Population Genomics Reveals Genetic Divergence and Adaptive Differentiation of Chinese Sea Bass (<Emphasis Type="Italic">Lateolabrax maculatus</Emphasis>)

The marine species usually show high dispersal capabilities accompanied by high levels of gene flow. On the other hand, many physical barriers distribute along the continental marginal seas and may prevent dispersals and increase population divergence. These complexities along the continental margin generate serious challenges to population genetic studies of marine species. Chinese sea bass Lateolabrax maculatus distributes broad latitudinal gradient spanning from the tropical to the mid-temperate zones in the continental margin seas of the Northwest Pacific Ocean. Using the double digest restriction-site-associated DNA tag sequencing (ddRAD) approach, we genotyped 10,297 SNPs for 219 Chinese seabass individuals of 12 populations along the Chinese coast in the Northwest Pacific region. Genetic divergence among these populations was evaluated, and population structure was established. The results suggested that geographically distant populations in the Bohai Gulf and the Beibu Gulf retain significant genetic divergence, which are connected by a series of intermediate populations in between. The results also suggested that Leizhou Peninsula, Hainan Island, and Shandong Peninsula are major physical barriers and substantially block gene flow and genetic admixture of L. maculatus. We also investigated the potential genetic basis of local adaptation correlating with population differentiation of L. maculatus. The sea surface temperature is a significantly differentiated environmental factor for the distribution of L. maculatus. The correlation of water temperature and genetic variations in extensively distributed populations was investigated with Bayesian-based approaches. The candidate genes underlying the local selection in geographically divergent populations were identified and annotated, providing clues to understand the potential mechanisms of adaptive evolution. Overall, our genome scale population genetic analysis provided insight into population divergence and local adaptation of Chinese sea bass in the continental marginal seas along Chinese coast.     

Larval development and growth ratios of Odonata of the Azores

To fully understand odonate life cycles, it is vital to analyse the patterns of larval growth, which are tightly associated with variations in environmental factors. However, the identification of larval instars is often difficult, especially for early development stages. We hypothesise that pond hydroperiod influences odonate larval growth, and test this idea with novel information about the environmental characteristics of 12 study ponds in Terceira Island (Azores). This study, which represents the first analysis of larval development of Odonata in the Azores, involved determining the instars of development and growth ratios. We measured the morphological characteristics of 898 Odonata larvae, and found that they significantly differed between temporary and permanent ponds. To estimate the larval instars, we used two methods: frequency distribution methods and correlation diagrams between body characteristics. The first method was the most effective, allowing the estimation of 17 instars for Anax imperator, 13 for Sympetrum fonscolombii and 10 for Ischnura hastata, as well as growth ratios between instars for head width, total length, abdomen length, wings and antenna length. Our results also suggest that a combination of the two methods is the most appropriate strategy for estimating the number of instars and growth ratios during larval development.     

Fitness variation in response to artificial selection for reduced cell area,cell number and wing area in natural populations of <Emphasis Type="Italic">Drosophila melanogaster</Emphasis>

Background

Genetically based body size differences are naturally occurring in populations of Drosophila melanogaster, with bigger flies in the cold. Despite the cosmopolitan nature of body size clines in more than one Drosophila species, the actual selective mechanisms controlling the genetic basis of body size variation are not fully understood. In particular, it is not clear what the selective value of cell size and cell area variation exactly is. In the present work we determined variation in viability, developmental time and larval competitive ability in response to crowding at two temperatures after artificial selection for reduced cell area, cell number and wing area in four different natural populations of D. melanogaster.

Results

No correlated effect of selection on viability or developmental time was observed among all selected populations. An increase in competitive ability in one thermal environment (18°C) under high larval crowding was observed as a correlated response to artificial selection for cell size.

Conclusion

Viability and developmental time are not affected by selection for the cellular component of body size, suggesting that these traits only depend on the contingent genetic makeup of a population. The higher larval competitive ability shown by populations selected for reduced cell area seems to confirm the hypothesis that cell area mediated changes have a relationship with fitness, and might be the preferential way to change body size under specific circumstances.

