Gypsy Moth Populations Research Articles

How trait distributions evolve in populations with parametric heterogeneity

We consider the problem of determining the time evolution of a trait distribution in a mathematical model of non-uniform populations with parametric heterogeneity. This means that we consider only heterogeneous populations in which heterogeneity is described by an individual specific parameter that differs in general from individual to individual, but does not change with time for the whole lifespan of this individual. Such a restriction allows obtaining a number of simple and yet important analytical results. In particular we show that initial assumptions on time-dependent behavior of various characteristics, such as the mean, variance, or coefficient of variation, restrict severely possible choices for the exact form of the trait distribution. This fact must be taken into account for both model formulation and, especially, for testing theoretical models against available real world data. We illustrate our findings by in-depth analysis of the variance evolution and specific examples from population ecology and mathematical epidemiology. We also reanalyze a well known mathematical model for gypsy moth population and show that the knowledge of how trait distributions evolve allows producing oscillatory behaviors for highly heterogeneous populations.

What can be Concluded from COI Gene Data in Limited History Specimen: A sample analysis of a forest pest,Lymantria dispar

Nowadays, more and more biodiversity and biogeography studies are conducted with the help of gene sequences. Fresh samples obtained using consistent collection methods can provide DNA for analysis and yield the current status of target species. As there are often no historical samples providing a timescale, it is often difficult to draw conclusions and to provide an evolutionary explanation of the observed biogeographical patterns because of a lack of evidence. The huge natural history specimen collections in museums could possibly provide this information. The gypsy moth, Lymantria dispar (Linnaeus) is a worldwide forest pest species. Our analyses of mitochondrial COI gene sequencing data in specimens from disparate locations revealed previously unknown genetic relationships in gypsy moth populations across space (in and around China) and time (1955–2012). We recovered 103 full-length COI gene sequences from eight fresh samples and from 95 Lymantria dispar collection specimens that had been captured between 1955 and 1996. Combining 103 full-length COI gene sequences with 146 COI gene sequences from Genbank (https://www.ncbi.nlm.nih.gov) or DNA barcode libraries, we analyzed the genetic differentiation, gene flow and haplotypes (special sequences from individuals) within the gypsy moth populations in order to reflect the genetic structure and population dynamics of this pest. Twenty-five previously unknown haplotypes were discovered. Regional populations from the same location, but collected at different times, showed high genetic diversity. In some geographical populations (Heilongjiang, Liaoning and Beijing populations), the genetic differentiation was greatest in 1979, but much lower in 1992 and 2012. This study is an example that shows how specimen collections can be useful to complete gaps in biodiversity studies carried out through genetic sequencing.

A Phenology Model for Asian Gypsy Moth Egg Hatch.

Phenology models are useful tools in pest management interventions, biosecurity operations targeting alien invaders, and answering questions regarding the potential for range expansion/shift. The Gypsy Moth Life Stage model (GLS) has been used to predict the invasive range of the North American gypsy moth (Lymantria dispar dispar Linnaeus [Lepidoptera: Erebidae]) in North America and New Zealand. It has been used to examine the role of supra-optimal temperatures in range expansion/stasis/retraction. However, GLS has also been used where the target organism is the Asian subspecies L. d. asiatica Vnukovskij, despite observed differences between the predominant phenotypes of the two subspecies in the temperature requirements for egg hatch and the absence of egg phenology model parameters specific to the Asian phenotype. Here we describe the results of temperature and exposure duration on the timing of Asian gypsy moth egg hatch, and we present phenology model parameters for the Asian phenotype. Sum of squared differences (observed minus predicted day of median egg hatch) was reduced from 7,818 d2 (North American parameters) to 178 d2. Days of simulated median egg hatch differed from the observed days by 0-7 d (x¯=0.2;SD=3.1). The pattern of simulated egg hatch closely mimicked the irregular pattern of observed egg hatch from the temperature regimes of our experiment. Egg hatch is arguably the most important life cycle event in gypsy moth population suppression/eradication interventions and in estimating their potential invasive range. The model parameters described here produce accurate predictions of Asian gypsy moth egg hatch.

