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The article presents the discussion on overview of the evolutionary ramifications of the relation between animal personality and the ideal free distribution (IFD). Topics include electronic supplementary material, DiNuzzo & Griffen showing some simulation results for a scenario with temporally varying patch quality; and optimal behaviour of a polymorphic population deviating considerably from the IFD of a monomorphic population.

Using targeted survey, excavation, and radiocarbon dating, we assess the extent to which human settlement patterns on California’s northern Channel Islands fit predictions arising from the ideal free distribution (IFD): (1) people first established and expanded permanent settlements in the regions ranked high for environmental resource suitability; (2) as population grew, they settled in progressively lower ranked habitats; and (3) changes in the archaeological record associated with high population levels such as increases in faunal diversity and evenness in high-ranked habitats are coinci- dent with the expansion to other areas. On Santa Rosa Island, the early permanent settlements were located in both high- and middle-ranked locations, with the most extensive settlement at the highest ranked locations and only isolated sites elsewhere. Settlement at a low-ranked habitat was confined to the late Holocene (after 3600 cal BP). Drought influenced the relative rank of different locations, which is an example of climate adding a temporal dimension to the model that episodically stimulated popu- lation movement and habitat abandonment. Because the IFD includes a wide range of cultural and environmental variables, it has the potential to be a central model for guiding archaeological analysis and targeted field research.

The standard model of a single population fragmented into two patches connected by migration, was first introduced in the 1970s by Freedman and Waltman, since generating long-term research interest, though its full analysis for arbitrary values of migration rate has only been completed relatively recently. Here, we present a model of two competing species in a two-patch habitat with migrations between patches. We derive equilibrium solutions of this model for three cases of migration rate resulting in isolated, well-mixed and semi-isolated habitats. We evaluate the full range of effects of habitat, life-history and migration parameters on population sizes. Finally, we add harvesting mortality and define conditions under which introduction of a no-harvesting (protected) area may lead to increased maximum sustainable yield. The results have applications in mixed fishery management and the design of wildlife protection zones, including marine protected areas (MPAs). • We consider a system of two competing populations with asymmetric migrations between two habitats. • We obtain equilibrium population sizes for zero, sufficiently small and infinite migration rates. • The coexistence condition for two competing species in a perfectly mixed habitat is derived. • Harvest mortality is added to the system and the maximum sustainable yield (MSY) is calculated. • The conditions under which a no-harvesting zone (e.g., marine protected area) can increase MSY are evaluated. [ABSTRACT FROM AUTHOR]

Major disturbances can temporarily remove factors that otherwise constrain population abundance and distribution. During such windows of relaxed top‐down and/or bottom‐up control, ungulate populations can grow rapidly, eventually leading to resource depletion and density‐dependent expansion into less‐preferred habitats. Although many studies have explored the demographic outcomes and ecological impacts of these processes, fewer have examined the individual‐level mechanisms by which they occur. We investigated these mechanisms in Gorongosa National Park, where the Mozambican Civil War devastated large‐mammal populations between 1977 and 1992. Gorongosa's recovery has been marked by proliferation of waterbuck (Kobus ellipsiprymnus), an historically marginal 200‐kg antelope species, which is now roughly 20‐fold more abundant than before the war. We show that after years of unrestricted population growth, waterbuck have depleted food availability in their historically preferred floodplain habitat and have increasingly expanded into historically avoided savanna habitat. This expansion was demographically skewed: mixed‐sex groups of prime‐age individuals remained more common in the floodplain, while bachelors, loners, and subadults populated the savanna. By coupling DNA metabarcoding and forage analysis, we show that waterbuck in these two habitats ate radically different diets, which were more digestible and protein‐rich in the floodplain than in savanna; thus, although individuals in both habitats achieved positive net energy balance, energetic performance was higher in the floodplain. Analysis of daily activity patterns from high‐resolution GPS‐telemetry, accelerometry, and animal‐borne video revealed that savanna waterbuck spent less time eating, perhaps to accommodate their tougher, lower‐quality diets. Waterbuck in savanna also had more ectoparasites than those in the floodplain. Thus, plasticity in foraging behavior and diet selection enabled savanna waterbuck to tolerate the costs of density‐dependent spillover, at least in the short term; however, the already poorer energetic performance of these individuals implies that savanna occupancy may become prohibitively costly as heterospecific competitors and predators continue to recover in Gorongosa. Our results suggest that behavior can provide a leading indicator of the onset of density‐dependent limitation and the likelihood of subsequent population decline, but that reliable inference hinges on understanding the mechanistic basis of observed behavioral shifts. [ABSTRACT FROM AUTHOR]

The wool carder bee Anthidium manicatum is one textbook example of resource defense polygyny among solitary bees, known for intense male–male competition, forced copulations, and the extreme form of interspecific territoriality toward other flower visitors. This mating system depends on the spatial structure of the defended resource and requires several adaptations in males. The allocation of patches with host plants as well as male body size and phenology was analyzed over 3 years in the diverse habitat of a botanical garden. Anthidium manicatum males searched in groups up to 12 individuals a wide diversity of patches with various food plants of foraging females. Territories were established in small high-quality patches only. Males abandoned aggressive and territorial behavior in large patches. Available patches were occupied by males of the various body size fractions independently of each other according to patch profitability. The higher competitive weight of large males in small patches compared to spacious ones was balanced by an opposing correlation of patch profitability. Although the mating system in A. manicatum is clearly a resource defense polygyny, males were found to be plastic in their behavior, and territoriality was not consistently observed. Mate acquiring tactics, be they territory holder (bourgeois), sneaker, floater, or scrambler for mating, can be considered to be different behavioral phenotypes within one environmentally sensitive conditional strategy. Significance statement: Territoriality is a rare and derived pattern in solitary bee mating behavior. In most cases of territoriality, males defend rendezvous places to meet freshly emerged, virgin females. While this type of mating behavior fits still into the framework of ancestral monandry of aculeate Hymenoptera, the continually polyandric resource defense polygyny found in the genus Anthidium is highly derived. Males occupy flower resources exploited for larval provisions and extort copulations from provisioning nesting females. Territoriality in Anthidium does not lead to a monopolization of females, the exclusion of many competitors from reproduction, and a reduction of sperm competition as is typical for resource-based mating systems. Contrary, Anthidium is a highly promiscuous species and both males and females are lifelong engaged in copulations with multiple mates. Also, the allocation of the resource fundamental to the defense polygyny was found to be more fairly balanced than expected. This study diversifies the mating system of anthidiine bees and demonstrates unusually high plasticity in the resource allocation of a territorial species. [ABSTRACT FROM AUTHOR]

