Contrasting success in the restoration of plant and phytophagous beetle assemblages of species-rich mesotrophic grasslands

Over the last 60 years changes to the management of species-rich mesotrophic grasslands have resulted in the large-scale loss and degradation of this habitat across Europe. Restoration of such grasslands on agriculturally improved pastures provides a potentially valuable approach to the conservation of these threatened areas. Over a four-year period a replicated block design was used to test the effects of seed addition (green hay spreading and brush harvest collection) and soil disturbance on the restoration of phytophagous beetle and plant communities. Patterns of increasing restoration success, particularly where hay spreading and soil disturbance were used in combination, were identified for the phytophagous beetles. In the case of the plants, however, initial differences in restoration success in response to these same treatments were not followed by subsequent temporal changes in plant community similarity to target mesotrophic grassland. It is possible that the long-term consequences of the management treatments would not be the establishment of beetle and plant communities characteristic of the targets for restoration. Restoration management to enhance plant establishment using hay spreading and soil disturbance techniques would, however, still increase community similarity in both taxa to that of species-rich mesotrophic grasslands, and so raise their conservation value. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Evaluation of Initial Restoration Measures during the Restoration of Calcareous Grasslands on Former Arable Fields

In 1993, experiments on the restoration of calcareous grasslands on ex‐arable fields were started in order to provide new habitats for species of a small nature reserve with ancient grasslands north of Munich (Germany). The effects of diaspore transfer by the application of seed‐containing hay on vegetation establishment were studied on restoration fields with and without topsoil removal for 5 years. The aim of the study was to assess plant diversity for the evaluation of restoration success by different methods including determination of species with viable seeds in the hay by germination tests, phenological investigations on hay‐transfer source sites at the time of harvest, and vegetation analyses on the restoration sites. Total seed content of the hay and the number and composition of plant species with viable seeds were affected by the time of harvesting and differed between a site which had been used as arable field until 1959 and ancient grassland sites. Nevertheless, the number of established hay‐transfer species showed only few differences between restoration fields. The proportion of species transferred to restoration fields in relation to the number of species with viable seeds in the hay was between 69 and 89%. Five years after the hay transfer, the proportion of the established species was still between 58 and 76%. Up to now, topsoil removal had no significant effect on the number of established hay‐transfer species. After triple hay application the absolute number of transferred grassland species was higher than on sites with single hay application, but restoration efficiency was lower because many of the species with viable seeds in the hay did not establish. In general, our results showed that the transfer of autochthonous hay is a successful method to overcome dispersal limitation in restoration projects.     

The relative importance of trees versus lianas as hosts for phytophagous beetles (Coleoptera) in tropical forests

Aim Insect assemblages associated with lianas in tropical forests are poorly studied compared with those associated with trees. The importance of lianas for the maintenance of local species richness of insect herbivores in tropical forests is therefore poorly understood. With this in mind, a comparative study of the relative importance of trees and lianas as hosts for phytophagous beetles was carried out. Location The study area was located in the canopy of a dry tropical forest in Parque Natural Metropolitano, Panama province, Republic of Panama. Methods A crane system was utilized to access the canopy. The number of species and host specialization of adult phytophagous beetles associated with twenty‐six liana species of ten different families, and twenty‐four tree species of twelve different families were compared. Results A total of 2561 host associations of 697 species of beetles were determined (1339 for trees and 1222 for lianas). On average 55.8 ± 6.8 beetle species were found to be associated with each tree species while the comparable number for lianas was 47.0 ± 6.1. The pooled numbers of phytophagous beetle species associated with trees and lianas, respectively, were not significantly different. However, there were significantly more species feeding on green plant parts on lianas than on trees, and there were significantly more wood eaters on trees than on lianas. Phytophagous beetles associated with lianas were significantly more specialized than the tree associates due to a higher degree of specialization among the species feeding on green plant parts of lianas. Wood eaters and flower visitors showed no differences in host specialization on different growth forms. Main conclusion The present study shows that lianas are at least as important as trees for the maintenance of local species diversity of phytophagous beetles at this site. The mechanisms that drive the patterns can only be hypothesized. Plant architecture, size, and length of growing season are probably involved. Further studies, should include measurements of plant traits to elucidate experimentally what mechanisms that drive the patterns. Additional insight would come from similar studies in other forest types, and also studies of other major taxonomic groups of arthropod herbivores.     

