Status,number, and monitoring of the common eider (<Emphasis Type="Italic">Somateria mollissima</Emphasis>) population in the barents sea and the White Sea

The breeding, molting, and wintering ranges of the common eider (Somateria mollissima) were mapped and described in the southern part of the Barents Sea region, including the White Sea population in the western White Sea and the Murmansk population in the northwestern White Sea and the southeastern Barents Sea. The present-day abundance was determined for both populations: since the 1950s, it was the highest in the 2000s for the entire period of ornithological monitoring in the region. Aerial survey from a helicopter is considered to be the only reliable method for estimation of the total population number. The best season for surveying the White Sea population is March–early April (wintering); the most favorable period for surveying the Murmansk population is August (postbreeding/molting). The population status of the common eider in the northern and eastern parts of the Barents Sea has not yet been evaluated. On Franz-Josef Land, the common eider is distributed sporadically, and its number was assessed using expert estimates. The current abundance of the common eider on Novaya Zemlya is unknown. Helicopter-based aerial survey performed in late summer during the postbreeding season is the only relevant method to obtain reliable estimates for the population of the common eider inhabiting Franz-Josef Land and Novaya Zemlya.     

Climate change and the population collapse during the “Great Famine” in pre‐industrial Europe

Population dynamics, economy, and human demography started with Malthus, the idea that population growth is limited by resources and “positive checks” occur when population growth overshoots the available resources. In fact, historical evidence indicates that long‐term climate changes have destabilized civilizations and caused population collapses via food shortages, diseases, and wars. One of the worst population collapses of human societies occurred during the early fourteenth century in northern Europe; the “Great Famine” was the consequence of the dramatic effects of climate deterioration on human population growth. Thus, part of my motivation was to demonstrate that simple theoretical‐based models can be helpful in understanding the causes of population change in preindustrial societies. Here, the results suggest that a logistic model with temperature as a “lateral” perturbation effect is the key element for explaining the population collapse exhibited by the European population during the “Great Famine”.     

Viability of the Endangered Little Bustard <Emphasis Type="Italic">Tetrax tetrax</Emphasis> Population of Western France

Stochastic computer simulations are used to evaluate the sensitivity of Little bustard population parameters, estimating the survival probabilities of the seven endangered Little bustard populations of central-western France for which conservation actions are currentlybeing or have been implemented. Different scenarios of parameter compensation for those nuclei to establish parameter levels assuring population viability are discussed. Adult survival, productivity per female, initial population size and carrying capacity were the most sensitive parameters in a hypothetical, isolated population. Juvenile survival also affected population survival, although its sensitivity was lower. Sex ratio did not have a linear effect on population survival, but probability of extinction increased for extreme values. Productivity per female and initial population size, varied strongly among the populations studied, determining their average time of extinction and growth rate. When a metapopulation scenario was simulated, the survival probabilities of each population and the metapopulations stayed close to 1.0 if no mortality was associated to migration. When mortality during migration was included in the simulations, the metapopulation's probability of survival significantly decreased under 90%. This approach may help managers to correctly address conservation measures and design effective strategies, which should be directed mainly to improve productivity, enhance female survival, and minimise mortality during migration (e.g. promoting insect-rich nesting substrates, avoiding female killing and nest destruction at harvesting, reducing the risk of collision with powerlines, or controlling poaching).     

Inherited phenotypic changes in the population dynamics of water vole (<Emphasis Type="Italic">Arvicola terrestris</Emphasis> L.) in Northern Baraba

A new method of studying genetic factors in phenotypical variability of rodents is applied for the cycling population of water vole (Arvicola terrestris L.) in Northern Baraba. The components of the maximum additive heritability are found via the correlations “parent-offspring” in vivarium population. The interannual phenotypical variability of natural rodent populations is studied in the space of these components. It is shown that radical genetic restructuring in the population takes place in the phase of low density. The genetic specificity of different cycles of vole population dynamics is confirmed as well. The changes of common animals sizes associated with population dynamics are determined by heterozygosity effects.     

