Landscape composition and habitat area affects butterfly species richness in semi-natural grasslands

During the last 50 years, the distribution and abundance of many European butterfly species associated with semi-natural grasslands have declined. This may be the result of deteriorating habitat quality, but habitat loss, resulting in decreasing area and increasing isolation of remaining habitat, is also predicted to result in reduced species richness. To investigate the effects of habitat loss on species richness, we surveyed butterflies in semi-natural grasslands of similar quality and structure, but situated in landscapes of different habitat composition. Using spatially explicit habitat data, we selected one large (6–10 ha) and one small (0.5–2 ha) grassland site (pasture) in each of 24 non-overlapping 28.2 km² landscapes belonging to three categories differing in the proportion of the area that consisted of semi-natural grasslands. After controlling for local habitat quality, species richness was higher in grassland sites situated in landscapes consisting of a high proportion of grasslands. Species richness was also higher in larger grassland sites, and this effect was more pronounced for sedentary than for mobile species. However, the number of species for a given area did not differ between large and small grasslands. There was also a significant relationship between butterfly species richness and habitat quality in the form of vegetation height and abundance of flowers. In contrast, butterfly density was not related to landscape composition or grassland size. When species respond differently to habitat area or landscape composition this leads to effects on community structure, and nestedness analysis showed that depauperate communities were subsets of richer ones. Both grassland area and landscape composition may have contributed to this pattern, implying that small habitat fragments and landscapes with low proportions of habitat are both likely to mainly contain common generalist species. Based on these results, conservation efforts should aim at preserving landscapes with high proportions of the focal habitat.     

Comparison of butterfly communities and abundances between marginal grasslands and conservation lands in the eastern Great Plains

The alteration and fragmentation of native tallgrass prairie in the Midwestern United States has created a need to identify other land types with the ability to support grassland butterfly species. This study examines butterfly usage of marginal grasslands, which consist of semi-natural grasslands existing within in a larger agricultural matrix, compared to grasslands managed for conservation of prairie species. Using generalized linear mixed models we analyzed how land purpose (marginal vs. conservation grasslands) affected butterfly abundance. We found grassland butterfly species to be significantly more common on conservation grasslands, whereas generalist species were significantly more common on marginal grasslands. Results of ordination analyses indicated that while many species used both types of habitats, butterfly species assemblages were distinct between habitat types and that edge to interior ratio and the floristic quality index of sites were important habitat characteristics driving this distinction. Within conservation grasslands we examined the relationship between butterfly abundance and the planting diversity used in restoring each site. We found higher diversity restorations hosted more individuals of butterflies considered habitat generalists, as well as species considered to be of conservation concern.     

Importance of boreal grasslands in Sweden for butterfly diversity and effects of local and landscape habitat factors

A widespread decline in biodiversity in agro-ecosystems has been reported for several groups of organisms in Western Europe. The butterfly fauna was studied in 60 selected semi-natural grasslands in a coniferous-dominated boreal landscape in south-eastern Sweden. The aim was to investigate how butterfly assemblages were affected by the amount of semi-natural grasslands in the surrounding landscape. Furthermore, we wanted to determine if semi-natural grasslands in boreal landscapes harboured species otherwise declining in other parts of Europe. For each study site, the amounts of semi-natural grasslands in the landscape within radii of 500, 2,000 and 5,000 m were studied. Nine local habitat factors were also recorded. Only the amount of semi-natural grasslands within a 5,000 m radius could explain a significant part of the variation in butterfly composition, but there was no clear relationship between the amount of semi-natural grassland and butterfly diversity. Instead, this study showed that local habitat quality was very important for butterfly diversity at individual sites. Flower abundance, sward height and herb composition were the most important local factors. Patches surrounded by a small amount of semi-natural grasslands had high butterfly diversity, contrary to expectations. This may be explained by the fact that forest habitat provides a matrix with several features suitable for butterflies. The butterfly fauna was rich in species representative of low-productivity grasslands, species that are declining in other countries in Western Europe.     

