Lottery Competition Research Articles

Dynamics of a multi-species lottery competition model in stochastic environments

An N-dimensional lottery model for competition among [Formula: see text] ecological species in stochastic environments is studied under the i.i.d. assumption. First, a system of nonlinear stochastic differential equations (SDEs) is developed as the diffusion approximation for the discrete lottery model. Then the existence and uniqueness of positive and bounded global solutions, as well as long-term dynamics for the solution are investigated. In particular, sufficient conditions under which extinction and persistence occur are constructed, respectively.

The Lottery Model for Ecological Competition in NonStationary Environments

A two-species lottery competition model with nonstationary reproduction and mortality rates of both species is studied. First, a diffusion approximation for the fraction of sites occupied by each a...

Proximity to roads disrupts rodents’ contributions to seed dispersal services and subsequent recruitment dynamics

Abstract Seed dispersal and subsequent recruitment dynamics play a crucially important role in regulating species coexistence and structuring tree diversity in diverse forests. Wildlife, which can dually shape the tree recruitment process by simultaneously functioning as natural enemies and seed dispersers, are undergoing widespread changes in population and behaviour due to the detrimental effects of expanding global road networks. However, the impact of these changes on recruitment dynamics through the alteration of seed dispersal processes remains understudied. Here, we assessed how roads affect animal‐mediated recruitment dynamics from the seed to adult stages of trees using a ubiquitous vertebrate‐seed model: rodents and acorns. To quantify the degree to which proximity to a road alters seed dispersal and regulates subsequent recruitment dynamics, we conducted seed dispersal and predation experiments, and investigated the natural recruitment of a dominant tree species (Quercus aliena) from September 2009 to July 2012 in a subtropical forest of central China. Roads caused a decreased seed dispersal distance and increasing larder hoarding, demonstrating a weakened contribution of rodents to seed dispersal services. These patterns were stronger in the masting year than in the non‐masting year. Correspondingly, seedlings, saplings and adult trees had higher densities near roads than far from roads. Near roads, recruit transition rates (i.e. seedling‐to‐sapling and sapling‐to‐juvenile) were low, and the influential strength of conspecific adult density was weakened over these recruit transitions, indicating that space limitation and lottery competition, not conspecific negative density‐dependent effects, approximately determined the near‐road recruitment process. Furthermore, most adults near roads were young, and their ages matched the road ages. Synthesis. Roads diminished animal‐mediated seed dispersal services and disrupted subsequent recruitment dynamics in Quercus aliena populations, thus weakening the key process promoting diversity in forest ecosystems. Given that these animal‐regulated roles in recruitment dynamics are widespread stabilizing forces for tree coexistence, our findings suggest that the ubiquity of roads and their continued expansion will contribute to the increase in forests dominated by a relatively low number of species. Consequently, the growing expansion of road networks will ultimately cause profound changes in community composition and structure across diverse forests worldwide.

Are there so many congeneric species of chironomid larvae in a small stream?

The co-occurrence of larvae of congeneric chironomid species is common in natural stream assemblages, and raises the problem of finding mechanisms to explain the co-existence of species with similar ecological requirements. In this contribution, we explored the co-occurrence of chironomid larvae belonging to congeneric species within four genera of chironomids: Cricotopus, Eukiefferiella, Orthocladius and Rheocricotopus (with 2, 7, 2 and 4 species, respectively) in the headwaters of a small Mediterranean calcareous stream. Due to the intrinsic, natural spatial and temporal variability in these habitats, we studied three different sites at two different seasons within the annual hydrological cycle (spring vs summer samples), and each microhabitat unit was surveyed with an effort proportional to its cover at the sampling site. The Outlying Median Index method was used to distinguish the niches of the different chironomid species in relation to the hydraulic features and substrates within each site. Our results showed that hydraulic features helped to improve discrimination between the niches of five congeneric species of Eukiefferiella, and the same occurred within the species belonging to Cricotopus and Orthocladius, although niche overlap was high in general. One Rheocricotopus species was associated to algal substrate. Schoener’s co-occurrence at the microhabitat scale was low among the congeneric species found in our study, suggesting exclusion mechanisms. Flow regime, substrate type and shifts in environmental conditions may favor the settlement of some species to the detriment of other congeneric ones, but other mechanisms such as lottery competition, diffusion competition or predation should be considered in further studies.

