Reduced genetic variation in Norwegian Peregrine Falcons Falco peregrinus indicated by minisatellite DNA fingerprinting

The Scandinavian Peregrine Falcon Falco peregrinus population went through a severe population bottleneck during the second half of the twentieth century, and was almost extinct during the 1970s. This event may have reduced the amount of genetic variation in the population. With this background, a comparative study, using multilocus, minisatellite DNA fingerprinting, was carried out on broods of the Peregrine Falcon, the Merlin Falco columbarius and the Eurasian Hobby Falco subbuteo from south-east Norway. Band-sharing analysis of DNA fingerprints was used to test whether broods of Peregrine Falcons showed a greater between-nest similarity in their fingerprint profiles than did broods of the two congeneric species breeding in the same region, which have not undergone any recent population bottlenecks. The results show that broods of Peregrine Falcons were significantly more similar to each other genetically than were broods of either Merlins or Eurasian Hobbies. Furthermore, there was a positive correlation between the similarity in minisatellite DNA and the similarity in a set of 11 microsatellite loci analysed for a subset of the Peregrine Falcon samples. The correlation supports the assumption that minisatellite fingerprints provide a reliable indicator of overall genetic similarity, i.e. relatedness, between breeding pairs in the population. Hence we can conclude that broods of Peregrine Falcons were genetically more related to each other than were broods of the other two species. The high similarity in minisatellite DNA between broods indicates a loss of genetic variation in the Peregrine Falcon population caused by the bottleneck, but this explanation can only be verified through a comparative genetic study of individuals sampled before and after the bottleneck event.     

THE INFLUENCE OF HABITAT ON THE DISTRIBUTION AND ABUNDANCE OF PEREGRINE AND LANNER FALCONS IN SOUTH AFRICA

Jenkins, A.R. 1994. The influence of habitat on the distribution and abundance of Peregrine and Lanner Falcons in South Africa. Ostrich 65: 281–290.

The distribution and abundance of Peregrine and Lanner Falcons in South Africa was compared using recorded sightings from various sources, including the Southern African Bird Atlas Project. Falcon distributions were compared with the distribution of cliffs and vegetation, to quantify differences in the habitat preferences of the two species in the breeding and the non-breeding seasons. Lanner Falcons outnumbered Peregrine Falcons in most areas by at least 10:1. Peregrine Falcons were more habitat specific than Lanner Falcons, in terms of topographic and biotic requirements. Peregrine Falcons were largely restricted to high cliff areas throughout the year and there probably were no large-scale seasonal movements within the population. The bulk of the resident Peregrine Falcon population was found in the fynbos biome, in the southwestern Cape. Outside of this area, Peregrine Falcons were concentrated in woodlands. Lanner Falcons were less dependent on high cliffs, although cliff availability was important in defining the ranges of both species. Lanner Falcons were most common in the sour grasslands in the east of the country in the breeding season, with apparent movements in the non-breeding season into the fynbos, the Nama Karoo and the southern Kalahari. Overall, Peregrine Falcons favoured relatively closed habitats and Lanner Falcons favoured relatively open habitats. The differences in the two species' habitat preferences are proximate factors influencing distribution and abundance.     

Restricted mating dispersal and strong breeding group structure in a mid-sized marsupial mammal (Petrogale penicillata)

