Evidence for different drivers behind long-term decline and depression of density in cyclic voles

Decline and long-term depression of mean densities of the grey-sided vole (Myodes rufocanus) and the field vole (Microtus agrestis) have occurred in managed forest landscapes of Sweden since the 1970s. Generally poor over-winter survival during a period with mild winters suggested a common climatic driver, but other explanations exist. Here we explore the response of the grey-sided vole, preferring forested habitats, and the field vole, preferring open habitats, to clear-cutting of old forest in Sweden. The cumulated impact from long-term clear-cutting explained local disappearances of the grey-sided vole. Maintained connectivity of old forest to stone fields was important for local population survival, since no such populations disappeared. For the grey-sided vole, it is probable that climate is not the dominating driver due to different timing of the decline in our study area. Instead, habitat loss is concluded as being a potential cause of the decline in mean density and depression of grey-sided vole densities. The long-lasting depression of field vole densities, despite favourable landscape changes, suggests action of another strong driver. A recent field vole recovery, essentially back to pre-decline densities and distribution, coincided with favourable winter/snow conditions, suggesting a climatic driver in this case.     

Dampening of population cycles in voles affects small mammal community structure,decreases diversity,and increases prevalence of a zoonotic disease

Long‐term decline and depression of density in cyclic small rodents is a recent widespread phenomenon. These observed changes at the population level might have cascading effects at the ecosystem level. Here, we assessed relationships between changing boreal landscapes and biodiversity changes of small mammal communities. We also inferred potential effects of observed community changes for increased transmission risk of Puumala virus (PUUV) spread, causing the zoonotic disease nephropatica epidemica in humans. Analyses were based on long‐term (1971–2013) monitoring data of shrews and voles representing 58 time series in northern Sweden. We calculated richness, diversity, and evenness at alpha, beta, and gamma level, partitioned beta diversity into turnover (species replacement) and nestedness (species addition/removal), used similarity percentages (SIMPER) analysis to assess community structure, and calculated the cumulated number of PUUV‐infected bank voles and average PUUV prevalence (percentage of infected bank voles) per vole cycle. Alpha, beta, and gamma richness and diversity of voles, but not shrews, showed long‐term trends that varied spatially. The observed patterns were associated with an increase in community contribution of bank vole (Myodes glareolus), a decrease of gray‐sided vole (M. rufocanus) and field vole (Microtus agrestis) and a hump‐shaped variation in contribution of common shrew (Sorex araneus). Long‐term biodiversity changes were largely related to changes in forest landscape structure. Number of PUUV‐infected bank voles in spring was negatively related to beta and gamma diversity, and positively related to turnover of shrews (replaced by voles) and to community contribution of bank voles. The latter was also positively related to average PUUV prevalence in spring. We showed that long‐term changes in the boreal landscape contributed to explain the decrease in biodiversity and the change in structure of small mammal communities. In addition, our results suggest decrease in small mammal diversity to have knock‐on effects on dynamics of infectious diseases among small mammals with potential implications for disease transmission to humans.     

THE EFFECT OF SERPENTINE ON THE POPULATION STRUCTURE OF SILENE DIOICA (CARYOPHYLLACEAE)

Serpentine soils are rich in heavy metals and have a distinctive flora. Silene dioica is a member of the Scandinavian serpentine plant community but is also widespread outside serpentine soils. To study the population genetic consequences of serpentine stress and the origin and evolution of serpentine populations we analyzed the isozyme genetic structure of S. dioica. Seventeen populations located in the mountains of Västerbotten and Jämtland, central Sweden, were investigated by starch gel enzyme electrophoresis. About one half of the populations grow in serpentine soils and the rest on adjacent non-serpentine sites. Analyses of allele frequencies show that both serpentine and non-serpentine populations in the northern part of the studied area (Västerbotten) are genetically similar. Evidently serpentine does not exert strong selection acting upon isozyme loci. In the south (Jämtland), however, the serpentine populations exhibit genetic differentiation. This allozyme divergence is probably not due to direct selection but rather represents the effects of isolation and genetic drift. The results suggest that S. dioica has colonized serpentine repeatedly and that the tolerant populations have a multiple origin.     