Prolific fruit output by the invasive tree Bellucia pentamera Naudin (Melastomataceae) is enhanced by selective logging disturbance

AbstractSelective logging in tropical rain forests may promote population growth of invasive plants. The ability of invaders to respond, specifically in reproductive traits, to increase in resource abundance may allow them to increase their presence in the seed rain of recipient communities. The invasive pioneer tree Bellucia pentamera (Melastomataceae) is currently spreading within Gunung Palung National Park in West Kalimantan, Indonesia. The park has also experienced periods of illegal, small‐scale, selective logging that seem to have facilitated population growth and spread of this invader. We first used fruiting frequency as a proxy for fruit output to make comparisons between B. pentamera and the native tree community of over 200 genera. We then constructed two Generalized Linear Autoregressive Moving Average (GLARMA) models using 13 months of phenology data to predict both fruiting frequency and crop size of B. pentamera under selective logging versus natural treefall disturbance regimes. Bellucia pentamera fruited at considerably higher frequency than all 200 native genera considered. This invader also responded positively to selective logging with both odds of being in fruit and crop sizes at least doubling in logged plots. Prolific seed output of B. pentamera is especially problematic within the lottery competition of tropical rain forest gap tree communities, in which prominence in the seed rain is particularly important. Furthermore, the reproductive response of B. pentamera to selective logging suggests that this harvesting practice may have a considerable role in facilitating this invasion in Southeast Asia.

Competitive mechanisms change with ontogeny in coral-dwelling gobies.

Recent theory suggests that a mix of lottery and niche processes can facilitate coexistence between competing species, but this has not yet been empirically tested. Previous research has suggested that a competitive lottery for space promotes coexistence between two ecologically similar species, Gobiodon histrio and Gobiodon erythrospilus. However, not all the assumptions of lottery competition have been tested, and patterns of habitat use by adults suggest niche partitioning. Here, we investigated the hypothesis that the mechanism of competition changes with ontogeny, with a lottery for space operating at settlement and niche partitioning occurring in adults. Patterns of resource use in the field were compared for juveniles and adults of the two species. Pelagic larval duration (PLD) and size-at-settlement was also estimated to determine if size differences at settlement could affect the outcome of competitive interactions among juveniles. Habitat preference and size-based competitive ability were then tested for juveniles and adults in laboratory experiments. Finally, a transplant experiment was performed to test the fitness-associated consequences of niche partitioning among adults and its implications for coexistence of the two species. G. histrio had a similar PLD (20.7 ± 2.0 days) to G. erythrospilus (18.5 ± 1.9 days), and there was no difference in size-at-settlement between the species. Juveniles of the two species had similar patterns of habitat use and similar competitive abilities, supporting the lottery mechanism at settlement. However, adults differ in their habitat use, supporting the prediction that resource partitioning increases with ontogeny. In laboratory experiments, adults of each species preferred colonies of Acropora nasuta. However, G. histrio was a superior competitor and prevented G. erythrospilus from using A. nasuta in > 70% of the trials. In the field transplant experiment, G. erythrospilus (inferior competitor) suffered less of a fitness loss when occupying the non-preferred coral (A. spathulata) compared with G. histrio, which could explain its ability to persist when displaced by the superior competitor. These results suggest that the competitive mechanism operating between the two Gobiodon species shifts from a lottery for space to niche partitioning through ontogeny, and that these two mechanisms of competitive coexistence are not mutually exclusive.

Spatial structures of the environment and of dispersal impact species distribution in competitive metacommunities.

The correspondence between species distribution and the environment depends on species’ ability to track favorable environmental conditions (via dispersal) and to maintain competitive hierarchy against the constant influx of migrants (mass effect) and demographic stochasticity (ecological drift). Here we report a simulation study of the influence of landscape structure on species distribution. We consider lottery competition for space in a spatially heterogeneous environment, where the landscape is represented as a network of localities connected by dispersal. We quantified the contribution of neutrality and species sorting to their spatial distribution. We found that neutrality increases and the strength of species-sorting decreases with the centrality of a community in the landscape when the average dispersal among communities is low, whereas the opposite was found at elevated dispersal. We also found that the strength of species-sorting increases with environmental heterogeneity. Our results illustrate that spatial structure of the environment and of dispersal must be taken into account for understanding species distribution. We stress the importance of spatial geographic structure on the relative importance of niche vs. neutral processes in controlling community dynamics.