This study is an application of the ideal free distribution (IFD) model to understand settlement patterns during the Mauretanian and Roman periods in northwest Morocco. We use proxies for potential agricultural productivity and distance from a viable harbor for each of the locations of known settlement sites. There is a clear relationship between the distance from harbors and habitat suitability, with sites that were established earliest all on or close to a point of access to the ocean. This is consistent with a focus on maritime trade and a connection with the Mediterranean Sea. Agricultural potential is also an important factor influencing settlement, although to a lesser extent, with earlier, low-density settlement more focused on trade potential. Consistent with predictions of the IFD, there is an expansion through time to progressively lower ranked habitats, with persistent settlement at the highest ranked habitats, including at Lixus, which is generally considered to be the earliest city in northwest Africa. During the Roman period, there is a focus of interior settlement near Volubilis. Subsidiary sites likely benefit from their proximity to this important political site, despite their relatively low rank within the IFD, perhaps reflecting patterns consistent with an ideal despotic distribution. This study demonstrates how the IFD can be used in a simple context with limited available survey data to assess the important environmental variables influencing settlement decisions. It has broad implications for understanding the formation of urban centers prior to and during the Roman period. [ABSTRACT FROM AUTHOR]

Birds exhibit a remarkable array of seasonal migrations. Despite much research describing migratory behaviour, the underlying forces driving how a species' breeding and wintering populations redistribute each year, that is, migratory connectivity, remain largely unknown. Here, we test the hypothesis that birds migrate in a way that minimises energy expenditure while considering intraspecific competition for energy acquisition, by developing a modelling framework that simulates an optimal redistribution of individuals between breeding and wintering areas. Using 25 species across the Americas, we find that the model accurately predicts empirical migration patterns, and thus offers a general explanation for migratory connectivity based on first ecological and energetic principles. Our model provides a strong basis for exploring additional processes underlying the ecology and evolution of migration, but also a framework for predicting how migration impacts local adaptation across seasons and how environmental change may affect population dynamics in migratory species. [ABSTRACT FROM AUTHOR]

Ecological fitness is the ability of individuals in a population to survive and reproduce. Individuals with increased fitness are better equipped to withstand the selective pressures of their environments. This paradigm pertains to all organismal life as we know it; however, it is also becoming increasingly clear that within multicellular organisms exist highly complex, competitive, and cooperative populations of cells under many of the same ecological and evolutionary constraints as populations of individuals in nature. In this review I discuss the parallels between populations of cancer cells and populations of individuals in the wild, highlighting how individuals in either context are constrained by their environments to converge on a small number of critical phenotypes to ensure survival and future reproductive success. I argue that the hallmarks of cancer can be distilled into key phenotypes necessary for cancer cell fitness: survival and reproduction. I posit that for therapeutic strategies to be maximally beneficial, they should seek to subvert these ecologically driven phenotypic responses.

Individuals that disperse long distances from their natal site must select breeding patches with no prior knowledge of patch suitability. Despite decades of theoretical studies examining which cues dispersing individuals should use to select breeding patches, few empirical studies have tested the predictions of these theories at spatial scales relevant to long‐distance dispersal in wild animal populations. Here, we use a novel assignment model based on multiple intrinsic markers to quantify natal dispersal distances of Wood Thrush (Hylocichla mustelina) breeding in forest fragments. We show that long‐distance natal dispersal in this species is more frequent than commonly assumed for songbirds and that habitat selection by these individuals is driven by density‐dependence and patch quality but not the amount of habitat surrounding breeding patches. These results represent an important contribution to understanding habitat selection by dispersing individuals, especially with regards to long‐distance dispersal. [ABSTRACT FROM AUTHOR]

Root competition is a key factor determining plant performance, community structure and ecosystem productivity. To adequately estimate the extent of root proliferation of plants in response to neighbours independently of nutrient availability, one should use a set-up that can simultaneously control for both nutrient concentration and soil volume at plant individual level. With a mesh-divider design, which was suggested as a promising solution for this problem, we conducted two intraspecific root competition experiments: one with soybean (Glycine max) and the other with sunflower (Helianthus annuus). We found no response of root growth or biomass allocation to intraspecific neighbours, i.e. an 'ideal free distribution' (IFD) norm, in soybean; and even a reduced growth as a negative response in sunflower. These responses are all inconsistent with the hypothesis that plants should produce more roots even at the expense of reduced fitness in response to neighbours, i.e. root over-proliferation. Our results suggest that neighbour-induced root over-proliferation is not a ubiquitous feature in plants. By integrating the findings with results from other soybean studies, we conclude that for some species this response could be a genotype-dependent response as a result of natural or artificial selection, or a context-dependent response so that plants can switch from root over-proliferation to IFD depending on the environment of competition. We also critically discuss whether the mesh-divider design is an ideal solution for root competition experiments. [ABSTRACT FROM AUTHOR]

A population is said to have an ideal free distribution in a spatially heterogeneous but temporally constant environment if each of its members has chosen a fixed spatial location in a way that optimizes its individual fitness, allowing for the effects of crowding. In this paper, we extend the idea of individual fitness associated with a specific location in space to account for the full path that an individual organism takes in space and time over a periodic cycle, and we extend the mathematical formulation of an ideal free distribution to general time periodic environments. We find that, as in many other cases, populations using dispersal strategies that can produce a generalized ideal free distribution have a competitive advantage relative to populations using dispersal strategies that cannot do so. A sharp criterion on the environmental functions is found to be necessary and sufficient for such ideal free distribution to be feasible. In the case the criterion is met, we show the existence of dispersal strategies that can be identified as producing a time-periodic version of an ideal free distribution, and such strategies are evolutionarily steady and are neighborhood invaders from the viewpoint of adaptive dynamics. Our results extend previous works in which the environments are either temporally constant, or temporally periodic but the total carrying capacity is temporally constant. [ABSTRACT FROM AUTHOR]

The concept of an ideal free distribution (IFD) is analyzed for the predator–prey system in an inhomogeneous ring-shaped habitat. Diffusion–reaction–advection equations were used to model multifactorial taxis with regard to various laws of prey growth. Relationships were established for the parameters at which the IFD occurs. Transformation of solutions was studied for the case where the parameters deviate from the IFD conditions and the origin of auto-oscillating regimes was considered. [ABSTRACT FROM AUTHOR]

