Search

Birds often have to choose their nest site location along a food safety axis, balancing nest predation danger with the food requirements of themselves and their offspring. This is probably most important for precocial species, such as most shorebirds, in which both chicks and parents need access to food resources in the surroundings of the nest, at least during the first days of life of the chicks. In many Arctic ecosystems, shorebird nests are typically prone to predation by both avian and terrestrial predators, especially in lemming-poor years. Among other factors, the strength of the trophic interactions between shorebirds, their prey, and their predators depend on how all of these are distributed across space. During two breeding seasons in northern Taimyr, North-Central Russia, we investigated how the spatial distribution of red knot Calidris canutus and little stint Calidris minuta nests and broods overlaps with the local food landscape and also with the distribution of avian predators and their main prey, lemmings. We found that the two shorebird species use different habitats that vary in arthropod community structure in accordance with the birds' diet: while little stints selected lower elevations where chironomid midges Chironomidae are more abundant, red knots selected higher elevations where crane flies Tipulidae are more abundant. Furthermore, little stints share low-elevation habitats with lemmings and predators, while red knots inhabit higher elevations averted by both lemmings and avian predators. We found higher nest predation for little stint nests than for red knots nests, especially in a low-lemming year. Our results thus support the idea that food web interactions are driven by landscape and community aspects. [ABSTRACT FROM AUTHOR]

Prey handling processes are considered a dominant mechanism leading to short‐term positive indirect effects between prey that share a predator. However, a growing body of research indicates that predators are not necessarily limited by such processes in the wild. Density‐dependent changes in predator foraging behavior can also generate positive indirect effects but they are rarely included as explicit functions of prey densities in functional response models. With the aim of untangling proximate mechanisms of species interactions in natural communities and improving our ability to quantify interaction strength, we extended the multi‐prey version of the Holling disk equation by including density‐dependent changes in predator foraging behavior. Our model, based on species traits and behavior, was inspired by the vertebrate community of the arctic tundra, where the main predator (the arctic fox) is an active forager feeding primarily on cyclic small rodent (lemming) and eggs of various tundra‐nesting bird species. Short‐term positive indirect effects of lemmings on birds have been documented over the circumpolar Arctic but the underlying mechanisms remain poorly understood. We used a unique data set, containing high‐frequency GPS tracking, accelerometer, behavioral, and experimental data to parameterize the multi‐prey model, and a 15‐year time series of prey densities and bird nesting success to evaluate interaction strength between species. We found that (1) prey handling processes play a minor role in our system and (2) changes in arctic fox daily activity budget and distance traveled can partly explain the predation release on birds observed during lemming peaks. These adjustments in predator foraging behavior with respect to the main prey density thus appear as the dominant mechanism leading to positive indirect effects commonly reported among arctic tundra prey. Density‐dependent changes in functional response components have been little studied in natural vertebrate communities and deserve more attention to improve our ability to quantify the strength of species interactions. [ABSTRACT FROM AUTHOR]

Most small rodent populations in the world have fascinating population dynamics. In the northern hemisphere, voles and lemmings tend to show population cycles with regular fluctuations in numbers. In the southern hemisphere, small rodents tend to have large amplitude outbreaks with less regular intervals. In the light of vast research and debate over almost a century, we here discuss the driving forces of these different rodent population dynamics. We highlight ten questions directly related to the various characteristics of relevant populations and ecosystems that still need to be answered. This overview is not intended as a complete list of questions but rather focuses on the most important issues that are essential for understanding the generality of small rodent population dynamics. [ABSTRACT FROM AUTHOR]

The vocal repertoire of steppe (Lagurus lagurus Pallas, 1773) and yellow steppe (Eolagurus luteus Eversmann, 1840) lemmings consists of only one type of signal, namely, a squeak. The signal does, however, have considerable variability. The DFA standard procedure shows the significant differences in the parameters of squeaks between species and significant differences in squeak parameters between the sexes in steppe lemming but not in the yellow steppe lemming. The fundamental frequency of the smaller steppe lemming’s squeak is higher than that of the larger yellow steppe lemming, although the peak frequencies have comparable values. In addition, the steppe lemming displays a pronounced sexual dimorphism in vocalization parameters; the frequency characteristics of the signals of the smaller females have lower values, which are contrary to scaling laws, stating that smaller individuals tend to have higher fundamental and peak frequencies. The age-related variability in the signals of yellow steppe lemmings was also described. The fundamental frequency of their squeaks is higher than that of the adults, but the peak frequency of signals in young and adults is not distinguished, and its value is higher than theoretically calculated. Such deviation in signal frequency parameters from the optimum may be result of directed selection, indicating the high value of such signals in the acoustic communication of lemmings. [ABSTRACT FROM AUTHOR]

The effects of close breeding upon dental phenotype are analysed in three laboratory colonies of Dicrostonyx using traditional comparative methods and a previously developed approach to quantify dental complexity in Arvicolinae. Across ten to 12 generations, dental complexity fluctuates within the range of variability inherited from the colony founders and shows no shifts towards complication. The finite number of founders (ten or fewer) favours the accumulation of rare dental traits inherited from the founders and leads to the appearance of atavisms and phenotypic outliers with extremely simple patterns of dentition. The atavistic patterns on m1, M1 and M3 revealed in two colonies of Dicrostonyx torquatus recapitulate the traits of the Miocene species Microtocricetus molassicus, which has been regarded previously as an evolutionary dead end in Cricetidae. A comparison with other arvicoline lineages suggests that one of the atavisms shared by D. torquatus and Microtocricetus could also be found in Microtus and Lemmus as an extremely rare trait, thus raising a question regarding the close relatedness of Microtocricetus to the present-day Arvicolinae. A perspective on the practical application of rare dental traits to detect close-breeding events in natural populations, living and extinct, is considered and exemplified for a particular case of arvicoline rodents. [ABSTRACT FROM AUTHOR]

