Emigration Probability Research Articles

A multistate mark–recapture approach to characterize stream fish movement at multiple spatial scales

We studied movement of a native salmonid, white-spotted char (Salvelinus leucomaenis), in a 1-km tributary in northern Hokkaido, Japan, in May–July 2018. Based on physical mark–recapture of 501 unique individuals and detection by mobile PIT antenna over monthly intervals, a majority of fish (70%–80%) stayed within 60 m of previously released locations, demonstrating what appeared to be restricted movement patterns. However, fixed PIT antenna data showed that as much as 17% of marked individuals emigrated from the study area during the 2-month study period. Probability of emigration did not depend on where in the 1-km segment individuals had been released, indicating that emigration likely represented long-distance movement. Once emigrants made a decision to emigrate, they left the tributary within 1–3 median days by moving downstream in a unidirectional manner, based on detections at a total of three antenna arrays deployed throughout the tributary. Our multiscale analysis provided strong support for co-existence of short- and long-distance movement patterns, and we conclude that movement data at multiple spatial scales complement each other to characterize population-scale movement.

Integrating an individual-based model with approximate Bayesian computation to predict the invasion of a freshwater fish provides insights into dispersal and range expansion dynamics

Short-distance dispersal enables introduced alien species to colonise and invade local habitats following their initial introduction, but is often poorly understood for many freshwater taxa. Knowledge gaps in range expansion of alien species can be overcome using predictive approaches such as individual based models (IBMs), especially if predictions can be improved through fitting to empirical data, but this can be challenging for models having multiple parameters. We therefore estimated the parameters of a model implemented in the RangeShifter IBM platform by approximate Bayesian computation (ABC) in order to predict the further invasion of a lowland river (Great Ouse, England) by a small-bodied invasive fish (bitterling Rhodeus sericeus). Prior estimates for parameters were obtained from the literature and expert opinion. Model fitting was conducted using a time-series (1983 to 2018) of sampling data at fixed locations and revealed that for 5 of 11 model parameters, the posterior distributions differed markedly from prior assumptions. In particular, sub-adult maximum emigration probability was substantially higher in the posteriors than priors. Simulations of bitterling range expansion predicted that following detection in 1984, their early expansion involved a relatively high population growth rate that stabilised after 5 years. The pattern of bitterling patch occupancy was sigmoidal, with 20% of the catchment occupied after 20 years, increasing to 80% after 30 years. Predictions were then for 95% occupancy after 69 years. The development of this IBM thus successfully simulated the range expansion dynamics of this small-bodied invasive fish, with ABC improving the simulation precision. This combined methodology also highlighted that sub-adult dispersal was more likely to contribute to the rapid colonisation rate than expert opinion suggested. These results emphasise the importance of time-series data for refining IBM parameters generally and increasing our understanding of dispersal behaviour and range expansion dynamics specifically.

Modeling the effects of density dependent emigration, weak Allee effects, and matrix hostility on patch-level population persistence.

The relationship between conspecific density and the probability of emigrating from a patch can play an essential role in determining the population-dynamic consequences of an Allee effect. In this paper, we model a population that inside a patch is diffusing and growing according to a weak Allee effect per-capita growth rate, but the emigration probability is dependent on conspecific density. The habitat patch is one-dimensional and is surrounded by a tuneable hostile matrix. We consider five different forms of density dependent emigration (DDE) that have been noted in previous empirical studies. Our models predict that at the patch-level, DDE forms that have a positive slope will counteract Allee effects, whereas, DDE forms with a negative slope will enhance them. Also, DDE can have profound effects on the dynamics of a population, including producing very complicated population dynamics with multiple steady states whose density profile can be either symmetric or asymmetric about the center of the patch. Our results are obtained mathematically through the method of subsuper solutions, time map analysis, and numerical computations using Wolfram Mathematica.

