Probability Of Local Extinction Research Articles

An occupancy-based quantification of the highly imperiled status of desert fishes of the southwestern United States.

Desert fishes are some of the most imperiled vertebrates worldwide due to their low economic worth and because they compete with humans for water. An ecological complex of fishes, 2 suckers (Catostomus latipinnis, Catostomus discobolus) and a chub (Gila robusta) (collectively managed as the so-called three species) are endemic to the U.S. Colorado River Basin, are affected by multiple stressors, and have allegedly declined dramatically. We built a series of occupancy models to determine relationships between trends in occupancy, local extinction, and local colonization rates, identify potential limiting factors, and evaluate the suitability of managing the 3 species collectively. For a historical period (1889-2011), top performing models (AICc) included a positive time trend in local extinction probability and a negative trend in local colonization probability. As flood frequency decreased post-development local extinction probability increased. By the end of the time series, 47% (95% CI 34-61) and 15% (95% CI 6-33) of sites remained occupied by the suckers and the chub, respectively, and models with the 2 species of sucker as one group and the chub as the other performed best. For a contemporary period (2001-2011), top performing (based on AICc ) models included peak annual discharge. As peak discharge increased, local extinction probability decreased and local colonization probability increased. For the contemporary period, results of models that split all 3 species into separate groups were similar to results of models that combined the 2 suckers but not the chub. Collectively, these results confirmed that declines in these fishes were strongly associated with water development and that relative to their historic distribution all 3 species have declined dramatically. Further, the chub was distinct in that it declined the most dramatically and therefore may need to be managed separately. Our modeling approach may be useful in other situations in which targeted data are sparse and conservation status and best management approach for multiple species are uncertain.

Relating life‐history traits, environmental constraints and local extinctions in river fish

Summary The life histories of freshwater fish are widely studied because they represent fundamental determinants of population performances. However, a gap remains in our understanding of how species traits may predispose species to extinction in a changing environment. In this study, based on a large data set provided by the French National Agency for Water and Aquatic Environment (325 sites), we analysed factors that explain the probability of local extinction in 40 freshwater species across French rivers. A total of five traits characterised the demography of 40 species, and eight environmental parameters at the 325 sites were examined. Our results agreed closely with an empirical classification of freshwater fish in temperate regions, conforming to three‐endpoint continuum of life‐history ‘strategies’ of species (equilibrium, periodic and opportunist). The probability of local species extinction was closely related to species traits. Equilibrial species tended to show lower annual extinction rates, whereas opportunistic species and, above all, periodic ones exhibited higher extinction values. Nevertheless, prediction of species local extinctions is not trivial and depends not only on particular suites of life‐history traits but also on their interaction with environmental conditions along the longitudinal river continuum.

On the evolution of dispersal via heterogeneity in spatial connectivity.

Dispersal has long been recognized as a mechanism that shapes many observed ecological and evolutionary processes. Thus, understanding the factors that promote its evolution remains a major goal in evolutionary ecology. Landscape connectivity may mediate the trade-off between the forces in favour of dispersal propensity (e.g. kin-competition, local extinction probability) and those against it (e.g. energetic or survival costs of dispersal). It remains, however, an open question how differing degrees of landscape connectivity may select for different dispersal strategies. We implemented an individual-based model to study the evolution of dispersal on landscapes that differed in the variance of connectivity across patches ranging from networks with all patches equally connected to highly heterogeneous networks. The parthenogenetic individuals dispersed based on a flexible logistic function of local abundance. Our results suggest, all else being equal, that landscapes differing in their connectivity patterns will select for different dispersal strategies and that these strategies confer a long-term fitness advantage to individuals at the regional scale. The strength of the selection will, however, vary across network types, being stronger on heterogeneous landscapes compared with the ones where all patches have equal connectivity. Our findings highlight how landscape connectivity can determine the evolution of dispersal strategies, which in turn affects how we think about important ecological dynamics such as metapopulation persistence and range expansion.