     

Nutrient availability reduced in older rural impoundments in coastal Bay of Fundy,Canada

The caddisfly species Micropterna lateralis is an abundant representative of limnephilids in intermittent streams. Yet, its basic life history characteristics and adaptations related to environmental factors, such as stream drying, are comparatively understudied. Here, we investigated larval growth and metabolic energy reserves (glycogen, triglycerides) through development in their natural habitat. We concentrated on the larval development because this period represents the important phase of energy accumulation necessary for growth, metamorphosis and embryogenesis. Besides larval physiology, female adults were studied in terms of ovarian maturation. Our results indicate that adult females lack an imaginal diapause, which is otherwise often observed in intermittent stream-inhabiting Limnephilidae. Further, M. lateralis is univoltine and exhibits a relatively fast larval development with five distinct instars, of which four are characterised here (instars II–V). Accrual of biomass occurs in final instars, where a high amount of glycogen is accumulated. Lipid concentrations, on the other hand, are kept constant in final stages and slightly lower than in preceding instars. This dominance of glycogen in final instars found in M. lateralis is highly unusual in insects and of potential adaptive significance for the species’ ability to exploit intermittent habitats.     

Univoltine seasonal cycle and obligate diapause in the noctuid moth <Emphasis Type="Italic">Charanyca trigrammica</Emphasis> Hufn. (Lepidoptera,Noctuidae)

Charanyca trigrammica is a univoltine species over its whole distribution range. To study the diapause-inducing factors, caterpillars were reared at 24°C and day lengths of 12, 13, 14, 15, 16, 17, and 18 h. In all the studied regimes, pupation was not recorded, suggesting an obligate diapause. However, the development was faster under short days. The threshold of this short-day photoperiodic response was ca 17 h. This type of environmental regulation of development may be considered a special feature of diapause occurring in the last larval instars. Hence, the obligate diapause in the last larval instars determines the univoltine cycle of Ch. trigrammica in Belgorod Province of Russia, ensuring successful hibernation of all individuals.     

Effect of Temperature on Development and Reproduction of <Emphasis Type="Italic">Epilachna dodecastigma</Emphasis> (Wied.) (Coleoptera: Coccinellidae)

The effect of five constant temperatures of 21, 24, 27, 30 and 33 °C on adult life span, reproduction, oviposition behavior and larval developmental time of a bitter gourd inhabited coleopteran insect Epilachna dodecastigma (Wied.) (Coccinellidae) was determined in laboratory conditions under 70 ± 5 % relative humidity and a photoperiod of 12 L : 12 D. Larval developmental time of E. dodecastigma decreased as temperature increased from 21 to 33 °C. Life table data revealed that overall mortality was lowest at 27 °C and highest at 21 °C. Females lived longer than males at all temperatures; but longevity decreased with increase in temperature. Pre-oviposition period decreased significantly with increase in temperature up to 27 °C and thereafter increased at a slower rate; whereas oviposition period decreased significantly with increase in temperature. Fecundity and egg viability increased significantly with an increase in temperature up to 27 °C and thereafter decreased at a slower rate. The intrinsic rate of increase (r _m ) was 0.1703, 0.1984, 0.2235, 0.2227 and 0.2181 day^?1 at 21, 24, 27, 30 and 33 °C, respectively. The net reproductive rate and finite rate of increase was highest at 27 °C (R _o  = 112.05; λ = 1.4233) and lowest at 21 °C (R _o  = 51.23; λ = 1.2581).     

The seasonal development cycle of <Emphasis Type="Italic">Aphantopus hyperantus</Emphasis> (L.) (Lepidoptera,Nymphalidae: Satyrinae) in Leningrad Province

