Variation In Dispersal Behaviour Research Articles

Interpopulation variation in dispersal behavior of fat minnow Rhynchocypris oxycephalus jouyi juveniles inhabiting fragmented habitats.

In many organisms, including fishes, downstream dispersal is often phenotype-dependent. Phenotype-dependent downstream dispersal can generate evolutionary pressure via spatial sorting, which non-randomly removes phenotypes enhancing downstream dispersal from upstream populations. Spatial sorting due to downstream dispersal could accumulate in fish populations in above-barrier habitats to which dispersed individuals cannot return, resulting in functional traits that reduce downstream dispersal. This evolutionary mechanism may be more important in smaller above-barrier habitats where downstream emigration occurs over shorter dispersal distances. This study observed the dispersal behavior of fat minnow Rhynchocypris oxycephalus jouyi juveniles in an experimental tank to examine whether juveniles from small above-barrier habitats show more behaviors favorable for reducing downstream dispersal than those from large above-barrier habitats. Juveniles from small above-barrier habitats avoided downstream dispersal for longer durations than those from large above-barrier habitats, but there was no difference in the frequency of ascending attempts. These results support the notion that behavioral traits of juveniles in small above-barrier populations have been refined by spatial sorting to reduce downstream dispersal. The finding that interpopulation variation in dispersal behavior occurred only for certain dispersal directions implies that the behavioral consequences of habitat fragmentation are more complex than previously assumed.

Movement of white‐tailed deer in contrasting landscapes influences management of chronic wasting disease

AbstractChronic wasting disease (CWD) continues to expand in distribution and prevalence across North America. Upon detection, either for the first time in a novel area or in a region with an existing outbreak, wildlife management agencies are tasked with responding to mitigate the disease. This response often entails creation or modification of a management zone with modified rules and regulations that support an agency's disease management plan. To guide the process of creating an appropriately sized CWD management zone, assuming that wild deer movements are a major risk factor for disease spread, we used data from global positioning system (GPS)‐collared white‐tailed deer (Odocoileus virginianus) in southeastern Minnesota and southcentral Pennsylvania, USA, between 2018 and 2021 to estimate long‐distance movements associated with dispersal and migratory behaviors. These contrasting study areas with active CWD outbreaks permitted an evaluation of deer movement dynamics in different parts of their range. We quantified the proportion, distribution, timing, and orientation of dispersing and migratory deer. We observed 21% of female and 58% of male yearlings disperse from their apparent natal home range in Minnesota, while in Pennsylvania 4% of female and 68% of male yearlings dispersed. We also documented 20% of females and 6% of males migrated between seasonal home ranges in Minnesota, while in Pennsylvania no females and 5% of males migrated. The average distance deer dispersed or migrated in Minnesota was 20 km and 11 km, respectively, while in Pennsylvania male deer dispersed only about 4 km. Both sexes in Minnesota tended to disperse in a consistent, westerly direction; however, there was no directional preference observed for migratory deer or for dispersing deer in Pennsylvania. We found differences between natal and adult home range size for both sexes in Minnesota but not for males in Pennsylvania. Our results identify the considerable variability in dispersal and migration dynamics of white‐tailed deer in disparate landscapes, which is important to agencies managing CWD. We summarize the distribution of these movements and suggest agencies use this information to help make decisions about optimal management zone size. We suggest the development of formalized assessments of the tradeoffs associated with optimizing decisions about creation of CWD management zones across white‐tailed deer populations that exhibit variation in dispersal behavior and suggest careful evaluation to avoid using an arbitrary size or shape to create disease management zones.

Community context and dispersal stochasticity drive variation in spatial spread.

Dispersal is a key process in shaping species spatial distributions. Species interactions and variation in dispersal probabilities may jointly influence species spatial dynamics. However, many studies examine dispersal as a neutral process, independent of community context or intraspecific variation in dispersal behaviour. Here, we use controlled, replicated communities of two Tribolium species (T. castaneum and T. confusum) to examine how intraspecific variation in dispersal behaviour and community context influence dispersal dynamics in simple experimental landscapes composed of homogeneous habitat patches. We found considerable individual-level variation in dispersal probability that was unrelated to body size variation. Further, the context of dispersal mattered, as T. castaneum dispersal was reduced in two-species communities, while T. confusum dispersal was unaffected by community composition. Incorporating individual-level variation into a two-species stochastic spatial Ricker model, we provide evidence that individual-level variability in dispersal behaviour results in more variable spatial spread than assuming individuals have the same dispersal probability. Further, interspecific competition resulted in more variable spatial spread. The variability in spatial spread observed in our tightly controlled and replicated experimental system and in our stochastic model simulations points to potential fundamental limitations in forecasting species shifting ranges without considering potential interspecific interactions and demographic variability in dispersal behaviour.

