Katarina M. Mikac

Genetic structure and dispersal patterns of the invasive psocid Liposcelis decolor (Pearman) in Australian grain storage systems.

Microsatellite markers were used to investigate the genetic structure among invasive L. decolor populations from Australia and a single international population from Kansas, USA to determine patterns of dispersal. Six variable microsatellites displayed an average of 2.5-4.2 alleles per locus per population. Observed (HO) heterozygosity ranged from 0.12-0.65 per locus within populations; but, in 13 of 36 tests, HO was less than expected. Despite low levels of allelic diversity, genetic structure estimated as theta was significant for all pairwise comparisons between populations (theta=0.05-0.23). Due to suspected null alleles at four loci, ENA (excluding null alleles) corrected FST estimates were calculated overall and for pairwise population comparisons. The ENA-corrected FST values (0.02-0.10) revealed significant overall genetic structure, but none of the pairwise values were significantly different from zero. A Mantel test of isolation by distance indicated no relationship between genetic structure and geographic distance among all populations (r2=0.12, P=0.18) and for Australian populations only (r2=0.19, P=0.44), suggesting that IBD does not describe the pattern of gene flow among populations. This study supports a hypothesis of long distance dispersal by L. decolor at moderate to potentially high levels.

Wing Shape and Size of the Western Corn Rootworm (Coleoptera: Chrysomelidae) is Related to Sex and Resistance to Soybean-Maize Crop Rotation

ABSTRACT The western corn rootworm, Diabrotica virgifera virgifera LeConte, is a major pest of maize in the United States and more recently, Europe. Understanding the dispersal dynamics of this species will provide crucial information for its management. This study used geometric morphometric analysis of hind wing venation based on 13 landmarks in 223 specimens from nine locations in Illinois, Nebraska, Iowa, and Missouri, to assess whether wing shape and size differed between rotated and continuously grown maize where crop rotation-resistant and susceptible individuals are found, respectively. Before assessing differences between rotation-resistant and susceptible individuals, sexual dimorphism was investigated. No significant difference in wing (centroid) size was found between males and females; however, females had significantly different shaped (more elongated) wings compared with males. Wing shape and (centroid) size were significantly larger among individuals from rotated maize where crop-rotation resistance was reported; however, cross-validation of these results revealed that collection site resistance status was an only better than average predictor of shape in males and females. This study provides preliminary evidence of wing shape and size differences in D. v. virgifera from rotated versus continuous maize. Further study is needed to confirm whether wing shape and size can be used to track the movement of rotation-resistant individuals and populations as a means to better inform management strategies.

Thermogenesis in decomposing carcasses

It is of fundamental importance in forensic entomology that the factors controlling carcass temperatures during decomposition are thoroughly understood. The thermal environment to which fly larvae are exposed is the primary influence on their growth rate, and hence affects any estimate of minimum time since death using such specimens in homicide investigations. To date, much of the entomological research on maggot masses has focused on their elevation of carcass temperatures, with very little focus on the bacteria associated with larval activity. The aim of this study was to investigate the heat associated with decay and the types of bacteria present during the decomposition of a carcass, both in the presence and in the absence of maggots. Three treatments were imposed: fresh, frozen and maggot-infested, each consisting of five replicate pig carcasses. Temperature measurements and bacterial swabs were taken from the gastro-intestinal region of each pig and temperatures and bacterial communities compared between treatments. All carcasses reached average maximum temperatures above 32 °C in a temperature controlled room set at 23 °C. Treatment had no statistically significant effect on the temperatures recorded in each carcass but did significantly affect the community structure of the bacteria. However, bacterial community structure varied across time. This study suggests that bacterial metabolism plays a significant role in carcass thermogenesis, and that maggot masses, while contributing to localised heating within the carcass, may have less of a role in elevating carcass temperatures than previously assumed.

