Population Structure and Dispersal Patterns within and between Atlantic and Mediterranean Populations of a Large-Range Pelagic Seabird

Dispersal is critically linked to the demographic and evolutionary trajectories of populations, but in most seabird species it may be difficult to estimate. Using molecular tools, we explored population structure and the spatial dispersal pattern of a highly pelagic but philopatric seabird, the Cory''s shearwater Calonectris diomedea. Microsatellite fragments were analysed from samples collected across almost the entire breeding range of the species. To help disentangle the taxonomic status of the two subspecies described, the Atlantic form C. d. borealis and the Mediterranean form C. d. diomedea, we analysed genetic divergence between subspecies and quantified both historical and recent migration rates between the Mediterranean and Atlantic basins. We also searched for evidence of isolation by distance (IBD) and addressed spatial patterns of gene flow. We found a low genetic structure in the Mediterranean basin. Conversely, strong genetic differentiation appeared in the Atlantic basin. Even if the species was mostly philopatric (97%), results suggest recent dispersal between basins, especially from the Atlantic to the Mediterranean (aprox. 10% of migrants/generation across the last two generations). Long-term gene flow analyses also suggested an historical exchange between basins (about 70 breeders/generation). Spatial analysis of genetic variation indicates that distance is not the main factor in shaping genetic structure in this species. Given our results we recommend gathering more data before concluded whether these taxa should be treated as two species or subspecies.     

Characteristics of migration in the population of Yevpatoria (Crimea)

Indicators characterizing population migration were calculated according to the marriage records of Yevpatoria (Crimea) of 1960/1961, 1985, and 1994/1995. The marital migration coefficient m in those years was 0.80, 0.75, and 0.66, the endogamy index was 0.04, 0.08, and 0.15, and the rate of marriage contingency by birthplace was 0.15, 0.16, and 0.19, respectively. The highest values of the positive mating assortative index were recorded for people from the Caucasus, Central, Central Black Earth Oblast, and Northwest regions of Russia in 1960/1961 and for migrants from Moldavia, the republics of Central Asia and Caucasus, Western Siberia, and Ukraine in 1985. In 1994/1995, natives of Yevpatoria were also included in this group. The average distance of migration by year was 909, 1280, and 1314 km, and the marital distance was 960, 1397, and 1171 km. The “radius” of the Yevpatoria population, in accordance with the Maleco model in the years under study, was 98, 134, and 137 km. The distance isolation indicator b was decreasing and amounted to 0.00049, 0.00043, and 0.00038. In the migration flow in all of the periods, the majority of immigrants came from different regions of Ukraine outside Crimea (27–31%), followed by natives of various places in Crimea (21–24%), Central (3.6–8.5%), and Central Black Earth (1.8–6.1%) regions of Russia, and the South Caucasus (4.0–5.7%). The proportion of Russians and Jews decreased in the migration flow, while the proportion of Ukrainians and representatives of non-Slavic nationalities increased.     

Higher Rate of Tuberculosis in Second Generation Migrants Compared to Native Residents in a Metropolitan Setting in Western Europe

Background

In Western Europe, migrants constitute an important risk group for tuberculosis, but little is known about successive generations of migrants. We aimed to characterize migration among tuberculosis cases in Berlin and to estimate annual rates of tuberculosis in two subsequent migrant generations. We hypothesized that second generation migrants born in Germany are at higher risk of tuberculosis compared to native (non-migrant) residents.

Methods

A prospective cross-sectional study was conducted. All tuberculosis cases reported to health authorities in Berlin between 11/2010 and 10/2011 were eligible. Interviews were conducted using a structured questionnaire including demographic data, migration history of patients and their parents, and language use. Tuberculosis rates were estimated using 2011 census data.

Results

Of 314 tuberculosis cases reported, 154 (49.0%) participated. Of these, 81 (52.6%) were first-, 14 (9.1%) were second generation migrants, and 59 (38.3%) were native residents. The tuberculosis rate per 100,000 individuals was 28.3 (95CI: 24.0–32.6) in first-, 10.2 (95%CI: 6.1–16.6) in second generation migrants, and 4.6 (95%CI: 3.7–5.6) in native residents. When combining information from the standard notification variables country of birth and citizenship, the sensitivity to detect second generation migration was 28.6%.

