140 Works

Increasing stimulus similarity drives nonmonotonic representational change in hippocampus

Jeffrey Wammes
Studies of hippocampal learning have obtained seemingly contradictory results, with manipulations that increase coactivation of memories sometimes leading to differentiation of these memories, but sometimes not. These results could potentially be reconciled using the nonmonotonic plasticity hypothesis, which posits that representational change (memories moving apart or together) is a U-shaped function of the coactivation of these memories during learning. Testing this hypothesis requires manipulating coactivation over a wide enough range to reveal the full U-shape....

International Borrowing, Specialization and Unemployment in a Small, Open Economy

Patrick N. Osakwe & Shouyong Shi
Empirical evidence suggests that the unemployment rate and the export/GNP ratio are positively correlated with external debt across developing countries. This paper develops a dynamic model that provides an explanation for the aforementioned relationships. The central idea of our paper is that international borrowing affects unemployment and specialization patterns by unevenly changing the risk-sharing structure—across sectors—between firms and workers. The economy produces a domestic good and an export good and faces uncertainty in its terms...

Data from: The jellification of north temperate lakes

Adam Jeziorski, Andrew J. Tanentzap, Norman D. Yan, Andrew M. Paterson, Michelle E. Palmer, Jennifer B. Korosi, James A. Rusak, Michael T. Arts, Wendell Bill Keller, Ron Ingram, Allegra Cairns, John P. Smol & W. Keller
Calcium (Ca) concentrations are decreasing in softwater lakes across eastern North America and western Europe. Using long-term contemporary and palaeo-environmental field data, we show that this is precipitating a dramatic change in Canadian lakes: the replacement of previously dominant pelagic herbivores (Ca-rich Daphnia species) by Holopedium glacialis, a jelly-clad, Ca-poor competitor. In some lakes, this transformation is being facilitated by increases in macro-invertebrate predation, both from native (Chaoborus spp.) and introduced (Bythotrephes longimanus) zooplanktivores, to...

Data from: Closely related species of birds differ more in body size when their ranges overlap—in warm, but not cool, climates

Emma Bothwell, Robert Montgomerie, Stephen C. Lougheed & Paul R. Martin
Differences in body size are widely thought to allow closely related species to coexist in sympatry, but body size also varies as an adaptive response to climate. Here, we use a sister lineage approach to test the prediction that body size differences between closely related species of birds worldwide are greater for species whose ranges are sympatric rather than allopatric. We further test if body size differences among sympatric versus allopatric species vary with geography,...

Data from: The signature of fine scale local adaptation in Atlantic salmon revealed from common garden experiments in nature

Ciar L O'Toole, Thomas E. Reed, Deborah Bailie, Caroline Bradley, Deirdre Cotter, Jamie Coughlan, Tom Cross, Eileen Dillane, Sarah McEvoy, Niall O'Maoileidigh, Paulo Prodöhl, Ger Rogan & Philip McGinnity
Understanding the extent, scale and genetic basis of local adaptation (LA) is important for conservation and management. Its relevance in salmonids at microgeographic scales, where dispersal (and hence potential gene flow) can be substantial, has however been questioned. Here, we compare the fitness of communally reared offspring of local and foreign Atlantic salmon Salmo salar from adjacent Irish rivers and reciprocal F1 hybrid crosses between them, in the wild ‘home’ environment of the local population....

Data from: Correlated evolution of mating system and floral display traits in flowering plants and its implications for the distribution of mating system variation

Carol Goodwillie, Risa D. Sargent, Susan Kalisz, Richard H. Ree, David A. Moeller, Mario Vallejo-Marin, Christopher G. Eckert, Alice A. Winn, Elizabeth Elle, Monica A. Geber & Mark O. Johnston
Reduced allocation to structures for pollinator attraction is predicted in selfing species. We explored the association between outcrossing and floral display in a broad sample of angiosperms. We used the demonstrated relationship to test for bias against selfing species in the outcrossing rate distribution, the shape of which has relevance for the stability of mixed mating. Relationships between outcrossing rate, flower size, flower number and floral display, measured as the product of flower size and...