Demogenetic structure of brown troutSalmo truttaLinnaeus, 1758 populations in mountain headwaters: implications for conservation management

A demogenetic analysis based on 7 years of observation (2005–2011) was conducted to examine the population structure of brown trout Salmo trutta in pristine dendritic headwaters. The value of genetic divergence (FST) among sampling units ranged from −0.03 to 0.16. Demographic synchrony was low or moderate, and the average correlation coefficient of population growth between sampling units () ranged from 0.28 to 0.66. No isolation by distance was observed, but genetic divergence was negatively correlated with demographic synchrony among sampling units. Variance in the population growth rate (i.e. local extinction probability) increased with distance from the mainstream and from other sampling units. In contradiction with the usual model of stream-dwelling salmonids, the upstream sections of headwaters holds only ephemeral subpopulations, whereas the mainstream played a role in the source area of the metapopulation. These findings stress the importance of the mainstream in management conservation for brown trout in low productive mountain headwaters.

Quantifying the impact of Gambusia holbrooki on the extinction risk of the critically endangered red‐finned blue‐eye

Managing competing endangered and invasive species in spatially structured environments is challenging because it is often difficult to control invasive species without negatively impacting the endangered species. Effective management action requires an understanding of the factors affecting the presence and absence of each species so that promising sites for relocation of endangered species combined with eradication of invasive species can be identified. We investigate competing hypotheses about the factors affecting occupancy of the critically endangered red‐finned blue‐eye (Scaturiginichthys vermeilipinnis; hereafter ‘RFBE'), a native Australian fish with a global distribution that is restricted to a group of shallow artesian springs. RFBE are threatened by competition with invasive mosquito fish (Gambusia holbrooki), which are steadily colonizing the springs, resulting in local extinctions of RFBE in most cases. While hypotheses about the influences of Gambusia on RFBE exist, none have been tested with a quantitative model. We used a spatially‐structured two‐species occupancy modeling approach to examine the occupancy dynamics of these fish and tested competing hypotheses on how Gambusia occupancy affected RFBE. Gambusia occupancy had a strong negative effect on RFBE occupancy and colonization potential; increasing the probability of local extinction at a spring and decreasing the persistence probability of RFBE in a spring by 8.0% ± 2.7% (mean ± 1 SE). We found strongest support for the hypotheses that elevation and spring area influence colonization, and that spring area influences patch extinction probability. Using colonization and local extinction estimates for both species, we identify promising sites for eradication of Gambusia and relocation of RFBE.

Metapopulation analysis indicates native and non‐native fishes respond differently to effects of wildfire on desert streams

AbstractAsh flows and flooding associated with wildfires represent important but understudied sources of disturbance for fish populations. Knowledge concerning these disturbances is especially limited for larger streams where warm water species dominate. Fire‐related disturbances have been hypothesised to differentially affect native and non‐native fishes, although this hypothesis has only been tested for salmonids. The objective of our research was to contrast effects of uncharacteristically large wildfires followed by flooding on metapopulations of native and non‐native fishes in theGilaRiver of southwestNewMexico. Probabilities of occupancy, colonisation and local extinction of fishes were calculated across sites before and during disturbance and were also measured across a broader spatial scale during disturbance to identify potential refuge locations. Occupancy was higher for native fishes than non‐natives, but multiple wildfire and flood events increased extinction probabilities of native species. Responses of non‐native species to wildfires were mixed; extinction of non‐native salmonids increased during disturbance, while extinction of several warm water species remained unchanged or decreased. Several undisturbed sites were poor refugia for natives as they were impacted by non‐native piscivores, dewatering, and fragmentation. However, despite exposure to multiple disturbances, sites located in large tributary and valley reaches were consistently occupied by native species, suggesting these habitats provided refugia. We suggest that management actions (forest thinning; prescribed burning) that restore a more natural disturbance regime of small and less severe fires coupled with habitat remediation activities (non‐native removal; decreased water withdrawal; improved connectivity) might diminish extinction risk for native fishes exposed to wildfire disturbance.