Conclusions

There is a higher rate of tuberculosis among second generation migrants compared to native residents in Berlin. This may be explained by presumably frequent contact and transmission within migrant populations. Second generation migration is insufficiently captured by the surveillance variables country of birth and citizenship. Surveillance systems in Western Europe should allow for quantifying the tuberculosis burden in this important risk group.     

Genetic demographic data of Ukrainian urban populations in the 1990s: ethno-geographic characteristics of migrants in the Donetsk region

Analysis of data on the birthplaces and ethnicity of persons who contracted marriages in the city of Donetsk in 1960, 1985, and 1992 demonstrated that the proportions of Russians and Ukrainians (the dominant ethnic groups among Donetsk residents) in the migration flow increased. The trend towards formation of ethnically disperse groups from the city residents became stronger. The index of isolation by distance (parameter b of Malecot's model) was 0.00103, 0.00071, and 0.00083 in 1960, 1985, and 1992, respectively. The proportions of long-range and short-range migrants increased by 1.2 times and decreased by 2.3 times, respectively, during the period studied. The locality size of the Donetsk population was 50, 62, and 53 km in 1960, 1985, and 1992, respectively. The highest isolation by distance was observed in Jews and Greeks and the lowest one, in Russians.     

Genetic Demography of Ukrainian Urban Populations in the 1990s: Ethnic Geographic Characteristics of Migration in the Donetsk Population

Analysis of data on the birthplaces and ethnicity of persons who contracted marriages in the city of Donetsk in 1960, 1985, and 1992 demonstrated that the proportions of Russians and Ukrainians (the dominant ethnic groups among Donetsk residents) in the migration flow increased. The trend towards formation of ethnically disperse groups from the city residents became stronger. The index of isolation by distance (parameter b of Malecot's model) was 0.00103, 0.00071, and 0.00083 in 1960, 1985, and 1992, respectively. The proportions of long-range and short-range migrants increased by 1.2 times and decreased by 2.3 times, respectively, during the period studied. The locality size of the Donetsk population was 50, 62, and 53 km in 1960, 1985, and 1992, respectively. The highest isolation by distance was observed in Jews and Greeks and the lowest one, in Russians.     

Spring passerine migrants stopping over in the Sahara are not fall-outs

The strategy of migrants crossing the Sahara desert has been the subject of debate, but recent evidence from radar studies has confirmed that most passerines use an intermittent migration strategy. The latter has also been suggested from previous studies in oases during autumn migration. It was found that migrants with relatively high fuel loads rest in the desert during daytime and continue migration during the following night, whereas lean migrants stopover in oases for several days to refuel. However, data from the Sahara are scarce for spring migration. We captured passerine migrants near B?r Amrane (22°47′N, 8°43′W) in the plain desert of Mauritania for 3 weeks during spring migration in 2004. We estimated flight ranges of 85 passerines stopping over in the desert to test whether they carried sufficient fuel loads to accomplish migration across the Sahara successfully. High fat loads of the majority of birds indicated that they were neither “fall-outs” nor too weak to accomplish migration successfully. The flight range estimates, based on mean flight speeds derived from radar measurements (59 km/h), revealed that 85% of all birds were able to reach the northern fringe of the desert with an intermittent migration strategy. Furthermore, birds stopping over in an oasis (Ouadane, 370 km to the southwest of B?r Amrane) did not carry consistently lower fuel loads compared to the migrants captured in the desert.     