Can landscape properties predict occurrence of grey-sided voles?

There has been a long-term decline in spring and fall numbers of Clethrionomys rufocanus in boreal Sweden in 1971–2005. Previous studies on permanent sampling plots in the centre of 2.5 × 2.5 km landscapes suggested that habitat fragmentation (sensu destruction) could have contributed to the decline. Therefore, we tested these findings in a field study and compared trapping results on the central sampling plots of landscapes with a low degree of fragmentation (LDF) and of “hot spot” type with trapping results in managed forest landscapes with a high degree of fragmentation (HDF). We predicted that C. rufocanus would be more common on the LDF plots. We used our permanent plots supplemented with a new sample of plots, mainly of the rare LDF type, inside or just outside the long-term study area. Very few voles were trapped on both plot types, and no difference was found. However, a subsequent pilot study with trapping in a national park with large areas of pristine, unfragmented forest yielded more voles than in the managed, more fragmented, areas. Consequently, the initial field study data and some other recent data were also re-analysed from a “local patch quality” perspective. This alternative approach revealed the positive importance of large focal patches of forest >60 years old and their content of old-growth (pine) forest (>100 years). Interestingly, at the landscape level, the frequency distribution of patches of forest >60 years old, old-growth (>100 years), and especially of old-growth pine forest (>100 years), relative to the properties of plots with C. rufocanus, suggested that there are few forest patches left that are suitable for C. rufocanus. Our current results suggest that habitat fragmentation cannot be excluded as a contributing cause to the long-term decline of C. rufocanus in boreal Sweden.     

The effects of habitat manipulation on population distribution and foraging behavior in meadow voles

Individuals, free to choose between different habitat patches, should settle among them such that fitness is equalized. Alternatives to this ideal free distribution result into fitness differences among the patches. The concordance between fitnesses and foraging costs among inhabitants of different quality patches, demonstrated in recent studies, suggests that the mode of habitat selection and the resulting fitness patterns may have important implications to the resource use of a forager and to the survival of its prey. We studied how coarse scale selection between habitat patches of different quality and quitting harvest rate in these patches are related to each other and to fine scale patch use in meadow voles (Microtus pennsylvanicus). To demonstrate these relationships, we manipulated habitat patches within large field enclosures by mowing vegetative cover and adding supplemental food according to a 2×2 factorial design. We tracked vole population densities, collected giving‐up densities (GUDs, a measure of patch quitting harvest rate), and monitored the removal of seeds from lattice grids with 1.5 m intervals (an index of fine‐scale space use) in the manipulated habitat patches. Changes in habitat quality induced changes in habitat use at different spatial scales. In preferred habitats with intact cover, voles were despotic and GUDs were low, but increased with the addition of food. In contrast, voles in less‐preferred mowed habitats settled into an ideal free distribution, GUDs were high and uninfluenced by the addition of food. Seed removal was enhanced by the presence of cover but inhibited by supplemental food. Across all treatments, vole densities and GUDs were strongly correlated making it impossible to separate their effects on seed removal rates. However, this relationship broke down in unmowed habitats, where GUDs rather than vole density primarily influenced seed removal by voles. GUDs and seed removal correlated with predation on tree seedlings formerly planted into the enclosures, demonstrating the mechanisms between coarse‐scale habitat manipulations and community level consequences on a forager's prey.     

Influence of Patch Factors and Connectivity on the Avifauna of Fragmented Polylepis Forest in the Ecuadorian Andes