1. Understanding the distribution of organisms is a central issue in ecology. Some animal densities are directly determined by resource availability(i.e. the ideal free distribution model, IFD). Hence, animals freely occupy the available patches so that the payoff is ideally maximised according to resource exploitation and competition. Based on its assumptions, tests of the IFD should be made with animals presenting high motility and sensitivity to specific habitat characteristics. 2. This study demonstrates how traits from the plant community influence the distribution of two cobweb spiders, Helvibis longicauda and Chrysso intervales, on a forest understory. 3. Spider abundance was positively correlated to the availability of broadleaves (i.e. suitable sites) along patches. They show high topophilia (i.e. preferences based on microhabitat structural characteristics) for roof‐like leaves, which provide shelter to build webs underneath. Alternatively, higher numbers of pinnate fern fronds, a trait that is unsuitable to support the three‐dimensional webs of those species, translated to decreased abundance. Numbers of suitable and unsuitable sites were negatively correlated, indicating that their proportion on patches drives spider abundance. Finally, spider abundance along 22 suitable plant species was influenced by the number of microhabitats provided per species rather than by their phylogenetic identities. 4. We corroborate the IFD, demonstrating that simple consumer–resource relationships may occur on complex/multi‐species environments, such as forests. Dispersion and topophilic microhabitat selection may be driven by substrate availability and competition. Importantly, we provide insights based on the whole plant community, while previous evidence was limited to a single or a few species. [ABSTRACT FROM AUTHOR]

The ideal free distribution theory predicts that mobile species distribute themselves among habitat patches so as to optimize their fitness. Changes in land use alter the quality of habitat patches and thereby affect the distribution of species. Following the loss of native habitat, habitat specialists are expected to move to patches where native habitat still remains in order to survive. Competition for resources in habitat remnants should consequently increase. As generalists are able to use other habitats, generalists are expected to gradually disappear in remnants in order to avoid increasing competition with specialists. Here, we test these predictions by studying the response of habitat specialist and generalist birds to land-use change in Brazil's southern grasslands. Using a space-for-time substitution approach, we surveyed bird communities in native grassland sites (~4 ha) in 31 regions (10 × 10 km) with differing levels of conversion to agriculture (1–94%). We found a higher abundance of specialists in native grassland patches with increasing agricultural cover in the region, while the total number of individuals in remnants remained constant. At the same time, the share of generalists in total abundance and total species richness decreased. To gain insights into whether these patterns could be driven by shifts in competition, we tested whether generalists that continued to co-occur with specialists in remnants, had less dietary overlap with specialists. As a consequence of community composition in remnants, a higher proportion of generalists were omnivorous and the average generalist species fed less on seeds, whereas the average specialist species fed more on seeds when agricultural cover was high in the region. Our results, therefore, support predictions of the ideal free distribution theory. Specialists that are assumed to have a low survivorship outside of their specialized habitat, distribute to remnants of this habitat when it is converted elsewhere, while generalists, being able to survive in other habitats, disappear gradually in remnants. Such a process could partly explain the segregation of habitat specialist and generalist birds observed in many agricultural landscapes. Finally, our results suggest that native habitat remnants can be important temporary refugia for specialists.

An animal's movement rate (mobility) and its ability to perceive fitness gradients (fitness sensitivity) determine how well it can exploit resources. Previous models have examined mobility and fitness sensitivity separately and found that mobility, modelled as random movement, prevents animals from staying in high-quality patches, leading to a departure from an ideal free distribution (IFD). However, empirical work shows that animals with higher mobility can more effectively collect environmental information and better sense patch quality, especially when the environment is frequently changed by human activities. Here, we model, for the first time, this positive correlation between mobility and fitness sensitivity and measure its consequences for the populations of a consumer and its resource. In the absence of consumer demography, mobility alone had no effect on system equilibria, but a positive correlation between mobility and fitness sensitivity could produce an IFD. In the presence of consumer demography, lower levels of mobility prevented the system from approaching an IFD due to the mixing of consumers between patches. However, when positively correlated with fitness sensitivity, high mobility led to an IFD. Our study demonstrates that the expected covariation of animal movement attributes can drive broadly theorized consumer–resource patterns across space and time and could underlie the role of consumers in driving spatial heterogeneity in resource abundance.

The ideal free distribution (IFD) predicts that organisms will disperse to sites that maximize their fitness based on availability of resources. Habitat heterogeneity underlies resource variation and influences spatial variation in demography and the distribution of populations. We relate nest site productivity at multiple scales measured over a decade to habitat quality in a box-nesting population of Forpus passerinus (green-rumped parrotlets) in Venezuela to examine critical IFD assumptions. Variation in reproductive success at the local population and neighborhood scales had a much larger influence on productivity (fledglings per nest box per year) than nest site or female identity. Habitat features were reliable cues of nest site quality. Nest sites with less vegetative cover produced greater numbers of fledglings than sites with more cover. However, there was also a competitive cost to nesting in high-quality, low-vegetative cover nest boxes, as these sites experienced the most infanticide events. In the lowland local population, water depth and cover surrounding nest sites were related with F. passerinus productivity. Low vegetative cover and deeper water were associated with lower predation rates, suggesting that predation could be a primary factor driving habitat selection patterns. Parrotlets also demonstrated directional dispersal. Pairs that changed nest sites were more likely to disperse from poor-quality nest sites to high-quality nest sites rather than vice versa, and juveniles were more likely to disperse to, or remain in, the more productive of the two local populations. Parrotlets exhibited three characteristics fundamental to the IFD: habitat heterogeneity within and between local populations, reliable habitat cues to productivity, and active dispersal to sites of higher fitness.