Experimental assemblage of novel plant–herbivore interactions: ecological host shifts after 40 million years of isolation

Geographic isolation is the first step in insect herbivore diet specialization. Such specialization is postulated to increase insect fitness, but may simultaneously reduce insect ability to colonize novel hosts. During the Paleocene‐Eocene, plants from the order Zingiberales became isolated either in the Paleotropics or in the Neotropics. During the Cretaceous, rolled‐leaf beetles diversified in the Neotropics concurrently with Neotropical Zingiberales. Using a community of Costa Rican rolled‐leaf beetles and their Zingiberales host plants as study system, we explored if previous geographic isolation precludes insects to expand their diets to exotic hosts. We recorded interactions between rolled‐leaf beetles and native Zingiberales by combining DNA barcodes and field records for 7450 beetles feeding on 3202 host plants. To determine phylogenetic patterns of diet expansions, we established 20 experimental plots in the field, in which we planted plots five exotic Zingiberales, recording beetles feeding on these exotic hosts. In the laboratory, using both native and exotic host plants, we reared a subset of insect species that had expanded their diets to the exotic plants. The original plant–herbivore community comprised 24 beetle species feeding on 35 native hosts, representing 103 plant–herbivore interactions. After exotic host plant introduction, 20 percent of the beetle species expanded their diets to exotic Zingiberales. Insects only established on exotic hosts that belong to the same plant family as their native hosts. Laboratory experiments show that beetles are able to complete development on these novel hosts. In conclusion, rolled‐leaf beetles are preadapted to expand their diets to novel host plants even after millions of years of geographic isolation.     

Problems, Approaches, and Results in Restoration of Dutch Calcareous Grassland During the Last 30 Years

This paper is based on research of the restoration of species‐rich calcareous grasslands in The Netherlands, over the last 30 years. Chalk grassland is a semi‐natural vegetation with a high density of species at a small scale. This type of vegetation was once widespread in Western Europe as common grazing land, mainly for flocks of sheep for which the main function was dung production. In some regions of Central Europe, these grasslands were also used for hay production. The dung was used to maintain arable field production at a reasonable level. In the chalk district in the southernmost part of The Netherlands some 25 sites of this vegetation, varying in area from 0.05–4.5 ha, are still present. Chalk grassland completely lost its significance for modern agricultural production after the wide application of artificial fertilizer following World War II. This grassland has a high conservation value both for plants and animal species, of which a large number of species are exclusively restricted to this biotope. When conservation activities started at a large scale in the early 1960s, three different types of restoration activities could be distinguished: (1) restoration of fertilized sites; (2) restoration of abandoned grasslands; and (3) recreation of chalk grassland on former arable fields. The main aim of the restoration attempt is to create and/or improve sustainable conditions for both plant and animal species characteristic of the chalk grassland ecosystem. In the process of restoration, several phases of different activities can be distinguished: (1) pre‐restoration phase, during which information of the land use history is collected and, based on these data, clear restoration goals are established; (2) initial restoration phase, during which effects of former, non‐conservational land use has to be undone in order to stimulate germination and establishment of target species originating from soil seed bank and species pool; (3) consolidation phase, including the introduction and continuation of a regular management system for sustainable conservation; and (4) long‐term conservation strategy, including measures to prevent disturbance from the outside and genetic erosion and extinction of locally endangered plant populations.     

Beetles (Coleoptera) on brownfield sites in England: An important conservation resource?

A total of 78 brownfield (post-industrial and urban) sites were surveyed for beetles between 1991 and 2001 throughout England using pitfall traps. The distribution of ground, rove and phytophagous beetle assemblages was investigated using ordination and classification analyses. Site drainage and vegetation cover had a profound effect on the distribution of ground and rove beetle assemblages but site location was also important for phytophagous beetle assemblages. A total of 182 records of 46 nationally rare and scarce species (16 ground, 10 rove and 20 phytophagous species) were generated. A number of these species are more usually associated with other, more natural habitats such as riverine sediments, sandy heaths and chalk grassland. Brownfield sites provide habitat conditions similar to more natural habitats and they may help maintain populations of some rare and scarce species. The results indicate that brownfield sites are important habitats for beetles and there is evidence that the situation is similar for other invertebrate groups. There should be no further assumptions that post-industrial and urban sites have no conservation interest.     

