Colonization, genetic diversity, and evolution in the Swedish sand lizard, Lacerta agilis (Reptilia, Squamata)

The Swedish sand lizard ( Lacerta agilis ) is a relict species from the post-glacial warmth period. From the geological history of this region, and more recent data on population fragmentation due to disturbance by man, it can be surmised that the Swedish sand lizards passed through at least one population bottleneck in relatively recent times. We tested this hypothesis by investigating the amount and structuring of genetic variability in six microsatellite loci in ten lizard populations from different parts of Sweden. We contrasted these data against those from a Hungarian population which we have reason to assume strongly resembles the founder population for Swedish sand lizards. The average number of alleles per locus in Sweden was 3.3, and these alleles were common in almost all populations, whereas the average number of alleles in the Hungarian population was 8.0. Likewise, the level of expected heterozygosity was lower in the Swedish populations (0.45) compared to the Hungarian population (0.70). The lower variability in Swedish populations is probably a consequence of a common population bottleneck during the immigration subsequent to the latest glacial period. The remaining variability is strongly subdivided between populations (F_ST=0.30) with the main genetic differences being between rather than within populations. Despite the marked isolation of the populations and the present small population sizes (N= 10–300 adults), the Swedish relict populations show a surprisingly high level of observed heterozygosity, indicating that small population size is probably a recent phenomenon.     

PROCLAMATION

Natural hybridisation in Old World buzzards (Buteo) is an uncommon phenomenon with important ecological implications. This genus constitutes an intricate radiation of genetically poorly differentiated raptors whose taxonomic classification is a frequent subject of debate. We report the first case of successful hybridisation between the African subspecies of the Long-legged Buzzard Buteo rufinus cirtensis and Common Buzzard Buteo buteo buteo in a new contact zone in the Strait of Gibraltar (southern Spain). The hybrid offspring showed mixed characters from parental species indicating that, among others, hybridisation could explain the increasing presence of phenotypically odd reddish buzzards in southern Spain and northern Morocco. Given their close phylogenetic relation and their recently reduced allopatry, an increase in the hybridisation rate, fertile descendants and genetic introgression seem to be viable. We identify the potential contact zones where genetic monitoring is needed to gain insight on the real extent of this hybridisation and its possible effects on the current climate change scenario.     

Bark consumption of voles in relation to snow cover, population density and grazing impact

The voles Microtus agrestis and Clethrionomys glareolus consume more bark in north than in south Sweden in spite of lower availability in the former area due to snow-pressed ground. Field experiments with genetically homogeneous aspen sticks demonstrated that this pattern reflects differences in animal behaviour and not differences in plant palatability. Within a region consumption in snow-pressed areas was usually less than in subnivean spaces or runways. The amount of bark consumption was generally correlated with population density and amount of grazing impact. Great differences in bark consumption between north Swedish areas with high peak vole populations and south-central Swedish areas with moderate peak numbers imply that nutrition is of different importance at population declines in different regions. The ability of voles to move into snow-pressed areas and locate woody sticks in the snow suggests that control of ground cover will not protect tree seedlings at reforestation.     

The genetic structure of the Swedish population

Patterns of genetic diversity have previously been shown to mirror geography on a global scale and within continents and individual countries. Using genome-wide SNP data on 5174 Swedes with extensive geographical coverage, we analyzed the genetic structure of the Swedish population. We observed strong differences between the far northern counties and the remaining counties. The population of Dalarna county, in north middle Sweden, which borders southern Norway, also appears to differ markedly from other counties, possibly due to this county having more individuals with remote Finnish or Norwegian ancestry than other counties. An analysis of genetic differentiation (based on pairwise F(st)) indicated that the population of Sweden's southernmost counties are genetically closer to the HapMap CEU samples of Northern European ancestry than to the populations of Sweden's northernmost counties. In a comparison of extended homozygous segments, we detected a clear divide between southern and northern Sweden with small differences between the southern counties and considerably more segments in northern Sweden. Both the increased degree of homozygosity in the north and the large genetic differences between the south and the north may have arisen due to a small population in the north and the vast geographical distances between towns and villages in the north, in contrast to the more densely settled southern parts of Sweden. Our findings have implications for future genome-wide association studies (GWAS) with respect to the matching of cases and controls and the need for within-county matching. We have shown that genetic differences within a single country may be substantial, even when viewed on a European scale. Thus, population stratification needs to be accounted for, even within a country like Sweden, which is often perceived to be relatively homogenous and a favourable resource for genetic mapping, otherwise inferences based on genetic data may lead to false conclusions.     

