Ilse Storch

From connectivity to isolation: genetic consequences of population fragmentation in capercaillie across Europe

The capercaillie inhabits a continuous range in large parts of the Palearctic boreal forest, but is patchily distributed in temperate Europe. An ongoing population decline, largely related to human land use changes, has been most pronounced in central and western Europe, where some local populations have become extinct. In this study, we document the genetic differentiation of capercaillie populations at different stages along a gradient of spatial structuring from high connectivity (continuous range in the boreal forest) to a metapopulation systems (Alps) and recent (central Europe) and historic (Pyrenees) isolation. Four hundred and sixty individuals from 14 sample sites were genotyped at 10 polymorphic microsatellite loci to assess genetic structure and variation of capercaillie populations across its European range. As expected, differentiation was least pronounced within the continuous range in the boreal forest. Within the metapopulation system of the Alps, differentiation was less than among the isolated populations of central Europe (Black Forest, Fichtelgebirge, Thuringia, Vosges). In the long‐isolated population of the Pyrenees, and the recently isolated populations of central Europe, genetic diversity was significantly reduced compared with the Alps and boreal forest. Our results agree with the concept of a gradual increase in genetic differentiation from connectivity to isolation, and from recent to historic isolation. Anthropogenic habitat deterioration and fragmentation thus not only leads to range contractions and extinctions, but may also have significant genetic and evolutionary consequences for surviving populations. To maintain high levels of genetic variation in species in fragmented habitats, conservation should aim at securing connectivity between spatially distinct populations.

Habitat selection by capercaillie in summer and autumn: Is bilberry important?

The use of habitat by female and male adult capercaillie Tetrao urogallus during summer and autumn was studied by comparing the distribution of radio locations of birds with the availability of habitat at forest stand, home range and landscape level in an area of the Bavarian Alps, Germany. Capercaillie preferred forests with structural features typical of their main distribution range, the boreal forest: they selected large patches of old forest with moderate canopy cover of about 50%, and a well developed field layer with high proportions of bilberry Vaccinium myrtillus. Hens selected both home ranges and sites within home ranges in old forest. Ranges selected by cocks did not differ from availability in the study area, but they preferred old forest within their ranges. The size of home ranges was negatively related to bilberry cover both in hens and cocks. The distribution of bilberry also determined habitat use by capercaillie at the landscape scale. The study demonstrated that bilberry is the major determinant of the selection of habitat by capercaillie in landscapes with sparse and fragmentary cover of ericaceous shrubs, such as central Europe.

Annual home ranges and spacing patterns of capercaillie in Central Europe

The capercaillie (Tetrao urogallus) is endangered in Central Europe; knowledge of its spatial requirements is vague but important for conservation. I radiotracked 40 capercaillie during 1988-92 in the Bavarian Alps, Germany, to study annual range use patterns and to identify habitat needs for capercaillie conservation. Annual home ranges of females (n = 7) and males (n = 19) were not different in size (P = 0.56), diameter (P = 0.41), or vegetation (P > 0.15). Home range size varied between 132 and 1,207 ha, and averaged 550 ha (SE = 52 ha). Home range size was inversely related to availability of bilberry (Vaccinium myrtillus) (P 5-year-old males were the last to leave. Movements of males to summer ranges could not be explained by food sources and may be related to predator avoidance. In the course of a year, birds of 1 lek may use a 30-50 km 2 area. Therefore, maintaining leks and habitat within 3-4 km of the lek center should be emphasized in capercaillie conservation

Capercaillie in the Alps: genetic evidence of metapopulation structure and population decline

In the Alps, the capercaillie is distributed in a metapopulation pattern with local populations on mountain ranges separated by farmland valleys. Habitat deterioration, primarily related to human land use, resulted in population declines and range contractions became obvious. At the edge of a species’ range, lower connectivity and less gene flow may render populations more susceptible to decline and extinction than in the core of the range. If this were true for the capercaillie in the Alps, edge populations should be subject to limited gene flow and should show genetic signs of a more severe population decline than core populations. To test this hypothesis, we used microsatellite DNA typing techniques. We assessed genetic variation within and among 18 local capercaillie populations across the Alps in relation to geographical distribution within the metapopulation system. All populations showed high levels of genetic variation in terms of average number of alleles, allelic richness and heterozygosity. Excess heterozygosity suggested a recent population decline, that was more pronounced in edge than core populations. We found high gene flow, but also significant differentiation among populations. Differentiation among edge populations was related to geographical distance, and appeared to be a recent process, most probably caused by reduced gene flow after population decline. In the core group, the high mountains of the central Alps seem to limit dispersal, and genetic drift was the most likely explanation for the observed differentiation among populations. We conclude that maintaining connectivity within the metapopulation system is vital for capercaillie conservation in the Alps.

Minimum viable population size of capercaillie Tetrao urogallus: results from a stochastic model

In order to estimate minimum area requirements for viable isolated populations of capercaillie Tetrao urogallus in Central Europe, we developed a stochastic population model. Model parameters were largely based on the results of a field study in the Bavarian Alps. Environmental fluctuations (amount of rainfall in June and July) are taken into account in the early survival of chicks. For the default parameter set, the model predicts a minimum capacity needed for viability, i.e. for the extinction risk not to exceed 1% in 100 years, of about 470 individuals. In the Bavarian Alps, this corresponds to area requirements of an isolated viable population in an order of magnitude of 250 km2. These results are, however, sensitive to small changes in model parameters such as female survival, clutch survival and chick survival. We conclude that minimum viable population size and minimum area requirements may vary considerably across the range of the capercaillie. Therefore, we plan to apply our model to different parameter sets from different regions in order to explore the range of conditions under which capercaillie populations may be viable.