Timing of onset of evening activity of adult Chinese rose beetles (Coleoptera: Scarabaeidae)

Adult Chinese rose beetles, Adoretus sinicus (Burmeister) (Coleoptera: Scarabaeidae: Adoretini), present in China, Taiwan, Indonesia, Cambodia, Laos, Singapore, Thailand, Vietnam, the Marianas Islands, the Caroline Islands, and the Hawaiian Islands, are nighttime defoliators that feed on a wide variety of plant species. It has recently been demonstrated that illumination of plants at dusk has the potential to discourage feeding by adult Chinese rose beetles on the illuminated plants. To effectively use lighting to minimize defoliation of host plants, it is critical to know the timing of the initial host plant colonization by the beetles to ensure that illumination is initiated before host plant colonization begins. Adult Chinese rose beetles were observed to colonize host plants at dusk, with initiation of beetle colonization averaging more than 21 min after sunset, with the earliest observed beetle colonization occurring 11 min after sunset. These times corresponded to an average light level of 7.0 lux at the first colonization and the earliest first colonization occurring at 26.9 lux. Based on these results, use of lighting to minimize defoliation of host plants should be initiated at about sunset in order to discourage colonization (and associated defoliation) by adult Chinese rose beetles.     

The Natural Host Range of Beetle Species Feeding on Broom, Cytisus scoparius (L.) Link (Fabaceae), in Southwest Europe

The natural host range of beetles feeding on broom ( Cytisus scoparius ) and 14 other species (including six other Cytisus species) in the tribe Genisteae was investigated at 39 sites in Spain , Portugal and France in 1989 and 1992 as part of a biological control programme for broom . Data on host - plant associations were analyzed for 36 phytophagous beetle species from 18 sites , and host records were listed for an additional 58 species . Nine species were apparently restricted to the genus Cytisus : Cryptocephalus octoguttatus, Gonioctena olivacea, Bruchidius lividimanus, B. villosus, Exapion elongatissimum, E. fuscirostre, Lepidapion sp . 1 , Polydrusus confluens and Tychius parallelus. These field records suggest a narrower host - plant range for some beetle species than laboratory host - range tests , and may assist in interpreting host - plant associations reported in the literature . Beetle species with a restricted host - plant range were rarely found on related non - host plants .     

The importance of plant relatedness for host utilization among phytophagous insects

Current methods for measuring similarity among phytophagous insect communities fail to consider the phylogenetic relationship between host plants. We analysed this relation based on 3580 host observations of 1174 beetle species associated with 100 species of angiosperms in two different forest types in Panama. We quantified the significance of genetic distance as well as taxonomic rank among angiosperms in relation to species overlap in beetle assemblages. A logarithmic model describing the decrease in beetle species similarity between host-plant species of increasing phylogenetic distance explains 35% of the variation. Applied to taxonomic rank categories the results imply that except for the ancient branching of monocots from dicots, only adaptive radiations of plants on the family and genus level are important for host utilization among phytophagous beetles. These findings enable improvements in estimating host specificity and species richness through correction for phylogenetic relatedness between hosts and consideration of the host-specific fauna associated with monocots.     

Habitat and climatic preferences drive invasions of non-native ambrosia beetles in deciduous temperate forests

The introduction of non-native ambrosia beetles can cause severe damage in forest ecosystems. Understanding the environmental drivers affecting their invasion at the local scale is of utmost importance to enhancing management strategies. Our objectives were: (1) to determine the influence of forest composition, forest structure, and climate on invasion success of non-native ambrosia beetles in deciduous temperate forests, and (2) to test the effect of host tree species on colonization success by non-native ambrosia beetles. In 2013, we sampled 25 forest stands located in North-East Italy belonging to three forest types dominated respectively by hop hornbeam, chestnut, and beech. Both ethanol-baited traps and trap-logs of five tree species (hop hornbeam, chestnut, beech, manna ash, and black locust) were used to sample non-native and native ambrosia beetle communities. We found a clear effect of forest composition on non-native species richness and activity-density, as measured in ethanol-baited traps, both of which were higher in chestnut-dominated forests. Furthermore, we found a positive effect of temperature on both the number of trapped non-native species and their activity-density, with cold temperatures limiting beetle spread in high-elevation forests. Only Xylosandrus germanus successfully colonized the trap-logs. The number of colonized logs was higher for chestnut and in chestnut-dominated forests. Both trapping and log-baiting indicated that chestnut-dominated forests were at greater risk of invasion than hop hornbeam- and beech-dominated forests. Given the economic and ecological importance of chestnut, ambrosia beetle communities present in chestnut-dominated forests should be monitored to determine where protective measures must be taken.     

