Role of breeding and natal movements in lifetime dispersal of a forest‐dwelling rodent

The lifetime movements of an individual determine the gene flow and invasion potential of the species. However, sex dependence of dispersal and selective pressures driving dispersal have gained much more attention than dispersal at different life and age stages. Natal dispersal is more common than dispersal between breeding attempts, but breeding dispersal may be promoted by resource availability and competition. Here, we utilize mark–recapture data on the nest‐box population of Siberian flying squirrels to analyze lifetime dispersal patterns. Natal dispersal means the distance between the natal nest and the nest used the following year, whereas breeding movements refer to the nest site changes between breeding attempts. The movement distances observed here were comparable to distances reported earlier from radio‐telemetry studies. Breeding movements did not contribute to lifetime dispersal distance and were not related to variation in food abundance or habitat patch size. Breeding movements of males were negatively, albeit not strongly, related to male population size. In females, breeding movement activity was low and was not related to previous breeding success or to competition between females for territories. Natal philopatry was linked to apparent death of a mother; that is, we did not find evidence for mothers bequeathing territories for offspring, like observed in some other rodent species. Our results give an example of a species in which breeding movements are not driven by environmental variability or nest site quality. Different evolutionary forces often operate in natal and breeding movements, and our study supports the view that juveniles are responsible for redistributing individuals within and between populations. This emphasizes the importance of knowledge on natal dispersal, if we want to understand consequences of movement ecology of the species at the population level.     

Scale‐specific processes shape plant community patterns in subtropical coastal grasslands

Processes responsible for shaping community patterns act at specific spatial scales. In this study, we aimed at disentangling the effects of climate, soil and space as drivers of variation in a coastal grassland plant community. We were specifically interested in evaluating the relative influence of those processes at broad and fine spatial scales as well as when considering species groups with good and poor long‐distance dispersal capacity. We sampled grassland vegetation at 16 sites distributed along a latitudinal gradient of more than 500 km in subtropical southern Brazil and used variation partitioning procedures to ascertain the relative influence of climatic, edaphic and spatial processes on variation in species composition at different spatial scales, considering the entire community and subsets with only species from the Asteraceae family (good long‐distance dispersal) and Poaceae (poor long‐distance dispersal). Climatic filters were the most responsible for shaping grassland community composition at the broad scale, while edaphic filters showed higher importance at the fine scale. When not considering the influence of spatial scale, we observed higher influence of climate structured in space. Composition patterns of species with poor long‐distance dispersal (Poaceae) were more closely related to spatial variables than those of species with effective dispersal (Asteraceae). Our results stressed the importance of addressing different spatial scales to rightly ascertain the magnitude that different drivers exert on plant community assembly. Dividing the community into groups with different dispersal abilities proved useful for a more detailed understanding of the community assembly processes.     

Sex biased natal dispersal in a closed, saturated population of Seychelles warblers Acrocephalus sechellensis

The distances that individuals disperse, from their natal site to the site of first breeding and between breeding sites, have important consequences for the dynamics and genetic structure of a population. Nearly all previous studies on dispersal have the problem that, because the study area encompassed only a part of the population, emigration may have been confounded with mortality. As a result long-distance dispersers may have been overlooked and dispersal data biased towards short distances. By studying a virtually closed population of Seychelles warblers Acrocephalus sechellensis we obtained almost unbiased results on several aspects of dispersal. As in the majority of other avian species, natal dispersal distance was female biased in the Seychelles warbler. Female offspring also forayed further from the natal territory in search of breeding vacancies than male offspring. The sex bias in natal dispersal distance did, however, depend on local breeding density. In males, dispersal distance decreased as the number of territories bordering the natal territory increased, while in females, dispersal distance did not vary with local density. Dispersal by breeders was rare and, unlike in most species, distances did not differ between the sexes. We argue that our results favour the idea that the sex bias in natal dispersal distance in the Seychelles warbler is due to inbreeding avoidance and not resource competition or intrasexual competition for mates.     

