Microsatellite loci for the Siberian flying squirrel,Pteromys volans

We report the isolation and characterization of polymorphic microsatellite loci for the Siberian flying squirrel Pteromys volans. The seven most useful loci had between six and 11 alleles and expected heterozygosities ranging from 0.477 to 0.866. We also tested the utility of these loci in other squirrel species, northern flying squirrels (Glaucomys sabrinus and G. volans) and the common red squirrel (Sciurus vulgaris). Three of the Siberian flying squirrel loci were polymorphic in other squirrel species, suggesting a limited potential for cross‐species use.     

Contrasting seasonal dynamics in fleas of the Siberian flying squirrel (Pteromys volans) in Finland

Abstract.  1. The seasonal and spatial variation of the adult flea fauna (Siphonaptera) was examined in connection with live-trapping studies of the Siberian flying squirrel ( Pteromys volans ) in three study areas in southern Finland between 1997 and 2005.
2. The numerically dominant flea species of the Siberian flying squirrel were Tarsopsylla octodecimdentata octodecimdentata and Ceratophyllus (Monopsyllus) indages indages (Ceratophyllidae); the latter being a host specialist of the Siberian flying squirrel. Tarsopsylla octodecimdentata , which also commonly occurs on the red squirrel ( Sciurus vulgaris ), infected a large proportion of the host population throughout the winter, whereas C. indages occurred predominantly during the summer and autumn, being practically the only flea species in nests during the flying squirrels' breeding season and on juveniles still inhabiting their natal nest.
3. The use of nest boxes by flying squirrels did not have any positive effects on flea populations, but it may have had a negative impact on T.   octodecimdentata .
4. The potentially vulnerable C.   i.   indages is a predictable, widespread component in the flea fauna of the Siberian flying squirrel at various spatial scales, and it is likely to occur in most of the permanent flying squirrel populations in Finland.     

Temporal patch occupancy dynamics of the Siberian flying squirrel in a boreal forest landscape

Ability to predict species distribution in a landscape is of crucial importance for natural resource management and species conservation. Therefore, the understanding of species habitat requirements and spatio-temporal dynamics in occurrence is needed. We examined patch occupancy patterns of the Siberian flying squirrel Pteromys volans in northern Finland across a seven year study period. Forest patches dominated by mature spruce ( Picea abies ) in a study area (375 km²) were surveyed to monitor the presence or absence of the flying squirrel. The patch occupancy pattern was dynamic: about half of the habitat patches were occupied at least once during the study period and more patches were colonised than were abandoned. Patches that were continuously occupied (i.e. occupied during all sample periods) were typically of high quality (based on habitat and landscape characteristics), continuously unoccupied patches were usually of low quality, and intermediate quality patches were occupied intermittently. The variables explaining patch occupancy were similar each year, and a statistical model based on data from the year 2000 also predicted occupancy in 2004 with similar accuracy. However, data from a single survey were inadequate for identifying patches used intermittently by flying squirrels. Despite inconsistent occupancy, these patches may be important for the local persistence of flying squirrels. The dynamic occupancy pattern may thus affect estimates of suitable habitat area and identification of functional patch networks for landscape planning. These results emphasise the need for follow-up studies to better understand population patterns and processes in time.     

Natal habitat-biased dispersal in the Siberian flying squirrel

Theoretically, dispersers should target the habitat where prospects for fitness will be highest. Aiming for a habitat similar to the natal area (natal habitat-biased dispersal) has been hypothesized as a probable rule of thumb for dispersers, but has received very little empirical support to date. We investigated similarities between natal and post-dispersal settlement sites with radio-collared Siberian flying squirrels (Pteromys volans L.). Juveniles born in small patches and raised in nests close to patch edge settled in small patches and used nests close to edges after dispersal. In addition, post-dispersal use of dreys (versus cavities) was similar to that observed in natal sites. However, the quality of settlement habitat was unrelated to the quality of the natal site, which suggests that natal experience on average-quality habitats may not lead to ecological traps for flying squirrels. This study provides evidence that habitat selection at the landscape scale is influenced by habitat of natal area.     