Mitochondrial Gene Sequence (COI) Reveals the Genetic Structure and Demographic History of Lymantria dispar (Lepidoptera: Erebidae: Lymantriinae) in and around China.

The gypsy moth, Lymantria dispar, is among the most destructive quarantine pests of forests. Here, we reconstructed the genetic structure and determined the population differentiation of gypsy moths across its distribution range at different times. This information could be used to both improve the prevention and detection of gypsy moths in the field. Using 31 newly designed species-specific primers targeting fragments of 216–1102 bp, we identified 103 full-length cytochrome oxidase subunit I (COI) gene sequences from eight fresh samples and 95 L. dispar specimens collected between 1955 and 1996, mainly in China. Combining 103 full-length COI gene sequences with 146 COI gene sequences from Genbank or DNA barcode libraries, we analyzed the genetic differentiation, gene flow and haplotypes between gypsy moth populations in order to reflect the genetic structure and population dynamics of gypsy moths. We discovered 25 previously unknown haplotypes from old gypsy moth specimens. We found that the genetic diversity among gypsy moth populations (collected in the same region at different time points) was relatively high. Furthermore, the genetic structure of Chinese geographical populations (Heilongjiang, Liaoning, Beijing) in different years was distinct. Our results suggested that some gypsy moths in China showed the genetic affinity with European gypsy moths (a sub-species of gypsy moths found mainly in Europe).

Evolutionary genomics of gypsy moth populations sampled along a latitudinal gradient.

The European gypsy moth (Lymantria dispar L.) was first introduced to Massachusetts in 1869 and within 150years has spread throughout eastern North America. This large-scale invasion across a heterogeneous landscape allows examination of the genetic signatures of adaptation potentially associated with rapid geographical spread. We tested the hypothesis that spatially divergent natural selection has driven observed changes in three developmental traits that were measured in a common garden for 165 adult moths sampled from six populations across a latitudinal gradient covering the entirety of the range. We generated genotype data for 91,468 single nucleotide polymorphisms based on double digest restriction-site associated DNA sequencing and used these data to discover genome-wide associations for each trait, as well as to test for signatures of selection on the discovered architectures. Genetic structure across the introduced range of gypsy moth was low in magnitude (FST =0.069), with signatures of bottlenecks and spatial expansion apparent in the rare portion of the allele frequency spectrum. Results from applications of Bayesian sparse linear mixed models were consistent with the presumed polygenic architectures of each trait. Further analyses indicated spatially divergent natural selection acting on larval development time and pupal mass, with the linkage disequilibrium component of this test acting as the main driver of observed patterns. The populations most important for these signals were two range-edge populations established less than 30 generations ago. We discuss the importance of rapid polygenic adaptation to the ability of non-native species to invade novel environments.

Allee effects under climate change

Understanding how climate change affects population dynamics is crucial for assessing future of biodiversity. Here I ask how can Allee effects, occurring when mean individual fitness is reduced in rare populations, respond to increasing temperature. Despite the role Allee effects play in ecology of invasive, threatened and harvested populations, impacts of climate change on Allee effects are practically unknown. Analysis of two population models reveals that whereas the Allee effect driven by predation generally weakens as temperature increases, the Allee effect due to need of finding mates is predicted to become stronger when warming occurs. For the former model, the metabolic theory suggests that with increasing temperature prey growth rate should increase faster than predator attack rate. Increasing temperature thus weakens the Allee effect. In the latter, gypsy moth population model, mating rate increases with warming due to enhanced female−male encounter rate and temperature‐induced modifications in female and male adult emergence distributions. However, male and female mortality rates increase, too and the net effect is strengthening of the Allee effect. These results have repercussions also for pest control, indicating that augmentation of biocontrol agents may perhaps be not as effective as using pesticides or disrupting mating.