Genetic and environmental influences on natal dispersal distance in a resident bird species

We analyzed more than 1,600 dispersal events from two populations of a North American cooperatively breeding woodpecker species to determine what factors influence natal dispersal distance and whether distance traveled affects reproduction later in life. We found significant heritability of natal dispersal distance, in both males and females, indicating substantial additive genetic variance for this behavioral trait. Natal dispersal distance additionally was affected by social and ecological factors: individuals dispersing in their first year of life moved longer distances than those staying on their natal site as helpers for a prolonged time prior to dispersal, and increasing territory isolation led to longer dispersal distances. Successful dispersers incurred fitness costs, with lifetime fledgling production (in both sexes) and lifetime production of recruits to the breeding population (in females only) decreasing with increasing natal dispersal distance. We conclude that natal dispersal distance has a genetic basis but is modulated by environmental and social factors and that natal dispersal distance in this species is (currently) under selection.     

Annual variation in long‐distance dispersal driven by breeding and non‐breeding season climatic conditions in a migratory bird

Long‐distance dispersal is a fundamental process in ecology and evolution but the factors that influence these movements remain poorly understood in most species. We used stable hydrogen isotopes to quantify the rate and direction of long‐distance immigration in a breeding population of American redstarts and to test whether the settlement decisions that result in long‐distance dispersal are driven by habitat saturation or by the phenology of breeding‐season resources. Our results provide evidence that both natal dispersal and breeding dispersal were influenced by the timing of breeding‐season phenology, with both age classes more likely to disperse north in years when the onset of breeding‐season phenology occurs earlier than normal. Yearlings were also more likely to disperse north following winters with poor habitat quality on their non‐breeding grounds, demonstrating that carry‐over effects from the non‐breeding season influence natal dispersal in this species. Collectively, these results are consistent with the hypothesis that American redstarts use the phenology of breeding season resources as a cue to select breeding sites. Our results suggest that long‐distance dispersal may allow individuals to rapidly respond to advancing phenology caused by global climate change, though their ability to do so may be constrained by long‐term decline in habitat quality predicted for their tropical non‐breeding grounds.     

The origin of out‐of‐range pelicans in Europe: wild bird dispersal or zoo escapes?

We tested whether spatial and annual patterns of occurrence of out-of-range Great White Pelecanus onocrotalus , Dalmatian Pelecanus crispus and Pink-backed Pelicans Pelecanus rufescens recorded in Europe between 1980 and 2004 supported a natural vagrancy theory. Candidate variables tested were those likely to influence dispersal and escape probability (distance to the usual breeding/wintering range, national captive stock), and wild breeding population sizes and their movements (size of breeding colonies, climate conditions on wintering grounds or during dispersal). Spatial vagrancy patterns supported the hypothesis of wild birds dispersing from their normal range, with decreasing national totals with increasing distance to the usual range for the three species. Annual out-of-range numbers of Great White Pelican were predicted by breeding colony size and breeding success in Greece, with a further effect of Sahel rainfall during the previous year. Annual numbers of Dalmatian Pelican were related to the North Atlantic Oscillation index and to breeding success in Greece. Finally, annual numbers of Pink-backed Pelican were predicted by summer Sahel rainfall, which is known to drive dispersal of the species northwards into the sub-Sahelian steppes during wet summers there. Hence, annual vagrancy patterns in Europe were well predicted for all three species by population size indices, reproductive success and/or climatic components, which presumably influence survival and/or dispersal. We therefore consider that vagrancy patterns were driven by wild birds, whereas escapes – even if potentially numerous – do not create sufficient 'noise' to hide these patterns.     

