Hans Peter Ravn

The spread of Ips typographus (L.) (Coleoptera, Scolytidae) attacks following heavy windthrow in Denmark, analysed using GIS

The population of the spruce bark beetle Ips typographus (L.) in the forest of Rold Skov was monitored in the years following a 1981 gale. All attacked standing trees, areas with windthrown trees, catches in pheromone traps, timing of salvage harvests, and stands exposed to attack were registered and mapped in 1982 and 1983. Three different indices for attack density in areas around windthrown trees, infested trees and pheromone traps were calculated using GIS (ArcView). The attack densities in 1983 around areas with windthrown trees salvaged after 1 July 1982 were significantly higher than for areas salvaged earlier. Attack densities around windthrown trees salvaged between 15 May and 1 July, just after the main spring-flight period, were the lowest. The maximum distance from an old attack to a new was 650 m and there was an old attack within 500 m of all new attacks. Attack densities around pheromone traps were not correlated with the number of beetles caught in the traps. The majority of the beetles emerging from an epidemic attack dispersed over short distances (i.e. <500 m) before entering a new host. This local dispersal may best be countered by removing old breeding sites/windthrown trees in the period between spring-flight and the emergence of the new generation, i.e. by using the windthrown trees as bait trees. Pheromone traps are not suitable as a sole protective measure to prevent further infestation.

The harlequin ladybird, Harmonia axyridis: global perspectives on invasion history and ecology

The harlequin ladybird, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), is native to Asia but has been intentionally introduced to many countries as a biological control agent of pest insects. In numerous countries, however, it has been introduced unintentionally. The dramatic spread of H. axyridis within many countries has been met with considerable trepidation. It is a generalist top predator, able to thrive in many habitats and across wide climatic conditions. It poses a threat to biodiversity, particularly aphidophagous insects, through competition and predation, and in many countries adverse effects have been reported on other species, particularly coccinellids. However, the patterns are not consistent around the world and seem to be affected by many factors including landscape and climate. Research on H. axyridis has provided detailed insights into invasion biology from broad patterns and processes to approaches in surveillance and monitoring. An impressive number of studies on this alien species have provided mechanistic evidence alongside models explaining large-scale patterns and processes. The involvement of citizens in monitoring this species in a number of countries around the world is inspiring and has provided data on scales that would be otherwise unachievable. Harmonia axyridis has successfully been used as a model invasive alien species and has been the inspiration for global collaborations at various scales. There is considerable scope to expand the research and associated collaborations, particularly to increase the breadth of parallel studies conducted in the native and invaded regions. Indeed a qualitative comparison of biological traits across the native and invaded range suggests that there are differences which ultimately could influence the population dynamics of this invader. Here we provide an overview of the invasion history and ecology of H. axyridis globally with consideration of future research perspectives. We reflect broadly on the contributions of such research to our understanding of invasion biology while also informing policy and people.

Climate drivers of bark beetle outbreak dynamics in Norway spruce forests

Bark beetles are among the most devastating biotic agents affecting forests globally and several species are expected to be favored by climate change. Given the potential interactions of insect outbreaks with other biotic and abiotic disturbances, and the potentially strong impact of changing disturbance regimes on forest resources, investigating climatic drivers of destructive bark beetle outbreaks is of paramount importance. We analyzed 17 time-series of the amount of wood damaged by Ips typographus, the most destructive pest of Norway spruce forests, collected across 8 European countries in the last three decades. We aimed to quantify the relative importance of key climate drivers in explaining timber loss dynamics, also testing for possible synergistic effects. Local outbreaks shared the same drivers, including increasing summer rainfall deficit and warm temperatures. Large availability of storm-felled trees in the previous year was also strongly related to an increase in timber loss, likely by providing an alternative source of breeding material. We did not find any positive synergy among outbreak drivers. On the contrary, the occurrence of large storms reduced the positive effect of warming temperatures and rainfall deficit. The large surplus of breeding material likely boosted I. typographus population size above the density threshold required to colonize and kill healthy trees irrespective of other climate triggers. Importantly, we found strong negative density dependence in I. typographus that may provide a mechanism for population decline after population eruptions. Generality in the effects of complex climatic events across different geographical areas suggests that the large-scale drivers can be used as early warning indicators of increasing local outbreak probability. Ecography (Less)

Spatial spread and infestation risk assessment in the Asian longhorned beetle, Anoplophora glabripennis

