Wouter Dekoninck

Introduction and Establishment of the Exotic Mosquito Species Aedes japonicus japonicus (Diptera: Culicidae) in Belgium

ABSTRACT n The establishment of the potential vector species Aedes (Finlaya) japonicus japonicus (Theobald) (Diptera: Culicidae) in southern Belgium is reported. The species was most likely introduced through the international trade in used tires. It was first collected in 2002 on the premises of a second-hand tire company and was sampled using different sampling methods in the two consecutive years (2003–2004). It was only in 2007 and 2008, during a national mosquito survey (MODIRISK), that its presence as adults and larvae at the above-mentioned site and at another tire company in the area was confirmed based on morphological and molecular identification. This discovery is the first record for Belgium of an exotic mosquito species that established successfully and raises the question on the need for monitoring and control. Considering the accompanying species found during the surveys, we also report here the first observation of Culex (Maillotia) hortensis hortensis (Ficalbi) in Belgium.

Identification of Belgian mosquito species (Diptera: Culicidae) by DNA barcoding

Since its introduction in 2003, DNA barcoding has proven to be a promising method for the identification of many taxa, including mosquitoes (Diptera: Culicidae). Many mosquito species are potential vectors of pathogens, and correct identification in all life stages is essential for effective mosquito monitoring and control. To use DNA barcoding for species identification, a reliable and comprehensive reference database of verified DNA sequences is required. Hence, DNA sequence diversity of mosquitoes in Belgium was assessed using a 658 bp fragment of the mitochondrial cytochrome oxidase I (COI) gene, and a reference data set was established. Most species appeared as well‐supported clusters. Intraspecific Kimura 2‐parameter (K2P) distances averaged 0.7%, and the maximum observed K2P distance was 6.2% for Aedes koreicus. A small overlap between intra‐ and interspecific K2P distances for congeneric sequences was observed. Overall, the identification success using best match and the best close match criteria were high, that is above 98%. No clear genetic division was found between the closely related species Aedes annulipes and Aedes cantans, which can be confused using morphological identification only. The members of the Anopheles maculipennis complex, that is Anopheles maculipennis s.s. and An. messeae, were weakly supported as monophyletic taxa. This study showed that DNA barcoding offers a reliable framework for mosquito species identification in Belgium except for some closely related species.

Microgeographical distribution of ants (Hymenoptera: Formicidae) in coastal dune grassland and their relation to the soil structure and vegetation

In this paper, we investigate the microgeographical distribution of ants nests in an intensively grazed dune pasture. A total of seven species were recorded. By the application of a forward multiple logistic regression we were able to determine nesting choice for the three common species Lasius niger, L. psammophilus and Myrmica specioides . The e rst could be identie ed as a pioneer species, while the two latter species, which are typical of dry, sandy dune grounds, differ slightly in their nesting preference. The effect of nest building on soil structure was investigated for a mound-building species ( Formica cunicularia) and for a non-mound-building species ( Lasius psammophilus ). Both species signie cantly decrease the thickness of the organic and water-capturing soil layer, while the mound-building species additionally affects the soil lime content (an increase) and the soil hardness (a decrease). Mound building in dense Calamagrostis vegetation also stimulates the germination of a characteristic and rare plant species, Thymus pulegioides .

Context-dependent specialization in colony defence in the red wood ant Formica rufa

In many species, specialized defence traits and strategies are crucial for surviving enemy attacks or securing resources. In numerous social insect lineages, a morphologically and behaviourally distinct soldier caste specializes in colony defence, with larger foragers typically engaging most in the aggressive defence of the colony against external threats. We hypothesized, however, that specialization in aggression could show vastly different patterns in the context of the defence against small intranidal parasites that prey on brood. This is because we expected that small, intranidal nurse workers could be better suited to defend against these parasitic myrmecophiles (=ant associates) due to their better matching size, high encounter rate and the high task switching costs that would occur if foragers had to carry out this task. Here, we present data that support this hypothesis from a study on specialization in defence against two parasites in the red wood ant Formica rufa. In particular, we show that small workers displayed the strongest aggressive behaviour towards the parasitic rove beetle Thiasophila angulata and the spider Thyreosthenius biovatus, and present evidence that small workers were better at preventing brood predation than larger workers. In addition, there was worker task specialization in defensive behaviour, with nurses and workers at nest entrances being more aggressive towards T.xa0angulata than extranidal foragers. We argue that this context-dependent specialization in aggression and nest defence was likely to be important in favouring the pronounced worker polymorphism observed in both this and other ant species and discuss our findings in relation to models for the evolution of division of labour and caste polymorphism in insect societies.