Phenology of Parasetigena silvestris (Diptera: Tachinidae), gypsy moth (Lymantria dispar) (Lepidoptera: Lymantriidae) larval parasitoid and its efficiency for parasitisation

ABSTRACTParasetigena silvestris is a univoltine, solitary, larval endoparasitoid which lays its eggs on the surface of gypsy moth larvae. Field collection of the host larvae (2nd through 5th instar) from an artificially established gypsy moth population were made to compare stage specific parasitism between larvae without and with P. silvestris tachinid eggs. The tachinid oviposition rate detected was highest in second instar larvae, and then decreased as larvae developed toward full maturity. The opposite was true for tachinid parasitoid emergence which had no emergence from second through third host instar larvae. Fourth instar gypsy moth larvae, however, experienced significantly higher parasitism by P. silvestris in the larvae with eggs than those without the eggs. The braconid wasp Cotesia melanoscelus caused significantly higher parasitism in early instar larvae with P. silvestris eggs than in those without the eggs. The tachinid prefers to lay more eggs on parasitised larvae by the braconid even though the braconid is a superior competitor to the fly during multiparasitism. Factors influencing parasitism rates by P. silvestris such as host-parasitoid synchronisation and the multiparasitism interaction with C. melanoscelus are discussed.

Динамика популяции непарного шелкопряда в лесостепных дубравах Европейской России

Динамика популяции непарного шелкопряда в лесостепных дубравах Европейской России

Ispitivanje prisustva u zemljištu, vijabilnosti i infektivnog potencijala azigospora entomopatogene gljive Entomophaga maimaiga

Entomophaga maimaiga is one of the best-known gypsy moth pathogens with increasing importance in the biological control aimed at reducing the population of this defoliator. The territory of the Republic of Serbia is a very favorable gypsy moth habitat, and the problems caused by its larvae during the periods of outbreaks are so great that they can lead to forest defoliation and forest health deterioration. In the Republic of Serbia, E. maimaiga was first recorded in 2011 (as a new species in the microflora of Serbia) during the gypsy moth outbreak (2009-2014), which was the last to date. In 2011, numerous dead caterpillars were found on and around trees in oak and beech stands of the Belgrade and Valjevo regions in Serbia. Subsequent laboratory analyses revealed that they contained azygospores and conidia of this fungus. The assisted introduction of E. maimaiga was carried out in Compartments 28 and 30 of the FMU Avala on Mt. Avala in 2011. It led to an epizootic in the following year and stopped the outbreak of the gypsy moth in the area. Since it has been seven years since the outbreak, we tested the viability and infectivity of E. maimaiga azygospores obtained from the soil samples from Avala Mountain where its assisted introduction was carried out. We used larvae from the laboratory gypsy moth population and applied the bioassay method. The results show that azygospores are present in the given soil samples, they are viable and their infectivity is conserved. It can be concluded that in the case of an outbreak of gypsy moth populations in the future, they will exhibit their entomopathogenic effect

ПРИМЕНЕНИЕ СМЕШАННЫХ ИНФЕКЦИЙ ДЛЯ СДЕРЖИВАНИЯ ЧИСЛЕННОСТИ НЕПАРНОГО ШЕЛКОПРЯДА (LYMANTRIA DISPAR L.)

ПРИМЕНЕНИЕ СМЕШАННЫХ ИНФЕКЦИЙ ДЛЯ СДЕРЖИВАНИЯ ЧИСЛЕННОСТИ НЕПАРНОГО ШЕЛКОПРЯДА (LYMANTRIA DISPAR L.)

Limited Genetic Structure of Gypsy Moth Populations Reflecting a Recent History in Europe.