Ecological genetic studies have demonstrated that spatial patterns of mating dispersal, the dispersal of gametes through mating behaviour, can facilitate inbreeding avoidance and strongly influence the structure of populations, particularly in highly philopatric species. Elements of breeding group dynamics, such as strong structuring and sex-biased dispersal among groups, can also minimize inbreeding and positively influence levels of genetic diversity within populations. Rock-wallabies are highly philopatric mid-sized mammals whose strong dependence on rocky terrain has resulted in series of discreet, small colonies in the landscape. Populations show no signs of inbreeding and maintain high levels of genetic diversity despite strong patterns of limited gene flow within and among colonies. We used this species to investigate the importance of mating dispersal and breeding group structure to inbreeding avoidance within a 'small' population. We examined the spatial patterns of mating dispersal, the extent of kinship within breeding groups, and the degree of relatedness among brush-tailed rock-wallaby breeding pairs within a colony in southeast Queensland. Parentage data revealed remarkably restricted mating dispersal and strong breeding group structuring for a mid-sized mammal. Breeding groups showed significant levels of female kinship with evidence of male dispersal among groups. We found no evidence for inbreeding avoidance through mate choice; however, anecdotal data suggest the importance of life history traits to inbreeding avoidance between first-degree relatives. We suggest that the restricted pattern of mating dispersal and strong breeding group structuring facilitates inbreeding avoidance within colonies. These results provide insight into the population structure and maintenance of genetic diversity within colonies of the threatened brush-tailed rock-wallaby.     

Low genetic differentiation in a sedentary bird: house sparrow population genetics in a contiguous landscape

The house sparrow Passer domesticus has been declining in abundance in many localities, including Finland. We studied the genetic diversity and differentiation of the house sparrow populations across Finland in the 1980s, at the onset of the species'' decline in abundance. We genotyped 472 adult males (the less dispersive sex) from 13 locations in Finland (covering a range of 400 × 800 km) and one in Sweden (Stockholm) for 13 polymorphic microsatellite markers. Our analysis of Finnish ringing records showed that natal dispersal distances are limited (90% <16 km), which confirmed earlier finding from other countries. The Finnish populations were panmictic, and genetically very homogeneous and the limited dispersal was sufficiently large to maintain their connectivity. However, all Finnish populations differed significantly from the Stockholm population, even though direct geographical distance to it was often smaller than among Finnish populations. Hence, the open sea between Finland and Sweden appears to form a dispersal barrier for this species, whereas dispersal is much less constrained across the Finnish mainland (which lacks geographical barriers). Our findings provide a benchmark for conservation biologists and emphasize the influence of landscape structure on gene flow.     

Population genetics of the invasive water weed Elodea canadensis in Finnish waterways

Invasions of exotic species often involve a rapid evolutionary change in the introduced populations. Elodea canadensis is an invasive aquatic weed native to North America. Our aims were to reveal the evolutionary consequences of invasion to the population genetic structure of the presumably clonal E. canadensis in Finland and to test the hypothesis that the whole Finnish population originates from the first introduction of the species. We used ten polymorphic microsatellite markers to analyze the genetic characteristics of seven introduced E. canadensis populations in Finland. Despite the species' totally asexual mode of reproduction in Finland, two to five alleles per locus were detected in Finnish populations, and the expected heterozygosities varied between 0.19 and 0.37. The majority of variation was found within populations. Except for one, all pairwise values of population differentiation (F _ST) were significant, indicating restricted gene flow among the Finnish populations. In addition, a Bayesian analysis of population structure revealed the presence of regional population structuring. Genetic analyses indicate that E. canadensis could have been introduced to Finland multiple times. However, the amount of genetic variation and regional clustering detected could also be explained by post-establishment evolution, and based on this study it is not possible to exclude one introduction event followed by rapid evolution. We also tested the usability of the microsatellite markers for native North American samples in order to compare the within-population genetic characteristics of introduced and native populations. However, in native populations only four microsatellite markers amplified reliably, indicating sequence variation within primer-binding regions and, thus, genetic differentiation among populations of E. canadensis.     

Regional and local spatial genetic structure of Siberian primrose populations in Northern Europe

We have investigated the local and regional scale genetic structure of Siberian primrose (Primula nutans) populations in Northern Europe. The genetic diversity and structure of fifteen populations sampled from the Bothnian Bay in Finland, the Barents Sea in Norway and the White Sea in Russia were assessed using eleven microsatellite markers. We investigated the distribution of genetic variation within and between populations, and studied the local genetic structure using spatial autocorrelation analysis. We found very low genetic and allelic diversity in the Bothnian Bay and Barents Sea populations, and only slightly higher in the White Sea population. The level of genetic differentiation between the regions was very high, whereas differentiation between the populations within the regions was moderate. We found no spatial structuring of populations in any region suggesting efficient dispersal on a local scale. Clonal reproduction seemed to have no effect on genetic structure.     

