Western Subpopulation Research Articles

Genetic structure and diversity of the capercaillie (Tetrao urogallus) population in Belarus in the context of de-lineation of two subspecies: major and pleskei

In the present article, an analysis of the genetic diversity and differentiation of the Belarusian capercaillie sub-populations from the range of two subspecies—Tetrao urogallus major and Tetrao urogallus pleskei—distinguished on the basis of morphological and behavioural (mating vocalization) criteria was carried out. The microsatellites were chosen as genetic markers. A total of 53 specimens were used for genetic analysis (23 specimens from the range of T. u. major and 30 specimens from the range of T. u. pleskei). In this study, we aimed at resolving the following questions: (1) Does the capercaillie subpopulation from the range of T. u. ma-jor in Belarus exhibit genetic isolation from the rest of the population in the country? (2) Should we consider the western subpopulation of the capercaillie in Belarus a management unit? Our data allows concluding that the genetic diversity of the studied capercaillie subpopulations is sufficiently high. The eastern subpopulation of the capercaillie is characterised by slightly higher values of all estimates of genetic diversity. A total of 35 unique alleles were detected in the studied capercaillie population. Of them, 10 alleles (29%) were discovered among the specimens sampled from the western subpopulation of the capercaillie. Genetic analysis for the presence of bottleneck events did not reveal any evidence of those in the demographic history of the studied Belarusian capercaillie subpopulations. Bayesian analysis of genetic structure has indicated the presence of two clusters, corresponding to the eastern and western capercaillie subpopulations in Belarus. The obtained ge-netic structure of the capercaillie population is also supported by the results of the factorial correspondence analysis. The results of genetic structure and diversity analysis indicate that the capercaillie population in Bela-rus possesses a degree of genetic differentiation on subpopulation level and a lack of clear isolation between the studied subpopulations. As recommendations for the conservation of the western subpopulation of the capercaillie in Belarus we propose to conduct genetic monitoring of the newly created population, as well as genetic analysis of the specimens used for breeding.

Monarchs Reared in Winter in California Are Not Large Enough to Be Migrants. Comment on James et al. First Population Study on Winter Breeding Monarch Butterflies, Danaus plexippus (Lepidoptera: Nymphalidae) in the Urban South Bay of San Francisco, California. Insects 2021, 12, 946.

A recent study in this journal aimed to understand certain changes in the wintering behavior of monarch butterflies, specifically in the western subpopulation of North America [...].

And yet, migration, population growth or mortality are not balanced among Cantabrian brown bear subpopulations. Reply to Blanco et al (2020).

In a recent paper, we presented new evidence and provided new insights on the status of Cantabrian brown bear subpopulations, relevant for this species conservation. Namely, we revealed the likely phylogeographic relation between eastern Cantabrian subpopulation and the historical Pyrenean population. We have also detected an asymmetric flow of alleles and individuals from the eastern to the western subpopulation, including seven first-generation male migrants. Based on our results and on those of previous studies, we called the attention to the fact that Eastern Cantabrian brown bears might be taking advantage of increased connectivity to avoid higher human pressure and direct persecution in the areas occupied by the eastern Cantabrian subpopulation. In reply, Blanco et al (2020) [11] have criticized our ecological interpretation of the data presented in our paper. Namely, Blanco and co-authors criticize: (1) the use of the exodus concept in the title and discussion of the paper; (2) the apparent contradiction with source-sink theory; (3) the apparent overlooking of historical demographic data on Cantabrian brown bear and the use of the expression of population decline when referring to eastern subpopulation. Rather than contradicting the long and growing body of knowledge on the two brown bear subpopulations, the results presented in our paper allow a new perspective on the causes of the distinct pace of population growth of the two brown bear subpopulations in the last decades. Here, we reply to the criticisms by: clarifying our ecological interpretation of the results; refocusing the discussion on how the new genetic data suggest that currently, the flow of individuals and alleles is stronger westward, and how it may be linked to direct persecution and killing of brown bears. We provide detailed data on brown bear mortality in the Cantabrian Mountains and show that neither migration, gene flow, population increase nor mortality are balanced among the two subpopulations.