Abundance and residency dynamics of the Indo‐Pacific humpback dolphin, Sousa chinensis, in the Dafengjiang River Estuary, China

AbstractRobust population size estimates are essential for informing population conservation status. Residency dynamics show population habitat use through time. Population size of Indo‐Pacific humpback dolphins (Sousa chinensis) has been extensively investigated in Chinese waters, but their residency dynamics are rarely known. Mark‐recapture analysis based on photo‐identification records was applied to humpback dolphins in the Dafengjiang River Estuary habitat, one of the key habitats in the northern Beibu Gulf, China. Movement analyses based on lagged identification rate indicated the humpback dolphins spent, on average, 78.5 days inside and 46.9 days outside the survey area. Within the study area, the humpback dolphin abundance was 83 identifiable dolphins. A total of 353–430 humpback dolphins, estimated by POPAN modeling, were involved in this fluid habitat‐use dynamic. Robust Design analysis showed strong seasonality in humpback dolphin abundance and emigration probability, implying a movement‐ and habitat‐use pattern likely associated with spatiotemporal distribution of oceanographic characteristics and prey occurrences. Population surveys and conservation measures currently conducted in Chinese waters seldom consider seasonality in movements between habitat patches, which can be addressed by genetic analyses across habitats and cross‐matching photo‐identification records among neighboring habitats.

Departure Decisions of a Migratory Passerine, the Common Reed-Warbler Acrocephalus scirpaceus, in Relation to Fuel Load and Geographical Barrier Proximity

Research on the stopover ecology of migrant birds has examined the role of multiple factors, both intrinsic and extrinsic, on departure decisions. However, a single factor may influence stopover decisions differentially, depending on the relative geographic location of a stopover site within the flyway and the expectation of ecological challenges ahead. For instance, actual fuel load may have a decisive influence on departure decisions before a crossing of major geographical barriers, such as seas or deserts, but may be less important when crossing vast continental areas offering plenty of opportunities to refuel. The aim here was to test whether the relative influence of fuel load on departure decisions of the Common Reed-warbler Acrocephalus scirpaceus, a long-distance migrant songbird, varies in relation to proximity to a geographical barrier: the sea expanse between Iberia and Africa. We expected that departure from southern Iberian stopover sites would be highly influenced by fuel load, since migrants would not fly to Africa until they had sufficient fuel to cross the sea. We used Cormack-Jolly-Seber (CJS) models to test for the effect of fuel load on emigration (departure) probability from a number of stopover sites situated in northern and southern Iberia during the autumn migration period. Reed-warblers stopping over for longer than one day were more likely to depart if they were in northern Iberia than in southern sites. Moreover, large fuel loads promoted emigration from stopover sites in northern, but not in southern, Iberia. Therefore, we found no evidence supporting the hypothesis that Reed-warblers wait until they acquire large fuel loads before leaving their stopover sites near the edge of the barrier. This study shows that the same parameters may not act in the same way along migration route, in particular in relation to geographical barrier proximity.—Andueza, M., Barba, E., Cuenca, D., Laso, M., Unamuno, E., Unanue, A.,Valkenburg, T., Genovart, M. & Arizaga, J. (2020). Departure decisions of a migratory passerine, the Common Reed-warbler Acrocephalus scirpaceus, in relation to fuel load and geographical barrier proximity.

Male residency and dispersal triggers in a seasonal breeder with influential females

