Dispersal of the emerald ash borer, Agrilus planipennis, in newly-colonized sites

• 1 Emerald ash borer Agrilus planipennis Fairmaire (Coleoptera: Buprestidae) is an invasive forest insect pest threatening more than 8 billion ash (Fraxinus spp.) trees in North America. Development of effective survey methods and strategies to slow the spread of A. planipennis requires an understanding of dispersal, particularly in recently established satellite populations.
• 2 We assessed the dispersal of A. planipennis beetles over a single generation at two sites by intensively sampling ash trees at known distances from infested ash logs, the point source of the infestations. Larval density was recorded from more than 100 trees at each site.
• 3 Density of A. planipennis larvae by distance for one site was fit to the Ricker function, inverse power function, and the negative exponential function using a maximum likelihood approach. The prediction of the best model, a negative exponential function, was compared with the results from both sites.
• 4 The present study demonstrates that larval densities rapidly declined with distance, and that most larvae (88.9 and 90.3%) were on trees within 100 m of the emergence point of the adults at each site. The larval distribution pattern observed at both sites was adequately described by the negative exponential function.

     

Dispersal,ranging and settling behaviour of Marsh Tits Poecile palustris in a fragmented landscape in lowland England

Capsule Natal dispersal was rapid and distances were short. Winter ranging and breeding dispersal were limited. Few birds undertook large movements.

Aims To investigate the natal and breeding dispersal of Marsh Tits, including the timing of dispersal movements.

Methods Nestlings, juveniles and adults were ringed and searched for over 4500 ha during summer, autumn–winter, and spring over six years. Dispersal distances were measured as metric distances and multiples of territory widths. Ranging distances were compared with dispersal distances.

Results Median distances of natal dispersal were 2.6 territory widths for males (704.5 m) and 3.1 territory widths for females (1065.0 m). Median distances of breeding dispersal were 0.2 territory widths for males and females (58.6 and 53.1 m respectively). Most natal dispersal was completed soon after independence, with further movement in spring. Breeding dispersal was also detected during these periods. Median ranging distances were short, and some winter floaters were identified.

Conclusion Marsh Tits had short dispersal distances, with most dispersal activity occurring in June. Results suggested that dispersal behaviour was sensitive to habitat fragmentation, resulting in poor settling success outside of the natal wood. Habitat fragmentation may, therefore, be a contributory factor in the decline of the Marsh Tit population in Britain.     

Dispersal and dormancy strategies among insect species competing for a pulsed resource

相似文献   

Limited dispersal and its effect on population structure in the milkweed beetle Tetraopes tetraophthalmus

Summary The movement patterns of adult milkweed beetles, Tetraopes tetraphthalmus, were monitored via a mark-recapture technique. Movement or dispersal patterns were studied in two natural populations, one in which the host plant, Asclepias syriaca, was nearly continuously distributed over a 250×90 m area and another where Asclepias was distributed in 17 small discrete patches. In both populations dispersal distances resulting from the flight patterns of the adult beetles were quite short, averaging less than 40 m from the point of first encounter 10 days after marking. Males were shown to be more vagile than females. The distribution of dispersal distances collected from one of the populations was fit to three statistical distributions cited in the literature as expected from dispersal by many small-scale movements or observed in other species. It was found that an equation describing an exponential decay gave the best statistical fit to the data collected here for milkweed beetles. The data is discussed in the context of the effects of the limited dispersal power of the beetles and the distribution of suitable habitat on the population structure of Tetraopes.     

Movements of adult fish in a hybrid zone revealed by microsatellite genetic analysis and capture-recapture data

