Probability Of Dispersal Research Articles

Natal and Breeding Dispersal in Mute SwansCygnus olor: Influence of Sex, Mate Switching and Reproductive Success

Dispersive behaviour in birds is shaped by a set of different external factors (climate, human pressure, territory quality), as well as by internal constraints (reproductive strategy, sex, age, competitive abilities). Natal and breeding dispersal was studied in the migratory population of the Mute Swan Cygnus olor in Poland. The species showed male-biased natal dispersal with mean dispersal distance of 99.7 ± 20.0 km for males and 17.7 ± 5.4 km for females. Consistently, larger proportion of female swans showed natal philopatry, when compared with males (36.4% vs. 9.1%). The dispersal distance has shortened over the last three decades. This tendency prevailed in males and was associated with reduction in annual migration distance due to milder winters and adaptation for wintering in urban areas. Analysis of breeding dispersal showed that only 12.3% of breeding attempts were associated with changing territories (N = 945). Breeding dispersal distance was female-biased (0.66 ± 0.19 km for females vs. 0.35 ± 0.14 for males; N = 316 individuals). Occurrence of mate-switching and poor reproductive success were positively associated with probability of dispersal, but moving to a new territory did not increase breeding output in a season following dispersal event. Dispersive behaviour in the Mute Swan may be perceived as a part of species-specific ecological flexibility, allowing individuals to adjust to the changing conditions at the breeding grounds.

Self‐recruitment in aCaribbean reef fish: a method for approximating dispersal kernels accounting for seascape

Characterizing patterns of larval dispersal is essential to understanding the ecological and evolutionary dynamics of marine metapopulations. Recent research has measured local dispersal within populations, but the development of marine dispersal kernels from empirical data remains a challenge. We propose a framework to move beyond point estimates of dispersal towards the approximation of a simple dispersal kernel, based on the hypothesis that the structure of the seascape is a primary predictor of realized dispersal patterns. Using the coral reef fish Elacatinus lori as a study organism, we use genetic parentage analysis to estimate self-recruitment at a small spatial scale (<1 km). Next, we determine which simple kernel explains the observed self-recruitment, given the influx of larvae from reef habitat patches in the seascape at a large spatial scale (up to 35 km). Finally, we complete parentage analyses at six additional sites to test for export from the focal site and compare these observed dispersal data within the metapopulation to the predicted dispersal kernel. We find 4.6% self-recruitment (CI95% : ±3.0%) in the focal population, which is explained by the exponential kernel y = 0.915(x) (CI95% : y = 0.865(x) , y = 0.965(x)), given the seascape. Additional parentage analyses showed low levels of export to nearby sites, and the best-fit line through the observed dispersal proportions also revealed a declining function y = 0.77(x). This study lends direct support to the hypothesis that the probability of larval dispersal declines rapidly with distance in Atlantic gobies in continuously distributed habitat, just as it does in the Indo-Pacific damselfishes in patchily distributed habitat.

Connectivity modelling and network analysis of sea lice infection in Loch Fyne, west coast of Scotland

