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Dispersal Behaviour (dispersal + behaviour)
Selected AbstractsThe mortality of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) neonate larvae in relation to drop-off and soil surface temperature: the dangers of bungy jumpingAUSTRALIAN JOURNAL OF ENTOMOLOGY, Issue 4 2008David J Perovi Abstract The first larval instar has been identified as a critical stage for population mortality in Lepidoptera, yet due to the body size of these larvae, the factors that contribute to mortality under field conditions are still not clear. Dispersal behaviour has been suggested as a significant, but ignored factor contributing to mortality in first-instar lepidopteran larvae. The impact that leaving the host plant has on the mortality rate of Helicoverpa armigera neonates was examined in field crops and laboratory trials. In this study the following are examined: (1) the effects of soil surface temperature, and the level of shade within the crop, on the mortality of neonates on the soil after dropping off from the host plant; (2) the percentage of neonates that dropped off from a host plant and landed on the soil; and (3) the effects of exposure to different soil surface temperatures on the development and mortality of neonates. The findings of this study showed that: (1) on the soil, surface temperatures above 43°C were lethal for neonates, and exposure to these temperatures contributed greatly to the overall mortality rate observed; however, the fate of neonates on the soil varied significantly depending on canopy closure within the crop; (2) at least 15% of neonates dropped off from the host plant and landed on the soil, meaning that the proportion of neonates exposed to these condition is not trivial; and (3) 30 min exposure to soil surface temperatures approaching the lethal level (>43°C) has no significant negative effects on the development and mortality of larvae through to the second instar. Overall leaving the plant through drop-off contributes to first-instar mortality in crops with open canopies; however, survival of neonates that have lost contact with a host plant is possible, and becomes more likely later in the crop growing season. [source] Repeatability of dispersal behaviour in a common dwarf spider: evidence for different mechanisms behind short- and long-distance dispersalECOLOGICAL ENTOMOLOGY, Issue 2 2009DRIES BONTE Abstract 1.,The response of dispersal towards evolution largely depends on its heritability for which upper limits are determined by the trait's repeatability. 2.,In the Linyphiid spider E. atra, we were able to separate long- and short-distance dispersal behaviours (respectively ballooning and rappelling) under laboratory conditions. By performing repeated behavioural trials for females, we show that average dispersal trait values decrease with increasing testing days. By comparing mated and unmated individuals during two periods (before and after mating for the mated group, and the same two periods for the unmated group), we show that mating has no effect on the mean displayed dispersal behaviour or its within-individual variation. Repeatabilities were high and consistent for ballooning motivation, but not for rappelling. 3.,Ballooning motivation can be regarded as highly individual-specific behaviour, while general pre-dispersal and rappelling behaviours showed more individual variation. Such difference in repeatability between long- and short-distance dispersal suggests that short- and long-distance dispersal events are triggered by different ecological and evolutionary mechanisms. [source] Experimental evolution of dispersal in spatiotemporally variable microcosmsECOLOGY LETTERS, Issue 10 2003Nicholas A. Friedenberg Abstract The world is an uncertain place. Individuals' fates vary from place to place and from time to time. Natural selection in unpredictable environments should favour individuals that hedge their bets by dispersing offspring. I confirm this basic prediction using Caenorhabditis elegans in experimental microcosms. My results agree with evolutionary models and correlations found previously between habitat stability and individual dispersal propensity in nature. However, I also find that environmental variation that triggers conditional dispersal behaviour may not impose selection on baseline dispersal rates. These findings imply that an increased rate of disturbance in natural systems has the potential to cause an evolutionary response in the life history of impacted organisms. [source] Dispersal and influences on movement for Anoplophora glabripennis calculated from individual mark-recaptureENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 2 2005J.S. Bancroft Abstract We conducted an individual mark-release-recapture experiment on the beetle, Anoplophora glabripennis Motchulsky (Coleoptera: Cerambycidae). This invasive beetle has been introduced from Asia to Europe and North