Gut microbiota in the burying beetle,Nicrophorus vespilloides,provide colonization resistance against larval bacterial pathogens

Carrion beetles, Nicrophorus vespilloides, are reared on decomposing carrion where larvae are exposed to high populations of carcass‐derived bacteria. Larvae do not become colonized with these bacteria but instead are colonized with the gut microbiome of their parents, suggesting that bacteria in the beetle microbiome outcompete the carcass‐derived species for larval colonization. Here, we test this hypothesis and quantify the fitness consequences of colonization with different bacterial symbionts. First, we show that beetles colonized by their endogenous microbiome produce heavier broods than those colonized with carcass‐bacteria. Next, we show that bacteria from the endogenous microbiome, including Providencia rettgeri and Morganella morganii, are better colonizers of the beetle gut and can outcompete nonendogenous species, including Serratia marcescens and Escherichia coli, during in vivo competition. Finally, we find that Providencia and Morganella provide beetles with colonization resistance against Serratia and thereby reduce Serratia‐induced larval mortality. This effect is eliminated in larvae first colonized by Serratia, suggesting that while competition within the larval gut is determined by priority effects, these effects are less important for Serratia‐induced mortality. Our work suggests that an unappreciated benefit of parental care in N. vespilloides is the social transmission of the microbiome from parents to offspring.     

危害松树的小蠹虫与其伴生菌的相互关系

危害健康松属植物的小蠹虫经常与一些特殊的真菌相联系。在小蠹虫危害松属植物的过程中,这些真菌被小蠹虫的一些特殊结构或者体表携带到松属植物上。小蠹虫与其伴生菌的联系表明小蠹虫和其伴生菌之间是一种互惠互利的关系。伴生菌随小蠹虫扩散而被带到新的寄主树木。而伴生菌或作为小蠹虫的食物来源,但更重要的是,有些伴生菌能够通过其菌丝渗透寄主组织,释放毒素,致死寄主树木,以帮助小蠹虫降低寄主抗性。许多研究致力于探索小蠹虫/伴生菌联合体与寄主树木之间关系的特征和确定小蠹虫与其伴生菌相互关系在生态学上的意义。然而,不同小蠹虫和其伴生菌所组成的共生体系,不同小蠹虫的种群数量,和不同环境条件下同种小蠹虫与其伴生菌相互作用方式的差异使我们在研究小蠹虫和其伴生菌这个共生体系时,对它们各自在成功聚集寄主树木过程中所发挥的重要作用的概括变得非常困难。     

Near‐natural methods promote restoration of species‐rich grassland vegetation—revisiting a road verge trial after 9 years

The present loss of species‐rich grasslands makes it vital to restore these valuable habitat types, including novel habitat variants such as road verges. Due to the lack of knowledge on long‐term outcomes of restoration initiatives, well‐designed studies comparing different restoration methods are needed. In this study, we examined fine‐scale vegetation recovery patterns over 9 years in a field experiment with several near‐natural restoration methods (adding local seed mixtures, transferring hay from local grasslands using hard or light raking, and natural regeneration) in a road verge. We compared this to standard revegetation (hydroseeding species‐poor commercial seed mixtures). We found major temporal changes in vegetation restored by local seed or hay transfer, before it gradually became more similar to the donor grasslands and seed mixtures, which served as references for the experiment. Natural (spontaneous) regeneration with seed dispersal from surroundings gave similar results, whereas areas revegetated using standard methods became more dissimilar to the reference sites during the study period. The main variation in species composition reflected the contrast between local donor grasslands and seed mixtures and the species‐poor early successional grasslands. We conclude that near‐natural methods (hay transfer and seeding) successfully restored species‐rich grassland, including road verges. This study underlines the importance of comparing several treatments over a sufficiently long period to assess their success in restoring species‐rich grassland.     