AEI Aquaculture Environment Interactions Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections AEI 3:51-63 (2012) - DOI: https://doi.org/10.3354/aei00052 Connectivity modelling and network analysis of sea lice infection in Loch Fyne, west coast of Scotland Thomas Adams1,*, Kenny Black1, Craig MacIntyre2, Iain MacIntyre3, Rebecca Dean4 1SAMS, Scottish Marine Institute, Dunbeg, Oban, Argyll PA37 1QA, UK 2Argyll Fisheries Trust, Cherry Park, Inveraray, Argyll PA32 8XE, UK 3The Scottish Salmon Company, Arkinglas Estate, Cairndow, Argyll PA26 8BH, UK 4The Scottish Salmon Company, Mid-Strome, Lochcarron, Ross-Shire IV54 8YH, UK *Email: tom.adams@sams.ac.uk ABSTRACT: Sea lice are a persistent threat in many areas where salmon farming is practised. In common with the management of disease, infection levels are typically controlled by operating sites within distinct geographical areas, allowing for coordinated treatment and fallow cycles. However, the hydrodynamic connectivity and consequent transmission of lice larvae between sites is often not well understood, which limits our ability to optimise the spatial distribution of farms to minimise infection. We used a multistage modelling approach to investigate the transmission of sea lice larvae between salmon aquaculture sites in Loch Fyne, Scotland. A finite element hydrodynamic model was forced using meteorological data collected over the study period. Output from this model was used to drive a particle-tracking model. The latter model implemented the development and mortality of larvae to estimate the probability of successful larval dispersal between sites. In turn, these dispersal probabilities were used to define a network describing the sea lice metapopulation (its habitat defined by the aquaculture sites). Methods from graph theory allow the identification of those sites in the network that are likely to be key for the control of sea lice in the loch population as a whole. Model outputs were compared with data from a campaign of plankton tows and with lice abundance data from aquaculture sites. The general pattern of abundance was reasonably well replicated, albeit with some notable discrepancies. These differences are worth investigating further, as they may be suggestive of sources of infection by wild fish or of inadequacies in the model. KEY WORDS: Sea lice · Connectivity · Biophysical model · Larval dispersal · Population dynamics · Lepeophtheirus salmonis Full text in pdf format Supplementary material PreviousNextCite this article as: Adams T, Black K, MacIntyre C, MacIntyre I, Dean R (2012) Connectivity modelling and network analysis of sea lice infection in Loch Fyne, west coast of Scotland. Aquacult Environ Interact 3:51-63. https://doi.org/10.3354/aei00052 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AEI Vol. 3, No. 1. Online publication date: December 19, 2012 Print ISSN: 1869-215X; Online ISSN: 1869-7534 Copyright © 2012 Inter-Research.

Predicting food‐web structure with metacommunity models

SynthesisMetacommunity theory aims to elucidate the relative influence of local and regional‐scale processes in generating diversity patterns across the landscape. Metacommunity research has focused largely on assemblages of competing organisms within a single trophic level. Here, we test the ability of metacommunity models to predict the network structure of the aquatic food web found in the leaves of the northern pitcher plant Sarracenia purpurea. The species‐sorting and patch‐dynamics models most accurately reproduced nine food web properties, suggesting that local‐scale interactions play an important role in structuring Sarracenia food webs. Our approach can be applied to any well‐resolved food web for which data are available from multiple locations.The metacommunity framework explores the relative influence of local and regional‐scale processes in generating diversity patterns across the landscape. Metacommunity models and empirical studies have focused mostly on assemblages of competing organisms within a single trophic level. Studies of multi‐trophic metacommunities are predominantly restricted to simplified trophic motifs and rarely consider entire food webs. We tested the ability of the patch‐dynamics, species‐sorting, mass‐effects, and neutral metacommunity models, as well as three hybrid models, to reproduce empirical patterns of food web structure and composition in the complex aquatic food web found in the northern pitcher plant Sarracenia purpurea. We used empirical data to determine regional species pools and estimate dispersal probabilities, simulated local food‐web dynamics, dispersed species from regional pools into local food webs at rates based on the assumptions of each metacommunity model, and tested their relative fits to empirical data on food‐web structure. The species‐sorting and patch‐dynamics models most accurately reproduced nine food web properties, suggesting that local‐scale interactions were important in structuring Sarracenia food webs. However, differences in dispersal abilities were also important in models that accurately reproduced empirical food web properties. Although the models were tested using pitcher‐plant food webs, the approach we have developed can be applied to any well‐resolved food web for which data are available from multiple locations.

Forecasting the range expansion of a recolonising wild boar Sus scrofa population

