No loss of genetic divergence in Torymus sinensis following its release for Dryocosmus kuriphilus control in Europe

1. Arrival, establishment, and further dispersal of non-native natural enemies are considered essential for a successful biological control programme, while among the factors that may determine the success of such a programme, genetic diversity of the introduced population plays an important role in the establishment of a non-native species.
2. The Chinese parasitoid wasp Torymus sinensis Kamijo (Hymenoptera: Torymidae) was initially released in Europe in Italy to control biologically the Asian chestnut gall wasp Dryocosmus kuriphilus Yasumatsu (Hymenoptera: Cynipidae), and reduce the damage induced on sweet chestnut (Castanea sativa Miller). In the following years, T. sinensis was then released in numerous other European countries as a biological control agent of D. kuriphilus. Its presence has also been reported beyond the countries of release due to rapid natural dispersal.
3. To assess the post-release genetic diversity of D. kuriphilus, we screened T. sinensis populations from six European countries and tested the possibility of these populations suffering from frequently observed genetic effects that could threaten its successful establishment in Europe.
4. Our results exhibit that T. sinensis populations have suffered neither from the Allee effect nor from genetic bottleneck after their release and establishment in Europe, something that increases the possibility to effectively control D. kuriphilus in Europe.

     

Spatiotemporal dynamics of active flying Diptera predators among different farmland habitats

1. Farmland habitats comprise an arrangement of cropped, uncropped and natural vegetation among the farms. Despite the differences in these habitats' features, generalist highly mobile predators are more likely to explore them in time and space.
2. We investigated the spatiotemporal dynamics of the species of Dolichopodidae (Diptera) in organic vegetable farms because they are one of the most abundant generalist highly mobile predators in Brazilian agroecosystems.
3. We simultaneously sampled the abundance of Condylostylus Bigot and Chrysotus Loew adults (both Dolichopodidae) in the crop, fallow areas, agroforests and forest fragments within five organic farms for 2 years.
4. Predators preferred open-field habitats to agroforests and forest fragments. Probably, open-field habitats present more opportunities to prey foraging, resulting in higher population densities.
5. To the extent that abiotic conditions become more restrictive during the dry season, agroforests and forests act as breeding sites and shelter, thereby maintaining the predators' populations in the overall farmland habitat.
6. Both predatory genera occupy habitats with distinct features across time, forming a dynamic and contiguous population unit within the farm. Therefore, conservation biological control strategies in organic crops should consider the role of agroforests and forest fragments in species conservation beyond the plot level.

     

The giant willow aphid (Tuberolachnus salignus) and its effects on the survival and growth of willows

1. The giant willow aphid (Tuberolachnus salignus) is an invasive pest that can attain large populations on willows (Salix spp.). This has the potential to have a negative impact on the extensive use of willows for soil conservation, and as a source of pollen and nectar for honey bees in New Zealand.
2. A willow nursery field trial was established to evaluate the aphid populations, and the survival and growth of young plants of several willow species and hybrids, during two growing seasons from planting.
3. The willow species and hybrids varied widely in their susceptibility to the aphid, with large aphid populations and plant mortality in the most susceptible willows, and reductions in plant growth in all but aphid-resistant willows. The effects on the plants were not seen in the first season, but occurred during the second season.
4. The aphid can be expected to have some negative impacts in New Zealand, with reductions in growth of some willows commonly used for soil conservation, and for pollen and nectar for honey bees.

     

Tetanocera elata (Diptera: Sciomyzidae) Larvae Feed on Protected Slug Species Geomalacus maculosus (Gastropoda: Arionidae): First Record of Predation

The Family Sciomyzidae (Diptera) is one of the best studied groups of malacophagous insects containing some of the most important enemies of slugs. Larvae of the fly Tetanocera elata are known obligate feeders on slugs both as parasitoids and predators. We tested whether predatory larvae of T. elata can feed on the protected slug species Geomalacus maculosus, for which there appear to be no published records of natural enemies. Using an infra-red video camera, we recorded the behaviour of third instar T. elata in the presence of: 1) a single specimen of G. maculosus and 2) one specimen each of G. maculosus and Deroceras reticulatum, a known slug prey of T. elata. We describe the behaviour of the larvae where they killed and consumed G. maculosus and D. reticulatum in experiments 1 and 2 respectively. Since T. elata has been suggested as a potential biocontrol agent of pestiferous slugs, the possibility of predation on the protected species G. maculosus is discussed from this perspective.     