Human‐induced alteration of habitat is a major threat to biodiversity worldwide, especially in areas of high biological diversity and endemism. Polylepis (Rosaceae) forest, a unique forest habitat in the high Andes of South America, presently occurs as small and isolated patches in grassland dominated landscapes. We examine how the avian community is likely influenced by patch characteristics (i.e., area, plant species composition) and connectivity in a landscape composed of patches of Polylepis forest surrounded by páramo grasslands in Cajas National Park in the Andes of southern Ecuador. We used generalized linear mixed models and an information‐theoretic approach to identify the most important variables probably influencing birds inhabiting 26 forest patches. Our results indicated that species richness was associated with area of a patch and floristic composition, particularly the presence of Gynoxys (Asteraceae). However, connectivity of patches probably influenced the abundance of forest and generalists species. Elsewhere, it has been proposed that effective management plans for birds using Polylepis should promote the conservation of mature Polylepis patches. Our results not only suggest this but also show that there are additional factors, such as the presence of Gynoxys plants, which will probably play a role in conservation of birds. More generally, these findings show that while easily measured attributes of the patch and landscape may provide some insights into what influences patch use by birds, knowledge of other factors, such as plant species composition, is essential for better understanding the distribution of birds in fragmented landscapes.     

Bot fly parasitism of the red-backed vole: host survival,infection risk,and population growth

Parasites can play an important role in the dynamics of host populations, but empirical evidence remains sparse. We investigated the role of bot fly (Cuterebra spp.) parasitism in red-backed voles (Myodes gapperi) by first assessing the impacts of the parasite on the probability of vole survival under stressful conditions as well as on the reproductive activity of females. We then identified the main factors driving both the individual risk of infection and the abundance of bot flies inside red-backed voles. Finally, we evaluated the impacts of bot fly prevalence on the growth rate of vole populations between mid-July and mid-August. Thirty-six populations of red-backed voles were sampled in the boreal forest of Québec, Canada. The presence and the abundance of parasites in voles, two host life history traits (sex and body condition), three indices of habitat complexity (tree basal area, sapling basal area, coarse woody debris volume), and vole abundance were considered in models evaluating the effects of bot flies on host populations. We found that the probability of survival of red-backed voles in live traps decreased with bot fly infection. Both the individual risk of infection and the abundance of bot flies in red-backed voles were driven mainly by vole abundance rather than by the two host life history traits or the three variables of habitat complexity. Parasitism had population consequences: bot fly prevalence was linked to a decrease in short-term growth rate of vole populations over the summer. We found that bot flies have the potential to reduce survival of red-backed voles, an effect that may apply to large portions of populations. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Spatio-temporal patterns of habitat use in voles and shrews modified by density, season and predators

1.?Although the intrinsic habitat preferences of a species can be considered to be fixed, the realized habitat use depends on the prevailing abiotic and biotic conditions. Often the core habitats are occupied by dense and stable populations, while marginal habitats become occupied only at times of high density. In a community of interacting species, habitat uses of different species become inter-related, for example an increased density of a strong competitor forcing a weaker competitor to use more marginal habitats. 2.?We studied the spatio-temporal distribution patterns of three common small mammal species, the bank vole Myodes glareolus; the field vole Microtus agrestis; and the common shrew Sorex araneus, in a 4-year trapping study carried out on six large islands, each containing a mixture of three main habitat types (forest, field and clear-cut). We experimentally released least weasels (Mustela n. nivalis) to some of the islands to see how the focal species respond to increased predation pressure. 3.?Both vole species were largely restricted to their core habitats (bank voles to forests and field voles to fields) at times of low population density. With increasing density, the relative habitat use of both species increased in the clear-cut areas. The common shrew was a generalist in its habitat use at all population densities. 4.?The release of the weasels changed the habitat use of all study species. 5.?The vole species showed a stronger aggregated pattern than the common shrew, especially at low population density. The vole aggregations remained in the same localities between seasons, except in the case of bank voles after the weasels were released. 6.?Bank voles and field voles avoided each other at high density. 7.?We conclude that intrinsically differential habitat requirements and flexibility to modify habitat use facilitate the coexistence of the two competing vole species in mosaic landscapes consisting of boreal forests and open habitats.     