• 1 Barbus barbus and Barbus meridionalis (Cyprinidae) form a hybrid zone in the Lergue river (southern France). We attempted to characterise the pattern of adult dispersal with the aim of understanding the evolutionary interactions maintaining this hybrid zone. In a previous capture/recapture study, movements between localities at a distance of 2.5 km or more appeared extremely rare. We therefore decided to investigate adult movement using a different method, based on genetic markers.
• 2 As this hybrid zone has produced allele frequency clines, massive population movements would produce temporal variations in genetic composition at a given locality. In order to determine the relationship between gene frequency and position, we surveyed four diagnostic or semidiagnostic microsatellite loci over the hybrid zone and estimated the cline produced by introgression. Then, we focused on a single locality at the centre of the hybrid zone and established its introgression index over 11 periods during two years.
• 3 The introgression index varied between periods producing significant Fst. A synthetic hybrid index, based on principal component analysis of the logit frequencies, was used for regression analyses and appeared significantly correlated with the river flow. This may be explained by displacement of adult fishes in response to flow increase. Using the information from the cline, we estimate that the most important gene frequency changes among dates, if created exclusively by population movement, correspond to a distance of 1500 m.
• 4 Additionally, we performed recaptures on a finer geographic scale than previously, around the central locality. No recaptured fishes were observed at 1875 m or more downstream, and at 875 m or more upstream, from the central locality. A high proportion of recaptured fishes (20% and 12%) was found in the nearest points (312 m downstream and 437 m upstream, respectively).
• 5 Thus, we established that (i) individual movements appear limited to a few hundred metres and (ii) individuals in a location tend to move in the same direction at the same time, probably in response to the same environmental factor.

     

Adult movements between populations in the specialist butterfly Proclossiana eunomia (Lepidoptera, Nymphalidae)

Abstract.

• 1 The structure of local populations of a monophagous butterfly, the bog fritillary Proclossiana eunomia, was studied in a complex of suitable habitat patches separated by spruce plantations or fertilized pasture.
• 2 An unexpected high level of adult movements between habitat patches was detected by a mark—release—recapture technique. Local populations were connected by adult movements across unsuitable habitats, leading to a meta-population structure.
• 3 This evidence of the metapopulation structure of a specialist butterfly challenges the supposed relationship between habitat specialization and closed, isolated populations.
• 4 Males and females of P.eunomia exhibited different spatial behaviours; females were more likely to emigrate and dispersed further than males. These differences in spatial behaviour are related to the mating system.

     

Hydrodynamics and seed dispersal in the lower Amazon

相似文献   

Adaptive dispersal and appetitive flight in the green lacewing, Chrysopa cornea

Abstract.

• 1 The flight behaviour of Chrysopa cornea Steph. (Neuroptera: Chrysopidae) with regard to dispersal activity has been investigated in field experiments. There are three main types of flight activities.
• 2 Shortly after emergence (in the first two nights) the adults perform adaptive dispersal flights which are straight downwind flights mostly at elevations higher than 3 m above ground. The lacewings do not react to the presence of honey dew in the crop.
• 3 After 2—3 days the scent of honeydew becomes a strong landing stimulus. The flight is now an appetitive downwind flight which usually is lower than 3 m above ground.
• 4 Once landed, the lacewings' subsequent flights are toward the source of the kairomone which signals honeydew. This can be termed appetitive upwind flight. It is a low stepwise flight within the ‘boundary layer’ which rarely exceeds 1 m above crop level.
• 5 Dispersal takes place in a continuous ‘rolling’ downwind movement of the whole lacewing population. The immigration rate into a field is thus not a function of the quality of that field but rather of upwind fields. Emigration, however, strongly depends on the presence of honeydew (retaining of ovipositing immigrants) and the density of aphids or other food for the larvae (production of new adults).

     

Habitat use and dispersal characteristic by <Emphasis Type="Italic">Stethophyma grossum</Emphasis>: the role of habitat isolation and stable habitat conditions towards low dispersal

Species in a highly fragmented environment, such as the intensively used agricultural landscapes of Europe, are expected to be in danger of extinction. We hypothesize according to Kisdi’s theory (Am Nat 159:579–596, 2002) that species in fragmented landscapes with isolated habitats in general tend to possess low dispersal. In order to verify this hypothesis we studied the movement patterns of Stethophyma grossum, a hygrophilous species of wetlands, by mark–release–recapture techniques in a landscape with scattered suitable habitats over 3 years. The study focused on the major population in this landscape (site #1) as dispersal behaviour was assumed to be greatest. Actually, marked individuals of S. grossum were never found in any further suitable habitats in close vicinity to site #1. Despite that the peatland meadow of study site #1 was all over covered with homogenous vegetation only 6% (1.8 ha) of the whole area (30 ha) were occupied by S. grossum. The mean recapture rate over 3 years amounted to 39% with no significant differences between males and females. Both covered little distances within their mean range size of 1.8 ha; the median distances were 36.91 m for males and 26.65 m for females. We confirm the hypothesis that sub-populations of species in longstanding naturally isolated habitats, which habitat conditions have been stable; evolved low dispersal with little movements which are routine movements to find mating partners or food.     