The gypsy moth, Lymantria dispar, a prominent polyphagous species native to Eurasia, causes severe impacts in deciduous forests during irregular periodical outbreaks. This study aimed to describe the genetic structure and diversity among European gypsy moth populations. Analysis of about 500 individuals using a partial region of the mitochondrial COI gene, L. dispar was characterized by low genetic diversity, limited population structure, and strong evidence that all extant haplogroups arose via a single Holocene population expansion event. Overall 60 haplotypes connected to a single parsimony network were detected and genetic diversity was highest for the coastal populations Croatia, Italy, and France, while lowest in continental populations. Phylogenetic reconstruction resulted in three groups that were geographically located in Central Europe, Dinaric Alps, and the Balkan Peninsula. In addition to recent events, the genetic structure reflects strong gene flow and the ability of gypsy moth to feed on about 400 deciduous and conifer species. Distinct genetic groups were detected in populations from Georgia. This remote population exhibited haplotypes intermediate to the European L. dispar dispar, Asian L. dispar asiatica, and L. dispar japonica clusters, highlighting this area as a possible hybridization zone of this species for future studies applying genomic approaches.

Geographic Variation in Larval Metabolic Rate Between Northern and Southern Populations of the Invasive Gypsy Moth.

Thermal regimes can diverge considerably across the geographic range of a species, and accordingly, populations can vary in their response to changing environmental conditions. Both local adaptation and acclimatization are important mechanisms for ectotherms to maintain homeostasis as environments become thermally stressful, which organisms often experience at their geographic range limits. The spatial spread of the gypsy moth (Lymantria dispar L.) (Lepidoptera: Erebidae) after introduction to North America provides an exemplary system for studying population variation in physiological traits given the gradient of climates encompassed by its current invasive range. This study quantifies differences in resting metabolic rate (RMR) across temperature for four populations of gypsy moth, two from the northern and two from southern regions of their introduced range in North America. Gypsy moth larvae were reared at high and low thermal regimes, and then metabolic activity was monitored at four temperatures using stop-flow respirometry to test for an acclimation response. For all populations, there was a significant increase in RMR as respirometry test temperature increased. Contrary to our expectations, we did not find evidence for metabolic adaptation to colder environments based on our comparisons between northern and southern populations. We also found no evidence for an acclimation response of RMR to rearing temperature for three of the four pairwise comparisons examined. Understanding the thermal sensitivity of metabolic rate in gypsy moth, and understanding the potential for changes in physiology at range extremes, is critical for estimating continued spatial spread of this invasive species both under current and potential future climatic constraints.

Mechanical thinning to restore oak savanna promoted predator assemblages of gypsy moth pupae in Michigan

AbstractThe United States Forest Service conducted an oak savanna restoration using thinning and prescribed burning in the Manistee National Forest in Michigan to provide additional habitat for species dependent on this rare community type, including the Karner blue butterfly (Lycaeides melissa samuelis). Because the Karner blue butterfly is a federally endangered species, managers cannot spray Bt‐k (Bacillus thurigiensis var kurstaki) in areas undergoing restoration to control exotic invasive defoliators, such as European gypsy moths (Lymantria dispar). Although gypsy moths are invasive in North America, several native predators, such as white‐footed mice (Peromyscus leucopus), other small mammals and invertebrates, help keep gypsy moth populations at nondestructive levels. The present study investigated whether the small mammal community and gypsy moth predation rates were affected by the type of mechanical forest thinning method (bulldozer, masticator, shear cutter) used during an oak savanna restoration at two sites in Michigan within the suppression zone in 2010 and 2011. Predation rates on gypsy moth pupae were higher in bulldozer and shear cutter thinned compared with control plots at both sites in 2010. White‐footed mice relative abundance was significantly higher in thinned compared with control plots at one site in 2010 and 2011. Thinning maintained or promoted white‐footed mice abundance, which will maintain or enhance predation on gypsy moth pupae during oak savanna restoration.

Phytophagous larvae occurring in Central and Southeastern European oak forests as a potential host of Entomophaga maimaiga (Entomophthorales: Entomophthoraceae) - A field study.

We evaluated the presence and impact of Entomophaga maimaiga on both target and non-target phytophagous larvae. All six study plots, with low gypsy moth population density, were situated in Central and Southeastern European oak forests and E. maimaiga had previously been reported from these plots. Totally, 45 of 4,045 (1.13%) collected non-target larvae died due to fungal infections. No non-target insect specimen was infected by E.maimaiga, although the presence of the pathogen could not be fully excluded in three cadavers. Out of 1,780L.dispar larvae collected, 15individuals (0.84%) were infected by E.maimaiga.

