Effects of temperature and dietary nitrogen on genetic variation and covariation in gypsy moth larval performance traits

To assess the plastic and genetic components of variation in responses of gypsy moth (Lymantria dispar) 4th instar larvae to temperature and food quality, we applied a split-family four-environment experimental design where full-sibs were reared on two constant temperatures (23°C and 28°C) and two concentrations of dietary nitrogen (1.5 and 3.7% dry weight). A temperature of 28°C and low dietary nitrogen decreased larval weight and prolonged larval developmental time, while viability was not affected. Only a marginally significant interaction between the two environmental factors was found for larval weight. The broad-sense heritability for larval developmental time did not change across environments, and across-environment genetic correlations were close to one. Heritability for larval weight depended on environmental and across-environmental genetic correlations that were not significant. There was no evidence of a trade-off between developmental time and larval weight. The implications of the obtained results for the evolution of phenotypic plasticity in complex environments are discussed.Projekat ministarstva br. 17302

Effect of temperature and food quality on variability of fitness components and physiology of digestion in the gypsy moth larvae Lymantria dispar L.

Temperatura i kvalitet hrane utiču na performansu larvi gubara, Lymantria dispar L. nezavisno ili u međusobnoj interakciji. Strategije preživljavanja larvi gubara u temperaturno kao i nutritivno heterogenoj sredini obuhvataju različite tipove reverzibilne i ireverzibilne fenotipske plastičnosti, koje preko uticaja na usvajanje i raspodelu resursa utiču na osobine životne istorije i rezistentnost prema ekstremnim uslovima životne sredine. U cilju ispitivanja efekata temperature i kvaliteta hrane, tj. sadržaja proteina i ugljenih hidrata u hrani na komponente adaptivne vrednosti, kao i ekspresiju genetičke varijabilnosti, larve gubara su izložene delovanju tri različite temperature (suboptimalna, optimalna i supraoptimalna) i 4 kombinacije hranljivog sastava dijete, koje su se međusobno razlikovale kako u ukupnom sadržaju proteina i ugljenih hidrata, tako i u njihovom međusobnom odnosu. U istim eksperimentalnim uslovima ispitivana je uloga procesa varenja, odnosno aktivnosti digestivnih enzima u usklađivanju odnosa i količine unetih nutienata sa potrebama organizma na različitim temperaturama. Takođe, ispitan je uticaj nutritivne vrednosti i balansiranosti hrane na senzitivnost gubara prema stresnim temperaturama. Nepovoljne temperature i nizak sadržaj proteina u hrani, kao i disbalans proteina u odnosu na ugljene hidrate, smanjuju performansu larvi gubara. Uticaji temperature i kvaliteta hrane na komponente adaptivne vrednosti: preživljavanje, trajanje razvića, masu i relativnu brzinu rasta, uglavnom su međusobno nezavisni. Pokazano je da povišena temperatura smanjuje preživljavanje i trajanje razvića larvi ali dovodi do povećanja relativne brzine rasta. Nutritivni sastav hrane nije uticao na preživljavanje, ali je nizak sadržaj proteina u hrani dovodio do produžavanja razvića, smanjenja mase i relativne brzine rasta larvi. Relativna brzina rasta larvi je bila manja i pri visokom sadržaju ugljenih hidrata u hrani, dok je smanjenje mase larvi na hrani sa niskim sadržajem proteina bilo veće ako je i sadržaj ugljenih hidrata bio nizak...Temperature and food quality affect the performance of gypsy moth larvae Lymantria dispar L. independently or in an interaction with each other. Survival strategies of gypsy moth larvae in temperature and nutritionally heterogeneous environments include various types of reversible and irreversible phenotypic plasticity, which due to the effect of uptake and distribution of resources affect the life-history traits and resistance to extreme environmental conditions. In order to investigate the direct and interactive effects of temperature and food quality on fitness components, as well as the expression of genetic variation, gypsy moth larvae were exposed to three different temperatures (suboptimal, optimal and supraoptimal) and 4 sets of nutrient composition of the diet, which differed in protein and carbohydrate content. Under the same experimental conditions, the role of digestion and digestive enzyme activity in adjusting nutrient quantity and ratio with organism needs at different temperatures was investigated. Also, it was investigated the effect of nutritional value of the food on sensitivity of gypsy moth larvae to stressful temperatures. An adverse temperature and low protein content in food, as well as an imbalance of protein compared to carbohydrates, reduced performance of gypsy moth larvae. Effects of temperature and food quality on fitness components - survival, developmental time, larval weight and relative growth rate were mainly independent. It has been shown that elevated temperature reduces survival and duration of development, but leads to an increase of the relative growth rate. Nutritional composition of food had no effect on survival, but the low protein content led to prolonged developmental time, reduced larval weight and relative growth rate of gypsy moth larvae. The relative growth rate of larvae was lower if carbohydrate content in food was high, while larval weight reduction was greater if protein content was low and the carbohydrate content was high..