America and poses a serious threat to several important species of tree. Eradication efforts may benefit from knowledge of dispersal behaviour. Trees were cut and held to determine emergence rate of A. glabripennis. Unique marks were painted onto 912 beetles released into a group of 165 trees in Gansu, China. Data on subsequent sightings of beetles were used in a truncated diffusion model to calculate flight distances. Characteristics of the trees and climatic information were used in statistical tests for influence on movement. A total of 2245 sightings of beetles were observed and 29% of marked beetles were resighted. The scanning technique using binoculars was 90% effective in finding beetles and provided 81% accuracy for determining the sex of the beetles. Experimental manipulation of density quantified how A. glabripennis congregated on unoccupied trees and were repulsed from crowded hosts. The seasonal emergence rate of adults declined exponentially from July 20 to August 5. The results suggested A. glabripennis fly to nearby host trees at a rate of 34% per day. Median flight distance was estimated at 20 m per day. Statistical analysis with a generalized linear model tested the beetle's propensity to leave a tree and distance of flight. Generally, beetle movement showed a significant response to beetle density, weather conditions, beetle size, and tree size, in that order. The techniques developed here improve on previous recapture techniques to quantify dispersal and can be useful for analysing populations of other organisms. [source] Selection of hibernation sites by Anthonomus pomorum: preferences and ecological consequencesENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 3 2000St. Toepfer Abstract The apple blossom weevil, Anthonomus pomorum (L.) (Coleoptera: Curculionidae), has a long period of aestivo-hibernation in the adult stage lasting from summer to early spring of the following year. Potential hibernation sites within an apple orchard consist of high-stem rough-bark trees or dwarf smooth-bark trees. Field release-recapture experiments in 2 consecutive years showed that 64 and 47% of the weevils remained in the vicinity of the release sites in an area of high-stem trees and dwarf trees, respectively. The dispersing weevils moved over an average distance of 5.5 m in the dwarf tree area, as compared to 3.8 m in the high-stem tree area. The prevalent direction of dispersal was along tree rows in both areas. Some weevils displayed, after release in mid-July, a directional dispersal to the adjacent forests. Others, released in the dwarf tree area, dispersed towards the area of high-stem rough-bark apple trees. Experiments simulating various hibernation sites demonstrated that the litter of dry leaves was the most preferred overwintering shelter, yielding a relatively high survival rate. Branches with rough bark ranked second, while branches with smooth bark, grass and pure soil were not favourable for overwintering. Flight tendency in newly emerged weevils of summer generation was significantly higher in June/July than in August/September. This corresponds to the dispersal behaviour in the field. The timing of spring colonisation of apple trees was similar for weevils overwintering within the orchard and for those from outside. These results suggest that modern, dwarf apple orchards offer unfavourable conditions for overwintering, but that the relatively small proportion of weevils which manage to reach the adjacent forests find optimal hibernation sites there. [source] Constraints on recovery: using molecular methods to study connectivity of aquatic biota in rivers and streamsFRESHWATER BIOLOGY, Issue 4 2007JANE M. HUGHESArticle first published online: 2 MAR 200 Summary 1. The ,Field of Dreams Hypothesis' states ,if we build it, they will come', referring to the assumption that if habitats are restored, species will recolonise them. However, the ability of a species to recolonise a restored site will depend not only on the appropriate habitat being present, but also on the ability to get there. This is likely to depend on both the species' dispersal behaviour and the position of a site in the landscape. 2. Animals with good potential for dispersal are more likely to be able to disperse to newly restored sites. Similarly, sites in lowland streams with limited altitudinal differences between sites may be easier to reach than upstream sites. This is because upstream sites are connected to one another via lowland streams that have different characteristics and therefore may be difficult for animals to traverse. 3. In this paper, genetic data from a range of freshwater species that have been analysed in my laboratory are used to assess the importance of life cycle and position in the landscape (i.e. upland versus lowland streams) on connectivity patterns (and thus recolonisation potential) among populations. 