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.     

Phylogeographic signal variation in mitochondrial DNA among geographically isolated grassland butterflies

Aim We surveyed mitochondrial DNA (mtDNA) sequence variation among regionally isolated populations of 10 grassland‐associated butterfly species to determine: (1) the utility of phylogeographic comparisons among multiple species for assessing recent evolutionary patterns, and (2) the respective roles of isolation attributable to range disjunction versus isolation attributable solely to geographic distance in establishing divergence patterns. Location The Peace River grasslands of northern Alberta and British Columbia, Canada, which are isolated by 300+ km from similar communities to the south. Methods We sequenced mtDNA (1420 bp of cytochrome c oxidase subunit I) from five grassland‐restricted butterfly species that have geographically disjunct populations and from five ecologically broader species that have more continuous distributions across the same regions. Using analysis of molecular variance (AMOVA), Mantel and partial Mantel tests, and haplotype networks, we compared population structure within and between species in order to assess the validity of single‐species phylogeographic characterizations. We then contrasted variance components between disjunct and continuously distributed species to assess whether divergences were correlated more with disjunction or with geographic distance. Results Single‐species analyses varied substantially within both the disjunct and the continuous groups. One species in each of these groups had mtDNA with unusually deep intraspecific mitochondrial lineage divergences. On the whole, however, the five species with disjunct ranges exhibited greater divergence between geographically distant populations than did the five species with continuous distributions. Comparison of variance components between disjunct and continuous species indicated that isolation attributable only to geographic distance was responsible for up to half of the total sequence variation between disjunct populations of grassland butterflies. Main conclusions Our findings show that single‐species phylogeographic analyses of post‐Pleistocene butterfly distributions are inadequate for characterizing regional biogeographic divergence histories. However, comparison of mtDNA sequence divergences between groups of disjunct and continuously distributed species can allow isolation attributable to range interruption to be quantitatively distinguished from isolation attributable solely to gene flow attenuation over the same geographic area.     

Stoichiometric homeostasis of vascular plants in the Inner Mongolia grassland

Stoichiometric homeostasis, the degree to which an organism maintains its C:N:P ratios around a given species- or stage-specific value despite variation in the relative availabilities of elements in its resource supplies, is a key parameter in ecological stoichiometry. However, its regulation and role in affecting organismal and ecosystem processes is still poorly understood in vascular plants. We performed a sand culture experiment and a field nitrogen (N) and phosphorus (P) addition experiment to evaluate the strength of N, P and N:P homeostasis in higher plants in the Inner Mongolia grassland. Our results showed that homeostatic regulation coefficients (H) of vascular plants ranged from 1.93 to 14.5. H varied according to plant species, aboveground and belowground compartments, plant developmental stage, and overall plant nutrient content and N:P ratio. H for belowground and for foliage were inversely related, while H increased with plant developmental stage. H for N (H(N)) was consistently greater than H for P (H(P)) while H for N:P (H(N:P)) was consistently greater than H(N) and H(P). Furthermore, species with greater N and P contents and lower N:P were less homeostatic, suggesting that more homeostatic plants are more conservative nutrient users. The results demonstrate that H of plants encompasses a considerable range but is stronger than that of algae and fungi and weaker than that of animals. This is the first comprehensive evaluation of factors influencing stoichiometric homeostasis in vascular plants.     

Predicting the establishment success of introduced target species in grassland restoration by functional traits

Species‐rich semi‐natural grasslands are highly endangered habitats in Central Europe and numerous restoration efforts have been made to compensate for the losses in the last decades. However, some plant species could become more easily established than others. The establishment success of 37 species was analyzed over 6 years at two study sites of a restoration project in Germany where hay transfer and sowing of threshing material in combination with additional sowing were applied. The effects of the restoration method applied, time since the restoration took place, traits related to germination, dispersal, and reproduction, and combinations of these traits on the establishment were analyzed. While the specific restoration method of how seeds were transferred played a subordinate role, the establishment success depended in particular on traits such as flower season or the lifeform. Species flowering in autumn, such as Pastinaca sativa and Serratula tinctoria, became established better than species flowering in other seasons, probably because they could complete their life cycle, resulting in increasingly stronger seed pressure with time. Geophytes, like Allium angulosum and Galium boreale, became established very poorly, but showed an increase with study duration. For various traits, we found significant trait by method and trait by year interactions, indicating that different traits promoted establishment under different conditions. Using a multi‐model approach, we tested whether traits acted in combination. For the first years and the last year, we found that models with three traits explained establishment success better than models with a single trait or two traits. While traits had only an additive effect on the establishment success in the first years, trait interactions became important thereafter. The most important trait was the season of flowering, which occurred in all best models from the third year onwards. Overall, our approach revealed the potential of functional trait analysis to predict success in restoration projects.     