Coexistence patterns of two invasive thistle species, Carduus nutans and C. acanthoides, at three spatial scales

To better understand the competitive processes involved in invasion by congeners, we examine coexistence patterns of two invasive species, Carduus nutans and C. acanthoides, at three spatial scales. A roadside survey of 5 × 5 km blocks in a previously identified overlap zone provided information about the regional scale. At smaller scales, we surveyed four fields of natural co-occurrence, quantifying the spatial patterns at the field scale by randomly placed 1 × 1 m quadrats and at the smallest scale by detailing plant position within the quadrats. The patterns observed are strikingly different at the different scales. At the regional scale, there is positive local autocorrelation in both species but negative cross-correlation between them, consistent with previous surveys. However, at the field scale, there is positive local autocorrelation in both species, and we generally see a positive association between the two species. At the plot scale, when excluding areas of joint absence, there is again a negative association between the two species. This pattern can also be seen at the field scale when excluding plots with joint absence. These results suggest that, at the scale of a field, the strongest factor determining location is aggregation in favorable habitats, which is a stronger force than the competition-induced segregation evidenced at small scales. Lottery competition for spatially aggregated safe sites thus appears to drive the patterns observed at the field scale, while the regional scale pattern may be a result of restricted natural dispersal and invasion history.

Spatiotemporal controls of simulated metacommunity dynamics in dendritic networks

AbstractUnderstanding the mechanisms that create spatial and temporal patterns of functional diversity in stream networks is a goal of basic research and has implications for effective conservation of freshwater ecosystems. These patterns are likely to be influenced by the combination of temporally variable environmental conditions, movement constraints imposed by network structure, and the trait composition of local communities. We developed a simplified metacommunity model to investigate complex interactions among these factors under lottery competition for local resources, such as establishment sites. We used this model to examine how local and regional community composition varied in 3 scenarios: a null implementation involving only spatial effects, an implementation that combined network constraints with dispersal-trait variation, and an implementation in which a trade-off between multiple functional traits was paired with varying levels of temporal autocorrelation in the intensity of mortality. Thes...

Mutualism between Consumers and Their Shared Resource Can Promote Competitive Coexistence

Competitive coexistence depends on dynamic interactions between competitor and resource populations, including mutualism between the resource and each competitor. We add mutualism to a well-known model of resource competition and show that it can powerfully stabilize competitive coexistence in the absence or presence of resource heterogeneity. We use a transition matrix approach to describe lottery competition, while allowing each of two competitors to affect the population dynamics of their shared resource. For example, two plant-defending ant species may compete for nesting space within ant-adapted (myrmecophytic) plants. We show that mutualism between consumers and a resource species can stabilize competitive coexistence of the consumers by allowing each competitor to influence resource dynamics in a way that benefits the other. The effect of this novel coexistence mechanism depends on a mutualism's biological details: for example, altering myrmecophyte fecundity affects competing ant species differently than does altering plant survival. Finally, we consider a heterogeneous resource (e.g., two types of nest site) and show how niche partitioning can stabilize coexistence in the absence of resource dynamics. When resource heterogeneity is dynamic (e.g., small and large plants of the same species), niche partitioning also provides new routes for additional stabilization via mutualism.

The relationship between endophyte transition and plant species coexistence

The survival possibilities of terrestrial plant species are determined by their competitive abilities. One factor that affects competitive ability is the community of microorganisms that lives in association with the plants. Microorganisms affect the competitive dominance among plants by means of their metabolites. In this paper, we study the multiple plant species coexistence mediated by interactions with endophytes (fungi). The population dynamics are described by a revised lottery competition model for multiple plant species, each of which is divided into two classes: plants with endophytes (denoted EP) and plants without endophytes (NEP). The model includes the transition of seeds from EP to NEP. We show multiple species of plants cannot coexist in a steady state if this transition is density independent, but can coexist in a steady state if this transition is an increasing function of population density.

Analysis of a lottery competition model with limited nutrient availability

How a plant species utilizes a limited nutrient is important for its survival. The purpose of this work is to examine how nutrient utilization mechanisms (for seed production) affect the coexistence of competing plant species. We construct a revised lottery model that uses one of three possible kinds of nutrient utilization functions. In all cases the models suggest that two species can coexist under certain circumstances, but that three species cannot coexist, at least when the nutrient utilization functions are continuous functions of nutrient uptake. However, in the discontinuous case three species can coexist in a state of sustained oscillations. The results suggest that one need pay close attention to the differences in the nutrient utilization mechanisms among competing plant species in order to ascertain the competitive outcome.