The simultaneous influence of the photoperiodic and temperature conditions on pre-diapause and postdiapause larval development of the ringlet Aphantopus hyperantus was studied. At the short day (12 h of light a day) all larvae reached the III instar and entered diapause at all the temperatures tested (18–24°C). At the long day (22 h) the number of diapausing larvae increased with decreasing temperature, and the larvae diapaused at the III and IV instars. The I and II instar larvae (before winter) developed and grew faster under short-day, and the hibernated larvae, under long-day conditions. At the short day the growth rate of the I and II instar larvae did not depend on the temperature, and at the long day it decreased as the temperature increased. After hibernation the growth rate of the IV instar larvae increased with the temperature under long-day conditions, and did not depend on the temperature under short-day ones. Thus, acceleration or deceleration of development, depending on the photoperiodic and temperature conditions, regulated the timing of diapause in the overwintering stage (the III instar larva) and maintained the univoltine seasonal cycle. The males of A. hyperantus developed and grew faster than females while their weight at the larval and pupal stages was smaller. The thermal reaction norms for development (the lower temperature threshold and the coefficient of thermal sensitivity of development) were calculated for the eggs, IV and V instar larvae, and pupae. The coefficient of thermal sensitivity of development for the IV and V instar larvae taken together was lower, and the threshold was higher than the corresponding values for eggs and pupae. The thermal reaction norms for development of the latter stages were the same. The larvae of A. hyperantus retained their sensitivity to the photoperiod after hibernation. Resumption of development after cold reactivation occurred only under long-day conditions, whereas under short-day ones the overwintered larvae entered a repeated diapause. The possibility of photoperiodic reactivation and the absence of spontaneous resumption of development in these larvae were demonstrated.     

Exposure of <Emphasis Type="Italic">Eocanthecona furcellata</Emphasis> (Hemiptera: Pentatomidae) nymphs and adults to high temperatures induces an aestivo-hibernal egg diapause: a strategy for surviving hot summers

The predatory stink bug Eocanthecona furcellata (Wolff) (Hemiptera: Pentatomidae), which is widely distributed in the subtropics and tropics, is a potential biological control agent for lepidopteran, coleopteran, and hemipteran pests. We investigated development of eggs oviposited by E. furcellata females subjected to various photoperiods (i.e., 8L:16D, 12L:12D, and 16L:8D) and temperature regimes (i.e., 26:26, 30:28, 32:30, 34:32, 35:33, and 36:34 °C; temperatures at light and dark phases, respectively) at different developmental stages. Exposure of E. furcellata nymphs and adults to different photoperiods and temperature regimes affected the development of eggs they subsequently oviposited. Temperatures greater than 30 °C induced diapause in a portion of the eggs, as evidenced by the delayed appearance of the black circle and the red spot, characteristics of early and late stage of embryonic development, respectively. The proportion of diapausing eggs generally increased with increasing temperature exposure, whereas it decreased with advancing developmental stage/age at which E. furcellata was subjected to the temperature regime. Although viability of diapausing eggs was lower than that of non-diapausing eggs, diapausing eggs survived longer under high temperatures. The trade-off between survivability and viability may be a strategy to survive unpredictability of summer temperatures.     

Comparative morphology of larvae of coastal crabs (Crustacea: Decapoda: Varunidae)

The larval development of three crabs of the Varunidae family, (Hemigrapsus sanguineus, H. penicillatus, and H. longitarsis), widely spread in Russian waters of the Sea of Japan, were studied under laboratory conditions. At a temperature of 20–22°C and a salinity of 32‰ about 30% of larvae a complete developmental cycle, including five zoeal stages and megalopa, took from 22 to 30 days. All larval stages are illustrated and described in detail. Zoea I and zoea II of the studied crabs are not distinguishable. Zoea III–V of these species differ in the number of dorsomedial setae on the abdominal somite I and in the number of setae on the posterodorsal arch. The megalopae of three Hemigrapsus species possess a different number of segments, aesthetascs and setae on the antennular exopod. In spite of the great similarity of larvae of genera Hemigrapsus and Eriocheir, the latter possesses a number of distinctive features in all developmental stages, supporting the separation of these genera.     

Evolution of increased larval competitive ability in <Emphasis Type="Italic">Drosophila melanogaster</Emphasis> without increased larval feeding rate