Dispersal and genetic differentiation of Syntrichia caninervis populations across different desert regions in China

• The moss Syntrichia caninervis is widely distributed in cool temperate and cold deserts where environmental pressures create a dependence on asexual reproduction (fragment reproduction). However, when compared to sporophyte‐producing mosses, there is a lack of evidence to support the capacity of drought‐tolerant mosses that predominantly fragment and produce protonema to disperse over long distances.
• We used 20 microsatellite loci to study genetic variation and structure in six populations (five natural populations and one population from a regeneration site) in three contrasting and widely separated regions of China.
• The genetic diversity and expected heterozygosity were lower in populations from the Tengger Desert than in populations from the other regions. Using PCoA, UPGMA and Structure analysis, the genetic grouping divided the three regions into three distinct groups. This may indicate that in regions where S. caninervis reproduces predominantly asexually, propagules are spread mainly by short‐distance dispersal. The genetic diversity of the population from the regeneration site in the Tengger Desert was slightly higher than that of the nearby, naturally occurring population, and included some input from the Pamir Plateau almost 2,300 km to the west, suggesting long‐distance dispersal of S. caninervis propagules across the region.
• Predominantly asexually reproducing populations of S. caninervis are mainly dependent on short‐distance dispersal. Long‐distance dispersal of S. caninervis propagules across the region is difficult. Establishment of populations with dominant asexual reproduction will eventually result in genetic differentiation.

     

Characteristics of dispersal in sexually mature dragonflies

Abstract.

• 1 The population dynamics of a natural population of Sympetrum danae (Sulzer) were studied, by means of a mark—release—recapture method, to find indications of dispersal by mature adults. Additional information on orientation and the influence of phenotype (including age), density and weather was obtained by observations under natural conditions and in a large outdoor field cage.
• 2 80% of all mature adults caught around the natural pond were estimated to be immigrants. Considerable immigration was confirmed by the abdomen length of unmarked matures which did not accord with that expected from the locally emerged population. Total numbers captured and the minimum number known to be alive fell sharply at the time when most individuals were mature. At the same time, new matures continued to enter and disappear from the study area at an increasing rate.
• 3 Dispersive behaviour (escape flights) in the field enclosure was primarily age dependent in both sexes: it occurred from an age of 25–30 days onwards. This coincides with the time-lag between the emergence peak and increased dispersal in the field. Secondary effects on escape flights suggested that males tended to abandon low density areas.
• 4 Males flew relatively more southward than females.

     

Unexplained patterns of grey wolf Canis lupus natal dispersal

Natal dispersal (movement from the site of birth to the site of reproduction) is a pervasive but highly varied characteristic of life forms. Thus, understanding it in any species informs many aspects of biology, but studying it in most species is difficult. In the grey wolf Canis lupus, natal dispersal has been well studied. Maturing members of both sexes generally leave their natal packs, pair with opposite-sex dispersers from other packs, near or far, select a territory, and produce their own offspring. However, three movement patterns of some natal-dispersing wolves remain unexplained: 1) long-distance dispersal when potential mates seem nearby, 2) round-trip travels from their natal packs for varying periods and distances, also called extraterritorial movements, and often not resulting in pairing, and 3) coincidental dispersal by individual wolves from a given area in the same basic directions and over the same long distances. This perspective article documents and discusses these unexplained dispersal patterns, suggests possible explanations, and calls for additional research to understand them more clearly.     