Data from: Comparison of diets for largemouth and smallmouth bass in Eastern Lake Ontario using DNA barcoding and stable isotope analysis

Erich J.H. Nelson, Jeremy Holden, Robert Eves, Bruce Tufts & Erich J. H. Nelson
Largemouth (LMB: Micropterus salmoides) and Smallmouth Bass (SMB: Micropterus dolomieu) are important species in the recreational fisheries of the Laurentian Great Lakes. The invasion of the Round Goby (Neogobius melanostomus) into these lakes has changed several facets of black bass biology, but there is still much to learn about the relationship between these species. Previous dietary analyses have shown Round Goby to be important prey for bass, but have been limited by low visual identification...

Data from: Outlier analyses to test for local adaptation to breeding grounds in a migratory arctic seabird

Anna Tigano, Allison J. Shultz, Scott V. Edwards, Gregory J. Robertson & Vicki L. Friesen
Investigating the extent (or the existence) of local adaptation is crucial to understanding how populations adapt. When experiments or fitness measurements are difficult or impossible to perform in natural populations, genomic techniques allow us to investigate local adaptation through the comparison of allele frequencies and outlier loci along environmental clines. The thick-billed murre (Uria lomvia) is a highly philopatric colonial arctic seabird that occupies a significant environmental gradient, shows marked phenotypic differences among colonies, and...

Data from: Hydrogen sulfide regulates cardiovascular function by influencing the excitability of subfornical organ neurons

Markus Kuksis, Pauline M. Smith & Alastair V. Ferguson
Hydrogen sulfide (H2S), a gasotransmitter endogenously found in the central nervous system, has recently been suggested to act as a signalling molecule in the brain having beneficial effects on cardiovascular function. This study was thus undertaken to investigate the effect of NaHS (an H2S donor) in the subfornical organ (SFO), a central nervous system site important to blood pressure regulation. We used male Sprague-Dawley rats for both in vivo and in vitro experiments. We first...

Data from: The gravity of pollination: integrating at-site features into spatial analysis of contemporary pollen movement.

Michelle F. DiLeo, Jenna C. Siu, Matthew K. Rhodes, Adriana López-Villalobos, Angela Redwine, Kelly Ksiazek & Rodney J. Dyer
Pollen-mediated gene flow is a major driver of spatial genetic structure in plant populations. Both individual plant characteristics and site-specific features of the landscape can modify the perceived attractiveness of plants to their pollinators and thus play an important role in shaping spatial genetic variation. Most studies of landscape-level genetic connectivity in plants have focused on the effects of inter-individual distance using spatial and increasingly ecological separation; yet have not incorporated individual plant characteristics or...

Data from: Correlates of alternative migratory strategies in western bluebirds

Catherine A. Dale, Joseph J. Nocera, Samantha E. Franks, T. Kurt Kyser & Laurene M. Ratcliffe
Partial migration occurs when only some animals in a population migrate. While evidence suggests that migratory strategies are partially controlled by genes, individual and environmental conditions which alter the cost‐benefit trade‐off of migration among individuals are also likely to play a role. Three hypotheses have been advanced to explain condition‐dependent partial migration: the arrival time, dominance, and body size hypotheses. In this study, we asked whether these hypotheses explained differences in migratory strategy among individuals...

Data from: The influence of landscape on gene flow in the eastern massasauga rattlesnake (Sistrurus c. catenatus): insight from computer simulations

Michelle F. DiLeo, Jeremy D. Rouse, José A. Dávila & Stephen C. Lougheed
Understanding how gene flow shapes contemporary population structure requires the explicit consideration of landscape composition and configuration. New landscape genetic approaches allow us to link such heterogeneity to gene flow within and among populations. However, the attribution of cause is difficult when landscape features are spatially correlated, or when genetic patterns reflect past events. We use spatial Bayesian clustering and landscape resistance analysis to identify the landscape features that influence gene flow across two regional...