The materials on litho- and biostratigraphy (collared lemming, Dicrostonyx) of the Middle Neopleistocene of the northeast Russia were revised and litho- and biostratigraphic methods were mutually tested for determination of the age of geological bodies. The reasonable stratigraphic division and correlation of the Neopleistocene are especially topical because of the current preparation of a new common stratigraphic chart of Quaternary sediments. The petrographic composition of the coarse-clastic material and the orientation of clasts in moraines are regionally consistent lithostratigraphic criteria. In the Pechora (Dnieper) moraine, the elongated rock clasts are oriented in a sector of 20°-60° in contrast to an azimuth of 270°-360° of the Vychegda (Moscow) moraine, which, in addition to petrographic composition of rocks, indicates the contribution of terrigenous material from different glacial provenances during formation of moraines. Certain differences were revealed also in assemblages of heavy minerals. The Middle Neopleistocene rodent fauna was found between the Pechora and Vychegda moraines. The stratigraphic position of microtheriofauna is identified on the basis of evolution level of molars of collared lemmings. By proportion of simplicior and henseli morphotypes for M1 and M2, all fossils belong to three groups corresponding to three evolution stages of a tooth system: Late Pechora (Late Dnieper, MIS 8), Rodionovo (Shklov, MIS 7), and Early Vychegda (Early Moscow, MIS 6). They include D. simplicior morph 2 (Gavrilovka, Bol’shaya Sluda, Akis’, Laya-4 localities), D. simplicior morph 3 (Sercheiyu-1, Laya-3 localities), and D. ex gr. simplicior—gulielmi (Shapkina-4, Chuley, lower horizon of Kipievo localities) morphs. These evolution stages correspond to Late Pechora (Late Dnieper, MIS 8), Rodionovo (Shklov, MIS 7), and Early Vychegda (Early Moscow, MIS 6) intervals. Taking into account the paleoclimate data, the presence of the lemmings in the region during the Rodionovo time is rather plausible. [ABSTRACT FROM AUTHOR]

Microfaunal remains are commonly used as palaeoenvironmental proxies and have been proposed as a means to identify relative ages of Late Quaternary deposits through biostratigraphy (i.e., utilising ‘Mammal Assemblage Zones’). However, assemblages of faunal remains can include a diverse range of taxa which are often difficult to distinguish using morphological aspects of the surviving bones, particularly when diagnostic features are eroded or missing due to fragmentation. Here we investigate the application of a recently developed method of species identification by collagen fingerprinting to arvicoline rodents (voles and lemmings), the dominant mammalian taxonomic group present at the Late Pleistocene site of Pin Hole Cave, Creswell Crags U.K., which is currently the designated British type locality for the Pin Hole Mammal Assemblage Zone (Oxygen Isotope Stage 3) fauna. We also further explore the potential for studying collagen decay rate via deamidations, and their applicability across the species boundary, in terms of its use for relative ageing of remains. Our results demonstrate the ease with which some taxa can be objectively distinguished to genus (e.g. Microtus from Myodes and Lemmus from Dicrostonyx ) and in some cases species (e.g., M. gregalis from M. oeconomus ), but that the potential for relative ageing is complicated by a range of taphonomic factors. The results highlight the potential for this new technique in much larger-scale palaeoenvironmental studies investigating temporal changes in vertebrate biodiversity. [ABSTRACT FROM AUTHOR]

The Beringian Land Bridge is a well-documented dispersal corridor between the Eurasian continent and North America. Episodic sub-aerial exposure of the land bridge during the Late Cenozoic resulted from climatic oscillations and concomitant lowering of sea level. For much of the Pleistocene, dispersal was predominantly west-to-east (e.g., from Eurasia to North America), but a new discovery of the North American rodent Phenacomys from deeply buried sediments in The Netherlands documents an Early Pleistocene east-to-west invasion. The discovery reinforces earlier suggestive hints of an integrated Holarctic mammal fauna in the Early Pleistocene and provides a unique opportunity to establish a direct correlation of the classic mammal zonations of Europe and North America. Phenacomys is traditionally conceptualized as an endemic North American radiation of voles, and all extant taxa are exclusively North American. The first European remains of Phenacomys were recovered as part of the Zuurland Drilling Project from earliest Pleistocene (ca, 2.3–2.1 Ma) strata. The specimens were found in stratigraphic association with species that are well-known from more southern European assemblages of Early Pleistocene age, but also with contemporaneous taxa traditionally associated with more northern latitudes. The recognition of Phenacomys within the Zuurland assemblage demonstrates that the Bering Land Bridge served as a corridor for dispersal of mammal species during the earliest Pleistocene, and served as a physiographic mechanism for the integration of a circumpolar biogeographic province at that time. [ABSTRACT FROM AUTHOR]

Questions: We investigated the importance of climate and herbivory on native and alien conifer colonization of the birch-dominated Fennoscandian tree line by addressing the following questions: (a) are tree line and tundra habitats similarly suitable for conifer seedling recruitment; (b) do ungulate and rodent herbivores differentially impact seedling recruitment; and (c) how does the role of habitat and herbivory on seedling recruitment vary across a marked climate gradient? Location: Northern Fennoscandia, Sweden (Vassijaure and Paddus), and Norway (Joatka and Seiland). Methods: We conducted an experiment to assess the emergence rate, survival probability and height development of Norway spruce (Picea abies), Scots pine (Pinus sylvestris) and Siberian larch (Larix sibirica) seedlings. Three experimental plots (i.e., open control, reindeer exclosure and complete vertebrate exclosure) were established in both tree line and tundra habitats at each of the four locations. Seeds of the three conifer species were sown in each plot in June 1999 during three consecutive years. The surviving seedlings were counted in August to September 1999, 2000, 2001, 2002 and 2007. The height of all seedlings was measured in 2007. Results: Our study reveals that Norway spruce, Scots pine and Siberian larch can regenerate from seed at and above the current tree line in northern Fennoscandia. Their performance was generally higher above tree line in tundra than at tree line, but depended on species identity, climate aridity and mammal herbivory, particularly by rodents. These results suggest that the species composition and latitudinal limit of the tree line in the future might depend not only on direct effects of the future climate on the current tree line species, but also on the intensity of alien and native conifer introductions, as well as changes in herbivore populations. Conclusion: If sufficient seeds of Norway spruce, Scots pine and Siberian larch should reach the current tree line, their performances will increase with a warmer and wetter climate, and this effect will be markedly modulated by herbivores (particularly rodents). Further work is required to extend these results to determine the ability of these conifers to become tree line-forming species in the future. [ABSTRACT FROM AUTHOR]

Non-consumptive effects of predation have rarely been assessed in wildlife populations even though their impact could be as important as lethal effects. Reproduction of individuals is one of the most important demographic parameters that could be affected by predator-induced stress, which in turn can have important consequences on population dynamics. We studied non-consumptive effects of predation on the reproductive activity (i.e., mating and fertilization) of a cyclic population of brown lemmings exposed to intense summer predation in the Canadian High Arctic. Lemmings were live-trapped, their reproductive activity (i.e., testes visible in males, pregnancy/lactation in females) assessed, and predators were monitored during the summers of 2014 and 2015 within a 9 ha predator-reduction exclosure delimited by a fence and covered by a net, and on an 11 ha control area. Stress levels were quantified non-invasively with fecal corticosterone metabolites (FCM). We found that FCM levels of lemmings captured outside the predator exclosure (n = 50) were 1.6 times higher than inside (n = 51). The proportion of pregnant/lactating adult females did not differ between the two areas, nor did the proportion of adult scrotal males. We found that lemmings showed physiological stress reactions due to high predation risk, but had no sign of reduced mating activity or fertility. Thus, our results do not support the hypothesis of reproductive suppression by predator-induced stress. [ABSTRACT FROM AUTHOR]