Relationships among non-native plants, diversity of plants and butterflies, and adequacy of spatial sampling

Non-native invasive species are altering ecosystems in undesirable ways, often leading to biotic homogenization and rapid reduction of evolutionary potential. However, lack of money and time hampers attempts to monitor the outcome of restoration efforts. Hence, it is useful to determine whether relatively limited sampling can provide valid inferences about biological responses to pattern-based and process-based variables that are affected by restoration actions. In the Mojave Desert, invasion of salt-cedar ( Tamarix ramosissima ) has altered vegetational communities and some measures of faunal diversity. We tested whether six vegetation-based predictor variables affected species richness of butterflies in the Muddy River drainage (Nevada, USA). We also explored whether similar conclusions about relationships between vegetation and butterflies could have been obtained by using data from a subset of the 85 locations included in the study. We found that the effect of non-native plants on species richness of butterflies was negligible. Availability of nectar had the greatest independent explanatory power on species richness of butterflies, followed by species richness of plants. In comparison with the full data set, subsamples including 10, 25 and 50% of sites yielded similar conclusions. Our results suggest that relatively limited data sets may allow us to draw reliable inferences for adaptive management in the context of ecological restoration and rehabilitation.  © 2005 The Linnean Society of London, Biological Journal of the Linnean Society , 2005, 85 , 157–166.     

The acceptability of meadow plants to the slug Deroceras reticulatum and implications for grassland restoration

Background and Aims

Despite the selective pressure slugs may exert on seedling recruitment there is a lack of information in this context within grassland restoration studies. Selective grazing is influenced by interspecific differences in acceptability. As part of a larger study of how slug–seedling interactions may influence upland hay meadow restoration, an assessment of relative acceptability is made for seedlings of meadow plants to the slug, Deroceras reticulatum.

Methods

Slug feeding damage to seedling monocultures of 23 meadow species and Brassica napus was assessed in microcosms over 14 d. The severity and rate of damage incurred by each plant species was analysed with a generalized additive mixed model. Plant species were then ranked for their relative acceptability.

Key Results

Interspecific variation in relative acceptability suggested seedlings of meadow species form a hierarchy of acceptability to D. reticulatum. The four most acceptable species were Achillea millefolium and the grasses Holcus lanatus, Poa trivialis and Festuca rubra. Trifolium pratense was acceptable to D. reticulatum and was the second highest ranking forb species. The most unacceptable species were mainly forbs associated with the target grassland, and included Geranium sylvaticum, Rumex acetosa, Leontodon hispidus and the grass Anthoxanthum odoratum. A strong positive correlation was found for mean cumulative feeding damage and cumulative seedling mortality at day 14.

Conclusions

Highly unacceptable species to D. reticulatum are unlikely to be selectively grazed by slugs during the seedling recruitment phase, and were predominantly target restoration species. Seedlings of highly acceptable species may be less likely to survive slug herbivory and contribute to seedling recruitment at restoration sites. Selective slug herbivory, influenced by acceptability, may influence community-level processes if seedling recruitment and establishment of key functional species, such as T. pratense is reduced.     

The influence of seed addition and cutting regime on the success of grassland restoration on former arable land

Questions: Can seed addition enhance the success of establishing species‐rich grassland on former arable land? Are sowing date and cutting regime important in determining success? Location: Aberdeen and Elgin, northeast Scotland, United Kingdom. Methods: A field experiment was conducted at two sites to assess the effect of seed addition, sowing date and cutting regime on the vegetation developing on former arable land, the aim being to compare the success of different treatments at producing a species‐rich grassland. Results: Sowing a seed mix resulted in the establishment of vegetation very distinct from the species‐poor vegetation dominated by perennial grasses which otherwise developed, though establishment success of the sown grassland species was highly variable between sites. Where establishment of the sown species was poor, sowing date had no significant effect on species composition, whereas the cutting regime was very important. Cutting the vegetation significantly increased both the number and abundance of sown species compared with the uncut control. Conversely, where establishment had been good, the cutting regime in the first year had little effect on species composition. Cutting the vegetation at least twice a year appeared to be the most effective management over the length of the experiment. Conclusions: Sowing a seed mixture significantly reduced the abundance and number of naturally colonising species, effectively controlling problem weed species such as Senecio jacobaea and Cirsium vulgare, highlighting the agronomic value of sowing seed mixtures on fallow farmland. The sowing of a seed mix on former arable land has demonstrated that it is feasible to create vegetation similar in character to that of species‐rich grasslands.     