4. In general, contemporary dispersal across catchment boundaries is negligible, except for aquatic insects with an adult flight stage. Dispersal among streams within catchments appears to be more limited than was predicted from knowledge on life histories, except for fish in lowland rivers and streams. 5. As predicted, dispersal of fish, crustaceans and molluscs among streams within catchments is significantly greater in lowland rivers than in upland streams. 6. Overall, these analyses suggest that, with the exception of most insects, and fishes in lowland rivers, natural recolonisation of restored sites is only likely from sites within the same stream. If a species has disappeared from the whole stream, then restoration of habitat alone may not be sufficient for its re-establishment. [source] Climate warming, dispersal inhibition and extinction riskGLOBAL CHANGE BIOLOGY, Issue 3 2008MANUEL MASSOT Abstract Global warming impels species to track their shifting habitats or adapt to new conditions. Both processes are critically influenced by individual dispersal. In many animals, dispersal behaviour is plastic, but how organisms with plastic dispersal respond to climate change is basically unknown. Here, we report the analysis of interannual dispersal change from 16 years of monitoring a wild population of the common lizard, and a 12-year manipulation of lizards' diet intended to disentangle the direct effect of temperature rise on dispersal from its effects on resource availability. We show that juvenile dispersal has declined dramatically over the last 16 years, paralleling the rise of spring temperatures during embryogenesis. A mesoscale model of metapopulation dynamics predicts that in general dispersal inhibition will elevate the extinction risk of metapopulations exposed to contrasting effects of climate warming. [source] The role of food supply in the dispersal behaviour of juvenile Tawny Owls Strix alucoIBIS, Issue 2 2003C. F. Coles We investigated the effects of food supply on decisions made by dispersing juvenile Tawny Owls Strix aluco in Kielder Forest, Northumberland, in 1996 and 1997. Field Voles Microtus agrestis were the main food of the owls and clear-cuts the main habitat for voles. A vole sign index was used to estimate vole abundance. In areas near to roosting owls, mean vole densities were 83 and 115 ha,1 in 1996 and 1997, respectively. The prediction that birds would perform area-restricted searches when prey was more abundant was not confirmed. Moreover, we found no evidence that juveniles avoided conspecifics. Owls appeared to have an imperfect knowledge of the environment as they responded to variability in Field Vole densities by altering the time spent in different areas rather than by moving to areas with successively greater vole densities. Vole abundance explained 25.7% of the variation in the time spent in different areas. Movements did not decrease with time after dispersal, although the detection of such movements was prone to error. This study supports recent work suggesting that although dispersal may be initiated by a variety of proximate and ultimate factors, individual decisions made during dispersal may depend partly on environmental conditions encountered during the process itself. [source] Adult mortality rates in young colonies of a swarm-founding social wasp (Polybia occidentalis)JOURNAL OF ZOOLOGY, Issue 1 2003Andrew M. Bouwma The swarm founders are unusual among the social wasps in having socialized the dispersal stage of the life cycle. Colonies are initiated by groups of workers accompanied by smaller numbers of queens. Thus, swarm founders avoid the colony size bottleneck faced by the independent founders, whose colonies start with one or a few queens. Among the advantages of swarm founding is a reduction of the risk of colony failure due to attrition of the founding adults. Stochasticity in adult mortality is less likely to lead to outright extinction of a large founding group before new workers are produced (pre-emergence period). However, it is not known how important pre-emergence mortality is as a selective force on founding and dispersal behaviour in swarm founders, since colony-wide mortality rates have never been reported for a large-colony social wasp. Sixty-eight swarms of Polybia occidentalis were censused just before colony initiation and again 24 days later. Mortality over this period averaged 0.41±0.12 of the founding swarm population. Including mortality on the day of emigration and extrapolating to day 30, when the first adult offspring eclose, the original absconding swarm would be reduced by 0.52 of its initial size. Rates of loss during the first week, while the colonies engaged in nest construction, did not differ from rates over the full 24 days. Thus, colony founding in P. occidentalis is both costly and highly variable in terms of mortality of the founding adults. [source] Variable extent of sex-biased dispersal in a strongly polygynous mammalMOLECULAR