Disease alters macroecological patterns of North American bats

AbstractAimWe investigated the effects of disease on the local abundances and distributions of species at continental scales by examining the impacts of white‐nose syndrome, an infectious disease of hibernating bats, which has recently emerged in North America.LocationNorth America and Europe.MethodsWe used four decades of population counts from 1108 populations to compare the local abundances of bats in North America before and after the emergence of white‐nose syndrome to the situation in Europe, where the disease is endemic. We also examined the probability of local extinction for six species of hibernating bats in eastern North America and assessed the influence of winter colony size prior to the emergence of white‐nose syndrome on the risk of local extinction.ResultsWhite‐nose syndrome has caused a 10‐fold decrease in the abundance of bats at hibernacula in North America, eliminating large differences in species abundance patterns that existed between Europe and North America prior to disease emergence. White‐nose syndrome has also caused extensive local extinctions (up to 69% of sites in a single species). For five out of six species, the risk of local extinction was lower in larger winter populations, as expected from theory, but for the most affected species, the northern long‐eared bat (Myotis septentrionalis), extinction risk was constant across winter colony sizes, demonstrating that disease can sometimes eliminate numerical rarity as the dominant driver of extinction risk by driving both small and large populations extinct.Main conclusionsSpecies interactions, including disease, play an underappreciated role in macroecological patterns and influence broad patterns of species abundance, occurrence and extinction.

Barred owls and landscape attributes influence territory occupancy of northern spotted owls.

We used multi-season occupancy analyses to model 2 fates of northern spotted owl territories in relation to habitat amount, habitat fragmentation, and the presence of barred owls in Washington State, USA, 1989–2005. Local colonization is the probability a territory unoccupied by a spotted owl in year i would be occupied in year i + 1, and local extinction is the probability a territory that was occupied by a spotted owl in year i would be unoccupied in year i + 1. We found a negative relationship between local extinction probability and amount of late-seral forest edge. We found a negative relationship between colonization probability and the number of late-seral forest patches (higher fragmentation), and a negative relationship between colonization probability and the amount of non-habitat within 600 m of a spotted owl territory center (Akaike weight = 0.59). The presence of barred owls was positively related to extinction probability and negatively related to detection probability of spotted owls. The negative relationship between presence of barred owls and detectability of spotted owls indicated that spotted owls could be modifying their calling behavior in the presence of barred owls. The positive relationship between barred owl detections and local extinction probability suggests that because of competition with barred owls, spotted owls are being displaced. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.

High-speed tomographic PIV measurements of strain rate intermittency and clustering in turbulent partially-premixed jet flames

The effects of combustion on the strain rate field in turbulent jets were studied using 10kHz tomographic particle image velocimetry (TPIV). Measurements were performed in three turbulent jets: a well-studied, piloted partially-premixed methane/air jet flame, Sandia flame C, with low probability of localized extinction; a second piloted jet flame, analogous to flame C but with a reduced pilot flow rate and a high probability of localized extinction; and a non-reacting air jet. Since the jet exit Reynolds number of approximately 13000 was nearly identical in the three jets, differences in the strain rate fields were attributed to the effects of combustion. Spatiotemporal characteristics of the strain rate field were analyzed. Overall, the strain rate norm was larger in the flames than in the non-reacting jet with the most stable flame having the largest values. In all three jets, the compressive strain rate was on average the largest of the three principal strain rates. At high strain rates, the ratios of the compressive and extensive strain rate to the intermediate strain rate were similar to those found in isotropic incompressible turbulent flows. The three-dimensional velocity measurements were used to analyze the spatial distribution of strain rate clusters, defined as singly-connected groups of voxels where the strain rate magnitude exceeded a threshold value. The presence of a stable flame significantly attenuated the number of clusters of intermediate strain rate. Strain rate bursts, corresponding to sudden increases in the number of clusters, were identified in the three jets. Bursts in the non-reacting jet and the unstable flame contained up to twice as many clusters as in the stable flame. The temporal intermittency of intense strain rate clusters was analyzed using the time-series measurements. Clusters with strain rates greater than five times the standard deviation of the strain rate norm were highly intermittent.

