Marc Kenis

Harmonia axyridis in Europe: spread and distribution of a non-native coccinellid

Native to Asia, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) is considered an invasive alien ladybird in Europe and North America, where it was widely introduced as a biological control agent of aphids and coccids. In Europe, H. axyridis was sold by various biological control companies from 1995 in France, Belgium and the Netherlands, and was also intentionally released in at least nine other countries. It has spread very rapidly, particularly since 2002, and is now regarded as established in thirteen European countries. The established range extends from Denmark in the north to southern France in the south, and from Czech Republic in the east to Great Britain in the west. In this paper we map the spread and distribution of H. axyridis in Europe, and examine the situation on a country-by-country basis. We report first records of the species in five countries; Spain, Sweden, Denmark, Czech Republic and Italy; and first evidence of H. axyridis establishment in the latter three countries. Despite releases of H. axyridis in Portugal, Spain and Greece, there is little evidence of establishment in southern Europe. It is predicted that the spread and increase within Europe will continue and that H. axyridis will become one of the most widely distributed coccinellids in the continent.

Alien Terrestrial Invertebrates of Europe

Unlike other groups of animals and plants, no checklist of alien terrestrial invertebrates was available in any of the European countries until recently. Since 2002, such checklists were successively provided by Austria (Essl and Rabitsch 2002), Germany (Geiter et al. 2002), the Czech Republic (Sefrova and Lastu vka 2005), Scandinavia (NOBANIS 2007), the United Kingdom (Hill et al. 2005), Switzerland (Wittenberg 2006) and Israel (Roll et al. 2007). However, most European regions remained uncovered and, furthermore, comparisons between the existing lists were inherently difficult because they used different definitions of alien. Thus, estimating the importance of terrestrial alien invertebrates at the European level remained impossible, mostly because of poor taxonomic knowledge existed for several groups. By gathering taxonomists and ecologists specialised on most invertebrate taxa together with collaborators working at the national level in 35 European countries, the DAISIE project intended to fill this gap. However, a lack of European expertise in some taxonomic groups did not allow coverage of all the terrestrial invertebrates with the same level of precision. Data on insects were more reliable than those of other taxa, and consequently the analyses presented below will mostly refer to this group.

No saturation in the accumulation of alien species worldwide

Although research on human-mediated exchanges of species has substantially intensified during the last centuries, we know surprisingly little about temporal dynamics of alien species accumulations across regions and taxa. Using a novel database of 45,813 first records of 16,926 established alien species, we show that the annual rate of first records worldwide has increased during the last 200 years, with 37% of all first records reported most recently (1970–2014). Inter-continental and inter-taxonomic variation can be largely attributed to the diaspora of European settlers in the nineteenth century and to the acceleration in trade in the twentieth century. For all taxonomic groups, the increase in numbers of alien species does not show any sign of saturation and most taxa even show increases in the rate of first records over time. This highlights that past efforts to mitigate invasions have not been effective enough to keep up with increasing globalization.

Ecological effects and management of invasive alien Vespidae

Insect species associated with human goods continue to be accidentally introduced into new locations. A small proportion of these introduced species become invasive, causing a range of impacts in the receiving community. It is therefore important to evaluate the patterns of which species become invasive and which strategies are most successful in managing them. This review assesses the distribution, abundance, impact and management of the invasive Vespidae worldwide. We identified 34 vespid species known to be introduced around the world, but the seven most invasive species are all eusocial. Most introduced Vespidae only occur in one or two countries, but some areas have become geographic hotspots of invasion: Hawaii (15 species), North America (eight species), New Zealand (five species), Australia (four species) and South America (four species). Two invasive species, Vespula vulgaris and V. germanica have become particularly widespread and abundant with a range of impacts on biodiversity and ecosystem function. Other successful invasive species include several Polistes spp., which affect local biodiversity through direct predation or competition for food or space. Toxic baiting has been the most successful control strategy against invasive vespids to date, although this has mostly been small scale experimental management as it has proved difficult to develop commercial control products. Development of shelf-stable lures or baits combined with suitable toxins or pathogens could overcome some of the commercial impediments. Several attempts at biological control using parasitoids have not successfully reduced invasive wasp populations, although the biocontrol agent has only established in one case. The social structure of colonies and their high reproductive efficiency have facilitated invasion by these species, but it also means management at the population level will be difficult. This emphasises the need to prevent such invasions from occurring in the first place.

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.

Research on Parasitoids and Predators of Scolytidae – A Review

Scolytidae are major forest pests in Europe. For example, Ips typographus (L.) is considered the main pest problem in forestry in many central and northern European countries. Consequently, there is a long tradition of forest entomology studying various aspects of bark beetle ecology, including their natural enemy complexes, with a view to developing control methods. In recent years, the need for the development of sustainable pest management methods, taking into account the whole forest ecosystem, has enhanced the interest in natural mortality factors. Mills (1983) provided an extensive review of the natural enemies of conifer feeding bark beetles in Europe. In contrast, natural enemies of broadleaf-feeding species have never been reviewed. Furthermore, much research has been carried out in the last 20 years, in particular in fields such as host/prey location or tritrophic interactions. Other noteworthy reviews include two books by Hedqvist (1963; 1998) on chalcid and braconid parasitoids of Scolytidae in Sweden, and a publication by Nuorteva (1957) on parasitoids of bark beetles in Finland. Data are also available in general parasitoid and predator catalogues such as Thompson (1943), Herting (1973), and Noyes (2001), although these often repeat errors contained in primary publications. This review will focus primarily on parasitoids and predators of bark beetle species considered to be pests of living trees in Europe, although it may also consider relevant research in other continents. A list of these European species is given in chapter 1. Pathogens of scolytids are reviewed in another chapter (Wegensteiner, chapter 12).