Territory occupancy and breeding success of Peregrine Falcons Falco peregrinus at various stages of population recovery

Organochlorine pesticides disrupted reproduction and killed many raptorial birds, and contributed to population declines during the 1940s to 1970s. We sought to discern whether and to what extent territory occupancy and breeding success changed from the pesticide era to recent years in a resident population of Peregrine Falcons Falco peregrinus in southern Scotland using long‐term (1964–2015) field data and multi‐state, multi‐season occupancy models. Peregrine territories that were occupied with successful reproduction in one year were much more likely to be occupied and experience reproductive success in the following year, compared with those that were unoccupied or occupied by unsuccessful breeders in the previous year. Probability of territory occupancy differed between territories in the eastern and western parts of the study area, and varied over time. The probability of occupancy of territories that were unoccupied and those that were occupied with successful reproduction during the previous breeding season generally increased over time, whereas the probability of occupancy of territories that were occupied after failed reproduction decreased. The probability of reproductive success (conditional on occupancy) in territories that were occupied during the previous breeding season increased over time. Specifically, for territories that had been successful in the previous year, the probability of occupancy as well as reproductive success increased steadily over time; these probabilities were substantially higher in recent years than earlier, when the population was still exposed to direct or residual effects of organochlorine pesticides. These results are consistent with the hypothesis that progressive reduction, followed by a complete ban, in the use of organochlorine pesticides improved reproductive success of Peregrines in southern Scotland. Differences in the temporal pattern of probability of reproductive success between south‐eastern and south‐western Scotland suggest that the effect of organochlorine pesticides on Peregrine reproductive success and/or the recovery from pesticide effects varied geographically and was possibly affected by other factors such as persecution.     

Autosomal, mitochondrial, and Y chromosome DNA variation in Finland: evidence for a male-specific bottleneck

The high prevalence of rare genetic diseases in Finland has been attributed to a founder effect some 2,000 years ago. However, this hypothesis has not been supported from mtDNA sequence and autosomal microsatellite data which indicate high levels of gene diversity. Here we have identified genetic evidence for a population bottleneck by examining variable microsatellite loci on the nonrecombining portion of Y chromosomes from Finland and four populations from Europe and the Americas. Sequence data from segment I of the control region (HVS-1) of mtDNA (360 bases) and 20 autosomal dinucleotide repeat markers were also analyzed. Partitions of genetic variance within and between populations revealed significant levels of Y-chromosome differentiation between populations. Phylogenetic and diversity analyses revealed divergent Finnish Y-haplotype clades and significantly lower Y-haplotype diversity among Finns as compared to other populations. Surprisingly, Finnish Y-haplotype diversity was even lower than the Native American populations. These results provide support for the Finnish bottleneck hypothesis. Evidence for two separate founding Finnish Y-chromosome lineages was also observed from the Y-chromosome phylogeny. A limited number of closely related founding males may have contributed to the low number of paternal lineages in the Finnish population. In contrast, high levels of genetic diversity for mtDNA and autosomal STRs may be the result of sex-biased gene flow and recent immigration to urban areas from established internal isolates within Finland.     

Connectivity and gene flow among Eastern Tiger Salamander (Ambystoma tigrinum) populations in highly modified anthropogenic landscapes