Hematologic and hematochemical characteristics of the herring gull (Larus argentatus) and the buzzard (Buteo buteo)

Some hematological and hematochemical parameters in eight herring gulls (Larus argentatus) and in six buzzards (Buteo buteo) were checked. The buzzards were fed with ovine meat exclusively, while the herring gulls were fed with fish and ovine meat. Considerable differences between the two species were noted, particularly as far as the hematological and lipidic parameters are concerned. These differences are probably related to the aquatic life of the herring gull.     

Landscape structure, clonal propagation, and genetic diversity in Scandinavian populations of Arabidopsis lyrata (Brassicaceae)

Colonization history, landscape structure, and environmental conditions may influence patterns of neutral genetic variation because of their effects on gene flow and reproductive mode. We compared variation at microsatellite loci within and among 26 Arabidopsis lyrata populations in two disjunct areas of its distribution in northern Europe (Norway and Sweden). The two areas probably share a common colonization history but differ in size (Norwegian range markedly larger than Swedish range), landscape structure (mountains vs. coast), and habitat conditions likely to affect patterns of gene flow and opportunities for sexual reproduction. Within-population genetic diversity was not related to latitude but was higher in Sweden than in Norway. Population differentiation was stronger among Norwegian than among Swedish populations (F(ST) = 0.23 vs. F(ST) = 0.18). The frequency of clonal propagation (proportion of identical multilocus genotypes) increased with decreasing population size, was higher in Norwegian than in Swedish populations, but was not related to altitude or substrate. Differences in genetic structure are discussed in relation to population characteristics and range size in the two areas. The results demonstrate that the possibility of clonal propagation should be considered when developing strategies for sampling and analyzing data in ecological and genetic studies of this emerging model species.     

THE MIGRATION OF RAPTORS AND STORKS THROUGH THE NEAR EAST IN AUTUMN

Between 1963 and 1965 three expeditions have investigated the autumn migration of raptors and storks, on two occasions in southeast Turkey, and once in Lebanon.
Nearly all the soaring birds leaving Europe by the Bosphorus cross Asia Minor and turn south at the Gulf of Iskenderun. The commonest of these migrants are White Stork Ciconia ciconia , Honey Buzzard Pernis apivorus , and Eagles Aquila spp.
Other species such as Common Buzzard Buteo buteo are not usually seen crossing the Bosphorus, but occur in large numbers in the flocks seen south of the Gulf of Iskenderun. It is suggested that these are birds from Russia and north Turkey. Common Buzzards also occur on Cyprus in autumn, but their point of origin is not clear. Short-toed Eagles Circuetus gullicus and vultures join the migration from their breeding grounds in Turkey and the Levant.
Different species tend to migrate at different times of year. White Storks, Egyptian Vultures Neophron percnopterus and Black Kites Milvus migruns move chiefly between late August and mid-September, while eagles Aquilu spp. start in late September and continue until November. Other species are intermediate, or spread their migration out over a longer period.
The volume of migration at different times of day is discussed. No general conclusions are possible but in 1964 a correlation was obtained between cloud cover and the start of the migration.     

Spatio-temporal distribution of migrating raptors: a comparison of ringing and satellite tracking

We describe the migration performance of three long-distance migrating raptors, osprey Pandion haliaetus , honey buzzard Pernis apivorus and marsh harrier Circus aeruginosus , and one short-distance migrating raptor, common buzzard Buteo buteo based on Swedish ringing recoveries and satellite telemetry, respectively. Tracking by satellite can provide detailed information about the exact timing of migration, migration speed, migration directions, stopover sites, and detours, thereby overcoming many of the potential biases found in ring recoveries. Comparison of the results from these two methods revealed agreement in the geographical distribution of the studied Swedish raptor populations during autumn migration and the winter period. Satellite tracking, nevertheless, provided much more detailed information in Africa and revealed significantly faster migration progress than indicated by ring recoveries. The implications of our findings for interpretation of migratory connectivity and the understanding of migration are discussed.     