In many choice environments, risks and rewards—or probabilities and payoffs—seem tightly coupled such that high payoffs only occur with low probabilities. An adaptive mind can exploit this association by, for instance, using a potential reward's size to infer the probability of obtaining it. However, a mind can only adapt to and exploit an environmental structure if it is ecologically reliable, that is if it is frequent and recurrent. We develop the competitive risk–reward ecology theory (CET) that establishes how the ecology of competition can make the association of high rewards with low probabilities ubiquitous. This association occurs because of what is known as the ideal free distribution (IFD) principle. The IFD states that competitors in a landscape of resource patches distribute themselves proportionally to the gross total amount of resources in the patches. CET shows how this principle implies a risk–reward structure: an inverse relationship between probabilities and payoffs. It also identifies boundary conditions for the risk–reward structure, including heterogeneity of resources, computational limits of competitors, and scarcity of resources. Finally, a set of empirical studies (N = 1,255) demonstrate that people's beliefs map onto properties predicted by CET and change as a function of the environment. In sum, grounding people's inferences in CET demonstrates how the behaviors of a boundedly rational mind can be better predicted once accounts of the mind and the environment are fused. [ABSTRACT FROM AUTHOR]

It is well known that movement strategies in ecology and in economics can make the difference between extinction and persistence. We present a unifying model for the dynamics of ecological populations and street vendors, which are an important part of many informal economies. We analyze this model to study the effects of directed movement of populations subject to strong Allee effect. We begin with the study of the existence of equilibrium solutions subject to homogeneous Dirichlet or no-flux boundary conditions. Next, we study the evolution problem and show that if the directed movement effect is small, the solutions behave like those of the classical reaction-diffusion equation with bistable growth pattern. We present numerical simulations, which show that directed movement can help overcome a strong Allee effect and provide some partial analytical results in this direction. We conclude by making a connection to the ideal free distribution and analyze what happens under competition, finding that an ideal free distribution strategy is a local neighborhood invader. [ABSTRACT FROM AUTHOR]

When foraging and competing for below‐ground resources, plants have to coordinate the behaviour of thousands of root tips in a manner similar to that of eusocial animal colonies. While well described in animals, we know little about the spatial behaviour of plants, particularly at the level of individual roots.Here, we employed statistical methods previously used to describe animal ranging behaviour to examine root system overlap and the efficiency of root positioning in eight grassland species grown in monocultures and mixtures along a gradient of neighbour densities.Species varied widely in their ability to distribute roots efficiently, with the majority of species showing significant root aggregation at very fine spatial scales. Extensive root system overlap was observed in species mixtures, indicating a lack of territoriality at the level of whole root systems. However, with increasing density of competitors, several species withdrew roots from the periphery of foraging ranges and increased intraplant root aggregation in the remaining area, which may indicate consolidation of foraging areas under competitive pressure.Several species exhibited responses consistent with resource contest in species mixtures where encounters with competitors' roots triggered increased root aggregation at the expense of foraging efficiency. Such responses only occurred in mixtures of species with comparable competitive abilities but were absent in asymmetric species combinations.Synthesis. Combining fine‐scale measurement of plant root distributions with spatial statistics yields new insights into plant behavioural strategies with significant potential to impact resource foraging efficiency and productivity. [ABSTRACT FROM AUTHOR]

Some plants respond to both neighbours and nutrient levels below‐ground independently, while others respond only to nutrients. These responses have important ecological implications, but debate about the appropriate control treatments used in experiments has led many to debate results.When plants ignore neighbours, and only respond to nutrient levels this is sometimes called an ideal‐free distribution (IFD). When individual plants respond to neighbours by increasing root production to pre‐empt the uptake of neighbours, and do so at the expense of reproduction, this has become known as a tragedy of the commons (TOC). Here, I describe how the history of competition experiments has largely been a history of experiments that only control two of three critical variables: (a) total nutrients per plant; (b) soil nutrient concentration and (c) pot volume. These confounding effects are the source of debate about results.In one study, split‐root pea plants were grown with and without a below‐ground neighbour at many pot volumes with equal total nutrients per‐plant. The researchers explicitly argued that plant growth responses would not be affected by the concentration of nutrients in soil, and therefore they explicitly confounded soil nutrient concentration with neighbour presence. Here, I reanalyse a subset of their data, controlling for soil nutrient concentration, but confounding pot volume with neighbour presence.When I controlled for soil nutrient concentration, the presence of a below‐ground neighbour had no effects on plant size, or allocation, and the effects of volume also disappeared. The reanalysis suggests that the behaviour of peas in this study was consistent with an IFD model, and that the previously reported volume and neighbour responses may have been due to the confounding of nutrient concentration.The results of the study in question depend very much on whether one does analyses that control for pot volume or whether one does analyses that control for soil nutrient concentration. Ultimately, these analyses lead to two different interpretations of the data. New experimental designs are emerging that fully control pot volume and nutrients across competition treatment, and I discuss possible paths forward in this ongoing debate. [ABSTRACT FROM AUTHOR]

Population dynamics are shaped by species interactions with resources, competitors, enemies, and environmental fluctuations that alter the strength of these interactions. We used a food web approach to investigate the population dynamics of an abundant Arctic mosquito species, Aedes nigripes (Diptera: Culicidae). Specifically, we evaluated the importance of bottom‐up variation in aquatic biofilms (food) and top‐down predation from diving beetles (Colymbetes dolabratus, Coleoptera: Dytiscidae) on mosquito population performance. In spring 2018, we tracked mosquito and predator populations across eight ponds in western Greenland, measured biofilm productivity with standardized samplers, and estimated grazing pressure by invertebrate consumers with an in situ exclosure experiment. We also assessed the quality of biofilms as nutrition for mosquito larvae and evaluated pond attributes that might influence biofilm productivity and food quality. Our results indicated that mosquito population dynamics were more related to resource quality and intraspecific competition than to the density of predaceous diving beetles. Ponds with better quality biofilm tended to have more hatching larvae and those populations experienced higher per capita mortality. This aggregation of larvae in what would otherwise be the best mosquito ponds was enough to produce relatively low fitness. Thus, the landscape would support more mosquitoes if they instead distributed themselves to match predictions of the ideal free distribution. Although mortality rates were highest in ponds with the highest initial densities, the increased mortality was not generally enough to compensate for initial abundance, and 78% of the variation in the density of mosquitoes emerging from ponds was explained by the initial number of larvae in a pond. Resource quality was a strong predictor of consumer abundance, yet there was no evidence that biofilm grazing pressure was greater in ponds where mosquito density was higher. Collectively, our results suggest that mosquito ponds in western Greenland are a mosaic of source and pseudo‐sink populations structured by oviposition tendencies, biofilm resource quality, and density‐dependent larval mortality. [ABSTRACT FROM AUTHOR]