Female-biased natal dispersal in the Siberian flying squirrel

Natal dispersal is usually sex biased in birds and mammals.Female-biased natal dispersal is the prevailing pattern in birdsbut is rare among mammals. Hypotheses explaining sex bias indispersal include the mate-defense mating hypothesis, whichpredicts male-biased dispersal, the resource-defense hypothesispredicting female-biased dispersal, and the competition hypothesis,which predicts that if dispersal is caused by competition forresources between sexes, then the subdominant sex will disperse.We studied natal dispersal of Siberian flying squirrels Pteromysvolans using radio telemetry in Southern Finland in 1996–2004.Of 86 juveniles that survived over the dispersal period, almostall young females dispersed from the natal site, whereas almost40% of males were philopatric. Dispersal was farther for femalesthan males. Females began dispersal on average 2 weeks earlierthan males and were lighter in mass at the onset of dispersalthan later dispersing males. No mate- or resource-defense matingsystem could be found among males, but females seemed to defendnest and apparently food resources, in contrast to the expectationof dispersal bias in resource-defense systems. Competition forresources between sexes does not explain female bias either:in the flying squirrel, the female seems to be the dominantsex. We propose that young females are subordinate to theirmothers and have to disperse to find a vacant, suitable sitefor reproduction.     

Movements of the flying squirrel Pteromys volans in corridors and in matrix habitat

Elements of the landscape, such as patches of preferred habitat, matrix between patches, and corridors linking patches, differ as movement habitat for animals. To understand how landscape structure influences the movement and thus, population dynamics of animals, clear empirical knowledge on patterns of movement is needed. The Siberian flying squirrel inhabits spruce-dominated boreal forests from Finland to eastern Siberia. Numbers of flying squirrels have declined severely in Finland in past decades, probably due to modern forestry. We studied the movement of radio-collared adult flying squirrels in preferred (spruce forest) and in matrix habitat (open areas and other habitats with trees) in Finland 1997–2000, and determined whether the woodland strips connecting patches of preferred habitat could function as ecological corridors for flying squirrels.
Flying squirrels used woodland strips for inter-patch movements, but also used matrix with trees and were able to cross narrow open gaps. Males moved longer total distances and crossed edges more often than females. Males used matrix habitats for movement between spruce patches, and moved faster and more directly in the matrix than in the spruce forest. Females seldom changed spruce patches, but instead used the matrix for foraging. For both sexes probability of leaving the spruce forest patch correlated negatively with the size of the patch, but the type of connection the patch had to other patches did not affect the leaving probability. Due to efficient movement abilities of the flying squirrel and forest-dominated landscape structure of southern Finland, we suggest that conservation acts for maintaining viable populations of flying squirrels should focus on the quality of managed forest and the area of suitable breeding habitat (i.e. on habitat loss), but not necessarily on ecological corridors.     

Young flying squirrels (Pteromys volans) dispersing in fragmented forests

Dispersal is a key determinant of the population dynamics ofspecies. Thus, a better understanding of how dispersal is affectedby the landscape structure and how animals make decisions aboutmoving across different landscapes is needed. We studied thedispersal of 60 radio-collared juvenile Siberian flying squirrels(Pteromys volans) in southern Finland. The effect of landscapestructure on selected dispersal direction, dispersal distance,and straightness of dispersal path was studied. Flying squirrelswere capable of dispersing over long distances in fragmentedforest landscapes. The patches used as temporary roosting sitesduring dispersal were of a lower quality than were those usedas finally occupied patches. The patches used were larger thanwere patches on average in the study areas. There was a veryclear directional bias in the dispersal path (i.e., it was nearlya straight line), which remained over a large scale, but wide-openareas obstructed the straightness of the path. As the distancesbetween crossed patches increased, short-distance disperserswere found further away from their natal home range. However,there were no differences in the landscape that could explainthe differences between individuals in decisions to remain philopatricor to become short- or long-distance dispersers. In addition,whereas short-distance dispersers dispersed in random directions,long-distance dispersers started to disperse in directions dominatedby preferred habitat. Thus, there were behavioral differencesbetween dispersers. Our results supported the hypotheses statingthat individuals decide to disperse long or short distancesbefore the onset of dispersal.     