Males in female-philopatric social groupings leave their natal groups to pursue successive reproductive opportunities in one or more other groups. In vervet monkeys, Chlorocebus pygerythrus, adult males coexist and physical eviction is not a driver of male movement. Migratory decisions are expected to turn on an evaluation of future reproductive opportunity, as indexed principally by local operational sex ratio and relative competitive ability. Although vervet males' reproductive success is correlated with dominance, they are distinctive in that the attainment of rank is contingent on integration into female sociospatial networks and we expect decisions about continued residency to reflect this. We used 8 years' data from three groups to confirm that male dispersal between groups is seasonal in our population, with a peak that is coterminous with androgen levels and precedes peak mating and conception by 4 weeks. The average length of completed residency was 459 days, with an increase in the logged rate of departure after 1428 days, which is 150 days longer than the estimated modal age at first conception by putative daughters. There were positive correlations between a male's initial and highest rank, and between his highest rank and the length of time to reach it. We found that a male's residency was positively and independently associated with his highest achieved rank and both his grooming centrality and proximity degree. Additionally, increasing rank and proximity degree also had positive effects on residency length subsequent to the attainment of his highest rank. The probability of emigration was associated negatively with both female number and grooming centrality scores. We conclude that emigration from a group is linked to male rank attainment and mediated by a male's integration into female sociospatial networks. We found no evidence that emigration preceded the sexual maturity of putative daughters.

Emigration of hatchery‐reared Pallid Sturgeon, Scaphirhynchus albus (Forbes and Richardson), through a Missouri River dam

AbstractThe middle Missouri River (MMR; Fort Randall Dam, SD to Gavins Point Dam, NE‐SD) is stocked with hatchery‐reared pallid sturgeon, Scaphirhynchus albus (Forbes and Richardson), from upper Missouri River broodstock to aid recovery of this federally endangered species. Emigration of these fish through Gavins Point Dam restores genetic connectivity that likely existed pre‐impoundment but could lead to outbreeding depression in the future. Recapture data of hatchery‐reared pallid sturgeon stocked in the MMR were evaluated to improve understanding of pallid sturgeon emigration. From 2004 to 2015, 219 emigrants were caught: 4 stocked at age ≥2 years and 215 stocked at age ≤1 year. Emigration of the 2001‐2007 year classes stocked at age 1 was a consistent phenomenon and appeared higher than emigration of year classes stocked at ages 2–3. Little evidence suggested emigration was associated with an unusually high‐water event in 2011. The annual emigration probability of individuals stocked at age 1 estimated from multi‐state mark–recapture models was 0.05 [95% confidence interval = 0.04–0.06] for fish ages ≥1 year. This study suggests that alterations to stocking practices (e.g. stocking age) may affect emigration rates and, therefore, connectivity among pallid sturgeon populations.

Environmentally mediated reproductive success predicts breeding dispersal decisions in an early successional amphibian

Dispersal is a central mechanism in ecology and evolution. Dispersal evolution is driven by a trade-off between costs and benefits, which is influenced by interindividual variability and local environmental conditions (context-dependent dispersal). Many studies have investigated how dispersal decisions may be influenced by environmental factors, including density, predation and interspecific competition. Yet few have attempted to examine how habitat disturbance may affect the dispersal process in spatially structured populations. In early successional species, one might expect individuals to adjust their dispersal decisions based on two main factors that potentially have an influence on reproductive success: patch size and the level of patch disturbance. In this study, we examined how these two factors affect breeding success and dispersal decisions in an early successional amphibian, the yellow-bellied toad, Bombina variegata. To this end, we used capture–recapture data collected on a spatially structured population occupying 28 breeding patches. We took advantage of recent developments in multievent capture–recapture models to detect signs of context-dependent dispersal. The results revealed that the probability of successful reproduction and the number of newly metamorphosed individuals increased with both the size and the proportion of disturbance of a patch. In addition, our results showed that the factors affecting breeding success also influenced breeding dispersal probability. Large patch size negatively influenced emigration probability; in contrast, it positively influenced immigration probability. Equally, higher disturbance had a strong negative influence on emigration probability and slightly positively affected immigration probability. These findings strongly suggest that individuals make context-dependent dispersal decisions, adjusted to maximize future fitness prospects in a patch, allowing them to better cope with rapid changes in environmental conditions resulting from the ecological succession process. This opens new areas of potential research into the role of dispersal in organism specialization along an ecological succession gradient.