Variation in social environment can mitigate risks and rewards associated with occupying a particular patch. We aim to integrate Ideal Free Distribution (IFD) and Geometry of the Selfish Herd (GSH) to address an apparent conflict in their predictions of equal mean fitness between patches (IFD) and declining fitness benefits within a patch (GSH). We tested these hypotheses in a socio‐spatial context using individual caribou that were aggregated or disaggregated during calving and varied in their annual reproductive success (ARS). We then tested individual consistency of these spatial tactics. We reveal that two socio‐spatial tactics accorded similar mean ARS (IFD); however, ARS for aggregated individuals declined near the periphery (GSH). Individuals near the aggregation periphery exhibited flexibility, whereas others were consistent. The integration of classical theories through a contemporary lens of consistent individual differences provides evidence for an integrated GSH and IFD strategy that may represent an evolutionary stable state. [ABSTRACT FROM AUTHOR]

Density‐dependent competition for food reduces vital rates, with juvenile survival often the first to decline. A clear prediction of food‐based, density‐dependent competition for large herbivores is decreasing juvenile survival with increasing density. However, competition for enemy‐free space could also be a significant mechanism for density dependence in territorial species. How juvenile survival is predicted to change across density depends critically on the nature of predator–prey dynamics and spatial overlap among predator and prey, especially in multiple‐predator systems. Here, we used a management experiment that reduced densities of a generalist predator, coyotes, and specialist predator, mountain lions, over a 5‐year period to test for spatial density dependence mediated by predation on juvenile mule deer in Idaho, USA. We tested the spatial density‐dependence hypothesis by tracking the fate of 251 juvenile mule deer, estimating cause‐specific mortality, and testing responses to changes in deer density and predator abundance. Overall juvenile mortality did not increase with deer density, but generalist coyote‐caused mortality did, but not when coyote density was reduced experimentally. Mountain lion‐caused mortality did not change with deer density in the reference area in contradiction of the food‐based competition hypothesis, but declined in the treatment area, opposite to the pattern of coyotes. These observations clearly reject the food‐based density‐dependence hypothesis for juvenile mule deer. Instead, our results provide support for the spatial density‐dependence hypothesis that competition for enemy‐free space increases predation by generalist predators on juvenile large herbivores. [ABSTRACT FROM AUTHOR]

In the mid-1950s Western Desert of Australia, Aboriginal populations were in decline as families left for ration depots, cattle stations, and mission settlements. In the context of reduced population density, an ideal free-distribution model predicts landscape use should contract to the most productive habitats, and people should avoid areas that show more signs of extensive prior use. However, ecological or social facilitation due to Allee effects (positive density dependence) would predict that the intensity of past habitat use should correlate positively with habitat use. We analyzed fire footprints and fire mosaics from the accumulation of several years of landscape use visible on a 35,300-km² mosaic of aerial photographs covering much of contemporary Indigenous Martu Native Title Lands imaged between May and August 1953. Structural equation modeling revealed that, consistent with an Allee ideal free distribution, there was a positive relationship between the extent of fire mosaics and the intensity of recent use, and this was consistent across habitats regardless of their quality. Fire mosaics build up in regions with low cost of access to water, high intrinsic food availability, and good access to trade opportunities; these mosaics (constrained by water access during the winter) then draw people back in subsequent years or seasons, largely independent of intrinsic habitat quality. Our results suggest that the positive feedback effects of landscape burning can substantially change the way people value landscapes, affecting mobility and settlement by increasing sedentism and local population density. [ABSTRACT FROM AUTHOR]

Spatial distribution and habitat selection are integral to the study of animal ecology. Habitat selection may optimize the fitness of individuals. Hutchinsonian niche theory posits the fundamental niche of species would support the persistence or growth of populations. Although niche‐based species distribution models (SDMs) and habitat suitability models (HSMs) such as maximum entropy (Maxent) have demonstrated fair to excellent predictive power, few studies have linked the prediction of HSMs to demographic rates. We aimed to test the prediction of Hutchinsonian niche theory that habitat suitability (i.e., likelihood of occurrence) would be positively related to survival of American beaver (Castor canadensis), a North American semi‐aquatic, herbivorous, habitat generalist. We also tested the prediction of ideal free distribution that animal fitness, or its surrogate, is independent of habitat suitability at the equilibrium. We estimated beaver monthly survival probability using the Barker model and radio telemetry data collected in northern Alabama, United States from January 2011 to April 2012. A habitat suitability map was generated with Maxent for the entire study site using landscape variables derived from the 2011 National Land Cover Database (30‐m resolution). We found an inverse relationship between habitat suitability index and beaver survival, contradicting the predictions of niche theory and ideal free distribution. Furthermore, four landscape variables selected by American beaver did not predict survival. The beaver population on our study site has been established for 20 or more years and, subsequently, may be approaching or have reached the carrying capacity. Maxent‐predicted increases in habitat use and subsequent intraspecific competition may have reduced beaver survival. Habitat suitability‐fitness relationships may be complex and, in part, contingent upon local animal abundance. Future studies of mechanistic SDMs incorporating local abundance and demographic rates are needed. [ABSTRACT FROM AUTHOR]

Balanced harvesting (BH)—the idea of harvesting all species and sizes in proportion to their production rate—has been a topic of recent debate. Developed world fisheries tend to fish more selectively, concentrating on certain species and sizes preferred in the market. However, fishing patterns in some developing countries, with a range of different fishing gears and more generalist markets, more closely resemble BH. The BH debate therefore hinges on whether selective fisheries should become more balanced, whether unselective fisheries should do the opposite, both, or neither. In this study, we use simple and general analytical theory to describe the ideal free distribution that should emerge in unmanaged fisheries, and we show that this ideal free distribution should approximately produce BH only when prices, catchabilities, and fishing costs are similar across species and sizes. We then derive general properties of yield and profit maxima subject to conservation constraints. We find that BH is unlikely to be optimal in any fishery but may be closer to optimal in fisheries in which it emerges without management. Thus, BH may be more useful as a heuristic for understanding differences between fisheries in locally appropriate management than as an exact management strategy. [ABSTRACT FROM AUTHOR]