The Asian longhorned beetle (ALB), Anoplophora glabripennis (Motschulsky) (Coleoptera: Cerambycidae), is recognised as potentially one of the most damaging invasive insects in Europe and North America. International trade has increased the risk of accidental introduction of ALB. An eradication programme was initiated in Northeast Italy in June 2009, when an ALB infestation was discovered. The infestation was monitored by annual surveys of all host‐tree species growing in the eradication area. Infested trees were cut down and chipped. This study analyses the spatiotemporal distribution of infested trees for a 5‐year period from 2008 to 2012 using a generalised linear model approach. The results show that spread and infestation risk were significantly affected by (1) distance of suitable hosts from the nearest infested trees, (2) number of infested trees in the surroundings, and (3) annual variation. The significant differences in beetle dispersal between years reflect to some extent the onset of the eradication programme. The model allowed the estimation of arbitrary probability‐based management boundaries surrounding ALB‐infested trees. For example, the model estimated a 0.1% probability of attack on a suitable host tree 1 910 m from an existing attack.

Reproductive ecology of Heracleum mantegazzianum.

Reproduction is the most important event in a plant’s life cycle (Crawley, 1997). This is especially true for monocarpic plants, which reproduce only once in their lifetime, as is the case of Heracleum mantegazzianum Sommier & Levier. This species reproduces only by seed; reproduction by vegetative means has never been observed. As in other Apiaceae, H. mantegazzianum has unspecialized flowers, which are promiscuously pollinated by unspecialized pollinators. Many small, closely spaced flowers with exposed nectar make each insect visitor to the inflorescence a potential and probable pollinator (Bell, 1971). A list of insect taxa sampled on H. mantegazzianum (Grace and Nelson, 1981) shows that Coleoptera, Diptera, Hemiptera and Hymenoptera are the most frequent visitors. Heracleum mantegazzianum has an andromonoecious sex habit, as has almost half of British Apiaceae (Lovett-Doust and Lovett-Doust, 1982); together with perfect (hermaphrodite) flowers, umbels bear a variable proportion of male (staminate) flowers. The species is considered to be self-compatible, which is a typical feature of Apiaceae (Bell, 1971), and protandrous (Grace and Nelson, 1981; Perglova et al., 2006). Protandry is a temporal separation of male and female flowering phases, when stigmas become receptive after the dehiscence of anthers. It is common in umbellifers. Where dichogamy is known, 40% of umbellifers are usually protandrous, compared to only about 11% of all dicotyledons (Lovett-Doust and Lovett-Doust, 1982). Although protandry has traditionally been considered to be a mechanism of avoiding or reducing selfing, it is itself unlikely to guarantee outcrossing. However, when it is strongly developed, the male and female phases of a plant may be completely separated in time so that outcrossing is assured (Webb, 1981; Snow and Grove, 1995).

Seed germination, dispersal and seed bank in Heracleum mantegazzianum.

Since reproduction of Heracleum mantegazzianum Sommier & Levier is exclusively by seed (Tiley et al., 1996; Moravcova et al., 2005; Krinke et al., 2005), a detailed knowledge of its seed ecology is crucial for understanding this species’ invasive behaviour. This chapter summarizes available information on seed dormancy, pattern of germination, seed bank formation and dynamics, as well as the first solid data on the longevity of seed in the soil. Heracleum mantegazzianum has oval-elliptical broadly winged mericarps which are connected into pairs by carpophore (Fig. 5.1A) and split when mature (Holub, 1997). The mericarps are 6–18 mm long and 4–10 mm wide, and each contains one seed. The embryo is rudimentary (Martin, 1946) and surrounded by oily endosperm. Mature fruits have a strong resinous smell (Tiley et al., 1996). For simplicity the unit of generative reproduction and dispersal is termed ‘fruit’ throughout this chapter rather than the morphologically correct ‘mericarp’, and the term ‘seed’ is used when referring to germination.

The Natural Evolutionary Potential of Tree Populations to Cope with Newly Introduced Pests and Pathogens—Lessons Learned From Forest Health Catastrophes in Recent Decades

Emerging diseases often originate from host shifts of introduced pests or pathogens. Genetic resistance of the host to such diseases might be limited or absent due to the lack of coevolutionary history. We review six examples of major disease outbreaks on native tree species caused by different introduced pests and pathogens that led to large ecological and economical losses. In all six cases, high tree mortality was observed in natural populations with some surviving individuals exhibiting varying levels of genetic resistance. The abundance and distribution of resistant individuals and the heritability of resistance traits varies substantially among the cases. While chestnut blight wilt combined with ink disease has virtually eliminated mature Castanea dentata trees from North America, other severe emerging diseases, such as the ash dieback, have left many surviving trees and genetic variation in resistance to such diseases has been documented. We argue that the evolutionary potential of tree species to respond to new emerging diseases should not be underestimated. However, the risk of increased levels of inbreeding and loss of genetic diversity caused by low population sizes is a major concern. Maintenance of broad genetic diversity is an important issue in conservation and forestry management. We expect that future research targeting the genetic background of biotic resistance towards emerging diseases and the role of endophytic communities in protecting trees will facilitate the informed and science-based guidance required to manage and maintain forests with high resilience. International cooperation on limiting disease spread and the provision of early invasive pest or pathogen detection systems are essential.

