Genetic diversity, structure and conservation of the endangered Cantabrian Capercaillie in a unique peripheral habitat

Populations at the rear edge of the species’ range are often at a high risk of extinction due to their isolation, fragmentation and small population sizes. However, these populations also play a relevant role in the conservation of biodiversity since they may represent a valuable genetic resource. The endangered Cantabrian Capercaillie (Tetrao urogallus cantabricus) inhabits deciduous forests of the Cantabrian Mountains of Spain, at the southwestern limit of the species’ range. Recently, nine Cantabrian Capercaillie leks were discovered in Pyrenean oak forests of the southern slope of the Cantabrian range, where the subspecies historically occurred. To elucidate if the origin of this peripheral population nucleus is the result of a historical range contraction or a recent re-colonization from the core population, we sampled moulted feathers from all the known leks in the southern peripheral forests and from the adjacent main core population, based on nine microsatellite loci genotypes. No significant genetic differentiation was detected between main core and peripheral forests suggesting that gene flow is not interrupted between these nuclei. Contrary to expected, peripheral forests did not represent sink populations, since gene flow mainly occurred from southern peripheral to northern main core forests. Therefore, the origin of these birds inhabiting the peripheral nucleus seems not to be a recent colonization but relicts from the former distribution range that have remained unnoticed in a drier and warmer environment than described so far for the species. Cantabrian Capercaillie faces a high risk of extinction in the southernmost forests of its distribution, not only because of its peripheral location but also due to its small population size, low genetic diversity and low incoming gene flow. According to our results, this peripheral nucleus could represent an expanding edge for the population if Pyrenean oak forests continue to spread out southwards and consequently stress the need for conservation programs to preserve habitat availability and forest connectivity.     

The Mediterranean Quercus pyrenaica oak forest: a new habitat for the Capercaillie?

We described an extension of the known distribution range of the Cantabrian Capercaillie Tetrao urogallus cantabricus into an atypical area and habitat for the species. Nine Capercaillie leks and 14 cocks were registered in Mediterranean Quercus pyrenaica forests in an area of 1,500 km², of which 4,500 forest hectares were surveyed. At present, this population represents both the southern-most distribution for Capercaillie and the only one inhabiting Mediterranean Q. pyrenaica forests, what suggests a wider adaptation of this (sub)species than previously thought. This population and its habitat need to be better studied, as well as to be considered in conservation planning for Cantabrian Capercaillie.     

Habitat selection and diet of the Capercaillie Tetrao urogallus in Abernethy Forest,Strathspey, Scotland

Capsule Woodland characteristics are important for fully grown birds and for broods.

Aims To describe habitat selection and diet of the Capercaillie in ancient native pinewoods and Scots Pine Pinus sylvestris plantations, in order to provide a guide for forest management.

Methods Tree selection was studied in winter by locating droppings under trees along transects, and comparing those trees used by Capercaillie with those not used. Habitat selection by broods was studied by following radiotagged chicks or females with broods. Diet was described from the analysis of droppings.

Results In winter, Capercaillie preferred Scots Pines with wide crowns and large branches, and little surrounding Heather Calluna vulgaris, but avoided forest tracks. Female Capercaillie occurred in stands with a higher density of pines compared to males. The diet of fully grown birds comprised primarily Scots Pine needles between October and April. Scots Pine pollen cones were eaten during May, June and July. Bilberry Vaccinium myrtillus leaves and fruit were eaten in summer and autumn. Habitats used by broods had a higher percentage of Vaccinium sp. and smaller Scots Pines compared with random sites. Chicks hatch at the beginning of June, and in their first two weeks, their diet comprised Formicidae, Lepidoptera larvae and Coleoptera. In July and August, Lepidoptera larvae were rarely eaten but a higher percentage of chicks took vegetable material (particularly Bilberry fruit). In June, smaller numbers of invertebrates were generally trapped in mires of wooded bogs compared with areas of Heather and Vaccinium sp. in old woodland. Areas of Vaccinium sp. had the highest numbers of Formicidae, Coleoptera and Diptera, and especially Lepidoptera larvae. Numbers of Lepidoptera larvae declined during June and July as larvae pupated, explaining the reduction of Lepidoptera larvae in the diet of older chicks.