Multiple experimental evolution studies on Drosophila melanogaster in the 1980s and 1990s indicated that enhanced competitive ability evolved primarily through increased larval tolerance to nitrogenous wastes and increased larval feeding and foraging rate, at the cost of efficiency of food conversion to biomass, and this became the widely accepted view of how adaptation to larval crowding evolves in fruitflies. We recently showed that populations of D. ananassae and D. n. nasuta subjected to extreme larval crowding evolved greater competitive ability without evolving higher feeding rates, primarily through a combination of reduced larval duration, faster attainment of minimum critical size for pupation, greater efficiency of food conversion to biomass, increased pupation height and, perhaps, greater urea/ammonia tolerance. This was a very different suite of traits than that seen to evolve under similar selection in D. melanogaster and was closer to the expectations from the theory of K-selection. At that time, we suggested two possible reasons for the differences in the phenotypic correlates of greater competitive ability seen in the studies with D. melanogaster and the other two species. First, that D. ananassae and D. n. nasuta had a very different genetic architecture of traits affecting competitive ability compared to the long-term laboratory populations of D. melanogaster used in the earlier studies, either because the populations of the former two species were relatively recently wild-caught, or by virtue of being different species. Second, that the different evolutionary trajectories in D. ananassae and D. n. nasuta versus D. melanogaster were a reflection of differences in the manner in which larval crowding was imposed in the two sets of selection experiments. The D. melanogaster studies used a higher absolute density of eggs per unit volume of food, and a substantially larger total volume of food, than the studies on D. ananassae and D. n. nasuta. Here, we show that long-term laboratory populations of D. melanogaster, descended from some of the populations used in the earlier studies, evolve essentially the same set of traits as the D. ananassae and D. n. nasuta crowding-adapted populations when subjected to a similar larval density at low absolute volumes of food. As in the case of D. ananassae and D. n. nasuta, and in stark contrast to earlier studies with D. melanogaster, these crowding-adapted populations of D. melanogaster did not evolve greater larval feeding rates as a correlate of increased competitive ability. The present results clearly suggest that the suite of phenotypes through which the evolution of greater competitive ability is achieved in fruitflies depends critically not just on larval density per unit volume of food, but also on the total amount of food available in the culture vials. We discuss these results in the context of an hypothesis about how larval density and the height of the food column in culture vials might interact to alter the fitness costs and benefits of increased larval feeding rates, thus resulting in different routes to the evolution of greater competitive ability, depending on the details of exactly how the larval crowding was implemented.     

Dynamics of Estradiol Level during Metamorphosis in the Daubed Shanny (<Emphasis Type="Italic">Leptoclinus maculatus</Emphasis>, Fries, 1838) from Spitsbergen Island

The estradiol content of muscles during metamorphosis in the daubed shanny (Leptoclinus maculatus) from different fjords of Spitsbergen Island, Svalbard, have been studied using mass spectrometry. The level of estradiol at the L4 larval stage of development is significantly lower than at the L2 stage. Values of this parameter in adults are significantly higher than in post-larvae (stage L5). Variations in the estradiol level during metamorphosis can be associated with the growth stimulation and regulation of the process.     

Temperature and photoperiodic control of diapase induction in the ant <Emphasis Type="Italic">Lepisiota semenovi</Emphasis> (Hymenoptera,formicidae) from Turkmenistan

The ants L. semenovi has been found to belong to species with endogenous-heterodynamic seasonal life cycles with the obligate diapause induced predominantly by factors internal for a colony, whereas external ecological factors (photoperiods and temperature) produce merely modifying effects by accelerating or delaying the diapause onset. The photoperiodic and temperature regulation of diapause induction in larvae and queens is shown. Under effect of short days and low temperature the periods of larval pupation and queen oviposition in a colony are shortened markedly, i.e., the diapause of larvae and queens occurs earlier. The daily rhythms of temperature 15/25°C and particularly 20/30°C as compared with constant temperatures 20 and 25°C that correspond to the mean circadian temperatures of the thermorhythm, inhibit manifestations of the short day effects by stimulating the non-diapause development and increasing duration of the seasonal development cycle of ant colonies. The L. semenovi photoperiodic reaction is quantitative, as development and pupation of larvae and egg-laying of queens cease sooner or later under both the short and the long days, but in the latter case significantly later. Thus L. semenovi is one more example among very rare ant species that are revealed to have the photoperiodic regulation of the colony development seasonal cycle.     