Evidence of Recombination Suppression Blocks on the Y Chromosome of Date Palm (Phoenix dactylifera).

The genus Phoenix includes the fruit producing date palm tree among 14 species that are all dioecious. Females produce the fruit that are high in sugar content and used in multiple countries ranging from North Africa to South Asia, especially from the Phoenix dactylifera, Phoenix sylvestris, and Phoenix canariensis species. While females produce the fruit, understanding of the genetic basis of sex control only began recently. Through genus-wide sequencing of males and females we recently identified three genes that are conserved in all males and absent in all females of the genus and confirmed an XY sex chromosome system. While our previous study focused on conservation of male-specific sequences at the genus-level, it would be of interest to better understand the spread of male-specific sequences away from the core conserved male genes on the Y chromosome during speciation. To this end, we enumerated male-specific 16 bp sequences using three male/female pairs from the western subpopulation of date palm and documented the density of these sequences in contigs of a phased date palm genome assembly. Here we show that male specific sequences in the date palm Y chromosome have likely spread in defined events that appear as blocks of varying density with significant changes in density between them. Collinearity of genes in these blocks with oil palm shows high synteny with chromosome 10 between megabase 15 and 23 and reveals that large sections of the date palm Y chromosome have maintained the ancestral structure even as recombination has stopped between X and Y.

Does genetic variation on the shy–bold continuum influence carnivore attacks on people? Evidence from the brown bear

AbstractLittle is known about the heritable behavioural traits of attacks by large carnivores on people. During the last 30 years attacks by brown bears Ursus arctos on people in the Cantabrian Mountains of Spain have been disproportionately concentrated in the eastern subpopulation. Excluding factors such as the existence of a single unusually bold bear, a higher human population density, particular human activities promoting encounters, or clear habitat differences in the area of this subpopulation, we propose that a plausible explanation for the unbalanced geographical attack pattern is that this subpopulation, separated a century earlier from the western subpopulation, may harbour a higher proportion of bolder bears. In the absence of genetic analyses this explanation remains speculative, but supports the hypothesis that genetic variation on the shy–bold continuum may influence attacks of large carnivores on people.

Losing seasonal patterns in a hibernating omnivore? Diet quality proxies and faecal cortisol metabolites in brown bears in areas with and without artificial feeding.

Bears are omnivores particularly well-adapted to variations in the nutritional composition, quality and availability of food resources. Artificial feeding practices have been shown to strongly influence diet composition and seasonality, as well as to cause alterations in wintering and movement in brown bears (Ursus arctos). In this study, we investigated seasonal differences (hypophagia vs hyperphagia) in food quality of two brown bear subpopulations in the Polish Carpathians using faecal nitrogen (FN) and carbon (FC) estimates. The subpopulations inhabit areas that differ in artificial feeding practices: no artificial feeding occurs in the western subpopulation (Tatra Mountains), while artificial food targeted to ungulates is provided and used year-round in the eastern subpopulation (Bieszczady Mountains). We also compared these results with faecal cortisol metabolites (FCM) to explore how FN and FC correlate with the hypothalamic-pituitary-adrenal axis activity and if the seasonal patterns are apparent. We found that in Tatra Mts bears fed on significantly higher quality diet, as shown by FN and FC values, and had significantly higher FC levels in hyperphagia, when they accumulate fat reserves for wintering. The pattern in FCM levels for Tatra subpopulation followed the changes in energy intake during the seasons of hypo- and hyperphagia, while in Bieszczady Mts, the area with intensive feeding, no seasonal patterns could be observed. Artificial feeding practices may disrupt nutrient phenology and seasonality, relative to subpopulations with natural diets. We showed that the availability of human-provided foods may alter not only the overall dietary quality, but also hormonal patterns linked to seasonal nutritional requirements. Combining FN, FC and FCM proved to be a useful tool for reconstructing diet quality and related physiological patterns.