Conclusions Habitat management for Capercaillie should aim to provide old Scots Pine forest with a Vaccinium-rich field layer. Within Scotland, this may entail increasing the tree density in ancient native pinewoods but decreasing it in pine plantations. The removal or closure of tracks might increase the amount of woodland available to Capercaillie, by reducing human disturbance.     

Genetic differentiation of an endangered capercaillie (<Emphasis Type="Italic">Tetrao urogallus</Emphasis>) population at the Southern edge of the species range

The low-latitude limits of species ranges are thought to be particularly important as long-term stores of genetic diversity and hot spots for speciation. The Iberian Peninsula, one of the main glacial refugia in Europe, houses the southern distribution limits of a number of boreal species. The capercaillie is one such species with a range extending northwards to cover most of Europe from Iberia to Scandinavia and East to Siberia. The Cantabrian Range, in North Spain, constitutes the contemporary south-western distribution limit of the species. In contrast to all other populations, which live in pure or mixed coniferous forests, the Cantabrian population is unique in inhabiting pure deciduous forests. We have assessed the existence of genetic differentiation between this and other European populations using microsatellite and mitochondrial DNA (mtDNA) extracted from capercaillie feathers. Samples were collected between 2001 and 2004 across most of the current distribution of the Cantabrian population. Mitochondrial DNA analysis showed that the Cantabrian birds form a distinct clade with respect to all the other European populations analysed, including the Alps, Black Forest, Scandinavia and Russia, which are all members of a discrete clade. Microsatellite DNA from Cantabrian birds reveals the lowest genetic variation within the species in Europe. The existence of birds from both mtDNA clades in the Pyrenees and evidence from microsatellite frequencies for two different groups, points to the existence of a Pyrenean contact zone between European and Cantabrian type birds. The ecological and genetic differences of the Cantabrian capercaillies qualify them as an Evolutionarily Significant Unit and support the idea of the importance of the rear edge for speciation. Implications for capercaillie taxonomy and conservation are discussed.     

Capercaillie Tetrao urogallus abundance and habitat use in Scotland,in winter 1998–99

CapsuleA second full survey in which we estimate the population at 1073 birds (95% CL 549–2041).

Aims To provide an up-to-date estimate of the population size of Capercaillie in Britain and to identify habitat use by Capercaillie in winter.

Methods Using the census technique of distance sampling, flushed birds were counted along line transects walked in stratified random blocks of forest within the species' range. The same transects were surveyed as used in the 1992–94 survey, enabling direct comparison of the results. Densities were estimated using the DISTANCE program, combining these data with those from a similar survey of Capercaillie in 1992–94 to allow a more robust estimate of the detection function.

Results The Capercaillie population was estimated to be 1073 birds (95% CL 549–2041). This represents a decline of 51% between the two surveys, at a rate of 13% per annum. Females declined at a faster rate than males resulting in a marked change in the sex-ratio, which was close to 1:1 for the entire population. Bird densities declined by a similar magnitude in both native pinewoods and other woodlands in comparison to 1992–94. Even so, densities were significantly higher in native pinewoods (1.63 km^-2) than in other woodlands (0.43 km^-2), which comprised largely planted Scots Pine Pinus sylvestris, larch Larix spp., Lodgepole Pine Pinus contorta and Sitka Spruce Picea sitchensis. Overall, Capercaillie tended to use forest stands with a high proportion of Scots Pine and Blaeberry Vaccinium myrtilus; features that are typical of native pinewoods and old pine plantations.

Conclusions The Capercaillie population has undergone a dramatic decline during the last five years. The decline has been greater for females and has occurred across habitats. This information is helping to focus efforts in securing the future for Capercaillie in Scotland, which has now become a major conservation challenge.     

The European Pine Marten Martes martes in the Balearic Islands, Spain

Between March and December 1990, a survey of Pine Marten Martes martes L. on the Balearic Islands of Minorca and Majorca was carried out. Pine Marten were found distributed over 55% of Minorca and occupied Aleppo Pine and Holm Oak forests, mediterranean shrublands and riparian/ cliff habitats. In Majorca, Pine Marten were found on 48% of the island and three broad physiographic areas, the Sierra de Tramuntana, Sierra de Levant and the Massif de Randa. Droppings were collected along four designated routes during five bimonthly intervals in Minorca to describe the Pine Marten's differential use of habitat types. The upland/open pine forest had the highest use index while the Holm Oak forest had the lowest. The number of Pine Marten faeces collected was greatest during the months of July-August. The Balearic Island Pine Marten populations were once on the verge of extinction; however, protection during the last 20 years has enabled the species to recover throughout most of the forested habitats on both islands. Resource managers must carefully monitor the Pine Marten populations to provide the species and its habitat with adequate protection and management in the future.     