Population‐level manipulations of field vole densities induce subsequent changes in plant quality but no impacts on vole demography

Grazing‐induced changes in plant quality have been suggested to drive the negative delayed density dependence exhibited by many herbivore species, but little field evidence exists to support this hypothesis. We tested a key premise of the hypothesis that reciprocal feedback between vole grazing pressure and the induction of anti‐herbivore silicon defenses in grasses drives observed population cycles in a large‐scale field experiment in northern England. We repeatedly reduced population densities of field voles (Microtus agrestis) on replicated 1‐ha grassland plots at Kielder Forest, northern England, over a period of 1 year. Subsequently, we tested for the impact of past density on vole life history traits in spring, and whether these effects were driven by induced silicon defenses in the voles’ major over‐winter food, the grass Deschampsia caespitosa. After several months of density manipulation, leaf silicon concentrations diverged and averaged 22% lower on sites where vole density had been reduced, but this difference did not persist beyond the period of the density manipulations. There were no significant effects of our density manipulations on vole body mass, spring population growth rate, or mean date for the onset of spring reproduction the following year. These findings show that grazing by field voles does induce increased silicon defenses in grasses at a landscape scale. However, at the vole densities encountered, levels of plant damage appear to be below those needed to induce changes in silicon levels large and persistent enough to affect vole performance, confirming the threshold effects we have previously observed in laboratory‐based studies. Our findings do not support the plant quality hypothesis for observed vole population cycles in northern England, at least over the range of vole densities that now prevail here.     

Male and Female Meadow Voles,Microtus pennsylvanicus,Differ in Their Responses to Heterospecific/Conspecific Over‐Marks

Voles use runways, paths, and trails that may also be used by rabbits and mink. These shared areas could contain the scent marks of conspecifics and heterospecifics. Thus, it is likely that the scent marks of heterospecifics may overlap or be overlapped by those of voles, forming over‐marks. Much is known about how voles respond to over‐marks of two different conspecifics. However, we do not know how they would respond to an opposite‐sex conspecific whose scent marks are in an over‐mark with the scent marks of predator or the scent marks of a non‐predator heterospecifics. We tested the hypothesis that meadow voles, Microtus pennsylvanicus, differ in their response to the scent mark of the opposite‐sex conspecific if the scent mark was overlapped by that of a mink, a vole predator, or rabbit, a vole non‐predator. We found that female but not male voles showed a preference for the scent marks of the opposite‐sex conspecifics that were part of the mink‐vole over‐mark when compared to those of opposite‐sex conspecifics that were not part of the over‐mark. This preference by female voles was independent of whether the male vole was the top‐scent donor or bottom‐scent donor of the over‐mark. Male and female voles showed no preference between the scent marks of the opposite‐sex conspecifics whose marks were part of or not part of the rabbit‐vole over‐mark. Sex differences in the manner that meadow voles respond to rabbit‐vole and mink‐vole over‐marks are discussed.     

Importance of large and small mammalian herbivores for the plant community structure in the forest tundra ecotone

Both theoretical arguments and empirical evidence suggests that herbivory in general and mammalian winter herbivory in particular is important in arctic–alpine ecosystems. Although knowledge of the effect of herbivores on specific plants and communities is quite extensive, little is known about the relative impact of large and small vertebrate herbivores and how it might vary among different habitats. To address this key issue, we established exclosures with two different mesh sizes in forest and nearby tundra at three different sites in four contrasting locations in the forest–tundra ecotone in northernmost Sweden and Norway. Plant community composition was recorded annually in three permanent plots within each exclosure and an unfenced control. Local densities of vertebrate herbivores were estimated in spring and autumn from 1998 to 2002. Reindeer (Rangifer tarandus) were the most abundant large vertebrate while Norwegian lemmings (Lemmus lemmus) and grey‐sided voles (Clethrionomys rufocanus) were the most common small vertebrates. The study reveals that voles and lemmings have larger effects on the vegetation than reindeer in both habitats in all four locations, even though densities of reindeer differ between locations and only two locations experienced lemming peaks during the period of the experiment. The relative abundance of five of the fifteen most common species was significantly influenced by voles and lemmings whereas only a single species was significantly influenced by reindeer. Different analyses give contrasting results on the importance of herbivory in forest versus open heathlands. A principal component analyses revealed that herbivory influenced the vegetation more in open heathlands than in forests. However, an importance index of herbivores did not differ between forest and open heathlands. Moreover, none of the plant species responded differently in the two habitats, when herbivores were removed. Our results suggest that intense and localised selective foraging by small mammals may have a more marked effect on vegetation than transient feeding by reindeer.     

