126 research outputs found
Foraging under conditions of short-term exploitative competition: The case of stock traders
Theory purports that animal foraging choices evolve to maximize returns, such
as net energy intake. Empirical research in both human and nonhuman animals
reveals that individuals often attend to the foraging choices of their
competitors while making their own foraging choices. Due to the complications
of gathering field data or constructing experiments, however, broad facts
relating theoretically optimal and empirically realized foraging choices are
only now emerging. Here, we analyze foraging choices of a cohort of
professional day traders who must choose between trading the same stock
multiple times in a row---patch exploitation---or switching to a different
stock---patch exploration---with potentially higher returns. We measure the
difference between a trader's resource intake and the competitors' expected
intake within a short period of time---a difference we call short-term
comparative returns. We find that traders' choices can be explained by foraging
heuristics that maximize their daily short-term comparative returns. However,
we find no one-best relationship between different trading choices and net
income intake. This suggests that traders' choices can be short-term win
oriented and, paradoxically, maybe maladaptive for absolute market returns
Estimating the tolerance of species to the effects of global environmental change
Global environmental change is affecting species distribution and their
interactions with other species. In particular, the main drivers of
environmental change strongly affect the strength of interspecific interactions
with considerable consequences to biodiversity. However, extrapolating the
effects observed on pair-wise interactions to entire ecological networks is
challenging. Here we propose a framework to estimate the tolerance to changes
in the strength of mutualistic interaction that species in mutualistic networks
can sustain before becoming extinct. We identify the scenarios where generalist
species can be the least tolerant. We show that the least tolerant species
across different scenarios do not appear to have uniquely common
characteristics. Species tolerance is extremely sensitive to the direction of
change in the strength of mutualistic interaction, as well as to the observed
mutualistic trade-offs between the number of partners and the strength of the
interactions.Comment: Nature Communications 4, Article number: 2350, (2013
How structurally stable are global socioeconomic systems?
The stability analysis of socioeconomic systems has been centered on
answering whether small perturbations when a system is in a given quantitative
state will push the system permanently to a different quantitative state.
However, typically the quantitative state of socioeconomic systems is subject
to constant change. Therefore, a key stability question that has been
under-investigated is how strong the conditions of a system itself can change
before the system moves to a qualitatively different behavior, i.e., how
structurally stable the systems is. Here, we introduce a framework to
investigate the structural stability of socioeconomic systems formed by the
network of interactions among agents competing for resources. We measure the
structural stability of the system as the range of conditions in the
distribution and availability of resources compatible with the qualitative
behavior in which all the constituent agents can be self-sustained across time.
To illustrate our framework, we study an empirical representation of the global
socioeconomic system formed by countries sharing and competing for
multinational companies used as proxy for resources. We demonstrate that the
structural stability of the system is inversely associated with the level of
competition and the level of heterogeneity in the distribution of resources.
Importantly, we show that the qualitative behavior of the observed global
socioeconomic system is highly sensitive to changes in the distribution of
resources. We believe this work provides a methodological basis to develop
sustainable strategies for socioeconomic systems subject to constantly changing
conditions
On the structural stability of mutualistic systems
In theoretical ecology, traditional studies based on dynamical stability and numerical simulations have not found a unified answer to the effect of network architecture on community persistence. Here, we introduce a mathematical framework based on the concept of structural stability to explain such a disparity of results. We investigated the range of conditions necessary for the stable coexistence of all species in mutualistic systems. We show that the apparently contradictory conclusions reached by previous studies arise as a consequence of overseeing either the necessary conditions for persistence or its dependence on model parameterization. We show that observed network architectures maximize the range of conditions for species coexistence. We discuss the applicability of structural stability to study other types of interspecific interactions
Common Organizing Mechanisms in Ecological and Socio-economic Networks
Previous work has shown that species interacting in an ecosystem and actors
transacting in an economic context may have notable similarities in behavior.
