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Seasonal changes in the abundance of exothermic organisms can be expected with climate change if warmer temperatures can induce changes in their phenology. Given the increased time for ectothermic organism development at lower temperatures, we asked whether population dynamics of the house mosquito, Culex pipiens s.l. (L.) (Diptera: Culicidae), in Jeju-do (South Korea), an island with a gradient of warming temperatures from north to south, showed differences in sensitivity to changes in temperature along the warming gradient. In addition, we asked whether synchrony, that is, the degree of concerted fluctuations in mosquito abundance across locations, was affected by the temperature gradient. We found the association of mosquito abundance with temperature to be delayed by 2 wk in the north when compared with the south. The abundance across all our sampling locations had a flat synchrony profile that could reflect impacts of rainfall and average temperature on the average of all our samples. Finally, our results showed that population synchrony across space can emerge even when abundance is differentially impacted by an exogenous factor across an environmental gradient.
Meta-analysis of 33 studies of developmental timing of Culex pipiens s.l. Linnaeus demonstrates that development rate, or the rate of progression through immature life stadia, is primarily driven by temperature, whereas immature survival is driven by temperature, density, and variability in the environmental conditions. As expected, the linear relationship of temperature and development rate is positive for the larval period as well as development to adult emergence. However, the strength of this association varies significantly. Variation in development rate can be explained using additional environmental factors of intraspecific rearing density, sex, and study methodology. Heterogeneity in development rates even once temperature has been considered emphasizes the need for further research of multiple environmental factors and in changing environments. Immature survival is also significantly impacted by variability in environmental conditions. Development rates vary between subspecies of Cx. pipiens, but these population differences are no longer significant once an environmental factor of temperature is considered. Thus, variability in development rate of these insects appears to be primarily driven by response to certain environmental conditions rather than differences between populations. Broad patterns of phenotypic variation across latitude and 96 yr of empirical estimates were not significant once environmental rearing conditions had been considered.
Native to China, Japan, Korea, and Taiwan, the brown marmorated stink bug, Halyomorpha halys (Sål) (Hemiptera: Pentatomidae) was first detected in the United States in the mid-1990s. Since establishing in the United States, this invasive species has caused significant economic losses in agriculture and created major nuisance problems for home and business owners, especially in the mid-Atlantic region. Basic and applied questions on H. halys have been addressed in its native range in Asia since the mid-1900s and the research outcomes have been published in at least 216 articles from China, Japan, and the Republic of Korea. In Asia, H. halys is described as an occasional or outbreak pest of a number of crops such as apple, pear, persimmon, and soybeans. This species is considered a nuisance pest as well, particularly in Japan. This review summarizes 100 articles primarily translated from Chinese, Japanese, and Korean to English. The content of this review focuses on the biology, ecology, and management of H. halys in Asia, with specific emphasis on nomenclature, life history, host range, damage, economic importance, sampling and monitoring tools, and management strategies. This information from the native range of H. halys provides greater context and understanding of its biology, ecology, and management in North America.
Flight and emergence of the redbay ambrosia beetle, Xyleborus glabratus Eichhoff, were monitored from March 2011 through August 2012 using Lindgren funnel traps baited with manuka oil and emergence traps attached over individual beetle galleries on infested redbay (Persea borbonia (L.) Sprengel) trees. Of the 432 gallery entrances covered with emergence traps, 235 (54.4%) successfully produced at least two adults. Gallery success rates and time until adult emergence were highly variable and strongly depended on time of year galleries were initiated. Successful galleries produced 23.4 ± 2.50 ( ± SE) adult X. glabratus but one had 316 adults emerge from it. Galleries were active for an average of 231.9 ± 6.13 d but five were active for over 1 yr and one gallery produced beetles for 497 d. In total, 5,345 female and 196 males were collected during the study resulting in a sex ratio of ≈27:1 (female:male) emerging from galleries. Ambrosia beetles other than X. glabratus were recovered from 18 galleries or ≈4% of those studied. Beetles that attacked larger diameter trees were more likely to be successful and produce more brood. Lindgren trap captures reflected emergence trap collections but with a delay of about 1 mo between peaks in emergence and capture in traps. Peaks of activity occurred in fall 2011 and spring 2012, but at least some adult beetles were collected using both methods in every month of the year.