What can Invasion Analyses Tell us about Evolution under Stochasticity in Finite Populations?

The geometric mean of fitness is considered to be the main indicator of evolutionary change in stochastic models. However, this measure was initially derived for models with infinite population sizes, where the long-term evolutionary behavior can be described with certainty. In this paper we begin an exploration of the limitations and utility of this approach to evolution in finite populations and discuss alternate methods for predicting evolutionary dynamics. We reanalyze a model of lottery competition under environmental stochasticity by including population finiteness, and show that the geometric mean predictions do not always agree with those based on the fixation probability of rare alleles. Further, the fixation probability can be inserted into adaptive dynamics equations to derive the mean state of the population. We explore the effects of increasing population size on these conclusions through simulations. These simulations show that for small population sizes the fixation probability accurately predicts the course of evolution, but as population size becomes large the geometric mean predictions are upheld. The two approaches are reconciled because the time scale on which the fixation probability approach applies becomes very large as population size grows.

Trade‐offs and Spatial Life‐History Strategies in Classical Metapopulations

The metapopulation concept dichotomizes space into the local scale of an ephemeral patch and the broader scale of the persistent multipatch system. Here, we consider how the "best" (i.e., optimal or noninvasible) life history of asexually reproducing organisms might address this dichotomy along environmental gradients via shifts in two key trade-offs. The expansion-survival trade-off expresses the relation between the combined growth and propagule production rate and the mortality rate. The accumulation-export trade-off partitions expansion into a local accumulation of growth plus propagules retained within the patch and the potential-colonist propagules dispersed to other patches, although the dispersal linkages among patches are assumed to be weak (a characteristic of "classical" metapopulations). We identify the best life histories along gradients of productivity, stress, and patch extinction rates for a metapopulation with and without lottery or overgrowth competition, and we compare them with results for an isolated immortal patch. The two trade-offs interact in determining best life histories, but this effect is generally small, supporting the validity of studies addressing the trade-offs separately. The accumulation-export trade-off responds strongly to the three gradients, increasing export with productivity and with patch extinction rate when this rate is high but decreasing export with higher stress; the expansion-survival trade-off increases expansion with productivity but fails to respond to stress and patch extinction rate gradients, except when the other trade-off does not occur. By linking the trade-offs to life-history strategies (i.e., colonization, exploitation, and tolerance), we separate strategies from phenomenology (i.e., from export, accumulation, and survival) along the gradients.

Population cycles can maintain foraging polymorphism

The maintenance of genetic variability in morphological traits that affect fitness is poorly understood. We present a simple Mendelian model of genetic traits affecting foraging efficiency in grazing ungulates, based on a trade–off between rates of energy extraction at low versus high levels of plant abundance. The model suggests that variation in foraging efficiency could be maintained via lottery competition arising as a direct consequence of dynamically unstable interactions between consumers and their food resources. Lottery competition is a plausible mechanism for explaining wide variability in foraging efficiency, such as that documented in unstable Soay sheep populations on the St Kilda archipelago.

Ecological diversity and resilience of Mediterranean vegetation to disturbance

SummaryIn the Mediterranean region, plant communities are highly diverse with high total and local species richness, and a high spatial heterogeneity. They are also highly resilient to disturbance, which has been related to their evolutionary history of disturbance, and conceptually, although without formal proof, to their high ecological diversity. These ideas take on a new importance in the context of global change. In order to predict potential effects of future land use change, mechanisms underlying the resilience of ecosystems need to be understood. However, a review of the recent literature shows that confusion abounds as to the nature and measurement of resilience. In this paper we present a brief conceptual and methodological clarification and propose avenues for the analysis of mechanisms underlying the relationships between diversity and resilience, using Mediterranean ecosystems as an example.In Mediterranean ecosystems, rapid recovery from fire, soil disturbance and grazing has been attributed to two complementary causes. Firstly, disturbances often modify species relative abundances rather than composition, and recovery only involves the return to initial abundances. Secondly, life histories of dominant life forms in Mediterranean communities include efficient regeneration strategies that allow for recovery from dormant seeds or buds. In this paper, I use experimental results obtained in abandoned agricultural fields of southern France to investigate the mechanisms underlying the resilience of Mediterranean herbaceous communities to soil disturbance. These suggest that ecological diversity contributes to resilience in at least three ways.1.Post‐disturbance dynamics involve shifts in abundances of response groups to disturbance.2.Within response groups, processes of lottery competition account for the dynamic maintenance of numerous species.3.At the landscape scale, the fine grained distribution of communities at different successional stages allows for patch dynamics to operate with dispersal of species between patches.Further progress in the understanding of the relationships between ecological diversity and resilience of Mediterranean ecosystems can be achieved along two main avenues. Firstly, resilience of experimentally manipulated communities with differing levels of diversity needs to be assessed. Secondly, comparisons of those experiments across mediterranean‐climate regions with different evolutionary disturbance histories need to be coordinated.