Recolonising native mammals have the potential to cause environmental and agricultural damage. However, if their future distribution can be predicted, effective control measures can be scheduled beforehand to prevent the onset of damage. In this study, we predicted the future range expansion of recolonising wild boar Sus scrofa populations in the Chiba Prefecture, Japan, using simulations. Wild boars were extinct in the Chiba Prefecture until the 1970s, but since then, a new naturalised population has spread, probably due to release for hunting. Recently a small, isolated, naturalised population was found in the northern part of the prefecture, which was considered to be a new release. We divided the Chiba Prefecture (5,156 km2) into 3‐km grids and, based on nuisance control records, we examined the ‘presence’ of wild boar populations from 2002 to 2007 and in 2010. We simultaneously estimated habitat suitability and dispersal probability of the source population via range‐expasion modelling. We predicted the future distribution by the use of stochastic simulations for 20 years after 2010. According to the simulations, the wild boar populations will expand into the southern and northern regions of the Chiba Prefecture at a rate of 2,153 km/year, and crop damage should be expected in these areas in the future. Range expansion into the northern region of the prefecture will be completed by around 2025. If the northern isolated population is removed, it will be possible to delay the range expansion for about five years. The eradication of a small isolated population in the northern Chiba Prefecture may have significant economic benefits because the crop production in this area is relatively large.

Range‐wide population genetic structure of the Caribbean sea fan coral, Gorgonia ventalina

The population structure of benthic marine organisms is of central relevance to the conservation and management of these often threatened species, as well as to the accurate understanding of their ecological and evolutionary dynamics. A growing body of evidence suggests that marine populations can be structured over short distances despite theoretically high dispersal potential. Yet the proposed mechanisms governing this structure vary, and existing empirical population genetic evidence is of insufficient taxonomic and geographic scope to allow for strong general inferences. Here, we describe the range-wide population genetic structure of an ecologically important Caribbean octocoral, Gorgonia ventalina. Genetic differentiation was positively correlated with geographic distance and negatively correlated with oceanographically modelled dispersal probability throughout the range. Although we observed admixture across hundreds of kilometres, estimated dispersal was low, and populations were differentiated across distances <2 km. These results suggest that populations of G. ventalina may be evolutionarily coupled via gene flow but are largely demographically independent. Observed patterns of differentiation corroborate biogeographic breaks found in other taxa (e.g. an east/west divide near Puerto Rico), and also identify population divides not discussed in previous studies (e.g. the Yucatan Channel). High genotypic diversity and absence of clonemates indicate that sex is the primary reproductive mode for G. ventalina. A comparative analysis of the population structure of G. ventalina and its dinoflagellate symbiont, Symbiodinium, indicates that the dispersal of these symbiotic partners is not coupled, and symbiont transmission occurs horizontally.

Can brief marking campaigns provide reliable dispersal estimates? A Nickerl’s Fritillary (&lt;i&gt;Melitaea aurelia&lt;/i&gt;, Lepidoptera: Nymphalidae) case study

Functions expressing dispersal probability decays with increasing distance are widely used in studies of animal movements. The inverse power function (IPF) exhibits the property of self-similarity, and hence should perform robustly against variation in marking efforts, allowing comparisons across studies. We investigated this function property using dispersal data of Nickerl’s fritillary (Melitaea aurelia), a little studied checkerspot butterfly which is currently expanding in Central Europe. During mark-recapture in South Moravia, Czech Republic, a single researcher worked for the entire flight period in 2005, while in 2006 five researchers worked for just 5 days. Slopes of the fitted functions did not differ between the two seasons, illustrating the robustness of the function and suggesting the possibility to obtain reliable dispersal estimates even from brief marking campaigns. For both years, it was predicted that approximately one individual per one thousand would cross 10 km distance, the maximum distance separating the most isolated colonies in the region.

Evolution of dispersal in metacommunities of interacting species

Theoretical studies on the evolution of dispersal in metacommunities are rare despite empirical evidence suggesting that interspecific interactions can modify dispersal behaviour of organisms. To understand the role of species interactions for dispersal evolution, we utilize an individual-based model of a metacommunity where local population dynamics follows a stochastic version of the Nicholson-Bailey model and dispersal probability is an evolving trait. Our results show that in comparison with a neutral system (commensalism), parasitism promotes dispersal of hosts and parasites, while mutualism tends to reduce dispersal in both partners. Search efficiency of guests (only in the case of parasitism), dispersal mortality and external extinction risk can influence the evolution of dispersal of all partners. In systems composed of two host and two guest species, lower dispersal probabilities evolve under parasitism as well as mutualism than in one host and one guest species systems. This is because of frequency-dependent modulations of dispersal benefits emerging in such systems for all partners.