Fragmented landscapes resulting from anthropogenic habitat modification can have significant impacts on dispersal, gene flow, and persistence of wildlife populations. Therefore, quantifying population connectivity across a mosaic of habitats in highly modified landscapes is critical for the development of conservation management plans for threatened populations. Endangered populations of the eastern tiger salamander (Ambystoma tigrinum) in New York and New Jersey are at the northern edge of the species’ range and remaining populations persist in highly developed landscapes in both states. We used landscape genetic approaches to examine regional genetic population structure and potential barriers to migration among remaining populations. Despite the post-glacial demographic processes that have shaped genetic diversity in tiger salamander populations at the northern extent of their range, we found that populations in each state belong to distinct genetic clusters, consistent with the large geographic distance that separates them. We detected overall low genetic diversity and high relatedness within populations, likely due to recent range expansion, isolation, and relatively small population sizes. Nonetheless, landscape connectivity analyses reveal habitat corridors among remaining breeding ponds. Furthermore, molecular estimates of population connectivity among ponds indicate that gene flow still occurs at regional scales. Further fragmentation of remaining habitat will potentially restrict dispersal among breeding ponds, cause the erosion of genetic diversity, and exacerbate already high levels of inbreeding. We recommend the continued management and maintenance of habitat corridors to ensure long-term viability of these endangered populations.     

Rapid recovery of genetic diversity of dogwhelk (Nucella lapillus L.) populations after local extinction and recolonization contradicts predictions from life-history characteristics

The dogwhelk Nucella lapillus is a predatory marine gastropod populating North Atlantic rocky shores. As with many other gastropod species, N. lapillus was affected by tributyltin (TBT) pollution during the 1970s and 1980s, when local populations became extinct. After a partial ban on TBT in the United Kingdom in 1987, vacant sites have been recolonized. N. lapillus lacks a planktonic larval stage and is therefore expected to have limited dispersal ability. Relatively fast recolonization of some sites, however, contradicts this assumption. We compared levels of genetic diversity and genetic structuring between recolonized sites and sites that showed continuous population at three localities across the British Isles. No significant genetic effects of extinction/recolonization events were observed in SW Scotland and NE England. In SW England we observed a decrease in genetic diversity and an increase in genetic structure in recolonized populations. This last result could be an artefact, however, due to the superposition of other local factors influencing the genetic structuring of dogwhelk populations. We conclude that recolonization of vacant sites was accomplished by a relatively high number of individuals originating from several source populations (the 'migrant-pool' model of recolonization), implying that movements are more widespread than expected on the basis of development mode alone. Comparison with published data on genetic structure of marine organisms with contrasted larval dispersal supports this hypothesis. Our results also stress the importance of local factors (geographical or ecological) in determining genetic structure of dogwhelk populations.     

Landscape discontinuities influence gene flow and genetic structure in a large, vagile Australian mammal, Macropus fuliginosus

Large vagile mammals typically exhibit little genetic structuring across their range, particularly when their habitat is essentially continuous. We investigated the population genetic structure of a large vagile Australian macropodid, Macropus fuliginosus, which is continuously distributed across most of southern Australia, using nine highly polymorphic nuclear microsatellite loci. Five distinct genetic units were identified across the range, four on the mainland and one on Kangaroo Island. In addition to the predicted historic Nullarbor Plain Barrier, two unexpected mainland barriers to gene flow were identified. Both were associated with landscape discontinuities (Swan River, Flinders Ranges), which appear within the dispersal capabilities of M. fuliginosus. Typical of large vagile mammals, M. fuliginosus displays high genetic diversity (with the exception of an insular population) and weak genetic structuring (within genetic units). However, the expansion of M. fuliginosus from southwestern Australia during the Pleistocene has resulted in significantly reduced genetic diversity in eastern populations. No significant sex-biased dispersal was detected, although differences in habitat, densities and climatic conditions between the eastern and western regions of the range appear to influence dispersal with the effects of isolation by distance only evident in the west. These results suggest that the biogeography of southern Australia is more complex than previously thought and reveal that seemingly minor landscape features can significantly impact genetic structuring in large vagile mammals.     