Matching habitat choice promotes species persistence under climate change

Species may survive under contemporary climate change by either shifting their range or adapting locally to the warmer conditions. Theoretical and empirical studies recently underlined that dispersal, the central mechanism behind these responses, may depend on the match between an individuals’ phenotype and local environment. Such matching habitat choice is expected to induce an adaptive gene flow, but it now remains to be studied whether this local process could promote species’ responses to climate change. Here, we investigate this by developing an individual‐based model including either random dispersal or temperature‐dependent matching habitat choice. We monitored population composition and distribution through space and time under climate change. Relative to random dispersal, matching habitat choice induced an adaptive gene flow that lessened spatial range loss during climate warming by improving populations’ viability within the range (i.e. limiting range fragmentation) and by facilitating colonization of new habitats at the cold margin. The model even predicted range contraction under random dispersal but range expansion under optimal matching habitat choice. These benefits of matching habitat choice for population persistence mostly resulted from adaptive immigration decision and were greater for populations with larger dispersal distance and higher emigration probability. We also found that environmental stochasticity resulted in suboptimal matching habitat choice, decreasing the benefits of this dispersal mode under climate change. However population persistence was still better under suboptimal matching habitat choice than under random dispersal. Our results highlight the urgent need to implement more realistic mechanisms of dispersal such as matching habitat choice into models predicting the impacts of ongoing climate change on biodiversity.

Universal infant health interventions and young adult outcomes.

Three recent studies have documented short- and long-run benefits of early-infancy health interventions in Norway, Sweden, and Denmark: Universal nurse home visiting (NHV) and well-baby center care decreased infant mortality and positively impacted long-run survival (DK, S), morbidity (DK, N), and educational and labor market outcomes (N). Using Danish conscription data, this paper examines intermediate outcomes to assess both potential mechanisms and the importance of selective survival for the long-run health effects of NHV. We do not find strong effects of NHV for young adult's height or obesity status, but we find that NHV increases treated individuals' probability of emigration. As emigrants in our sample are positively selected and as they are not part of the samples used in long-run analyses, this finding suggests that the established long-run health benefits of NHV may be lower bounds.

Estimating population parameters of longsnout seahorses, Hippocampus reidi (Teleostei: Syngnathidae) through mark-recapture

ABSTRACT Estimating population parameters is essential for understanding the ecology of species, which ultimately helps to assess their conservation status. The seahorse Hippocampus reidi is directly exposed to anthropogenic threats along the Brazilian coast, but the species still figures as Data Deficient (DD) at IUCN’s Red List. To provide better information on the ecology of this species, we studied how population parameters vary over time in a natural subtropical environment. By combing mark-recapture models for open and closed populations, we estimated abundance, survival rate, emigration probability, and capture probability. We marked 111 individuals, which showed a 1:1 sex ratio, and an average size of 10.5 cm. The population showed high survival rate, low temporary emigration probability and variable capture probability and abundance. Our models considering relevant biological criteria illuminate the relatively poorly known population ecology and life history of seahorses. It is our hope that this study inspires the use of mark-recapture methods in other populations of H. reidi in a collective effort to properly assess their conservation status.

Community distance sampling models allowing for imperfect detection and temporary emigration