ECOLOGY, Issue 15 2010S. PÉREZ-ESPONA Abstract For mammals with a polygynous mating system, dispersal is expected to be male-biased. However, with the increase in empirical studies, discrepancies are arising between the expected and observed direction/extent of the bias in dispersal. In this study, we assessed sex-biased dispersal in red deer (Cervus elaphus) on 13 estates from the Scottish Highlands. A total of 568 adult individuals were genotyped at 21 microsatellite markers and sequenced for 821 bp of the mitochondrial control region. Estimates of population structure with mitochondrial sequences were eight times larger than that obtained with microsatellite data (Fst,-mtDNA = 0.831; Fst,-micros = 0.096) indicating overall male-biased dispersal in the study area. Comparisons of microsatellite data between the sexes indicated a predominance of male-biased dispersal in the study area but values of FST and relatedness were only slighter larger for females. Individual-based spatial autocorrelation analysis generated a similar pattern of relatedness across geographical distances for both sexes, with differences only significant at two distance intervals (25,30 and 70,112 km). Patterns of relatedness differed between estates, male biased-dispersal was detected in eight estates but no sex-biased dispersal was found in the remaining five. Neither population density nor landscape cover was found to be associated with the patterns of relatedness found across the estates. Differences in management strategies that could influence age structure, sex ratio and dispersal behaviour are proposed as potential factors influencing the relatedness patterns observed. This study provides new insights on dispersal of a strongly polygynous mammal at geographical scales relevant for management and conservation. [source] Flexible social organization and high incidence of drifting in the sweat bee, Halictus scabiosaeMOLECULAR ECOLOGY, Issue 8 2009YUKO ULRICH Abstract The very diverse social systems of sweat bees make them interesting models to study social evolution. Here we focus on the dispersal behaviour and social organization of Halictus scabiosae, a common yet poorly known species of Europe. By combining field observations and genetic data, we show that females have multiple reproductive strategies, which generates a large diversity in the social structure of nests. A detailed microsatellite analysis of 60 nests revealed that 55% of the nests contained the offspring of a single female, whereas the rest had more complex social structures, with three clear cases of multiple females reproducing in the same nest and frequent occurrence of unrelated individuals. Drifting among nests was surprisingly common, as 16% of the 122 nests in the overall sample and 44% of the nests with complex social structure contained females that had genotypes consistent with being full-sisters of females sampled in other nests of the population. Drifters originated from nests with an above-average productivity and were unrelated to their nestmates, suggesting that drifting might be a strategy to avoid competition among related females. The sex-specific comparison of genetic differentiation indicated that dispersal was male-biased, which would reinforce local resource competition among females. The pattern of genetic differentiation among populations was consistent with a dynamic process of patch colonization and extinction, as expected from the unstable, anthropogenic habitat of this species. Overall, our data show that H. scabiosae varies greatly in dispersal behaviour and social organization. The surprisingly high frequency of drifters echoes recent findings in wasps and bees, calling for further investigation of the adaptive basis of drifting in the social insects. [source] A comparison of techniques for assessing dispersal behaviour in gundis: revealing dispersal patterns in the absence of observed dispersal behaviourMOLECULAR ECOLOGY, Issue 15 2008KAREN J NUTT Abstract Knowledge of the dispersal status of group members is important to understanding how sociality may have evolved within a species. I assessed the effectiveness of four techniques for elucidating dispersal behaviour in a rock-dwelling rodent (Ctenodactylus gundi) with small group sizes (2,10 animals): genetic parentage assignment, haplotype data and kinship analyses, assignment testing, and F -statistics. The first two methods provided the greatest insight into gundi dispersal behaviour. Assignment testing and F -statistics proved of limited use for elucidating fine-scale dispersal, but could detect large-scale patterns despite low sex-biased dispersal intensity (1.9 : 1) because of moderate genetic differentiation among groups (FST = 0.10). Findings are discussed in light of current dispersal theory. In general, gundi dispersal is plastic, and seems to be dependent on body weight (for males), group composition, and scale of analysis (total dispersal