Dispersal and establishment filters influence the assembly of restored prairie plant communities

Community assembly filters, which in theory determine the suite of species that arrive at and establish in a community, have tremendous conceptual relevance to restoration. However, the concept has remained largely theoretical, with a paucity of empirical tests. As such, the applicability of assembly filters theory to ecological restoration remains incompletely known. We tested the relative strengths of dispersal and establishment filters by comparing the plant species composition, measured by species' presence/absence, in 29 restored prairies with the seed mixes used to restore each prairie. We found that both establishment and dispersal filters limited prairie similarity to the seed mix. Sown species responded differentially to filters, with a few species limited only by dispersal (seed density), many others limited only by establishment conditions (i.e. organic matter and sand content of soils, land use history, and fire frequency), and others limited by both dispersal and establishment filters. A few species, typically those sown most often, were not restricted by dispersal or establishment filters, likely because they were sown in high enough densities and all sites had suitable environmental conditions. Finally, one group of species established poorly, but we could not attribute this to either dispersal or establishment filters. This information can help land managers select species likely to establish in restorations when sown at sufficient densities. These results illustrate that dispersal and establishment filters limit the establishment of species in restored communities and these filters are species‐dependent. Identifying the most limiting filter(s) for species will inform strategies to increase their establishment success.     

Dispersal characteristics of seven odonate species in an agricultural landscape

Dispersal is an ecological phenomenon which is of fundamental importance to population biology. While dispersal behaviour of many orders of winged insects has received a great deal of attention, the dispersal characteristics of odonates have been poorly documented. We used capture-mark-recapture techniques to study dispersal behaviour of seven species of odonates breeding on a network of 11 small ponds in Cheshire, U.K. The ponds ranged in size from 615 to 1300 m²- and varied from 30 to 860 m apart. We found surprisingly high rates of dispersal between ponds, with 10–47% per species of recaptured individuals moving from their natal pond. The mean probability of dispersal differed significantly among species but the relationship between the probability of dispersal and distance moved consistently followed a simple negative exponential curve for all species. Most individuals stayed at their natal pond, but a few moved long distances. Neither the age at which an individual was marked (teneral vs sexually mature) nor its sex significantly affected its tendency to disperse. The negative exponential relationship suggests that dispersal should be relatively easy to incorporate in more complex models of odonate spatio-temporal dynamics. To our knowledge, this is the first large-scale, multi-species study to assess dispersal behaviour of odonates by direct observation.     

Dispersal influences genetic and acoustic spatial structure for both males and females in a tropical songbird

Animals exhibit diverse dispersal strategies, including sex‐biased dispersal, a phenomenon common in vertebrates. Dispersal influences the genetic structure of populations as well as geographic variation in phenotypic traits. Patterns of spatial genetic structure and geographic variation may vary between the sexes whenever males and females exhibit different dispersal behaviors. Here, we examine dispersal, spatial genetic structure, and spatial acoustic structure in Rufous‐and‐white Wrens, a year‐round resident tropical bird. Both sexes sing in this species, allowing us to compare acoustic variation between males and females and examine the relationship between dispersal and song sharing for both sexes. Using a long‐term dataset collected over an 11‐year period, we used banding data and molecular genetic analyses to quantify natal and breeding dispersal distance in Rufous‐and‐white Wrens. We quantified song sharing and examined whether sharing varied with dispersal distance, for both males and females. Observational data and molecular genetic analyses indicate that dispersal is female‐biased. Females dispersed farther from natal territories than males, and more often between breeding territories than males. Furthermore, females showed no significant spatial genetic structure, consistent with expectations, whereas males showed significant spatial genetic structure. Overall, natal dispersal appears to have more influence than breeding dispersal on spatial genetic structure and spatial acoustic structure, given that the majority of breeding dispersal events resulted in individuals moving only short distances. Song sharing between pairs of same‐sex animals decreases with the distance between their territories for both males and females, although males exhibited significantly greater song sharing than females. Lastly, we measured the relationship between natal dispersal distance and song sharing. We found that sons shared fewer songs with their fathers the farther they dispersed from their natal territories, but that song sharing between daughters and mothers was not significantly correlated with natal dispersal distance. Our results reveal cultural differences between the sexes, suggesting a relationship between culture and sex‐biased dispersal.     