Adaptive migratory divergence among sympatric brook charr populations

Ecological processes clearly contribute to population divergence, yet how they interact over complex life cycles remains poorly understood. Notably, the evolutionary consequences of migration between breeding and non-breeding areas have received limited attention. We provide evidence for a negative association between interpopulation differences in migration (between breeding and feeding areas, as well as within each) and the amount of gene flow (m) among three brook charr (Salvelinus fontinalis) populations inhabiting Mistassini Lake, Quebec, Canada. Individuals (n = 1166) captured throughout lake feeding areas over two consecutive sampling years were genotyped (10 microsatellites) and assigned to one of the three populations. Interpopulation differences in migration were compared based on spatial distribution overlap, habitat selection, migration distance within feeding areas, and morphology. We observed a temporally stable, heterogeneous spatial distribution within feeding areas among populations, with the extent of spatial segregation related to differential habitat selection (represented by littoral zone substrate). Spatial segregation was lowest and gene flow highest (m = 0.015) between two populations breeding in separate lake inflows. Segregation was highest and gene flow was lowest (mean m = 0.007) between inflow populations and a third population breeding in the outflow. Compared to outflow migrants, inflow migrants showed longer migration distances within feeding areas (64-70 km vs. 22 km). After entering natal rivers to breed, inflow migrants also migrated longer distances (35-75 km) and at greater elevations (50-150 m) to breeding areas than outflow migrants (0-15 km; -10-0 m). Accordingly, inflow migrants were more streamlined with longer caudal regions, traits known to improve swimming efficiency. There was no association between the geographic distance separating population pairs and the amount of gene flow they exchanged. Collectively, our results are consistent with the hypothesis that reduced gene flow between these brook charr populations results from divergent natural selection leading to interpopulation differences in migration. They also illustrate how phenotypic and genetic differentiation may arise over complex migratory life cycles.     

Population structure and anthropometric variation in rural western Ireland: Isolation by distance and analysis of the residuals

The study of human population structure allows the assessment of cultural and historical influences on mating probabilities, and, hence, genetic variation. A commonly used model is isolation by distance, which predicts a negative exponential relationship between genetic similarity and geographic distance. Anthropometric data collected during the 1930's for 261 adult women in 12 towns of rural western Ireland were used to test the isolation by distance model and to assess the influence of cultural factors upon the fit of the model. The effects of recent migration were tested by using two additional data subsets, one excluding known intercounty migrants and the other consisting of unmarried women, only in an attempt to control partially for local migration upon marriage. Deviations from the expected isolation by distance model were analyzed using rotational fitting and regression analysis. Estimates of the isolation by distance parameters agree closely with independent estimates from isonymy and with estimates obtained in other studies of rural European population structure. Analysis of the residuals indicates three major factors which contribute to deviations from the expected model: recent migration upon marriage, age variation among groups, and variation in population size and/or transportation opportunities. Variation in population size was tested using the gravity model of economic geography by regressing the residuals from the isolation by distance model for each pair of towns on the product of their population sizes. The best fit occurred for the unmarried sample, as expected from ethnographic evidence, since rural–urban migration was most common among unmarried women.     

Diffuse, short and slow migration among Blue Tits

The knowledge of migration systems in long-distance regular migrants is in many cases extensive. Our understanding of the migratory characteristics of partial migrants, on the other hand, is far more rudimentary. We investigated migratory characteristics of partially migratory Blue Tits Cyanistes caeruleus using ringing recoveries of Swedish birds, to answer questions about geographic migration patterns, age-specific migrations, migration speeds and synchrony of movements. Median migration distance of Swedish Blue Tits was 82 km, with a main autumn direction in the sector between S and W (large directional scatter). Northerly and southerly populations did not differ in migration directions or distances, suggesting chain migration to be the general pattern. A larger proportion of adult Blue Tits remained near the breeding grounds during winter than was the case for juveniles. Some of the migrating birds (17%) seemed not to return in spring but stayed to breed closer to the winter area. Swedish Blue Tits show an exceptionally slow migration speed (median 13 km/day), among the slowest speeds recorded for any migrant bird. The Blue Tit represents an extreme case of diffuse, short and slow bird migration.     