Butterfly species richness and abundance in the Katavi ecosystem of western Tanzania

We sampled butterflies in six different habitat types in and around Katavi National Park, a remote reserve consisting primarily of miombo woodland and seasonal lakes in western Tanzania. Blendon traps set for 531 trap days and 143 h of butterfly netting at 35 sites yielded 186 species from five families over a 4‐month period during the wet season. Eight of these species constituted possible range extensions. Butterfly abundance and species richness were low in cultivated habitats but high in open riverine habitats; many butterfly species were found only in seasonally flooded grassland. This study constitutes the first butterfly species inventory from this poorly‐known national park, shows that protection of dry season water sources provides an important conservation service for invertebrates as well as large mammals, and that increased cultivation outside miombo parks can reduce local butterfly diversity.     

Alien plants have greater impact than habitat fragmentation on native insect flower visitation networks

Aim

Habitat fragmentation and alien species are among the leading causes of biodiversity loss. In an attempt to reduce the impact of forestry on natural systems, networks of natural corridors and patches of natural habitat are often maintained within the afforested matrix, yet these can be subject to degradation by invasion of non‐native species. Both habitat fragmentation and alien invasive species disrupt the complex interaction networks typical of native communities. This study examines whether an invasive plant and/or the fragmented nature of the forestry landscape influences natural flower visitation networks (FVNs), flower–visitor abundance and richness or flower/visitor species composition.

Location

The species rich and diverse grasslands in the KwaZulu‐Natal Midlands, South Africa is under threat from transformation, particularly by commercial forestry plantations, restricting much of the remaining untransformed grasslands into remnant grassland patches (RGPs). Remaining patches are under additional threat from the invasive Rubus cuneifolius Pursh (bramble). Sites were established in RGPs and in a nearby protected area (PA), with and without brambles present for both areas.

Results

Flower abundance and flower area of native plant species were greater within RGP than in PA, but only in the absence of R. cuneifolius. Flower–visitor assemblages differed between invaded and uninvaded sites and also differed between PA and RGP sites. Both areas lost specialist flower–visitor species in the presence of brambles. Network modularity was greatly reduced by the presence of bramble, indicating a reduction in complexity and organization. The structure of FVNs was otherwise unaffected by presence of bramble or being located in RGPs or the PA.

Main conclusions

The RPGs contribute to regional biodiversity conservation through additional compositional diversity and intact FVNs. Rubus cuneifolius reduces ecological complexity of both RGPs and PAs, however, and its removal must be prioritized to conserve FVNs.     

Estimating the consequences of land-use changes on butterfly diversity in a marginal agricultural landscape in Sweden

Abandonment of farming with the resultant increase in forest cover is one of the major threats to semi-natural grasslands in marginal agricultural areas. In Sweden, the loss of semi-natural grassland is a serious nature conservation problem since it is one of the most species-rich habitats. In this study, the consequences of grassland abandonment and afforestation on butterfly diversity and butterfly dispersal costs are estimated and used to compare three different future land-use scenarios for a marginal agricultural landscape in Sweden. Based on previous butterfly surveys on grasslands in the area, a relationship between land-use type and butterfly diversity was established. By comparing land-use maps of different scenarios, the number of suitable habitat patches and total suitable habitat patch area with low, medium and high butterfly diversity could be estimated. To obtain an indication of possible fragmentation effects, a least-cost analysis was used to compare travel costs of the butterflies between suitable habitat patches for the different scenarios. The results show that different land-use scenarios affect butterfly diversity and travel costs differently. In the extreme case scenario of cessation of full-time farming and a reduction in part-time farming, nearly all valuable butterfly habitats will vanish, since the most species-rich habitats lie in the periphery of the settlement and are expected to be abandoned and afforested first. If, on the other hand, grassland management is less reduced the effect of abandonment on butterflies depends very much on which areas continue to be managed. To preserve the most important grasslands for butterflies an active management strategy for the whole study area would be needed. While it seems relatively easy to identify the areas most important to conserve from a butterfly diversity perspective, it will be more difficult to find an optimal spatial solution that also minimises dispersal costs for butterflies.     