Concurrent evolution of random dispersal and habitat niche width in host-parasitoid systems

Antagonistic interactions like those between hosts and parasites or parasitoids or between predators and prey are important for many ecological and evolutionary processes. Here, we contrast the effect of commensalism and host-parasitoid interaction (complete fertility loss for infected host), on the concurrent evolution of host dispersal and habitat niche width. We assume that host habitat niche width is associated with a fertility trade-off; the wider the habitat niche, the lower the maximum fertility in optimal habitats. We implement a spatially explicit, individual-based one-host-one-guest metacommunity model (guest species are commensals or parasitoids) with landscape heterogeneity of a continuous habitat trait that affects the host's fertility only. The antagonistic interaction model follows the Nicholson–Bailey equation.Compared to commensalism, the host-parasitoid interaction promotes the evolution of higher dispersal probability in hosts and guests. In comparison to homogeneous landscapes, lower dispersal probabilities of both hosts and guests evolve in heterogeneous landscapes. Other than in homogeneous landscapes, parasitoids typically evolve higher dispersal probabilities than their hosts in heterogeneous landscapes. The effect of landscape heterogeneity on dispersal evolution depends on the magnitude of the habitat–fertility trade-off for hosts and the search efficiency of parasitoids. Moreover, depending on the habitat–fertility trade-off, antagonistic interactions may promote evolution of habitat niche width in hosts. Landscape structure affects the evolution of dispersal and habitat niche width in opposite ways: in clustered (autocorrelated) landscapes, dispersal probability evolves to higher, but habitat niche width to lower levels than in random landscapes.

Contrasting effects of climatic variability on the demography of a trans‐equatorial migratory seabird

Large-scale seasonal climatic indices, such as the North Atlantic Oscillation (NAO) index or the Southern Oscillation Index (SOI), account for major variations in weather and climate around the world and may influence population dynamics in many organisms. However, assessing the extent of climate impacts on species and their life-history traits requires reliable quantitative statistical approaches. We used a new analytical tool in mark-recapture, the multi-event modelling, to simultaneously assess the influence of climatic variation on multiple demographic parameters (i.e. adult survival, transient probability, reproductive skipping and nest dispersal) at two Mediterranean colonies of the Cory's shearwater Calonectris diomedea, a trans-equatorial migratory long-lived seabird. We also analysed the impact of climate in the breeding success at the two colonies. We found a clear temporal variation of survival for Cory's shearwaters, strongly associated to the large-scale SOI especially in one of the colonies (up to 66% of variance explained). Atlantic hurricane season is modulated by the SOI and coincides with shearwater migration to their wintering areas, directly affecting survival probabilities. However, the SOI was a better predictor of survival probabilities than the frequency of hurricanes; thus, we cannot discard an indirect additive effect of SOI via food availability. Accordingly, the proportion of transients was also correlated with SOI values, indicating higher costs of first reproduction (resulting in either mortality or permanent dispersal) when bad environmental conditions occurred during winter before reproduction. Breeding success was also affected by climatic factors, the NAO explaining c. 41% of variance, probably as a result of its effect in the timing of peak abundance of squid and small pelagics, the main prey for shearwaters. No climatic effect was found either on reproductive skipping or on nest dispersal. Contrarily to what we expect for a long-lived organism, large-scale climatic indexes had a more pronounced effect on survival and transient probabilities than on less sensitive fitness parameters such reproductive skipping or nest dispersal probabilities. The potential increase in hurricane frequency because of global warming may interact with other global change agents (such as incidental bycatch and predation by alien species) nowadays impacting shearwaters, affecting future viability of populations.