Effect of temperature on the larval stage of Tetanocera elata (Diptera: Sciomyzidae) – Potential biological control agent of pestiferous slugs

Due to the considerable losses caused by slugs in terms of agricultural production and revenue, there is an urgent need for a cost effective biological control agent. The malacophagous nature of the sciomyzid fly, Tetanocera elata (Fab.) makes it a possible contender to meet this demand. This study examined the effect of constant temperatures (14, 17, 20, 23, and 26 °C), in addition to ambient outdoor and laboratory temperatures on T. elata larval duration and predation. In general, the mean and median larval stage duration decreased as temperature increased with percentage survival for the overall larval stage (62%) greatest at 20 °C with a median duration of 44 days. There was no significant difference between temperatures with regard to the number of slugs killed per larva and while predation rate increased with increasing constant temperature, there was also no significant difference between the constant temperatures. Our results show that puparial weight can be used to predict the sex of adult flies prior to their emergence. The results are discussed in the context of the suitability of T. elata as a biological control agent of pestiferous slugs.     

Oviposition,adult longevity and temperature effects on the eggs of Tetanocera elata (Fab.) (Diptera: Sciomyzidae): a potential biocontrol agent for slugs

Pestiferous slugs in organic and conventional farming systems damage crops, reduce yield and quality, and reduce profits; however, no biological control agent that is both efficacious and inexpensive has yet been developed. One potential biological control agent is the slug‐feeding Tetanocera elata (Fab.), for which scant scientific data are currently available regarding optimum growing conditions. This study examined the effect of constant temperatures (14, 17, 20, 23 and 26°C) and ambient outdoor and laboratory temperatures on the duration of the egg stage of T. elata. In general, mean and median duration of incubation decreased as temperatures increased, with the highest (52%) and lowest (20%) hatch rates occurring at 14 and 26°C, respectively. Longevity and oviposition rates for T. elata are discussed in the context of mass biocontrol production systems, and possible reasons for low hatch rates for eggs stored at 2–3°C are discussed in the context of the phenology of the species.     

Genetic diversity of Helosciadium repens (Jacq.) W.D.J. Koch (Apiaceae) in Germany,a Crop Wild Relative of celery

• Helosciadium repens (Jacq.) W.D.J. Koch is threatened by genetic erosion. It is a Crop Wild Relative (CWR) of celery and celeriac and a potentially valuable genetic resource for plant breeding. The objective of this study was the analysis of distribution of genetic diversity with a set of selected populations in Germany. The results of the genetic analysis and data obtained during the site visits were used to identify a subset which was chosen to best represent the genetic diversity of H. repens in Germany. The chance of long‐term conservation by securing the identified populations in genetic reserves is distinctly possible.
• Seven hundred and fifteen individuals from 27 sites were assessed using six simple sequence repeat markers. Discriminant analysis of principal components was used to identify six clusters of genetically similar individuals. The complementary compositional genetic differentiation Δj was calculated to designate a subset of populations chosen to best represent the overall genetic diversity. Entry 18R (Δ_18R = 0.2498) represented its pooled remainder the best, while entry 22R (Δ_22R = 0.4902) differed the most from its complement.
• Based on the results of the genetic analysis and information regarding the current conservation status, 14 most appropriate wild populations for potential genetic reserve were identified. The used markers display a low level of genetic variation between the analyzed populations, and a split between Northern and Southern populations was observed.
• CWR species are essential genetic resources for plant breeding and food security. However, 11.5% of the European CWRs are threatened. Therefore, it is of utmost importance to determine their genetic compositions. These insights will provide the fundamental basis for making crucial decisions concerning future conservation strategies for H. repens.