Trophic basis of dominant amphipods in the gray whale feeding grounds near northeastern Sakhalin Island (the Sea of Okhotsk) inferred from fatty acid and stable isotope analyses

The shelf waters off northeastern Sakhalin Island are the main feeding ground for the endangered western subpopulation of the gray whale Eschrichtius robustus. Amphipods, which dominate the benthic communities, are key dietary sources for the gray whales foraging in this area. To elucidate the trophic base supporting the large local amphipod biomass, fatty acid (FA) compositions and the stable isotope ratios δ13C and δ15N of the five most abundant amphipod species in the area were studied. The FA compositions were unusually similar (85% similarity) across the amphipod species although these species were represented by suspension-feeders, deposit-feeders and carnivores. The FAs of diatom origin predominated in the FA profiles of all amphipods and decreased in accordance with the increase in trophic position as determined by δ15N values and the FA trophic markers of carnivorous feeding. These results suggested that diatoms are the single, main trophic basis that underpins the food web of the feeding grounds on the northeastern Sakhalin shelf. Further studies on factors influencing the local production of large diatoms on the Sakhalin shelf can be important for the prognosis of future changes of foraging resources of the gray whales.

Assessing δ13C, δ15N and Total Mercury Measures in Epidermal Biopsies From Gray Whales

The gray whale (Eschrichtius robustus) is recognized as two geographically isolated and somewhat genetically distinct populations, with recent evidence showing exchange that questions the degree of isolation. The western gray whale subpopulation is currently listed as critically endangered, as designated by the IUCN, whereas the eastern North Pacific population is listed by the IUCN as “Least Concern”. The International Whaling Commission has stressed the value of studies on feeding ecology and contaminants for the western subpopulation. Our objective was to test for differences among epidermal tissue strata as part of an optimization effort to best use and interpret data from small biopsy samples. Fresh to moderately decomposed full thickness samples of epidermis and dermis were collected from stranded eastern gray whales along the California coast, USA (N: 14), and biopsy samples (N: 10) were collected from free-ranging western gray whales. We determined 13C and 15N stable isotope ratios (δ13C, δ15N); and total Hg concentrations ([THg]) from histologically different strata of epidermal tissue samples from the eastern gray whale population The information from these assessments (stranded whale samples) were directly applied for determining δ13C and δ15N from biopsies collected remotely from free-ranging western gray whales, as well as evaluating [THg]. We found a significant difference in [THg] values between the different strata. This has implications for analyzing Hg, and possibly other elements, from an epidermal biopsy from a free-ranging gray whale, and we recommend identifying which stratum/strata the biopsy represents. There were no significant differences in δ13C and δ15N values between the different strata, making epidermal biopsies from free-ranging gray whales an ideal sampling method to investigate δ13C and δ15N ratios regardless of strata representation.

Genetic analysis of African lions (Panthera leo) in Zambia support movement across anthropogenic and geographical barriers

The Luangwa Valley in eastern Zambia is a transverse offshoot of the Great Rift Valley system. This region appears to have an isolating effect as evidenced by suspected endemic subspecies, such as the Cookson’s wildebeest and Thornicroft’s giraffe. Recent mitochondrial DNA studies demonstrated that African lions in Zambia consist of two highly diverse eastern and western sub-populations. Herein, we report nuclear and mitochondrial DNA results from 409 lions that support this population substructure across Zambia but proposes only partial isolation of the Luangwa Valley with more movement between the populations than previously thought. Population assignment analysis identifies two populations with little evidence of admixture assigning lions to either the eastern or western sub-populations. A high occurrence of private alleles and clear evidence for a Wahlund effect further justify the presence of a highly structured population. But, while mitochondrial DNA analysis still shows little to no matrilineal gene flow (FST = 0.53) between sub-populations, microsatellite analysis suggests there is gene flow (FST = 0.04) with low but significant isolation-by-distance and an average of 6 migrants per generation. Evidence of isolation-by-distance is also found in factorial correspondence analysis with the Lower Zambezi National Park and eastern corridor clusters overlapping isolated clusters of the Luangwa Valley and western sub-population. From this evidence, the Luangwa Valley appears separated from the western sub-population with some dispersal through the southern regions of the eastern sub-population. Both the eastern and western sub-populations have high heterozygosity (0.68 and 0.69, respectively) and genetic diversity (0.47 and 0.50, respectively) values, indicative of genetically healthy populations.