AbstractRecent developments of community abundance models (CAMs) enable us to analyze communities subject to imperfect detection. However, existing CAMs assume spatial closure, that is, that individuals are always present in the sampling plots, which is often violated in field surveys. Violation of this assumption, such as in the presence of spatial temporary emigration, can lead to the underestimates of detection probability and overestimates of population densities and diversity metrics. Here, we propose a model that simultaneously accommodates both temporary emigration and imperfect detection by integrating CAMs and a form of hierarchical distance sampling for open populations. Expected values of species richness are obtained via the summation of occupancy (or incidence) probabilities, based on species‐level densities, across all species of the community. Simulations were used to examine the effects of spatial temporary emigration on the estimation of biological communities. We also applied the proposed model to empirical data and constructed area‐based rarefaction curves accounting for temporary emigration. Simulation experiments showed that temporary emigration can decrease the local species richness (α diversity) based on densities and increase the species turnover (β diversity). Raw species counts can overestimate or underestimate α diversity in the presence of temporary emigration, but the specific biases depend on the values of detection and emigration probabilities. Our newly proposed model yielded unbiased estimates of α, β, and γ diversity in the presence of temporary emigration. The application to empirical data suggested that accounting for temporary emigration lowered area‐based rarefaction curves because availability probabilities of individual species were estimated to be <1. Temporary emigration prevails in field surveys and has broad significance for understanding the ecology and function of biological communities and separation of imperfect detection and temporary emigration resolves long‐standing issues in the use of count data. We therefore suggest that the consideration of temporary emigration would contribute to understanding the nature and role of biological communities.

Migrációs regionális profilok vizsgálata Magyarországon, nagymintás adatbázison

Kutatásunkban – 2013 és 2016 között közel 6000 fő megkérdezésén alapuló kérdőíves adatgyűjtéssel – válaszokat kerestünk arra a kérdésre, hogy vajon előrejelezhető- e a lakosság migrációs szándéka. Milyen tényezők befolyásolják azt a döntést, hogy valaki el szeretné hagyni az országot – függetlenül attól, hogy kényszerű, kényelmi, praktikus vagy érzelmi okokból teszi azt. Meg lehet-e mondani, hogy milyen tulajdonságokkal rendelkeznek azok az emberek, akik inkább hajlamosak a kivándorlásra, és mi jellemzi azokat, akik lokálpatrióta érzelmeik miatt nem válnak emigránssá.Tanulmányunk első részében áttekintjük a 20. és 21. századi magyarországi kivándorlási hullámok kiváltó okait, az emigránsok társadalmi helyzetét, demográfiai jellemzőit, a kibocsátó területeket és a célországokat. A történeti áttekintés célja, hogy a napjainkban vándorbotot fogók és a korábbi exodusok résztvevői közötti hasonlóságokat, illetve különbözőségeket feltárjuk. Megkíséreljük meghatározni, hogy objektív és szubjektív tulajdonságok mennyiben járulnak hozzá ahhoz, hogy valaki külföldre készüljön hosszabb vagy rövidebb időre, illetve mennyivel nagyobb az esélye az itthon maradásnak. A vizsgált tényezők alapján bemutatjuk a régiók közötti különbségeket, valamint azt, hogy a heterogén földrajzi, gazdasági, demográfiai tulajdonságokkal rendelkező lakosok kivándorlási hajlandósága milyen eltéréseket mutat.A fenti kérdések megválaszolása nem egyszerű. Nemcsak azért, mert összetettségüknél és társadalmi jellegüknél fogva sem a szándék, sem az azt befolyásoló tényezők nem mérhetők egzakt módon, de azért sem, mert a megfelelő módszertan megválasztása is számos további kérdést vet fel.

Performance of multistate mark–recapture models for temporary emigration in the presence of survival costs

Abstract Temporary emigration is widespread in animals and plants and has important implications for ecological processes, evolution and the conservation of species. It is increasingly studied with capture–mark–recapture (CMR) models. Temporary emigration provides particular challenges to CMR analyses if it involves movement to an unobservable state. A multistate model in which individuals may move between an “observable” and an “unobservable” state (called TE model) was developed for such cases. The model assumes equal survival probability in both states. This assumption may be violated, especially if temporary emigration involves trade‐offs between survival and reproduction. A comprehensive assessment of the effects of unequal survival probability on power to detect temporary emigration and on bias and precision of estimates is still needed to understand the applicability and limits of the model. We assessed power to detect temporary emigration for four goodness‐of‐fit tests and evaluated bias and precision of estimates for the TE model and for its combination with a robust design. Our simulation study, based on 16,650 parameter combinations, shows that temporary emigration is more challenging than currently usually acknowledged. The Tests 2.CT and 2.C are largely independent of the difference in survival probability between the states. In contrast, Test 3.SR is sensitive to the difference in survival probability but also to emigration probability. Tests 2.C and 2.CT have high power if a large part of the population temporarily emigrates and a large fraction of the individuals return on the next capture occasion. Under this condition, bias is low and precision adequate even if the assumption of equal survival probability is violated. Bias and precision are also satisfactory if the assumption is met but unsatisfactory or unreliable for the remaining parameter space. We conclude that the uncertainties whether an appropriate model was selected and whether the estimates from the selected model may be biased should be clearly communicated and that every endeavour should be made to make the unobservable state observable.