Population cycles are one of nature's great mysteries. For almost a hundred years, innumerable studies have probed the causes of cyclic dynamics in snowshoe hares, voles and lemmings, forest Lepidoptera and grouse. Even though cyclic species have very different life histories, similarities in mechanisms related to their dynamics are apparent. In addition to high reproductive rates and density-related mortality from predators, pathogens or parasitoids, other characteristics include transgenerational reduced reproduction and dispersal with increasing-peak densities, and genetic similarity among populations. Experiments to stop cyclic dynamics and comparisons of cyclic and noncyclic populations provide some understanding but both reproduction and mortality must be considered. What determines variation in amplitude and periodicity of population outbreaks remains a mystery. [ABSTRACT FROM AUTHOR]

The isolated subspecies of Southern Bog Lemming of southeastern Virginia, Synaptomys cooperi helaletes, has been studied extensively since its "rediscovery" in the Great Dismal Swamp in 1980. Multiple studies using pitfall traps, starting in the Great Dismal Swamp National Wildlife Refuge and then extending elsewhere in southeastern Virginia and adjacent northeastern North Carolina, have revealed lemmings to be much more widespread and often more common than previously believed, with their presence now confirmed as far west as Surry and Sussex counties, about 30 km east of Petersburg, Virginia. When present, lemmings often are among the most numerous members of the small mammal community. Even in appropriate habitat, its presence seemingly is determined by its proximity to another arvicoline rodent, the Meadow Vole, Microtus pennsylvanicus, which usually is larger and perhaps competitively and behaviorally dominant. [ABSTRACT FROM AUTHOR]

Understanding the determinants of spatial and temporal differences in the relative strength of consumer-resource interactions is an important endeavour in ecology. Here, we explore the necessary conditions for temporal shifts in the relative strength of rodent-plant interactions in an area characterised by profound spatial differences in trophic control, with predator-prey interactions prevailing in productive habitats and rodent-plant interactions dominating unproductive habitats of the forest-tundra ecotone. We report data obtained during the exceptionally massive rodent outbreak of 2010-2012 in northernmost Fennoscandia, including an experimental manipulation of herbivore access to vegetation plots across a large-scale productivity gradient, multiple observational measures of plant-rodent interactions linked to rodent abundance data and a large-scale survey of breeding avian predators and mammalian predator activity. Unexpectedly, rodent grazing impacts documented during the rodent outbreak were uniformly strong across the landscape, regardless of habitat productivity. The runaway response in rodent populations was facilitated by a high population growth rate in the early phase of the outbreak due to the extended absence of predators in productive habitats, concomitant with an exceptionally long-lasting lemming outbreak in unproductive habitats. Our results showed that spatio-temporal variation in trophic control also occurs in ecosystems structured according to the exploitation ecosystems hypothesis and emphasises the importance of long-term studies to capture nonlinear and stochastic features that shape ecosystem functioning. In this context, the temporary release from top-down regulation in productive habitats caused strong grazing impacts that may be crucial for the resilience of tundra ecosystems under the threat of climate change-driven shrub encroachment. [ABSTRACT FROM AUTHOR]

Food availability has been proposed to be a factor driving population fluctuations of lemmings in the Arctic. In contrast with previous studies, a recent analysis of faecal pellets and stomach contents of brown lemmings ( Lemmus trimucronatus) reported a surprisingly high proportion (34-56%) of willows ( Salix spp.) in their diet during both summer and winter in the Canadian high Arctic. To better understand the contribution of willows to the diet of lemmings, we designed a cafeteria experiment to determine which part of Arctic willows ( S. arctica), usually the most abundant willow in the Canadian Arctic, were preferred by lemmings. We designed two types of experiments, one with flowering willows (summer stage; n = 10) and one with dormant willows without flowers or leaves (winter stage; n = 11). Lemmings preferred buds and to a lesser extent roots over woody stems in dormant willows, whereas in flowering willows, they preferred flowers and roots over leaves and buds. Our results suggest that lemmings shift their diet seasonally and prefer the fleshiest willow parts, i.e. flowers in summer and buds in winter. High consumption of roots by lemmings in both types of experiments indicates strong underground feeding habits. This behaviour could be favoured by geomorphological processes such as soil upheaves and permafrost thawing that often expose roots to grazing. [ABSTRACT FROM AUTHOR]

Trends in the dynamics of herbivore community related to trophic competition in summer have been analyzed on Wrangel Island. The results show that the trophic spectra overlap considerably, resources are partitioned on the principle 'weak competitors after strong competitors,' and community dynamics in the absence of extermination depend on specific competitive advantages related to the width of food spectrum. We conclude that the dynamics of this insular community prior to the establishment of nature reserve on the island have been determined by human activities, as well as the structure of arctic herbivore communities in general. [ABSTRACT FROM AUTHOR]

Using nonparametric tests, we analyzed the weights of the digestive tract organs of 198 rodent individuals belonging to 11 species of Arvicolinae (family Cricetidae) and Murinae (family Muridae), using both fresh and fixed material, the weight characteristics of which were identical. It has been shown that no unique dependence exists between the body weight and the entire digestive tract one in Arvicolinae rodents weighing 8-73 g. It was also shown that interspecific differences in the relative mass of such a dynamic system of organs as the digestive system cannot always be regarded as a function of the body size alone. [ABSTRACT FROM AUTHOR]

Spatial dispersion and clustering of populations is important for a complete understanding of ecological dynamics in many ecosystems. Motivated by an Arctic ecosystem involving foxes (predator), lemmings (prey), and seal carrion (subsidy), we extend the spatially homogeneous (island) model of predator–prey-subsidy dynamics originally proposed in Nevai and Van Gorder (2012) to account for dispersion of predator and prey populations throughout a two-dimensional domain. Our model has qualitatively similar behaviours in large regions of parameter space to the aforementioned island model. Quantitative effects due to varying the rate of dispersal and restricting the spatial extent of the subsidy are demonstrated. We observe nontrivial clustering of the predator and prey populations due to the presence of the subsidy only in a specific subregion of the domain, which suggests a novel mechanism of spatial partitioning and pattern formation due to the presence of subsidy in only part of the region of interest. [ABSTRACT FROM AUTHOR]