In Louisiana during the last decade, the redbanded stink bug, Piezodorus guildinii (Westwood), has become a significant and yield-limiting pest of soybean. The redbanded stink bug was previously reported in the United States in 1892, but was never considered an economically important pest until recently. Soybeans representing four maturity groups (MG) III, IV, V, and VI were sampled weekly from beginning bloom (R1) to physiological maturity (R8) during 2008–2010 at five locations across Louisiana to determine the Pentatomidae composition. In total, 13,146 stink bugs were captured and subsequently identified to species. The predominant species included the redbanded stink bug (54.2%); southern green stink bug (27.1%), Nezara viridula L.; brown stink bug (6.6%), Euschistus servus (Say); and green stink bug (5.5%), Acrosternum hilare (Say). Redbanded stink bug comprised the largest percentage of the complex collected at four of the five survey sites. Numbers exceeding action thresholds of this stink bug complex were only detected during R4 to R7 growth stages. Redbanded stink bug accounted for the largest percentage of the stink bug complex in early maturing soybean varieties (MG III [86%] and IV [60%]) and declined in later maturing soybeans (MG V [54%] and VI [50%]). The redbanded stink bug was initially identified in southern Louisiana during 2000 and had been reported in all soybean producing regions in Louisiana by 2006. This survey is the first to report the redbanded stink bug as a predominant pest of soybeans from locations within the United States.
Fungal entomopathogens are widely distributed across natural and managed systems, with numerous host species and likely a wide range of community impacts. While the potential for fungal pathogens to provide biological control has been explored in some detail, less is known about their community interactions. Here we investigate the effects of fungal epizootics of the entomopathogen Lecanicillium lecanii (Zimmerman) on a keystone mutualism between Azteca instabilis (F. Smith), a dominant arboreal ant, and the green coffee scale (Coccus viridis Green), as well as broader impacts on a coffee agroecosystem ant community. We hypothesized that seasonal epizootics cause shifts in the foraging ranges of A. instabilis as the ants adapt to the loss of the resource. We further hypothesized that the magnitude of these shifts depends on the availability of alternate resources located in neighboring shade trees. To test these hypotheses, we induced an epizootic in experimental sites, which were compared with control sites. Surveys of ant activity were undertaken pre- and postepizootic. We found a decrease in foraging activity of A. instabilis and increase in activity of other ant species in the experimental sites post-epizootic. The decrease in abundance of A. instabilis foragers was greater on plants in which an epizootic was induced than in other plants. This relationship was modified by shade tree density where higher shade tree density was associated with larger decreases in A. intabilis foraging activity in coffee plants. These results demonstrate the potential for fungal entomopathogens to influence the structure and diversity of ecological communities.
Community assembly is driven by multiple factors, including resource availability and habitat requirements. Litter nesting ants respond to food and nest site availability, and adding food and nests may increase ant species richness and abundance. However, litter decomposers share food resources with ants, and increasing food availability may speed decomposition processes, eliminating twigs and seeds in which litter ants nest. We manipulated ant food and nest resources in three habitat types (forest, high-shade coffee, and low-shade coffee) to determine ant community responses after 1 and 2 mo. We examined changes in numbers of ant species, colonies, workers, brood, colony growth rate, and ant species composition. Habitat type strongly affected ant communities, influencing ant species richness, numbers of colonies and workers, and ant species composition. However, food addition and nest addition did not affect these community characteristics. Colony growth rate did not differ with food addition but was greater in forest and low-shade coffee compared with high-shade coffee. Habitat differences in colony growth may be because of presence of an aggressive species (Wasmannia auropunctata Roger) in high-shade coffee plots or naturally low arthropod densities during a time when ant colonization was low. Thus, in coffee landscapes, habitat type impacts litter nesting ant community structure, composition, and colony growth rate; however, food and nest addition had small impacts.