Coevolution of patch-type dependent emigration and patch-type dependent immigration

The three phases of dispersal - emigration, transfer and immigration - are affecting each other and the former and latter decisions may depend on patch types. Despite the inevitable fact of the complexity of the dispersal process, patch-type dependencies of dispersal decisions modelled as emigration and immigration are usually missing in theoretical dispersal models. Here, I investigate the coevolution of patch-type dependent emigration and patch-type dependent immigration in an extended Hamilton–May model. The dispersing population inhabits a landscape structured into many patches of two types and disperses during a continuous-time season. The trait under consideration is a four dimensional vector consisting of two values for emigration probability from the patches and two values for immigration probability into the patches of each type. Using the adaptive dynamics approach I show that four qualitatively different dispersal strategies may evolve in different parameter regions, including a counterintuitive strategy, where patches of one type are fully dispersed from (emigration probability is one) but individuals nevertheless always immigrate into them during the dispersal season (immigration probability is one). I present examples of evolutionary branching in a wide parameter range, when the patches with high local death rate during the dispersal season guarantee a high expected disperser output. I find that two dispersal strategies can coexist after evolutionary branching: a strategy with full immigration only into the patches with high expected disperser output coexists with a strategy that immigrates into any patch. Stochastic simulations agree with the numerical predictions. Since evolutionary branching is also found when immigration evolves alone, the present study is adding coevolutionary constraints on the emigration traits and hence finds that the coevolution of a higher dimensional trait sometimes hinders evolutionary diversification.

The evolution of density-dependent dispersal under limited information

For an increasing number of species dispersal decisions have been shown to depend on local population density. This implies that organisms perceive – with sufficient accuracy – information about population density. However, research on the fitness value of such information, the adequate use of imprecise information, and how information use affects overall dispersal has only just started.A critical issue in such research necessarily concerns the adequate rule linking an individual's population density estimate to its readiness to emigrate; a spectrum of such rules has been proposed in the past. We use three prevalent rules and one rule specifically derived for situations of incomplete information to demonstrate that the adequacy of each rule strongly depends on the accuracy of information about population density: Simple bang–bang (threshold) behavior performs best if information is highly inaccurate, whereas a saturating response function (dispersal propensity gradually increasing with population density) out-competes all other strategies when individuals can estimate density accurately. The decision rule as well as the precision of information significantly influence average emigration probabilities establishing in metapopulations. Our results show that use of inadequate rules in models of dispersal evolution may lead to false dispersal decisions. Based on this analysis we present a rule that allows approximating an adequate dispersal response at the population level even when individuals possess incomplete information about local density. We conclude that individuals should generally invest little into the acquisition of (accurate) information even if such acquisition is associated with only small costs.