Homogenous Population Genetic Structure of the Non-Native Raccoon Dog (Nyctereutes procyonoides) in Europe as a Result of Rapid Population Expansion

The extent of gene flow during the range expansion of non-native species influences the amount of genetic diversity retained in expanding populations. Here, we analyse the population genetic structure of the raccoon dog (Nyctereutes procyonoides) in north-eastern and central Europe. This invasive species is of management concern because it is highly susceptible to fox rabies and an important secondary host of the virus. We hypothesized that the large number of introduced animals and the species’ dispersal capabilities led to high population connectivity and maintenance of genetic diversity throughout the invaded range. We genotyped 332 tissue samples from seven European countries using 16 microsatellite loci. Different algorithms identified three genetic clusters corresponding to Finland, Denmark and a large ‘central’ population that reached from introduction areas in western Russia to northern Germany. Cluster assignments provided evidence of long-distance dispersal. The results of an Approximate Bayesian Computation analysis supported a scenario of equal effective population sizes among different pre-defined populations in the large central cluster. Our results are in line with strong gene flow and secondary admixture between neighbouring demes leading to reduced genetic structuring, probably a result of its fairly rapid population expansion after introduction. The results presented here are remarkable in the sense that we identified a homogenous genetic cluster inhabiting an area stretching over more than 1500km. They are also relevant for disease management, as in the event of a significant rabies outbreak, there is a great risk of a rapid virus spread among raccoon dog populations.     

Trapping of Saker Falcon Falco cherrug and Peregrine Falcon Falco peregrinus in Saudi Arabia: Implications for biodiversity conservation

The numbers of Falco cherrug and Falco peregrinus trapped during their migration over the Kingdom of Saudi Arabia (KSA) were investigated from published reports and through interviews with well-known trappers and dealers over several years (1989–2013). The number of trapped individuals increased for both species over a 23 year period, which is probably related to an enhanced trapping effort. Time series analysis suggests that the number of Saker Falcons being trapped is likely to be stable with annual fluctuations in the coming ten-year period, whereas the number of trapped Peregrine Falcons will probably decline with a small fluctuation initially. Using the population viability analysis suggests a high extinction rate for the Saker Falcon population migrating through KSA during the coming 10 and 20 years; whereas Peregrine Falcons probably take more than 100 years to reach the extinction threshold. However, the increase in the trapping period, especially in the spring, that has been observed during the last five years could increase the number of falcons trapped in the future. As both falcon species are migratory, implementing conservation actions across all range states is important to ensure a favourable conservation status for the Saker and Peregrine Falcons. Both species will benefit through the implementation of the Global Action Plan (GAP), developed by the Saker Falcon Task Force.     

Population genetic structure of rock ptarmigan in the 'sky islands' of French Pyrenees: implications for conservation

Expected consequences of global warming include habitat reduction in many cool climate species. Rock ptarmigan is a Holarctic grouse that inhabits arctic and alpine tundra. In Europe, the Pyrenean ptarmigan inhabits the southern edge of the species' range and since the last glacial maximum its habitat has been severely fragmented and is restricted to high-alpine zones or 'sky islands'. A recent study of rock ptarmigan population genetic in Europe found that the Pyrenean ptarmigan had very low genetic diversity compared with that found in the Alps and Scandinavia. Habitat fragmentation and reduced genetic diversity raises concerns about the viability of ptarmigan populations in the Pyrenees. However, information on population structuring and gene flow across the Pyrenees, which is essential for designing a sound management plan, is absent. In this study, we use seven microsatellites and mitochondrial control region sequences to investigate genetic variation and differentiation among five localities across the Pyrenees. Our analyses reveal the presence of genetic differentiation among all five localities and a significant isolation-by-distance effect that is likely the result of short dispersal distances and high natal and breeding philopatry of Pyrenean ptarmigan coupled with severe habitat fragmentation. Furthermore, analysis of molecular variance, principal component analysis and Bayesian analysis of genetic structuring identified the greatest amount of differentiation between the eastern and main parts of the Pyrenean chain separated by the Sègre Valley. Our data also show that the Canigou massif may host an isolated population and requires special conservation attention. We propose a management plan which includes the translocation of birds. If a sky island structure affects genetic divergence in rock ptarmigan, it may also affect the genetic structure of other sky island species having low dispersal abilities.     

