Ideal Free Distribution Research Articles

Machine Learning Data Imputation and Prediction of Foraging Group Size in a Kleptoparasitic Spider

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 <IFD predicted slopes, p < 0.001). These findings highlight the importance of applying appropriate ML methods to the handling of missing field data.

Breakdown of the ideal free distribution under conditions of severe and low competition

Under the ideal free distribution (IFD), the number of organisms competing for a resource at different sites is proportional to the resource distribution among sites. The ideal free distribution of competitors in a heterogeneous environment often predicts habitat matching, where the relative number of individuals using any two patches matches the relative availability of resources in those same two patches. If a resource is scarce, access might be restricted to individuals with high resource holding potential, resulting in deviation from the IFD. The distribution of animals may also deviate from the IFD in the case of resource abundance, when social attraction or preference for specific locations rather than competition may determine distribution. While it was originally developed to explain habitat choice, we apply the habitat matching rule to microscale foraging decisions. We show that chickens feeding from two nondepleting feeders distribute proportionally to feeder space under intermediate levels of competition. However, chicken distribution between the feeders deviates from the IFD when feeder space is limited and competition high. Further, despite decreasing aggression with increasing feeder space, deviation from IFD is also observed under an excess supply of feeder space, indicating different mechanisms responsible for deviations from the IFD. Besides demonstrating IFD sensitivity to competition, these findings highlight IFD’s potential as a biological basis for determining minimal resource requirements in animal housing.Significance statementThe ideal free distribution (IFD) predicts how animals ought to distribute themselves within a habitat in order to maximize their payoff. Recent studies, however, have questioned the validity of the IFD concept following anomalous results. We studied the IFD in chickens by systematically varying the amount and distribution of space at two feed troughs. We show that when tested over a sufficiently large range, the distribution of birds depends on the overall resource availability. Furthermore, behavioral data suggest that distinctly different mechanisms account for deviations from the IFD at shortage and excess supply of feeder space, respectively.

Specialist Birds Replace Generalists in Grassland Remnants as Land Use Change Intensifies

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.

Household Inequality, Community Formation, and Land Tenure in Classic Period Lowland Maya Society

Access to social capital and valued resources modulates household decision-making as people seek to occupy the best-quality patches of land available. Prior occupancy, inheritance, and land tenure norms can constrain opportunities resulting in inequality between households. We examined processes of settlement development and structural inequality at two Classic Period (250–900 CE) Maya centers, Ix Kuku’il and Uxbenka, in Southern Belize. From the lens of human behavioral ecology (HBE), we evaluate the predictions of two population density models, the ideal free distribution (IFD) and the ideal despotic distribution (IDD), on household decision-making. To do so, we correlate the initial foundation date of households with nine measurable suitability variables as proxies for social and environmental resources. We conclude that at Uxbenka and Ix Kuku’il, social resources, such as the ability to mobilize labor, cooperation, and access to a transportation corridor, likely influenced where people chose to live. Environmental resources, including good farmland and access to perennial water sources, were widely distributed across the landscape and accessible to everyone. This study highlights the importance of social relationships on household decision-making, which is often difficult to detect in the archaeological record. The development and manifestation of institutionalized inequality are processes relevant to all societies past and present.

An ecological model of settlement expansion in northwestern Morocco

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.

Ideal Free Dispersal under General Spatial Heterogeneity and Time Periodicity

A population is said to have an ideal free distribution in a spatially heterogeneous but temporally constant environment if each of its members have 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 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 strategies that do not produce an ideal free distribution. 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 showed that there exist 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.

IDEAL FREE DISTRIBUTION IN DIFFUSION-ADVECTION-REACTION MODELS ON A HETEROGENEOUS HABITAT

. A model of the “predator – prey” system based on the diffusion-reaction-advection equations describing the multifactorial taxis of both predator and prey is presented. The spatial distribution of species in a heterogeneous area taking into account the concept of ideal free distribution (IFD) is analyzed. Relationships have been established for the parameters at which the IFD is realized. The transformations of the solutions are studied when the parameters deviate from the conditions ensuring the IFD, as well as the occurrence of self-oscillatory modes.

