserve, China. The other is a 50‐ha tropical rain forest in Barro Colorado Island, Panama. Spatial point pattern models were applied to investigate the contributions of dispersal and habitat heterogeneity and their interactions to the formation of the SARs in the two sites. The results showed that, although dispersal and habitat heterogeneity each could significantly contribute to the SARs, each alone was insufficient to explain the SARs. Their joint effects sufficiently explained the real SARs, suggesting that heterogeneous habitat and dispersal limitation are two predominant mechanisms for maintaining the spatial distributions of the species in these two forests. These results add to our understanding of the ecological processes underlying the spatial variation of SARs in natural forest communities.
Spatial synchrony propagates through a forest food web via consumer–resource interactions
Authors: Haynes Kyle J. , Liebhold Andrew M. , Fearer Todd M. , Wang Guiming , Norman Gary W. , Johnson Derek M.
Published: November 2009

In many study systems, populations fluctuate synchronously across large regions. Several mechanisms have been advanced to explain this, but their importance in nature is often uncertain. Theoretical studies suggest that spatial synchrony initiated in one species through Moran effects may propagate among trophically linked species, but evidence for this in nature is lacking. By applying the nonparametric spatial correlation function to time series data, we discover that densities of the gypsy moth, the moth's chief predator (the white‐footed mouse), and the mouse's winter food source (red oak acorns) fluctuate synchronously over similar distances (∼1000 km) and with similar levels of synchrony. In addition, we investigate the importance of consumer–resource interactions in propagating synchrony among species using an empirically informed simulation model of interactions between acorns, the white‐footed mouse, the gypsy moth, and a viral pathogen of the gypsy moth. Our results reveal that regional stochasticity acting directly on populations of the mouse, moth, or pathogen likely has little effect on levels of the synchrony displayed by these species. In contrast, synchrony in mast seeding can propagate across trophic levels, thus explaining observed levels of synchrony in both white‐footed mouse and gypsy moth populations. This work suggests that the transfer of synchrony among trophically linked species may be a major factor causing interspecific synchrony.
Ecological divergence of two sympatric lineages of Buggy Creek virus, an arbovirus associated with birds
Authors: Brown Charles R. , Padhi Abinash , Moore Amy T. , Brown Mary Bomberger , Foster Jerome E. , Pfeffer Martin , O'Brien Valerie A. , Komar Nicholas
Published: November 2009

Most arthropod‐borne viruses (arboviruses) show distinct serological subtypes or evolutionary lineages, with the evolution of different strains often assumed to reflect differences in ecological selection pressures. Buggy Creek virus (BCRV) is an unusual RNA virus (Togaviridae,Alphavirus) that is associated primarily with a cimicid swallow bug (Oeciacus vicarius) as its vector and the Cliff Swallow (Petrochelidon pyrrhonota) and the introduced House Sparrow (Passer domesticus) as its amplifying hosts. There are two sympatric lineages of BCRV (lineages A and B) that differ from each other by >6% at the nucleotide level. Analysis of 385 BCRV isolates all collected from bug vectors at a study site in southwestern Nebraska, USA, showed that the lineages differed in their peak times of seasonal occurrence within a summer. Lineage A was more likely to be found at recently established colonies, at those in culverts (rather than on highway bridges), and at those with invasive House Sparrows, and in bugs on the outsides of nests. Genetic diversity of lineage A increased with bird colony size and at sites with House Sparrows, while that of lineage B decreased with colony size and was unaffected by House Sparrows. Lineage A was more cytopathic on mammalian cells than was lineage B. These two lineages have apparently diverged in their transmission dynamics, with lineage A possibly more dependent on birds and lineage B perhaps more a bug virus. The long‐standing association between Cliff Swallows and BCRV may have selected for immunological resistance to the virus by swallows and thus promoted the evolution of the more bug‐adapted lineage B. In contrast, the recent arrival of the introduced House Sparrow and its high competence as a BCRV amplifying host may be favoring the more bird‐dependent lineage A.
Trait‐dependent modification of facilitation on cobble beaches
Authors: Irving Andrew D. , Bertness Mark D.
Published: November 2009