松嫩平原不同生境蝴蝶群落多样性及其保护建议

随着气候变化加剧和人类活动影响,生物多样性变化及其保护逐渐受到广泛关注。蝴蝶作为开花植物的传粉媒介和生态环境监测及评价的关键指示者,其多样性变化能够在一定程度上反映生境状况,因此,有必要清晰认识不同生境中的蝴蝶多样性变化。为明确松嫩平原蝴蝶资源和不同生境的群落多样性差异,采用样线法于2016年5月-2018年8月对松嫩平原的割草草地、湿地、农田、放牧利用草地及恢复草地共五种生境类型进行调查研究。结果发现,调查共记录蝴蝶5108头,隶属于6科21属26种,其中牧女珍眼蝶（Coenonympha amaryllis）和红珠灰蝶（Plebejus argyrognomon）为优势种类,分别占蝴蝶个体总数的25.61%和31.66%,且在五种生境类型中均有分布。不同生境类型中,蝴蝶群落的物种丰富度指数和均匀度指数无明显差异,而恢复草地生境的蝴蝶群落Shannon-Wiener多样性指数较高,优势度指数较低。农田生境中的蝴蝶个体数量较少,且群落组成与其他四种生境之间均具有显著差异。五种生境类型中的蝴蝶数量和多样性均呈现一定的月动态和年动态变化趋势。除湿地和农田外,其余三种生境中蝴蝶物种和个体数量从5月到8月均持续升高。四种生境的蝴蝶物种数量、个体数量（除农田外）在2018年均出现明显下降趋势。物种丰富度指数等指标的月动态和年动态在不同生境类型间存在较大差异。这些结果表明,生境类型和人类活动与蝴蝶多样性变化关系密切,表现为单一生境中蝴蝶多样性较低,复杂生境有利于保护蝴蝶多样性。本研究有助于厘清松嫩平原蝴蝶资源的基础数据,并为该地区蝴蝶多样性保护和利用及评估该区域生态环境提供一定理论支撑。     

Vegetation change in acidic dry grasslands in Moravia (Czech Republic) over three decades: Slow decrease in habitat quality after grazing cessation

Aims

Shallow soils on acidic bedrock in dry areas of Central Europe support dry grasslands and heathlands that were formerly used as extensive pastures. These habitats are of high conservation value, but their abandonment in the 20th century triggered slow natural succession that poses a threat to specialized plant species. We asked how this vegetation and its plant diversity have changed over the past three decades and whether protected areas have positively affected habitat quality.

Location

Southwestern and central Moravia, Czech Republic.

Methods

In 2018–2019, we resurveyed 94 vegetation plots first sampled in 1986–1991 at 47 acidic dry grassland and heathland sites. We compared the number of all vascular plant species, Red List species and alien species per plot using parametric and non-parametric tests, life-form spectra using the chi-square test, species composition using detrended correspondence analysis, and indicator values using a permutation test. We also compared these changes between sites within and outside protected areas.

Results

Vegetation changes over the past three decades have been relatively small. However, we detected a decrease in total species richness, the number of Red List species and the number of characteristic species of dry grasslands. Neophytes were infrequent, while archaeophytes increased slightly. The competitive tall grass Arrhenatherum elatius, annual species and young woody plants increased in abundance or newly established at many sites. Indicator values did not change except for a slight increase in nutrient values. These negative trends occurred both within and outside protected areas but were more pronounced outside.

Conclusions

Formerly grazed acidic dry grasslands and heathlands in Moravia are slowly losing habitat specialists, including threatened plant species, and are increasingly dominated by Arrhenatherum elatius. Conservation management, especially cutting in protected areas, slows down the negative trends of decline in plant diversity and habitat quality but is insufficient to halt these processes completely.     