Genetic signatures of population change in the British golden eagle (<Emphasis Type="Italic">Aquila chrysaetos</Emphasis>)

The golden eagle (Aquila chrysaetos) was once widely distributed in the uplands of the British Isles, but is now extinct in Ireland, and largely confined to the highlands and islands of Scotland. As the precise extent and severity of the reduction in population size are unclear, it is important to understand how the population was affected by the decline. We therefore genotyped 13 polymorphic microsatellite loci in 172 individuals from the contemporary British population and compared their genetic diversity to 70 British and 9 Irish museum specimens. Despite the recent population decline, there is only slight evidence for a concomitant loss of genetic variation. Instead, two likelihood-based Bayesian methods provided evidence for a severe ancient genetic bottleneck, possibly caused by the fragmentation of a large mainland European population and/or the founding effects of colonising the British Isles. As the population persisted despite this ancient bottleneck, our conclusion is that there is limited need for intervention to augment the present-day genetic diversity. The main short-term objective of conservation measures should be to increase population sizes by continuous safeguarding of individuals and habitat management. Finally, we also confirmed that, for management purposes, the species should be considered a single population unit and that the extinct Irish population was not differentiated from the British one.     

Density regulation in the Mediterranean leaf-toed gecko <Emphasis Type="Italic">Euleptes europaea</Emphasis>

Isolated populations are particularly prone to extinction, and understanding their temporal dynamics is relevant for conservation and management. In this study, the abundance of a population of the nocturnal leaf-toed gecko Euleptes europaea was estimated by mark-recapture over a 12-year period in northwest Italy. Simulation tests showed the presence of density-dependence, and autoregressive analyses indicated that direct density dependence was responsible for a large part of the variation in population growth rates. Density-dependent recruitment was suggested as the main demographic mechanism controlling population dynamics, which was also affected by solar radiation measured during the active gecko season. These results may contribute to implement conservation strategies in other small and isolated leaf-toed gecko populations.     

Detecting and managing an overgrazing-drought synergism in the threatened <Emphasis Type="Italic">Echeveria longissima</Emphasis> (Crassulaceae): the role of retrospective demographic analysis

Echeveria longissima, a threatened herb whose habitat has been severely overgrazed and eroded, was studied for three years in a currently grazed and a fenced area. Matrix population models were used to assess if livestock elimination provides a proper management strategy. The merits of retrospective perturbation analyses in terms of management planning have been debated. Nevertheless, they may prove useful when applied in combination with exclosures because they may detect the effects of anthropogenic disturbance on population dynamics. Thus, the results of retrospective and prospective methods were compared. A rapid decrease in population size was projected in both areas, even though it was faster in the exposed one. The demographic processes that were favourable or detrimental in a given year were magnified outside of the fence, but buffered in the exclosure, showing a strong drought-disturbance synergism. Thus, the largest difference in the population growth rate λ between areas was observed in the driest year. Higher nurse-plant density inside the fence seems to alleviate drought effects. The use of prospective analysis alone may lead to erroneous management decisions, since the highest elasticities corresponded to transitions that were favoured by human activities. While allowing for an increased λ in the short term, intervention aimed at increasing these transitions further without attending others that are lessened by disturbance may introduce large changes in the population dynamics, with negative long-term consequences. Retrospective methods can detect which processes have been altered by disturbance and its synergisms, so we may more efficiently restore healthy population dynamics.     

Co‐adaptation impacts the robustness of predator–prey dynamics against perturbations

Global change threatens the maintenance of ecosystem functions that are shaped by the persistence and dynamics of populations. It has been shown that the persistence of species increases if they possess larger trait adaptability. Here, we investigate whether trait adaptability also affects the robustness of population dynamics of interacting species and thereby shapes the reliability of ecosystem functions that are driven by these dynamics. We model co‐adaptation in a predator–prey system as changes to predator offense and prey defense due to evolution or phenotypic plasticity. We investigate how trait adaptation affects the robustness of population dynamics against press perturbations to environmental parameters and against pulse perturbations targeting species abundances and their trait values. Robustness of population dynamics is characterized by resilience, elasticity, and resistance. In addition to employing established measures for resilience and elasticity against pulse perturbations (extinction probability and return time), we propose the warping distance as a new measure for resistance against press perturbations, which compares the shapes and amplitudes of pre‐ and post‐perturbation population dynamics. As expected, we find that the robustness of population dynamics depends on the speed of adaptation, but in nontrivial ways. Elasticity increases with speed of adaptation as the system returns more rapidly to the pre‐perturbation state. Resilience, in turn, is enhanced by intermediate speeds of adaptation, as here trait adaptation dampens biomass oscillations. The resistance of population dynamics strongly depends on the target of the press perturbation, preventing a simple relationship with the adaptation speed. In general, we find that low robustness often coincides with high amplitudes of population dynamics. Hence, amplitudes may indicate the robustness against perturbations also in other natural systems with similar dynamics. Our findings show that besides counteracting extinctions, trait adaptation indeed strongly affects the robustness of population dynamics against press and pulse perturbations.     