Ten species of parthenogenetic broad-nosed weevils (Coleoptera: Curculionidae: Entiminae) native to Argentina, southern Brazil, and Uruguay were selected for niche modeling analysis based on climatic data and altitude, to evaluate their potential range expansion inside and outside South America. The selected species belong to five genera of the tribe Naupactini affecting economically important crops. Until present, five of the 10 species analyzed here have invaded prairies and steppes of countries outside South America (Australia, New Zealand, Mexico, United States, and South Africa) : Aramigus tessellatus (Say), Atrichonotussordidus (Hustache), Atrichonotus taeniatulus (Berg), Naupactus leucoloma Boheman, and Naupactus peregrinus (Buchanan). Our niche modeling analyses performed with MAXENT demonstrated that these areas would be also suitable for Aramigus conirostris (Hustache), Eurymetopus fallax (Boheman), Pantomorus auripes Hustache, Pantomorus ruizi (Brèthes), and Pantomorus viridisquamosus (Boheman), consequently, they also have the potential to invade areas outside their native ranges, mainly in southeastern United States, some European countries (e.g., Portugal, France, and southern England), South Africa, New Zealand, and southeastern Australia. All the studied species share similar environmental requirements, the most important variables being the Mean Temperature of Driest Quarter, the Annual Mean Temperature and Isothermality. Long distance dispersal through commercial trade, and parthenogenetic reproduction would increase the threat of these weevils to crop production worldwide.
Research on hedgerow design for supporting communities of natural enemies for biological control lags behind farmer innovation in California, where assemblages of perennial plant species have been used on crop field margins in the last decade. We compared natural enemy to pest ratios between fields with hedgerows and fields with weedy margins by sampling beneficial insects and key pests of vegetables on sticky cards. We used biweekly vacuum samples to measure the distribution of key insect taxa among native perennial plant species with respect to the timing and intensity of bloom. Sticky cards indicated a trend that field margins with hedgerows support a higher ratio of natural enemies to pests compared with weedy borders. Hedgerow plant species hosted different relative densities of a generally overlapping insect community, and the timing and intensity of bloom only explained a small proportion of the variation in insect abundance at plant species and among hedgerows, with the exception of Orius spp. on Achillea millefolium L. and Baccharis pilularis De Candolle. Indicator Species Analysis showed an affinity of parasitic wasps, especially in the super-family Chalcidoidea, for B. pilularis whether or not it was in flower. A. millefolium was attractive to predatory and herbivorous homopterans; Heteromeles arbutifolia (Lindley) Roemer and B. pilularis to Diabrotica undecimpunctata undecimpunctata Mannerheim; and Rhamnus califomica Eschsch to Hemerobiidae. Perennial hedgerows can be designed through species selection to support particular beneficial insect taxa, but plant resources beyond floral availability may be critical in providing structural refuges, alternative prey, and other attractive qualities that are often overlooked.
Actinomycetes—a group of antimicrobial producing bacteria- have been successfully cultured and characterized from the nest material of diverse arthropods. Some are symbionts that produce antimicrobial chemicals found to protect nest brood and resources from pathogenic microbes. Others have no known fitness relationship with their associated insects, but have been found to produce antimicrobials in vitro. Consequently, insect nest material is being investigated as a new source of novel antimicrobial producing actinomycetes, which could be harnessed for therapeutic potential. To extend studies of actinomycete-insect associations beyond soil-substrate dwelling insects and wood boring excavators, we conducted a preliminary assessment of the actinomycetes within the nests of the paper wasp, Polistes dominulus (Christ). We found that actinomycetes were readily cultured from nest material across multiple invasive P. dominulus populations-including members of the genera Streptomyces, Micromonospora, and Actinoplanes. Thirty of these isolates were assayed for antimicrobial activity against the challenge bacteria Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus, Serratia marcescens, and Bacillus subtilis. Sixty percent of isolates inhibited the growth of at least one challenge strain. This study provides the first assessment of bacteria associated with nests of P. dominulus, and the first record of antimicrobial producing actinomycetes isolated from social wasps. We provide a new system to explore nest associated actinomycetes from a ubiquitous and cosmopolitan group of insects.