Habitat and survival of capercaillie Tetrao urogallus nests and broods in the Bavarian alps

The capercaillie Tetrao urogallus has become endangered in central Europe, most probably as a result of habitat changes. Breeding ecology was studied by following radio-tagged hens through egg-laying, incubation, and chick-rearing between 1988 and 1992. Loss of chicks rather than nests was the main determinant of reproductive success. All adult hens incubated, two-thirds of the nests hatched, and one-fifth of the chicks survived until autumn. Both nests and broods were mostly found in habitats with rich ground vegetation. Nest cover was probably a major factor for hatching success. Brood home ranges averaged 148 ha during the period from hatching to late summer. Broods preferred old forest stands with rich ground vegetation and high invertebrate abundance, which occur under moderate canopy cover. Bilberry Vaccinium myrtillus was an essential feature for brood habitat at forest stand, home range, and landscape scale, and should therefore be a major goal for capercaillie habitat management in central Europe.

Genetic Correlates of Spatial Population Structure in Central European Capercaillie Tetrao urogallus and Black Grouse T. tetrix: A Project in Progress

Capercaillie Tetrao urogallus and black grouse T. tetrix are threatened species in central Europe. Their habitats are fragmented both at a continental and a regional scale, and spatial connectivity may play an important role for their (meta-)population dynamics and persistence. In order to identify conservation priorities, it is important to know if and to what extent exchange between local populations occurs. In this paper, we present the rationale and techniques of an ongoing project into the spatial structure of capercaillie and black grouse populations in central Europe using non-invasive genetic methods. In this project, we assess the genetic differentiation of spatially distinct populations using microsatellite analysis based on DNA extracted from feathers. This approach will allow us to identify critical geographic distances beyond which demographic connectivity between populations is not assured. We expect to find a correlation between geographic and genetic distance.

Comparative range use by three Atlantic Forest understorey bird species in relation to forest fragmentation

In this paper, we report on range use patterns of birds in relation to tropical forest fragmentation. Between 2003 and 2005, three understorey passerine species were radio-tracked in five locations of a fragmented and in two locations of a contiguous forest landscape on the Atlantic Plateau of Sao Paulo in south-eastern Brazil. Standardized ten-day home ranges of 55 individuals were used to determine influences of landscape pattern, season, species, sex and age. In addition, total observed home ranges of 76 individuals were reported as minimum measures of spatial requirements of the species. Further, seasonal home ranges of recaptured individuals were compared to examine site fidelity. Chiroxiphia caudata, but not Pyriglena leucoptera or Sclerurus scansor, used home ranges more than twice as large in the fragmented versus contiguous forest. Home range sizes of C. caudata differed in relation to sex, age, breeding status and season. Seasonal home ranges greatly overlapped in both C. caudata and in S. scansor. Our results suggest that one response by some forest bird species to habitat fragmentation entails enlarging their home ranges to include several habitat fragments, whereas more habitat-sensitive species remain restricted to larger forest patches.

META-X: Generic Software for Metapopulation Viability Analysis

The major tools used to make population viability analyses (PVA) quantitative are stochastic models of population dynamics. Since a specially tailored model cannot be developed for every threatened population, generic models have been designed which can be parameterised and analysed by non-modellers. These generic models compromise on detail so that they can be used for a wide range of species. However, generic models have been criticised because they can be employed without the user being fully aware of the concepts, methods, potentials, and limitations of PVA. Here, we present the conception of a new generic software package for metapopulation viability analysis, META-X. This conception is based on three elements, which take into account the criticism of earlier generic PVA models: (1) comparative simulation experiments; (2) an occupancy-type model structure which ignores details of local population dynamics (these details are integrated in external submodels); and (3) a unifying currency to quantify persistence and viability, the ‘intrinsic mean time to extinction’. The rationale behind these three elements is explained and demonstrated by exemplary applications of META-X in the three fields for which META-X has been designed: teaching, risk assessment in the field, and planning. The conception of META-X is based on the notion that PVA is a tool to deal with rather than to overcome uncertainty. The purpose of PVA is to produce relative, not absolute, assessments of extinction risk which support, but do not supplant, management decisions.

Meta‐analysis: A need for well‐defined usage in ecology and conservation biology

Meta-analysis is a powerful research summarization technique. In the medical field, for example, meta-analysis is an indispensable tool as part of systematic reviews for healthcare decision making. The advantages of meta-analysis have also been recognized in the fields of ecology and conservation biology with the method becoming increasingly popular since the 1990s. “Meta-analysis”, however, is not well-defined in these fields, but is regularly confused with other summary analysis techniques, such as multiple regression methods, vote-counting or other quantitative analyses. We argue that this vague and inconsistent utilization of the term is problematic, because a meta-analysis typically provides scientifically rigorous results. We therefore advocate a consistent and well-defined usage of the term in our disciplines, based on the standardized definition applied in the medical sciences. We searched the Web of Knowledge for meta-analyses in the subject area “biodiversity conservation” and evaluated the usage of the term “meta-analysis”. Based on meta-analysis literature from the medical sciences, we determined steps that in our opinion are mandatory when performing meta-analysis and rated articles according to these steps. In the first round of rating, we assessed the usage of four “technical” steps that are normally applied in meta-analytical software. In the second round, we only evaluated the highly rated articles from the first round. We considered three steps regarding more qualitative aspects of interpretation and results presentation. Of the 133 evaluated articles in the first round, only 45% fulfilled all technical requirements for a meta-analysis, while 25% did not fulfill any of the requisite steps. In the second round, only one article of 83 fulfilled all requisite steps, while 22% did not fulfill any requirement. Our findings highlight the ambiguous and vague usage of the term “meta-analysis” in ecology and conservation biology and underline the importance of a consistent and clear definition. We conclude with recommendations on how the term should be applied in the future.