Historical and recent reductions in genetic variation of the <Emphasis Type="Italic">Sarotherodon galilaeus</Emphasis> population in the Sea of Galilee

The Sea of Galilee has great significance as a natural habitat and a freshwater source for Israel. Anthropogenic impacts have been placing significant pressure on the species inhabiting this lake, among which is Sarotherodon galilaeus, an omnivorous fish with a relatively large population and significance for commercial fishing. An alarming decline in annual catch towards 2008 suggested that this unique population might be at risk. With that in mind, we characterized the current genetic variation of this species in Israel with reference to fish from Ghana, based on D-loop and microsatellite markers. Genetic variation and differentiation were found mostly among fish from Ghanaian localities and between fish from Israel and Ghana, whereas fish from all Israeli localities had uniform and limited variation, a signature compatible with historical founder effect followed by local adaptations. Such historical processes could leave a population vulnerable as reflected in the sudden and recent population decline. Comparing genetic variation between archived 30 year-old scales and modern lake fish revealed further reduction in genetic variation coincident with the recent population decline. Thus, a recently occurring genetic bottleneck had placed this unique and isolated population at an even higher risk. We carefully discuss the events leading to the current risk status for S. galilaeus in Israel and highlight the need for vigilant monitoring and active management to support a more sustainable future for this and other fish communities in this important habitat.     

Regional population structure of the endangered Bridle Shiner (<Emphasis Type="Italic">Notropis bifrenatus</Emphasis>)

In the last 100 years, the Bridle Shiner has declined over significant parts of its range. We used mitochondrial and nuclear microsatellite markers to investigate population structure of this species. Tissue samples were collected from populations in six drainages in PA, NJ, NY and CT. One predominant haplotype was observed in the Delaware, Housatonic, Passaic, and Raritan specimens. Specimens from the Hudson and St. Lawrence drainages had a separate unique haplotype. Microsatellite loci revealed low within-population genetic diversity and pairwise population comparisons of allelic divergence showed significant genetic differences among most drainages. Population structure analysis of microsatellite loci recover the same population clusters inferred using mtDNA. Within the Delaware drainage, there was significant differentiation among areas separated by 128 km. Several alternate scenarios of population divergence and population bottlenecks were investigated using approximate Bayesian computing. These supported a scenario with a bottleneck occurring in the ancestral population of Bridle Shiner followed by recent divergence of Northern and Southern drainages.     

Distribution of two chromosome races of the common shrew (<Emphasis Type="Italic">Sorex araneus</Emphasis> L.) in the hybrid zone: Can a change of the dispersal mode maintain independent gene frequencies?

Combination of different dispersal modes may itself, without external obstacles, lead to the appearance of subdivided populations and maintain the existence of independent population systems. The common shrew, a mammal convenient for studying different levels of intraspecific differentiation, was the object of the study. Empirical data have been used for simulation taking into account the change of dispersal modes in the population area. The obtained results agree with empirical data on the distribution of races and hybrids in the hybrid zone of chromosome races Moscow and Seliger. Change of the dispersal mode may maintain independent population dynamics and, in the case of chromosome races, prevent the migration of parental individuals into the territory of the other race.     

Morphological diversity of sockeye salmon (<Emphasis Type="Italic">Oncorhynchus nerka</Emphasis> (Walbaum)) of the Kamchatka River

A method based on morphological characters is proposed to evaluate biological diversity of a sockeye salmon population. In all samples, morphological diversity of males is greater than that of females. In addition, the inter-annual dynamics determined on the basis of separate morphological characters differs in individuals of different sex. The necessity of studying biological diversity for preserving population homeostasis is also considered.     

Photoreceptor spectral sensitivity in island and mainland populations of the bumblebee, <Emphasis Type="Italic">Bombus terrestris</Emphasis>

Most species of flower-visiting Hymenoptera are trichromatic, with photoreceptor spectral sensitivity peaks in the UV, blue and green regions of the spectrum. Red flowers, therefore, should be relatively difficult to detect for such insects. Nevertheless, in population biological studies in the bumblebee, Bombus terrestris, the Sardinian island population (B. t. sassaricus) displayed significantly higher responses to red artificial flowers (in tests of innate colour choice and detectability) than several mainland populations of the same species (Chittka et al. in Cognitive ecology of pollination, pp 106–126, 2001; Popul Ecol 46:243–251, 2004). Since there is relatively little physiological data on population differences in sensory systems, we used intracellular recording to compare photoreceptor spectral sensitivity in B. t. sassaricus and the southern European and Mediterranean population, B. t. dalmatinus. The results show both populations to be UV–blue–green trichromats, but with a small but significant increase in long-wave sensitivity in island bees. Spectral peaks were estimated at 348, 435 and 533 nm (B. t. dalmatinus) and 347, 436 and 538 nm (B. t. sassaricus) for UV, blue and green receptors, respectively. There were no significant differences in UV and blue receptor sensitivities. We found no photoreceptors maximally sensitive to red spectral light in the Sardinian population and model calculations indicate that the behavioural population differences in colour responses cannot be directly explained by receptor population differences. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Life‐history strategy varies with the strength of competition in a food‐limited ungulate population