A new approach to the “apparent survival” problem: estimating true survival rates from mark–recapture studies

Survival estimates generated from live capture-mark-recapture studies may be negatively biased due to the permanent emigration of marked individuals from the study area. In the absence of a robust analytical solution, researchers typically sidestep this problem by simply reporting estimates using the term "apparent survival." Here, we present a hierarchical Bayesian multistate model designed to estimate true survival by accounting for predicted rates of permanent emigration. Initially we use dispersal kernels to generate spatial projections of dispersal probability around each capture location. From these projections, we estimate emigration probability for each marked individual and use the resulting values to generate bias-adjusted survival estimates from individual capture histories. When tested using simulated data sets featuring variable detection probabilities, survival rates, and dispersal patterns, the model consistently eliminated negative biases shown by apparent survival estimates from standard models. When applied to a case study concerning juvenile survival in the endangered Cape Sable Seaside Sparrow (Ammodramus maritimus mirabilis), bias-adjusted survival estimates increased more than twofold above apparent survival estimates. Our approach is applicable to any capture-mark-recapture study design and should be particularly valuable for organisms with dispersive juvenile life stages.

Identification of subpopulations from connectivity matrices

Dispersal on the landscape/seascape scale may lead to complex spatial population structure with non‐synchronous demography and genetic divergence. In this study we present a novel approach to identify subpopulations and dispersal barriers based on estimates of dispersal probabilities on the landscape scale. A theoretical framework is presented where the landscape connectivity matrix is analyzed for clusters as a signature of partially isolated subpopulations. Identification of subpopulations is formulated as a minimization problem with a tuneable penalty term that makes it possible to generate population subdivisions with varying degree of dispersal restrictions. We show that this approach produces superior results compared to alternative standard methods. We apply this theory to a dataset of modeled dispersal probabilities for a sessile marine invertebrate with free‐swimming larvae in the Baltic Sea. For a range of critical connectivities we produce a hierarchical partitioning into subpopulations spanning dispersal probabilities that are typical for both genetic divergence and demographic independence. The mapping of subpopulations suggests that the Baltic Sea includes a fine‐scale (100–600 km) mosaic of invisible dispersal barriers. An analysis of the present network of marine protected areas reveal that protection is very unevenly distributed among the suggested subpopulations. Our approach can be used to assess the location and strength of dispersal barriers in the landscape, and identify conservation units when extensive genotyping is prohibitively costly to cover necessary spatial and temporal scales, e.g. in spatial management of marine populations.

Stable‐hydrogen isotope measures of natal dispersal reflect observed population declines in a threatened migratory songbird

AbstractAimMeasuring dispersal is crucial for estimating demographic rates that inform conservation plans for rare and threatened species. We evaluated natal dispersal patterns in Bicknell's thrush (Catharus bicknelli) across most of the breeding range using a 10‐year data set of stable‐hydrogen isotope ratios in feathers (δ2HF) grown on the natal area and sampled 1 year later at the first breeding site.LocationNorth‐eastern United States and south‐eastern Canada.MethodsWe used δ2HF values of adult thrushes sampled at 25 breeding sites as prior information for assigning first‐time breeders to their natal site. We calculated the minimum distance birds moved from their natal to first breeding site and fit these data to three statistical distributions for characterizing the importance of long‐distance dispersal: the exponential, Weibull and half‐Cauchy. Finally, we assessed differences in the probability of dispersal across the breeding range and through time to understand spatio‐temporal variation in demographic connectivity.ResultsThe δ2HF values of first‐time breeders were lower compared with those of adults, a difference that was greater at the southern compared with northern breeding range extreme. Assignment tests accounting for age differences in δ2HF suggested that most birds dispersed &lt; 200 km from their natal area and within the centre of the breeding range, whereas comparatively few individuals dispersed up to 700 km. A Weibull distribution provided the best fit to these data. Two of three corrections for age differences in δ2HF indicated that natal dispersal probability declined by 30–38% from 1996 to 2005.Main conclusionsOur findings suggest that estimating natal dispersal with δ2HF measurements may contribute to understanding the resilience of geographically isolated Bicknell's thrush populations. Declining natal dispersal may be symptomatic of observed population declines and could compound this trend by limiting demographic exchange between habitat patches predicted to be increasingly isolated by natural and anthropogenic habitat changes.