Butterfly community composition and conservation in and around a primary woodland of Mount Fuji, central Japan

A study was conducted in and around the Aokigahara primary woodland of Mount Fuji, central Japan, to clarify butterfly community structure along the environmental gradients of human disturbance, shade, and plant species richness, with a view to formulating conservation strategies for the community. The composition and abundance of butterfly species were recorded during 1999 along transects in three habitats: woodland, woodland edge and open land. Two sites were selected for each habitat. Canonical correspondence analysis (CCA) showed that community structure was correlated with both disturbance and shade. However, neither relationship was significant when disturbance and shade were analyzed as covariables (partial CCA), suggesting that the combined effect of the two variables played an important role in determining community structure. In contrast, CCA showed no significant relationships between butterfly community structure and plant or hostplant species richness. Correlation analyses between species characteristics and the CCA scores showed that species occurring in more disturbed habitats were more voltine, had a wider hostplant range and were associated with lower shade tolerance than those occurring in less disturbed habitats, and species occurring in darker habitats with higher shade tolerance. Generally, the structure and characteristics of the butterfly community could be understood well in terms of the habitat templet theory. To conserve endangered species on the Red List of Japan, and to maintain butterfly diversity in and around the woodland, this study suggests a need not only to conserve the primary woodland area, but most importantly to maintain the surrounding forest edge including areas of semi-natural grassland.     

Floristic diversity and the richness of locally endangered plant species of semi-natural grasslands under different management practices,southern Kyushu,Japan

Background: The rapid decline of semi-natural grasslands in Japan threatens many relic and endemic plant species. There is insufficient knowledge on how the impacts of land-use changes and management of grasslands have been affecting grassland ecosystems and what conservation measures may be taken to conserve as much of the existing plant diversity as possible.

Aim: We assessed the existing management regimes for their suitability for conserving Red Data Book (RDB) species.

Methods: We conducted our study in four districts of Kushima, Kyushu, south-west Japan, with different land-use histories. We compared species richness, plant density and abundance in six grassland types: regularly burnt, regularly mown, paddy levee, roadside, landslip and wetland communities in a total of 289 1 m x 1 m quadrats, recorded in172 grassland patches. Species richness plant density and abundance were analysed with special reference to RDB species under different land use history.

Results: Species richness of grasslands did not differ across different land use histories, yet our analysis showed that the reduced area of grasslands markedly affected the density of RDB species. Grassland types differed in their ability to support RDB species: regularly burnt grasslands were the richest in RDB species and poorest in alien species, followed by regularly mown grasslands, paddy levees, landslip, wetland and roadside communities.

Conclusions: Traditional management regimes, such as regular burning or mowing of grasslands have the best potential for conserving RDB species, and thus should be part of conservation management practices of semi-natural grasslands.     

The Influence of Landscape Grain Size on Butterfly Diversity in Grasslands

The relationship between butterfly diversity and both habitat and landscape variables was studied in two areas of southern Sweden. The habitat quality of the grasslands was similar in the two study areas but the landscape pattern differed in grain size and amount of grassland and forest. Using a transect survey method, a total of 3341 butterflies were observed and 30 taxa identified. We found that both habitat and landscape variables influenced the butterfly diversity of the investigated grasslands. Species composition differed markedly between the two study areas. A study area with a fine-grained landscape pattern, a high cover of semi-natural grassland and many forest edges had twice as many butterfly species but half the number of individuals compared with a coarser-grained study area with larger grasslands widely spread in a matrix of arable fields. The results of our study indicate that both habitat quality and landscape pattern have to be considered when developing conservation strategies for grassland butterflies.     