Colonization and extinction dynamics of a declining migratory bird are influenced by climate and habitat degradation

Uncovering the mechanisms involved in the decline of long‐distance migrants remains one of the most pressing issues inEuropean conservation. Since the 1980s, theBritish breeding population ofGardenWarblerSylvia borinhas declined by more than 25%. Here we use data from repeated bird surveys of woodland sites in the 1980s and in 2003–2004 to show that, although the overall population declined between the two periods, the probability of occupancy for this species increased at high latitudes and decreased at low latitudes. Range shifts such as this arise from a change in the ratio of colonizations to extinctions at the range margins, and we therefore related colonization and local extinction at the patch level to concurrent changes in temperature and habitat. The probability of patch colonization by this species was significantly lower where the percentage cover of vegetation in the understorey had declined, reducing habitat quality for this species. The probability of local extinction was significantly correlated with increasing mean May temperature, which may reflect a change in phenology, making breeding conditions less suitable. Changed regimes of grazing and woodland management could be used to increase habitat suitability and thereby increase colonization probability at the local scale, which may in turn increase the probability of patch occupancy despite future climatic unsuitability.

Multi-season occupancy analysis reveals large scale competitive exclusion of the critically endangered European mink by the invasive non-native American mink in Spain

Understanding changes over time in the distribution of interacting native and invasive species that may be symptomatic of competitive exclusion is critical to identify the need for and effectiveness of management interventions. Occupancy models greatly increase the robustness of inference that can be made from presence/absence data when species are imperfectly detected, and recent novel developments allow for the quantification of the strength of interaction between pairs of species.We used a two-species multi-season occupancy model to quantify the impact of the invasive American mink on the native European mink in Spain through the analysis of their co-occurrence pattern over twelve years (2000–2011) in the entire Spanish range of European mink distribution, where both species were detected by live trapping but American mink were culled. We detected a negative temporal trend in the rate of occupancy of European mink and a simultaneous positive trend in the occupancy of American mink. The species co-occurred less often than expected and the native mink was more likely to become extinct from sites occupied by the invasive species. Removal of American mink resulted in a high probability of local extinction where it co-occurred with the endemic mink, but the overall increase in the probability of occupancy over the last decade indicates that the ongoing management is failing to halt its spread. More intensive culling effort where both species co-exist as well as in adjacent areas where the invasive American mink is found at high densities is required in order to stop the decline of European mink.

The emergence of the rescue effect from explicit within- and between-patch dynamics in a metapopulation

Immigration can rescue local populations from extinction, helping to stabilize a metapopulation. Local population dynamics is important for determining the strength of this rescue effect, but the mechanistic link between local demographic parameters and the rescue effect at the metapopulation level has received very little attention by modellers. We develop an analytical framework that allows us to describe the emergence of the rescue effect from interacting local stochastic dynamics. We show this framework to be applicable to a wide range of spatial scales, providing a powerful and convenient alternative to individual-based models for making predictions concerning the fate of metapopulations. We show that the rescue effect plays an important role in minimizing the increase in local extinction probability associated with high demographic stochasticity, but its role is more limited in the case of high local environmental stochasticity of recruitment or survival. While most models postulate the rescue effect, our framework provides an explicit mechanistic link between local dynamics and the emergence of the rescue effect, and more generally the stability of the whole metapopulation.