Some butterflies do not care much about topography: a single genetic lineage of Erebia euryale (Nymphalidae) along the northern Iberian mountains

The phylogeography of montane species often reveals strong genetic differentiation among mountain ranges. Both classic morphological and genetic studies have indicated distinctiveness of Pyrenean populations of the butterfly Erebia euryale. This hypothesis remained inconclusive until data from the westernmost populations of the distribution area (Cantabrian Mountains) were analysed. In the present study, we set out to describe the population structure of Erebia euryale in western Cantabria, where the species occurs in scattered localities. For this goal, we estimate the genetic diversity and differentiation found in 218 individuals from six Cantabrian (North Spain) localities genotyped by 17 allozyme loci. We also sequence 816 bp of the cytochrome oxidase subunit I mitochondrial gene in 49 individuals from Cantabrian localities and 41 specimens from five other European sites. Mitochondrial data support the recognition of four major genetic groups previously suggested for the European populations based on allozyme polymorphisms. Both mitochondrial and nuclear markers reveal genetic distinctiveness of a single Pyrenean–Cantabrian lineage of E. euryale. The lack of geographical structure and the star‐like topology displayed by the mitochondrial haplotypes indicate a pattern of demographic expansion in northern Iberia, probably related to Upper Pleistocene climatic oscillations. By contrast, within the Pyrenean–Cantabrian lineage, Cantabrian samples are genetically structured in nuclear datasets. In particular, San Isidro is significantly differentiated from the other five populations, which cluster into two groups. We recognize an evolutionary significant unit for Pyrenean–Cantabrian populations of Erebia euryale. Our results also illustrate that the evolutionary history of a species may be shaped by processes undetectable by using mtDNA alone.     

Winter tourism increases stress hormone levels in the Capercaillie Tetrao urogallus

Montane and alpine habitats in Europe remained relatively undisturbed until the beginning of the last century. Today, outdoor recreation activities are a major economic factor in alpine regions. Many tourism areas coincide with winter habitats of shy and endangered species. The Western Capercaillie Tetrao urogallus has suffered from rapid population declines during recent decades over much of its range. In central Europe, many Capercaillie are exposed to intensive human recreation activities in their habitats, which may contribute to this decline. However, little is known about their susceptibility to human recreation activities. This study assessed whether human recreation in winter evokes physiological stress responses in several populations of Capercaillie. During two winters, we sampled 1130 Capercaillie droppings in Germany and Switzerland of populations at various distances from winter recreation activities and measured concentrations of faecal corticosterone metabolites. Capercaillie in relatively dense and homogeneous mountain forests dominated by Norway Spruce Picea abies showed markedly increased stress hormone levels closer to locations with winter recreation activity. However, this physiological response to human recreation was not detectable in forests dominated by various pine species and a heterogeneous structure. Capercaillie may be particularly sensitive to recreation because any factor affecting their fine‐tuned physiological and behavioural adaptations to survive under harsh winter conditions may lead to harmful fitness costs.     

Applying a continua landscape approach to evaluate plant response to fragmentation: Primula vulgaris in the Cantabrian mountains