Aim: As a response of pastoralists to climate change, nomadic migration deeply shaped Chinese history during the imperial era. Existing research on climate‐driven nomadic migration is conducted mainly on a national–continental scale. To advance the current work, we aim to resolve migratory movements at a provincial–regional scale using a large and long‐term historical dataset as a first attempt. The spatio‐temporal features of nomadic migration under climatic effects, specifically precipitation, are analysed in the theoretical context of behavioural ecology. Location: China. Time: Imperial era (220 BC–1910 AD). Study subject: Nomadic pastoralist minorities in imperial China. Methods: We frame the analysis using an ideal free distribution model. A total of 1,842 historical location records of pastoralist immigration are empirically examined. Precipitation anomalies and nomadic migration are statistically assessed with nonparametric and Poisson regression methods, and temporal interdependencies among provincial–regional migratory movements are explored with a vector autoregressive model. Results: We divide imperial China into six regions according to statistical results and geographic factors. Overall, decreased precipitation and drought provoked pastoralist migrations in a north‐to‐south direction. Northern nomads, with an apparent preference for central China as a major destination, triggered the most conflicts with resident agriculturalists. Nomads originating from the Tibetan minority regions moved north‐eastward into Qinghai Province as their main destination. Main conclusions: Long‐term regional patterns of pastoralist migration are closely associated with drought‐induced ecological change in imperial China. Climate‐driven dynamics assessed with long‐term historical data facilitate the understanding of climate–ecology–society interactions in behavioural ecology and macroecology. Moreover, findings from imperial China may imply that cultural acceptance and communications could avoid conflicts between immigrants and original residents when facing mass migration, an issue of growing contemporary urgency in many parts of the world. [ABSTRACT FROM AUTHOR]

The ideal free distribution (IFD) theory, which predicts that a population of individuals will match the distribution of a patchily distributed resource, is widely used in ecology to describe the spatial distribution of animals. While many studies have shown general support of its habitat matching prediction, others have described a systematic pattern of undermatching, where too many animals feed at patches with fewer resources, and too few animals feed in richer patches. These results have been attributed to deviations from several of the assumptions of the IFD. One possible variable, the cost of travelling between patches, has received little attention. Here, we investigated the impact on resource matching when travel costs were manipulated in a simple laboratory experiment involving two continuous input patches. This experiment allowed us to control for extraneous variables and decouple time costs from energetic costs of travel. Two experiments examined the impact of varying travel costs on movement rates between foraging patches and how these travel costs impact conformity to the IFD. Our data demonstrated that there was less movement between patches and greater discrepancies from the IFD predictions as the cost of travel increased. [ABSTRACT FROM AUTHOR]

We study the evolutionary stability of dispersal strategies, including but not limited to those that can produce ideal free population distributions (that is, distributions where all individuals have equal fitness and there is no net movement of individuals at equilibrium). The environment is assumed to be variable in space but constant in time. We assume that there is a separation of times scales, so that dispersal occurs on a fast timescale, evolution occurs on a slow timescale, and population dynamics and interactions occur on an intermediate timescale. Starting with advection–diffusion models for dispersal without population dynamics, we use the large time limits of profiles for population distributions together with the distribution of resources in the environment to calculate growth and interaction coefficients in logistic and Lotka–Volterra ordinary differential equations describing population dynamics. We then use a pairwise invasibility analysis approach motivated by adaptive dynamics to study the evolutionary and/or convergence stability of strategies determined by various assumptions about the advection and diffusion terms in the original advection–diffusion dispersal models. Among other results we find that those strategies which can produce an ideal free distribution are evolutionarily stable. [ABSTRACT FROM AUTHOR]

Food acquisition by most organisms is a complex ecological process that involves benefits and risks, affecting organism development and interspecific interactions. The evaluation of habitat selection, food consumption, and predator avoidance is pivotal for understanding the ecological process affecting life history traits and the role of species on communities and ecosystems. In a microcosm experiment, we evaluated if Rhinella diptycha tadpoles actively choose to forage in habitats with high resource (food) availability and if they avoid such habitats when predators are positively correlated with resource distribution. We also evaluated if behavioral changes under predation risk were associated with specific morphological phenotypes. We observed that tadpoles chose, although not intensely, habitats with high resource availability when predator cues were absent, but they avoided the same habitats when predation cues were present. We also observed an increase in swimming activity and morphological changes in tadpoles exposed to predation risk, especially related to body and tail morphology, which translates into rapid development. Our results suggest that tadpoles assess habitat quality through resource availability and predation risk. Moreover, our results suggest that tadpoles seem to exhibit functionally independent co-specialization of defensive strategies, due to the expression of specific behavioral and morphological phenotypes. [ABSTRACT FROM AUTHOR]

• Boko Haram refugee crisis nearly doubles grazing pressure in Logone Floodplain. • Ideal free distribution in floodplain persists despite arrival of pastoralist refugees. • Long-term data on livestock populations indicates resilience of pastoral system. • Open access to common-pool resources is key to resilience of open property regime. Previous studies have shown that the open property regime of mobile pastoralists in the Logone Floodplain, Cameroon works as a complex adaptive system in which individual movement decisions result in an ideal free distribution of grazing pressure over common-pool grazing resources. Recently, the humanitarian crisis in the Chad Basin caused by Boko Haram has resulted in the arrival of thousands of pastoralist refugees from Northeastern Nigeria in the Far North Region of Cameroon. In this paper, we examine the impact of pastoralist refugees on the resilience of the open property regime. First, we describe the migratory flight of pastoralists. Second, we examine whether and how the pastoralist refugee crisis affected the open property regime, in particular the distribution of pastoralists over grazing resources. Data were collected in a longitudinal and interdisciplinary study that integrated spatial and ethnographic approaches to describe and explain the distribution of pastoralists in the Logone Floodplain from 2008 to 2016. The results show that the number of pastoralist refugees from Nigeria exceeds 1000 households with an estimated 100,000 cattle. However, despite the large number of pastoralist refugees, we continue to find evidence of an ideal free distribution of pastoralists over grazing resources in the Logone Floodplain. Moreover, we found that pastoralists, while frustrated by the increasing grazing pressure, remained committed to the ethos of open access. The study offers evidence of the resilience of the open property regime and we discuss the reasons for the resilience of this complex adaptive system using the concept of panarchy. [ABSTRACT FROM AUTHOR]