events recorded within the population were almost twice the immigration rate into the population). Most groups were comprised of a single matriline and one immigrant male. Immigrant rather than philopatric males bred with group females. Dispersal among groups was male-biased, but dispersal or philopatry could occur by either sex. During a drought, both sexes delayed dispersal and cooperative social units formed. Whether such behaviour resulted directly from the drought or not remains unclear, however, since comparative information was not available from nondrought years. Combining fine-scale analyses with information on large-scale patterns provided substantial insight into gundi dispersal behaviour despite the limited movement of animals during a drought, and may prove useful for elucidating dispersal behaviour in other social animals. [source] A tale of two worlds: molecular ecology and population structure of the threatened Florida scrub-jayMOLECULAR ECOLOGY, Issue 7 2008WALTER D. KOENIG Abstract Elsewhere in this issue of Molecular Ecology, Coulon et al. provide a detailed analysis of population structure of the threatened Florida scrub-jay (Aphelocoma coerulescens) using genetic markers and compare it to that inferred from previous demographic surveys and observed dispersal behaviour in this species. In contrast to previous attempts at such comparisons, estimates from the two methods are reasonably congruent. Although challenges remain, Coulon et al.'s analyses demonstrate the potential for closing the gap between these alternative methodologies, and ultimately for future genetic surveys to be used confidently in conservation planning. [source] Phenotype matching and inbreeding avoidance in African elephantsMOLECULAR ECOLOGY, Issue 21 2007JIM MOORE Abstract Perhaps the most important ,decision' made by any animal (or plant) is whether to disperse , leave kith and kin, or remain with the familiar and related. The benefits of staying at home are obvious, so dispersal requires an explanation , and the most popular is that dispersal functions to avoid inbreeding depression. Strong support comes from the observation that dispersal is so often sex biased. Simply put, all else being equal members of both sexes should prefer to remain philopatric, but this would lead to inbreeding depression so members of one sex have to disperse. In principle, this link between inbreeding depression and sex-biased dispersal could be broken if individuals recognize close kin and avoid mating with them. Archie et al. (2007) provide one of the most compelling analyses to date of the interaction among inbreeding avoidance, kin recognition and mating strategies in any mammal, clearly showing that elephants recognize even close paternal kin and avoid mating with them. Their important results illuminate the subtleties of elephant inbreeding avoidance as well as illustrate the difficulty of arriving at definitive answers to questions about the evolution of dispersal behaviour. [source] Fine-scale spatial genetic correlation analyses reveal strong female philopatry within a brush-tailed rock-wallaby colony in southeast QueenslandMOLECULAR ECOLOGY, Issue 12 2004S. L. HAZLITT Abstract We combine spatial data on home ranges of individuals and microsatellite markers to examine patterns of fine-scale spatial genetic structure and dispersal within a brush-tailed rock-wallaby (Petrogale penicillata) colony at Hurdle Creek Valley, Queensland. Brush-tailed rock-wallabies were once abundant and widespread throughout the rocky terrain of southeastern Australia; however, populations are nearly extinct in the south of their range and in decline elsewhere. We use pairwise relatedness measures and a recent multilocus spatial autocorrelation analysis to test the hypotheses that in this species, within-colony dispersal is male-biased and that female philopatry results in spatial clusters of related females within the colony. We provide clear evidence for strong female philopatry and male-biased dispersal within this rock-wallaby colony. There was a strong, significant negative correlation between pairwise relatedness and geographical distance of individual females along only 800 m of cliff line. Spatial genetic autocorrelation analyses showed significant positive correlation for females in close proximity to each other and revealed a genetic neighbourhood size of only 600 m for females. Our study is the first to report on the fine-scale spatial genetic structure within a rock-wallaby colony and we provide the first robust evidence for strong female philopatry and spatial clustering of related females within this taxon. We discuss the ecological and conservation implications of our findings for rock-wallabies, as well as the importance of fine-scale spatial genetic patterns in studies of dispersal behaviour. [source] Repeatability of dispersal behaviour in a common dwarf spider: evidence for different mechanisms behind short- and long-distance dispersalECOLOGICAL ENTOMOLOGY, Issue 2 2009DRIES BONTE Abstract 1.,The response of dispersal towards evolution largely depends on its heritability for which upper limits are determined by the trait's repeatability. 