Structure of allozyme variation in Nordic Silene nutans (Caryophyllaceae): population size, geographical position and immigration history

We investigated allozyme variation in 34 populations of the perennial herb Silene nutans from Sweden and northern Finland, areas that were ice-covered during the last (Weichselian) glaciation. The present geographical structure of genetic variation in S. nutans in Sweden and northern Finland appears to have been mainly shaped by ancient historical processes. Patterns of variation in allele frequencies suggest two major postglacial immigration routes into Sweden, with populations entering the area from both the south and the east and forming a contact zone with admixed populations in central Sweden. While estimates of within-population genetic diversity and allelic richness are significantly correlated with present population size and geographical position (latitude), population size is not correlated with latitude. Low genetic diversity in the northern populations is more likely to have resulted from ancient stochastic events during the process of immigration than from recent population fragmentation. F _IS values are high and increase with latitude. Evidence of recent bottlenecks was detected in several southern Swedish populations: these can be interpreted in terms of population fragmentation as a result of anthropogenic disturbance. Soil pH is uncorrelated with population size and position.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society, 2004, 81 , 357–371.     

Genetic estimates of annual reproductive success in male brown bears: the effects of body size, age, internal relatedness and population density

1. We studied male yearly reproductive success (YRS) and its determinants (phenotypic characteristics, age, population density) in two Scandinavian brown bear populations, using molecular techniques to determine paternity. 2. We found a significant difference in male YRS between the study areas, with lower YRS in the south than in the north. 3. In general, older and larger males had higher YRS. Older males may be more experienced in competition for reproduction (male dominance). Large body size is of direct benefit in male-male competition and of advantage in endurance competition for the access to females. 4. Age was relatively more important for YRS in the north and body size was more important in the south, due perhaps to differences in male age structure due to illegal killing. A single old male dominated the reproduction in the north during the study, which resulted most probably in the relatively higher importance of age in the north. In the south, with a more even male age structure, no single male was able to dominate, probably resulting in a more intense competition among males, with body size as the deciding factor. 5. Male YRS was correlated positively with population density. This may be related to the structure of the expanding bear population, with female densities declining towards the population edge. 6. Internal relatedness, a measure of genetic heterozygosity, was correlated negatively with YRS, suggesting that outbred individuals have a higher YRS. Individual heterozygosity at key or many loci may reflect male physical qualities and condition-sensitive traits, which may benefit males directly in contest or in sperm competition.     

The influence of landscape structure on occurrence, abundance and genetic diversity of the common frog, Rana temporaria

Human‐caused habitat destruction and modification constitute one of the largest threats to population persistence and biodiversity, and are also suspected to be the major cause behind the global decline of amphibian populations. We assessed the potential role of agriculture‐related habitat fragmentation on population size and genetic variability in the common frog (Rana temporaria) by recording the occurrence, population density and genetic diversity in three geographically disparate regions in Sweden – each containing landscapes of high and low agricultural activity – and related these to landscape variables extracted from digital maps. We found a highly significant region‐by‐landscape interaction in occurrence, population density and genetic diversity revealing a reversed response to agriculture from south to north: while the effects of agriculture on R. temporaria populations were negative in the south, there were no effects in the central region, whereas positive effects were observed in the north. Spatial autocorrelation analyses of genetic data revealed that populations in high agricultural activity areas were more isolated than populations in low activity areas both in the southern and central regions of Sweden. Landscape diversity showed a strong positive correlation with both density and occurrence of frogs in Sweden as a whole, as well as in the southern region. Also, negative effects of roads and positive effects of ditches on genetic diversity were found in the south. Overall, these results suggest clear but regionally opposite effects of habitat structure on the population size and genetic diversity of amphibian populations. This means that the management strategy aiming to maximize the size and genetic diversity of local common frog populations, and perhaps also those of other amphibian populations, should account for regional differences in existing land‐use patterns.     

Contributions to the life-cycle of Frenkelia. III. The sexual development of F. clethrionomyobuteonis in the buzzard (author's transl)]

8 buzzards (Buteo buteo) were infected orally with cysts of Frenkelia clethrionomyobuteonis of the bank vole (Clethrionomys glareolus). Their intestines were searched for developmental stages of Frenkelia 21 and 24 h and 2, 3, 4, and 5 days post infection. After 21 and 24 h male and female gamonts could be detected within epithelial cells of the villi of the first half of the small intestine. The microgamonts contained 10-14 microgametes. The macrogamonts which measured on an average 11,1 X 9,8 mum in Giemsa stained smears developed into very thin-walled oocysts measuring in fresh preparations on an average 15,8 X 11,7 mum on day 3 after infection. The oocysts were located between the lamina propria and the epithelial lining of the distal third of the villi. They began to sporulate on day 5 and the first sporocysts were excreted 7 and 8 days post infection. Schizonts and schizont-like stages could not be observed in the developmental cycle in Buteo buteo.     