Formulating spread of species with habitat dependent growth and dispersal in heterogeneous landscapes

Habitat heterogeneity can have profound effects on the spreading dynamics of invasive species. Using integro-difference equations, we investigate the spreading dynamics in a one-dimensional heterogeneous landscape comprising alternating favourable and unfavourable habitat patches or randomly generated habitat patches with given spatial autocorrelation. We assume that population growth and dispersal (including emigration probability and dispersal distance) are dependent on habitat quality. We derived an approximation of the rate of spread in such heterogeneous landscapes, suggesting the sensitivity of spread to the periodic length of the alternating favourable and unfavourable patches, as well as their spatial autocorrelation. A dispersal-limited population tends to spread faster in landscapes with shorter periodic length. The spreading dynamics in a heterogeneous landscape was found to be not only dependent on the availability of favourable habitats, but also the dispersal strategy. Estimates of time lag before detection and the condition for boom-and-bust spreading dynamics were explained. Furthermore, rates of spread in heterogeneous landscapes and corresponding homogeneous landscapes were compared, using weighted sums of vital rates.

On the evolution of patch-type dependent immigration

Empirical studies of dispersal indicate that decisions to immigrate are patch-type dependent; yet theoretical models usually ignore this fact. Here, we investigate the evolution of patch-type dependent immigration of a population inhabiting and dispersing in a heterogeneous landscape, which is structured by patches of low and high reward. We model the decision to immigrate in detail from a mechanistic underpinning. With the methods of adaptive dynamics, we derive both analytical and numerical results for the evolution of immigration when life-history traits are patch-type dependent. The model exhibits evolutionary branching in a wide parameter range and the subsequent coevolution can lead to a stable coexistence of a generalist, settling in patches of any type, and a specialist that only immigrates into patches of high reward. We find that individuals always settle in the patches of high reward, in which survival until maturation, relative fecundity and emigration probability are high. We investigate how the probability to immigrate into patches of low reward changes with model parameters. For example, we show that immigration into patches of low reward increases when the emigration probability in these patches increases. Further, immigration into patches of low reward decreases when the patches of high reward become less safe during the dispersal season.

The Adequate Use of Limited Information in Dispersal Decisions.

Several theoretical studies predict that informed (e.g., density-dependent) dispersal should generally result in lower emigration probabilities than uninformed (random) dispersal. In a 2012 publication, Bocedi et al. surprisingly come to the opposite conclusion. For most scenarios investigated, they found that noninformed and, particularly, less precisely informed dispersers evolve lower dispersal propensity than dispersers following "fully informed" strategies. Further, they observed that fully informed individuals evolved a steplike dispersal response-a response to local density that contradicts theoretical predictions for organisms with nonoverlapping generations. Replicating the individual-based simulations of Bocedi et al. we find that these conclusions are not justified and are based on a misinterpretation of simulation results: their controversial findings result from (i) a misleading use of the term "population density," (ii) a misconception concerning the true informative value of the different decision criteria they compared, and (iii) arbitrary constraints on the evolution of the dispersal response that prevented the evolution of strategies that allow for a fitness-enhancing utilization of available information.

Models of Dispersal Evolution Highlight Several Important Issues in Evolutionary and Ecological Modeling.

Previous results showing that lack of information on local population density leads to higher emigration probabilities in unpredictable environments but to lower emigration probabilities in constant or highly predictable scenarios have recently been challenged by Poethke et al. By reimplementing both our model and that of Poethke and colleagues, we demonstrate that our original results indeed hold to the presented critiques and do not contradict previous findings. The comment by Poethke and colleagues does, however, present potentially intriguing results suggesting that negative density-dependent dispersal evolves under white noise for some model formulations. Here, through intermodel comparison, we seek to better understand the source of the differences in results obtained in our study and theirs. We conclude that the apparent negative density dependence reported by Poethke et al. is effectively density independence and that the shape of the reaction norm they obtain is a model artefact. Further, this response provides an opportunity to elaborate on some important issues in evolutionary and ecological modeling regarding (i) the importance of carefully considering different models' assumptions in comparisons among models, (ii) the need to consider the role of stochasticity and uncertainty when presenting and interpreting results from stochastic individual-based models, (iii) the adequate choice of the underlying ecological model that creates the selective pressures determining the evolution of behavioral reaction norms, and (iv) the appropriate choice of mutation models.