Coexistence and Community Structure of Tropical Trees in a Hawaiian Montane Rain Forest

We measured the diameter at breast height of all trees and shrubs 25 meters in height, including standing dead trees, on 68 0.04-hectare study plots in a montane, subtropical rain forest on Mauna Loa, Hawai'i. The canopy species consisted of 88 percent Metrosideros polymorpha (ohia) and 12 percent Acacia koa (koa). Negative associations were found between the densities of koa and ohia, the density of koa and the total basal area of ohia, and the total basal areas of koa and ohia. The two-species lottery competition model, a stochastic model in which the coexistence of two species in a space-limited community results from temporal variation in recruitment and death rates, predicts a quadratic-beta distribution for the proportion of space occupied by each species. A discrete version of the quadraticbeta distribution, the quadratic-beta binomial distribution, was fit to the live koa and ohia densities and assessed with goodness-of-fit tests. Likelihood ratio tests provided evidence that the mean adult death rates of the two species were equal but that the relative competitive abilities of the two species favored ohia. These tests were corroborated by a contingency table analysis of death rates based on standing dead trees and growth rate studies which report that koa grows much faster than ohia. The lottery model predicts a positive covariance between death rates and ohia recruitment when mean death rates are equal and koa has a higher growth rate than ohia. We argue that the competitive advantage of ohia is due to its superior dispersal ability into large gaps, which would yield the positive covariance described above, and it is this positive covariance term that skews the occupation of space in favor of ohia.

Limits to the Similarity of Competitors Under Hierarchical Lottery Competition

Previous articleNext article No AccessNotes and CommentsLimits to the Similarity of Competitors Under Hierarchical Lottery CompetitionPeter A. AbramsPeter A. Abrams Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The American Naturalist Volume 148, Number 1Jul., 1996 Published for The American Society of Naturalists Article DOIhttps://doi.org/10.1086/285920 Views: 12Total views on this site Citations: 19Citations are reported from Crossref Copyright 1996 The University of ChicagoPDF download Crossref reports the following articles citing this article:Barbara Bauer, Emilio Berti, Remo Ryser, Benoit Gauzens, Myriam R. 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Phenological Pattern of Tree Regeneration in a Model for Forest Species Diversity

A phenological segregation model of forest tree dynamics is studied, which has previously proposed to explain the observed gradient of species diversity along the length of an unfavorable season (e.g., winter or dry months). The assumptions are: the coexistyence of many species in a tropical rain forest is based on lottery competition. With gap formation occurring throughout the year, a season unfavorable for growth causes a peak regeneration opportunity in the beginning of the growing season. The synchronization of the regeneration opportunity jeopardizes the coexistence of many similar species. The model has the globally stable equilibrium, where the curve of regeneration opportunity is best matches by a weighted average of regeneration ability (or niche) curves calculated using the species composition. If the candidate species have the same niche width and different peak dates, the remaining community includes several distinct groups of species with a similar peak regeneration date. If the candidate species differ also in niche width, the equilibrium community includes broad niche species with the peak in the middle of the growing season and narrow niche species with the peak either in the beginning or in the end of the growing season.

Life Histories with Lottery Competition in a Stochastic Environment: ESSs which Do Not Prevail

We present examples for multiple ESSs, for ESSs which cannot invade other established strategies, and for ESSs which cannot be approached gradually in a lottery model with randomly fluctuating adult survival. In case of multiple ESSs the outcome of the evolution may depend not only on the initial population but also on the historical sequence of mutations.