Interest in the ecology of stress in wild populations has triggered the development of noninvasive methods for quantifying stress hormones. Measurement of fecal corticosteroid metabolites (FCMs) is one such method, but it is still unclear whether FCMs can be a reliable proxy of free plasma glucocorticoids. To assess the validity of this assumption, we carried out a robust assessment on brown lemmings (Lemmus trimucronatus) from Bylot Island, Nunavut, Canada, that were hand captured and anesthetized and related plasma glucocorticoid levels to fecal metabolite glucocorticoid levels. We examined endogenous factors that could explain interindividual variability. Blood corticosterone was measured from samples obtained on capture and 30 min later, and FCM levels were measured from animals kept in captivity for 72 h. Plasma free corticosterone increased 135-fold over baseline values 30 min after capture, which confirmed that initial handling was perceived as a stressor. We found that FCM levels were highly related with free (marginal Rm2 = 0.53) but not with total (Rm2 = 0.02) corticosterone levels, regardless of age, sex, and reproductive condition. FCM levels started increasing 2 h after capture and reached maximum levels 4 h after capture. No circadian rhythm in FCMs was found. Plasma total corticosterone levels were much higher in adult females compared with adult males, but this difference was much smaller when measuring free corticosterone levels and FCM levels. Our results suggest that FCM levels are good measures of stress by being closely related to plasma free corticosterone levels in brown lemmings. [ABSTRACT FROM AUTHOR]

Rodents are among the most damaging pests in agriculture worldwide. High-density populations of rodent pests can kill plants or diminish their growth, and reduce both fruit size and the number of seeds. Therefore, rodent pests can lead to considerable crop loss and require management actions to minimize damage. Optimal management of pest rodents is usually based on the combination of methods to reduce damage. Although rodenticides are usually the most commonly deployed approach, they have undesirable side effects. Consequently, more environmentally benign approaches such as repellents or attractants to lure rodents away from fields are gaining traction. The dispersal of a large number of juvenile males at certain times of year has prompted us to focus on male rodents for our experiments. We used laboratory feeding experiments to measure how the odor of plant secondary metabolites (PSMs) affects two pest rodents: common voles ( Microtus arvalis, Pallas) and house mice ( Mus musculus, L.). We tested eighteen different PSMs or combinations thereof with voles. Four PSMs reduced feeding and seven PSMs increased feeding of male common voles. Five of six tested odors were effective as repellents against house mice. However, we assume a species-specific response to volatile PSMs repellents. This study demonstrated that four repellents reduced feeding in both rodent species. Our results contribute to the development of non-lethal management tools for rodent pest species that are potentially more suitable than traps and rodenticides. This approach could be applicable to a variety of crops if effective at field conditions. [ABSTRACT FROM AUTHOR]

A new species of the Mimomys is described from the Far East Russia (the Medvezhyi Klyk cave, Sikhote-Alin). Layer 7 of the Medvezhyi Klyk cave (1.08-1.18 m) was dated to be 13 790-14 200 BP. Mimomys chandolensis sp. nov. was found in a deeper layer (2.63-2.68 m) and therefore assuming there was no redeposition of the remains and that the accumulation proceeded gradually, the molar specimen we found is 30-50 kyr old. Due to the extent of the preservation we observed in the molar and the structure of the cave, the specimen does not seem likely to have been redeposited. Our hypothesis is that due to the warm and wet climate of the region, the vole, which became extinct more than 600 kyr ago, had been extant there by the Late Pleistocene period. The new species is hypsodont, with a few cement, a lack of enamel isle or prismatic fold; tangential and lamellar layers of enamel ultrastructure are poorly expressed. [ABSTRACT FROM AUTHOR]

Taxonomic identification of arvicolines (Arvicolinae, Rodentia) based on dental characteristics without taking into account cranial, external, or other nondental features is an important task in neontology when studying the diets of carnivorous mammals and birds of prey and in Quaternary paleontology, biostratigraphy, and paleoecology. The morphological criteria for the taxonomic identification of arvicoline molars are formalized in this paper. Dichotomous keys to identification of modern and Pleistocene arvicoline taxa of the Urals and Western Siberia based on the structural and histological characteristics and the occlusal configuration of the first lower molar are proposed. [ABSTRACT FROM AUTHOR]

Scansoriality (climbing) allows access to valuable resources in the arboreal niche and is widespread among mammals, yet little is known about how it originates from obligate terrestriality. The northern red-backed vole ( Myodes rutilus) is a small, Holarctic rodent long presumed to be strictly terrestrial, yet 3 of its congeners ( M. gapperi, M. glareolus, and M. californicus) have been observed climbing in trees. We conducted paired arboreal and ground trapping surveys in interior Alaska to investigate anecdotal accounts of tree-climbing behavior in M. rutilus. Results indicate that they readily climb up to 2 m above ground in trees of their own volition, a phenomenon heretofore undocumented in the literature. Camera trap videos show M. rutilus exhibiting behavior and dexterity-such as terminal branch arboreal quadrupedalism and head-first descent mediated by hindfoot rotation-generally associated with more arboreal species. Northern red-backed voles may therefore provide a new perspective on early stages of scansoriality in small-bodied mammals. [ABSTRACT FROM AUTHOR]

In the Arctic, food limitation is one of the driving factors behind small mammal population fluctuations. Active throughout the year, voles and lemmings (arvicoline rodents) are central prey in arctic food webs. Snow cover, however, makes the estimation of their winter diet challenging. We analyzed the isotopic composition of ever-growing incisors from species of voles and lemmings in northern Finland trapped in the spring and autumn. We found that resources appear to be reasonably partitioned and largely congruent with phylogeny. Our results reveal that winter resource use can be inferred from the tooth isotopic composition of rodents sampled in the spring, when trapping can be conducted, and that resources appear to be partitioned via competition under the snow. [ABSTRACT FROM AUTHOR]

Lemming population cycles in the Arctic have an important impact on the Arctic food web, indirectly also affecting breeding success in Arctic-nesting birds through shared predators. Over the last two decades lemming cycles have changed in amplitude and even disappeared in parts of the Arctic. To examine the large scale effect of these recent changes we re-analysed published data from the East Atlantic Flyway (EAF), where a relationship between lemming cycles and wader breeding success was earlier found, and new data on breeding success of waders in the East Asian-Australasian Flyway (EAAF). We found that 1) any long-term periodicities in wader breeding success existed only until the year 2000 in the EAAF and until the 1980s in the EAF; 2) studying these patterns at a smaller spatial scale, where the Siberian-Alaskan breeding grounds were divided into five geographical units largely based on landscape features, breeding success of waders from the EAAF was not correlated to an index of predation pressure, but positively correlated to Arctic summer temperatures in some species. We argue that fading out of lemming cycles in some parts of the Arctic is responsible for faltering periodicity in wader breeding success along both flyways. These changed conditions have not yet resulted in any marked changing trends in breeding success across years, and declining numbers of waders along the EAAF are therefore more likely a result of changing conditions at stop-over and wintering sites. [ABSTRACT FROM AUTHOR]