     

Trophic web associated with the South American tomato moth Tuta absoluta: implications for its conservation biological control in Argentina

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Influence of plot characteristics and surrounding vegetation on the intra-plot spatial distribution of Empoasca vitis

• 1 Spatial distributions of adults and nymphs of Empoasca vitis were assessed during 3 years inside two adjacent vine plots having considerable intra‐plot variability, diversified natural ground cover and surrounding vegetation, and no insecticide application.
• 2 Geostatistical analysis confirmed that, in spite of repeated adult migrations, spatial distributions of summer populations were highly aggregated, similar every year and similar between adults and nymphs. Comparison of insect distribution with intra‐plot characteristics, such as vine plant vigour (leaf density and leaf chlorophyll concentration) and phenology, plot topography and surrounding vegetation, revealed that E. vitis clearly aggregates in areas with the most vigorous vine plants.
• 3 Even though the presence of natural enemies in the surrounding vegetation was confirmed by specific observations, we did not observe significant population decrease at the contiguous plot edges. Natural ground cover, together with the absence of insecticide, might allow the spreading and perennial conservation of E. vitis natural enemies inside the plots.
• 4 Clear adult aggregations observed along downwind woodlands suggest that this vegetation acts as a barrier and intercepts the adults flying passively across the plot. However, this surrounding vegetation could also serve as an alternative refuge when vine water deficit and vine foliage temperature increase.

     

Population size and habitat quality affect genetic diversity and fitness in the clonal herb <Emphasis Type="Italic">Cirsium dissectum</Emphasis>

Remaining populations of plant species in fragmented landscapes are threatened by declining habitat quality and reduced genetic diversity, but the interactions of these major factors are rarely studied together for species conservation. In this study, the interactions between population size, habitat quality, genetic diversity and fitness were investigated in 22 populations of the clonal herb Cirsium dissectum throughout the British Isles. Regression analysis was used to identify significant factors, and a structural equation model was developed to illustrate and integrate these interactions. It was found that smaller populations (measured as the total number of plants) had lower genetic diversity (proportion of polymorphic loci), and that reduced genetic diversity (allelic richness) had a negative impact on the survival of seedlings grown under standard conditions. Habitat quality also had a large effect on C. dissectum. Unmanaged sites with tall vegetation, no bare soil and higher nutrient levels had smaller populations of C. dissectum, but flowering was promoted. Flowering was suppressed in heavily grazed sites with short vegetation. Higher levels of bare soil and phosphorus both had a positive relationship with genetic diversity, but probably for distinctly different reasons: bare soil provides safe sites for establishment, whilst phosphorus may promote flowering and improve seed germination. In order to conserve C. dissectum, management needs to maintain site heterogeneity so that C. dissectum can flower and establishment gaps are still available for seedlings; when either component is reduced, negative feedbacks through reduced genetic diversity and individual fitness can be expected. This study therefore highlights the importance of considering both conservation genetics and habitat quality in the conservation of plant species.     

Prevalence,damage, management and insecticide resistance of stink bug populations (Hemiptera: Pentatomidae) in commodity crops

1. Pest management of stink bugs (Hemiptera: Pentatomidae) in soybean [Glycine max (L.) Merr.], corn (Zea mays L.) and cotton (Gossypium spp.) agroecosystems has become a major concern in several countries of the Americas.
2. In this review, we report an overview on geographical distribution, injury, damage and methods used to control (plant resistance mechanisms, biological control) the most important stink bugs in the Americas, with an emphasis on Brazil, the implications of the trend towards decreased susceptibility of stink bug populations to insecticides and the current difficulties of the management of these insect pests.
3. Currently, the Neotropical brown stink bug Euschistus heros (Fabricius) is less susceptible to organophosphate insecticides than in the past. A slight reduction in E. heros susceptibility to pyrethroids and, to a lesser extent, to neonicotinoids has also been observed. In addition, the green‐belly stink bug [Dichelops melacanthus (Dallas)] is more tolerant to the three classes of insecticides (neonicotinoids, organophosphates and pyrethroids) than E. heros.
4. Metabolic detoxification is involved in organophosphate, neonicotinoid and pyrethroid differences in susceptibility. Restricted availability of insecticides with different modes of action could favour the selection of resistant phenotypes in stink bug populations.