2.,In the Linyphiid spider E. atra, we were able to separate long- and short-distance dispersal behaviours (respectively ballooning and rappelling) under laboratory conditions. By performing repeated behavioural trials for females, we show that average dispersal trait values decrease with increasing testing days. By comparing mated and unmated individuals during two periods (before and after mating for the mated group, and the same two periods for the unmated group), we show that mating has no effect on the mean displayed dispersal behaviour or its within-individual variation. Repeatabilities were high and consistent for ballooning motivation, but not for rappelling. 3.,Ballooning motivation can be regarded as highly individual-specific behaviour, while general pre-dispersal and rappelling behaviours showed more individual variation. Such difference in repeatability between long- and short-distance dispersal suggests that short- and long-distance dispersal events are triggered by different ecological and evolutionary mechanisms. [source] Fine-scale population genetic structure in a fission,fusion societyMOLECULAR ECOLOGY, Issue 11 2008ELIZABETH A. ARCHIE Abstract Nonrandom patterns of mating and dispersal create fine-scale genetic structure in natural populations , especially of social mammals , with important evolutionary and conservation genetic consequences. Such structure is well-characterized for typical mammalian societies; that is, societies where social group composition is stable, dispersal is male-biased, and males form permanent breeding associations in just one or a few social groups over the course of their lives. However, genetic structure is not well understood for social mammals that differ from this pattern, including elephants. In elephant societies, social groups fission and fuse, and males never form permanent breeding associations with female groups. Here, we combine 33 years of behavioural observations with genetic information for 545 African elephants (Loxodonta africana), to investigate how mating and dispersal behaviours structure genetic variation between social groups and across age classes. We found that, like most social mammals, female matrilocality in elephants creates co-ancestry within core social groups and significant genetic differentiation between groups (,ST = 0.058). However, unlike typical social mammals, male elephants do not bias reproduction towards a limited subset of social groups, and instead breed randomly across the population. As a result, reproductively dominant males mediate gene flow between core groups, which creates cohorts of similar-aged paternal relatives across the population. Because poaching tends to eliminate the oldest elephants from populations, illegal hunting and poaching are likely to erode fine-scale genetic structure. We discuss our results and their evolutionary and conservation genetic implications in the context of other social mammals. [source] Local and regional spatial distribution of an eruptive and a latent herbivore insect speciesAUSTRAL ECOLOGY, Issue 2 2003Katia T. Ribeiro Abstract In this work, we investigated the spatial distribution of two sessile insect herbivores over the entire range of their host plant, Coccoloba cereifera, a sclerophyllous shrub endemic to Serra do Cipó, Brazil. The two insects have very distinct life histories and dispersal behaviours and we hypothesized that their classification into behavioural syndromes could be used to predict their spatial distribution patterns. Abgrallaspis cyanophylli (Homoptera) is an armoured scale insect that fits well into the eruptive syndrome. Stenapion aff. contrarium (Coleoptera) is a petiole borer with wide search capabilities, which fits into the latent syndrome. We expected that Abgrallaspis would follow the host plant aggregation pattern whereas Stenapion would be distributed more uniformly through the region and be less affected by host aggregation. We counted the number of attacked and non-attacked ramets within two perpendicular belt transects as well as within a 20 m × 20 m quadrat placed over a dense shrub aggregation. Local quadrat covariance methods were used to estimate the spatial pattern of each insect. At fine scales, we found Stenapion evenly distributed over the host plant and Abgrallaspis with a significantly aggregated pattern. This finding is in accordance with our hypothesis. At larger scales, however, this pattern was lost and the results were largely variable. We conclude that the classification of insects into behavioural syndromes may be useful to predict distribution patterns at fine scales. At larger scales, however, history and chance events may be more important. [source] |