Question: Continua landscape approaches conceptualize the effects of habitat fragmentation on the biota by considering fragmented landscapes as continuous gradients, departing from the view of habitat as either suitable (fragment) or unsuitable (matrix). They also consider the ecological gradients or the ‘Umwelt’ (species‐specific perception of the landscape) to represent the processes that ultimately limit organisms' ability to colonize and persist within habitat remnants. Are these approaches suitable for evaluating the response of plant species to fragmentation? Location: Fragmented mid‐elevation temperate forests, Cantabrian range, Spain. Methods: The presence, abundance and demographic structure of populations of the perennial herb Primula vulgaris were sampled across a continuous extent of 100 ha, subdivided into 400 50 m × 50 m sampling units. These variables were related to forest availability, forest subdivision and edge density, topography and the spatial clumpiness of populations (a measure of plant dispersal constraints and, hence, a major surrogate of plant Umwelt). Results: Fragmentation processes, especially habitat loss, negatively affect P. vulgaris, with a stronger effect on presence than on abundance and demography. Despite the importance of habitat availability, P. vulgaris does not occupy all potentially suitable forest habitat, mostly owing to dispersal constraints. A positive effect of slope on plant presence also suggests some effect of habitat quality in determining establishment and occupancy of forest landscape. Conclusions: Within‐habitat dispersal constraints are as important as forest fragmentation in determining the landscape‐scale distribution of P. vulgaris. By assessing the relative role of the diverse fragmentation processes, and of the species' landscape perception, a continua landscape approach proves to be a valuable tool for predicting plant response to landscape change.     

Diet and habitat selection in Cantabrian Capercaillie (Tetrao urogallus cantabricus): ecological differentiation of a rear-edge population

Cantabrian capercaillie Tetrao urogallus cantabricus is a peripheral population with distinctive phenotypic, biogeographic, and genetic characteristics. Hence, the population may also show substantial ecological differentiation associated with its habitat in purely deciduous forests. We assessed seasonal diet selection, small-scale habitat selection, and patterns of trophic niche width in Cantabrian capercaillie over two years. Diet was found to be a driver of small-scale habitat selection, a result consistent with previous studies of stand-scale habitat selection. Diet and habitat selection showed the importance of beech Fagus sylvatica, holly Ilex aquifolium, bilberry Vaccinium myrtillus, and ferns in Cantabrian capercaillie’s resource selection. Conversely, the abundant oaks Quercus petraea, birches Betula pubescens, and heaths Erica sp. were used below their availability. The reliance on bilberry appears as a unifying characteristic between central and peripheral capercaillie populations. Cantabrian capercaillie showed stronger reliance on understory resources than range-central populations. It also showed wider trophic niche and higher specialization of feeding events. Trophic niche patterns and reliance on ground resources indicated a marked ecological differentiation, which stresses the need for local data and specific conservation actions.     

Assessing forest vulnerability to climate warming using a process‐based model of tree growth: bad prospects for rear‐edges

Growth models can be used to assess forest vulnerability to climate warming. If global warming amplifies water deficit in drought‐prone areas, tree populations located at the driest and southernmost distribution limits (rear‐edges) should be particularly threatened. Here, we address these statements by analyzing and projecting growth responses to climate of three major tree species (silver fir, Abies alba; Scots pine, Pinus sylvestris; and mountain pine, Pinus uncinata) in mountainous areas of NE Spain. This region is subjected to Mediterranean continental conditions, it encompasses wide climatic, topographic and environmental gradients, and, more importantly, it includes rear‐edges of the continuous distributions of these tree species. We used tree‐ring width data from a network of 110 forests in combination with the process‐based Vaganov–Shashkin‐Lite growth model and climate–growth analyses to forecast changes in tree growth during the 21st century. Climatic projections were based on four ensembles CO₂ emission scenarios. Warm and dry conditions during the growing season constrain silver fir and Scots pine growth, particularly at the species rear‐edge. By contrast, growth of high‐elevation mountain pine forests is enhanced by climate warming. The emission scenario (RCP 8.5) corresponding to the most pronounced warming (+1.4 to 4.8 °C) forecasted mean growth reductions of ?10.7% and ?16.4% in silver fir and Scots pine, respectively, after 2050. This indicates that rising temperatures could amplify drought stress and thus constrain the growth of silver fir and Scots pine rear‐edge populations growing at xeric sites. Contrastingly, mountain pine growth is expected to increase by +12.5% due to a longer and warmer growing season. The projections of growth reduction in silver fir and Scots pine portend dieback and a contraction of their species distribution areas through potential local extinctions of the most vulnerable driest rear‐edge stands. Our modeling approach provides accessible tools to evaluate forest vulnerability to warmer conditions.     