Phenotype-by-environment interactions influence dispersal.

Numerous studies have demonstrated that dispersal is dependent on both disperser phenotype and the local environment. However, there is substantial variability in the observed strength and direction of phenotype- and environment-dependent dispersal. This has been hypothesized to be the result of interactive effects among the multiple phenotypic and environmental factors that influence dispersal. Here, our goal was to test the hypothesis that these interactions are responsible for generating variation in dispersal behaviour. We achieved these goals by conducting a large, 2-year, mark-release-recapture study of the backswimmer Notonecta undulata in an array of 36 semi-natural ponds. We measured the effects of multiple phenotypic (sex and body size) and environmental (population density and sex ratio) factors, on both dispersal probability and dispersal distance. We found support for the hypothesis that interactive effects influence dispersal and produce variability in phenotype- and environment-dependent dispersal: dispersal probability was dependent on the three-way interaction between sex, body mass and population density. Small males displayed strong, positive density dependence in their dispersal behaviour, while large males and females overall did not respond strongly to density. Small notonectids, regardless of sex, were more likely to disperse, but this effect was strongest at high population densities. Finally, the distance dispersed by backswimmers was a negative function of population density, a pattern which we hypothesize could be related to: (a) individuals from high and low density patches having different dispersal strategies, or (b) the effect of density on dispersal capacity. These results suggest that phenotype-by-environment interactions strongly influence dispersal. Since phenotype- and environment-dependent dispersal has different consequences for ecological and evolutionary dynamics (e.g. metapopulation persistence and local adaptation) than random dispersal, interactive effects may have wide-reaching impacts on populations and communities. We therefore argue that more investment should be made into estimating the effects of multiple, interacting factors on dispersal and determining whether similar interactive effects are acting across systems.

Habitat fragmentation drives inter-population variation in dispersal behavior in a Neotropical rainforest bird

Conservation ecology research, management and modeling often assume species-specific fixed traits ignoring intraspecific variation. Dispersal in animals is a heritable trait where intraspecific variation should be common, as it develops via interactions between landscape and behavioral processes. We conducted translocation-radio-tracking experiments and novel-environment tests on a Neotropical rainforest bird (Pyriglena leucoptera, Thamnophillidae) to assess whether dispersal success and exploratory behavior are determined by an individual's population of origin (i.e. fragmented or continuous forest). Based on a model for non-optimal animal movement in human-modified landscapes, we predicted that individuals that evolve or develop in fragmented landscapes, with daily exposure to risky boundary and matrix conditions, would have higher resistance to boundary-crossing and overall increased dispersal success than individuals from continuous habitats. We found that birds from fragmented landscapes were more resistant to cross boundaries and more successful at crossing the matrix relative to birds from continuous forest. Novel-environment tests detected reduced exploratory scores for birds from fragments, suggesting they were slower-explorers, and possibly more thorough in assessing their environment which, in turn, may have enabled more successful matrix transit. Observed behavioral differences can emerge by genetic adaptation or behavioral adjustments. In any case, because P. leucoptera is capable of adaptive behavioral adjustments to fragmentation, gradual landscape changes should be encouraged to minimize the potential for emergence of non-optimal dispersal behaviors in human-modified landscapes.

Spatial Selection and Local Adaptation Jointly Shape Life-History Evolution during Range Expansion.