Abstract Beaches are interesting ecosystems on which to test foraging ecology because the resident fauna mostly depend on unpredictably supplied allochthonous food resources. This study tests the food selection of two beach scavengers with different foraging strategies. Ghost crabs (Ocypode ryderi) patrol along the shore in search of food; it was predicted that, if given equal choices, they would select the most calorie-rich food. In contrast, swash-riding plough snails (Bullia spp.) need to make immediate decisions whether to emerge from the sand to feed on a beach-cast food item before it is washed away. It was predicted that they would emerge in response to all food equally because there is no guarantee of a better meal in their immediate future. These predictions were tested in two different in situ experiments that simulated natural foraging conditions for each scavenger. Ghost crabs consumed fish (highest calorific value) significantly more often than other foods. Similarly, significantly more snails responded to fish (higher calorific value) than jellyfish (lower calorific value); a result that was consistent with snail size, but was not affected by food-cue concentration. Beach scavengers are well adapted to the challenges of the ecosystem, and although food is supplied unpredictably, they still select for high-quality food, supporting optimal foraging theory. It is hypothesized that the patchy distribution of resident macrofauna on sandy shores may (partly) reflect their foraging ecology, sensu the ideal free distribution theory. Highlights • We test food selection by ghost crabs and plough snails on sandy beaches. • The first food item inspected by ghost crabs was no different from random. • Ghost crabs selected to consume fish more frequently than other food items. • Significantly more plough snails responded to beach-cast fish than jellyfish. • Beach scavengers select food with higher calorific value. [ABSTRACT FROM AUTHOR]

This article studies the effect of travel costs on population distribution in a patchy environment. The Ideal Free Distribution with travel costs is defined in the article as the distribution under which it is not profitable for individuals to move, i.e., the movement between patches ceases. It is shown that depending on the travel costs between patches, the Ideal Free Distribution may be unique, there may be infinitely many possible IFDs, or no Ideal Free Distribution exists. In the latter case, animal distribution can converge to an equilibrium of distributional dynamics at which individuals do disperse, but the net movement between patches ceases. Such distributional equilibrium corresponds to balanced dispersal. [ABSTRACT FROM AUTHOR]

Cost–benefit analysis is widely used to elucidate the association between foraging group size and resource size. Despite advances in the development of theoretical frameworks, however, the empirical systems used for testing are hindered by the vagaries of field surveys and incomplete data. This study developed the three approaches to data imputation based on machine learning (ML) algorithms with the aim of rescuing valuable field data. Using 163 host spider webs (132 complete data and 31 incomplete data), our results indicated that the data imputation based on random forest algorithm outperformed classification and regression trees, the k-nearest neighbor, and other conventional approaches (Wilcoxon signed-rank test and correlation difference have p-value from < 0.001–0.030). We then used rescued data based on a natural system involving kleptoparasitic spiders from Taiwan and Vietnam (Argyrodes miniaceus, Theridiidae) to test the occurrence and group size of kleptoparasites in natural populations. Our partial least-squares path modelling (PLS-PM) results demonstrated that the size of the host web (T = 6.890, p = 0.000) is a significant feature affecting group size. The resource size (T = 2.590, p = 0.010) and the microclimate (T = 3.230, p = 0.001) are significant features affecting the presence of kleptoparasites. The test of conformation of group size distribution to the ideal free distribution (IFD) model revealed that predictions pertaining to per-capita resource size were underestimated (bootstrap resampling mean slopes p < 0.001). These findings highlight the importance of applying appropriate ML methods to the handling of missing field data.

Highlights • We examine the ecological context of Neo-Eneolithic settlement in Eastern Europe. • Site selection criteria suggest shift in subsistence economy occurred ∼3500–3000 BCE. • Subsistence strategies changed in response to environmental fluctuation. • Transition to Early Bronze Age was preceded by endogenous pastoralist transition. Abstract During the fourth millennium BCE socioeconomic change from a regime of Neo-Eneolithic village-based sedentary agriculture to more itinerant pastoralism dramatically changed European society. Continental-scale archaeological and genetic studies generally attribute this change to the movement of Early Bronze Age (EBA) populations into Eastern Europe ca. 3000 BCE. However, archaeological assemblages in Ukraine, Moldova, and Romania suggest that migrations and changes in subsistence regime started earlier, coinciding with climatic change during the 5.9 ka event (Bond Event 4) and continuing into the Atlantic/Subboreal transition. We apply the Ideal Free Distribution (IFD) to a settlement record spanning over 3000 years (ca. 6100–3000 BCE) in 14 sub-regions of Eastern Europe to establish a quantitative indicator of changing subsistence strategies throughout the fourth millennium BCE. This provides corroboration for arguments made on the basis of careful study of material culture, which suggest that economic changes were gradual, regionally diverse in their manifestation and pre-date the arrival of EBA populations in Eastern Europe. Our implementation of the IFD shows it to be a useful tool for highlighting changes in regional subsistence regimes, but further analysis is required to address issues of habitat ranking, migratory vectors, and settlement dating on smaller scales. [ABSTRACT FROM AUTHOR]

Abstract Archaeologists now routinely use summed radiocarbon dates as a measure of past population size, yet few have coupled these measures to theoretical expectations about social organization. To help move the 'dates as data' approach from description to explanation, this paper proposes a new integrative theory and method for quantitative analyses of radiocarbon summed probability distributions (SPDs) in space. We present this new approach to 'SPDs in space' with a case study of 3571 geo-referenced radiocarbon dates from Wyoming, USA. We develop a SPD for the Holocene in Wyoming, then analyze the spatial distribution of the SPD as a function of time using a standard nearest-neighbor statistic. We compare population growth and decline throughout the Holocene with expectations for different Ideal Distribution Models from population ecology that predict the relationship between habitat quality and population density. Results suggest that populations in Wyoming were initially clustered and then became increasingly dispersed through the course of the Holocene. These results suggest that Allee-like benefits to aggregation, rather than ideal free-driven dispersion patterns, explain settlement decisions in response to growing populations. Our approach is a first step in constructing a method and theory for describing relationships between social organization and population growth trends derived from archaeological radiocarbon time-series. [ABSTRACT FROM AUTHOR]