The effectiveness of US mitigation and monitoring practices for the threatened Valley elderberry longhorn beetle

Habitat mitigation frequently leads to planting of new habitat, assuming that it can replace lost natural habitat. Yet this practice has rarely been examined in detail. In the USA habitat mitigation is frequently allowed under the US Endangered Species Act, providing monitoring reports which represent a potentially valuable data source for imperiled species. We used publicly available reports for the US threatened Valley elderberry longhorn beetle (Desmocerus californicus dimorphus) to assess record keeping practices used by US Fish and Wildlife Service (FWS), and the utility of such analyses for improving conservation. A large portion of mitigation reports known to exist were missing from FWS files, indicating problems with data management, and a loss of important information. Transplanted brought mature beetle host plants and beetles to sites, promoting beetle colonization. Conversely, few sites with seedlings were colonized. Results indicate a need for improved data management by FWS and longer term monitoring.     

Experimental demography and the vital rates of generalist and specialist insect herbivores on native and novel host plants

1. Colonization success of species when confronted with novel environments is of interest in ecological, evolutionary and conservation contexts. Such events may represent the first step for ecological diversification. They also play an important role in adaptive divergence and speciation. 2. A species that is able to do well across a range of environments has a higher plasticity than one whose success is restricted to a single or few environments. The breadth of environments in which a species can succeed is ultimately determined by the full pattern of its vital rates in each environment. 3. Examples of organisms colonizing novel environments are insect herbivores expanding their diets to novel host plants. One expectation for insect herbivores is that species with specialized diets may display less plasticity when faced with novel hosts than generalist species. 4. We examine this hypothesis for two generalist and two specialist neotropical beetles (genus Cephaloleia: Chrysomelidae) currently expanding their diets from native to novel plants of the order Zingiberales. Using an experimental approach, we estimated changes in vital rates, life-history traits and lifetime fitness for each beetle species when feeding on native or novel host plants. 5. We did not find evidence supporting more plasticity for generalists than for specialists. Instead, we found similar patterns of survival and fecundity for all herbivores. Larvae survived worse on novel hosts; adults survived at least as well or better, but reproduced less on the novel host than on natives. 6. Some of the novel host plants represent challenging environments where population growth was negative. However, in four novel plant-herbivore interactions, instantaneous population growth rates were positive. 7. Positive instantaneous population growth rates during initial colonization of novel host plants suggest that both generalist and specialist Cephaloleia beetles may be pre-adapted to feed on some novel hosts. This plasticity in host use is a key factor for successful colonization of novel hosts. Future success or failure in the colonization of these novel hosts will depend on the demographic rates described in this research, natural selection and the evolutionary responses of life-history traits in novel environments.     

Colonization of host patches following long-distance dispersal by a goldenrod beetle, Trirhabda virgata

1. The arrival of the chrysomelid beetle Trirhabda virgata on isolated patches of its host Solidago altissima was closely monitored to determine how conspecific density and host condition influence colonization.
2. Experimental host patches, which were set on the roof of a four-storey building located 0.7 km from the nearest naturally occurring hosts, were frequently colonized by beetles over a 2-week dispersal period.
3. Females preferred lush host patches that were free from simulated Trirhabda chewing damage. Females colonized lush patches more often than defoliated patches at two spatial scales, when patches were 2 m and 25 m apart. Males did not show a strong preference for lush plants.
4. Males aggregated on plants that already contained adult conspecifics, apparently increasing their reproductive success. Females did not respond to the presence of adults on the patch.
5. Ninety-five per cent of the females arriving on the isolated plants had mated before flying, indicating that lone females are able to colonize empty stands.
6. By avoiding heavily defoliated plants, females should dissipate local outbreaks and spread their offspring away from over-exploited areas.     