Lemmings is a computer puzzle game developed by DMA Design and published by Psygnosis in 1991, in which the player has to guide a tribe of lemming creatures to safety through a hazardous landscape, by assigning them specific skills that modify their behavior in different ways. In this paper we study the optimization problem of saving the highest number of lemmings in a given landscape with a given number of available skills. We prove that the game is PSPACE -complete, even if there is only one lemming to save, and only Builder and Basher skills are available. We thereby settle an open problem posed by Cormode in 2004, and again by Forišek in 2010. However we also prove that, if we restrict the game to levels in which the available Builder skills are only polynomially many (and there is any number of other skills), then the game is solvable in NP . Similarly, if the available Basher, Miner, and Digger skills are polynomially many, the game is solvable in NP . Furthermore, we show that saving the maximum number of lemmings is APX -hard, even when only one type of skill is available, whatever this skill is. This contrasts with the membership in P of the decision problem restricted to levels with no “deadly areas” (such as water or traps) and only Climber and Floater skills, as previously established by Cormode. [ABSTRACT FROM AUTHOR]

Long-tailed Jaegers ( Stercorarius longicaudus) normally lay one or two eggs (rarely three), with a maximum of two eggs set by the existence of only two brood patches. Here, however, we present the first documentation of a clutch of four eggs in a Long-tailed Jaeger nest found at Zackenberg in northeastern Greenland. [ABSTRACT FROM AUTHOR]

We describe tularaemia in a Norwegian dog caused by Francisella tularensis subspecies holarctica . A Hamilton Hound and his owner developed tulaeremia after hunting an infected mountain hare ( Lepus timidus ). The dog showed signs of lethargy, anorexia and fever during a period two to four days after hunting and thereafter fully recovered. Its antibody titers increased 32-fold from one to three weeks post exposure. Thereafter, the titer declined and leveled off at moderate positive values up to one year after exposure (end of study). This is believed to be the first case report of clinical F. tularensis subspecies holarctica infection in a European dog. In 2011, enormous numbers of Norway lemmings ( Lemmus lemmus ) occurred in Finnmark, the northernmost county of Norway and many dogs caught and swallowed lemmings. Some of these dogs developed non-specific signs of disease and the owners consulted a veterinary surgeon, who suspected tularaemia. In order to investigate this hypothesis, serum samples from 33 dogs were examined for antibodies to F. tularensis . The dogs were allocated into three groups: Dogs from Finnmark that became sick (Group 1) or remained healthy following contact with lemmings (Group 2), and healthy control dogs from Oslo without known contact with lemmings (Group 3). All the serum samples were analyzed with a tube agglutination assay. Among dogs exposed to lemmings, 10/11 and 3/12 were antibody positive in Group 1 and Group 2, respectively, whereas none of the control dogs ( n = 10) were positive for antibodies against F. tularensis . These results strongly indicate that the non-specific disease seen in the dogs in Finnmark was linked to F. tularensis infection acquired through contact with lemmings. [ABSTRACT FROM AUTHOR]

The alternative prey hypothesis (APH) suggests that the functional and numerical response of predators to fluctuating rodent populations may drive annual variation in predation pressure on other available prey such as bird eggs. Most studies that have provided evidence supporting the APH in arctic bird populations have been conducted in the eastern hemisphere, and considerably less evidence for APH has emerged from western hemisphere populations. We tested the hypothesis that predation pressure on shorebird nests would increase as lemming abundance decreases due to apparent competition between lemmings and shorebirds via their shared predators in the eastern Canadian High Arctic. Over a period of 5 years on Bylot Island, Nunavut, Canada, we found that lemming abundance had a significant negative effect on predation risk as measured by artificial nests. Survival probabilities of artificial nests were also negatively related to fox abundance but positively associated with the abundance of breeding avian predators, likely due to predator exclusion around avian predator nests. Models of daily nest survival for real nests also indicated that interannual variation in nest survival was best explained by lemming abundance. Combined results from both artificial and real nests indicate that fluctuations in lemming populations likely have an indirect effect on predation pressure on shorebird eggs in the Canadian High Arctic, although mechanisms explaining the observed relationship require further investigation. [ABSTRACT FROM AUTHOR]

Highlights: [•] First multilocus treatment of a diverse Holarctic rodent tribe, Myodini. [•] Elevation of the subgenus Craseomys to genus is corroborated. [•] Two species of Alticola show mtDNA capture and raise possibility of adaptive acquisition. [•] First DNA assessment of Hyperacrius questions its affinity to Myodini. [•] Myodini did not diversify via punctuated bursts of diversification. [ABSTRACT FROM AUTHOR]

Both the theory and the observations suggest that, there are strong links between herbivores and plants in terrestrial ecosystems; although, the effect of herbivores on plant community biomass is often attributed to variations in plant palatability. The existence of a strong link is commonly tested by constructing exclosures that exclude herbivores during a period of time. We here present data from two long-term (9 and 20 years, respectively) herbivore exclosure studies in lemming habitats on arctic tundra in northernmost Norway. The exclusion of all mammalian herbivores triggered strong increases in community level plant biomass and substantial changes in plant community composition. Palatable plants like graminoids and large bryophytes, as well as unpalatable plants like evergreen ericoids, deciduous shrubs, and lichens were all favored by excluding lemmings. These results reveal that a substantial increase in community biomass which occurs only when plant species capable of accumulating biomass are present, and palatability is a poor predictor of long-term responses of plants to excluding herbivores. [ABSTRACT FROM AUTHOR]

Geographical patterns of morphological variation in small mammals are often associated with environmental factors. The southern red-backed vole Myodes gapperi is a widespread and abundant small mammal in Canada, occurring in environments as diverse as mixed-wood forests and taiga. First upper molars and skulls from nine populations of southern red-backed voles distributed across three ecozones and approximately 10° of latitude were analysed by means of geometric morphometric techniques, and their relationships with environmental variables were examined. A weak, non-linear trend of size increase towards higher latitudes was observed in voles' skulls. Environmental variables appeared to be important drivers of shape differentiation among populations from the three distinct ecozones analysed. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 112, 204-218. [ABSTRACT FROM AUTHOR]