Mealybug, Phenacoccus solenopsis Tinsley, is a sap-sucking hemipteran insect. It is an agricultural pest that is now widely distributed in India. In this study we report the presence of Rickettsia from P. solenopsis. We constructed a 16S rRNA gene library to study the bacterial diversity associated with this insect and we found that all the clones from the library were only of Candidatus Tremblaya phenacola. This study also highlights that the normal protocol adopted to study the bacterial diversity from environmental sample, by preparation of a 16S rRNA gene library, does not work when the bacterial population is highly skewed in favor of one bacteria (primary endosymbiont in this case). Hence, we used bacterial genus specific polymerase chain reaction primers to test the presence of any of the widely known secondary endosymbionts associated with insects. We tested for the presence of Cardinium, Rickettsia, Wolbachia, and Arsenophonus in P. solenopsis collected from 10 different locations across India. Only Rickettsia was detected from four locations while we were not able to find any other bacteria. We confirmed the presence of these bacteria by localizing Rickettsia and the primary endosmbiont, Candidatus Tremblaya sp. to the bacteriocyte of P. solenopsis using fluorescent in situ hybridization.
Endoparasitoid larvae may eliminate heterospecific competitors by physical or physiological means. The outcomes of these intrinsic competitions are often predictable with one species typically eliminating the other. The opiine braconids Doryctobracon areolatus (Szepligeti) and Utetes anastrephae (Viereck) are among the most common native parasitoids of frugivorous Tephritidae in the Neotropics and subtropics. U. anastrephae is typically the victor in intrinsic interactions with D. areolatus, but the later has a longer ovipositor and may find a competitor-free-space in larger fruit whose hosts are beyond the reach of U. anastrephae. An Asian opiine species, Diachasmimorpha longicaudata (Ashmead) has been introduced throughout much of the Americas. Its ovipositor is longer than that of D. areolatus and if it is a superior intrinsic competitor it should be able to cause local extinctions of D. areolatus. The outcomes of sequential ovipositions by D. longicaudata and D. areolatus and U. anastrephae found that D. longicaudata significantly suppresses development of D. areolatus. However, competitions between D. longicaudata and U. anastrephae were more equal. The denial of competitor free space may account for the gradual replacement of D. areolatus by D. longicaudata in Florida where both species were introduced ≈40 yr ago. Diachasmimorpha longicaudata and D. areolatus continue to coexist in Mexico and this could be because of greater abiotic and biotic environmental complexity that allows for separate niches. Establishment or augmentative releases of D. longicaudata could result in elimination of native parasitoids and this should be considered before its introduction.
The apiflora of 34 forest and meadow plant communities in Tara National Park was studied with the aim of assessing their melliferous potential and their contribution to bee pasture during the vegetation period. The melliferous plants were analyzed individually from the aspect of their flowering phenology, abundance, and the intensity of nectar and pollen production, as well as the production of honeydew. The melliferous potential of each investigated plant community was theoretically assessed on the basis of the coenotic coefficient of melliferousness incorporating a phytocoenotic analysis, the coenotic coefficients of nectar and pollen production, and the percentage of melliferous species in relation to the total number of species that characterize the association. The highest percentage of the melliferous species was noted in the meadow association Petasitetum hybridi (70%) and the forest association Piceetum-Abietis serpentinicum (63.6%). The highest values of the coenotic coefficient of melliferousness were established for the forest association Querco-Carpinetum iliricum, and the meadow association Rhinantho-Cynosuretum cristati. Trees notable for their honeydew production in good quantities were Pinus nigra Arnold, Picea sp. Fagus sylvatica Linnaeus, Populus tremula Linnaeus, and Quercus cerris Linnaeus. Because, the vegetation in the study area is forest dominated, forest bee pasture including early flowering herbaceous and woody plants, is of the greatest significance for the honey bee, both in the early spring because of pollen and nectar production, and in the autumn as a source of honeydew.