Mitochondrial and microsatellite DNA markers reveal a Balkan origin for the highly invasive horse‐chestnut leaf miner Cameraria ohridella (Lepidoptera, Gracillariidae)

Biological invasions usually start with a small number of founder individuals. These founders are likely to represent a small fraction of the total genetic diversity found in the source population. Our study set out to trace genetically the geographical origin of the horse‐chestnut leafminer, Cameraria ohridella, an invasive microlepidopteran whose area of origin is still unkown. Since its discovery in Macedonia 25 years ago, this insect has experienced an explosive westward range expansion, progressively colonizing all of Central and Western Europe. We used cytochrome oxidase I sequences (DNA barcode fragment) and a set of six polymorphic microsatellites to assess the genetic variability of C. ohridella populations, and to test the hypothesis that C. ohridella derives from the southern Balkans (Albania, Macedonia and Greece). Analysis of mtDNA of 486 individuals from 88 localities allowed us to identify 25 geographically structured haplotypes. In addition, 480 individuals from 16 populations from Europe and the southern Balkans were genotyped for 6 polymorphic microsatellite loci. High haplotype diversity and low measures of nucleotide diversities including a significantly negative Tajima’s D indicate that C. ohridella has experienced rapid population expansion during its dispersal across Europe. Both mtDNA and microsatellites show a reduction in genetic diversity of C. ohridella populations sampled from artificial habitats (e.g. planted trees in public parks, gardens, along roads in urban or sub‐urban areas) across Europe compared with C. ohridella sampled in natural stands of horse‐chestnuts in the southern Balkans. These findings suggest that European populations of C. ohridella may indeed derive from the southern Balkans.

Host Volatile Attractants and Traps for Detection of Tetropium fuscum (F.), Tetropium castaneum L., and Other Longhorned Beetles (Coleoptera: Cerambycidae)

Abstract Cortical and sapwood volatiles were collected in situ from red spruce, Picea rubens (Sarg.), trees infested with Tetropium fuscum (F.), to determine the relative concentrations and enantiomer ratios of monoterpenes emitted. This information was used to create a synthetic “spruce blend” lure that was tested in various trap designs for efficacy in capturing T. fuscum, and Tetropium castaneum L. in field bioassays conducted on McNabs Island, Nova Scotia, in 2001 and 2002 and in Poland and Switzerland in 2002. Response of other cerambycid species was measured opportunistically. Cross-vane pan traps baited with spruce blend caught significantly more T. fuscum than unbaited traps or traps baited with racemic α-pinene, ethanol, or both. The addition of an ethanol lure to spruce blend–baited traps significantly increased capture of T. fuscum and T. castaneum. There were no significant differences among trap designs in mean catch of either Tetropium species. Spruce blend was also significantly attractive to Monochamus urussovii (Fischer) and, when paired with an ethanol lure, was significantly attractive to Spondylis buprestoides L. Asemum striatum L. was significantly attracted to racemic α-pinene but was not attracted to spruce blend or spruce blend plus ethanol. None of the lures tested were significantly attractive to Stictoleptura rubra L. or Alosterna tabacicolor (DeGeer).

Discrimination of Eubazus (Hymenoptera, Braconidae) sibling species using geometric morphometrics analysis of wing venation

Abstract Complexes of sibling and cryptic species are encountered frequently in parasitic Hymenoptera. Geometric morphometrics is a useful tool to detect minimal morphological variations, which often are undetectable by traditional morphological studies and even by classical morphometric approaches. We applied geometric morphometrics to wing venation to assess a complex case of sibling species in the genus Eubazus (Hymenoptera, Braconidae), parasitoids of conifer bark weevils of the genus Pissodes (Coleoptera, Curculionidae). The results and methods were compared with previous taxonomic studies on the same species, involving classical multivariate morphometrics, isoenzyme analyses, cross‐mating experiments and biological observations. Geometric morphometrics confirmed the previous division into four distinct species. However, this approach enabled the four species to be separated simultaneously, with a reliability of 98.6% for well‐classified females and 93.1% for males. A similar result in previous studies was obtained only by combining isoenzyme analyses and several canonical variate analyses, including many morphometric characters. Furthermore, measurements of wing venation were less time‐consuming, more reliable and required less prior knowledge of braconid taxonomy than the measurements needed for the classical morphometrics methods. Geometric morphometrics was used also to test the effect of host species on wing shape. Several female populations of Eubazus semirugosus originating from three different Pissodes spp. were compared. Significant differences were found in wing shape between conspecific Eubazus from different host species. The results are discussed in relation to reproductive isolation and genetic flow between the four species.

Non-crop plants used as hosts by Drosophila suzukii in Europe

The invasive spotted wing drosophila Drosophila suzukii, a fruit fly of Asian origin, is a major pest of a wide variety of berry and stone fruits in Europe. One of the characteristics of this fly is its wide host range. A better knowledge of its host range outside cultivated areas is essential to develop sustainable integrated pest management strategies. Field surveys were carried out during two years in Italy, the Netherlands and Switzerland. Fruits of 165 potential host plant species were collected, including mostly wild and ornamental plants. Over 24,000 D. suzukii adults emerged from 84 plant species belonging to 19 families, 38 of which being non-native. Forty-two plants were reported for the first time as hosts of D. suzukii. The highest infestations were found in fruits of the genera Cornus, Prunus, Rubus, Sambucus and Vaccinium as well as in Ficus carica, Frangula alnus, Phytolacca americana and Taxus baccata. Based on these data, management methods are suggested. Ornamental and hedge plants in the vicinity of fruit crops and orchards can be selected according to their susceptibility to D. suzukii. However, the widespread availability and abundance of non-crop hosts and the lack of efficient native parasitoids suggest the need for an area-wide control approach.