A comparison of the diversity and structure of butterfly communities in semi-natural and human-modified grassland habitats at the foot of Mt. Fuji, central Japan

To examine the effects of human land use and disturbance on butterfly communities we compared the diversity and structure of communities in relatively undisturbed, semi-natural grassland habitats and highly disturbed, human-modified ones. Comparisons were based on transect counts conducted at 6 study sites at the foot of Mt. Fuji in the cool temperate zone of central Japan during 1995. Out of the six community parameters used in the analyses, the species richness, species diversities H and 1/, and dominance indices were significantly different between the two habitat types stated above. That is, butterfly communities in semi-natural habitats had higher species richness and diversity, and lower dominance indices than those in human-modified ones. This suggests that heavy land modification and disturbance to semi-natural habitats change greatly its butterfly community structure, which, indeed, leads to decreasing species richness and diversity mainly due to the loss of species that are confined to semi-natural habitats. Through the comparisons of various species' characteristics, it was found that the species confined to semi-natural habitats had lower population abundance, fewer generations per year, more restricted local distributions, and narrower geographic range size in Japan than the other component species. Based on our results, it is critical that the persistence of the species that are limited to semi-natural habitats be ensured in order to maintain high species richness and diversity in grassland butterfly communities. Thus, conservation plans that retain as much semi-natural habitat as possible within the process of human grassland use, development, and modification are needed.     

Landscape effects on butterfly assemblages in an agricultural region

We examined the butterfly fauna at 62 sites in southeastern Sweden within a region exhibiting high variation in the landscape surrounding the studied grasslands. The landscape varied from an intensively-managed agricultural landscape with a large amount of open fields to a landscape with a high amount of deciduous forest/semi-natural grassland. We made 12 179 observations of 57 species of butterflies. The amount of neighbouring deciduous forest/semi-natural grassland, with >25% tree and bush cover, was the most important environmental factor explaining the variation in the butterfly assemblages. Landscape analyses at three different spatial scales showed that the variation in butterfly assemblages could be explained only at the largest scale (radius 5000 m) and not at the smaller ones (radii 500 and 2000 m).
Logistic regressions were used to predict presence/absence of butterfly species. Our study indicated that there may be critical thresholds for the amount of habitat at the landscape scale for several butterfly species as well as for species richness. For Melitaea athalia , there was a sharp increase in occupancy probability between 3 and 10% deciduous forests/semi-natural grasslands at the 5000-m scale. For 12 other species, the value for 50% probability of occurrence varied between 2 and 12% deciduous forest/semi-natural grassland. Species which had high occupancy probabilities in landscapes with a low amount of surrounding deciduous forests/semi-natural grasslands were significantly more mobile than others.
Our study highlights the importance of applying a landscape perspective in conservation management, and that single-patch management might fail in maintaining a diverse butterfly assemblage.     

Climate‐based empirical models show biased predictions of butterfly communities along environmental gradients

A better understanding of the factors that mould ecological community structure is required to accurately predict community composition and to anticipate threats to ecosystems due to global changes. We tested how well stacked climate‐based species distribution models (S‐SDMs) could predict butterfly communities in a mountain region. It has been suggested that climate is the main force driving butterfly distribution and community structure in mountain environments, and that, as a consequence, climate‐based S‐SDMs should yield unbiased predictions. In contrast to this expectation, at lower altitudes, climate‐based S‐SDMs overpredicted butterfly species richness at sites with low plant species richness and underpredicted species richness at sites with high plant species richness. According to two indices of composition accuracy, the Sorensen index and a matching coefficient considering both absences and presences, S‐SDMs were more accurate in plant‐rich grasslands. Butterflies display strong and often specialised trophic interactions with plants. At lower altitudes, where land use is more intense, considering climate alone without accounting for land use influences on grassland plant richness leads to erroneous predictions of butterfly presences and absences. In contrast, at higher altitudes, where climate is the main force filtering communities, there were fewer differences between observed and predicted butterfly richness. At high altitudes, even if stochastic processes decrease the accuracy of predictions of presence, climate‐based S‐SDMs are able to better filter out butterfly species that are unable to cope with severe climatic conditions, providing more accurate predictions of absences. Our results suggest that predictions should account for plants in disturbed habitats at lower altitudes but that stochastic processes and heterogeneity at high altitudes may limit prediction success of climate‐based S‐SDMs.     