Testing metapopulation concepts: effects of patch characteristics and neighborhood occupancy on the dynamics of an endangered lagomorph

Metapopulation ecology is a field that is richer in theory than in empirical results. Many existing empirical studies use an incidence function approach based on spatial patterns and key assumptions about extinction and colonization rates. Here we recast these assumptions as hypotheses to be tested using 18 years of historic detection survey data combined with four years of data from a new monitoring program for the Lower Keys marsh rabbit. We developed a new model to estimate probabilities of local extinction and colonization in the presence of nondetection, while accounting for estimated occupancy levels of neighboring patches. We used model selection to identify important drivers of population turnover and estimate the effective neighborhood size for this system. Several key relationships related to patch size and isolation that are often assumed in metapopulation models were supported: patch size was negatively related to the probability of extinction and positively related to colonization, and estimated occupancy of neighboring patches was positively related to colonization and negatively related to extinction probabilities. This latter relationship suggested the existence of rescue effects. In our study system, we inferred that coastal patches experienced higher probabilities of extinction and colonization than interior patches. Interior patches exhibited higher occupancy probabilities and may serve as refugia, permitting colonization of coastal patches following disturbances such as hurricanes and storm surges. Our modeling approach should be useful for incorporating neighbor occupancy into future metapopulation analyses and in dealing with other historic occupancy surveys that may not include the recommended levels of sampling replication.

The roles of competition and habitat in the dynamics of populations and species distributions

The role of competition in structuring biotic communities at fine spatial scales is well known from detailed process-based studies. Our understanding of competition's importance at broader scales is less resolved and mainly based on static species distribution maps. Here, we bridge this gap by examining the joint occupancy dynamics of an invading species (Barred Owl, Strix varia) and a resident species (Northern Spotted Owl, Strix occidentalis caurina) in a 1000-km study area over a 22-year period. Past studies of these competitors have focused on the dynamics of one species at a time, hindering efforts to parse out the roles of habitat and competition and to forecast the future of the resident species. In addition, while these studies accounted for the imperfect detection of the focal species, no multi-season analysis of these species has accounted for the imperfect detection of the secondary species, potentially biasing inference. We analyzed survey data using models that combine the general multistate-multi-season occupancy modeling framework with autologistic modeling, allowing us to account for important aspects of our study system. We found that local extinction probability increases for each species when the other is present; however, the effect of the invader on the resident is greater. Although the species prefer different habitats, these habitats are highly correlated at the patch scale, and the impacts of invader on the resident are greatest in patches that would otherwise be optimal. As a consequence, competition leads to a weaker relationship between habitat and Northern Spotted Owl occupancy. Colonization and extinction rates of the invader are closely related to neighborhood occupancy, and over the first half of the study the availability of colonists limited the rate of population growth. Competition is likely to exclude the resident species, both through its immediate effects on local extinction and by indirectly lowering colonization rates as Northern Spotted Owl occupancy declines. Our analysis suggests that dispersal limitation affects both the invasion dynamics and the scale at which the effects of competition are observed. We also provide predictions regarding the potential costs and benefits of managing Barred Owl populations at different target levels.

Detection probability of the Collared Flycatcher Ficedula albicollis during quick, multiple surveys: a case study in an isolated population in northern Poland

We investigated factors affecting the detection probability of the Collared Flycatcher Ficedula albicollis, a secretive forest passerine, whose range is confined to central and eastern Europe. With a robust design sampling protocol, 78 sites were surveyed four times in spring 2012 for the presence of singing males in the Las Warmiński nature reserve (northern Poland). Multi-season occupancy models fitted to the data showed that detection probability varied considerably as a function of habitat quality. Probabilities of detection of at least one singing male during a single survey were very similar under various models: 0.383-0.419 at sites with single males, 0.815-0.837 at sites with two males, 0.970-0.974 and 0.999 at sites with three and four males. Detection probability did not depend on time of day, indicating no decline in singing activity as the day progresses. The local extinction probability was zero, suggesting that sites occupied early in the season are unlikely to be deserted - males were actively singing several days after arrival. Since mated males reduce their singing activity very much, these results may suggest low mating success. If this holds true, the colonization probability invariably estimated at 1.0 is best explained by the late arrival of some males rather, than by within-season movements of males already present. This study emphasizes that occupancy models are useful for the simultaneous investigation of the effects of multiple covariates not only on detection but also on other, biologically important parameters.