Using gap‐crossing capacity to evaluate functional connectivity of two Atlantic rainforest birds and their response to fragmentation

Abstract One of the main consequences of habitat loss and fragmentation is the increase in patch isolation and the consequent decrease in landscape connectivity. In this context, species persistence depends on their responses to this new landscape configuration, particularly on their capacity to move through the interhabitat matrix. Here, we aimed first to determine gap‐crossing probabilities related to different gap widths for two forest birds (Thamnophilus caerulescens, Thamnophilidae; and Basileuterus culicivorus, Parulidae) from the Brazilian Atlantic rainforest. These values were defined with a playback technique and then used in analyses based on graph theory to determine functional connections among forest patches. Both species were capable of crossing forest gaps between patches, and these movements were related to gap width. The probability of crossing 40 m gaps was 50% for both species. This probability falls to 10% when the gaps are 60 m (for B. culicivorus) or 80 m (for T. caerulescens). Actually, birds responded to stimulation about two times more distant inside forest trials (control) than in gap‐crossing trials. Models that included gap‐crossing capacity improved the explanatory power of species abundance variation in comparison to strictly structural models based merely on patch area and distance measurements. These results highlighted that even very simple functional connectivity measurements related to gap‐crossing capacity can improve the understanding of the effect of habitat fragmentation on bird occurrence and abundance.     

Influence of Land Mosaic Composition and Structure on Patchy Populations: The Case of the Water Vole (Arvicola sapidus) in Mediterranean Farmland

The ability of patchy populations to persist in human-dominated landscapes is often assessed using focal patch approaches, in which the local occurrence or abundance of a species is related to the properties of individual patches and the surrounding landscape context. However, useful additional insights could probably be gained through broader, mosaic-level approaches, whereby whole land mosaics with contrasting patch-network and matrix characteristics are the units of investigation. In this study we addressed this issue, analysing how the southern water vole (Arvicola sapidus) responds to variables describing patch-network and matrix properties within replicated Mediterranean farmland mosaics, across a gradient of agricultural intensification. Patch-network characteristics had a dominant effect, with the total amount of habitat positively influencing both the occurrence of water voles and the proportion of area occupied in land mosaics. The proportions of patches and area occupied by the species were positively influenced by mean patch size, and negatively so by patch isolation. Matrix effects were weak, although there was a tendency for a higher proportion of occupied patches in more intensive, irrigated agricultural landscapes, particularly during the dry season. In terms of conservation, results suggest that water voles may be able to cope well with, or even be favoured by, the on-going expansion of irrigated agriculture in Mediterranean dry-lands, provided that a number of patches of wet herbaceous vegetation are maintained within the farmland mosaic. Overall, our study suggests that the mosaic-level approach may provide a useful framework to understand the responses of patchy populations to land use change.     

The Tien Shan vole (Microtus ilaeus; Rodentia: Cricetidae) as a new species in the Late Pleistocene of Europe

Grey voles (subgenus Microtus) represent a complex of at least seven closely related and partly cryptic species. The range of these species extends from the Atlantic to the Altai Mountains, but most of them occur east of the Black Sea. Using ancient DNA analyses of the Late Pleistocene specimens, we identified a new mtDNA lineage of grey voles in Europe. Phylogenetic analysis of mitochondrial DNA cytochrome b sequences from 23 voles from three caves, namely, Emine–Bair–Khosar (Crimea, Ukraine), Cave 16 (Bulgaria), and Bacho Kiro (Bulgaria), showed that 14 specimens form a previously unrecognized lineage, sister to the Tien Shan vole. The average sequence divergence of this lineage and the extant Tien Shan vole was 4.8%, which is similar to the divergence of grey vole forms, which are considered distinct species or being on the verge of speciation; M. arvalis and M. obscurus or M. mystacinus and M. rossiaemeridionalis. We estimated the time to the most recent common ancestor of the grey voles to be 0.66 Ma, which is over twice the recent estimates, while the divergence of the extant Tien Shan vole and the new lineage to be 0.29 Ma. Our discovery suggests that grey voles may have been more diversified in the past and that their ranges may have differed substantially from current ones. It also underlines the utility of ancient DNA to decipher the evolutionary history of voles.     