Predictors of long-distance dispersal in the Siberian flying squirrel

During dispersal the distances moved differ between individuals. The evolutionary causes of dispersal rate are much studied, for example, it is observed that dispersal is often a condition- and phenotype-dependent strategy. However, more empirical information is needed on factors affecting the dispersal distance. We study factors behind dispersal distance in the juvenile Siberian flying squirrel. The longer dispersing individuals abandoned natal site earlier in the season and were larger, perhaps being born earlier, than shorter dispersing individuals. These patterns did not hold between same-sex siblings, indicating that the early long-distance dispersal was more a between than a within-litter related phenomenon. Our results indicate differences between litters that are related to dispersal strategies of individuals. In flying squirrels, long-distance dispersal is not merely a secondary effect of short-distance dispersal. Instead, the distribution of dispersal distance is affected by factors enhancing long-distance dispersal.     

Local habitat patch pattern of the Siberian flying squirrel in a managed boreal forest landscape

We examined how the structure of a boreal forest landscape is related to the occurrence of the Siberian flying squirrel Pteromys volans in northern Finland. The flying squirrel inhabits mature spruce-dominated ( Picea abies ) mixed forests and is categorised as vulnerable species due to habitat loss and change. We classified a landscape of 374.5 km² into potential habitat patches, potential dispersal areas, and areas incapable of being inhabited using national forest inventory data, and surveyed all 136 potential habitat patches for the presence of the species. Different landscape variables were defined, and also connections by the shortest distances to neighbouring habitat patches along both straight lines and least-cost distances based on specific movement costs were measured. Occupied patches were larger in size, contained more deciduous trees for food and nesting cavities, and were in closer proximity to the nearest occupied patches. Occupied patches were mainly located below 300 m a.s.l. The occurrence of flying squirrels was correctly predicted for 88% of the habitat patches using landscape variables. This modelling result proved to be rather general. In addition, the configuration of occupied patches was mainly clustered across the landscape, and distant occupied patches seemed to be linked to other patches via forested connections. We suggest that maintaining a clustered arrangement of good quality habitat patches and regenerating new potential habitat as well as dispersal areas between the habitat patches seem to be appropriate goals for long-term forest management planning to sustain populations of the flying squirrel in the landscape.     

Immigration ensures population survival in the Siberian flying squirrel

Linking dispersal to population growth remains a challenging task and is a major knowledge gap, for example, for conservation management. We studied relative roles of different demographic rates behind population growth in Siberian flying squirrels in two nest‐box breeding populations in western Finland. Adults and offspring were captured and individually identifiable. We constructed an integrated population model, which estimated all relevant annual demographic rates (birth, local [apparent] survival, and immigration) as well as population growth rates. One population (studied 2002–2014) fluctuated around a steady‐state equilibrium, whereas the other (studied 1995–2014) showed a numerical decline. Immigration was the demographic rate which showed clear correlations to annual population growth rates in both populations. Population growth rate was density dependent in both populations. None of the demographic rates nor the population growth rate correlated across the two study populations, despite their proximity suggesting that factors regulating the dynamics are determined locally. We conclude that flying squirrels may persist in a network of uncoupled subpopulations, where movement between subpopulations is of critical importance. Our study supports the view that dispersal has the key role in population survival of a small forest rodent.     