     

Micro‐climate determines oviposition site selection and abundance in the butterfly Pyrgus armoricanus at its northern range margin

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Time course study of Bactrocera oleae (Diptera: Tephritidae) pupae predation in soil: the effect of landscape structure and soil condition

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Population ecology of the endangered aquatic carnivorous macrophyte Aldrovanda vesiculosa at a naturalised site in North America

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Ten years after: Release cutting around old oaks still affects oak vitality and saproxylic beetles in a Norway spruce stand

1. It is often suggested to release oaks (Quercus robur) from competition, to ensure their survival and boost their conservational value. However, few studies have explored how long-lasting this effect is and how it affects saproxylic beetles.
2. Ten years after cutting, we investigated effects of different release cutting levels (high, medium, and no release) around 140-year-old retained oaks in a commercial forest with Norway spruce (Picea abies).
3. We evaluated oak vitality using crown and dead wood measurements. Saproxylic beetles were caught in window traps, identified to species level, and grouped according to their association with oak and/or Norway spruce.
4. Released oaks had more light, higher temperatures, greater crown growth, and less dead wood in the crown compared to the no-release control.
5. After 10 years we still found a higher abundance of oak-associated beetles and higher overall species richness of saproxylic beetles in the released oaks. Beetle species composition significantly differed between released oaks and control.
6. We suggest avoiding planting trees beneath retained oaks when regenerating conifer forests and to proceed with conservation management during subsequent thinning by removing regeneration under the oak crowns. We emphasize the benefits of monitoring the retained oaks to maintain tree vitality, habitat quality, and insolation.

     

Long-term within-basin isolation patterns,different conservation units,and interspecific mitochondrial DNA introgression in an amphipod endemic to the ancient Lake Skadar system,Balkan Peninsula

1. Investigation of biodiversity, including genetic diversity within species, is crucial for rational planning of nature conservation and species protection. Endemics or narrow-ranged taxa, sensitive to alteration of physical and chemical conditions, may serve as local bioindicators.
2. Homoeogammarus scutarensis is an endemic, cold-adapted amphipod crustacean, inhabiting fragmented spring habitats, within a relatively small area of the Lake Skadar basin. The basin is recently under heavy anthropogenic influence leading to habitat deterioration.
3. Genetic diversity within H. scutarensis was investigated using the mitochondrial cytochrome c oxidase subunit I and the nuclear 28S ribosomal RNA markers. Genetic diversity within the mitochondrial (mt)DNA appeared to be surprisingly high as for the limited spatial scale. The history of within-species divergence dates back at least to the Pliocene.
4. A case of interspecific mtDNA introgression from the endemic H. scutarensis to the widespread and partly sympatric Homoeogammarus thoni was observed in one of the studied populations.
5. Demographic analysis showed that the demography of H. scutarensis population has been stable, without evidence of expansion. Thus, we believe that H. scutarensis, responsive to environmental changes, is a proper model mirroring the conditions in sensitive habitats of the Lake Skadar basin. To protect ongoing evolutionary processes, the conservation measures for this species should take into account the complex fine-scale lineage endemism patterns. This case study may also provide a hint for planning conservation strategies in other geologically old spring systems.
6. Most of the localities where H. scutarensis occurs provide refugia for divergent mtDNA lineages, suggesting prolonged isolation between sites and independent evolutionary histories. We conclude that H. scutarensis is composed of two or three conservation units. One of them occupies the headwaters of the Crnojevića River and spring in its valley. The other is widespread throughout the sub-lacustrine springs and the Zeta Plain; however, a group of unique haplotypes is found in springs in the Podhum Bay. Their presence and distribution should be considered while planning any investments or conservation strategies.