In the context of climate change and species invasions, range shifts increasingly gain attention because the rates at which they occur in the Anthropocene induce rapid changes in biological assemblages. During range shifts, species experience multiple selection pressures. For poleward expansions in particular, it is difficult to interpret observed evolutionary dynamics because of the joint action of evolutionary processes related to spatial selection and to adaptation toward local climatic conditions. To disentangle the effects of these two processes, we integrated stochastic modeling and data from a common garden experiment, using the spider mite Tetranychus urticae as a model species. By linking the empirical data with those derived form a highly parameterized individual-based model, we infer that both spatial selection and local adaptation contributed to the observed latitudinal life-history divergence. Spatial selection best described variation in dispersal behavior, while variation in development was best explained by adaptation to the local climate. Divergence in life-history traits in species shifting poleward could consequently be jointly determined by contemporary evolutionary dynamics resulting from adaptation to the environmental gradient and from spatial selection. The integration of modeling with common garden experiments provides a powerful tool to study the contribution of these evolutionary processes on life-history evolution during range expansion.

Individual variation in ballooning dispersal by black widow spiderlings: The effects of family and social rearing

Abstract Individual behavioral variation is ubiquitous across taxa and important to understand if we wish to fully use behavioral data to understand the ecology and evolution of organisms. Only recently have studies of individual variation in dispersal behavior become a focus of research. A better understanding of individual variation in dispersal behavior is likely to improve our understanding of population dynamics. In particular, the dynamics of critically small populations (endangered species) and large populations (pest species) may be driven by unique dispersal variants. Here we documented individual variation in the ballooning dispersal behavior of Western black widow spiderlings Latrodectus hesperus, an urban pest species found in superabundant infestations throughout cities of the desert Southwest USA. We found a great deal of family-level variation in ballooning dispersal, and this variation was highly consistent (repeatable) across time. Maternal egg investment was a poor predictor of this ballooning dispersal. Instead, we show that spiderlings reared in isolation are significantly slower to disperse than spiderlings raised in a more natural setting surrounded by full siblings. Thus, our study examines a widespread but poorly understood dispersal behavior (ballooning), and suggests urban pest population dynamics are likely driven by the interaction of variation in individuals, families and social environments.

Foraging Rates of Larval Dragonfly Colonists Are Positively Related to Habitat Isolation: Results from a Landscape‐Level Experiment

There is increasing evidence of intraspecific variation in dispersal behavior. Individual differences in dispersal behavior may be correlated with other traits that determine the impact individuals have on patches they colonize. We established habitat patches-artificial pools-across a landscape, and these pools were naturally colonized by dragonfly larvae. Larvae were collected from pools at different levels of isolation and held under common lab conditions for 5 months. We then compared larval foraging rates. Foraging rate was positively related to habitat isolation, and colonists from the most isolated artificial pools had significantly higher foraging rates than individuals from the least isolated pools. Our results indicate that spatial patterns in colonist behavior can develop across a landscape independent of species-level dispersal limitation. This finding suggests that studies of community structure across space should include an assessment of the distribution of phenotypes as well as species-level dispersal limitation patterns.

The context of female dispersal in Kanyawara chimpanzees

In most social mammals, members of either one sex or both leave their natal group at sexual maturity. In catarrhine primates, male emigration is the predominant pattern. Female philopatry facilitates cooperation among kin, and female reproductive success is influenced by these relationships. Chimpanzees ( Pan troglodytes ) are unusual in that dispersal is almost exclusively by females. While plausible ultimate hypotheses can explain this dispersal pattern, the proximate causes of female dispersal are unknown and warrant examination due to variation in dispersal behaviour and the associated high costs of immigration. In this study, we examine the behavioural and hormonal context of female dispersal in chimpanzees of Kibale National Park, Uganda, in order to understand variation in dispersal patterns and gain insight into functional explanations. Using over 10 years of behavioural, endocrinological, and demographic records, we examined the significance of 5 potential predictors of the timing of dispersal: (1) maturational state; (2) association patterns; (3) mating patterns; (4) physiological stress; and (5) feeding ecology. Female dispersal was not strictly predicted by chronological or gynaecological age, and dispersal did not correlate with shifts in glucocorticoid levels. We found no evidence that females avoided mating in their natal group, even with known relatives, suggesting that inbreeding avoidance is not a sufficient proximate explanation for dispersal in chimpanzees. Instead, variation in social development and the availability of energy for dispersal were implicated and necessitate more intensive examination along with subtler variation in maturational trajectories.