Potato field colonization by low-density populations of Colorado potato beetle as a function of crop rotation distance

Monitoring of 10 and 12 commercial potato, Solanum tuberosum L., fields in 2004 and 2005, respectively, confirmed for a low-density population of Colorado potato beetle, Leptinotarsa decemlineata (Say), that potato fields nearest to the previous year's potato fields are significantly more colonized by this beetle than more distant fields. This pattern is partially explained by the presence of a reservoir of colonizers estimated at 35% of the season-long colonizing population in 2004 and 2005. These beetles, which emerged before potato plants broke the ground, were ready to establish themselves on nearby potato plants. The colonizing Colorado potato beetles dispersed within the maximum range of 1.5 km over a season, and the colonization risk for the new crop decreased with distance from the previous year's crop. There was no evidence that rotation distance delayed colonization. In terms of pest management, although the findings confirm that only long 1.5-km rotations can prevent Colorado potato beetle colonization, they also demonstrate that short rotations of 100 m or more can make substantial contributions to pest management programs for low-density beetle populations.     

The impact of site conditions and seed dispersal on restoration success in alluvial meadows

Abstract. We studied the restoration success of flood plain meadows in the northern Upper Rhine valley, where between 1988 and 1992, 35 ha of arable land was converted into grassland and subsequently managed for nature conservation. Remnant populations of typical alluvial meadow species were found in old meadows and along drainage ditches that dissect the whole area. We analysed the site conditions and phytosociological relevés in old and new meadows. Small differences in site parameters between old and new meadows contrasted with a clear floristic differentiation between the two meadow types. The vegetation of old meadows was much more differentiated along prevailing environmental gradients than the vegetation of new meadows. Despite the favourable site conditions for the re‐establishment of species‐rich meadows on the former arable land, restoration success was limited to the vicinity of remnant stands. In contrast to old meadows, indicator species of new grassland were still typical species of regularly disturbed ruderal and arable habitats, often capable of building up a persistent seed bank. The precise mapping of 23 target species revealed that even wind dispersal predominantly leads to re‐establishment in the close circumference of parent plants. We found no indication that regular flooding, hay‐making and autumnal grazing had an impact on recolonization of newly created grassland. Even under favourable conditions for the re‐establishment of target species, restoration success in alluvial meadows proved to be strongly dispersal limited. We discuss the implications of our findings for future restoration management in grasslands.     

Patch colonization by Trirhabda canadensis (Coleoptera: Chrysomelidae): effects of plant species composition and wind

Summary The goldenrod leaf beetle, Trirhabda canadensis, is known to respond to odors of host and non-host species in the laboratory. Here we report movements of T. canadensis in the field in response to volatile odors from monocultures and polycultures of host plants. Overall, beetles preferentially colonized plots with a higher density of host plants and lower diversity of allelochemicals, but under some wind conditions there were marked exceptions. At high windspeeds, they colonized whichever plot(s) was upwind. At low windspeeds, beetles colonized preferred plots even when they were not upwind. The data suggest that odor dispersion varies in a complex way with windspeed: at low windspeeds beetles received information from a wide are of vegetation and made choices while at high windspeeds information was available only from upwind plot(s).     

Soil Organism and Plant Introductions in Restoration of Species-Rich Grassland Communities

Soil organisms can strongly affect competitive interactions and successional replacements of grassland plant species. However, introduction of whole soil communities as management strategy in grassland restoration has received little experimental testing. In a 5-year field experiment at a topsoil-removed ex-arable site ( receptor site ), we tested effects of (1) spreading hay and soil, independently or combined, and (2) transplanting intact turfs on plant and soil nematode community development. Material for the treatments was obtained from later successional, species-rich grassland ( donor site ). Spreading hay affected plant community composition, whereas spreading soil did not have additional effects. Plant species composition of transplanted turfs became less similar to that in the donor site. Moreover, most plants did not expand into the receiving plots. Soil spreading and turf transplantation did not affect soil nematode community composition. Unfavorable soil conditions (e.g., low organic matter content and seasonal fluctuations in water level) at the receptor site may have limited plant and nematode survival in the turfs and may have precluded successful establishment outside the turfs. We conclude that introduction of later successional soil organisms into a topsoil-removed soil did not facilitate the establishment of later successional plants, probably because of the "mismatch" in abiotic soil conditions between the donor and the receptor site. Further research should focus on the required conditions for establishment of soil organisms at restoration sites in order to make use of their contribution to grassland restoration. We propose that introduction of organisms from "intermediate" stages will be more effective as management strategy than introduction of organisms from "target" stages.