Factors influencing and consequences of breeding dispersal and habitat choice in female grey seals (<Emphasis Type="Italic">Halichoerus grypus</Emphasis>) on Sable Island,Nova Scotia

Selection of breeding location can influence reproductive success and fitness. Breeding dispersal links habitat use and reproduction. This study investigated factors affecting breeding dispersal and its reproductive consequences in grey seals (Halichoerus grypus) on Sable Island, Nova Scotia. Breeding dispersal distance was determined in 692 individually marked, known-age female grey seals observed from 2004 to 2014. We used generalized linear mixed-effects models to test hypotheses concerning environmental and demographic factors influencing breeding dispersal distance and the consequences of dispersal distance on offspring weaning mass. Grey seal females rarely exhibited fidelity to previous breeding sites. Median dispersal distance between years was 5.1 km. Only 2.9% of females returned to a previous breeding site. Breeding dispersal distance was affected by parity and density, but effects were small and are presumably of no biological significance. Variation in dispersal distance among adult females was large. Dispersal distance had no significant influence on offspring weaning mass; however, as previously found, pup sex and maternal age did. Although breeding location was not important, heavier pups were born in habitats with no tidal or storm-surge influence indicating that breeding habitat type did influence offspring size at weaning. The lack of site fidelity in grey seals on Sable Island is associated with an unpredictable and changing landscape (sand dunes) that could make it difficult for females to locate previous breeding locations. Although breeding location within habitat type had small consequences on offspring weaning mass, we detected no evidence that breeding site selection within the habitat had consequences to females.     

Inbreeding avoidance mechanisms: dispersal dynamics in cooperatively breeding southern pied babblers

1.?Breeding with kin can reduce individual fitness through the deleterious effects of inbreeding depression. Inbreeding avoidance mechanisms are expected to have developed in most species, and especially in cooperatively breeding species where individuals may delay dispersal until long after sexual maturity. Such potential mechanisms include sex-biased dispersal and avoidance of kin known through associative learning. 2.?The investigation of inbreeding avoidance through dispersal dynamics can be enhanced by combining fine-scale population genetic structure data with detailed behavioural observations of wild populations. 3.?We investigate possible inbreeding avoidance in a wild population of cooperatively breeding southern pied babblers (Turdoides bicolor). A combination of genetic, geographic and observational data is used to examine fine-scale genetic structure, dispersal (including sex-biased dispersal) and inheritance of dominance in cooperatively breeding groups. 4.?Unusually, sex-bias in dispersal distance does not occur. Rather, individuals appear to avoid inbreeding through two routes. First, through dispersal itself: although both males and females disperse locally, they move outside the range within which genetically similar individuals are usually found, going twice as far from natal groups as from non-natal groups. Second, through avoidance of familiar group members as mates: individuals inherit a dominant position in the natal group only when an unrelated breeding partner is present. 5.?This study uses spatial genetic analyses to investigate inbreeding avoidance mechanisms in a cooperative breeder and shows that individuals of both sexes can avoid inbreeding through a dispersal distance mechanism. While it appears that dispersal allows most individuals to move beyond the range of closely related kin, matings may still occur between distant kin. Nevertheless, any costs of breeding with a distant relative may be outweighed by the benefits of local dispersal and the immense fitness gains available from attaining a breeding position.     

Limited dispersal by Nazca boobies Sula granti

We documented natal and breeding dispersal at several spatial scales by Galápagos Nazca boobies Sula granti, a wide‐ranging pelagic seabird. We found exceptionally low degrees of both types of dispersal despite these birds’ vagility. Median natal dispersal distances were 26 m and 105 m for males and females, respectively. Median breeding dispersal distances for both sexes were 0 m. No natal or breeding dispersals occurred from our study site at Punta Cevallos, Isla Española to six other colonies in the Galápagos, but we did document four long‐distance natal dispersals from Punta Cevallos to islands near the South American coast. Recaptures and dead recoveries of ringed birds showed long distance non‐breeding movements to the Central American coast and elsewhere in the eastern Pacific, contrasting with the very limited dispersal to breeding sites.     