Statin consumption as a risk factor for developing colorectal cancer: a retrospective case study

Background

Statins are the backbone of lipid-lowering therapy and are among the most commonly prescribed drugs in the elderly population in Sweden today. Colorectal cancer is the second most common cancer in men and women, after prostate and breast cancer, respectively, with a median age of 72 years at diagnosis. Statins induce mitochondrial damage leading to accumulation of reactive oxygen species in the cell. Reactive oxygen species can cause mutations in mitochondrial as well as nuclear DNA leading to the development of cancer. Our hypothesis was that statins increase the risk for colorectal cancer.

Methods

A case study was performed on consecutive cases of colorectal cancer diagnosed at Norrlands University Hospital (NUS) in Umeå between 2012 and 2015 (n?=?325). Patients diagnosed with diabetes mellitus type II (DM II n?=?65) were excluded in the primary endpoint analysis (occurrence of colorectal cancer). As control, three databases were used to create an age-matched population in order to calculate the proportion of inhabitants using statins in the county of Västerbotten, Sweden. A secondary endpoint was cancer-specific survival among our study group of colorectal cancer patients, including those with DM II, investigating whether there was a difference if the patient was a ‘recent’ statin user or not at the time of diagnosis.

Results

Statin use at the time of colorectal cancer diagnosis in the study group was 23.8%. The corresponding figure in an age-matched population in Västerbotten was 24.6%. Using a one-proportional one-sided z test, there was no significant difference between these (23.8%, 95% CI 18.6–29.0%, p?=?0.601). When comparing groups 20–64 years of age, the difference was greater with recent statin use in 17.8% in the study population and 11.9% in Västerbotten (17.8%, 95% CI 9.0–26.6%, p?=?0.059). When considering cancer-specific survival, no significant difference in survival was seen when comparing ‘former/never’ statin users as reference category with ‘recent’ users diagnosed with colorectal cancer (HR 1.39, 95% CI 0.89–2.16).

Conclusions

No significant increase in risk for developing colorectal cancer among patients (type II diabetics excluded) medicated with statins was found. We found no correlation between ‘recent’ statin use at the time of diagnosis and cancer-specific survival.

     

Dissecting geographic variation in population synchrony using the common vole in central Europe as a test bed

Spatial synchrony of population fluctuations is ubiquitous in nature. Theoretical models suggest that correlated environmental stochasticity, dispersal, and trophic interactions are important promoters of synchrony in nature to leave characteristic signatures of distance‐dependent decays in synchrony. Recent refinements of this theory have clarified how distance‐decay curves may steepen if local dynamics are governed by different density‐dependent feedbacks and how synchrony should vary regionally if the importance and correlation of environmental stochasticity is location‐specific. We analysed spatiotemporal data for the common vole, Microtus arvalis from 49 districts in the Czech Republic to examine the pattern of population synchrony between 2000 and 2014. By extending the nonparametric covariation function, we develop a quantitative method that allows a dissection of the effects of distance and additional variables such as altitude on synchrony. To examine the pattern of local synchrony, we apply the noncentered local‐indicators of spatial association (ncLISA) which highlights areas with different degrees of synchrony than expected by the region‐wide average. Additionally, in order to understand the obtained pattern of local spatial correlations, we have regressed LISA results against the proportion of forest in each district. The common vole abundances fluctuated strongly and exhibited synchronous dynamics with the typical tendency for a decline of synchrony with increasing distance but, not with altitude. The correlation between the neighbor districts decreases as the proportion of forest increases. Forested areas are suboptimum habitats and are strongly avoided by common voles. The investigation of spatiotemporal dynamics in animal populations is a key issue in ecology. Although the majority of studies are focused on testing hypotheses about which mechanisms are involved in shaping this dynamics it is crucial to understand the sources of variation involved in order to understand the underlying processes.     