Data from: Contact zone dynamics during early stages of speciation in a chorus frog (Pseudacris crucifer)

Kathryn A. Stewart, James D. Austin, Kelly R. Zamudio & Stephen C. Lougheed
Characterizing the genetic and behavioural consequences of contact between previously geographically isolated lineages provides insights into the mechanisms underlying diversification and ultimately speciation. The spring peeper (Pseudacris crucifer) is a widespread Nearctic chorus frog with six divergent mitochondrial DNA (mtDNA) lineages, many of which came into secondary contact during the Holocene. We examined genetics, morphology, advertisement calls and female preference for two lineages that began diverging in allopatry in the Pliocene and now overlap in...

Data from: Extensive sampling of polar bears (Ursus maritimus) in the Northwest Passage (Canadian Arctic Archipelago) reveals population differentiation across multiple spatial and temporal scales

Leonardo Campagna, Peter J. Van Coeverden De Groot, Brenda L. Saunders, Stephen N. Atkinson, Diana S. Weber, Markus G. Dyck, Peter T. Boag & Stephen C. Lougheed
As global warming accelerates the melting of Arctic sea ice, polar bears (Ursus maritimus) must adapt to a rapidly changing landscape. This process will necessarily alter the species distribution together with population dynamics and structure. Detailed knowledge of these changes is crucial to delineating conservation priorities. Here, we sampled 361 polar bears from across the center of the Canadian Arctic Archipelago spanning the Gulf of Boothia (GB) and M'Clintock Channel (MC). We use DNA microsatellites...

Data from: Can alternative mating tactics facilitate introgression across a hybrid zone by circumventing female choice?

Kathryn A. Stewart, Cameron M. Hudson & Stephen C. Lougheed
Reproductive barriers and divergence in species’ mate recognition systems underlie major models of speciation. However, hybridization between divergent species is common, and classic mechanisms to explain permeable reproductive barriers rarely consider how an individual may attain reproductive success. Alternative mating tactics exist in various forms across animal taxa. Such tactics may allow poorer quality individuals to gain mating opportunities and facilitate introgression either through asymmetrical positive selection, or by circumventing female choice altogether in areas...

Size-dependent costs of migration: migrant bird species are subordinate to residents, but only at small body sizes

Paul Martin, Haley Kenyon & Leah Hayes
Migrant species are commonly thought to be poor competitors in aggressive interactions with resident species. However, no studies have tested if this relationship is widespread. Here we compare the behavioural dominance of closely-related species of migratory and non-migratory birds, testing if migrants are consistently subordinate to resident species in aggressive contests. We compiled published behavioural dominance data involving migrant and resident congeners, gathering additional data on the body mass and migratory distance of each species....

Knee extension moment arm variations relate to mechanical function in walking and running

Mitchell Wheatley
The patellofemoral joint plays a crucial mechanical role during walking and running. It increases the knee extensor mechanism’s moment arm and reduces required knee extension muscle forces to generate the extension moment that supports body weight, prevents knee buckling and propels the centre-of-mass. However, the mechanical implications of moment arm variation caused by patellofemoral and tibiofemoral motion remain unclear. We used a data-driven musculoskeletal model with a 12-degree-of freedom knee to simulate the knee extension...

Chronic selection for early reproductive phenology in an annual plant across a steep, elevational gradient of growing season length

David J. Ensing, Dylan M. D. H. Sora & Christopher G. Eckert
Colonisation along ubiquitous gradients of growing season length should require adaptation of phenological traits, driven by natural selection. While phenology often varies with season length and genetic differentiation in phenological traits sometimes seems adaptive, few studies test whether natural selection is responsible for these patterns. The annual plant Rhinanthus minor is genetically differentiated for phenology across a 1000-m elevational gradient of growing season length in the Canadian Rocky Mountains. We estimated phenotypic selection on five...