Rockiness determines meso-scale conservation of butterflies in Afro-montane grassland

Understanding how and why certain species respond to various habitat resources can optimize conservation strategies. Furthermore, behaviour can contribute significantly to predicting the presence or absence of a species under certain habitat conditions. There is a measurable interaction between higher percentage rock exposure in a landscape and butterfly species richness and composition in montane grasslands. Here, we attempt to explain this interaction by measuring the behavioural responses of montane butterfly species to rock cover. The butterfly assemblage was observed across three increasing levels of rockiness in the landscape. At sites within each of these rockiness categories, we also sampled the different behavioural traits of the different species. We determined whether there were significant differences in behavioural traits among this assemblage in response to rockiness. We also identified the specific species which were responsible for driving differential behavioural responses under varying rock exposure in a landscape. The rockiest areas had significantly more behavioural events, and these behaviours were more often associated with direct utilization of rocks, and related to agonistic interaction. Certain butterfly species therefore use rocks as a utility habitat resource, in different ways, highlighting the importance of the resource-based habitat concept for conservation. As such, for butterfly conservation in these montane grasslands, emphasis is placed on including a rocky gradient in protected areas and conservation landscape designs.     

Weak functional response to agricultural landscape homogenisation among plants,butterflies and birds

Measures of functional diversity are expected to predict community responses to land use and environmental change because, in contrast to taxonomic diversity, it is based on species traits rather than their identity. Here, we investigated the impact of landscape homogenisation on plants, butterflies and birds in terms of the proportion of arable field cover in southern Finland at local (0.25 km²) and regional (> 10 000 km²) scales using four functional diversity indices: functional richness, functional evenness, functional divergence and functional dispersion. No uniform response in functional diversity across taxa or scales was found. However, in all cases where we found a relationship between increasing arable field cover and any index of functional diversity, this relationship was negative. Butterfly functional richness decreased with increasing arable field cover, as did butterfly and bird functional evenness. For butterfly functional evenness, this was only evident in the most homogeneous regions. Butterfly and bird functional dispersion decreased in homogeneous regions regardless of the proportion of arable field cover locally. No effect of landscape heterogeneity on plant functional diversity was found at any spatial scale, but plant species richness decreased locally with increasing arable field cover. Overall, species richness responded more consistently to landscape homogenisation than did the functional diversity indices, with both positive and negative effects across species groups. Functional diversity indices are in theory valuable instruments for assessing effects of land use scenarios on ecosystem functioning. However, the applicability of empirical data requires deeper understanding of which traits reliably capture species’ vulnerability to environmental factors and of the ecological interpretation of the functional diversity indices. Our study provides novel insights into how the functional diversity of communities changes in response to agriculturally derived landscape homogenisation; however, the low explanatory power of the functional diversity indices hampers the ability to reliably anticipate impacts on ecosystem functioning.     

Factors affecting the distribution of vascular plants, springtails, butterflies and birds on small tropical islands

Aim

The primary objective of our study was to examine the factors affecting the distribution of vascular plants, springtails, butterflies and birds on small tropical islands to understand how different groups of organisms with distinct biological traits respond to biogeographical variables, such as island area.

Location

The Republic of Singapore (103°50′E, 1°20′N) located at the southern tip of Peninsular Malaysia.

Methods

Seventeen islands were surveyed for vascular plants, springtails, butterflies and birds. Correlation analysis, simple linear and multiple regression analyses and the nestedness index were used to test the hypotheses that (1) area is the best predictor of species/genus richness at both the community and specific/generic levels; (2) there is no correlation between population density and island area; and (3) species/genera are distributed as nested subsets.

Results

Area was the most significant factor in determining the island distribution of springtails, butterflies and birds at both the community and specific/generic levels, although there were disparate responses to the biogeographical variables between the three taxonomic groups, as well as between common species within each group. Individual species displayed disparate responses to biogeographical variables, suggesting that patterns of distribution at the community level may not be a good indicator of the population dynamics of individual species/genera. Plant species richness did not show any correlation with any of the tested variables. Population densities of springtails, butterflies and birds were positively correlated with area, contradicting the assumption of the equilibrium theory of island biogeography that population density of island species is independent of area. Population densities of plants showed no correlation with any of the tested biogeographical variables. Vascular plant, springtail, butterfly and bird communities on the islands showed significant patterns of nestedness, indicating there may be species/genus‐specific responses to biogeographical variables.