Geographical variation in wolf spider dispersal behaviour is related to landscape structure

Theoretical studies suggest that mechanisms underlying habitat and population structure are important for shaping inter- and intraspecific variation in dispersal behaviour. Empirical evidence, especially in organisms living in spatially structured populations, however, is scarce. We investigated the relation between habitat configuration (patch size, connectivity) and dispersal by studying variation in tiptoe behaviour in the dune wolf spider, Pardosa monticola, under standardized laboratory conditions. Tiptoe behaviour prepares spiderlings for ballooning and can hence be considered as a precursor of aerial dispersal. The proportion of individuals that displayed tiptoe behaviour was highest in offspring from grasslands in a large dune landscape where habitat was continuously available, intermediate in offspring originating from a fragmented landscape, and lowest in offspring originating from a small and extremely isolated grassland patch. At the level of the fragmented landscape, variation was related to size and connectivity of four subpopulations. Both between and within landscapes, maternal condition had no effect on offspring dispersal. These results indicate that changes in habitat configuration from a large, connected landscape towards a small, fragmented one may lead to a decrease in dispersal rates, even at small spatial scales. Hence, behavioural traits narrowly linked to dispersal evolve towards less mobile phenotypes in small, isolated habitats, indicating high dispersal costs and low efficacy for gene flow in a spider species restricted to fragmented habitats.

Social Behavior, Reproductive Strategies, and Population Genetic Structure of Lagothrix poeppigii

For species of primates in which females emigrate, we would expect males within groups to be related to one another. Kin selection theory suggests that these males should associate preferentially with one another, be more affiliative and cooperative with one another than females are, and compete less overtly with one another over reproductive opportunities than males in female philopatric taxa do. Precisely these patterns of social behavior characterize well-studied populations of 2 of the 3 atelin primate genera: spider monkeys (Ateles) and muriquis (Brachyteles). For the third atelin genus, Lagothrix, patterns of intragroup social behavior have been less well-documented. We studied the social and reproductive behavior of lowland woolly monkeys (Lagothrix lagotricha poeppigii) in Ecuador during a one-year observational study and subsequently used molecular techniques to investigate population genetic structure and dispersal patterns for this taxon. Among adult male woolly monkeys, both affiliative and agonistic interactions were rare, and males were seldom in close proximity to one another. Relationships among male woolly monkeys are best characterized as tolerant, especially in the context of mating wherein direct competition among males was minimal despite the fact that females mated with multiple males. Relationships among females were likewise generally tolerant but nonaffiliative, though females often directed harassment towards copulating pairs. Affiliative interactions that did occur among woolly monkeys tended to be directed either between the sexes—primarily from female to male—or from younger towards older males, and the proximity partners of females tended to be members of the opposite sex. These results suggest that bonds between the sexes may be more important than same-sex social relationships and that direct female-female competition is an important feature of woolly monkey reproductive biology. Our genetic results indicate that, as in other atelins, dispersal by females is common, but some male dispersal likely occurs as well. In some but not all groups we studied, nonjuvenile males within social groups were more closely related to one another on average than females were, which is consistent with greater male than female philopatry. However, differences in these patterns among our study groups may reflect local variation in dispersal behavior.

Dispersal range analysis: quantifying individual variation in dispersal behaviour.

A complete understanding of animal dispersal requires knowledge not only of its consequences at population and community levels, but also of the behavioural decisions made by dispersing individuals. Recent theoretical work has emphasised the importance of this dispersal process, particularly the phase in which individuals search the landscape for breeding opportunities. However, empirical advances are currently hampered by a lack of tools for quantifying these dispersal search tactics. Here, we review existing methods for quantifying movement that are appropriate for the dispersal search process, describe several new techniques that we developed for characterising movement and behaviour through an individual's dispersal range, and illustrate their use with data from Australasian treecreepers (Climacteridae). We also describe how the quantitative parameters we discuss are calculated in a freely available computer software package that we designed. Specifically, we present methods for calculating the area searched during dispersal, search rate, thoroughness, intensity, philopatry of search, timing of exploration, and surreptitiousness. When we applied this approach to the study of dispersal in treecreepers, we found that search area, philopatry and timing of exploration showed the greatest individual variation. Furthermore, search area, search rate, thoroughness and philopatry of search were all correlated, suggesting they may be useful parameters for further research on the causes and consequences of different dispersal search tactics. Finally, we make recommendations for modifying radiotracking protocols to facilitate more accurate assessment of individual variation in the dispersal process, and suggest future directions for this type of empirical work at the interface of population and behavioural ecology.