Fundamental gaps remain in our knowledge of how positive species interactions, such as facilitation and mutualism, structure and maintain populations and communities. Foundation species create extensive biogenic habitats, but we know little of how their traits, such as density, age, and patch size, modify their ability to facilitate other species. We tested the role of facilitator traits in cobble beach plant communities in New England, USA. In this system, intertidal beds of the cordgrass Spartina alterniflora facilitate populations of halophytic forbs at higher shore elevations by buffering wave action, stabilizing cobbles, and limiting physical disturbance. Using descriptive and experimental techniques, we tested the hypotheses that (1) the density and height of cordgrass shoots modify the strength of the cordgrass–forb facilitation, and (2) cordgrass peat alone contributes to the facilitation of forbs. Increased shoot density, as well as the combination of cordgrass peat and shoots, positively affected two life history stages (seedling and adult) of the abundant forb Suaeda linearis, demonstrating that cordgrass traits modify the strength of facilitation in this system. Since the expression of traits varies within and among patches of any given foundation species, traits can and should be used to predict the strength of facilitation, to guide the development of conservation strategies, and to develop more accurate models of species interactions.
Genetic differences among populations of a marine snail drive geographic variation in predation
Authors: Sanford Eric , Worth David J.
Published: November 2009

The extent to which community processes can be generalized from local field studies to larger spatial scales remains a contentious issue. The search for broad generality can be hampered when species interactions vary geographically, a common phenomenon attributed to a wide range of underlying ecological factors. Less attention has been directed toward understanding the additional role that evolutionary processes may play in modifying the way that pairs of species interact over large spatial scales. Here we examine whether marked geographic variation in the interaction between a predatory snail (Nucella canaliculata) and an intertidal mussel (Mytilus californianus) arises from phenotypic plasticity or fixed genetic differences among snail populations. Over a three‐year period, we reared snails from eight populations in California and Oregon, USA, through two laboratory generations and tested whether family lines differed in their ability to drill M. californianus. Remarkably, F2 generation snails from Oregon sources were generally unable to drill mid‐sized Mytilus californianus (5–7 cm long), whereas snails from California readily drilled this prey. Because snails were raised through two generations on a common diet (Mytilus trossulus), these differences among populations likely have a genetic basis. Snails from California and Oregon readily interbred and produced viable offspring in the laboratory, suggesting that populations belong to a single biological species. Field surveys of mussel beds revealed striking geographic variation in predation that closely matched the observed differences in the drilling capacity of N. canaliculata. Drilled M. californianus were common at all sites in California and included many large mussels (>10 cm long). In contrast, drilled M. californianus were rare on the central Oregon coast and consisted mostly of small mussels (<3 cm). We hypothesize that persistent variation in prey recruitment along the coast has selected for interpopulation differences in the drilling capacity of this direct‐developing snail, with potential consequences for the size structure of mussel beds. Combined with growing evidence of restricted gene flow and low connectivity among many marine populations, this study highlights the importance of considering the contribution of evolutionary processes to geographic variation in species interactions.
Assessing ecological specialization of an ant–seed dispersal mutualism through a wide geographic range
Authors: Manzaneda Antonio J. , Rey Pedro J.
Published: November 2009