黑龙江省张广才岭北部小飞鼠的遗传多样性与种群历史动态

小飞鼠 (Pteromys volans) 为树栖夜行滑行类啮齿动物,在森林种子传播和维持生态系统平衡等方面发挥着重要的生态学作用。本研究利用mtDNA Cytb、控制区和nDNA微卫星3种分子标记,对黑龙江省张广才岭北部的小飞鼠种群进行遗传多样性与历史动态分析。检测出Cytb全序列 (1 140 bp) 的平均单倍型多样性为0.909,平均核苷酸多样性为0.616%;控制区全序列 (1 066 bp) 的平均单倍型多样性为0.945,平均核苷酸多样性为1.698%;微卫星检测出种群平均等位基因数13.167个,观测杂合度0.727,期望杂合度0.864,近交系数0.159。结果表明,小飞鼠种群遗传多样性丰富,但存在一定程度的杂合度不足和近亲繁殖;未检测到种群近期遗传瓶颈效应,种群内无遗传分化。高比例的稀有单倍型 (≥ 60%) 、低频率等位基因与近亲繁殖,提示未来种群面临遗传多样性下降的风险,建议加大对该物种的关注和保护力度。基于Cyt b基因的系统进化关系结果表明,小飞鼠存在3个明显的遗传谱系：远东、欧亚大陆北部和日本北海道,本研究中张广才岭和大兴安岭的样本单倍型归属为远东谱系。     

Multilevel landscape utilization of the Siberian flying squirrel: Scale effects on species habitat use

Animals use and select habitat at multiple hierarchical levels and at different spatial scales within each level. Still, there is little knowledge on the scale effects at different spatial levels of species occupancy patterns. The objective of this study was to examine nonlinear effects and optimal‐scale landscape characteristics that affect occupancy of the Siberian flying squirrel, Pteromys volans, in South‐ and Mid‐Finland. We used presence–absence data (n = 10,032 plots of 9 ha) and novel approach to separate the effects on site‐, landscape‐, and regional‐level occupancy patterns. Our main results were: landscape variables predicted the placement of population patches at least twice as well as they predicted the occupancy of particular sites; the clear optimal value of preferred habitat cover for species landscape‐level abundance is a surprisingly low value (10% within a 4 km buffer); landscape metrics exert different effects on species occupancy and abundance in high versus low population density regions of our study area. We conclude that knowledge of regional variation in landscape utilization will be essential for successful conservation of the species. The results also support the view that large‐scale landscape variables have high predictive power in explaining species abundance. Our study demonstrates the complex response of species occurrence at different levels of population configuration on landscape structure. The study also highlights the need for data in large spatial scale to increase the precision of biodiversity mapping and prediction of future trends.     

Characterization of microsatellite DNA loci for the southern flying squirrel (Glaucomys volans)

Polymerase chain reaction primers for microsatellite DNA loci (one dinucleotide, four tetranucleotide and two compound) and the conditions necessary to amplify each are described for the southern flying squirrel (Glaucomys volans). These primers were tested on 22 or more individuals from a population at the Savannah River Site in South Carolina. These microsatellite primers yielded a high allelic diversity (6–22 alleles/locus), and moderate to high observed heterozygosities (0.318–0.826). Primers developed for the northern flying squirrel (Glaucomys sabrinus) were also tested for use on G. volans, with only two successful cross amplifications from the seven loci.     

Site occupancy and cavity use by the northern flying squirrel in the boreal forest