Factors affecting breeding success of Peregrine and Lanner Falcons in South Africa

Jenkins, A.R. 2000. Factors affecting breeding success of Peregrine and Lonner Falcons in South Africa. Ostrich 71 (384): 385-392. Breeding success was recorded for three Peregrine Falcon, Falco peregrinus, populations in South Africa over nine years, and for Peregrine and Lanner Falcon, Ebiarmicus, populations in an area of sympatry over three years. The objectives of the study were to measure geographic and interspecific variation in reproductive performance, and determine environmental correlates of productivity. Territory occupancy, the frequency of breeding per occupied territory and clutch size did not vary significantly between the three Peregrine populations. However, Peregrine breeding success was generally lower on the Cape Peninsula (1. 11 young fledged per territorial poir), higher in the Soutpansberg (1.36) and highest on the Orange River (1.70). Overall, fledging rates of Soutpansberg Peregrines and Lanners were not significantly different, although annual productivity of the Lonner population was consistently higher. Neither species' breeding success was significantly depressed by the presence of close neighbouring pairs of the other, suggesting that they were not active competitors. Breeding performance of Peregrines on the Cape Peninsula correlated strongly with spring weather conditions: egg and hatchling survival was lower in wet years, and fledging rates were higher in warm years. Annual productivity of Orange River Peregrines correlated positively with the height of the river at the onset of breeding, and productivity of Soutpansberg Peregrines was higher in seasons following years of high rainfall. Elements of the physical structure of the nesting habitat (exposure of the nest ledge, height of the nest cliff) correlated positively with Peregrine breeding performance. Breeding success of Soutpansberg Lanners was largely unaffected by any of the environmental variables considered. Overall, it is proposed that Peregrine productivity reflected variation in the physical environment and its affect on prey availability.     

Gene flow connects coastal populations of a habitat specialist,the Clapper Rail Rallus crepitans

Examining population genetic structure can reveal patterns of reproductive isolation or population mixing and inform conservation management. Some avian species are predicted to exhibit minimal genetic differentiation among populations as a result of the species high mobility, with habitat specialists tending to show greater fine‐scale genetic structure. To explore the relationship between habitat specialization and gene flow, we investigated the genetic structure of a saltmarsh specialist with high potential mobility across a wide geographical range of fragmented habitat. Little variation among mitochondrial sequences (620 bp from ND2) was observed among 149 individual Clapper Rails Rallus crepitans sampled along the Atlantic coast of the USA, with the majority of individuals at all sampling sites sharing a single haplotype. Genotyping of nine microsatellite loci across 136 individuals revealed moderate genetic diversity, no evidence of bottlenecks and a weak pattern of genetic differentiation that increased with geographical distance. Multivariate analyses, Bayesian clustering and an AMOVA all suggested a lack of genetic structuring across the Atlantic coast of the USA, with all individuals grouped into a single interbreeding population. Spatial autocorrelation analyses showed evidence of weak female philopatry and a lack of male philopatry. We conclude that high gene flow connecting populations of this habitat specialist may result from the interaction of ecological and behavioural factors that promote dispersal and limit natal philopatry and breeding‐site fidelity. As climate change threatens saltmarshes, the genetic diversity and population connectivity of Clapper Rails may promote resilience of their populations. This finding helps inform about potential fates of other similarly behaving saltmarsh specialists on the Atlantic coast.     

Mitochondrial genetic variation and population structure of the striped snakehead,Channa striata in Malaysia and Sumatra,Indonesia

We explored the genetic diversity and structure of the striped snakehead (Channa striata) across Malaysia and Sumatra (Indonesia) using the partial mtDNA CO1 gene. Twenty five populations (n = 345) were assayed and subdivided into six regions, following the physiogeographical barriers. Populations Sega (SG), Tanjung Tambutan (TR), Kajang (KJ) and Linggi (LG) are highly diversified (Hd: 0.484–0.762, π: 0.0033–0.0059) which could serve as candidates for a selective breeding programme. The only population that contributed to the total allelic richness is Takengon (CS) as it is highly differentiated from other populations and genetically variable within population. We detected two major phylogenies: 1) northwest Peninsular Malaysia and 2) all other regions of Malaysia and Sumatra, Indonesia. They are products of the physical restriction to gene flow between the two lineages by the Bintang Mountain Range. A total of 92.4% of the population pairwise comparison F_ST showed significant structuring, yet several geographically distant populations showed a close genetic relationship. The discrepancy is due to ancient population dispersal and human-mediated translocation. These major findings provide an important base study for initiating a selective breeding program. The high population genetic diversity requires independent conservation as they contain most of the total diversity in this area.     