Moose density and habitat productivity affects reproduction,growth and species composition in field layer vegetation

Question: What is the effect of a gradient in moose density on reproduction, growth and functional composition of the field layer vegetation in a boreal forest, and how is this effect modified by habitat productivity? Location: Northwest of Umeå, Västerbotten, northern Sweden. Methods: Field layer vegetation was surveyed in an experimental setup with simulation of three different moose densities and a control in eight study sites along a gradient of habitat productivity. Results: We found that increased moose density led to decreased cover and reproductive effort of a browsed dwarf shrub (bilberry, Vaccinium myrtillus L.) and increased cover and reproductive effort of a non‐browsed graminoid (wavy hair‐grass, Avenella flexuosa (L.) Drejer). Increased moose density led to increased light availability and probably reduced competition from V. myrtillus. Total reproductive effort in the field layer vegetation increased, height decreased and cover of light‐demanding species and graminoids increased with increasing moose density. The effects of moose density were modified by the productivity gradient, leading to a higher relative increase in light availability and reproductive effort in highly productive areas than in low productive areas. Conclusions: Increased light availability was an important indirect effect of moose density, leading to less competition for light and a shift towards early successional species. The effect of moose density on light availability was modified by habitat productivity, leading to stronger relative effects in highly productive areas than in low productive areas.     

Local and Regional Variation in Local Frequency of Multiple Coffee Pests Across a Mosaic Landscape in Coffea arabica's Native Range

Shaded coffee has been highlighted for its potential to conserve biodiversity, and thus perhaps also a diversity of natural enemies that could control pest organisms. In southwestern Ethiopia, coffee is grown in shade both in contiguous forests and in forest patches with native trees surrounded by open fields. We hypothesized that coffee grown in contiguous forests, which is the natural habitat for coffee (Coffea arabica) and its interacting organisms, would have less pest damage due to high protection by natural enemies. We surveyed pests on coffee plants in plots within contiguous forests (10 sites) and in forest patches (21 sites). In general, the variation in number of damaged or attacked leaves by individual insect or fungal pests was larger between plants than between plots, which suggests that very local conditions or processes are important. The spatial signals were generally weak. Coffee rust and coffee blotch miner tended to have lower infestation rates in accordance with our hypothesis, while fruit flies in ripe berries were more abundant in forest patches closer to contiguous forest. Based on interviews, olive baboons showed a clear dependency on contiguous forest habitat and were regarded as a problem only in contiguous forests and forest patches close to contiguous forests. In conclusion, we found no support for a generally stronger top‐down control on coffee pests in sites within, or with connectivity to, contiguous moist afromontane forests in the native range of coffee.     

Differential effects of anthropogenic edges and gaps on the reproduction of a forest‐dwelling plant: The role of plant reproductive effort and nectar robbing by bumblebees

Forest fragmentation produces sharp changes in the spatial configuration of remnant forest patches, which include the increasing influence of patch edges on the interior of forest patches (‘edge effects’). Human activities responsible for forest fragmentation tend also to change the internal characteristics of remnant patches, for example, through the creation of gaps by selective logging. While edges and gaps can be expected to cause comparable changes in the micro‐environmental conditions of the forest, their effects on forest‐dwelling species and their interactions are not necessarily comparable. This study compares the effect of forest edges and anthropogenic gaps on the reproductive success of a self‐incompatible epiphytic plant (Mitraria coccinea), mediated by changes in its relationship with mutualists (pollinators) and antagonists (flower larcenists). Mitraria coccinea's flowers are pollinated by hummingbirds and robbed by the bumblebee Bombus dahlbomii. Edges and gaps had comparable positive effects on flower production and fruit set; however, nectar robbing was up to sevenfold higher in patches with numerous gaps and resulted in lower reproductive success (fruit set and total fruit crop). Forest fragmentation studies should therefore avoid treating forest remnants as homogeneous units (i.e. focusing exclusively on their characteristics and connectivity), without taking into account the internal heterogeneity caused by anthropogenic pressures (e.g. gaps and edge effects).