Main conclusions

We conclude that although area was the most important factor affecting the island distribution of springtails, butterflies and birds, conservation planning must take into consideration how target taxonomic groups respond to biogeographical variables, instead of relying on general principles (e.g. those derived from the equilibrium theory). On a local scale, in order to preserve the island biodiversity of Singapore, the highest priority should be given to preserving the larger islands (e.g. Pulau Ubin) which not only have higher numbers of species, but also species that are absent on smaller islands.

     

Effects of managing semi-natural grassland buffers on butterflies

Butterflies are important components of biodiversity in grassland ecosystems and provide ecosystem services such as pollination. Although agricultural intensification has led to a scarcity of native grassland habitats within most agricultural landscapes of North America, fragmented remnants and semi-natural habitats may support diverse communities, including butterflies, as long as vital resources such as host plants are available. The United States Department of Agriculture’s (USDA) Conservation Reserve Program practice CP33 Habitat Buffers for Upland Birds (USDA 2004) provides semi-natural grassland habitat in agricultural landscapes, but a knowledge gap exists about impacts of prescribed disturbance (e.g. burning or disking) on butterflies. We monitored butterfly habitat and butterfly communities on experimentally manipulated CP33 grassland buffers in Clay County, Mississippi from 2007 to 2009. Disturbance guild butterfly species richness did not differ among treatments. However, disturbance guild abundance was positively affected by disking in both the first and second growing seasons following disking, and the magnitude of this response varied between years. Effects of burning on disturbance guild abundance did not differ from the control treatment. There were no treatment differences for grassland guild butterfly abundance and species richness suggesting that periodic disturbance does not unduly impact grassland-associated butterflies in the southeastern US. Our results support current USDA practice standards that require periodic disturbance during the 10-year contract, but restrict the disturbance to 1/3 or 1/4 of grassland buffer area in a given year.     

Regional differences in soil pH niche among dry grassland plants in Eurasia

Soil pH is a key predictor of plant species occurrence owing to its effect on the availability of nutrients and phytotoxic metals. Although regional differences in realized soil pH niche (‘niche shifts’) have been reported since the 19th century, no study has disentangled how they are influenced by spatial differences in substrate availability, macroclimate, and competitors. We linked plot‐level data on species occurrence and measured soil pH from dry grasslands in eight regions across Eurasia (n = 999 plots), spanning a geographic gradient of 6862 km. We calculated regional shifts in niche optimum (D_opt) and width (D_width) for 73 Species × Region 1 × Region 2 combinations (SRRs; 38 study species) using extended Huisman–Olff–Fresco models. Next, we used commonality analysis to partition the contribution of substrate availability, precipitation, and species traits indicative of competitive ability to variation in regional niche shifts. Shifts in optimum were rare (5% of SRRs with D_opt ≥ 1 pH units) but many species did not show optima within regions. By contrast, shifts in niche width were common (22% of SRRs with D_width ≥1 pH units) and there were pronounced interspecific differences. Whereas none of the three predictors significantly explained shifts in niche optimum, common and unique effects of substrate availability and precipitation accounted for 85% of variation in niche width. Our results suggest that substrate availability and precipitation could be the driving factors behind species regional shifts in niche width. Studies that address additional factors, such as other edaphic niches, and their variability at the regional and micro‐scale will improve our understanding of the mechanisms underlying species distributions.     

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.     

云雾山不同恢复方式下草地植物与土壤的化学计量学特征

研究云雾山天然草地、灌草地、禁牧地、撂荒地4种恢复方式下草地各植物组分(植物地上部分、枯落物、根系)与土壤C、N、P化学计量特征及其相互关系.结果表明: 土壤与植物地上部分和根系的化学计量学特征显著相关,并且植物地上部分与根系之间P的联系比N紧密,土壤与植物地上部分和根系之间N的联系比P紧密,而土壤与枯落物、根系与枯落物的化学计量学特征相关性不显著.不同恢复方式间植物地上部分和根系总体的C、N储量无显著差异,P储量差异显著且以撂荒地最大(0.49 g·m^-2),禁牧地最小(0.29 g·m^-2).禁牧年限对植物和土壤的化学计量学特征影响较小;耕地撂荒恢复12年后土壤C、N(分别为9.98和1.07 g·kg^-1)仍显著低于天然草地(分别为14.27和1.55 g·kg^-1),两者植物化学计量特征的差异由撂荒地各植物组分P浓度高引起;由于根系生物量的稀释作用,天然草地根系N、P浓度最低(分别为6.25和0.57 g·kg^-1);灌草地地上部分N、P浓度偏低(分别为12.77和 0.98 g·kg^-1),但根系N、P浓度偏高(分别为9.30和0.77 g·kg^-1).物种组成是影响植物生态化学计量学特征变化的主要因素,不同恢复方式间群落相似度高则整体化学计量特征差异小.