A theoretical framework for multi-species range expansion in spatially heterogeneous landscapes

Range expansion is the spatial spread of a population into previously unoccupied regions. Understanding range expansion is important for the study and successful manipulation and management of ecosystems, with applications ranging from controlling bacterial biofilm formation in industrial and medical environments to large scale conservation programmes for species undergoing climate-change induced habitat disruption. During range expansion, species typically encounter competitors. Moreover, the environment into which expansion takes place is almost always heterogeneous when considered at the scale of the individual. Despite the ubiquitous nature of these features, the impact of competition and spatial landscape heterogeneities on range expansion remains understudied. In this paper we present a theoretical framework comprising two competing generic species undergoing range expansion and use it to investigate the impact of spatial landscape heterogeneities on range expansion with a particular focus on its effect on competition dynamics. We reveal that the area covered by range expansion during a fixed time interval is highly variable due to the fixed landscape heterogeneities. Moreover, we report significant variability in competitive outcome (relative abundance of a focal species) but determine that this is induced by low initial population densities, independent of landscape heterogeneities. We further show that both area covered by range expansion and competitive outcome can be accurately predicted by a Voronoi tessellation with respect to an appropriate metric, which only requires information on the spatial landscape and the response of each species to that landscape. Finally, we reveal that if species interact antagonistically during range expansion, the dominant mode of competition depends on the initial population density. Antagonistic actions determine competitive outcome if the initial population density is high, but competition for space is the dominant mode of competition if the initial population density is low.

How do outcome-based competitive relationships shape future risky cooperation?

There is growing evidence that cooperative behavior between individuals is regulated by their experience of previous interactions with others. However, it is unclear how a relationship that stems from the evaluation of outcomes from competitive interactions can affect subsequent cooperation between these individuals. To address this issue, we examined how participants cooperated with a partner having just competed with them. While competing, participants (N = 164) were randomly assigned to receive one of four types of outcome feedback regarding their performance (win vs. loss vs. uncertain vs. control). We found that both the experience of loss and of uncertainty as competitive outcomes exerted a negative impact on the extent to which participants then engaged in mutually cooperative behavior toward their opponents. Moreover, these effects operated in a context-dependent manner: they were only found when we manipulated the relational context to imply a high potential for incurring personal costs rather than imply no risk for incurring personal costs and mutual gains. Finally, our mediation analysis further revealed that the effect of the loss outcome was mediated by the intention of participants to cooperate and their level of interpersonal trust, while the effect of uncertain competitive outcome was mediated only by the extent to which participants intended to cooperate. This suggests the presence of distinct psychological processes underlying the effects of these two types of competitive outcome. Taken together, these finding offer novel insight into how risky cooperation may cascade from previous exposure to competitive settings.

Founder cell configuration drives competitive outcome within colony biofilms

Bacteria typically form dense communities called biofilms, where cells are embedded in a self-produced extracellular matrix. Competitive interactions between strains within the biofilm context are studied due to their potential applications in biological, medical, and industrial systems. Combining mathematical modelling with experimental assays, we reveal that the spatial structure and the competitive dynamics within biofilms are significantly affected by the location and density of founder cells. Using an isogenic pair of Bacillus subtilis strains, we show that the observed spatial structure and relative strain biomass in a mature biofilm can be mapped directly to the locations of founder cells. Moreover, we define a predictor of competitive outcome that accurately forecasts relative abundance of strains based solely on the founder cells' access to free space. Consequently, we reveal that variability of competitive outcome in biofilms inoculated at low founder density is a natural consequence of the random positioning of founding cells in the inoculum. Extending our study to non-isogenic strain pairs of B. subtilis, we show that even for strains with different antagonistic strengths, a race for space remains the dominant mode of competition in biofilms inoculated at low founder densities. Our results highlight the importance of spatial dynamics on competitive interactions within biofilms and hence to related applications.

The role of heterogenous environmental conditions in shaping the spatiotemporal distribution of competing Aedes mosquitoes in Panama: implications for the landscape of arboviral disease transmission

Monitoring the invasion process of the Asian tiger mosquito Aedes albopictus and its interaction with the contender Aedes aegypti, is critical to prevent and control the arthropod-borne viruses (i.e., Arboviruses) they transmit to humans. Generally, the superior ecological competitor Ae. albopictus displaces Ae. aegypti from most geographic areas, with the combining factors of biology and environment influencing the competitive outcome. Nonetheless, detailed studies asserting displacement come largely from sub-tropical areas, with relatively less effort being made in tropical environments, including no comprehensive research about Aedes biological interactions in Mesoamerica. Here, we examine contemporary and historical mosquito surveillance data to assess the role of shifting abiotic conditions in shaping the spatiotemporal distribution of competing Aedes species in the Republic of Panama. In accordance with prior studies, we show that Ae. albopictus has displaced Ae. aegypti under suboptimal wet tropical climate conditions and more vegetated environments within the southwestern Azuero Peninsula. Conversely, in the eastern Azuero Peninsula, Ae. aegypti persists with Ae. albopictus under optimal niche conditions in a dry and more seasonal tropical climate. While species displacement was stable over the course of two years, the presence of both species generally appears to fluctuate in tandem in areas of coexistence. Aedes albopictus was always more frequently found and abundant regardless of location and climatic season. The heterogenous environmental conditions of Panama shape the competitive outcome and micro-geographic distribution of Aedes mosquitoes, with potential consequences for the transmission dynamics of urban and sylvatic zoonotic diseases.

Competition of Two Host Species for a Single-Limited Resource Mediated by Parasites

In this paper we consider a mathematical model of two host species competing for a single -limited resource mediated by parasites. Each host population is divided into susceptible and infective population. We assume that species 1 has the lowest break-even concentration with respect to nutrient, when there is no parasite. Thus species 1 is a superior competitor that outcompetes species 2. When parasites present, the competitive outcome is determined by the contact rate of the superior competitor. We analyze the model by finding the conditions for the existence of various equilibria and doing their stability analysis. Two bifurcation diagrams are presented. The first one is in $\beta_1$-$\beta_2$ plane (See Figure 3) and the second one is in $R^{(0)}$-line (See Figure 4).

A Concrete Theory of Moligopoly

This chapter presents an empirical theory of moligopoly competition, in which big tech firms compete by a process of indirect entry. It begins by introducing each tech giant, namely, Facebook, Apple, Amazon, Netflix, Google, and Microsoft. The chapter then identifies six properties common to many of them: diversification, discontinuity, long termism, growth, exploration and discovery, and flexibility. All six properties work together toward a competitive outcome. Moreover, moligopoly competition appears to lead to a substantial allocation of resources to invention.