     

High‐resolution distribution modeling of a threatened short‐range endemic plant informed by edaphic factors

1. Short‐range endemic plants often have edaphic specializations that, with their restricted distributions, expose them to increased risk of anthropogenic extinction.
2. Here, we present a modeling approach to understand habitat suitability for Ricinocarpos brevis R.J.F.Hend. & Mollemans (Euphorbiaceae), a threatened shrub confined to three isolated populations in the semi‐arid south‐west of Western Australia. The model is a maximum entropy species distribution projection constructed on the basis of physical soil characteristics and geomorphology data at approximately 25 m² (1 arc‐second) resolution.
3. The model predicts the species to occur on shallow, low bulk density soils that are located high in the landscape. The model shows high affinity (72.1% average likelihood of occurrence) for the known populations of R. brevis, as well as identifying likely locations that are not currently known to support the species. There was a strong relationship between the likelihood of R. brevis occurrence and soil moisture content that the model estimated at a depth of 20 cm.
4. We advocate that our approach should be standardized using publicly available data to generate testable hypotheses for the distribution and conservation management of short‐range endemic plant species for all of continental Australia.

     

Pre‐zygotic reproductive isolation between two synchronopatric Opuntia (Cactaceae) species in the Brazilian Chaco

• Opuntia (Cactaceae) is known for high rates of hybridization and ploidisation, resulting in the formation of new species. The occurrence of two sympatric and closely related species of Opuntia, O. elata and O. retrorsa, in Brazilian Chaco enabled us to test the hypothesis that pre‐zygotic reproductive isolation mechanisms operate in both species.
• We monitored the flowering period, as well as floral biology, and compared the morphological variation of floral structures through measurements, performed intra‐ and interspecific cross‐pollination tests, and recorded the guild of floral visitors and pollinators.
• Flowering was seasonal and highly synchronous. Floral biology exhibits similar strategies, and although floral morphology differs significantly in many of the compared structures, such morphological variation does not result in the selection of exclusive pollinators. Floral visitors and pollinators are oligolectic bees shared by both species. Opuntia elata and O. retrorsa are self‐compatible. While interspecific cross‐pollination (bidirectional) resulted in germination, the pollen tube did not penetrate the stigma.
• Opuntia elata and O. retrorsa are closely related; however, they are isolated and do not hybridise in Brazilian Chaco. We found that both have weak pre‐pollination barriers, but that they are strongly isolated by pollen–pistil incompatibility, i.e. post‐pollination barrier.

     

Parasitoid associated with Liriomyza huidobrensis (Diptera: Agromyzidae) outbreaks in tomato fields in Brazil

1. The knowledge of natural factors that affect pest populations is essential in predicting the occurrence of pest outbreaks and in developing integrated pest management programmes. Natural enemies, climatic elements and host plants are among the most important factors affecting pest dynamics.
2. Tomato (Solanum lycopersicum) is the second most consumed vegetable worldwide. The pea leaf miner Liriomyza huidobrensis (Diptera: Agromyzidae) is a major pest to the tomato in Brazil.
3. This study aimed to determine the main natural factors that regulate L. huidobrensis populations in tomato fields in Brazil.
4. Liriomyza huidobrensis densities were evaluated by directly counting the number of active mines on the basal leaf of the middle section of the plant canopy, and predators and parasitoids were assessed using the leaf‐beating‐against‐a‐tray technique. Eight commercial tomato fields were assessed over two years. The phenological growth stages of the tomato plants (vegetative and reproductive) were noted during the assessments.
5. Liriomyza huidobrensis populations peaked between the middle and end of the planting season.
6. Opius sp. (Hymenoptera: Braconidae) was the main natural enemy of L. huidobrensis.
7. Our results suggest that phenological growth stage and Opius sp. are associated with population dynamics of L. huidobrensis in tomato fields.
8. Therefore, integrated pest management programmes should aim to preserve populations of the parasitoid Opius sp.