Fluctuating population density in stochastic environments can contribute to maintain life‐history variation within populations via density‐dependent selection. We used individual‐based data from a population of Soay sheep to examine variation in life‐history strategies at high and low population density. We incorporated life‐history trade‐offs among survival, reproduction and body mass growth into structured population models and found support for the prediction that different life‐history strategies are optimal at low and high population densities. Shorter generation times and lower asymptotic body mass were selected for in high‐density environments even though heavier individuals had higher probabilities to survive and reproduce. In contrast, greater asymptotic body mass and longer generation times were optimal at low population density. If populations fluctuate between high density when resources are scarce, and low densities when they are abundant, the variation in density will generate fluctuating selection for different life‐history strategies, that could act to maintain life‐history variation.     

Putative native source of the invasive fire ant <Emphasis Type="Italic">Solenopsis invicta</Emphasis> in the USA

The ecological and evolutionary dynamics of newly introduced invasive species can best be understood by identifying the source population(s) from which they originated, as many species vary behaviorally, morphologically, and genetically across their native landscapes. We attempt to identify the source(s) of the red imported fire ant (Solenopsis invicta) in the southern USA utilizing data from three classes of genetic markers (allozymes, microsatellites, and mitochondrial DNA sequences) and employing Bayesian clustering simulations, assignment and exclusion tests, and phylogenetic and population genetic analyses. We conclude that the Mesopotamia flood plain near Formosa, Argentina represents the most probable source region for introduced S. invicta among the 10 localities sampled across the native South American range. This result confirms previous suspicions that the source population resides in northern Argentina, while adding further doubts to earlier claims that the Pantanal region of Brazil is the source area. Several lines of evidence suggest that S. invicta in the southern USA is derived from a single location rather than being the product of multiple invasions from widely separated source localities. Although finer-scale sampling of northern Argentina and Paraguay combined with the use of additional genetic markers will be necessary to provide a highly precise source population assignment, our current results are of immediate use in directing future sampling and focusing ongoing biological control efforts.     

Demographic and genetic consequences of population subdivision in Formosa land-locked salmon <Emphasis Type="Italic">Oncorhynchus masou formosanus</Emphasis>, the southernmost subspecies of the salmonids

A few studies have evaluated demographic and genetic consequences of population subdivision by damming on the population as a whole. Formosa landlocked salmon Oncorhynchus masou formosanus have persisted as a relatively large population that has recently been subdivided into seven subpopulations by erosion-control dams and a natural waterfall. The present study simulated the demographic and genetic dynamics of this subdivided salmon population using VORTEX, an individual-based stochastic model. Although the population as a whole did not experience extinction over 200 simulation years, the loss of genetic variation was often detrimental (>10% loss). Isolated headwater subpopulations frequently reached extinction. Even when the subpopulations did persist through the 200 years, they experienced dramatic loss of genetic variation, suggesting short-term genetic threats. Due to the unidirectional dispersal of the fish, the damming puts headwater subpopulations at higher risk of extinction and loss of genetic variation, which affects persistence of the population as a whole, particularly from a genetic perspective.     

On the origin of Solovetskaya vendace <Emphasis Type="Italic">Coregonus albula</Emphasis> and of the syamozero smelt <Emphasis Type="Italic">Osmerus eperlanus</Emphasis>

The genetic analysis is made on the population of the European smelt Osmerus eperlanus occasionally introduced to Lake Syamozero (Karelia) and of the vendace Coregous albula supposedly acclimatized in Solovetskie Islands as a result of fish cultural activities of the Solovetskii Monastery. They are compared with several natural populations—possible donors for both introductions. Genetic variation in a sample of smelt was estimated by means of restrictase analysis of mtDNA (fragment ND1/ND2) in samples of vendace—by means of allozyme analysis of six isoenzyme systems. The probable population for the Syamozero smelt is the population of Onega Lake in spite of the previously noted greater morphological similarity of colonizers with the smelt of Ladoga Lake. A high level of genetic variation in the Syamozero smelt in comparison with native populations indicates that, beside the introduction from Onega Lake, there were repeated introductions from neighboring water bodies. The genetic analysis of the Solovetskaya vendace does not prove that the vendace appeared on islands due to acclimatization. Frequencies of alleles of allozyme loci in the Solovetskaya population significantly differ from frequencies in continental populations. Still, it is compared with some populations of the Arkhangelsk oblast. Estimations of genetic diversity of the Solovetskaya vendace turned out to be comparable with those in native populations.     