Short distance migrants travel as far as long distance migrants in lesser black‐backed gulls Larus fuscus

Migration strategies differ greatly among and within avian populations. The associated trade‐offs and fitness consequences of diverse strategies and how they persist are pertinent questions in migration research. Migration is a costly endeavour, presumably compensated for by better survival conditions in the non‐breeding area. One way to assess the cost of alternative strategies is to investigate the investment in movement across the entire annual cycle, an assessment made increasingly feasible with improvements in tracking technology. Our study focuses on lesser black‐backed gulls, generalist seabirds that exploit a broad range of resources, exhibit diverse migration strategies and have potentially altered migration strategies in response to human activities and climate change. We used GPS tracking to quantify lesser black‐backed gulls’ movement throughout their annual cycle and compare trade‐offs among four migration strategies. The annual cumulative distance travelled by long distance migrants wintering in west Africa, over 4000 km from their breeding colony, did not differ significantly from individuals of the same breeding colony wintering only a few hundred kilometres away in Great Britain. Short distance migrants returned to the colony first, and long distance migrants returned last. Sex and wing length were not correlated with maximum range, cumulative distance travelled or timing. Individuals spent only a small proportion of their time in flight and spent on average 17% of their time at sea throughout an annual cycle, suggesting a reliance on inland resources for many individuals. Analysing movement throughout the annual cycle can change our perspective and understanding of consequences of different migration strategies. Our study shows that a range of migration strategies coexists and we propose that the long term costs and benefits of these strategies balance out. Diversity in migration strategies may contribute to the resilience of this species in the face of ongoing anthropogenic impact on the environment.     

Marriage structure of Yakut populations: Migrations

Rural and urban settlements of the Republic of Sakha (Yakutia) are characterized by intense marriage migrations: both indigenous residents of different uluses (districts) of the republic (7–30%) and migrants from outside Yakutia (7–29%) contract marriages in five administrative centers analyzed in this respect. All the populations studied are characterized by a wide geographic range of the birthplaces of persons contracted marriages there (from 14 to 24 uluses of Yakutia), without any predominant migration flow from one district to another. The proportion of homolocal marriages among indigenous ethnic groups (Evenks, Evens, and Yukagirs) is as high as 75–100%; this proportion among Yakuts varies from 26 to 68%; heterolocal marriages are more characteristic of Russian immigrants (41–95%). Positive assortative marriages among persons with the same birthplaces have been found in all populations except for Momsky ulus.     

Demographic uniformitarianism: the theoretical basis of prehistoric demographic research and its cross-disciplinary challenges

A principle of demographic uniformitarianism underpins all research into prehistoric demography (palaeodemography). This principle—which argues for continuity in the evolved mechanisms underlying modern human demographic processes and their response to environmental stimuli between past and present—provides the cross-disciplinary basis for palaeodemographic reconstruction and analysis. Prompted by the recent growth and interest in the field of prehistoric demography, this paper reviews the principle of demographic uniformitarianism, evaluates how it relates to two key debates in palaeodemographic research and seeks to delimit its range of applicability to past human and hominin populations.This article is part of the theme issue ‘Cross-disciplinary approaches to prehistoric demography’.     

Spatial and geographic characteristics of marriage migration in the Lugansk population

Data from the Lugansk City Registry Office archives of 1960, 1985, 1990, and 2000 were used to calculate genetic demographic parameters characterizing marriage migration. The migration coefficients (m) in these years were 0.69, 0.54, 0.47, and 0.36; the endogamy indices were 12.1, 24.4, 30.5, and 43.2%, and the marriage contingency coefficients with respect to birthplace (K) were 0.12, 0.10, 0.11, and 0.13, respectively. The mean migration distance increased by a factor of 1.5 (from 599 to 870 km), and the mean parent-offspring distance decreased by a factor of 1.3 (from 415 to 317 km) during the period between 1960 and 2000. The mean marriage distance increased from 654 to 718 km between 1960 and 1985 and then decreased to 594 km by the year 2000. The proportion of "long-distance" migrations calculated using Malecot's model increased from 0.013 to 0.021 between 1960 and 1990 and decreased to 0.005 by 2000. The proportion of "short-distance" migrations was 0.77 in 1960 and 0.51 in 2000. The migration efficiency increased from 0.09 to 0.18 between 1960 and 1990 and decreased to 0.07 by 2000. In the years studied, the indices of isolation by distance (b) were 0.0005, 0.0004, 0.0005, and 0.0002, and the population "radii" were 90, 118, 119, and 168 km, respectively.     