The decapod researcher’s guide to the galaxy of sex determination

The objective of this study was to assess the frequency of use of marine resources in recruitment of Southern Hemisphere native riverine fish Galaxias maculatus from rivers across a latitudinal gradient. To do this, we analysed the concentrations of δ³⁴S in vertebral column tissues from fish collected in ten Chilean river systems across latitudes 36°–47°S. The analyses of δ³⁴S signatures in these rivers suggest that the use of marine resources by riverine populations of G. maculatus in large river systems in Chile is variable, with marine resources playing a limited role in more northern large rivers, characterised by warmer temperatures and predictable flow regimes and floodplain inundations. This is in contrast to life histories described for G. maculatus in rivers from New Zealand and Australia, where riverine populations are believed to be characterised by an obligatory recruitment phase in marine environments. Recruitment of G. maculatus in Chilean large rivers appears to depend on their freshwater productivity driven by climate as well as both longitudinal (headwaters lakes-estuary) and lateral (main channel-floodplains) hydrologic connectivities.     

How salinity stress influences the thermal time requirements of seed germination in <Emphasis Type="Italic">Silybum marianum</Emphasis> and <Emphasis Type="Italic">Calendula officinalis</Emphasis>

Salinity is a major problem of many agricultural lands that is usually associated with drought stress in arid and semi-arid regions. In this study we examine the role of salinity stress on temperature requirements of two herbaceous species and how it could be modeled to quantify alterations. We applied four non-linear regression models (segmented, beta, beta modified, and dent-like) to describe the germination rate–temperature relationships of Silybum marinum L. and Calendua officinalis L. over six constant temperatures exposed to different levels of salinity stress. Our results revealed that salinity could affect the cardinal temperatures in both plants and, as a result, it is not possible to suggest one model for all levels of salinity stress. The best model to fit data to predict cardinal temperatures of Silybum marianum and Calendula officinalis at the no-salinity condition were dent-like (AICc?=?4.03) and beta (AICc = ??2.30), respectively. Knowing the thermal time constant (f_o) value helps us predict the minimum number of hours required for completion of germination at the optimal temperature. All models in this study were estimated higher f_o due to higher salinity stress in both Silybum marianum and Calendula officinalis seeds. The highest estimated f_o for Silybum marianum (91.5?±?59.6) and Calendula officinalis (178.9?±?26.5) was obtained from the results of germination rate prediction using a dent-like model at 200 mM salinity.     

Assessing Common Bean Cultivars for Resistance to the Soybean Looper <Emphasis Type="Italic">Chrysodeixis includens</Emphasis> (Lepidoptera: Noctuidae)

The soybean looper Chrysodeixis includens (Walker) (Lepidoptera: Noctuidae) is known as an important pest of leguminous plants worldwide. In Brazil, this pest species is gaining importance to producers of the common bean Phaseolus vulgaris L. (Fabaceae) because it limits field production of the crop. Chemical control is still the primary method of insect control. However, due to the possible harmful effects of pesticides to humans and the environment, alternative and less aggressive practices are being investigated. For this reason, the use of resistant plant genotypes represents a valuable tool in insect control. This study evaluated the biological aspects of larvae of C. includens confined to 14 bean genotypes under laboratory conditions (26 ± 2°C; 65 ± 10% RH; photoperiod of 14 h L:10 h D). The duration of the instars, total duration of the larval phase, consumption while in the larval phase, weight of the fifth instar larvae, larval viability, duration of the pre-pupal and pupal phases, pupal weight, pupal viability, pupal deformity, caterpillar-to-adult cycle, duration of the pre-oviposition and oviposition periods, and total number of viable eggs per female were evaluated. The genotypes “IAC Boreal,” “IAC Harmonia,” and “IAC Formoso” expressed antibiosis, prolonging the caterpillar-to-adult cycle and reducing the larval viability; however, each of these genotypes also experienced high leaf consumption. “IAC Jabola” expressed moderate levels of antibiosis and/or antixenosis (feeding), while the genotype “BRS Horizonte” expressed antixenosis (feeding). The data obtained with IAC Boreal, IAC Harmonia, IAC Formoso, IAC Jabola, and BRS Horizonte are promising and may help with the improvement of programs aimed at managing C. includens damage to this leguminous agricultural crop.     

On distribution and ecology of some species of cleonines (Coleoptera,Curculionidae): IV. Genus <Emphasis Type="Italic">Lixus</Emphasis> F., subgenus <Emphasis Type="Italic">Eulixus</Emphasis> Reitt.