Motivational and Heritable Determinants of Dispersal Latency in Wild Male House Mice (Mus musculus musculus)

AbstractDivergence of dispersal regimens has been suggested to be the selective basis for the evolutionary differentiation of agonistic phenotypes found in natural populations of house mice. Dispersal propensity may, therefore, be expected to exhibit heritable variation in wild house mice, ultimately related to motivational differences causing observable differences in agonistic behaviour. To test for heritable components in dispersal propensity in wild house mice, father–offspring regressions of dispersal latencies from residential social groups were determined in standardized seminatural social settings. To evaluate potential motivational causes of phenotypic variation in dispersal behaviour, all test animals (fathers, sons, and daughters) were scored prior to the dispersal experiment in a standardized behavioural test, at 60 d of age. Activities were monitored in a 1 m2 square test arena during 10‐min observation periods. Test arenas exhibited four equidistant openings leading to cages containing fresh, own, sibling, or foreign bedding material. The apparatus allowed for scoring anxiety, exploratory activity, and kin preference. Subsequently, test animals were exposed to a resident population in a semi‐natural enclosure providing a dispersal opportunity. Father–son regressions of dispersal latencies were significantly positive, but no significant relationship was found for daughters. Dispersal latency decreased with increasing exploratory activity scores in males, but increased in females. Anxiety as well as kin preferences did not affect dispersal propensity. Hence sex‐linked, motivational components reflect heritable social behaviour variation in male house mice that may ultimately be caused by diverging dispersal regimens.

SOCIAL AND ENVIRONMENTAL FACTORS AFFECT NATAL DISPERSAL AND PHILOPATRY OF MALE RED-COCKADED WOODPECKERS

Natal dispersal behavior can vary considerably among individuals, but the causes of intraspecific plasticity in dispersal are poorly understood. We tested six hypotheses about social and environmental conditions that might influence natal dispersal of males in the cooperatively breeding Red-cockaded Woodpecker (Picoides borealis). Further, we examined whether variation in dispersal behavior is heritable. Dispersing from the natal territory during the first year rather than remaining as a helper was associated with four factors. First, dispersing male fledglings were, on average, significantly lower in body mass than their philopatric siblings, indicating an influence of social dominance on dispersal. Second, individuals were more likely to disperse from territories with many male fledglings, independent of the number of adult male helpers per territory, suggesting that sibling (rather than helper–offspring) competition for future reproduction may be the underlying mechanism. Third, the probability of remaining as a helper rather than dispersing was positively associated with quality of the natal territory and with the number of high-quality territories close to the natal site. This suggests an influence of the benefits of philopatry, because many males that initially remain as helpers eventually become breeders on the natal territory or a neighboring territory. Finally, we found evidence that ecological constraints influence dispersal: the probability of dispersing was positively related to the availability of vacant territories in the wider neighborhood of the natal site. Natal dispersal behavior was not influenced by resource competition, measured as group size on the natal territory, or by local density, estimated as the number of active territories in the vicinity of the natal site. Based on comparisons of father–son and brother–brother dispersal behavior, we found no evidence for heritability of philopatric behavior. Dispersal of male fledgling Red-cockaded Woodpeckers can be viewed as conditional on social and ecological factors in the natal territory and in the immediate neighborhood. These factors seem to serve as proximate cues that influence young birds to either disperse or remain as philopatric helpers.

Individual variation in dispersal behaviour of newly emerged chinook salmon (Oncorhynchus tshawytscha) from the Upper Fraser River, British Columbia

Immediately after emergence from spawning gravels, fry of stream-type chinook salmon (Oncorhynchus tshawytscha) populations from tributaries of the upper Fraser River, British Columbia, distribute themselves downstream from the spawning areas, throughout the natal stream, and into the Fraser River. We tested the hypothesis that this range in dispersal distances is caused by innate differences in nocturnal migratory tendency among individuals. Using an experimental stream channel, we found repeatable differences in downstream movement behaviour among newly emerged chinook fry. Fish that moved downstream were larger than those that held position in the channel. However, the incidence of downstream movement behaviours decreased over the first 2 weeks after emergence. We propose that the variation among individuals in downstream movement behaviour we observed leads to the dispersal of newly emerged fry throughout all available rearing habitats. Thus, between- and within-population variation in the freshwater life history observed in these populations may be caused by small differences in the behaviour of individuals.