Modelling fishing location choice and spatial behaviour of fishers near a marine protected area

PurposeThis study investigates whether higher catch rates near a marine protected area (MPA), and/or in other fishing areas within a choice set, attract more fishers. A survey conducted in the fishing grounds near an MPA located in south east of Mauritius in the Indian Ocean shows concentration of fishers in regions with lower catch rates. This contrasts with the predictions of the “fishing the line” hypothesis and the ideal free distribution (IFD) that fishers are likely to be attracted near the MPA with higher resource abundance.Design/methodology/approachUsing the random utility model as the framework and the random parameter logit (RPL) model, the study attempts to explain spatial behaviour of fishers. Expected catch and catch variability are modelled using the Just and Pope (JP) production function. The study also estimates effort elasticities with respect to expected catch and catch variability and simulates the relocation of effort from area closure.FindingsThe paper concludes that higher catch does attract fishers but is a partial and very restrictive explanation of fishers' behaviour. The “fishing the line” hypothesis does hold to some extent, but it should not be taken for granted that rising catch rates in adjacent waters will increase fishing pressure. The paper concludes that factors such as catch variability, distance from homeport to fishing ground, potential physical risk and attitudes towards risk of fishers affect spatial behaviour of fishers and should be considered for the placement and size of MPAs. The study also finds that the responsiveness of effort to catch rates is lowest in areas which are already heavily fished and easily accessible.Practical implicationsThe identification of fishing areas as complements (when fishing in one area increases fishing effort in another) and substitutes is valuable information for determining the placement and size of an MPA. A larger reserve is likely to have more displacement effect in this case than a smaller one. Therefore, a small or a network of a small reserve may be appropriate. The premise to select the site and size of the reserve is to avoid overconcentration of fishers in alternative fishing areas, which can be vulnerable to excessive fishing and unintended effects from fishers.Originality/valueThe paper contributes to an understanding of fishing behaviour and its impact on the configuration of marine reserves. It discusses the importance of effort elasticities to determine the placement and size of an MPA. Studies on this topic are very scanty in the Indian Ocean region. It also shows the application of location choice model, the RPL model and the JP production function in the fisheries sector for a small island.

Is conservation based on best available science creating an ecological trap for an imperiled lagomorph?

Habitat quality regulates fitness and population density, making it a key driver of population size. Hence, increasing habitat quality is often a primary goal of species conservation. Yet, assessments of fitness and density are difficult and costly to obtain. Therefore, species conservation often uses “best available science,” extending inferences across taxa, space, or time, and inferring habitat quality from studies of habitat selection. However, there are scenarios where habitat selection is not reflective of habitat quality, and this can lead to maladaptive management strategies. The New England cottontail (Sylvilagus transitionalis) is an imperiled shrubland obligate lagomorph whose successful recovery hinges on creation of suitable habitat. Recovery of this species is also negatively impacted by the non‐native eastern cottontail (Sylvilagus floridanus), which can competitively exclude New England cottontails from preferred habitat. Herein, we evaluate habitat quality for adult and juvenile New England and eastern cottontails using survival and density as indicators. Our findings did not support selection following an ideal free distribution by New England cottontails. Instead, selected resources, which are a target of habitat management, were associated with low survival and density and pointed to a complex trade‐off between density, survival, habitat, and the presence of eastern cottontails. Further, movement distance was inversely correlated with survival in both species, suggesting that habitat fragmentation limits the ability of cottontails to freely distribute based on habitat quality. While habitat did not directly regulate survival of juvenile cottontails, tick burden had a strong negative impact on juvenile cottontails in poor body condition. Given the complex interactions among New England cottontails, eastern cottontails, and habitat, directly assessing and accounting for factors that limit New England cottontail habitat quality in management plans is vital to their recovery. Our study demonstrates an example of management for possible ecological trap conditions via the application of incomplete knowledge.