Genetic variation and correlations of life-history traits in gypsy moths (Lymantria dispar L.) from two populations in Serbia

Periodic fluctuations in density impose different selection pressures on populations of outbreaking Lepidoptera due to changes in their nutritional environment. The maternal effects hypothesis of insect outbreak predicts the transmission of this nutritional "information" to subsequent generations and alterations in offspring life-history traits. To test for these time-delayed effects of the parental generation, we compared life-history traits and their variation and covariation among laboratory-reared gypsy moths hatched from egg masses collected from low- and medium-density populations. Decreased individual performance was recorded in offspring from the medium-density population, indicating reduced egg provisioning under crowding conditions. Genetic variance and covariance were also shown to be sensitive to density of the parental generation. In gypsy moths from the medium-density population, quantitative genetic analysis revealed significantly higher broad-sense heritabilities for development duration traits and demonstrated a trade-off between development duration and body size

Effects of temperature and dietary nitrogen on genetic variation and covariation in gypsy moth larval performance traits

To assess the plastic and genetic components of variation in responses of gypsy moth (Lymantria dispar) 4th instar larvae to temperature and food quality, we applied a split-family four-environment experimental design where full-sibs were reared on two constant temperatures (23°C and 28°C) and two concentrations of dietary nitrogen (1.5 and 3.7% dry weight). A temperature of 28°C and low dietary nitrogen decreased larval weight and prolonged larval developmental time, while viability was not affected. Only a marginally significant interaction between the two environmental factors was found for larval weight. The broad-sense heritability for larval developmental time did not change across environments, and across-environment genetic correlations were close to one. Heritability for larval weight depended on environmental and across-environmental genetic correlations that were not significant. There was no evidence of a trade-off between developmental time and larval weight. The implications of the obtained results for the evolution of phenotypic plasticity in complex environments are discussed.Projekat ministarstva br. 17302

The effects of cadmium on the life history traits of Lymantria dispar L.

Gypsy moth (Lymantria dispar L.) females and males were chronically exposed to three sublethal cadmium concentrations (10, 30 and 50 mg/g dry food mass) in order to assess the effects of cadmium on larval and pupal duration, pupal mass and longevity. On average, the presence of cadmium in food did not affect larval duration while shortened pupal duration and reduced pupal mass and longevity were recorded. The most significant effects were obtained at the highest cadmium concentration. Females and males did not differ in sensitivity of life history traits to cadmium exposure. It is concluded that (1) cadmium exerts a strong adverse impact on the growth and development of gypsy moths, and (2) the significance of the cadmium effects depends on the dose.Projekat ministarstva br. 14303

Biogenic amines in protocerebral A2 neurosecretory neurons of Lymantria dispar L. (Lepidoptera:Lymantriidae): Response to trophic stress

The number, morphometric parameters and amount of aminergic neurosecretory product of protocerebral A2 neurosecretory neurons were investigated in the fifth instar of Lymantria dispar caterpillars, following a suitable or unsuitable trophic regime. Caterpillars originated from two populations (Quercus rubra or Robinia pseudoacacia forest) and were differently adapted to trophic stress, i.e. feeding on locust tree leaves - unsuitable host plant. The number of neurosecretory neurons was higher in the caterpillars originated from Robinia population than in Quercus population, regardless of feeding. A2 neurosecretory neurons, nuclei and their nucleoli were larger in caterpillars fed with unsuitable leaves in both populations. There was more aminergic product in the A2 neurosecretory neurons of the caterpillars fed with unsuitable leaves independently of population origin

Biogenic amines in protocerebral A2 neurosecretory neurons of Lymantria dispar L. (Lepidoptera:Lymantriidae): Response to trophic stress

The number, morphometric parameters and amount of aminergic neurosecretory product of protocerebral A2 neurosecretory neurons were investigated in the fifth instar of Lymantria dispar caterpillars, following a suitable or unsuitable trophic regime. Caterpillars originated from two populations (Quercus rubra or Robinia pseudoacacia forest) and were differently adapted to trophic stress, i.e. feeding on locust tree leaves - unsuitable host plant. The number of neurosecretory neurons was higher in the caterpillars originated from Robinia population than in Quercus population, regardless of feeding. A2 neurosecretory neurons, nuclei and their nucleoli were larger in caterpillars fed with unsuitable leaves in both populations. There was more aminergic product in the A2 neurosecretory neurons of the caterpillars fed with unsuitable leaves independently of population origin.Projekat ministarstva br. 17302

Trypsin activity in the midgut of gypsy moth (Lymantria dispar L.)larvae during the intermolt period

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Host-associated divergence in the activity of digestive enzymes in two populations of the gypsy moth Lymantria dispar (Lepidoptera: Erebidae)

The gypsy moth is a generalist insect pest with an extremely wide host range. Adaptive responses of digestive enzymes are important for the successful utilization of plant hosts that differ in the contents and ratios of constituent nutrients and allelochemicals. In the present study, we examined the responses of α-amylase, trypsin, and leucine aminopeptidase to two tree hosts (suitable oak, Quercus cerris, and unsuitable locust tree, Robinia pseudoacacia) in the fourth, fifth, and sixth instars of gypsy moth larvae originating from oak and locust tree forest populations (hereafter assigned as Quercus and Robinia populations, respectively). Gypsy moths from the Robinia forest had been adapting to this unsuitable host for more than 40 generations. To test for population-level host plant specialization, we applied a two-population × two-host experimental design. We compared the levels, developmental patterns, and plasticities of the activities of enzymes. The locust tree diet increased enzyme activity in the fourth instar and reduced activity in advanced instars of the Quercus larvae in comparison to the oak diet. These larvae also exhibited opposite developmental trajectories on the two hosts, i.e. activity increased on the oak diet and decreased on the locust tree diet with the progress of instar. Larvae of the Robinia population were characterized by reduced plasticity of enzyme activity and its developmental trajectories. In addition, elevated trypsin activity in response to an unsuitable host was observed in all instar larvae of the Robinia population, which demonstrated that Robinia larvae had an improved digestive performance than did Quercus larvae

Morphometric changes of corpora allata in Morimus funereus müls. (Cerambycidae) larvae during thermal stress

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