A multi‐event model to study stage‐dependent dispersal in radio‐collared hares: when hunting promotes costly transience

Behavioral ecologists have often assumed that dispersal is costly mainly because of unfamiliarity with traversed habitats during dispersal and energy costs of the movement per se; thus, dispersers that have successfully settled should experience survival rates comparable to those of philopatric individuals. In this paper, we tested that hypothesis using 152 radio-collared European hares in a harvested population. We developed a multi-event capture recapture model, combining telemetry data and recoveries and separately modeling the foray probability, the settlement probability, and the permanent dispersal probability. The parameterization introduced here raises the possibility of separately testing effects on survival and dispersal probabilities at each stage of dispersal (departure, transience, and settlement). In accordance with our expectations, we reveal that dispersers incur higher mortality risks during transience and the early settlement period than philopatric individuals or settled dispersers. We also found that dispersers suffer from higher risks of being shot. Those results illustrate that unfamiliarity with the habitat during transience makes dispersal costly and that settled dispersers may enjoy survival rates comparable to those of philopatric individuals. Surprisingly, we also found that individuals have a higher probability of foraying during the hunting season. We suggest that hunting and related disturbances increase dispersal costs both by increasing mortality risk during transience and (perhaps) by increasing movement rates. We emphasize the need to take human pressures into account as factors that may drive the demographics of movements in populations.

Using dispersal information to model the species–environment relationship of spreading non‐native species

Summary1. Non‐native species can be major drivers of biodiversity loss and cause economic damage. Predicting the potential distribution of a non‐native species, and understanding the environmental factors that limit this distribution, is useful for informing their potential management. This is often carried out using species distribution models (SDMs) that attempt to classify grid cells as suitable or unsuitable for a species based on a set of environmental covariates.2. A key assumption of SDMs is that a species is in equilibrium with its environment. Spreading non‐native species often violate this assumption due to dispersal limitation.3. We present a simple method for dealing with this problem: dispersal weighting (DW). This uses the probability that a species can disperse to a grid cell to weight a SDM. We use simulations to compare the ability of DW and unweighted models at parameterising the true species–environment relationship (SER) of a simulated species, and to test their ability at predicting the future distribution of this species. We investigate how varying the degree of spatial autocorrelation in explanatory variables affects the performance of the methods.4. Dispersal weighting models outperformed unweighted models at parameterising the SER, and at predicting the future distribution of the species when dispersal probabilities were incorporated into the model predictions. Unweighted models had a stronger tendency than DW models to overestimate the magnitude of relationships with spatially autocorrelated explanatory variables, but underestimate the magnitude of relationships with randomly distributed variables.5. We then applied our method to a real case study, using it to model the distribution of the non‐native common waxbill Estrilda astrild in the Iberian Peninsula as a function of climate and land‐use variables. The relative performance of DW and unweighted models reflected the results of the simulation.6. We conclude that DW models perform better than unweighted models at modelling the true SER of non‐native species, and recommend using DW whenever enough data exist to create a dispersal model.

Changing Seascapes, Stochastic Connectivity, and Marine Metapopulation Dynamics

The probability of dispersal from one habitat patch to another is a key quantity in our efforts to understand and predict the dynamics of natural populations. Unfortunately, an often overlooked property of this potential connectivity is that it may change with time. In the marine realm, transient landscape features, such as mesoscale eddies and alongshore jets, produce potential connectivity that is highly variable in time. We assess the impact of this temporal variability by comparing simulations of nearshore metapopulation dynamics when potential connectivity is constant through time (i.e., when it is deterministic) and when it varies in time (i.e., when it is stochastic). We use mathematical analysis to reach general conclusions and realistic biophysical modeling to determine the actual magnitude of these changes for a specific system: nearshore marine species in the Southern California Bight. We find that in general the temporal variability of potential connectivity affects two important quantities: metapopulation growth rates when the species is rare and equilibrium abundances. Our biophysical models reveal that stochastic outcomes are almost always lower than their deterministic counterparts, sometimes by up to 40%. This has implications for how we use spatial information, such as connectivity, to manage nearshore (and other) systems.