Invasive Process and Repeated Cross-Sectional Surveys of the Mosquito Aedes japonicus japonicus Establishment in Belgium

When accidentally introduced in a new location, a species does not necessarily readily become invasive, but it usually needs several years to adapt to its new environment. In 2009, a national mosquito survey (MODIRISK) reported the introduction and possible establishment of an invasive mosquito species, Aedes j. japonicus, in Belgium. First collected in 2002 in the village of Natoye from a second-hand tire company, then sampled in 2003 and 2004, the presence of adults and larvae was confirmed in 2007 and 2008. A repeated cross-sectional survey of Ae. j. japonicus was then conducted in 2009 in Natoye to study the phenology of the species on two different sites using three kinds of traps: Mosquito Magnet Liberty Plus traps, BG sentinel traps and CDC Gravid traps. An analysis of the blood meals was done on females to assess the epidemiological risks. Five species of mosquitos were caught using the different kind of traps: Culex pipiens, Cx torrentium, Anopheles claviger, Aedes geniculatus and Ae. j. japonicus, Cx pipiens being the most abundant. The CDC gravid traps gave the best results. Surprisingly Ae. j. japonicus was only found on one site although both sites seem similar and are only distant of 2.5 km. Its population peak was reached in July. Most of the engorged mosquitoes tested acquired blood meals from humans (60%). No avian blood meals were unambiguously identified. Larvae were also collected, mostly from tires but also from buckets and from one tree hole. Only one larva was found in a puddle at 100 m of the tire storage. A first local treatment of Ae. j. japonicus larvae population was done in May 2012 using Bacillus thuringiensis subsp. israelensis (Bti) and was followed by preventive actions and public information. A monitoring is also presently implemented.

Cross-realm assessment of climate change impacts on species’ abundance trends

Climate change, land-use change, pollution and exploitation are among the main drivers of species’ population trends; however, their relative importance is much debated. We used a unique collection of over 1,000 local population time series in 22 communities across terrestrial, freshwater and marine realms within central Europe to compare the impacts of long-term temperature change and other environmental drivers from 1980 onwards. To disentangle different drivers, we related species’ population trends to species- and driver-specific attributes, such as temperature and habitat preference or pollution tolerance. We found a consistent impact of temperature change on the local abundances of terrestrial species. Populations of warm-dwelling species increased more than those of cold-dwelling species. In contrast, impacts of temperature change on aquatic species’ abundances were variable. Effects of temperature preference were more consistent in terrestrial communities than effects of habitat preference, suggesting that the impacts of temperature change have become widespread for recent changes in abundance within many terrestrial communities of central Europe.

Do well-integrated species of an inquiline community have a lower brood predation tendency? A test using red wood ant myrmecophiles.

BackgroundA host infected with multiple parasitic species provides a unique system to test evolutionary and ecological hypotheses. Different parasitic species associated with a single host are expected to occupy different niches. This niche specialization can evolve from intraguild competition among parasites. However, niche specialization can also be structured directly by the host when its defence strategy depends on the parasite’s potential impact. Then it can be expected that species with low or no tendency to prey on host brood will elicit less aggression than severe brood parasitic species and will be able to integrate better in the host system.We examined this hypothesis in a large community of symbionts associated with European red wood ants (Formica rufa group) by testing the association between 1) level of symbiont integration (i.e. presence in dense brood chambers vs. less populated chambers without brood) 2) level of ant aggression towards the symbiont 3) brood predation tendency of the symbiont.ResultsSymbionts differed vastly in integration level and we demonstrated for the first time that relatively unspecialized ant symbionts or myrmecophiles occur preferentially in brood chambers. Based on their integration level, we categorize the tested myrmecophiles into three categories: 1) species attracted to the dense brood chambers 2) species rarely or never present in the brood chambers 3) species randomly distributed throughout the nest. The associates varied greatly in brood predation tendency and in aggression elicited. However, we did not find a correlation for the whole myrmecophile community between a) brood predation tendency and host’s aggression b) integration level and host’s aggression c) integration level and brood predation tendency.ConclusionsOur results indicate that red wood ants did not act more hostile towards species that have a high tendency to prey on brood compared to species that are less likely or do not prey on brood. We show that potentially harmful parasites can penetrate into the deepest parts of a social insect fortress. We discuss these seemingly paradoxical findings in relation to models on coevolution and evolutionary arms races and list factors which can make the presence of potentially harmful parasites within the brood chambers evolutionary stable.