Calodium hepaticum (syn. Capillaria hepatica) is a worldwide-distributed species of zoonotic nematodes with a high affinity to the liver. Several rodent species of the superfamily Muroidea serve as main hosts for this pathogen. C. hepaticum has been found in Muroidean hosts in more than 60 countries in Europe; North, Central, and South America; Asia; Africa; and Oceania. C. hepaticum was documented in more than 90 Muroidean rodent species (Murinae, Deomyinae, Arvicolinae, Neotominae, Cricetinae, Sigmodontinae, Gerbillinae, and Cricetomyinae). Globally, the Norway rat ( Rattus norvegicus) seems to be the main host species for this nematode. However, locally high prevalences (above 50 %) have also been observed in several other synanthropic (commensal and non-commensal) Muroidea species (e.g., Rattus tanezumi, Ondatra zibethicus, Apodemus sylvaticus). This review gives an overview of the distribution and host spectrum of C. hepaticum in Muroidea host species. [ABSTRACT FROM AUTHOR]

While shrubs appear to be expanding in Arctic tundra due to climatic warming, patches of tall shrubs in riparian habitats are most likely to colonize new areas. Shrub recruits outside established patches represent the forefront of area expansion, but their dynamics may be sensitive to the action of several herbivore species. The empirical evidence for how different-sized herbivores affect recruits of tall shrubs is lacking. Moreover, although management and natural population dynamics of herbivores happens at landscape and regional scales, field research on herbivore impacts on shrubs seldom covers these scales., Reindeer management and different rodent population dynamics result in regional variation in herbivore abundances in arctic Norway. We conducted an herbivore exclusion experiment, covering three low-arctic river catchments with contrasting herbivore abundances. We assessed the impacts of small rodents and reindeer on growth, and survival of willow Salix spp. recruits after 3 years of herbivore exclusion., As expected, the Salix recruits increased in sizes and had lower mortality when released from herbivores. Both types of herbivores had strong impacts on size and survival of Salix recruits., Spatially contrasting results were consistent with regional differences in the abundance of reindeer and rodents; herbivore impacts on shrubs were found when at least one type of herbivore was abundant. However, the impact was not independent of herbivore species. While both browsing from reindeer and rodents pruned the recruits and prevented them from escaping the field layer, the rodents also inflicted substantial mortality and thus thinned the stand of recruits., Synthesis and applications. Sympatric populations of rodents and reindeer have strongly complementary impacts on shrub recruits and may limit the expansion potential of tall shrubs even in the most productive habitats of arctic tundra. The spatial correspondence between shrub recruits performance and herbivore abundances, found after a short time period, suggests that the extent of tall shrub expansion in tundra is contingent on current variation and future trends in herbivore populations. In areas where humans control large herbivore populations, management may opt to counteract climate-driven shrub expansion also in habitats that are most prone to such expansion. [ABSTRACT FROM AUTHOR]

Prédation has been suggested to be especially important in simple food webs and less productive ecosystems such as the arctic tundra, but very few data are available to evaluate this hypothesis. We examined the hypothesis that avian predators could drive the population dynamics of two cyclic lemming species in the Canadian Arctic. A dense and diverse suite of predatory birds, including the Snowy Owl (Bubo scandiacus), the Rough-legged Hawk (Buteo lagopus), and the Long-tailed Jaeger (Stercorarius longicaudus), inhabits the arctic tundra and prey on collared (Dicrostonyx groenlandicus) and brown (Lemmus trimucronatus) lemmings during the snow-free period. We evaluated the prédation pressure exerted by these predators by combining their numerical (variation in breeding and fledgling numbers) and functional (variation in diet and daily consumption rates) responses to variations in lemming densities over the 2004-2010 period. Breeding density and number of fledglings produced by the three main avian predators increased sharply without delay in response to increasing lemming densities. The proportion of collared lemmings in the diet of those predators was high at low lemming density (both species) but decreased as lemming density increased. However, we found little evidence that their daily consumption rates vary in relation to changes in lemming density. Total consumption rate by avian predators initially increased more rapidly for collared lemming but eventually leveled off at a much higher value for brown lemmings, the most abundant species at our site. The combined daily prédation rate of avian predators exceeded the maximum daily potential growth rates of both lemming species except at the highest recorded densities for brown lemmings. We thus show, for the first time, that prédation pressure exerted without delay by avian predators can limit populations of coexisting lemming species during the snow-free period, and thus, that prédation could play a role in the cyclic dynamic of these species in the tundra. [ABSTRACT FROM AUTHOR]

Predicting impacts of global warming requires understanding of the extent to which plant biomass and production are controlled by bottom-up and top-down drivers. By annually monitoring community composition in grazed control plots and herbivore-free exclosures at an Arctic location for 15 years, we detected multiple biotic interactions. Regular rodent cycles acted as pulses driving synchronous fluctuations in the biomass of field-layer vegetation; reindeer influenced the biomass of taller shrubs, and the abundance of plant pathogenic fungi increased when densities of their host plants increased in exclosures. Two outbreaks of geometrid moths occurred during the study period, with contrasting effects on the field layer: one in 2004 had marginal effects, while one in 2012 severely reduced biomass in the control plots and eliminated biomass that had accumulated over 15 years in the exclosures. The latter was followed by a dramatic decline of the dominant understory dwarf-shrub Empetrum hermaphroditum, driven by an interaction between moth herbivory on top buds and leaves, and increased disease severity of a pathogenic fungus. We show that the climate has important direct and indirect effects on all these biotic interactions. We conclude that long time series are essential to identify key biotic interactions in ecosystems, since their importance will be influenced by climatic conditions, and that manipulative treatments are needed in order to obtain the mechanistic understanding needed for robust predictions of future ecosystem changes and their feedback effects. [ABSTRACT FROM AUTHOR]

In the Arctic tundra, snow is believed to protect lemmings from mammalian predators during winter. We hypothesized that snow quality (depth and hardness) should affect mammalian predation rates on lemmings, but that this effect would depend on the predator hunting strategy; and that predation by ermines (Mustela erminea), which can hunt lemmings under the snow, should be higher in preferred lemming habitats. We measured snow depth and hardness at tunnels made by arctic fox (Vulpes lagopus) predation attempts, at winter nests nonpredated and predated by ermines, and at random locations. We also determined winter nest density in 3 habitats (wet, mesic, and gully). Deep and hard snow restricted fox predation attempts made by jumping through the snow, but not those made by digging. Ermine predation was unaffected by snow depth and weakly by nest density but was higher in gully and intermediate in mesic habitats, which are conducive to high snow accumulation, compared to the wet habitat. These results indicate that habitat-related topographical features are more important than snow depth or nest density per se in affecting the winter foraging strategy of ermines. Overall, even though we found a relatively weak effect of the snow cover on predation by foxes and ermines, it is difficult to predict how upcoming changes to the snow cover will affect lemming vulnerability to mammalian predators because a wide range of snow conditions may result from climate warming. [ABSTRACT FROM AUTHOR]