Invertebrate conservation at the interface between the grassland matrix and natural Afromontane forest fragments

Diversity patterns of amphipods, carabid beetles and ants were investigated in five naturally-fragmented Afromontane forest remnants, and in the surrounding grassland matrix. Forests were architecturally similar. In contrast, grasslands surrounding these forests are subject to great differences in anthropogenic impacts. Consequently, transition from forest to grassland ranged from being abrupt (heavy disturbance) to gradual (little disturbance). Significantly different mean numbers of carabid individuals and species were captured between sites and multivariate analyses showed clear separation in carabid assemblage-structure with level of disturbance. Carabids were, furthermore, significantly more diverse in forests, compared to grasslands. Ants, however, were equally species rich between sites but were significantly more abundant and species rich in grasslands than forests. Amphipods, represented here by a single species, Talistroides africana, was significantly less abundant at highly disturbed sites and significantly more abundant in forests than grasslands. Results support the hypothesis that the dynamics of remnants are influenced by their surrounding landscape. Here, the dynamics of amphipods and carabids (predominantly forest taxa) were influenced by different disturbance regimes in grasslands surrounding these forests. Epigaeic ants, a predominantly grassland taxon here, also showed significant differences in assemblage-composition between sites with varying disturbance. Conserving Afromontane grasslands should be of prime concern because this will include the protection of forest/grassland ecotones and forest remnants.     

Butterfly community structure in fragmented habitats

We analysed effects of habitat fragmentation on the diversity, abundance, and life history traits of butterflies on 33 calcareous grasslands. Diversity of butterflies was positively correlated with habitat area (as was plant diversity), but not with habitat isolation. In contrast to expectations, butterfly densities of polyphagous and oligophagous species declined with habitat area whereas densities of monophagous species increased. The z -values, i.e. the slope of species–area relationships, increased with food plant specialization, from 0.07 in polyphagous, 0.11 in oligophagous, 0.16 in strongly oligophagous to 0.22 in monophagous species, and were 0.14 in plant species. Significant z -values were not only found for total species richness, based on a sample size adjusted to fragment area ( z  = 0.12), but also for the local density of butterfly species richness, based on equal sample size across all habitat fragments ( z  = 0.06). To our knowledge, this is the first study to show differential responses of monophagous, oligophagous and polyphagous species to area with respect to species richness and population density.     

Importance of local habitat conditions and past and present habitat connectivity for the species richness of grassland plants and butterflies in power line clearings

Agricultural intensification has caused drastic declines in the area and species richness of semi-natural grasslands across Europe. Novel habitats, such as power line clearings, provide alternative habitats and niches for grassland species, and might therefore mitigate these declines. However, it is not fully understood which environmental factors determine the occurrence of grassland species in the clearings. Identifying the most important drivers for grassland species occurrence would help understand the value of the clearings for grassland conservation and target enhanced management into clearings with most potential as grassland habitat. We studied the effects of local environmental conditions, and past and present connectivity to semi-natural grasslands, on the species richness of grassland plants and butterflies in 43 power line clearings in Finland. The results of generalized linear models and hierarchical partitioning showed that increasing time since clear-cut and amount of clearing residue decreased the species richness of both species groups, while the cover of mesic habitats increased it. However, the two species groups showed also divergent responses. Present-day local environmental conditions appeared to be the sole driver of grassland butterfly species richness, whereas the richness of grassland plants was related both to current conditions and historical connectivity to grasslands in 1870–1880s. This suggests the presence of an extinction debt in the studied grassland plant communities, emphasizing the need for enhanced management to increase suitable grassland habitat in the clearings. This would diminish the potential future losses of grassland plant species in the clearings and create valuable habitat for grassland butterflies as well.     