Structural brain network abnormalities and the probability of seizure recurrence after epilepsy surgery: supplementary material

Nishant Sinha, Yujiang Wang, Nádia Moreira Da Silva, Anna Miserocchi, Andrew McEvoy, Jane De Tisi, Sjoerd Vos, Gavin Winston, John Duncan & Peter Taylor
Objective: We assessed pre-operative structural brain networks and clinical characteristics of patients with drug resistant temporal lobe epilepsy (TLE) to identify correlates of post-surgical seizure recurrences. Methods: We examined data from 51 TLE patients who underwent anterior temporal lobe resection (ATLR) and 29 healthy controls. For each patient, using the preoperative structural, diffusion, and post-operative structural MRI, we generated two networks: ‘pre-surgery’ network and ‘surgically-spared’ network. Standardising these networks with respect to controls, we determined...

The extensibility of the plantar fascia influences the windlass mechanism during human running

Lauren Welte, Luke Kelly, Sarah Kessler, Daniel Lieberman, Susan D'Andrea, Glen Lichtwark & Michael Rainbow
The arch of the human foot is unique among hominins as it is compliant at ground-contact but sufficiently stiff to enable push-off. These behaviours are partly facilitated by the ligamentous plantar fascia whose role is central to two mechanisms. The ideal windlass mechanism assumes that the plantar fascia has a nearly constant length to directly couple toe dorsiflexion with a change in arch shape. However, the plantar fascia also stretches and then shortens throughout gait...

Phylogeography of the sea urchin genus Echinothrix.

Simon Coppard, Harilaos Lessios & Holly Jessop
The sea urchins Echinothrix calamaris and E. diadema have sympatric distributions throughout the Indo-Pacific. Diverse colour variation is reported in both species. To reconstruct the phylogeny of the genus and assess gene flow across the Indo-Pacific we sequenced mitochondrial 16S rDNA, ATPase-6, and ATPase-8, and nuclear 28S rDNA and the Calpain-7 intron. Our analyses revealed that E. diadema formed a single trans-Indo-Pacific clade, but E. calamaris contained three discreet clades. One clade was endemic to...

Climate oscillations drive millennial-scale changes in seabird colony size

Matthew Duda, Frédéric Cyr, Gregory Robertson, Neal Michelutti, Carsten Meyer-Jacob, April Hedd, William Montevecchi, Linda Kimpe, Jules Blais & John Smol
Seabird population size is intimately linked to the physical, chemical, and biological processes of the oceans. Yet, the overall effects of long-term changes in ocean dynamics on seabird colonies are difficult to quantify. Here, we used dated lake sediments to reconstruct ~10,000-years of seabird dynamics in the Northwest Atlantic to determine the influences of Holocene-scale climatic oscillations on colony size. On Baccalieu Island (Newfoundland and Labrador, Canada) – where the world’s largest colony of Leach’s...

Adoption Costs of Financial Innovation: Evidence from Italian ATM Cards

Kim Huynh, Philipp Schmidt-Dengler, Gregor W. Smith & Angelika Welte
The discrete choice to adopt a financial innovation affects a household’s exposure to inflation and transactions costs. We model this adoption decision as being subject to an unobserved cost. Estimating the cost requires a dynamic structural model, to which we apply a conditional choice simulation estimator. A novel feature of our method is that preference parameters are estimated separately, from the Euler equations of a shopping-time model, to aid statistical efficiency. We apply this method...

A Benchmark Data Set for Hydrogen Combustion

Akshaya Das, Christopher J. Stein, Farnaz Heidar-Zadeh, Luke Bertels, Meili Liu, Xingyi Guan, Mojtaba Haghighatlari, Jie Li, Oufan Zhang, Hongxia Hao, Itai Leven, Martin Head-Gordon & Teresa Head-Gordon

Data from: Plasticity versus evolutionary divergence: what causes habitat partitioning in urban-adapted birds?

Paul Martin, Kevin Burke & Frances Bonier
Habitat partitioning can facilitate the coexistence of closely related species, and often results from competitive interference inducing plastic shifts of subordinate species in response to aggressive, dominant species (plasticity), or the evolution of ecological differences in subordinate species that reduce their ability to occupy habitats where the dominant species occurs (evolutionary divergence). Evidence consistent with both plasticity and evolutionary divergence exist, but the relative contributions of each to habitat partitioning have been difficult to discern....

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