Neighborhood effects on seed dispersal by frugivores: testing theory with a mistletoe–marsupial system in Patagonia

The outcome of the dispersal process in zoochorous plants is largely determined by the behavior of frugivorous animals. Recent simulation studies have found that fruit removal rates and mean dispersal distances are strongly affected by fruiting plant neighborhoods. We empirically tested the effects of conspecific fruiting plant neighborhoods, crop sizes, and plant accessibility on fruit removal rates and seed dispersal distances of a mistletoe species exclusively dispersed by an arboreal marsupial in Northern Patagonia. Moreover, in this study, we overcome technical limitations in the empirical estimation of seed dispersal by using a novel 15N stable isotope enrichment technique together with Bayesian mixing models that allowed us to identify dispersed seeds from focal plants without the need of extensive genotyping. We found that, as predicted by theory, plants in denser neighborhoods had greater fruit removal and shorter mean dispersal distances than more isolated plants. Furthermore, the probability of dispersing seeds farther away decreased with neighborhood density. Larger crop sizes resulted in larger fruit removal rates and smaller probabilities of longer distance dispersal. The interplay between frugivore behavioral decisions and the spatial distribution of plants could have important consequences for plant spatial dynamics.

Breeding dispersal of Eurasian Hoopoes (Upupa epops) within and between years in relation to reproductive success, sex, and age

ABSTRACT. Breeding dispersal is often affected by previous reproductive success, age, and sex. Birds with multiple broods within a season can disperse not only between, but also within, years. Little is known about factors that govern dispersal within a season or how strong it is compared with dispersal between years. We studied breeding dispersal of Eurasian Hoopoes (Upupa epops) in Valais, Switzerland, using capture-recapture data collected over 8 years (n = 712 individuals). We analyzed breeding dispersal probability and distance, both between and within years, in relation to age, sex, and reproductive output, using multistate capture-recapture models and generalized linear models. Between years, females dispersed more often and over longer distances than males (mean distance, females = 1.98 km; males = 0.83 km), but dispersal was only weakly affected by age and previous reproductive success. Dispersal within a year also differed between sexes (mean distance, females = 1.45 km; males = 0.46 km) and var...

Compounding effects on nest-site dispersal of Barn Owls Tyto alba

Capsule Recovery distances of Barn Owls ringed as pulli are conditional on ringing date but not on population density. Aims To test whether ring recovery distances (proxy for natal dispersal distances) were conditional on population density and reproductive timing. Methods We used ringing data of pulli ringed in Denmark (1921–2009; n = 590) and glmms to test density, recovery time, ringing date and brood size for their influence on dispersal probability and recovery distance. Results The probability of being recovered > 1 km from the nest-site as well as total recovery distances increased steeply from 0 to 100 days after ringing, being stable thereafter, and was also impacted by brood size. Owls ringed very early or late in the breeding season were more likely to be recovered < 1 km from the nest-site at a recovery time where dispersal seemed to be completed. Conclusions Owls from early and late broods showed lower dispersal distances than others on average, despite non-philopatric owls having equal recovery distances regardless of ringing date. Overall, dispersal probability and recovery distances did not correlate with population density, but there is some evidence that young owls dispersed faster in denser populations.

Spatial and temporal arrival patterns of Madagascar's vertebrate fauna explained by distance, ocean currents, and ancestor type

How, when, and from where Madagascar's vertebrates arrived on the island is poorly known, and a comprehensive explanation for the distribution of its organisms has yet to emerge. We begin to break that impasse by analyzing vertebrate arrival patterns implied by currently existing taxa. For each of 81 clades, we compiled arrival date, source, and ancestor type (obligate freshwater, terrestrial, facultative swimmer, or volant). We analyzed changes in arrival rates, with and without adjusting for clade extinction. Probability of successful transoceanic dispersal is negatively correlated with distance traveled and influenced by ocean currents and ancestor type. Obligate rafters show a decrease in probability of successful transoceanic dispersal from the Paleocene onward, reaching the lowest levels after the mid-Miocene. This finding is consistent with a paleoceanographic model [Ali JR, Huber M (2010) Nature 463:653-656] that predicts Early Cenozoic surface currents periodically conducive to rafting or swimming from Africa, followed by a reconfiguration to present-day flow 15-20 million years ago that significantly diminished the ability for transoceanic dispersal to Madagascar from the adjacent mainland.