Genetic and demographic recovery of an isolated population of brown bear Ursus arctos L., 1758.

The brown bear Ursus arctos L., 1758 population of the Cantabrian Mountains (northwestern Spain) became isolated from other bear populations in Europe about 500 years ago and has declined due to hunting and habitat degradation. At the beginning of the 20th century, the Cantabrian population split into eastern and western subpopulations, and genetic exchange between them ceased. In the early 1990s, total population size was estimated to be < 100 bears. Subsequently, reduction in human-caused mortality has brought about an increase in numbers, mainly in the western subpopulation, likely promoting male-mediated migration and gene flow from the western nucleus to the eastern. To evaluate the possible genetic recovery of the small and genetically depauperate eastern subpopulation, in 2013 and 2014 we genotyped hair and faeces samples (116 from the eastern subpopulation and 36 from the western) for 18 microsatellite markers. Data from the annual count of females with cubs of the year (COY) during the past twenty-six years was used to analyze demographic changes. The number of females with COY fell to a minimum of seven in the western and three in eastern subpopulations in the biennium 1993–1994 and reached a respective maximum of 54 and 10 individuals in 2013–2014. We also observed increased bear dispersal and gene flow, mainly from the western to the eastern subpopulation. Of the 26 unique genotypes detected in the eastern subpopulation, 14 (54%) presented an admixture composition, and seven (27%) were determined to be migrants from the western subpopulation. Hence, the two separated and clearly structured subpopulations identified in the past currently show some degree of genetic admixture. This research shows the partial demographic recovery and a change in genetic composition due to migration process in a population of bears that has been isolated for several centuries.

Y chromosome haplotype distribution of brown bears (Ursus arctos) in Northern Europe provides insight into population history and recovery

High-resolution, male-inherited Y-chromosomal markers are a useful tool for population genetic analyses of wildlife species, but to date have only been applied in this context to relatively few species besides humans. Using nine Y-chromosomal STRs and three Y-chromosomal single nucleotide polymorphism markers (Y-SNPs), we studied whether male gene flow was important for the recent recovery of the brown bear (Ursus arctos) in Northern Europe, where the species declined dramatically in numbers and geographical distribution during the last centuries but is expanding now. We found 36 haplotypes in 443 male extant brown bears from Sweden, Norway, Finland and northwestern Russia. In 14 individuals from southern Norway from 1780 to 1920, we found two Y chromosome haplotypes present in the extant population as well as four Y chromosome haplotypes not present among the modern samples. Our results suggested major differences in genetic connectivity, diversity and structure between the eastern and the western populations in Northern Europe. In the west, our results indicated that the recovered population originated from only four male lineages, displaying pronounced spatial structuring suggestive of large-scale population size increase under limited male gene flow within the western subpopulation. In the east, we found a contrasting pattern, with high haplotype diversity and admixture. This first population genetic analysis of male brown bears shows conclusively that male gene flow was not the main force of population recovery.

Inferences of demographic history and fine-scale landscape genetics in Cycas panzhihuaensis and implications for its conservation

Understanding the population genetic structure and demographic history helps in the management and restoration of endangered species. Cycas panzhihuaensis (Panzihihua sago palm) is narrowly distributed in the eastern Sichuan Basin of China. The only extant population is in the Panzhihua Cycad Nature Reserve (PCNR), which is close to Panzhihua City, and is threatened by the mining industry and slash-and-burn agriculture. To protect this rare species, the local government implemented an ex situ conservation project. In this study, amplified fragment length polymorphism (AFLP) was used to explore the genetic diversity of wild and cultivated populations. Two evolutionarily significant units (ESUs) in PCNR were determined based on significant differences in genetic diversity and demographic histories. The western ESU has low genetic diversity and shares common genotypes with a part of the eastern ESU. The founder effect is suggested as the best-fit scenario to explain the current genetic distribution among the eastern and western ESUs. Small carrying capacity limits both census and effective population sizes, and the gene surfing hypothesis explains the high frequency of fixed alleles without private alleles in multiple loci in the western subpopulation. Every cultivated population, established for either conservation or horticultural purposes, has only genotypes from a single ESU. Supplementary collection for ex situ conservation is suggested to preserve the genetic features of C. panzhihuaensis.