Habitat partitioning in endangered Cantabrian capercaillie Tetrao urogallus cantabricus

The endangered Cantabrian capercaillie (Tetrao urogallus cantabricus) lives at the southern edge of tetraonids’ distribution range, in entirely deciduous forests. Its conservation planning has been always lek-centred. There is very little information about the specific habitat requirements of hens and broods, even though reproductive success appears to be a limiting factor. We analysed summer surveys from 1997 to 2004, carried out to estimate the reproductive success of the population. We compared the habitat characteristics at different spatial scales of hens with broods, broodless hens, and cocks in summer, with the better known spring habitat in display areas. Summer habitat showed higher proportion of open areas and was associated with more rugged zones at moderate spatial scales (78 ha) than spring habitat at display areas. Cocks and hens showed summer habitat partitioning; hens were associated with higher proportions of open and shrubby habitats. Furthermore, broodless hens preferred areas with higher slope variability than the display and summer areas preferred by cocks. These differences may reflect the sexual dimorphism of the species in reproductive role, energetic demands and conspicuousness. At larger spatial scales a previously developed habitat suitability model performed well to predict good brood-rearing areas. Hens with broods were located in the best-preserved areas in the range, mainly characterized by higher proportion of forest cover at a large (50 km²) scale. We suggest that these characteristics indicate refuge habitats where Cantabrian capercaillie can still breed successfully.     

The legacy of ice ages in mountain species: post‐glacial colonization of mountain tops rather than current range fragmentation determines mitochondrial genetic diversity in an endemic Pyrenean rock lizard

Aim The genetic impact of Quaternary climatic fluctuations on mountain endemic species has rarely been investigated. The Pyrenean rock lizard (Iberolacerta bonnali) is restricted to alpine habitats in the Pyrenees where it exhibits a highly fragmented distribution between massifs and between habitats within massifs. Using mitochondrial DNA markers, we set out: (1) to test whether several evolutionary units exist within the species; (2) to understand how the species persisted through the Last Glacial Maximum and whether the current range fragmentation originates from distribution shifts after the Last Glacial Maximum or from more ancient events; and (3) to investigate whether current mitochondrial diversity reflects past population history or current habitat fragmentation. Location The Pyrenees in south‐western France and northern Spain. Methods We used variation in the hypervariable left domain of the mitochondrial control region of 146 lizards collected in 15 localities, supplemented by cytochrome b sequences downloaded from GenBank to cover most of the species’ distribution range. Measures of population genetic diversity were contrasted with population isolation inferred from topography. Classical (F‐statistics) and coalescence‐based methods were used to assess the level of gene flow and estimate divergence time between populations. We used coalescence‐based simulations to test the congruence of our genetic data with a scenario of simultaneous divergence of current populations. Results Coalescence‐based analyses suggested that these peripheral populations diverged simultaneously at the end of the last glacial episode when their habitats became isolated on mountain summits. High mitochondrial diversity was found in peripheral, isolated populations, while the populations from the core of the species’ range were genetically impoverished. Where mitochondrial diversity has been retained, populations within the same massif exhibited high levels of genetic differentiation. Main conclusions As suggested for many other mountain species, the Pyrenean rock lizard survived glacial maxima through short‐distance range shifts instead of migration or contraction in distant southern refugia. Most of the main Pyrenean range has apparently been re‐colonized from a single or a few source populations, resulting in a loss of genetic diversity in re‐colonized areas. As a result, current levels of intra‐population mitochondrial diversity are better explained by post‐glacial population history than by current habitat fragmentation. Genetic population differentiation within massifs implies severe reduction in female‐mediated gene flow between patches of habitats.     

Habitat fragmentation in forests affects relatedness and spatial genetic structure of a native rodent,Rattus lutreolus

Habitat fragmentation can have a range of negative demographic and genetic impacts on disturbed populations. Dispersal barriers can be created, reducing gene flow and increasing population differentiation and inbreeding in isolated habitat remnants. Aggregated retention is a form of forestry that retains patches of forests as isolated island or connected edge patches, with the aim of ‘lifeboating’ species and processes, retaining structural features and improving connectivity. Swamp rats (Rattus lutreolus) are a cover‐dependent species that are sensitive to habitat removal. We examined the effects of aggregated retention forestry and forestry roads in native wet Eucalyptus forests on swamp rat gene flow and population genetic structure. We characterized neighbourhood size in unlogged forest to provide a natural state for comparison, and examined population structure at a range of spatial scales, which provided context for our findings. Tests of pairwise relatedness indicated significant differentiation between island and edge populations in aggregated retention sites, and across roads in unlogged sites. Spatial autocorrelation suggested a neighbourhood size of 42–55 m and revealed male‐biased dispersal. We found no genetic isolation by geographical distance at larger (>2.3 km) scales and populations were all significantly differentiated. Our results suggest that removal of mature forest creates barriers for swamp rat dispersal. In particular, roads may have long‐term impacts, while harvesting of native forests is likely to create only short‐term dispersal barriers at the local scale, depending on the rate of regeneration.     