The early effects of afforestation on biodiversity of grasslands in Ireland

The target rate of afforestation in Ireland over the next 30 years is 20,000 ha per year, which would result in an increase of the forest cover from the current 10% to 17%. In order to promote sustainable forest management practices, it is essential to know the composition and conservation value of habitats where afforestation is planned and the effects of subsequent planting upon biodiversity. The objectives of this study were to investigate changes in vegetation composition and diversity of grasslands 5 years after afforestation with Sitka spruce (Picea sitchensis) and determine the primary ecological and management factors responsible for these changes. Species cover, environmental and management data were collected from 16 afforested and unplanted improved and wet grassland site pairs in Ireland. Our results indicate that 5 years after tree planting, there were significant changes in richness, composition, and abundance of species. Competitive and vigorous grasses were more abundant in planted than in unplanted sites, as were generalist species found in both open and wooded habitats, while small-stature shade-sensitive species were less abundant. Vascular plant species richness and Shannon’s diversity index were higher in unplanted wet grassland, than in the planted sites. Bryophyte species richness was higher in planted improved grassland than in unplanted sites. The differences were primarily the result of the exclusion of grazing, ground preparation, changes in nutrient management and drainage for afforestation. Drainage ditches provided a temporary habitat for less competitive species, but the overall effect of drainage was to reduce the diversity of species dependent on wet conditions. Variance partitioning showed differences in the relative influences of environmental and management variables on biodiversity in the two habitats, probably due to the greater pre-afforestation grazing pressure and fertilisation levels in improved grasslands. The differences in biodiversity between planted and unplanted grasslands indicate that afforestation represents a threat to semi-natural habitats where distinctive and highly localised plant communities could potentially occur.     

Evaluating butterflies as surrogates for birds and plants in semi-natural grassland buffers

Semi-natural grasslands can support diverse faunal and floral communities, including grassland birds, beneficial insects, and native wildflowers. Monitoring biodiversity of this type of ecosystem is important to assess abundance and richness of grassland-associated species, evaluate success of establishing grasslands, and to assess overall ecosystem health. We tested butterflies as surrogates for birds and plants to assess establishment success of semi-natural grassland buffers in north-central Mississippi using Spearman rank correlation (Spearman’s ρ). Disturbance and grassland butterfly guilds were generally not suitable surrogates for grassland bird metrics, non-grassland bird metrics, or nest density metrics. Butterflies did have consistent positive correlations with plant species richness and forb metrics, as well as consistent negative correlations with grass metrics, but these correlations were generally smaller than what is considered suitable to serve as surrogates. In general, butterflies were not suitable surrogates for birds or plants in semi-natural grassland buffers.     

Are boreal ecosystems susceptible to alien plant invasion? Evidence from protected areas

Although biological invasion by alien species is a major contributor to loss of indigenous biological diversity, few studies have examined the susceptibility of the boreal biome to invasion. Based on studies of other ecosystems, we hypothesized that alien plants will be restricted to disturbed areas near human activity and will not be found in natural areas of boreal ecosystems in Gros Morne National Park (Canada), a protected area experiencing a wide range of disturbance regimes. The distribution of alien plants in the region was evaluated using surveys, and study sites were established in naturally and anthropogenically disturbed habitats that had been invaded. Within study sites, randomization tests evaluated the importance of disturbance to alien plant invasion by examining changes in environmental conditions and species abundance within various disturbance regimes, while the importance of site characteristics limiting the distribution of alien plants were examined using Canonical Correspondence Analysis. Consistent with studies in a variety of biomes, areas of high disturbance and human activity had the greatest abundance of resources and the highest percentage of alien species. However, contrary to our hypothesis, natural areas of boreal ecosystems were found susceptible to alien plant invasion. Vegetation types vulnerable to invasion include forests, riparian areas, fens, and alpine meadows. Natural disturbance occurring in these vegetation types caused increases in bare ground and/or light availability facilitating alien plant invasion. Although high soil pH was associated with alien plants in these areas, disturbance was not found to cause changes in soil pH, suggesting susceptibility to invasion is pre-determined by bedrock geology or other factors influencing soil pH. Moose (Alces alces), a non-native herbivore, acts as the primary conduit for alien plant invasion in GMNP by dispersing propagules and creating or prolonging disturbance by trampling and browsing vegetation. The recurrent nature of disturbance within the boreal biome and its interaction with site conditions and herbivores enables alien plants to persist away from areas of high human activity. Managers of natural lands should monitor such interactions to decrease the invasion potential of alien plants.