Geographic populations of a widespread species can differ in their ability to adapt to a novel environment because they possess different amounts of the requisite genetic variation. We compared responses to the same novel host in ecologically and genetically divergent populations of the seed beetle Cattosobruchus maculatus (F.). Populations from Africa and Asia had been derived from and maintained on different legume hosts. In preselection assays, both populations exhibited lower survival, slower development, and smaller size on a third host (adzuki bean), and the difference in performance between the ancestral and novel hosts was especially high for the African population. Replicate lines of each population were switched to adzuki bean or maintained on the ancestral host, and beetle performance was measured on both hosts after 12 generations. Survival on adzuki bean increased substantially in the adzuki-bean lines of the African population, but improved only slightly in the Asian lines. Similarly, only the African adzuki-bean lines exhibited significantly faster development on adzuki bean. Improved performance on adzuki bean did not simultaneously reduce performance on the ancestral host. Together with previous studies, these results confirm that populations of C. maculatus often possess sufficient standing genetic variation for rapid adaptation to a novel host, but the magnitude of the response may depend on the source population. Although international trade in grain legumes can expand beetle host ranges and produce unusual biotypes, the consistent absence of strong genetic trade-offs in larval performance or adult oviposition across hosts makes it unlikely that this insect would form distinct host races.
The redbay ambrosia beetle (Xyleborus glabratus Eichhoff) is an invasive pest and vector of the pathogen that causes laurel wilt disease in Lauraceous tree species in the eastern United States. This insect uses olfactory cues during host finding, but use of visual cues by X. glabratus has not been previously investigated and may help explain diameter-related patterns in host tree mortality. The objective of this study was to determine whether X. glabratus females visually detect silhouettes of tree stems during host finding and are more likely to land on large diameter stems than smaller ones. Three field experiments were conducted in which stem silhouettes (black cylinders or standing nonhost pines) of varying diameters and identical capture surface areas were baited with essential oil lures. The Log10-transformed number of X. glabratus trapped per week increased as a function of silhouette diameter in 2011 and 2012, using artificial silhouette diameters ranging 2–18 and 3–41 cm, respectively. When lures and capture surfaces were attached to standing pines ranging 4–37 cm in diameter, a positive relationship between Log10(X. glabratus trap catch) and stem diameter was modeled using nonlinear quadratic plateau regression and indicated a diameter above which visual attraction was not enhanced; however, there was not a maximum diameter for enhanced X. glabratus attraction that was generally consistent across all experiments. These results 1) indicate that X. glabratus incorporates visual information during host finding, 2) help explain diameter-related patterns of redbay (Persea borbonia (L.) Sprengel) mortality observed during laurel wilt epidemics, and 3) are applicable to the management of this forest pest.
Attraction of wild male fall armyworm, Spodoptera frugiperda (J. E. Smith), was compared in trapping experiments during 2005–2009 in Florida. Traps were baited either with a commercial sex pheromone lure or corn and rice strain females obtained from laboratory colonies. Over 6,900 male moths were collected, and a large subset (>1,500) of these moths was analyzed for their host strain identity. The pheromone lure attracted over four times more males than virgin corn or rice strain females. Almost 60% of males attracted to the pheromone lure were identified as corn strain. However, both corn and rice strain females attracted a higher percentage of rice strain males, providing evidence that the commercial lure used in our study is biased to attract corn strain males and underestimates rice strain population numbers relative to corn strain numbers. Corn and rice strain males were attracted more to corn strain females than rice strain females, although there was variation in response according to location and season. Our results suggest that attraction of males to corresponding-strain females does not appear to be a premating mechanism that results in assortative mating between corn and rice host strains. Clearly other premating or perhaps even postmating mechanisms are important for the maintenance of host strains in S. frugiperda.
The choice of killing solutions for pitfall traps can influence sampling and is highly dependent on the objectives of each study. It is becoming increasingly common, however, and is more environmentally friendly, to use the same organisms to extract information for different kinds of studies. The killing solution should, therefore, be able to sample local active organisms, as well as maintain the integrity of their organs, tissues, and macromolecules. In a previous work, we showed that using ethanol fuel as a killing solution maintains the integrity of the specimens and enhances the Orthoptera richness and abundance of samples. In the current study, we evaluated two explanations for this pattern. We set up a field experiment to test whether ethanol fuel is attractive for orthopterans, and we investigated in the laboratory whether individuals of Gryllus sp. sink or die faster in ethanol fuel than in other killing solutions. Our results allowed us to refute the hypotheses of attraction caused by ethanol fuel and showed that the higher sampling efficiency of ethanol fuel is directly linked to the specimens sinking and dying faster than in other killing solutions. Thus, in addition to taxonomic, anatomical, and molecular studies, we recommend ethanol fuel for sampling organisms active in the litter in ecological studies.