Preliminary results on snow surveys of Pyrenean grey partridge (<Emphasis Type="Italic">Perdix perdix hispaniensis</Emphasis>) in the Cantabrian Mountains

Peripheral populations tend to be smaller and more prone to extinction than those in core areas. Grey partridge Perdix perdix in its southern-most edge occupies mountain habitats, which is unlike any habitat in its northern European range. This makes these mountain ecotypes especially susceptible to range contractions and population decrease is likely the result of the current global change process. In Iberia, the so-called Pyrenean grey partridge subspecies P. p. hispaniensis is considered to be declining but little is known about its real trends and numbers. We locally studied the abundance of the Pyrenean grey partridges in winter by direct observations in the Cantabrian Mountains (NW Spain), while driving on a paved road. In addition, we related observed partridge abundances to different context variables to find the ones better helping to detect this species. The paved road-based censuses were successful, and we detected the presence and abundance of the Pyrenean grey partridge. Individuals and groups were more easily detected from December to February while couples were observed at the end of the winter (i.e. February–March). Wherever open paved roads exist, we strongly recommend using direct observations from them during winter as an adequate tool for Pyrenean grey partridge monitoring. This easy and cost-effective method affordable to managers and conservationists can contribute to a better understanding of the European mountain’s changing ecosystems and help us understanding the population trends of this vulnerable subspecies.     

Greater growth stability of trees in marginal habitats suggests a patchy pattern of population loss and retention in response to increased drought at the rear edge

Species rear range edges are predicted to retract as climate warms, yet evidence of population persistence is accumulating. Accounting for this disparity is essential to enable prediction and planning for species’ range retractions. At the Mediterranean edge of European beech‐dominated temperate forest, we tested the hypothesis that individual performance should decline at the limit of the species’ ecological tolerance in response to increased drought. We sampled 40 populations in a crossed factor design of geographical and ecological marginality and assessed tree growth resilience and decline in response to recent drought. Drought impacts occurred across the rear edge, but tree growth stability was unexpectedly high in geographically isolated marginal habitat and lower than anticipated in the species’ continuous range and better‐quality habitat. Our findings demonstrate that, at the rear edge, range shifts will be highly uneven and characterised by reduction in population density with local population retention rather than abrupt range retractions.     

Reintroducing capercaillie (Tetrao urogallus) into southern Scotland: identification of minimum viable populations at potential release sites

Capercaillie (Tetrao urogallus) populations are declining in western parts of their range, including Scotland. It has been proposed that their numbers, and the extent of their range in Scotland be increased to reduce the risk of a second extinction in the UK. The feasibility of a reintroduction of capercaillie to coniferous plantations in southern Scotland was assessed by undertaking a population viability analysis. Following a review of capercaillie ecology and habitat requirements, VORTEX population simulation software was used to identify a minimum viable population (MVP). From this the minimum dynamic area of suitable habitat required in order to support such a MVP was then calculated. It was estimated that a minimum of 60 individuals would be required in approximately 5000ha of habitat in order for the population to have a >0.95 probability of surviving for 50 years. Supplementation of populations with two unrelated individuals every five years reduced the MVP to ten individuals. Further simulations were run in order to establish the sensitivity of the model to changes in three key parameters. Assessment of areas of suitable habitat identified two potential release sites, Wauchope and Newcastleton forests, in southern Scotland. Some practical considerations relating to management of a release population are outlined. It was concluded that an appropriately planned and resourced reintroduction was feasible.     