Tree cavities are used as shelter and breeding nests by numerous avian and mammalian species. In cold environments, tree cavities are often proposed as the best winter nest choice because of the superior protection they offer from precipitation, wind, cold temperatures, and predators. As such, they represent a critical resource, which has the potential to limit population size of non-excavating species. We assessed factors affecting site occupancy in the boreal forest by northern flying squirrels, a secondary user of tree cavities, and to identify which nest type is preferred during the colder days of the autumn–winter period. We trapped flying squirrels twice in 59 aspen-dominated stands in the autumn period using low- (1.5 m above ground-level) and high-mounted (4 m) traps to determine site occupancy. A total of 85 individuals were captured on 2,880 trap-nights. During the winter period, we radio-tracked 26 individuals to 87 diurnal nests in 220 locations. None of the habitat variables considered (cavity availability, woody debris, and lateral cover) explained site occupancy. Detectability decreased with precipitation, and was lower using high traps than low traps. Both females and males used tree cavities (26%), external nests (39%), and ground nests (35%). In cold weather, females preferred ground nests, whereas males preferred external nests. Our results do not support the hypothesis that tree cavities represent a limiting factor to northern flying squirrels in cold environments. Instead, this species seems to be a generalist and is opportunistic, using a variety of nest types. Nevertheless, practices ensuring the persistence of large diameter live cavity trees, providing better insulative properties, are likely to increase the relative use of tree cavities as nest sites by northern flying squirrels. © 2011 The Wildlife Society.     

Understanding flying insect dispersion: Multiscale analyses of fragmented landscapes

A multiscale model was developed to simulate the rate of landing of a winged insect, the grain aphid, Sitobion avenae F. At a large scale (kilometric scale), it is convenient to use a deterministic model of their dispersion, based upon diffusion–advection–reaction partial derivative equations. At a small scale (hectometric scale), the process of site selection (‘landing’) is only partially understood, but is known to include the perception of field colour and landscape characteristics. Several hypotheses on aphids' behaviour were tested to simulate the rate of landing: the simulation was done by a cellular automata submodel under five different hypotheses on the precise organisation of the landing behaviour. We found a strong interaction between the effect of the proportion of wheat crops in the landscape and their spatial organisation. The spatial correlation between the places occupied by wheat crops appears crucial to determine the global rate of landing of the aerial insect stock. The shape of the response surface of landing rate against the proportion of surface occupied by wheat, and the spatial autocorrelation of wheat plots, appears very regular and relatively simple to model by ad hoc mathematical functions. Large scale simulations using the results of the small scale model in a diffusion–reaction equation solved numerically, showed that, on a real landscape extracted from a GIS on the whole Brittany region (western France), the spatial pattern of the aphid landing is sensitive to the hypothesis tested on their landing behaviour. This hierarchical modelling combining two different approaches at two different scales (mathematical deterministic equations on a large multi-kilometric scale, and partly stochastic cellular automata on a small hectometric scale), requires methods to validate its results in the field, in the framework of a decision support system. Such a multiscale model has a wide field of application including not only plant protection but also management and conservancy of animal species dispersing by flight.     

Landscape characteristics associated with the occurrence of the flying squirrel Pteromys volans in old-growth forests of northern Finland

We investigated whether the occurrence of the flying squirrel, a declined virgin forest species, was accounted for by the structure of the landscape in northeastern Finland We sampled 20 forest areas (1–77 km² in size) in 1995 for the occurrence of the species using a sampling plot method Landscape structure around occupied and unoccupied areas were compared using seven different radii ranging from 100 m lo 10 km Classified satellite images were analyzed with Geographic Information System (GIS) Ten areas could be determined to be occupied by the flying squirrel Results showed that occupied areas did not deviate from unoccupied ones in total area In unoccupied areas there were more mature pine-spruce forests, and less matrix habitat at the home range scale (100 m and 200 m radii) than in occupied areas Further more, in unoccupied forest areas open habitats (clear-cuts, open fens) were more common than in occupied ones at distances between 200 m and 2 km around sampling plots These differences resulted from both larger mean patch size of and smaller mean nearest neighbor distance between open habitat patches m unoccupied than in occupied forest areas According to a logistic regression analysis, information on the amount of open habitat within 1 km radius alone correctly classified 75% of the areas into occupied and unoccupied ones The probability of the presence of flying squirrel decreases with the increasing amount of open habitat within 1 km The results suggest that increasing the amount of open habitats (e g clear-cutting) at the local scale has a negative impact on the flying squirrel It is obvious that in the present situation where the population has severely declined and its optimal habitat is still diminishing, every patch suitable for the species - whether occupied or not -may be important for the population persistence