The Role of Microhabitat and Water Level in Regulating the Small-Scale Distribution, Seasonal Abundance and Overwintering Success of the Protected Snail Vertigo moulinsiana in a Natural Wetland

Despite the high taxonomic diversity, wide distribution and important ecosystem functions of snails, their ecology remains obscure, and this can hamper their conservation. Overwintering in the studied population of Vertigo moulinsiana is effective enough to allow the majority of it to survive. The population dynamics of V. moulinsiana is specific, where the summer boom in a suboptimal habitat covering a small area (wet patches of sweet grass) can determine the snail's range over much larger areas. Our results suggest that humidity could have been the major factor governing population increase. The summer boom is caused by juveniles appearing in very large numbers during this period, thus the peak height is mostly influenced by the considerable susceptibility of juveniles and eggs to desiccation. The limiting influence of humidity is evident in the unequal spatial distribution of individuals: the wetter the substrate, the greater the abundance of snails. As a consequence, the boom may be spatially regulated and only occurs in wet habitats, even though the snail actually occupies a much larger area. Our results indicate that this V. moulinsiana population does not follow typical models constructed for vertebrates or other animals with high dispersal abilities, like the Ideal Free Distribution (IFD) model, and requires a specific approach. Its specific spatiotemporal pattern should be taken into account during monitoring surveys and conservation actions.

Habitat selection patterns are density dependent under the ideal free distribution.

Despite being widely used, habitat selection models are rarely reliable and informative when applied across different ecosystems or over time. One possible explanation is that habitat selection is context‐dependent due to variation in consumer density and/or resource availability. The goal of this paper is to provide a general theoretical perspective on the contributory mechanisms of consumer and resource density‐dependent habitat selection, as well as on our capacity to account for their effects.Towards this goal we revisit the ideal free distribution (IFD), where consumers are assumed to be omniscient, equally competitive and freely moving, and are hence expected to instantaneously distribute themselves across a heterogeneous landscape such that fitness is equalised across the population. Although these assumptions are clearly unrealistic to some degree, the simplicity of the structure in IFD provides a useful theoretical vantage point to help clarify our understanding of more complex spatial processes. Of equal importance, IFD assumptions are compatible with the assumptions underlying common habitat selection models.Here we show how a fitness‐maximising space use model, based on IFD, gives rise to resource and consumer density‐dependent shifts in consumer distribution, providing a mechanistic explanation for the context‐dependent outcomes often reported in habitat selection analysis. Our model suggests that adaptive shifts in consumer distribution patterns would be expected to lead to nonlinear and often non‐monotonic patterns of habitat selection.These results indicate that even under the simplest of assumptions about adaptive organismal behaviour, habitat selection strength should critically depend on system‐wide characteristics. Clarifying the impact of adaptive behavioural responses may be pivotal in making meaningful ecological inferences about observed patterns of habitat selection and allow reliable transferability of habitat selection predictions across time and space.

Interpreting plant root responses to nutrients, neighbours and pot volume depends on researchers’ assumptions

Abstract 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.

Spiders follow an ideal free distribution based on traits of the plant community

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.

Modeling Incipient Use of Neolithic Cultigens by Taiwanese Foragers: Perspectives from Niche Variation Theory, the Prey Choice Model, and the Ideal Free Distribution

The earliest evidence for agriculture in Taiwan dates to about 6000 years BP and indicates that farmer-gardeners from Southeast China migrated across the Taiwan Strait. However, little is known about the adaptive interactions between Taiwanese foragers and Neolithic Chinese farmers during the transition. This paper considers theoretical expectations from human behavioral ecology based models and macroecological patterning from Binford’s hunter-gatherer database to scope the range of responses of native populations to invasive dispersal. Niche variation theory and invasion theory predict that the foraging niche breadths will narrow for native populations and morphologically similar dispersing populations. The encounter contingent prey choice model indicates that groups under resource depression from depleted high-ranked resources will increasingly take low-ranked resources upon encounter. The ideal free distribution with Allee effects categorizes settlement into highly ranked habitats selected on the basis of encounter rates with preferred prey, with niche construction potentially contributing to an upswing in some highly ranked prey species. In coastal plain habitats preferred by farming immigrants, interactions and competition either reduced encounter rates with high ranked prey or were offset by benefits to habitat from the creation of a mosaic of succession ecozones by cultivation. Aquatic-focused foragers were eventually constrained to broaden subsistence by increasing the harvest of low ranked resources, then mobility-compatible Neolithic cultigens were added as a niche-broadening tactic. In locations less suitable for farming, fishing and hunting continued as primary foraging tactics for centuries after Neolithic arrivals. The paper concludes with a set of evidence-based archaeological expectations derived from these models.