Estimating the population size of the endangered Cantabrian brown bear through genetic sampling

The Cantabrian brown bearUrsus arctospopulation can be seen as a paradigm in conservation biology due to its endangerment status and genetic uniqueness. Therefore, the need to obtain basic demographic data to inform management actions for conservation is imperative. Despite this, empirical data on the size and trends of the Cantabrian bear population are scarce. Here we present the first estimates of population size (Nc) and effective population size (Ne) of the whole Cantabrian brown bear population. We genotyped 270 non‐invasive samples collected during 2006 throughout the entire range of the population and subsequently identified 130 individuals. Different model estimators of Ncbased on capture—markrecapture (CMR) procedures were compared. The average for the best three models (Mh Chao, Mh Darroch and CAPWIRE TIRM) yielded a total estimate of Nc= 223 individuals (CI95%= 183–278) and Ne50 (CI95%= 36–75) providing an Ne/ Ncratio of 0.22. Estimates for the two subpopulations commonly recognized in the Cantabrian range were Nc= 203 (CI95%= 168–260) and Ne= 47 (CI95%= 36–70) for the western subpopulation and Nc= 19 (CI95%= 12–40) and Ne= 9 (CI95%= 8–12) for the eastern subpopulation. These data suggest that the Cantabrian brown bear population has increased recently, mainly in the western subpopulation, after a long period of decline and isolation which lead to the split of the population at the beginning of the 20th century. Population sizes in the early 1990s were thought to be only 60 individuals for the western subpopulation and 14 individuals in the eastern one. The efforts to improve conservation policies made since then have probably contributed, to some extent, to the population increase during the last couple of decades.

Genetic differentiation of brackish water populations of cod Gadus morhua in the southern Baltic, inferred from genotyping using SNP-arrays

The Baltic is a semi-enclosed sea characterised by decreasing salinity in the eastern and northern direction with only the deeper parts of the southern Baltic suitable as spawning grounds for marine species like cod. Baltic cod exhibits various adaptations to brackish water conditions, yet the inflow of salty North Sea water near the bottom remains an influence on the spawning success of the Baltic cod. The eastern Baltic population has been very weakly studied in comparison with the western population.The aim of this study is to demonstrate for the first time genetic differentiation by the use of a large number of SNPs between eastern and western Baltic populations existing in differentiated salinity conditions. Two cod samples were collected from the Bay of Gdańsk, Poland and one from the Kiel Bight, Germany. Samples were genotyped using a cod derived SNP-array (Illumina) with 10 913 SNPs. A selection of diagnostic SNPs was performed. A set of 7944 validated SNPs were analysed to assess the differentiation of three samples of cod. Results indicated a clear distinctness of the Kiel Bight from the populations of the eastern Baltic. FST comparison between both eastern samples was non-significant. Clustering analysis, principal coordinates analysis and assignment test clearly indicated that the eastern samples should be considered as one subpopulation, well differentiated from the western subpopulation. With the SNP approach, no differentiation between groups containing ‘healthy’ and ‘non-healthy’ cod individuals was observed.

Seasonal movements of wisents (Bison bonasus L., 1758) in the Bieszczady Mountains (SE Poland)

Abstract We studied seasonal movements of wisents (also known as European bison) from the western subpopulation in the Bieszczady Mountains, in forest districts of Baligród, Komańcza, Lesko, and Cisna. The estimation of distance of seasonal movements was based on telemetric bearings of 4 adult animals (1 cow and 3 bulls) in 2002‑2005. We assumed that a maximum distance of movement was a linear extent between 2 most distant locations of an animal recorded in winter and in the following growing season. The maximum distances were 12.8‑18.5 km for the cow, and 5.1‑22.9 km for bulls. Wisent movements were triggered by significant changes in ambient temperature (decrease in late autumn and increase in early spring) and the appearance of first snowfall in autumn.