Microsatellite investigation of roe deer (Capreolus capreolus) in Scandinavia reveals genetic differentiation of a Baltic Sea Island population

After a decline in the early 19th century, a remnant population of the Scandinavian roe deer (Capreolus capreolus) was protected in southern Sweden around 1840. The roe deer quickly recovered and recolonized most of the Scandinavian Peninsula. In this study, I analyze microsatellite variation in 14 roe deer populations in Scandinavia to (1) investigate if all Swedish roe deer trace their ancestry to southern Sweden, (2) define other areas where roe deer may have remained during the population decline, and (3) examine if the large geographic distances during the expansion phase have influenced the degree and sorting of genetic variation. The results show that the mainland roe deer most likely trace their ancestry to southern Sweden, but interestingly, the two neighboring populations Övedskloster and Wittskövle in the south are significantly different from each other (p<0.01). Furthermore, the population in Wittskövle and roe deer from Köpingsvik at the Baltic Sea Island Öland are significantly different from all other populations (p<0.1). Thus, potentially, there are more than one founder population that contributed to the current Swedish population. The particular differentiation of roe deer from Öland might be an effect of random population genetic processes during the population expansion phase, potentially in combination with introductions of roe deer from other areas than the Swedish mainland. The results are discussed in relation to management of roe deer in Sweden.     

SPRING MIGRATION OF EIDERS SOMATERZA MOLLISSIMA IN SOUTHERN SCANDINAVIA

Eider migration in southern Scandinavia in spring 1972 was studied simultaneously at three radar stations and ten field observation sites. The Eiders winter in Danish and West German waters, from which they set out on spring migration on courses ranging from SE to NE; those from the northern part of the wintering area flew SE, those from the south NE, while birds wintering in between these geographical extremes set out on intermediate courses around E. Radar showed that most Eiders fly over the island of Zealand and the peninsula of Skåne, but only exceptionally further north over Sweden. Few Eiders crossing land were registered by field observers and most evidently passed at high altitudes beyond the range of vision. After having crossed Skåne, on varying tracks both south and north of east, the Eiders descended and changed flight direction towards NE. Some Eiders from the northern part of the wintering area circumnavigated Skåne, passing south along the Swedish coast of the Sound, crossing the very narrow peninsula of Falsterbo, and subsequently following the south coast of Skåne eastwards. Eiders from southern Denmark and Germany were often deflected eastwards along the south coast. After having passed Skåne no significant land crossings were made. Upon reaching the province of Blekinge on a course towards NE, the Eiders were deflected E to ESE along the coast and later NNE along the west coast of Öland through Kalmar sound. Approximately 350 000 ducks migrated during daytime of the study period, 250 000 crossing the land of Skåne while 100 000 passed along the south coast. Almost 300 000 migrated north in Kalmar sound, and 17 % of all Eiders passed east of Gland over the open sea. Three distinct peaks of activity during the day were noted in Skåne. The first, at around sunrise, originated from birds resting in waters off Skåne. The second occurred about four hours later and probably consisted of birds which had departed from the wintering area in the early morning. A final peak at sunset was often recorded. Migration also took place during the night, but involved only one fifth of the total number. From combined radar and field counts the total Baltic Eider population is estimated to have been 700 000–800 000 in spring 1972, indicating about 300 000 breeding pairs in the Baltic Sea.     

Biogeographic variation in skull morphology across the Kra Isthmus in dusky leaf monkeys

Despite the growing literature on the underlying factors of geographical phenotypic variation, little is known about how and to what extent biogeographic barriers in South‐East Asia have shaped morphological variation in primates. We aimed to investigate the geographical variations in skull morphology in dusky leaf monkeys by decomposing them into clinal (latitudinal), non‐clinal spatial (discrete difference between regions north and south of the Isthmus of Kra), and environment‐related components. We applied geometric morphometrics to measure 53 adult male specimens from 36 localities, covering the regions both north and south of the Isthmus of Kra. A linear model was used to test the effects of region (north vs. south of the Isthmus of Kra), latitude, and environmental factors (temperature and rainfall) on the size and shape of skulls. A part of variation in skull shape differed moderately between the regions in the north and south of the Isthmus of Kra, and this difference cannot be explained by latitudinal and environmental factors. However, for size and the majority of variations in shape, we detected limited contributions of region and the two environmental factors. Shape differentiation that was unexplained by latitudinal and environmental factors suggests that dusky leaf monkeys may have experienced a population division due to habitat constriction around the Isthmus of Kra. However, this divergence probably has been obscured by subsequent gene flow between populations after habitat recovery.     