Historical and Contemporary Population Genetics of the Invasive Western Corn Rootworm (Coleoptera: Chrysomelidae) in Croatia

ABSTRACT Classical population genetic analyses were used to investigate populations of the western corn rootworm, Diabrotica virgifera virgifera LeConte, in Croatia in 1996 and 2009. The number of alleles was low in both 1996 and 2009; however, more alleles were found in the putative populations surveyed in 2009. Croatia had only 51% of the alleles recorded from the United States and 69% from Europe. However, 10 private (unique) alleles were found in Croatia, which were not found previously in Europe. Most populations were out of Hardy—Weinberg equilibrium, although no linkage disequilibrium was found. Low to no genetic differentiation was found between population pairwise comparisons in 1996, with a greater level of differentiation found between populations sampled in 2009. Using the program STRUCTURE, a single genetic cluster was found for populations sampled in 1996 and 2009. However, two genetic clusters were detected when the 1996 and 2009 data were combined, indicating significant temporal differentiation. Isolation by distance pattern of gene flow characterized populations sampled in 2009 only when the most distant population of Ogulin (the head of the expansion front) was included in the analysis. When Ogluin was excluded from the 2009 analysis no isolation by distance pattern was found. The possible impact that control practices have had on the population genetics of D. v. virgifera in Croatia from 1996 to 2009 are discussed in light of the temporal genetics differences found.

Climatic, Edaphic Factors and Cropping History Help Predict Click Beetle (Coleoptera: Elateridae) (Agriotes spp.) Abundance.

It is assumed that the abundance of Agriotes wireworms (Coleoptera: Elateridae) is affected by agro-ecological factors such as climatic and edaphic factors and the crop/previous crop grown at the sites investigated. The aim of this study, conducted in three different geographic counties in Croatia from 2007 to 2009, was to determine the factors that influence the abundance of adult click beetle of the species Agriotes brevis Cand., Agriotes lineatus (L.), Agriotes obscurus (L.), Agriotes sputator (L.), and Agriotes ustulatus Schall. The mean annual air temperature, total rainfall, percentage of coarse and fine sand, coarse and fine silt and clay, the soil pH, and humus were investigated as potential factors that may influence abundance. Adult click beetle emergence was monitored using sex pheromone traps (YATLORf and VARb3). Exploratory data analysis was preformed via regression tree models and regional differences in Agriotes species’ abundance were predicted based on the agro-ecological factors measured. It was found that the best overall predictor of A. brevis abundance was the previous crop grown. Conversely, the best predictor of A. lineatus abundance was the current crop being grown and the percentage of humus. The best predictor of A. obscurus abundance was soil pH in KCl. The best predictor of A. sputator abundance was rainfall. Finally, the best predictors of A. ustulatus abundance were soil pH in KCl and humus. These results may be useful in regional pest control programs or for predicting future outbreaks of these species.

Multiple incursions and putative species revealed using a mitochondrial and nuclear phylogenetic approach to the Trogoderma variabile (Coleoptera: Dermestidae) trapping program in Australia.

The Warehouse beetle, Trogoderma variabile (Coleoptera: Dermestidae), is an internationally significant invasive pest of packed goods and stored grain. When it was first documented in Australia at Griffith, New South Wales, in 1977, an eradication campaign was initiated. After several years and considerable effort, the eradication campaign was abandoned. To monitor the presence and spread of T. variabile, surveys were carried out by government agencies in 1992 and 2002. When survey data was compared, it was concluded that the distribution of morphologically identified T. variabile had doubled in most Australian states. Here, we used samples from the 2002 survey to conduct a phylogenetic study using partial sequences of mitochondrial genes Cytochrome oxidase I and Cytochrome B, and the nuclear gene 18S, to examine the distribution and dispersal of T. variabile and detect the presence of misidentified species. Based on our molecular results, we show that only 47% of the samples analysed were T. variabile, and the remaining were a mixture of six putative species. In addition, T. variabile was found in only 78% of the trapping sites. We discuss the importance of correct diagnosis in relation to the eradication campaign.

Monitoring techniques of the western corn rootworm are the precursor to effective IPM strategies

BACKGROUND The western corn rootworm (WCR) is economically the most important pest of maize in Croatia. To predict WCR adult population abundance and variability, traditional, genetic and morphometric monitoring of populations was conducted over time through each phase of the WCR invasion process in Croatia. RESULTS Through traditional monitoring it was shown that WCR established their current population and reached economic densities after 14 years persisting in the study area. Regression-tree-based modelling showed that the best predictor of WCR adult abundance was the total amount of rainfall. Genetic monitoring indicated that genetic differentiation increased over time at the intrapopulation level, and morphometric monitoring indicated that wing morphotypes varied according to edaphic landscape changes. CONCLUSION Traditional population metric surveys are important in WCR integrated pest management (IPM), as such surveys can be effectively used to predict population abundances. Novel-use monitoring techniques such as genetics and geometric morphometrics can be used to provide valuable information on variation within and among populations. The monitoring techniques presented herein provide sound data to assist in the understanding of both WCR ecology and population genetics and may provide more information than that currently available using traditional techniques (e.g. sticky traps), and as such these additional techniques should be written into IPM for WCR.