Geographic distribution of the mid‐continent population of sandhill cranes and related management applications

AbstractThe Mid‐continent Population (MCP) of sandhill cranes (Grus canadensis) is widely hunted in North America and is separated into the Gulf Coast Subpopulation and Western Subpopulation for management purposes. Effective harvest management of the MCP requires detailed knowledge of breeding distribution of subspecies and subpopulations, chronology of their use of fall staging areas and wintering grounds, and exposure to and harvest from hunting. To address these information needs, we tagged 153 sandhill cranes with Platform Transmitting Terminals (PTTs) during 22 February–12 April 1998–2003 in the Central and North Platte River valleys of south‐central Nebraska. We monitored PTT‐tagged sandhill cranes, hereafter tagged cranes, from their arrival to departure from breeding grounds, during their fall migration, and throughout winter using the Argos satellite tracking system. The tracking effort yielded 74,041 useable locations over 49,350 tag days; median duration of tracking of individual cranes was 352 days and 73 cranes were tracked &gt;12 months. Genetic sequencing of mitochondrial DNA (mtDNA) from blood samples taken from each of our random sample of tagged cranes indicated 64% wereG. c. canadensisand 34% wereGrus canadensis tabida. Tagged cranes during the breeding season settled in northern temperate, subarctic, and arctic North America (U.S. [23%,n = 35], Canada [57%,n = 87]) and arctic regions of northeast Asia (Russia [20%,n = 31]). Distribution of tagged cranes by breeding affiliation was as follows: Western Alaska–Siberia (WA–S, 42 ± 4% [SE]), northern Canada–Nunavut (NC–N, 21 ± 4%), west‐central Canada–Alaska (WC–A, 23 ± 4%) and East‐central Canada–Minnesota (EC–M, 14 ± 3%). All tagged cranes returned to the same breeding affiliation used during the previous year with a median distance of 1.60 km (range: 0.08–7.7 km,n = 53) separating sites used in year 1 and year 2. Fall staging occurred primarily in central and western Saskatchewan (69%), North Dakota (16%), southwestern Manitoba (10%), and northwestern Minnesota (3%). Space‐use sharing indices showed that except for NC–N and WC–A birds, probability of finding a crane from one breeding affiliation within the home range of another breeding affiliation was low during fall staging. Tagged cranes from WC–A and EC–M breeding affiliations, on average, spent 25 and 20 days, respectively, longer on fall staging areas in the northern plains than did WA–S and NC–N birds. Cranes in the NC–N, WA–S, and WC–A affiliations spent 99%, 74%, and 64%, respectively, of winter in western Texas in Hunting Zone A; EC–M cranes spent 83% of winter along the Texas Gulf Coast in Hunting Zone C. Tagged cranes that settled within the breeding range of the Gulf Coast Subpopulation spent 28% and 42% of fall staging and winter within the range of the Western Subpopulation, indicating sufficient exchange of birds to potentially limit effectiveness of MCP harvest management. Harvests of EC–M and WC–A cranes during 1998–2003 were disproportionately high to their estimated numbers in the MCP, suggesting more conservative harvest strategies may be required for these subpopulations in the future, and for sandhill cranes to occupy major parts of their historical breeding range in the Prairie Pothole Region. Exceptionally high philopatry of MCP cranes of all 4 subpopulations to breeding sites coupled with strong linkages between crane breeding distribution, and fall staging areas and wintering grounds, provide managers guidance for targeting MCP crane harvest to meet management goals. Sufficient temporal or spatial separation exists among the 4 subpopulations on fall staging areas and wintering grounds to allow harvest to be targeted at the subpopulation level in all states and provinces (and most hunting zones within states and provinces) when conditions warrant. Knowledge gained from our study provides decision‐makers in the United States, Canada, Mexico, and Russia with improved guidance for developing sound harvest regulations, focusing conservation efforts, and generating collaborative efforts among these nations on sandhill crane research and management to meet mutually important goals. © 2011 The Wildlife Society.