However, the specific mechanism that may underlie similarities in nature and
human systems has not been analyzed. Building on stochastic food-web models, we
propose a parsimonious bipartite-cooperation model that reproduces the key
features of mutualistic networks - degree distribution, nestedness and
modularity -- for both ecological networks and socio-economic networks. Our
analysis uses two diverse networks. Mutually-beneficial interactions between
plants and their pollinators, and cooperative economic exchanges between
designers and their contractors. We find that these mutualistic networks share
a key hierarchical ordering of their members, along with an exponential
constraint in the number and type of partners they can cooperate with. We use
our model to show that slight changes in the interaction constraints can
produce either extremely nested or random structures, revealing that these
constraints play a key role in the evolution of mutualistic networks. This
could also encourage a new systematic approach to study the functional and
structural properties of networks. The surprising correspondence across
mutualistic networks suggests their broadly representativeness and their
potential role in the productive organization of exchange systems, both
ecological and social.Comment: In F. Reed-Tsochas and N. Johnson (eds.) Complex Systems and
Interdisciplinary Sciences. London: World Scientific Publishing (in press
Tracking Traders' Understanding of the Market Using e-Communication Data
Tracking the volume of keywords in Internet searches, message boards, or
Tweets has provided an alternative for following or predicting associations
between popular interest or disease incidences. Here, we extend that research
by examining the role of e-communications among day traders and their
collective understanding of the market. Our study introduces a general method
that focuses on bundles of words that behave differently from daily
communication routines, and uses original data covering the content of instant
messages among all day traders at a trading firm over a 40-month period.
Analyses show that two word bundles convey traders' understanding of same day
market events and potential next day market events. We find that when market
volatility is high, traders' communications are dominated by same day events,
and when volatility is low, communications are dominated by next day events. We
show that the stronger the traders' attention to either same day or next day
events, the higher their collective trading performance. We conclude that
e-communication among traders is a product of mass collaboration over diverse
viewpoints that embodies unique information about their weak or strong
understanding of the market
Towards the integration of niche and network theories
The quest for understanding how species interactions modulate diversity has progressed by theoretical and empirical advances following niche and network theories. Yet, niche studies have been limited to describe coexistence within tropic levels despite incorporating information about multi-trophic interactions. Network approaches could address this limitation, but they have ignored the structure of species interactions within trophic levels. Here we call for the integration of niche and network theories to reach new frontiers of knowledge exploring how interactions within and across trophic levels promote species coexistence. This integration is possible due to the strong parallelisms in the historical development, ecological concepts, and associated mathematical tools of both theories. We provide a guideline to integrate this framework with observational and experimental studies
How structurally stable are global socioeconomic systems?
The stability analysis of socioeconomic systems has been centred on answering whether small perturbations when a system is in a given quantitative state will push the system permanently to a different quantitative state. However, typically the quantitative state of socioeconomic systems is subject to constant change. Therefore, a key stability question that has been under-investigated is how strongly the conditions of a system itself can change before the system moves to a qualitatively different behaviour, i.e. how structurally stable the systems is. Here, we introduce a framework to investigate the structural stability of socioeconomic systems formed by a network of interactions among agents competing for resources. We measure the structural stability of the system as the range of conditions in the distribution and availability of resources compatible with the qualitative behaviour in which all the constituent agents can be self-sustained across time. To illustrate our framework, we study an empirical representation of the global socioeconomic system formed by countries sharing and competing for multinational companies used as proxy for resources. We demonstrate that the structural stability of the system is inversely associated with the level of competition and the level of heterogeneity in the distribution of resources. Importantly, we show that the qualitative behaviour of the observed global socioeconomic system is highly sensitive to changes in the distribution of resources. We believe that this work provides a methodological basis to develop sustainable strategies for socioeconomic systems subject to constantly changing conditions
Multispecies coexistence in fragmented landscapes
Publisher Copyright: Copyright © 2022 the Author(s). Published by PNAS.Spatial dynamics have long been recognized as an important driver of biodiversity. However, our understanding of species’ coexistence under realistic landscape configurations has been limited by lack of adequate analytical tools. To fill this gap, we develop a spatially explicit metacommunity model of multiple competing species and derive analytical criteria for their coexistence in fragmented heterogeneous landscapes. Specifically, we propose measures of niche and fitness differences for metacommunities, which clarify how spatial dynamics and habitat configuration interact with local competition to determine coexistence of species. We parameterize our model with a Bayesian approach using a 36-y time-series dataset of three Daphnia species in a rockpool metacommunity covering >500 patches. Our results illustrate the emergence of interspecific variation in extinction and recolonization processes, including their dependencies on habitat size and environmental temperature. We find that such interspecific variation contributes to the coexistence of Daphnia species by reducing fitness differences and increasing niche differences. Additionally, our parameterized model allows separating the effects of habitat destruction and temperature change on species extinction. By integrating coexistence theory and metacommunity theory, our study provides platforms to increase our understanding of species’ coexistence in fragmented heterogeneous landscapes and the response of biodiversity to environmental changes.Peer reviewe
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