Data on habitats, food plants of larvae and adults, feeding, mating, oviposition, larval and pupal development, natural enemies, and distribution of seven weevil species (Lixus canescens F.-W., L. iridis Ol., L. myagri Ol., L. punctirostris Boh., L. subtilis Boh., L. incanescens Boh., and L. brevipes Bris.) are given. New host plants of L. canescens and L. iridis are revealed. Gall induction by L. brevipes is reported for the first time. Distribution of all the species in Ukraine and Russia (the latter based on the literature) are given in more detail. Information on the known and potential economic importance of every species is provided.     

mtDNA analysis of <Emphasis Type="Italic">Mytilopsis</Emphasis> (Bivalvia,Dreissenidae) invasion in Brazil reveals the existence of two species

The present study sought to identify general patterns of genetic variability and structure of fish stocks (migratory and non-migratory species) along one of the largest Brazilian rivers, the São Francisco. Given that genetic variability of populations of all organisms is governed by both present and past influences, herein we investigate both these aspects by evaluating the current genetic differences between populations of five species (Leporinus piau, Megaleporinus reinhardti, Pimelodus maculatus, Prochilodus argenteus, and Pygocentrus piraya) along the entire extension of the river, as well as their demographic history. Analyses were done through sequences of two mitochondrial fragments and microsatellite data. In general, the data showed no support for recent fragmentation of stocks by the dams present in this river, and that all species show signs of past population expansion. We discuss the possible reasons for the common patterns found between these species, including the influence of the river’s topography and history.     

Dynamics of host plant selection and host-switching by silver-spotted skipper caterpillars

Investigations of host plant selection in herbivorous arthropods have emphasized the importance of oviposition site selection by adults; however, a more complete picture of this process requires additional consideration of the factors influencing host plant choice during the immature feeding stages. We conducted a series of larval choice experiments to examine both the innate and induced preferences of larvae of the Silver-spotted skipper (Epargyreus clarus L.) on three commonly used hosts (Wisteria, Robinia, and Pueraria). Late instar E. clarus larvae reared on each of the three host plants displayed an overall pattern of innate preferences that correlated well with larval performance measures and reflected differences in foliar nutrient concentrations. Larval preferences were also influenced by rearing host species, indicating a role for feeding-induced preferences. When larvae reared on low-quality Wisteria for the first four instars were switched to higher quality Pueraria for the final instar, they developed more quickly and attained significantly higher pupal mass than larvae maintained on Wisteria throughout development. Similarly, larvae switched from Pueraria to Wisteria for the final instar suffered increased development time and produced significantly smaller pupae than those maintained on Pueraria throughout. Thus host-switching, particularly during the more mobile final instars, appears to offer larvae an opportunity to recoup fitness losses associated with early development on a low-quality host. For an equal amount of consumption, larvae feeding on Pueraria gained 50% more mass than those feeding on Wisteria, reflecting measured differences in foliar nitrogen concentration; despite these overall differences in quality, larval growth efficiency was similar among hosts. Especially in the age of common exotic plant introductions, a full understanding of the behavioral component of host selection by herbivorous insects requires appreciation of the dynamic role that immatures can play in host selection and use.     

Host plants influence female oviposition and larval performance in West Indian sweet potato weevils <Emphasis Type="Italic">Euscepes postfasciatus</Emphasis> (Coleoptera: Curculionidae)

Euscepes postfasciatus (Fairmaire) is an invasive pest of the sweet potato (Ipomoea batatas) and is also parasitic to other wild host plants of the Ipomoea genus. The population density of E. postfasciatus is sometimes greater in Ipomoea pes-caprae L. than in Ipomoea indica (Burm. f.). We investigated the desirability of I. pes-caprae as a host plant for E. postfasciatus in terms of reproductive and developmental potential. Females laid fewer eggs on I. pes-caprae, and the eclosion of their larvae was delayed compared with on I. indica. Furthermore, the larval growth rate was slower on I. pes-caprae than on I. indica. These results suggest that I. pes-caprae is not always the preferred host for egg laying and growth rate in the early developmental stages. However, the larval survival rate after the initial period of development was markedly better on I. pes-caprae than on I. indica. The present simulation study demonstrated that the population density of E. postfasciatus on I. pes-caprae overwhelmed that on I. indica over generations. Comparing the two wild host plant species, I. pes-caprae outweighs I. indica with respect to total population growth, but reproduction on I. indica may be advantageous for the colonization of the new habitat.