Driving factors of a vegetation shift from Scots pine to pubescent oak in dry Alpine forests

An increasing number of studies have reported on forest declines and vegetation shifts triggered by drought. In the Swiss Rhone valley (Valais), one of the driest inner‐Alpine regions, the species composition in low elevation forests is changing: The sub‐boreal Scots pine (Pinus sylvestris L.) dominating the dry forests is showing high mortality rates. Concurrently the sub‐Mediterranean pubescent oak (Quercus pubescens Willd.) has locally increased in abundance. However, it remains unclear whether this local change in species composition is part of a larger‐scale vegetation shift. To study variability in mortality and regeneration in these dry forests we analysed data from the Swiss national forest inventory (NFI) on a regular grid between 1983 and 2003, and combined it with annual mortality data from a monitoring site. Pine mortality was found to be highest at low elevation (below 1000 m a.s.l.). Annual variation in pine mortality was correlated with a drought index computed for the summer months prior to observed tree death. A generalized linear mixed‐effects model indicated for the NFI data increased pine mortality on dryer sites with high stand competition, particularly for small‐diameter trees. Pine regeneration was low in comparison to its occurrence in the overstorey, whereas oak regeneration was comparably abundant. Although both species regenerated well at dry sites, pine regeneration was favoured at cooler sites at higher altitude and oak regeneration was more frequent at warmer sites, indicating a higher adaptation potential of oaks under future warming. Our results thus suggest that an extended shift in species composition is actually occurring in the pine forests in the Valais. The main driving factors are found to be climatic variability, particularly drought, and variability in stand structure and topography. Thus, pine forests at low elevations are developing into oak forests with unknown consequences for these ecosystems and their goods and services.     

Land use influences harvestman diversity in northern Spain: a case study involving secondary grasslands and forest plantations (Arachnida: Opiliones)

Harvestmen have a general distribution pattern with more species and higher abundance in forests than in open habitats, as previously verified in mountain Cantabrian areas of northern Spain, of the Orocantabrian Province. The study of harvestmen of the low Cantabrian areas of the adjacent biogeographic Cantabro-Atlantic Province is highly appropriate to determine the influence of biogeographic position on the main diversity parameters and the effect of different land uses on harvestman assemblages. The main types of managed habitats (forest plantations and secondary grasslands), together with natural forests, non-planted young forests, shrublands and habitat boundaries were continuously sampled with seven pitfall traps during 1 year at 28 sites. The harvestman assemblages were classified using six different analyses, and indicator species were identified. The spatial patterns of harvestman diversity in low areas differed from those of mountain areas, although they have 15 species in common. Remarkably, higher average harvestman species richness was measured in low Cantabrian areas than in mountain areas. Shrublands and boundaries were the most species-rich habitats. Forested areas were the poorest in abundance, and were not the habitats richest in harvestman species, though they had higher average richness than mountain Cantabrian forests. Grasslands had a unique harvestman composition with significant extraordinary abundances, in particular of Homalenotus quadridentatus (indicator species of this habitat) and H. laranderas. Interestingly, H. laranderas, Paroligolophus agrestis and Ischyropsalis hispanica, indicator species of some open habitats in low Cantabrian areas, have recently been shown to be indicators of shady forests in mountain Cantabrian territories.     

Identifying refugia from climate change using coupled ecological and genetic data in a transitional Mediterranean‐temperate tree species

Populations occurring in areas of overlap between the current and future distribution of a species are particularly important because they can represent “refugia from climate change”. We coupled ecological and range‐wide genetic variation data to detect such areas and to evaluate the impacts of habitat suitability changes on the genetic diversity of the transitional Mediterranean‐temperate tree Fraxinus angustifolia. We sampled and genotyped 38 natural populations comprising 1006 individuals from across Europe. We found the highest genetic diversity in western and northern Mediterranean populations, as well as a significant west to east decline in genetic diversity. Areas of potential refugia that correspond to approximately 70% of the suitable habitat may support the persistence of more than 90% of the total number of alleles in the future. Moreover, based on correlations between Bayesian genetic assignment and climate, climate change may favour the westward spread of the Black Sea gene pool in the long term. Overall, our results suggest that the northerly core areas of the current distribution contain the most important part of the genetic variation for this species and may serve as in situ macrorefugia from ongoing climate change. However, rear‐edge populations of the southern Mediterranean may be exposed to a potential loss of unique genetic diversity owing to habitat suitability changes unless populations can persist in microrefugia that have facilitated such persistence in the past.