Population genetic patterns in an irruptive species,the long-nosed bandicoot (<Emphasis Type="Italic">Perameles nasuta</Emphasis>)

Understanding the genetic diversity of a population is important for understanding population persistence and extinction risk. The long-nosed bandicoot (Perameles nasuta) was once regarded as common throughout its range, but it is unknown whether it is at risk of decline and the genetic diversity in this species has not been assessed. We evaluated the genetic structure and diversity of a P. nasuta population from samples collected during a 6 year demographic study that encompassed a cyclical fluctuation in abundance. Genetic diversity was higher compared to other studies on bandicoot species suggesting the population is not genetically impoverished. We detected significant temporal genetic differentiation suggesting turnover of genotypes. There was no strong evidence for population structuring, indicating a panmictic population. Individual-based spatial autocorrelation analysis generated a similar pattern of relatedness across geographical distances for both sexes suggesting no or limited sex-biased dispersal. This study provides useful baseline genetic data for a large P. nasuta population that is not significantly impacted by introduced predators or habitat destruction.     

Challenges to assessing connectivity between massive populations of the Australian plague locust

Linking demographic and genetic dispersal measures is of fundamental importance for movement ecology and evolution. However, such integration can be difficult, particularly for highly fecund species that are often the target of management decisions guided by an understanding of population movement. Here, we present an example of how the influence of large population sizes can preclude genetic approaches from assessing demographic population structuring, even at a continental scale. The Australian plague locust, Chortoicetes terminifera, is a significant pest, with populations on the eastern and western sides of Australia having been monitored and managed independently to date. We used microsatellites to assess genetic variation in 12 C. terminifera population samples separated by up to 3000 km. Traditional summary statistics indicated high levels of genetic diversity and a surprising lack of population structure across the entire range. An approximate Bayesian computation treatment indicated that levels of genetic diversity in C. terminifera corresponded to effective population sizes conservatively composed of tens of thousands to several million individuals. We used these estimates and computer simulations to estimate the minimum rate of dispersal, m, that could account for the observed range-wide genetic homogeneity. The rate of dispersal between both sides of the Australian continent could be several orders of magnitude lower than that typically considered as required for the demographic connectivity of populations.     

Significant genetic admixture after reintroduction of peregrine falcon (<Emphasis Type="Italic">Falco peregrinus</Emphasis>) in Southern Scandinavia

The peregrine falcon (Falco peregrinus) population in southern Scandinavia was almost extinct in the 1970’s. A successful reintroduction project was launched in 1974, using captive breeding birds of northern and southern Scandinavian, Finnish and Scottish origin. We examined the genetic structure in the pre-bottleneck population using eleven microsatellite markers and compared the data with the previously genotyped captive breeding population and contemporary wild population. Museum specimens between 53 and 130 years old were analyzed. Despite an apparent loss of historical genetic diversity, the contemporary population shows a relatively high level of genetic variation. Considerable gene introgression from captive breeding stock used to repopulate the former range of southern Scandinavian peregrines may have altered the genetic composition of this population. Both the historical and contemporary northern and southern Scandinavian populations are genetically differentiated. The reintroduction project implemented in the region and the use of non-native genetic stock likely prevented the southern Scandinavian population from extinction and thus helped maintain the level of genetic diversity and prevent inbreeding depression. The population is rapidly increasing in numbers and range and shows no indication of reduced fitness or adaptive capabilities in the wake of the severe bottleneck and the reintroduction.