Can climate explain interannual local extinctions among bird species?

Aim Geographical variations in species richness are strongly related to temperature and precipitation. On ecological time-scales, these variations in species richness should reflect rates of immigration and local extinction (extirpation). Here we ask whether the probability of local extinction in passerine birds covaries with climate. Specifically, we test whether local extinctions increase with climatic harshness or with the climatic distance from a species' optimal climate. Location USA and Canada. Methods We obtained bird counts from the North American Breeding Bird Survey (BBS) from 1967 to 2012. For each BBS route, we calculated the probability of interannual local extinction for each of 206 passerine birds. We then used linear mixed-effects models and structural equation modelling to relate local extinction rates to our hypothesized predictor variables: temperature, precipitation and their distance from the species' most occupied temperature and precipitation. Results We found that local extinctions are nearly independent of temperature and precipitation: no climate is inherently more extinction-prone than any other. Similarly, the climatic distance from a species' maximally occupied temperature and precipitation has only an extremely weak positive effect on the probability of local extinction. We found that only abundance has a strong negative effect on the probability of local extinction. Main conclusions Although variations in local extinctions are typically spatially structured, we conclude that they are not related to contemporary climate in a consistent way among species. Broad-scale geographical gradients of species richness are unlikely to be driven by higher extinction rates in climatically harsh areas.

Determinants of extinction‐colonization dynamics inMediterranean butterflies: the role of landscape, climate and local habitat features

Many species are found today in the form of fragmented populations occupying patches of remnant habitat in human-altered landscapes. The persistence of these population networks requires a balance between extinction and colonization events assumed to be primarily related to patch area and isolation, but the contribution of factors such as the characteristics of patch and matrix habitats, the species' traits (habitat specialization and dispersal capabilities) and variation in climatic conditions have seldom been evaluated simultaneously. The identification of environmental variables associated with patch occupancy and turnover may be especially useful to enhance the persistence of multiple species under current global change. However, for robust inference on occupancy and related parameters, we must account for detection errors, a commonly overlooked problem that leads to biased estimates and misleading conclusions about population dynamics. Here, we provide direct empirical evidence of the effects of different environmental variables on the extinction and colonization rates of a rich butterfly community in the western Mediterranean. The analysis was based on a 17-year data set containing detection/nondetection data on 73 butterfly species for 26 sites in north-eastern Spain. Using multiseason occupancy models, which take into account species' detectability, we were able to obtain robust estimates of local extinction and colonization probabilities for each species and test the potential effects of site covariates such as the area of suitable habitat, topographic variability, landscape permeability around the site and climatic variability in aridity conditions. Results revealed a general pattern across species with local habitat composition and landscape features as stronger predictors of occupancy dynamics compared with topography and local aridity. Increasing area of suitable habitat in a site strongly decreased local extinction risks and, for a number of species, both higher amounts of suitable habitat and more permeable landscapes increased colonization rates. Nevertheless, increased topographic variability decreased the extinction risk of bad dispersers, a group of species with significantly lower colonization rates. Our models predicted higher sensitivity of the butterfly assemblages to deterministic changes in habitat features rather than to stochastic weather patterns, with some relationships being clearly dependent on the species' traits.

