Scaling laws and fluctuations in the statistics of word frequencies

In this paper we combine statistical analysis of large text databases and simple stochastic models to explain the appearance of scaling laws in the statistics of word frequencies. Besides the sublinear scaling of the vocabulary size with database size (Heaps' law), here we report a new scaling of the fluctuations around this average (fluctuation scaling analysis). We explain both scaling laws by modeling the usage of words by simple stochastic processes in which the overall distribution of word-frequencies is fat tailed (Zipf's law) and the frequency of a single word is subject to fluctuations across documents (as in topic models). In this framework, the mean and the variance of the vocabulary size can be expressed as quenched averages, implying that: i) the inhomogeneous dissemination of words cause a reduction of the average vocabulary size in comparison to the homogeneous case, and ii) correlations in the co-occurrence of words lead to an increase in the variance and the vocabulary size becomes a non-self-averaging quantity. We address the implications of these observations to the measurement of lexical richness. We test our results in three large text databases (Google-ngram, Enlgish Wikipedia, and a collection of scientific articles).Comment: 19 pages, 4 figure

Tracing an Invasion Paradox across Scales: Patterns and Tests for the Effects of the Introduced Predatory Grouper, Roi (Cephalopholis argus) in Hawai‘i.

Ph.D. Thesis. University of Hawaiʻi at Mānoa 2017

Summing the strokes: energy economy in northern elephant seals during large-scale foraging migrations.

BackgroundThe energy requirements of free-ranging marine mammals are challenging to measure due to cryptic and far-ranging feeding habits, but are important to quantify given the potential impacts of high-level predators on ecosystems. Given their large body size and carnivorous lifestyle, we would predict that northern elephant seals (Mirounga angustirostris) have elevated field metabolic rates (FMRs) that require high prey intake rates, especially during pregnancy. Disturbance associated with climate change or human activity is predicted to further elevate energy requirements due to an increase in locomotor costs required to accommodate a reduction in prey or time available to forage. In this study, we determined the FMRs, total energy requirements, and energy budgets of adult, female northern elephant seals. We also examined the impact of increased locomotor costs on foraging success in this species.ResultsBody size, time spent at sea and reproductive status strongly influenced FMR. During the short foraging migration, FMR averaged 90.1 (SE = 1.7) kJ kg(-1)d(-1) - only 36 % greater than predicted basal metabolic rate. During the long migration, when seals were pregnant, FMRs averaged 69.4 (±3.0) kJ kg(-1)d(-1) - values approaching those predicted to be necessary to support basal metabolism in mammals of this size. Low FMRs in pregnant seals were driven by hypometabolism coupled with a positive feedback loop between improving body condition and reduced flipper stroking frequency. In contrast, three additional seals carrying large, non-streamlined instrumentation saw a four-fold increase in energy partitioned toward locomotion, resulting in elevated FMRs and only half the mass gain of normally-swimming study animals.ConclusionsThese results highlight the importance of keeping locomotion costs low for successful foraging in this species. In preparation for lactation and two fasting periods with high demands on energy reserves, migrating elephant seals utilize an economical foraging strategy whereby energy savings from reduced locomotion costs are shuttled towards somatic growth and fetal gestation. Remarkably, the energy requirements of this species, particularly during pregnancy, are 70-80 % lower than expected for mammalian carnivores, approaching or even falling below values predicted to be necessary to support basal metabolism in mammals of this size

Mapping the Dorsal Skin Pigmentation Patterns of Two Sympatric Populations of Ambystomatid Salamanders, \u3cem\u3eAmbystoma opacum\u3c/em\u3e and \u3cem\u3eA. maculatum\u3c/em\u3e from Northeast Tennessee.