Current theoretical models of the commons assert that common-pool resources can only be managed sustainably with clearly defined boundaries around both communities and the resources that they use. In these theoretical models, open access inevitably leads to a tragedy of the commons. However, inmany openaccess systems, use of common-pool resources seems to be sustainable over the long term (i.e., current resource use does not threaten use of common-pool resources for future generations). Here, we outline the conditions that support sustainable resource use in open property regimes. We use the conceptual framework of complex adaptive systems to explain how processes within and couplings between human and natural systems can lead to the emergence of efficient, equitable, and sustainable resource use. We illustrate these dynamics in eight case studies of different social-ecological systems, including mobile pastoralism, marine and freshwater fisheries, swidden agriculture, and desert foraging. Our theoretical framework identifies eight conditions that are critical for the emergence of sustainable use of common-pool resources in open property regimes. In addition, we explain how changes in boundary conditions may push open property regimes to either common property regimes or a tragedy of the commons. Our theoretical model of emergent sustainability helps us to understand the diversity and dynamics of property regimes across a wide range of social-ecological systems and explains the enigma of open access without a tragedy. We recommend that policy interventions in such self-organizing systems should focus on managing the conditions that are critical for the emergence and persistence of sustainability. [ABSTRACT FROM AUTHOR]

Habitat selection models can explain spatial patterns in the relative abundance of animals in different habitats based on the assumption that fitness declines as density in a habitat increases. Ectotherms, such as lizards, may not follow predictions of density-dependent habitat selection models because temperature, which is unaffected by density, strongly influences their habitat selection. If competition for limited resources decreases fitness, then crowding should cause a decrease in body size and growth rates. We used skeletochronology and body size data from tree lizards (Urosaurus ornatus) at six sites that each spanned two habitats varying in quality to test the hypothesis that habitat selection is density dependent because growth is limited by competition for resources and by habitat quality. First, we tested that the maximum body size of lizards decreased with higher densities in a habitat by comparing growth between sites. Second, we tested whether body size and growth were higher in the habitat with more resources by controlling for density in a habitat and comparing growth between habitats in different sites. We found evidence of density-dependent growth in females, but not in males. Females in more crowded sites reached a smaller maximum size. Females in the higher quality habitat also grew larger than females in the lower quality habitat after controlling for differences in density between the habitats. Therefore, we found partial support for our hypothesis that competition for resources limits growth and causes density-dependent habitat selection. [ABSTRACT FROM AUTHOR]

Abstract Operational and environmental factors limited available resource space of gillnet and longline fishers targeting Nile perch in the Speke gulf and open lake of southern Lake Victoria and drove their encounter rates with patches of fish resulting in gear specific distributional patterns. Catch-rate patterns were similar by region and gear: large (>50 cm) Nile-perch densities increased over distance from homeport and deeper in the water column while small Nile perch (<50 cm) densities decreased. Effects of season, (setting) depth and region were present but small and obscured by high variation in daily catch-rates and individual fisher strategies. Both fisheries distributed themselves over the size-productivity spectrum of Nile perch but reacted differently to patterns in size distribution of Nile perch: gillnetters focused more on numbers of productive juveniles between 30 and 60 cm at on average 5 km distance (59 min travel time) from homeport and longliners on larger sized 40–80 cm Nile perch deeper in the water column at 7 km (108 min). Sampled fishers likely were representative of most of the Nile perch fisheries. If so, this means that fishing pressure is mainly exerted on nearshore lake areas, and more lightly fished offshore areas may act as a refuge for adult Nile perch. Total catch-rates by gear were generally equalized over the resource space, increasing slightly with distance from homeport, according to ideal free distribution predictions. Nile perch fishers on Lake Victoria appear to distribute themselves according to the underlying productivity distribution of the resource within the constraints of their available resource space. [ABSTRACT FROM AUTHOR]

Abstract Some invasive species can persist in their habitat but eventually spread very slow in a nonlinear fashion to expand their habitat range. In order to capture this phenomenon, we consider reaction–diffusion–advection models with a free boundary modeling the spreading and the biased movement of species in one-dimensional spatially heterogeneous environments. Under a condition of low resource quality, we find that large advection can lead to the spreading of the species but the spreading speed goes asymptotically to zero. Moreover, we investigate the effect of the resource on the dynamics of the current problem. Finally, we bring the notion of an ideal free distribution (IFD) into free boundary problems to understand the mechanism such that the species can eventually match the environmental quality perfectly. Under the current problem setting, the IFD may not hold even if the population plays an ideal free strategy. We then provide a sufficient condition for the IFD to be reached when using an ideal free strategy. [ABSTRACT FROM AUTHOR]

The vertical distribution of planktonic animals, such as Daphnia , in overlapping gradients of food concentration and risk of visual predation should depend on Daphnia population density and should be the result of the group effect of optimizing decisions taken by each individual (juvenile or adult), trading-off a high growth rate to low mortality risk. We tested this hypothesis by comparing the theoretical distributions from simulations based on an experimentally parameterized, optimizing individual-based model (consistent with the assumptions of the concept of the interference ideal free distribution with costs) with distributions observed in laboratory experiments. The simulations were generated for two scenarios, where the shape of the functional response of fish is consistent with either type II or III. The results confirmed the hypothesis. The greatest similarity of the distributions obtained in the experiments and simulations was found for the simulations based on the scenario assuming the type III rather than type II for both age classes of Daphnia. This was consistent with the results of the experiments for the model parameterization, which revealed the type III functional response of fish. Therefore, the results suggest that aggregating may be maladaptive as an anti-vertebrate-predation defense in the case of zooplankton. [ABSTRACT FROM AUTHOR]

By considering various biotic and abiotic factors, organisms are expected to distinguish among suitable habitats of different quality and choose the one that offers them the highest fitness payoff. According to the ideal-free-distribution model, density drives organism choice and ultimately distribution among habitats. However, deviations from the basic model are common, as it does not take into account intrinsic and extrinsic constraints. Two important constraints are those of habitat geometry (e.g. habitat area, habitat shape), and perceptual range. We used a trap-building predator, the wormlion larva, to examine these constraints. We manipulated the geometry of the preferred shaded microhabitat and the distance of individuals from it, and assessed their effect on wormlion habitat choice, distribution patterns, and performance. Habitat geometry affected wormlion microhabitat choice and distribution patterns, measured as distance from the habitat center and spatial pattern type, but had no effect on performance, expressed as the area of the pit-trap constructed. The interaction between habitat geometry and density was inconsistent regarding the distribution patterns, affecting distance from the center but not the spatial pattern type. Furthermore, we found that wormlions demonstrated a low perceptual range, which limited their ability to sense proximate shaded conditions. We highlight the importance of incorporating the interplay between habitat geometry, density, and perceptual range when studying habitat choice and spatial patterns and suggest that spatial patterns should be analyzed in more than a single way. [ABSTRACT FROM AUTHOR]