Effects of strain rate, turbulence, reactant stoichiometry and heat losses on the interaction of turbulent premixed flames with stoichiometric counterflowing combustion products

Intense strain, turbulence, heat transfer, and mixing with combustion products can affect premixed flames in practical combustion devices. These effects are systematically studied in turbulent premixed CH4/N2/O2 flames using a reactant versus product counterflow system and independently varying bulk strain rate, turbulent Reynolds number, equivalence ratio of the reactant mixture, and temperature of the stoichiometric counterflowing combustion products. The flow field and the turbulent flames are investigated using particle image velocimetry (PIV) measurements and laser-induced fluorescence (LIF) imaging of OH. The OH-LIF images are used to identify the interface between the counterflowing streams, referred to here as the gas mixing layer interface (GMLI). The flame response for different flow conditions is compared in terms of the probability of localized extinction along the GMLI, the turbulent flame brush thickness, and flame position relative to the GMLI, by using an OH-LIF-based progress variable. The probability of localized extinction at the GMLI increases as the separation between the turbulent flame brush and the GMLI decreases. Flame fronts in the vicinity of the GMLI are more likely to extinguish as a result of heat losses, dilution of the reaction zone by the product stream, and large local strain rates. A higher probability of localized extinction at the GMLI is induced by either a larger bulk strain rate or a slower flame speed. As the turbulent Reynolds number increases, the corresponding increase in turbulent flame brush thickness enhances the interactions of the flame fronts with the GMLI. Heat losses are substantially less significant for cases in which the turbulent flame brush is sufficiently separated from the GMLI. For flames in close proximity to the GMLI, the effects of the product stream on the flame front differ for lean and rich reactant mixtures. These disparities are attributed in part to differences in the ignitibility of the reactant mixtures by the hot product stream.

Climate warming increases biodiversity of small rodents by favoring rare or less abundant species in a grassland ecosystem

Our Earth is facing the challenge of accelerating climate change, which imposes a great threat to biodiversity. Many published studies suggest that climate warming may cause a dramatic decline in biodiversity, especially in colder and drier regions. In this study, we investigated the effects of temperature, precipitation and a normalized difference vegetation index on biodiversity indices of rodent communities in the current or previous year for both detrended and nondetrended data in semi-arid grassland of Inner Mongolia during 1982-2006. Our results demonstrate that temperature showed predominantly positive effects on the biodiversity of small rodents; precipitation showed both positive and negative effects; a normalized difference vegetation index showed positive effects; and cross-correlation function values between rodent abundance and temperature were negatively correlated with rodent abundance. Our results suggest that recent climate warming increased the biodiversity of small rodents by providing more benefits to population growth of rare or less abundant species than that of more abundant species in Inner Mongolia grassland, which does not support the popular view that global warming would decrease biodiversity in colder and drier regions. We hypothesized that higher temperatures might benefit rare or less abundant species (with smaller populations and more folivorous diets) by reducing the probability of local extinction and/or by increasing herbaceous food resources.

Site occupancy and spatial co-occurrence of boreal small mammals are favoured by late-decay woody debris

Dwindling stocks of decaying coarse woody debris (CWD), as a result of forest management and growing interest for biofuels, may jeopardize the persistence of a broad spectrum of organisms such as small mammals. In this study, we quantified the effects of CWD in late-decay stages on the occupancy dynamics of small mammals in managed and unmanaged boreal forests. Probabilities of initial site occupancy, colonization, local extinction, and co-occurrence were modelled for five boreal small mammal species. Southern red-backed voles (Myodes gapperi Vigor) and southern bog lemmings (Synaptomys cooperi Baird) were more likely to occupy sites with high volumes of late-decay CWD early in the summer. The probability of local extinction for deer mice (Peromyscus maniculatus Wagner) slightly decreased with an increasing volume of late-decay CWD in harvested sites. Southern red-backed voles and meadow voles (Microtus pennsylvanicus Ord) co-occurred more often in old, uncut forests, as well as harvested sites with high volumes of late-decay CWD. These results suggest that cover provided by late-decay CWD benefited two small rodent species during early reproduction and increased persistence of deer mice later in the summer. Finally, we found that in addition to high live-tree basal areas, high late-decay CWD volume also favours local diversity of small mammals.