A variety of traps have been developed for monitoring introduced populations of Pseudacteon spp. phorid flies (Diptera: Phoridae) across their established range in the United States. Such traps typically exploit common aspects of phorid fly biology and behavior, such as their attraction to live or dead red imported fire ants, Solenopsis invicta Buren (Hymenoptera: Formicidae), as well as the perching behavior of these parasitoids. However, populations of multiple species of phorid flies have been established in the United States to serve as biological control agents against S. invicta, and it is unclear if all trap designs are equally effective in sampling this variety of phorid species. This study investigated the effectiveness of six trap designs simultaneously during three sampling events in south- central Texas. Interactions between two species of phorid flies (Pseudacteon tricuspis Borgmeier and P. curvatus B.) and their hosts have been intensively studied at this location for over eight years. When analyzed independently, there were no significant differences in the mean number of P. curvatus or P. tricuspis phorid s collected by any of the trap designs during any of the sampling events. However, when the total number of phorids collected were combined, significant trap performance differentials were observed during the October 2010 sampling event. Furthermore, there were significant differences among male flies during the September 2012 observation. Additionally, a trap component cost comparison is provided. The consistent and relatively equivalent performance of the phorid traps investigated in these trials suggests that all are appropriate for phorid surveillance, and cost and ease-of-use considerations may be the most important criteria when selecting a trap design.
Alfalfa (Medicago sativa L.) is a highly attractive plant host to Lygus spp. and is used as a trap crop in California organic strawberries to influence the dispersion and dispersal of these pests, particularly Lygus hesperus Knight. The abundance and distribution of Lygus spp. nymphs between two trap crops separated by 50 strawberry rows was analyzed in 2008 and 2010. Nymphs demonstrated a bimodal distribution in strawberries between trap crops, where nymphs were most abundant and aggregated in alfalfa, when compared with interior strawberry rows, where nymphs were less abundant. The majority of nymphs were concentrated in trap crops and nymphal densities in interior strawberry rows were well below economic thresholds. The movement of Lygus spp. from a marked alfalfa trap crop into adjacent strawberry rows or trap crops was also studied in 2008 and 2009 using a chicken egg albumin enzyme-linked immunosorbent assay mark-capture technique. The majority of marked-captured L. hesperus adults and Lygus spp. nymphs remained in alfalfa trap crops, rather than dispersing out into strawberry rows at 24 h, 48 h, and 2 wk, postprotein application. The attenuation of Lygus spp. movement in alfalfa associated with organic strawberries is a key component of successful trap cropping. A small percentage of marked adults and nymphs were captured in neighboring alfalfa trap crops, located 62 m from the point of protein application, highlighting the dispersal capacity of this key pest.
In-nest observations of the solitary bee, Megachile rotundata (F.), revealed that nesting females apply olfactory cues to nests for nest recognition. On their way in and out of the nest, females drag the abdomen along the entire length of the nest, and sometimes deposit fluid droplets from the tip of the abdomen. The removal of bee-marked sections of the nest resulted in hesitation and searching behavior by females, indicating the loss of olfactory cues used for nest recognition. Chemical analysis of female cuticles and the deposits inside marked nesting tubes revealed the presence of hydrocarbons, wax esters, fatty aldehydes, and fatty alcohol acetate esters. Chemical compositions were similar across tube samples, but proportionally different from cuticular extracts. These findings reveal the importance of lipids as chemical signals for nest recognition and suggest that the nest-marking cues are derived from a source in addition to, or other than, the female cuticle.
Herbivore host specialization includes changes in behavior, driven by locally induced adaptations to specific plants. These adaptations often result in sexual isolation that can be gauged through detection of reduced gene flow between host associated populations. Hypothetically, reduced gene flow can be mediated both by differential response to specific plant kairomones and by the influence of larval diet on some adult traits such as pheromone composition. These hypotheses could serve as a model to explain rapid radiation of phytophagous tephritid fruit flies, a group that includes several complexes of cryptic species. The South American Fruit Fly Anastrepha fraterculus (Wiedemann) is a complex of at least seven cryptic species among which pheromone mediated sexual isolation resulted in rapid differentiation. Cryptic species also exhibit differences in host affiliation. In search of a model explaining rapid radiation in this group, we studied host plant chemical composition and genetic structure of three host associated sympatric populations of A. fraterculus. Chemical composition among host plant fruit varied widely both for nutrient and potentially toxic secondary metabolite content. Adaptation to plant chemistry appears to have produced population differentiation. We found host mediated differentiation to be stronger between populations exploiting sympatric synchronic hosts differing in chemical composition, than between populations that exploit hosts that fruit in succession. Gene flow among such host associated populations was extremely low. We propose as a working hypothesis for future research, that for those differences to persist over time, isolating mechanisms such as male produced sex pheromones and female preferences resulting from adaptation to different larval diets should evolve.