The influence of wind on spiral grain formation in conifer trees

The correlation between spiral grain formation and crown asymmetry was investigated in 18 Scots pine (Pinus sylvestris L.) and 17 Norway spruce [Picea abies (L.) Karst.] trees selected from clones of each species growing in the south of Sweden. The angle between the longitudinal direction of the tracheids in the outermost year ring compared to the longitudinal direction of the stem was measured by scribing lines which followed the direction of the tracheids. The crown asymmetry was measured by taking photographs of the trees followed by a simple picture analysis of the tree. Wind data for the growing seasons of 1997 and 1998 were obtained from the Swedish Meteorological and Hydrological Institute. The results showed a significant correlation between the angle of the tracheids compared to the stem longitudinal direction going from a left-handed angle if the trees had a crown projected to the north towards a right-handed angle the more the crown projects to the south. Received: 6 September 1999 / Accepted: 20 January 2000     

The complete sequence of the mitochondrial genome of Buteo buteo (Aves, Accipitridae) indicates an early split in the phylogeny of raptors

The complete sequence of the mitochondrial (mt) genome of Buteo buteo was determined. Its gene content and nucleotide composition are typical for avian genomes. Due to expanded noncoding sequences, Buteo possesses the longest mt genome sequenced so far (18,674 bp). The gene order comprising the control region and neighboring genes is identical to that of Falco peregrinus, suggesting that the corresponding rearrangement occurred before the falconid/accipitrid split. Phylogenetic analyses performed with the mt sequence of Buteo and nine other mt genomes suggest that for investigations at higher taxonomic levels (e.g., avian orders), concatenated rRNA and tRNA gene sequences are more informative than protein gene sequences with respect to resolution and bootstrap support. Phylogenetic analyses indicate an early split between Accipitridae and Falconidae, which, according to molecular dating of other avian divergence times, can be assumed to have taken place in the late Cretaceous 65-83 MYA.     

Inference of hazel grouse population structure using multilocus data: a landscape genetic approach

In conservation and management of species it is important to make inferences about gene flow, dispersal and population structure. In this study, we used 613 georeferenced tissue samples from hazel grouse (Bonasa bonasia) where each individual was genotyped at 12 microsatellite loci to make inference on population genetic structure, gene flow and dispersal in northern Sweden. Observed levels of genetic diversity suggest that Swedish hazel grouse do not suffer loss of genetic diversity compared with other grouse species. We found significant F(IS) (deviation from Hardy-Weinberg expectations) over the entire sample using jack-knifed estimators over loci, which is most likely explained by a Wahlund effect. With the use of spatial autocorrelation methods, we detected significant isolation by distance among individuals. Neighbourhood size was estimated in the order of 62-158 individuals corresponding to a dispersal distance of 950-1500 m. Using a spatial statistical model for landscape genetics to infer the number of populations and the spatial location of genetic discontinuities between these populations we found indications that Swedish hazel grouse are divided into a northern and a southern population. We could not find a sharp border between these two populations and none of the observed borders appeared to coincide with any potential geographical barriers.These results imply that gene flow appears somewhat unrestricted in the boreal taiga forests of northern Sweden and that the two populations of hazel grouse in Sweden may be explained by the post-glacial reinvasion history of the Scandinavian Peninsula.     

Multiple origins of stone loach,Barbatula barbatula (Teleostei: Nemacheilidae), in Sweden based on mitochondrial DNA

Stone loach, Barbatula barbatula, occurs in scattered localities in Sweden. Some of the populations have usually been considered as feral descendants of escaped 18th Century pond stock, but historical documentation is inconclusive. Using the mitochondrial COI gene as a marker, we analyzed specimens from seven Swedish localities. One of the middle Swedish localities, in Stockholm, belongs to a haplotype found also in Poland and Lithuania. Two other samples, from near Nyköping and Lake Hjälmaren, belong to a haplotype found in northeastern Europe (Finland, Estonia, Latvia, Volga basin in Russia). Those two Swedish populations are probably descendants from at least two introductions, probably for pond rearing for human consumption. Samples from Skåne and Halland in southern Sweden belong to the haplotype found in Denmark, northern Germany and Poland; and whereas it remains possible that they also represent feral populations, they may be naturally occurring, having reached Sweden during the Ancylus period, about 8,000–10,000 years ago. A recently discovered population from the central South Swedish Highlands belongs to a mainly southeastern European haplotype. It probably represents a release of imported aquarium specimens or live bait carried by sport fishing tourists.