Lemmings are key herbivores in many arctic food webs, and their population dynamics have major impacts on the functioning of tundra systems. However, current knowledge of lemming diet is limited, hampering evaluation of lemming-vegetation interactions. This lack of knowledge is mainly due to methodological challenges, as previously used microhistological methods result in large proportions of poorly resolved plant taxa. We analyzed diets of Norwegian lemmings ( Lemmus lemmus) in three different habitats using a new method, DNA metabarcoding of stomach contents. To achieve detailed information on ingested vascular plants, bryophytes, and fungi, we amplified short fragments of chloroplast DNA (for plants; P6 loop of the trnL intron) and nuclear ribosomal DNA (for fungi; ITS1-region). Our results revealed that lemming diets were dominated by grasses, mainly Avenella flexuosa, and mosses, mainly Dicranum spp., but that a variety of other food items were also eaten. Vascular plant composition of the diets differed between heath, meadow, and wetland habitats, whereas bryophyte composition did not. Also, a variety of fungal taxa were retrieved, but as most of the identified taxa belong to micromycetes, they were unlikely to be consumed as food. The role of fungi in the diet of lemmings remains to be investigated. We suggest that there may be substantial variation between habitats and regions in lemming diet. [ABSTRACT FROM AUTHOR]

Apparent competition between prey is hypothesized to occur more frequently in environments with low densities of preferred prey, where predators are forced to forage for multiple prey items. In the arctic tundra, numerical and functional responses of predators to preferred prey (lemmings) affect the predation pressure on alternative prey (goose eggs) and predators aggregate in areas of high alternative prey density. Therefore, we hypothesized that predation risk on incidental prey (shorebird eggs) would increase in patches of high goose nest density when lemmings were scarce. To test this hypothesis, we measured predation risk on artificial shorebird nests in quadrats varying in goose nest density on Bylot Island (Nunavut, Canada) across three summers with variable lemming abundance. Predation risk on artificial shorebird nests was positively related to goose nest density, and this relationship was strongest at low lemming abundance when predation risk increased by 600% as goose nest density increased from 0 to 12 nests ha−1. Camera monitoring showed that activity of arctic foxes, the most important predator, increased with goose nest density. Our data support our incidental prey hypothesis; when preferred prey decrease in abundance, predator mediated apparent competition via aggregative response occurs between the alternative and incidental prey items. [ABSTRACT FROM AUTHOR]

This research is continuation of the investigation of metal accumulation in native and transplanted moss Pleurozium schreberi in the most industrialized and affected region in Poland (Upper Silesia). We tested the hypotheses that in Upper Silesia transplants of P. schreberi may be used in a 90 days bioindication experiment in case native specimens are absent; a 90 days exposure of transplanted P. schreberi was long enough for evaluation of Hg pollution of the environment. An assay was carried out with native mosses at 27 polluted sites and mosses from an uncontaminated control site transplanted to the same 27 polluted sites. P. schreberi collected from the same sites as classified for more and less polluted basing on Pb and Zn concentrations show quite different pattern of pollution with mercury; The accumulation of Hg by the transplants increased much faster in the first 45 days of the experiment (accumulation factor 1.5-6.7; mean 3.4 ± 0.5) in comparison with the second period from day 45 to 90 (accumulation factor 1.0-1.6; mean 1.2 ± 0.1). The 90 days exposure of transplanted P. schreberi was long enough for evaluation of Hg pollution of the environment. Transplants of P. schreberi may be used in a 90 days bioindication experiment in case native specimens are absent. [ABSTRACT FROM AUTHOR]

Based on evidence from a series of recent studies linking behaviour to demography in experimental vole populations we propose how intrinsic and extrinsic factors interact through the various phases of the multi-annual population cycles of voles and lemmings. We hypothesise that population growth in the increase phase of the cycle is enhanced by a high degree of space sharing (sociality) among reproductive females who share resource patches, especially during winter. These social females enjoy a high reproductive output due to good resource conditions, and facilitation provided by communal thermoregulation, breeding and defence of weanlings towards infanticidal conspecifics. We hypothesise on the other hand that the crash phase is initiated and enhanced by predation of adult males that leads to a series of cascading events involving infanticidal behaviour by immigrant males, increased mortality of adult social females, and inversely density-dependent and/or disturbance-induced dispersal. These events further enhance predation-induced mortality and thus a negative feed-back loop to the rate of the crash. In this framework we may explain how extrinsic factors such as predation and winter resource distribution contribute to transitions between docile and aggressive behaviours, and how this transition is spatially synchronised by inversely density-dependent dispersal that may act to mediate a rapidly spreading wave throughout the population. We propose that innate differences among rodent species in their propensities for different social organizations also determine their propensity for exhibiting multi-annual cycles as well as other cycle-related phenomena such as shape of the population cycles and spatial synchrony. We provide a set of testable predictions for further empirical evaluation. [ABSTRACT FROM AUTHOR]

We attempted to live trap lemmings under the snow in their preferred winter habitat at two sites in the Canadian Arctic using chimney-like boxes. Lemmings used the boxes during winter, but we had very low trapping success in April and May. During spring trapping, in contrast to most of the winter, subnivean temperatures became colder than ambient air temperatures. We hypothesize that our low success in spring resulted from lemmings' leaving the deeper snow areas where our boxes were located and moving to shallower snow or exposed tundra. We suggest that the trapping boxes could be successful if trapping occurred earlier during winter. [ABSTRACT FROM AUTHOR]