Parasitism, host immune defence and dispersal

Host-parasite interactions have been hypothesized to affect the evolution of dispersal by providing a possibility for hosts to escape debilitating parasites, and by influencing the level of local adaptation. We used a comparative approach to investigate the relationship between a component of host immune function (which reflects the evolutionary history of parasite-induced natural selection) and dispersal in birds. We used a sample of 46 species of birds for which we had obtained field estimates of T-cell response for nestlings, mainly from our own field studies in Denmark and Spain. Bird species with longer natal, but not with longer breeding dispersal distances had a stronger mean T-cell-mediated immune response in nestlings than species with short dispersal distances. That was also the case when controlling for the potentially confounding effect of migration from breeding to wintering area, which is known from previous studies to be positively associated with dispersal distance. These relationships held even when controlling for similarity among species because of common ancestry. Avian hosts with a larger number of different breeding habitats had weaker mean T-cell-mediated immune responses than habitat specialists. This relationship held even when controlling for similarity among species because of common ancestry. Therefore, T-cell-mediated immunity is an important predictor of evolutionary changes in dispersal ability among common European birds.     

Offspring-driven local dispersal in female sand lizards (Lacerta agilis)

We report on a field study in which determinants of female breeding dispersal (i.e. the shift in the mean home range coordinates between successive breeding events) was investigated. Offspring were released in full sib groups (or half sib ones if there was within-clutch multiple paternity) at a separation distance from the females that varied between 'families'. This allowed for analysis of 'offspring nearness' effects on maternal dispersal. When a female's offspring were released more closely to her, she responded with greater dispersal. Furthermore, when the data set was truncated at 100 m maternal-offspring separation distance at offspring release (because perception at longer distances is likely to be unrealistic), maternal dispersal resulted in greater separation distance between female and offspring in the following year. A corresponding analysis for juveniles revealed no effect of maternal nearness on offspring dispersal but identified a significant effect of clutch size, to our surprise with dispersal declining with increasing clutch size. We discuss this result in a context of the 'public information hypothesis' (reinterpreted for juveniles in a nonsocial foraging species), suggesting that conspecific abundance perhaps acts as an indicator of local habitat quality. Thus, our analysis suggests a microgeographic structuring of the adult female population driven by genetic factors, either through inbreeding avoidance, or from simply avoiding individuals with a similar genotype regardless of their pedigree relatedness, while a nongenetic factor seems more important in their offspring.     

Genetic consequences of natal dispersal in the colonial lesser kestrel

Dispersal is a life-history trait that plays a fundamental role in population dynamics, influencing evolution, species distribution, and the genetics and structure of populations. In spite of the fact that dispersal has been hypothesized to be an efficient behavioural mechanism to avoid inbreeding, the expected relationship between dispersal and mate relatedness still remains controversial. Here, we examine the genetic consequences of natal dispersal, namely the higher chance of obtaining genetically less similar mates as a result of moving from natal to breeding sites, in a lesser kestrel (Falco naumanni) population. Relatedness between individuals tended to decrease with distance between their breeding colonies, indicating that the study population follows an 'isolation-by-distance' pattern of spatial genetic structure. Such a fine-scale genetic structure generates a scenario in which individuals can potentially increase the chance of obtaining genetically less similar mates by dispersing over larger distances from their natal colony. Using dispersal information and genotypic data, we showed that mate relatedness decreased with natal dispersal distance, an effect that remained significant both while including and excluding philopatric individuals from the data set. These results, together with the well known detrimental consequences of reduced genetic diversity in the study population, suggest that dispersal may have evolved, at least in part, to avoid the negative fitness consequences of mating with genetically similar individuals.     