Long-term demographic analysis in goshawk <Emphasis Type="Italic">Accipiter gentilis</Emphasis>: the role of density dependence and stochasticity

Density dependence and environmental stochasticity are both potentially important processes influencing population demography and long-term population growth. Quantifying the importance of these two processes for population growth requires both long-term population as well as individual-based data. I use a 30-year data set on a goshawk Accipiter gentilis population from Eastern Westphalia, Germany, to describe the key vital rate elements to which the growth rate is most sensitive and test how environmental stochasticity and density dependence affect long-term population growth. The asymptotic growth rate of the fully age-structured mean matrix model was very similar to the observed one (0.7% vs. 0.3% per annum), and population growth was most elastic to changes in survival rate at age classes 1-3. Environmental stochasticity led only to a small change in the projected population growth rate (between -0.16% and 0.67%) and did not change the elasticities qualitatively, suggesting that the goshawk life history of early reproduction coupled with high annual fertility buffers against a variable environment. Age classes most crucial to population growth were those in which density dependence seemed to act most strongly. This emphasises the importance of density dependence as a regulatory mechanism in this goshawk population. It also provides a mechanism that might enable the population to recover from population lows, because a mean matrix model incorporating observed functional responses of both vital rates to population density coupled with environmental stochasticity reduced long-term extinction risk of 30% under density-independent environmental stochasticity and 60% under demographic stochasticity to zero.     

Genetic population structure of the Fire-bellied toad <Emphasis Type="Italic">Bombina bombina</Emphasis> in an area of high population density: implications for conservation

In this study, we report the genetic population structure of the Fire-bellied toad Bombina bombina in Brandenburg (East Germany) in the context of conservation. We analysed 298 samples originating from 11 populations in Brandenburg using mitochondrial control region sequences and six polymorphic microsatellite loci. For comparison, we included one population each from Poland and Ukraine into our analysis. Within Brandenburg, we detected a moderate variability in the mitochondrial control region (19 different haplotypes) and at microsatellite loci (9–12 alleles per locus). These polymorphisms revealed a clear population structure among toads in Brandenburg, despite a relatively high overall population density and the moderate size of single populations (100–2000 individuals). The overall genetic population structure is consistent with a postglacial colonization from South East-Europe and a subsequent population expansion. Based on genetic connectivity, we infer Management Units (MUs) as targets for conservation. Our genetic survey identified MUs, within which human infrastructure is currently preventing any genetic exchange. We also detect an unintentional translocation from South East to North West Brandenburg, presumably in the course of fish stocking activities. Provided suitable conservation measures are taken, Brandenburg should continue to harbor large populations of this critically endangered species.     

Population genetics of the cytoplasm and the units of selection on mitochondrial DNA in <Emphasis Type="Italic">Drosophila melanogaster</Emphasis>

Biological variation exists across a nested set of hierarchical levels from nucleotides within genes to populations within species to lineages within the tree of life. How selection acts across this hierarchy is a long-standing question in evolutionary biology. Recent studies have suggested that genome size is influenced largely by the balance of selection, mutation and drift in lineages with different population sizes. Here we use population cage and maternal transmission experiments to identify the relative strength of selection at an individual and cytoplasmic level. No significant trends were observed in the frequency of large (L) and small (S) mtDNAs across 14 generations in population cages. In all replicate cages, new length variants were observed in heteroplasmic states indicating that spontaneous length mutations occurred in these experimental populations. Heteroplasmic flies carrying L genomes were more frequent than those carrying S genomes suggesting an asymmetric mutation dynamic from larger to smaller mtDNAs. Mother-offspring transmission of heteroplasmy showed that the L mtDNA increased in frequency within flies both between and within generations despite sampling drift of the same intensity as occurred in population cages. These results suggest that selection for mtDNA size is stronger at the cytoplasmic than at the organismal level. The fixation of novel mtDNAs within and between species requires a transient intracellular heteroplasmic stage. The balance of population genetic forces at the cytoplasmic and individual levels governs the units of selection on mtDNA, and has implications for evolutionary inference as well as for the effects of mtDNA mutations on fitness, disease and aging.