Master of all traits: can we successfully fight giant hogweed?

The Caucasian Apiaceae giant hogweed, Heracleum mantegazzianum Sommier & Levier, has been with us in Europe for almost two centuries (see Jahodova et al., Chapter 1, this volume), but as is the case with most invasive species, it has received serious attention only in recent decades. A need for practical solutions to the problems posed by ecological and economic impacts, and scientific appeal associated with one of the most spectacular plant invasions in Europe, were the main reasons for giant hogweed becoming the subject of the international GIANT ALIEN project, which included participants from various parts of Europe with a wide range of expertise (Nielsen et al., 2005). It is not surprising that during the work on the GIANT ALIEN project some myths were unmasked: the plant is almost never truly biennial in the field (Pergl et al., Chapter 6, this volume); it does not produce over 100,000 fruits (Perglova et al., Chapter 4, this volume); the seeds do not survive for 15 years in the soil (Moravcova et al., Chapter 6, this volume); and it is not polycarpic (Pysek et al., Chapter 7, this volume). Surprisingly, the reputation of giant hogweed is even worse than it deserves – because of its attractiveness to the public it became a tabloid archetypal plant invader. It even attracted the attention of artists – long before scientists in Europe began to recognize the problem of this species, H. mantegazzianum was the subject of the song ‘The

Dreyfusia nordmannianae in Northern and Central Europe: potential for biological control and comments on its taxonomy

The silver fir woolly adelgid, Dreyfusia nordmannianae, is the most severe pest occurring on Abies nordmanniana in Central and Northern Europe. The adelgid is particularly damaging to trees in Christmas tree plantations. Dreyfusia nordmannianae is native to the Caucasus region and alien to Europe, where its natural enemy complex is less diverse compared to its area of origin. Mitochondrial and nuclear DNA sequence data from the samples of D. nordmannianae collected in its native range and Europe and from the samples of Dreyfusia piceae and Dreyfusia prelli collected in Europe and North America were examined for phylogenetic structure. There was no evidence of differentiation, suggesting that these Dreyfusia species have recently diverged or require taxonomic revision. All existing published and unpublished reports on natural enemies of D. nordmannianae in its place of origin were reviewed, with the purpose of selecting agents for classical biological control in Europe. The literature review suggested that the most promising agent was the Chamaemyiidae fly, Leucopis hennigrata. A new survey in D. nordmannianaes area of origin – Turkey, Georgia and Russia – showed that L. hennigrata was present in all localities. It was particularly abundant in Turkey, where its impact on populations of D. nordmannianae appears to be high. Its use as a biological control agent is discussed, as well as other biological control strategies.

The influence of small urban parks characteristics on bird diversity: A case study of Petaling Jaya, Malaysia

The capacity of small urban park to serve as urban habitats are rarely explored. This study analyses the characteristics of small urban parks and their potential to support urban biodiversity and ecological functions. Nine small urban parks were studied in Malaysia in August and September 2014 using the combined field survey method of structured observation and field measurements. The measured variables were divided into three broad categories of physical characteristics, species richness and human factors. Bird species richness and abundance were used as the indicators for assessing biodiversity. Pearson correlations and multiple regressions were conducted to analyse the relationships between variables and to identify which variables had a significant effect on bird species richness and abundance. The results demonstrated that park area and vegetation variables ( e.g. the percentage of tree canopy cover, open grass/ground, native-exotic plants) are the important predictors of bird species richness and abundance. The percentage of canopy covers (negative relation) and park area (positive relation) are the best predictors of bird species richness in small urban parks. Meanwhile, the best predictors for bird abundance are the percentage of canopy covers (negative relation) and native vegetation species (positive relation). Human activities and park surroundings have a marginal effect on the presence of bird species in small parks. Based on the findings, we provide two general recommendations that could probably increase bird diversity in small urban parks: (1) the park development and management plan should incorporate a social-ecological approach that can benefit both city-dwellers and bird species, and (2) findings from the study should be used to rethink the planting design and composition of especially newly established small urban parks.