Because of growing concern of habitat fragmentation and its adverse effects on salamander communities in Appalachian region, sympatric populations of ambystomatid salamanders A. opacum and A. maculatum were studied in Northeast Tennessee to address a number of questions: i) the extent of sexual size dimorphism (SSD) in both species, ii) what traits influence the dorsal skin pigmentation and how, iii) whether gender differences in developmental stability occur, and iv) the extent of phenotypic variation within each species. The findings of this study revealed SSD in both species of salamanders. The most parsimonious statistical model was developed that explained the influence of body mass, dorsal body area, and sex on development of dorsal white pigmentation in marbled salamanders. Data on asymmetry indicate that females are under more stress than males in marbled salamanders, while for spotted salamanders nonsignificant asymmetry is indicative of similar level of stress in both sexes. Data on coefficient of variation (CV) suggest stabilizing selection on optimal body size and mass in female marbled salamanders compared to males; however, for spotted salamanders CV indicates relatively similar selection pressure for body size and mass for both sexes

Seahorse aquaculture, biology and conservation: knowledge gaps and research opportunities

11 páginas, 6 figuras, 1 tablaSeahorses are currently experiencing an unprecedented level of anthropogenic pressure promoted by habitat destruction and increasing fishing effort to supply premium markets. This study provides an overview of the scientific literature on seahorses in the 21st century and critically discusses five major knowledge gaps and research opportunities to advance the state of the art on this research field. The average number of publications per year increased from 10 (2001–2002) to ∼40 (2001–2015), the majority addressing issues on seahorse ecology, biology, and aquaculture, with the most studied species being Hippocampus kuda, H. guttulatus, H. reidi, H. abdominalis, H. erectus, H. hippocampus, and H. trimaculatus. This study explores the opportunity of using seahorses as flagship species to foster mangrove conservation and decrease trawling fisheries. It also suggests that further scientific studies are needed to better understand and manage the populations of the most heavily traded seahorse species, as well as the need to monitor their vulnerability to emerging pollutants and climate change. Sustainable seahorse aquaculture can play an important role in seahorse conservation, as well as in the development of reliable traceability tools to fight the illegal trade of these highly priced organismsWe thank the São Paulo Research Foundation–FAPESP (grants nos. 2013/22260-6 and 2015/18050-0) and The National Council for Scientific and Technological Development–CNPq (grant nos. 441356/2014-1) for the financial support provided. Thanks also to FCT/MEC through national funds, and the cofunding by the FEDER, within the PT2020 Partnership Agreement and Compete 2020 for the financial support to CESAM (UID/AMB/50017/2013)Peer reviewe

Ecological interactions among important groundfishes in the Gulf of Alaska

Thesis (Ph.D.) University of Alaska Fairbanks, 2019Complex ecological interactions such as predation and competition play an important role in shaping the structure and function of marine communities. In fact, these processes can have greater impacts than those related to fishing. We assessed ecological interactions among economically important fishes in the Gulf of Alaska - a large marine ecosystem that has recently undergone considerable shifts in community composition. Specifically, we developed an index of predation for Walleye Pollock (Gadus chalcogrammus) to examine spatiotemporal changes in consumption, quantify portfolio effects, and better understand diversity-stability relationships within the demersal food web. We also evaluated the potential for competition between two important pollock predators, Arrowtooth Flounder (Atheresthes stomias) and Pacific Halibut (Hippoglossus stenolepis). We found highly variable predation intensity on Gulf of Alaska pollock. The combination of a single dominant predator and synchronous consumption dynamics indicated strong top-down control in the region. Spatial heterogeneity, however, may offset trophic instability at the basin scale. Assessments of resource partitioning provided little indication for competition between Arrowtooth Flounder and Pacific Halibut of similar lengths. Morphological differences between the two flatfish predators prompted an exploration into whether our conclusions about resource partitioning were dependent upon the size metric used. From this study, we found a relatively early onset of piscivory for Arrowtooth Flounder. Relationships between predator size and prey size also suggested gape limitation among Pacific Halibut sampled. Trophic niche separation was more pronounced for fishes with larger gapes, indicating greater potential for competition among smaller Arrowtooth Flounder and Pacific Halibut in Southeast Alaska. Reexamining basin-scale relationships between spatial and dietary overlap according to gape size would further elucidate the effects an increasing Arrowtooth Flounder population has had on changes in Pacific Halibut size-at-age. Results from this dissertation improve our understanding about the impacts of complex ecological interactions on population and community dynamics, and how those interactions may change in time, space, and under different environmental conditions.Pollock Conservation Cooperative Research Center (PCCRC; G00009488), Rasmuson Fisheries Research Cente