The effects of animal personality on the ideal free distribution.

The ideal free distribution (IFD) has been used to predict the distribution of foraging animals in a wide variety of systems. However, its predictions do not always match observed distributions of foraging animals. Instead, we often observe that there are more consumers than predicted in low-quality patches and fewer consumers than predicted in high-quality patches (i.e. undermatching). We examine the possibility that animal personality is one explanation for this undermatching. We first conducted a literature search to determine how commonly studies document the personality distribution of populations. Second, we created a simple individual-based model to conceptually demonstrate why knowing the distribution of personalities is important for studies of populations of foragers in context of the IFD. Third, we present a specific example where we calculate the added time to reach the IFD for a population of mud crabs that has a considerable number of individuals with relatively inactive personalities. We suggest that animal personality, particularly the prevalence of inactive personality types, may inhibit the ability of a population to track changes in habitat quality, therefore leading to undermatching of the IFD. This may weaken the IFD as a predictive model moving forward.

Consumer-resource dynamics in Arctic ponds.

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.

Cultural spaces and climate change: Modeling Holocene archaeological settlement patterns on the coastal plain of the southeastern United States

Ideal free distribution (IFD) models generally predict that populations, including human populations, will distribute themselves across the landscape such that resource access is optimized. However, links between ecology and human responses to it are not always straightforward, especially during periods of climate change when people often act based on incomplete information and for reasons not connected directly to ecological output. Here, we analyze archaeological site distribution across the coastal plains of South Carolina, Georgia, and Florida to test the roles that both ecology and knowledge of a region, as estimated based on past site occupations, played in human decision making during the Middle and Late Archaic periods. These periods correlate to substantial climatic, environmental and ecological change during the middle Holocene and beginning of the late Holocene. We find that IFD models that include both ecological variables and past landscape use fit both cultural periods, but to different degrees.

Dynamic Modeling of the Effects of Site Placement on Environmental Suitability: A Theoretical Example from Northwest Morocco

ABSTRACT This paper offers a new numerical approach to model the effects of archaeological site placement and population density on environmental suitability using two ecological models, the Ideal Free Distribution (IFD) and Ideal Despotic Distribution (IDD), treating the Oued Loukkos in northern Morocco as an example. This method incorporates local resource depletion with increasing population density consistent with the predictions of the IFD. It also incorporates the potential for the exclusion of part of the population from certain productive areas consistent with the IDD. In this study, we propose a dynamic approach to the impact of site placement on habitat suitability and therefore broader application for understanding changes in settlement distribution with population density through time. Furthermore, resulting settlements can be parameterized by a Zipf-Mandelbrot distribution, entailing a direct relationship between the ecological, demographic, and political factors and the resulting rank-size distribution of sites. This approach allows for a broader range of applications among foraging and agricultural economies.

Fire on the Mountain: The Ideal Free Distribution and Early Hunter-gatherer Demography in the Tennessee River Drainage, USA

ABSTRACT The colonisation of North America and subsequent adaptation to climate change are major research foci in the American Southeast. Here, we used the Ideal Free Distribution from Behavioural Ecology and projections of fossil pollen to generate predictions for landscape use. We tested these predictions against the distribution of previously recorded projectile points in the Paleoindian Database of the Americas and archaeological sites in the Digital Index of North American Archaeology for the Tennessee River drainage from the appearance of Clovis sites in the terminal Pleistocene though the Late Holocene (∼13,250–3,000 cal BP). We found that the distribution of points and sites were initially skewed towards lower elevations, and then spread to higher elevations over the course of the Younger Dryas into the Middle Holocene, which is consistent with predictions of the Ideal Free Distribution. However, during the Middle Holocene, sites are more clustered, which is consistent with a shift to an Ideal Free Distribution with Allee effect that was likely driven by a broader distribution of oak–hickory forests. Finally, the distribution of sites after the Middle Holocene was more dispersed, which is consistent with a shift to an Ideal Despotic Distribution.

Mobility and its sensitivity to fitness differences determine consumer-resource distributions.

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.