Relationship between efficacy of mating disruption and gypsy moth density

ABSTRACTMating disruption tactics involve the deployment of pheromones to interfere with mate finding behaviors in insect populations. This management strategy is the dominant one used against expanding gypsy moth populations in the United States, and historically it has been assumed to be most effective against low-density populations. Operationally, mating disruption is used in areas where the season-long trap catch is <30 males/trap, however the maximum population density at which mating disruption is effective remains unknown. We analysed historical gypsy moth mating disruption treatment data from 2000 to 2010, and used this information to guide the mating disruption field studies conducted from 2012 to 2015 against artificially-created populations of various densities, from 0 to 116 males/trap/day. We observed that mating disruption tactics at a dose of 15 g AI/ha were effective against gypsy moth populations with a season-long trap catch of at least 115 males/trap. This research highlights the utility of mating disruption in higher gypsy moth densities than what is currently recommended in management programs.

Scale-dependent portfolio effects explain growth inflation and volatility reduction in landscape demography

Population demography is central to fundamental ecology and for predicting range shifts, decline of threatened species, and spread of invasive organisms. There is a mismatch between most demographic work, carried out on few populations and at local scales, and the need to predict dynamics at landscape and regional scales. Inspired by concepts from landscape ecology and Markowitz's portfolio theory, we develop a landscape portfolio platform to quantify and predict the behavior of multiple populations, scaling up the expectation and variance of the dynamics of an ensemble of populations. We illustrate this framework using a 35-y time series on gypsy moth populations. We demonstrate the demography accumulation curve in which the collective growth of the ensemble depends on the number of local populations included, highlighting a minimum but adequate number of populations for both regional-scale persistence and cross-scale inference. The attainable set of landscape portfolios further suggests tools for regional population management for both threatened and invasive species.

Assessing the potential of genotyping‐by‐sequencing‐derived single nucleotide polymorphisms to identify the geographic origins of intercepted gypsy moth (Lymantria dispar) specimens: A proof‐of‐concept study

AbstractForest invasive alien species are a major threat to ecosystem stability and can have enormous economic and social impacts. For this reason, preventing the introduction of Asian gypsy moths (AGM; Lymantria dispar asiatica and L. d. japonica) into North America has been identified as a top priority by North American authorities. The AGM is an important defoliator of a wide variety of hardwood and coniferous trees, displaying a much broader host range and an enhanced dispersal ability relative to the already established European gypsy moth (L. d. dispar). Although molecular assays have been developed to help distinguish gypsy moth subspecies, these tools are not adequate for tracing the geographic origins of AGM samples intercepted on foreign vessels. Yet, this type of information would be very useful in characterizing introduction pathways and would help North American regulatory authorities in preventing introductions. The present proof‐of‐concept study assessed the potential of single nucleotide polymorphism (SNP) markers, obtained through genotyping by sequencing (GBS), to identify the geographic origins of gypsy moth samples. The approach was applied to eight laboratory‐reared gypsy moth populations, whose original stocks came from locations distributed over the entire range of L. dispar, comprising representatives of the three recognized subspecies. The various analyses we performed showed strong differentiation among populations (FST ≥ 0.237), enabling clear distinction of subspecies and geographic variants, while revealing introgression near the geographic boundaries between subspecies. This strong population structure resulted in 100% assignment success of moths to their original population when 2,327 SNPs were used. Although the SNP panels we developed are not immediately applicable to contemporary, natural populations because of distorted allele frequencies in the laboratory‐reared populations we used, our results attest to the potential of genomewide SNP markers as a tool to identify the geographic origins of intercepted gypsy moth samples.