Networks in cognitive science

Networks of interconnected nodes have long played a key role in Cognitive Science, from artificial neural networks to spreading activation models of semantic memory. Recently, however, a new Network Science has been developed, providing insights into the emergence of global, system-scale properties in contexts as diverse as the Internet, metabolic reactions, and collaborations among scientists. Today, the inclusion of network theory into Cognitive Sciences, and the expansion of complex-systems science, promises to significantly change the way in which the organization and dynamics of cognitive and behavioral processes are understood. In this paper, we review recent contributions of network theory at different levels and domains within the Cognitive Sciences.Postprint (author's final draft

BIO-ECOLOGICAL AND ANATOMICAL ASPECTS OF THE EUROPEAN EEL ANGUILLA ANGUILLA (L. 1758)

Catadromous fish are considered important species for their ecological, economical, and cultural value. Because their complex life cycle, they are subjected to cumulative effects of anthropogenic threats that resulted in worldwide decline since the beginning of the 20th century. Among the most iconic catadromous species, the European eel Anguilla anguilla (L.) has aroused considerable interest since ancient times, though, to date, many aspects of its life cycle remain relatively unknown. A. anguilla showed a progressively decline since the 1970s. Starting from 2007, has been protected by the European Council Regulation 1100/2007, and successively classified as Critically Endangered (CR). Although conspicuous efforts have been conducted, to implement knowledge and identify possible solutions to preserve the future survivorship of A. anguilla, there is an urgent need to gain further insights into its life history. A review of the bibliography allowed me to obtain an updated state of the art of knowledge about the European eel life cycle, biology, ecology, allowing me to identify main topics that structured my thesis project. Topics have been developed with the general aim of providing a contribution to the implementation of the knowledge of the bio-ecology and anatomy of this species in relation to the various environmental and anthropic factors through a multidisciplinary approach that involved numerous sampling activities accompanied by complex data collection, laboratory experiments, and statistical analyses. First, I demonstrated the presence of synaptic development in the olfactory bulb, in terms of morphology and density of dendritic spines, that is shaped according to a pattern linked to the migratory life stages of the European eel (glass eels and silver eels). Second, I described the glass eels’ migration temporal peak for the first time in the central-western Mediterranean in relation to the effects of main environmental factors. I also identified a spatio-temporal variability between four sites in the western Mediterranean in terms of the peak of recruitment and the biometric and pigmentation patterns of glass eels. Moreover, I tested new floating traps as an alternative sampling method in three Sardinian estuaries to further deepen glass eels’ recruitment dynamics in Sardinia. Third, I analysed eels’ survival and growth performances during a rearing experiment with wild glass eels. I estimated recapture and growth rates on marked and unmarked farmed eels after restocking after a four-year study. Results suggest a good readjustment to the wild environment and demonstrated that this technique could represents a valid alternative restocking approach. Furthermore, I studied eels’ growth also in terms of otoliths’ shape differences. I found a distinct clustering among rivers and lagoons, with more rounded otoliths shapes in eels from rivers than lagoons, but with annual body growth quicker in lagoons than in rivers, showing that eel’s growth can differ according to habitat types. I fitted Von Bertalanffy’s growth curves for female and male eels from a Sardinian stream, that exhibited the already-known sexual dimorphism in growth parameters with higher values in females. Finally, I pinpointed an overall decrease in eels’ occurrence in the Sardinian river network because of dams’ building features and the time from their construction. Achieved results might have several implications beyond the regional interest and add new points from which to start further investigations that, over specific actions, may guide the implementation of new studies and appropriate monitoring programs. Findings highlighted also an urgent need for collaboration between the various stakeholders, researchers, decision-makers, authorities, professionals, and common people as an essential step to creating a sense of awareness on the criticalities that impact this species and the need to mitigate them

Remote Sensing of Savannas and Woodlands

Savannas and woodlands are one of the most challenging targets for remote sensing. This book provides a current snapshot of the geographical focus and application of the latest sensors and sensor combinations in savannas and woodlands. It includes feature articles on terrestrial laser scanning and on the application of remote sensing to characterization of vegetation dynamics in the Mato Grosso, Cerrado and Caatinga of Brazil. It also contains studies focussed on savannas in Europe, North America, Africa and Australia. It should be important reading for environmental practitioners and scientists globally who are concerned with the sustainability of the global savanna and woodland biome