More than a quarter of the world's carnivores are threatened, often due to multiple and complex causes. Considerable research efforts are devoted to resolving the mechanisms behind these threats in order to provide a basis for relevant conservation actions. However, even when the underlying mechanisms are known, specific actions aimed at direct support for carnivores are difficult to implement and evaluate at efficient spatial and temporal scales., We report on a 30-year inventory of the critically endangered Fennoscandian arctic fox Vulpes lagopus L., including yearly surveys of 600 fox dens covering 21 000 km2. These surveys showed that the population was close to extinction in 2000, with 40-60 adult animals left. However, the population subsequently showed a fourfold increase in size., During this time period, conservation actions through supplementary feeding and predator removal were implemented in several regions across Scandinavia, encompassing 79% of the area. To evaluate these actions, we examined the effect of supplemental winter feeding and red fox control applied at different intensities in 10 regions. A path analysis indicated that 47% of the explained variation in population productivity could be attributed to lemming abundance, whereas winter feeding had a 29% effect and red fox control a 20% effect., This confirms that arctic foxes are highly dependent on lemming population fluctuations but also shows that red foxes severely impact the viability of arctic foxes. This study also highlights the importance of implementing conservation actions on extensive spatial and temporal scales, with geographically dispersed actions to scientifically evaluate the effects. We note that population recovery was only seen in regions with a high intensity of management actions., Synthesis and applications. The present study demonstrates that carnivore population declines may be reversed through extensive actions that target specific threats. Fennoscandian arctic fox is still endangered, due to low population connectivity and expected climate impacts on the distribution and dynamics of lemmings and red foxes. Climate warming is expected to contribute to both more irregular lemming dynamics and red fox appearance in tundra areas; however, the effects of climate change can be mitigated through intensive management actions such as supplemental feeding and red fox control. [ABSTRACT FROM AUTHOR]

Numbers of Western Atlantic Red Knots ( Calidris canutus rufa (A. Wilson, 1813)) have declined since 1980, with a sustained downward trend observed after 1998. Because the reproductive output of a closely related Eurasian subspecies ( Calidris canutus islandica (L., 1767)) is known to be low when lemming numbers are low, and because lemming cycles in Fennoscandia were recently interrupted, we investigated the relationship between the rodent cycle in arctic Canada and numbers of C. c. rufa migrating through the United States. Shooting records from Cape Cod in the 1800s and Red Knot counts on the Delaware Bay from 1986 to 1998 cycled with 4-year periods. Annual peaks in numbers of Red Knots stopping in the Delaware Bay in 1986-1998 occurred 2 years after arctic rodent peaks more often than expected at random. The results suggest that the reproductive output of C. c. rufa was linked to the rodent cycle before the Red Knot decline. There is no evidence that such a link existed after 1998. These findings are consistent with the hypothesis that an interruption of the rodent cycle in Red Knot habitat could have been a driver in the recent Red Knot decline. Field studies in the Arctic are needed to further investigate this hypothesis. [ABSTRACT FROM AUTHOR]

Lemming cycles are a key process in the functioning of tundra ecosystems. Although it is agreed that trophic interactions are important in causing the cycles, the actual mechanism is disputed. Some researchers attribute a major role to predation by small mustelids such as stoats and least weasels. Here we present a 40-year time series of lemming dynamics from Wrangel Island and show statistically that lemmings do exhibit population cycles in the absence of small mustelids. The observed density fluctuations differed, however, from those observed elsewhere, with long cycles and possibly higher densities of lemmings during the low phase. These differences in the shape of the population cycles may be related to the unique species assemblage of Wrangel Island, where arctic foxes are the only year-round resident lemming predator, and to the high diversity of landscapes, microclimatic conditions, and plants on the island. Both spectral analysis and wavelet analysis show a change in period length from five years in the 1970s to nearly eight years in the 1990s and 2000s. This change in dynamics coincides with reports of dampening or fading out of lemming cycles that have been observed in several regions of the Arctic in recent decades. As in the other cases, the changed lemming dynamics on Wrangel Island may be related to ground icing in winter, which could delay peak years. [ABSTRACT FROM AUTHOR]

Synapsis and reciprocal recombination between sex chromosomes are restricted to the pseudoautosomal region. In some animal species, sex chromosomes do not present this region, although they utilize alternative mechanisms that ensure meiotic pairing and segregation. The subfamily Arvicolinae (Rodentia, Cricetidae) includes numerous species with achiasmate sex chromosomes. In order to know whether the mechanism involved in achiasmate segregation is an ancient feature in arvicolid species, we have compared the sex chromosomes of both the Mediterranean vole ( Microtus duodecimcostatus) and the water vole ( Arvicola terrestris). By means of immunofluorescence, we have found that sex chromosomes in M. duodecimcostatus are asynaptic and develop a synaptonemal complex-derived structure that mediates pairing and facilitates segregation. In A. terrestris, sex chromosomes are synaptic and chiasmate but also exhibit a synaptonemal complex-derived filament during anaphase I. Since phylogenetic relationships indicate that the synaptic condition is ancestral in arvicolids, this finding indicates that the mechanism for achiasmate sex chromosome segregation precedes the switching to the asynaptic condition. We discuss the origin of this synaptonemal complex-derived mechanism that, in turn, could counterbalance the disruption of homology in the sex chromosomes of those species. [ABSTRACT FROM AUTHOR]

The sibling species Microtus arvalis and Microtus rossiaemeridionalis are widely sympatric, North Eurasian species that are difficult to trace back in the fossil record due to the lack of criteria for taxonomic identification. This paper examines the potential of morphometric and molecular methods for differentiating their fossil remains. Discriminant function (DF) analysis of linear measurements of the lower first molar (m1) is used to create and validate a predictive model for taxonomic identification using modern M. arvalis (obscurus karyotypic form) and M. rossiaemeridionalis from the Ural Mountains. For modern specimens both the derived DF and the molecular methods yielded identical results for species identification. DF derived from modern data was applied to m1s of M. arvalis sensu lato from Subatlanticum (1300–1200 BP) and Atlanticum (7380 ± 150 BP) layers of the Pershinskaya 1 cave in the Middle Urals. In addition, from 27 mandibles with m1 in the morphological dataset 258 bp of cytochrome b were sequenced using ancient DNA techniques. Comparison of the morphological and molecular results revealed a substantial loss of predictive power of the DF derived from modern data when applied to fossils. Morphological change since the mid Holocene appears detrimental to DF derived from recent data. Our results emphasize the need for verification of taxonomic inferences from morphological data when dealing with sibling species, and accentuate the advantages of joint use of morphological and molecular methods in differentiating cryptic taxa in the fossil record. [ABSTRACT FROM AUTHOR]

In this paper are described the arvicolines from El Chaparral site (Villaluenga del Rosario, Cádiz, Southwestern Spain). Due to their wide geographical distributions and rapid evolutionary rates, arvicolines are especially useful for biostratigraphical purposes. The stratigraphic layers of El Chaparral have yielded arvicolines remains of the genera Allophaiomys, Iberomys, Pliomys, and Terricola. The presence of these rodents together the other vertebrates recovered allows to determinate the age of the El Chaparral site and compare our data with other Iberian Pleistocene sites, such as of the Sierra de Atapuerca. El Chaparral site ranges between the Jaramillo Subchron (1.07-0.99 Ma) and shortly after the Brunhes-Matuyama transition at 0.78 Ma covering a important time span for the knowledge of the earliest humans occupations in western Europe. [ABSTRACT FROM AUTHOR]