Evidence for improved connectivity between Cantabrian brown bear subpopulations

Abstract The brown bear (Ursus arctos) population in the Cantabrian Mountains of northwest Spain is among the most endangered bear populations worldwide. It is divided into 2 isolated and genetically differentiated subpopulations. We present evidence of recent male migration between the subpopulations based on genetic identification of hair and scats samples gathered between 2004 and 2007. Of 76 identified individuals, our analysis assigned 3 males sampled in the eastern subpopulation to the western subpopulation. As well, 1 male genetically belonging to the eastern subpopulation was repeatedly sampled along his way to the western subpopulation during April to November 2006 (a linear distance of 144 km). This bear's path may help identify natural corridors, which could be improved through restoration management. In addition, we identified 2 genetically admixed individuals during 2008 in the Western limit of the eastern subpopulation range. Connectivity between subpopulations and gene flow appears to be im...

A population viability analysis for the Island Fox on Santa Catalina Island, California

The island fox ( Urocyon littoralis) on Santa Catalina Island is among the most imperiled species on the Channel Islands due to a recent outbreak of canine distemper virus (CDV). The western subpopulation, which was not exposed to CDV, is a crucial element in the recovery of foxes by providing a source of animals for translocation and captive breeding. Using the program VORTEX, we developed a population viability analysis for the Santa Catalina Island fox to (1) address the likelihood of population persistence, (2) estimate the current susceptibility of the population to catastrophic events, and (3) evaluate the efficacy of current restoration strategies of releasing captive bred foxes and transplanting wild animals. Overall, we found the population to be susceptible to catastrophic events; a 50% increase in mortality every 20 years was sufficient to elevate the extinction risk above 5%. Current management activities entail the transplanting of 12 juvenile foxes annually, which may reduce the viability of the western subpopulation. A minimum population size of at least 150 foxes should be maintained in each subpopulation to reduce the risk of extinction due to demographic stochasticity. Releases of translocated and captive bred animals affect the speed of recovery on the eastern half of Catalina Island, but not the probability of extinction, which is near zero under current conditions. We conducted a sensitivity analysis for demographic parameters by incrementally varying survival, fecundity and density-dependence parameters, while holding all other parameters constant. Sensitivity analyses identified mortality and mean litter size as the most sensitive parameters, while the implementation of density-dependence and environmental variation of model parameters did not seem to affect population performance. We conclude that the population of island foxes on Santa Catalina is currently at a critically low population level, but recovery of the species appears possible.

Geographically distant isolates of the crinivirus Cucurbit yellow stunting disorder virus show very low genetic diversity in the coat protein gene.

The population structure and genetic variation of Cucurbit yellow stunting disorder virus (CYSDV) isolates were estimated by single-strand conformation polymorphism and nucleotide sequence analyses of the CYSDV coat protein gene. Analysis of 71 isolates collected from Spain, Jordan, Turkey, Lebanon, Saudi Arabia and North America showed that, from a genetic viewpoint, these isolates could be divided into two diverged subpopulations: an Eastern subpopulation composed of Saudi Arabian isolates and a Western subpopulation containing the rest of the CYSDV isolates. The genetic variation within the Western subpopulation was very small (nucleotide identity >99%) in spite of the extensive and discontinuous geographical distribution and different years of collection. We also estimated the within-isolate genetic structure and variation of three CYSDV isolates by analysing 30 clones per isolate. Our results showed that these CYSDV isolates had a quasispecies structure.

Population dynamics of the endangered Cape Sable seaside‐sparrow

AbstractThe Cape Sable seaside‐sparrow (Ammodramus maritimus mirabilis) has disappeared from its only known breeding areas episodically since its discovery early this century. Systematic surveys across its range in the southern Everglades find the sparrow's range to be fragmented into six subpopulations. The sparrow population decreased by 58% between 1992 and 1995, with the near extinction of the western half of the population and the temporary local extinction of some eastern populations. Other similar grassland sparrows have populations that vary considerably from year to year. Yet the decline in the western subpopulation and the local extinction of some of the peripheral populations cannot be explained by natural variability alone. Hurricane Andrew passed over several subpopulations prior to the particularly poor year of 1993. However, the geographical and temporal patterns of subpopulation decline are not consistent with what would be expected following a hurricane. Frequent fires prevent successful breeding as does flooding during the breeding season. Better management can prevent frequent fires and episodic flooding. However, the long‐term survival of the sparrow depends on managing the unanticipated risks that attend its small, fragmented population.