Genetic Monitoring of Western Corn Rootworm (Coleoptera: Chrysomelidae) Populations on a Microgeographic Scale

ABSTRACT Microsatellite and mitochondrial DNA genetic monitoring of the western corn rootworm, Diabrotica virgifera virgifera LeConte, was undertaken in Croatia and Serbia from 1996 to 2011 and in the United States in 2011. The seven U.S. populations displayed the greatest allelic diversity. In Europe, the highest number of alleles was found in Rugvica, Croatia, and Surčin, Serbia, the two sites closest to international airports. The highest number of mitochondrial (mt) DNA haplotypes was recorded from Croatia in 1996. From 2009 to 2011, haplotype diversity declined, and Croatia and Serbia had a single fixed haplotype. U.S. continuous maize locations had one haplotype, while three haplotypes were found at crop-rotated locations. Minimal temporal genetic differentiation was found within and between populations in Europe and the United States. Bayesian cluster analysis identified two genetic clusters that grouped western corn rootworm from Croatia and Serbia separately from U.S. populations; however, these clusters were not neat, and numerous U.S. individuals had both European and U.S. ancestry, suggesting bidirectional gene flow. Bottlenecks were identified within most Croatian populations sampled in 1996, only two populations in 2009, and in all populations in 2011. Bottlenecks were not identified from Serbia from 1996 to 2011 or from the United States in 2011. As suspected Serbia was identified as the geographic source of western corn rootworm in Croatia. The temporal genetic monitoring undertaken allowed a deeper understanding of the population genetics of western corn rootworm in Croatia, neighboring Serbia, and its geographic source in the United States. The data obtained can be used to inform western corn rootworm pest management strategies in Croatia and Europe.

Arsenoriboside degradation in marine systems: The use of bacteria culture incubation experiments as model systems

Arsenoribosides (as glycerol; phosphate; sulfate and sulfonate) persisted in all bacteria-inoculated cultures irrespective of the source of bacteria (seawater, macro-algae surface) or the culture media used (DIFCO Marine Broth 2216 or novel blended Hormosira banksii tissue-based). This is unlike observations from traditional macro-algae tissue decomposition studies or in nature. In addition known arsenoriboside degradation products such as dimethylarsenoethanol (DMAE), dimethylarsenate (DMA), methylarsenate (MA) and arsenate - As(V) were not detected in any cultures. Consequently, the use of bacterial culture incubation experiments to explain the fate of arsenoribosides in marine systems appears limited as the processes governing arsenoriboside degradation in these experiments appear to be different to those in macro-algae tissue decomposition studies or in nature.

The degradation of arsenoribosides from Ecklonia radiata tissues decomposed in natural and microbially manipulated microcosms

We investigated the influence of microbial communities on the degradation of arsenoribosides from E. radiata tissues decomposing in sand and seawater-based microcosms. During the first 30 days, arsenic was released from decomposing E. radiata tissues into seawater and sand porewaters in all microcosms. In microcosms containing autoclaved seawater and autoclaved sand, arsenic was shown to persist in soluble forms at concentrations (9-18mg per microcosm) far higher than those present initially (,3mg per microcosm). Arsenoribosides were lost from decomposing E. radiatatissues in all microcosms with previously established arsenoriboside degradation products, such as thio-arsenic species, dimethylarsinoylethanol (DMAE), dimethylarsenate (DMA) and arsenate (As V ) observed in all microcosms. DMAE and DMA persisted in the seawater and sand porewaters of microcosms containing autoclaved seawater and autoclavedsand.Thissuggeststhatthedegradationstepfromarsenoribosides-DMAEoccursonalgalsurfaces,whereas the step from DMAE-As V occurs predominantly in the water-column or sand-sediments. This study also demonstrates that disruptions to microbial connectivity (defined as the ability of microbes to recolonise vacant habitats) result in alterations to arsenic cycling. Thus, the re-cycling of arsenoribosides released from marine macro-algae is driven by microbial complexity plus microbial connectivity rather than species diversity as such, as previously assumed. Additional keywords: algal decomposition, arsenic cycling, macro-algae, microbial ecology.