Specialization in species interactions is of central importance for understanding the ecological structure and evolution of plant–animal mutualisms. Most plant–animal mutualisms are facultative and strongly asymmetric. In particular, myrmecochory (seed dispersal by ants) has been regarded as a very generalized interaction. Although some recent studies have suggested that only a few ant species are really important for dispersal, no rigorous measurement of the specialization in ant–seed dispersal mutualisms has been performed. Here, we use individual plants as basic units for replication to investigate the generalization–specialization of the herb Helleborus foetidus on its ant dispersers over a considerable part of its geographical range. We define generalization in terms of diversity components (species richness and evenness) of the ant visitor that realizes dispersal by removing diaspores. We obtain truly comparable values of ant visitor diversity, distinguishing among different functional groups of visitors and identifying incidental visitors and real ant dispersers. Using null model approaches, we test the null hypothesis that ant‐mediated dispersal is a generalized mutualism. At least two premises should be confirmed to validate the hypothesis: (1) diaspores are dispersed by multiple ant‐visitor species, and (2) diaspore dispersal is significantly equitable. Though up to 37 ant species visited diaspores across 10 populations, only two large formicines, Camponotus cruentatus and Formica lugubris, were responsible for the vast majority of visits resulting in dispersal in most populations and years, which strongly suggests that ant seed dispersal in H. foetidus is ecologically specialized. Interestingly, specialization degree was unrelated to dispersal success across populations. Our study offers new insights into the spatiotemporal dynamics of myrmecochory. We propose the existence of an alternative scenario to extensive generalization. In this new scenario, generalization is replaced by ecological specialization, which is determined by the intrinsic traits of the plant species rather than by the ecological context in which the interaction takes place.
Periodically forced food‐chain dynamics: model predictions and experimental validation
Authors: Steiner Christopher F. , Schwaderer Anne S. , Huber Veronika , Klausmeier Christopher A. , Litchman Elena
Published: November 2009

Despite the recognition of the importance of seasonal forcing in nature, remarkably few studies have theoretically explored periodically forced community dynamics. Here we employ a novel approach called “successional state dynamics” (SSD) to model a seasonally forced predator–prey system. We first generated analytical predictions of the effects of altered seasonality on species persistence and the timing of community state transitions. We then parameterized the model using a zooplankton–phytoplankton system and tested quantitative predictions using controlled experiments. In the majority of cases, timing of zooplankton and algal population peaks matched model predictions. Decreases in growing‐period length delayed algal blooms, consequently delaying peaks in zooplankton abundance. Predictions of increased probability of predator extinction at low growing‐period lengths were also upheld experimentally. Our results highlight the utility of the SSD modeling approach as a framework for predicting the effects of altered seasonality on the structure and dynamics of multitrophic communities.
Canopy height and ground elevation in a mixed‐land‐use lowland Neotropical rain forest landscape
Authors: Kellner James R. , Clark David B. , Hofton Michelle A.
Published: November 2009

We obtained spatially extensive canopy height measurements using airborne remote sensing to characterize the structure and dynamics of a tropical rain forest landscape. Light detection and ranging (LiDAR) is a remote‐sensing technology that acquires measurements of canopy height and ground elevation. By recording the return time of laser pulses emitted by aircraft‐mounted sensors, LiDAR systems quantify the structure and geometry of individual trees and canopy height and enable estimation of the vertical and horizontal distribution of biomass using millions of accurate height measurements. This data set contains 127 849 839 records from 128 square kilometers of tropical wet forest in the Atlantic lowlands of Costa Rica (mean sampling density is 1.99 observations/m2). The study area includes all 16 square kilometers of mixed‐land‐use forest at the La Selva Biological Station and the lower flanks of Braulio Carrillo National Park. It contains a mosaic of historical and contemporary land use that is representative of contemporary tropical forest landscapes. Field studies demonstrated that LiDAR measurements were precise and accurate throughout the topographic and structural conditions at the site. Each record includes: easting and northing mapped coordinates (UTM Zone 16 North), height above ground (m), interpolated ground elevation (m), and six remote‐sensing descriptors (point classification, the return number, the number of returns for the given pulse, intensity, scan angle, and the time of emission of the laser pulse). The data can be applied to a wide range of questions in basic and applied science, and are a valuable resource from a well‐studied tropical rain forest for teaching and education. They also provide a quantitative baseline against which future conditions can be assessed.

The complete data sets corresponding to abstracts published in the Data Papers section of the journal are published electronically in Ecological Archives at 〈http://esapubs.org/archive〉. (The accession number for each Data Paper is given directly beneath the title.)