Effects of migration distance and sex on stopover timing and refueling by Wilson's Warblers

Migration distance and sex are integral to avian migration strategies, yet these intrinsic factors are understudied with respect to their effects on stopover ecology and behavior. We investigated how individual variation in migration distance and sex affected body condition, refueling performance, and stopover durations of Wilson's Warblers (Cardellina pusilla) during spring and fall 2006 at a stopover site in southern Arizona. Migration distance of individuals was inferred using the hydrogen stable isotope ratio of feathers (δ²H_f) as an index of breeding latitude, refueling rate was assessed using plasma triglyceride and β‐OH‐butyrate, and minimum length of stay was estimated by re‐sighting color‐banded birds. In the spring, migration distance and sex were strong determinants of the timing of migration by Wilson's Warblers, with males and shorter‐distance migrants passing through the site earlier than females and longer‐distance migrants. Later‐arriving migrants also had higher fat scores and refueling rates. However, neither migration distance nor sex independently affected body condition (fat score or size‐corrected mass), refueling rate, or minimum length of stay. In a smaller sample of fall migrants, we found that longer‐distance migrants and males had higher refueling rates than shorter‐distance migrants and females. Our results show that differences in migration distance can, under some circumstances, affect how birds use stopover sites. Stable isotope analysis and other methods can provide information on migration distance, and should be integrated with measurements of timing, fuel stores, refueling performance, and departure behavior to gain a deeper understanding of bird migration.     

Spatial and geographic characteristics of marriage migration in the Lugansk population

Data from the Lugansk City Registry Office archives of 1960, 1985, 1990, and 2000 were used to calculate genetic demographic parameters characterizing marriage migration. The migration coefficients (m) in these years were 0.69, 0.54, 0.47, and 0.36; the endogamy indices were 12.1, 24.4, 30.5, and 43.2%, and the marriage contingency coefficients with respect to birthplace (K) were 0.12, 0.10, 0.11, and 0.13, respectively. The mean migration distance increased by a factor of 1.5 (from 599 to 870 km), and the mean parent-offspring distance decreased by a factor of 1.3 (from 415 to 317 km) during the period between 1960 and 2000. The mean marriage distance increased from 654 to 718 km between 1960 and 1985 and then decreased to 594 km by the year 2000. The proportion of “long-distance” migrations calculated using Malecot’s model increased from 0.013 to 0.021 between 1960 and 1990 and decreased to 0.005 by 2000. The proportion of “short-distance” migrations was 0.77 in 1960 and 0.51 in 2000. The migration efficiency increased from 0.09 to 0.18 between 1960 and 1990 and decreased to 0.07 by 2000. In the years studied, the indices of isolation by distance (b) were 0.0005, 0.0004, 0.0005, and 0.0002, and the population “radii” were 90, 118, 119, and 168 km, respectively.     

Inclusive fitness and differential productivity across the life course determine intergenerational transfers in a small-scale human society

Transfers of resources between generations are an essential element in current models of human life-history evolution accounting for prolonged development, extended lifespan and menopause. Integrating these models with Hamilton''s theory of inclusive fitness, we predict that the interaction of biological kinship with the age-schedule of resource production should be a key driver of intergenerational transfers. In the empirical case of Tsimane’ forager–horticulturalists in Bolivian Amazonia, we provide a detailed characterization of net transfers of food according to age, sex, kinship and the net need of donors and recipients. We show that parents, grandparents and siblings provide significant net downward transfers of food across generations. We demonstrate that the extent of provisioning responds facultatively to variation in the productivity and demographic composition of families, as predicted by the theory. We hypothesize that the motivation to provide these critical transfers is a fundamental force that binds together human nuclear and extended families. The ubiquity of three-generational families in human societies may thus be a direct reflection of fundamental evolutionary constraints on an organism''s life-history and social organization.     