Persistent inter- and intraspecific gene exchange within a parallel radiation of caterpillar hunter beetles (Calosoma sp.) from the Galápagos.

When environmental gradients are repeated on different islands within an archipelago, similar selection pressures may act within each island, resulting in the repeated occurrence of ecologically similar species on each island. The evolution of ecotypes within such radiations may either result from dispersal, that is each ecotype evolved once and dispersed to different islands where it colonized its habitat, or through repeated and parallel speciation within each island. However, it remains poorly understood how gene flow during the divergence process may shape such patterns. In the Galápagos islands, three phenotypically similar species of the beetle genus Calosoma occur at higher elevations of different islands, while lowlands are occupied by a fourth species. By genotyping all major populations within this radiation for two nuclear and three mitochondrial gene fragments and seven microsatellite markers, we found strong support that the oldest divergence separates the highland species of the oldest island from the remaining species. Despite their morphological distinctness, highland species of the remaining islands were genetically closely related to the lowland population on each island and within the same magnitude as lowland populations sampled at different islands. Repeated evolution of highland ecotypes out of the lowland species appears the most likely scenario and estimates of geneflow rates revealed extensive admixture among ecotypes within islands, as well as between islands. These findings indicate that gene exchange among the different populations and species may have shaped the phylogenetic relationships and the repeated evolution of these ecotypes.

Updated checklist of the mosquitoes (Diptera: Culicidae) of Belgium

ABSTRACT: n Most information about the systematics and bioecology of Belgian mosquitoes dates back from before 1950, and only scattered information was produced during the last decades. In this paper we review and update the list of mosquito species recorded in Belgium, from first report (1908) to 2015. Six genera and 31 species were recorded so far, including 28 autochthonous species and three invasive alien species recently recorded in Belgium: Aedes albopictus (Skuse 1894), Ae. japonicus japonicus (Theobald 1901), and Ae. koreicus (Edwards 1917). The six genera are Anopheles (five species), Aedes (sixteen species), Coquillettidia (one species), Culex (four species), Culiseta (four species), and Orthopodomyia (one species).

Distribution, behavioral dominance and potential impacts on endemic fauna of tropical fire ant Solenopsis geminata (Fabricius, 1804) (Hymenoptera: Formicidae: Myrmicinae) in the Galápagos archipelago

Abstract. Tropical fire ant (TFA), Solenopsis geminata (Fabricius, 1804), is considered as one of the most serious threats to the terrestrial fauna of Galápagos, yet little is known about its distribution and impact in the archipelago. We reviewed literature, studied museum specimens and sampled over 62 sites on ten islands and islets in order to update the distribution of TFA. Since the 1980s, species occurrences for TFA have increased from three to 115 localities, and the species is now recorded on seven islands and 11 islets. Sixty-six new records were registered since the last review in 2008, including the islets Bayas, Champion, Cuevas, and Eden. TFA seems to be present in a wide range of habitats with a clear predominance in human-disturbed zones. Our data, compiled with previous studies, suggest that TFA can behaviorally dominate other ants. TFA was collected on 28 nesting sites of endangered and/or endemic vertebrate species, where it constitutes a potential or proven threat. This study identifies potential invasion sites as well as endemic species that may further be impacted by this highly invasive ant. It also recommends regular monitoring to prevent further invasion.