Eggs of Anagasta kuehniella (Zeller) are widely used in mass rearing of parasitoids, especially Trichogramma spp. and predators in many biological-control programs. The objective of this study was to improve the efficiency of mass rearing of A. kuehniella through determining the optimal temperature conditions for rearing, by assessing the effect of temperature during the developmental stages on the reproduction of A. kuehniella. We evaluated 1) the effect of temperature at which A. kuehniella was kept from egg to adult death, on reproduction; 2) the effect of temperature during the larval and pupal stages on oviposition; and 3) the effect of different temperatures on adults that originated from larvae kept in a constant temperature of 25°C. The results indicated that the optimal temperature range for the development of A. kuehniella is between 20–30°C, as at 30°C there was a marked decrease in viability of the egg and larval stages. The best temperature for maintaining A. kuehniella from egg to adult death is 25°C. Temperatures of 30 and 32°C lead to deformations in genitalia of males, reducing the viability of eggs, and also eggs and females from these temperatures have lower weights. The rearing temperature of immatures affects the egg-laying capacity of adults and the egg viability. The oviposition capacity of adults kept in different temperatures ranging from 18 to 32°C, after being reared in constant temperature (25°C) during the larval stages, was not affected.
We characterized the cold tolerance of natural populations of the Eastern subterranean termite (Reticulitermes flavipes (Kollar) [Isoptera, Rhinotermitidae]) in southwestern Ontario, Canada. We measured cold tolerance in workers from six colonies of termites established from Pelee Island in Lake Erie, and Point Pelee National Park. The mean critical thermal minimum, at which termites entered chill coma, ranged from 8.1 to 5.7°C. Mean supercooling points (SCP, the temperature at which individuals freeze) ranged from -4 to -4.6°C, and did not differ significantly between colonies, nor was SCP dependent on body size. Individuals survived brief exposure to low temperatures, as long as they did not freeze, but internal ice formation was always lethal, suggesting a freeze avoiding strategy. The LT50 (temperature at which 50% of individuals were killed by a 1 h exposure) was -5.1°C, but all individuals could survive -2°C for at least 72 h. Low temperature acclimation (12°C, 7 d) or hardening (4°C, 2 h) had no impact on the SCP, but acclimation did slightly increase the critical thermal minimum, making the termites less cold tolerant. We conclude that R. flavipes is not particularly cold tolerant, and likely relies on burrowing deep into the soil to avoid exposure to temperature to extremes.
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.
Selection of test species for use in biosafety evaluation of genetically modified plants is challenging but important, as regulators in many jurisdictions require tests to determine the potential for adverse environmental impacts before the release of plants into the environment. This contribution provides an example of an evidence-based process whereby species from the receiving environment can be ranked in order of susceptibility to potential impact, and guide test species selection. The case study used for this example was ryegrass, a forage plant, which had been modified to produce elevated levels of the lipid triacylglyceride. The previously described priority ranking of nontarget invertebrates model (PRONTI), designed to rank invertebrates for biosafety testing, has been adapted for use with these plants, which could, potentially, be beneficial to invertebrate populations, and applied to data on 246 known pasture invertebrate species. The output from the model for the top 20 ranked pasture invertebrate species is discussed, the attributes of these are considered along with the level of uncertainty in the information used. Consideration is given to how the model output can be interpreted and used in a biosafety risk assessment. While some subjectivity is involved in establishing the scores, all invertebrate species are subjected to the same analysis, and treated equally. In this way, regulators have a method of a risk assessment that is evidence-based, and transparent in its assumptions thereby avoiding potential for bias.
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