Short‐distance migration of Wrynecks Jynx torquilla from Central European populations

European Wrynecks Jynx torquilla torquilla have generally been considered to be long‐distance Palaearctic–African migrants that spend the non‐breeding season in Sahelian Africa, where they have been reported regularly. Results from tracking individual birds showed that Wrynecks from two Central European populations migrated only relatively short distances to the Iberian Peninsula and northwestern Africa (c. 1500 km and 3000 km, respectively), compared with a minimum distance of about 4500 km to Sahelian Africa. Additionally, differences in wing lengths of populations from Central and Northern Europe support the idea of leap‐frog migration, populations from Northern Europe being long‐distance migrants with a non‐breeding distribution in Sahelian Africa.     

Measuring selection in human populations using the growth rate per generation

Estimates of the speed of evolution between generations depend on the association between individual traits and a measure of fitness. The two most frequently used measures of fitness are the net reproduction rate and the 1-year growth factor implied by the fertility and mortality rates. Results based on the two lead to very different results. The reason is that the 1-year growth factor is not a measure of change between generations. Therefore, studies of changes between generations should use the amount of growth over the length of a generation. This is especially important for studies of human populations because of the long length of generation. In addition, estimates based on a single year''s growth are overly sensitive to data on individuals who fail to reproduce. The effects of using a generational measure are demonstrated using data from Kenya and Ukraine. These results demonstrate that using a 1-year growth rate to measure fitness leads to estimates that understate the rate at which evolution changes the characteristics of a human population.     

A Comparative Assessment of Genetic Diversity among Differently-Aged Populations of Spartina alternif lora on Restored Versus Natural Wetlands

We collected naturally recolonizing Spartina alterniflora (smooth cord grass) from each of three restored sites and one undisturbed reference site in southwestern Louisiana to assess the impact of wetland restoration on genetic diversity. We used amplified fragment length polymorphisms (AFLPs) to produce 94 polymorphic genetic markers, which were used to characterize genetic diversity as average heterozygosity and the proportion of polymorphic loci

. Overall our findings indicate that restored populations of S. alterniflora maintain levels of genetic diversity comparable to natural populations, which should provide some measure of resistance against environmental disturbances. Diversity estimates were lowest for the natural reference site ( = 0.1059;

= 0.2763), whereas estimates for the three restored sites ranged from < H > = 0.1148 to 0.1256 and

= 0.3114 to 0.3202. All sites maintained sufficiently high diversity levels to suggest significant rates of outcrossing. Overall, genetic differentiation among populations was small (Weir and Cockerham's Θ = 0.0645), with the values from each pairwise comparison among the populations increasing with the geographic distance between sites (range = 0.0490–0.1101). These values indicate an average migration rate of 3.6 migrants, either pollen or seeds, per generation.     

Functional endemism: population connectivity,shifting baselines,and the scale of human experience

Quantifying population connectivity is important for visualizing the spatial and temporal scales that conservation measures act upon. Traditionally, migration based on genetic data has been reported in migrants per generation. However, the temporal scales over which this migration may occur do not necessarily accommodate the scales over which human perturbations occur, leaving the potential for a disconnect between population genetic data and conservation action based on those data. Here, we present a new metric called the “Rule of Memory”, which helps conservation practitioners to interpret “migrants per generation” in the context both of human modified ecosystems and the cultural memory of those doing the modification. Our rule states that clades should be considered functionally endemic regardless of their actual taxonomic designation if the migration between locations is insufficient to maintain a viable population over the timescales of one human generation (20 years). Since larger animals are more likely to be remembered, we quantify the relationship between migrants per human (N) and body mass of the organism in question (M) with the formula N = 10M⁻¹. We then use the coral reef fish Pomacentrus moluccensis to demonstrate the taxonomic and spatial scales over which this rule can be applied. Going beyond minimum viable population literature, this metric assesses the probability that a clade''s existence will be forgotten by people throughout its range during a period of extirpation. Because conservation plans are predicated on having well-established baselines, a loss of a species over the range of one human generation evokes the likelihood of that species no longer being recognized as a member of an ecosystem, and thus being excluded in restoration or conservation prioritization. [Correction added on 26 December 2012, after first online publication: this formula has been corrected to N=10M⁻¹].