Individual variation in dispersal behaviour of newly emerged chinook salmon (<I>Oncorhynchus</I> <I>tshawytscha</I>) from the Upper Fraser River, British Columbia

Individual variation in dispersal behaviour of newly emerged chinook salmon (<I>Oncorhynchus</I> <I>tshawytscha</I>) from the Upper Fraser River, British Columbia

Emigration of Meadow Voles, Microtus Pennsylvanicus: The Effect of Sex Ratio

Exposure to testosterone has been suggested to serve as a trigger for dispersal of female mammals. In male biased litters there is a high probability that a female will be positioned in utero next to one or two males, and hence be exposed to the testosterone produced by the adjacent males. Sex ratio in litters of grey-sided voles, Clethrionomys rufocanus, successfully explain a major portion of the variation in dispersal behaviour of females of this species, thus providing indirect evidence that exposure to testosterone predisposes the females to disperse. Meadow voles, Microtus pennsylvanicus, were raised under laboratory conditions, and the emigration tendency of the young was tested using outdoor enclosures with exit gates

Heritability of dispersal in banner-tailed kangaroo rats, Dipodomys spectabilis

In a wild population of banner-tailed kangaroo rats, heritability of dispersal was estimated using two measures of dispersal tendency: distance moved from the natal site and likelihood of leaving the natal home range. Neither of the heritability measures was significantly different from 0. The results indicate that the main causes of variation in dispersal behaviour in this species are environmental, and suggest that there is no class of ‘innate’ dispersers. The possibility cannot be excluded that this population retains modest additive genetic variance for dispersal tendency. The survival consequences of dispersal in kangaroo rats are known to depend on population density and to change significantly between years, so that selection should maintain genetic variation in dispersal tendencies. Modest genetic variation for dispersal tendencies, especially if dispersal is a conditional trait, will be extremely difficult to detect in field studies.

Ecological Studies on the Butterfly Maniola jurtina in Britain. I. Adult Behaviour, Microdistribution and Dispersal

SUMMARY (1) The behaviour, microdistribution and dispersal of the meadow brown butterfly Maniolajurtina was investigated using mark-release-recapture techniques. (2) The main study site was a meadow at Hightown near Liverpool where a grid of 7.5 m squares was established. (3) Butterflies showed an aggregated microdistribution at Hightown. Intraseasonal changes and differences between years (generations) in microdistribution were correlated with changes in the distribution of clumps of flowering plants. Such changes in males were probably also influenced by the distribution of emerging females. The sexes showed statistically different microdistributions associated with differences in resource requirements. (4) A low rate of movement from areas of favourable habitat was detected (38 out of 1568 recaptures). The frequency distribution of the distance moved by M. jurtina at Hightown was leptokurtic. Butterflies tended to restrict their activity to familiar areas within the habitat of this population. The home range (95%) of individuals was estimated as 0.85 + 0.065 ha. Inspection of the data indicated that this is an underestimate. Preliminary evidence for individual variation in dispersal behaviour is examined. (5) Males and females showed similar dispersal rates. However, males fly more often than females. Males show a characteristic exploratory flight for mates. Females fly to lay eggs and to feed. Nectar is probably a more important resource for females than males. (6) The present study confirms the hypothesis of Handford (1973) that male and female M.jurtina occupy different ecological niches.

Ecological Variables Affecting the Dispersal Behavior of Drosophila pseudoobscura and Its Relatives

Results of field studies indicate that dispersal behavior of Drosophila species of the American obscura group is strongly affected by ecological factors. In some habitats the flies move very rapidly while in others they are quite sedentary. In an attempt to quantify the spatial variation in dispersal, we have performed computer simulations based on diffusion equations. We assigned different dispersal coefficients to the six different habitat types we identified in the area in which the field studies were performed. The best-fit simulations indicate that dispersal rates vary by nearly one order of magnitude in an area a few hundred meters square. Such variation in dispersal behavior affects the population genetic structure and evolution of populations.