Home Range and Movement Patterns of Toucans: Implications for Seed Dispersal

Toucans (Ramphastidae) are highly frugivorous, widespread throughout the Neotropics, and travel long distances, thus likely providing dispersal for many tropical trees. Despite being large conspicuous members of the canopy and subcanopy bird community, their movement ecology has been little studied. To understand how these frugivores move through a lowland tropical forest, I tracked the movements of Ramphastos tucanus (White‐throated Toucan), Ramphastos vitellinus (Channel‐billed Toucan), and Pteroglossus pluricinctus (Many‐banded Araçari) in Yasuní National Park, Ecuador. The objectives of this study were to use radiotelemetry to estimate toucan home ranges, movement patterns, and potential seed dispersal distances. Using canopy nets, a total of 20 P. pluricinctus and three Ramphastos toucans were captured, radio‐tagged, and tracked over a 4‐yr period from 2001 to 2005. Average home range sizes were 191 and 86 ha for P. pluricinctus and Ramphastos toucans, respectively. The maximum travel distance in a single 30‐min tracking interval was 3665 m for P. pluricinctus and 3027 m for Ramphastos. Estimated dispersal distances of medium‐sized seeds ranged from 269 to 449 m. Large home range size and long‐distance movements indicate that toucans likely disperse seeds over a scale of hundreds of meters. This study is the first to estimate home range size of any toucan species in intact closed‐canopy forests. Abstract in Spanish is available at http://www.blackwell‐synergy.com/loi/btp .     

Dispersal potential of spores and asexual propagules in the epixylic hepatic Anastrophyllum hellerianum

Dispersal ability is of great importance for plants, which commonly occupy spatially and temporally limited substrate patches. Mixed reproductive strategies with abundant diaspore production are favoured in a heterogeneous landscape to ensure successful colonisation at different distances. In bryophytes, long-distance dispersal has been thought to take place primarily by spores, while asexual propagules are important in local dispersal and in the maintenance of colonies. In the present study, we investigated the dispersal potential of two equally sized propagules, sexually formed spores and asexually produced gemmae in the dioecious, epixylic hepatic, Anastrophyllum hellerianum, which inhabits spatially and temporally limited substrate patches. We trapped propagules at different distances (0–10 m) and directions from the source colonies in two experiments: one in a natural habitat within a forest and another involving an artificial set-up in an open habitat. Spore dispersal showed only slight distance dependence both in the open and the forest habitats, presumably as a consequence of wind affecting the dispersal pattern. Gemma dispersal was more strongly distance-dependent in the open habitat than in the forest sites. Considerably more gemmae were deposited during rainy than dry periods, possibly because of the effect of rain drops on gemma release. However, weather conditions had no effect on the dispersal patterns of spores or gemmae. In A. hellerianum, the combination of occasional spore production and practically continuous, massive gemma production facilitates dispersal both on local scale and over long distances. Unlike previously assumed, not only spores but also the asexual propagules may contribute to long-distance dispersal, thus allowing considerable gene flow at the landscape level.     

Do pools impede drift dispersal by stream insects?

相似文献   

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.     

Spatial connectivity in an adult‐sedentary reef fish with extended pelagic larval phase

Understanding the spatial scale of demographic connectivity in marine reef fishes dispersing pelagic larvae is a challenging task because of the technical difficulties associated with tagging and monitoring the movements of progeny at early life stages. Several studies highlighted a strong importance of local retention with levels of dispersal of ecological significance restricted to short distances. To date little information is available in species where pelagic dispersal lasts for long periods of time. In this work, population structure and connectivity were studied in the grey triggerfish, Balistes capriscus. Grey triggerfish larvae and juveniles remain associated with floating Sargassum sp. beds for an estimated period of 4–7 months before settling on benthic habitats where they remain sedentary as adults. Analysis of genetic variation among populations along the continental shelf of the northern Gulf of Mexico and U.S. east coast, encompassing over 3,100 km of coastline, revealed homogeneous allele frequencies and a weak isolation‐by‐distance pattern. Moment and maximum‐likelihood estimates of dispersal parameters both indicated occurrence of large neighbourhoods with estimates of the dispersal distribution parameter σ of 914 and 780 km, respectively. Simulated distributions of dispersal distances using several distribution functions all featured substantial fractions of long‐distance dispersal events with the 90% percentiles of travel distance prior to settlement averaging 1,809 km. These results suggest a high dependency of local recruitment on the output of nonlocal spawning stocks located hundreds of kilometres away and a reduced role of local retention in this species.     

Migration and dispersal patterns of bats and their influence on genetic structure

相似文献   

When genes go wild: highly variable internal transcibed spacer1 and conserved mitochondrial DNA haplotypes used to examine the genetic diversity and dispersal pathways of invasive Hylotrupes bajulus in Western Australia

相似文献