DNA insecticides: the lethal potency of LdMNPV IAP-2 gene antisense oligonucleotides in pre-infected gypsy moth (Lymantria dispar L.) larvae

ABSTRACTIn this study, we designed and analysed the insecticidal effectiveness of two short single-stranded DNA fragments from LdMNPV (Lymantria dispar multicapsid nuclear polyhedrosis virus) IAP-2 gene. Our results show that the ssDNA fragments from the antisense region is selectively lethal, and rapidly decreases the population of second instar gypsy moth (Lymantria dispar L.) larvae one day post-treatment (Control-H2O group vs oligoAn group, χ2 = 5; p < 0.05) when infected with LdMNPV as a trigger, before treatment through feeding with 75 pmol/µl of synthesized fragments from LdMNPV IAP-2 gene. Data analysis on larvae biomass did not show significant influence in all groups of the experiment when compared with the Control-H2O group. Relatively, our preliminary evaluation of biochemical parameters (total glucose and total protein concentrations) did not show significant response to the applied ssDNA oligonucleotides. Our conclusive remarks based on mortality data support the concept that antisense oligonucleotides from LdMNPV IAP-2 gene can act as an insecticide against pre-infected gypsy moth larvae.

Effects of Temperature on Development of Lymantria dispar asiatica and Lymantria dispar japonica (Lepidoptera: Erebidae).

Periodic introductions of the Asian subspecies of gypsy moth, Lymantria dispar asiatica Vnukovskij and Lymantria dispar japonica Motschulsky, in North America are threatening forests and interrupting foreign trade. Although Asian gypsy moth has similar morphology to that of European and North American gypsy moth, it has several traits that make it a greater threat, the most important being the flight capability of females. Asian gypsy moth is not yet established in North America; however, infestations have been detected multiple times in Canada and the United States. To facilitate detection and eradication efforts, we evaluated the effect of a range of temperatures on development time, survivorship, and fertility of eight populations of Asian gypsy moth. There were significant impacts of temperature and population on these life history characteristics. The larval developmental rate increased with temperature until it reached an optimum at 29 °C. Larvae experienced significant molting problems at the highest and lowest temperatures tested (10 °C and 30 °C). At 30 °C, female fitness was markedly compromised, as evidenced by reduced fecundity and fertility. This suggests that development and survival of Asian gypsy moth may be limited by summer temperature extremes in the Southern United States. We also determined the degree-day requirements for two critical life stages and two populations of Asian gypsy moth, which represent the extremes in latitude, to predict the timing for biopesticide application and adult trap deployment. Our data will benefit pest managers in developing management strategies, pest risk assessments, and timing for implementation of management tactics.

Landscape-Level Patterns of Elevated FS1 Asian Allele Frequencies in Populations of Gypsy Moth (Lepidoptera: Erebidae) at a Northern U.S. Boundary.

From a regulatory perspective, Asian gypsy moth is a species complex consisting of three species of Lymantria and two subspecies of Lymantria dispar (L.), differing from the European subspecies, L. dispar dispar (L.), by having consistently flight-capable females. As such, the invasion potential in North America is thought to exceed that of European gypsy moth. USDA-APHIS therefore has a monitoring program to detect Asian gypsy moth at high-risk introduction pathways. Molecular markers are used to improve the diagnosis of Asian gypsy moth. One such marker, which targets the FS1 locus, detects an allele, FS1-A, prevalent in Asian populations but occurring at low frequencies (3-6%) throughout the European gypsy moth's range in North America. However, some locales, such as Minnesota, exhibit elevated FS1-A frequencies. We studied the distribution of the FS1-A allele in northern Minnesota, 2013-2014, assessing spatial patterns in the distribution of the FS1-A allele using Moran's I and using spatial regression techniques to examine if the FS1-A allele was associated with putative movement pathways. We also used time series analysis to discern if temporal patterns in FS1-A or possible introduction events occurred. Our results indicated that FS1-A occurred randomly in space and time. We found no evidence that elevated FS1-A frequencies were associated with movement pathways or possible immigration events into this region over the two years. Elevated frequencies of the FS1-A allele within this region could be due to genetic drift and allelic surfing along the expanding population front, or to selection of physiological or behavioral traits.