Modelling and analysing evolution of dispersal in populations at expanding range boundaries

Abstract 1. Species would be expected to shift northwards in response to current climate warming, but many are failing to do so because of fragmentation of breeding habitats. Dispersal is important for colonisation and an individual‐based spatially explicit model was developed to investigate impacts of habitat availability on the evolution of dispersal in expanding populations. Model output was compared with field data from the speckled wood butterfly Pararge aegeria, which currently is expanding its range in Britain. 2. During range expansion, models simulated positive linear relationships between dispersal and distance from the seed location. This pattern was observed regardless of quantity (100% to 10% habitat availability) or distribution (random vs. gradient distribution) of habitat, although higher dispersal evolved at expanding range margins in landscapes with greater quantity of habitat and in gradient landscapes. Increased dispersal was no longer evident in any landscape once populations had reached equilibrium; dispersal values returned to those of seed populations. However, in landscapes with the least quantity of habitat, reduced dispersal (below that of seed populations) was observed at equilibrium. 3. Evolutionary changes in adult flight morphology were examined in six populations of P. aegeria along a transect from the distribution core to an expanding range margin in England (spanning a latitudinal distance of >200 km). Empirical data were in agreement with model output and showed increased dispersal ability (larger and broader thoraxes, smaller abdomens, higher wing aspect ratios) with increasing distance from the distribution core. Increased dispersal ability was evident in populations from areas colonised >30 years previously, although dispersal changes were generally evident only in females. 4. Evolutionary increases in dispersal ability in expanding populations may help species track future climate changes and counteract impacts of habitat fragmentation by promoting colonisation. However, at the highest levels of habitat loss, increased dispersal was less evident during expansion and reduced dispersal was observed at equilibrium indicating that, for many species, continued habitat fragmentation is likely to outweigh any benefits from dispersal.     

Dispersal and climate change: a case study of the Arctic tern Sterna paradisaea

Dispersal is an important evolutionary process that can affect admixture of populations and cause rapid responses to changing climatic conditions due to gene flow from populations at different altitudes or latitudes already experiencing these conditions. We investigated long-term patterns of natal and breeding dispersal in a coastal seabird, the Arctic tern Sterna paradisaea , that experiences specific climatic conditions in the northern temperate and Arctic climate zones during breeding and different climatic conditions in the Antarctic during winter. Long natal and breeding dispersal distances were costly as shown by their effects on delayed breeding. Dispersal distances varied significantly among years, with natal dispersal showing a strong temporal increase during the last 70 years. Annual differences in dispersal distance could be accounted for by climate conditions in the breeding grounds and the winter quarters. Natal dispersal was related to climate conditions in both the year of hatching and the year of breeding, whereas breeding dispersal was only related to climate conditions in the second year of the dispersal event. Only the north Atlantic oscillation (NAO) index for winter showed a consistent temporal trend, suggesting that the temporal trend in natal dispersal distance must be caused by changes in the NAO (or associated phenomena). These findings indicate that dispersal can change rapidly in response to changing climate conditions.     

Distance-dependent performance of asexual progeny in Allium vineale (Liliaceae)

Local adaptation within and among populations may have an impact on processes ranging from speciation to the evolution of mixed breeding systems and dispersal strategies. It is also one potential factor that could favor the production of asexual over sexual propagules. This field experiment tested whether asexually produced bulbils of Allium vineale demonstrate local adaptation to the parental microsite at the scale of natural dispersal from the parent (5, 25, 50, 100, and 1000 cm). Both "home' and randomly chosen "away' genotypes were planted at each location to determine the relative performance of the "home' genotype. Overall, bulbil performance declined with distance from the parent. In particular, "home' bulbils outperformed "away' bulbils at a distance of 25 cm from the parent, indicating that local adaptation has occurred at the scale of natural dispersal in this species. The variance in propagule performance also increased at farther distances from the parent, indicating that the predictability of offspring performance decreases with distance. Fine-scale local adaptation within the range of seed dispersal in this population may be one factor favoring asexual reproduction in Allium vineale.