Female sex pheromone components of Helicoverpa gelotopoeon: first heliothine pheromone without (Z)-11-hexadecenal

Helicoverpa gelotopoeon Dyar is a very important pest of economic importance on cotton in Argentina. Analysis of female pheromone gland extracts prepared from 1‐ to 2‐day‐old virgin female moths demonstrated the presence of a 1 : 0.84 blend of hexadecanal (16:Ald) and (Z)‐9‐hexadecenal (Z9‐16:Ald), with trace quantities of tetradecanal in some samples, 2.4% of 16:Ald. The average quantity of Z9‐16:Ald extracted per female was estimated to be 33 ng, with a range of 18.9–46.4 ng per female when collected 2–3 h into the scotophase. In field trials conducted in both cotton and tomato crops in Santiago del Estero, Argentina 1 : 1 blends of 16:Ald and Z9‐16:Ald caught significantly more male H. gelotopoeon than Z9‐16:Ald alone, although there was no significant difference between blends containing between a 0.2 : 1 and 2 : 1 ratio of 16:Ald and Z9‐16:Ald. There was no analytical evidence for the presence of (Z)‐11‐hexadecenal (Z11‐16:Ald) in pheromone gland extracts, although this compound has been identified in all female sex pheromones of Heliothinae to date. In field trials, the addition of Z11‐16:Ald at the 1% level to either a 1 : 1 blend of 16:Ald and Z9‐16:Ald or Z9‐16:Ald alone significantly reduced the catch of male H. gelotopoeon. Sympatric Heliothis virescens were not caught in any of the blends tested for H. gelotopoeon, but were caught in low numbers in traps baited with a 4 : 100 blend of (Z)‐9‐tetradecenal and (Z)‐11‐hexadecenal.     

The mango seed weevil Sternochetus mangiferae (Fabricius) (Coleoptera: Curculionidae) is characterized by low genetic diversity and lack of genetic structure

1. The mango seed weevil Sternochetus mangiferae (Fabricius) is distributed across the major mango-producing areas of the world and causes significant economic losses of mango fruit. Despite its importance as a crop pest, we have only limited information on the population genetics of the mango seed weevil.
2. Here, we examined the genetic diversity of this important pest using specimens intercepted by Beijing Customs District P. R. in China from 41 countries and regions. We used segments of the mitochondrial gene cytochrome c oxidase subunit I and the nuclear gene elongation factor 1-alpha to examine population genetic structure in this species.
3. Our results showed that genetic diversity is low in S. mangiferae, with a mean genetic distance of 0.095–0.14%. Other population genetic parameters also indicated a low level of genetic diversity among samples from a large geographic range. Analysis of molecular variance revealed little population genetic structure, and mismatch distribution analyses provided evidence of a population expansion, although other demographic metrics of population expansion were nonsignificant.
4. We suggest that the observed low level of genetic diversity and population genetic structure in S. mangiferae supports the hypothesis that the population genetics of this species has been impacted by anthropogenic transportation of mangoes and weevils.

     

Phenotypic variability in the Old World bollworm,Helicoverpa armigera (Hübner) populations in India

Helicoverpa armigera (Hübner) is one of the most prominent polyphagous species of the Heliothinae pest complex that inflicts severe damage to a wide range of crops in India. Knowledge regarding the population structure of the pest species, whether morphological or genetic, is considered as an essential tool in making effective management decisions. Thus here, we performed the phenotypic characterization of H. armigera populations collected from varied geographic locations across India. Studied populations differed significantly for several external morphometric traits studied at larval, pupal and adult stages. Significant differences were also observed with respect to the intensity of black pigmentation on larval body as well as adult eye and forewing colour patterns. Besides external phenotypic traits, the length of genital organs like aedeagus and valva in males, and bursa copulatrix and bursa seminalis in females also differed significantly amongst populations. The dendrogram based on selected traits showed clear cut differentiation of studied populations into two major groups, one including all the South Zone populations and the other having populations from North and Central Zones. Differences based on phenotyping in the present study indicate the possibility of the existence of different subspecies within the Indian populations of H. armigera.     

Processes that drive the population structuring of Jenynsia lineata (Cyprinidontiformes,Anablepidae) in the La Plata Basin

1. The distribution of genetic diversity across a species distribution range is rarely homogeneous, as the genetic structure among populations is related to the degree of isolation among them, such as isolation by distance, isolation by barrier, and isolation by environment.
2. Jenynsia lineata is a small viviparous fish that inhabits a wide range of habitats in South America. To decipher the isolation processes that drive population structuring in J. lineata, we analyzed 221 sequences of the mitochondrial cytochrome c oxidase I gene (COI), from 19 localities. Then, we examined the influence of the three most common types of isolation in order to explain the genetic variation found in this species.
3. Our results revealed a marked structuration, with three groups: (a) La Plata/Desaguadero Rivers (sampling sites across Argentina, Uruguay, and Southern Brazil), (b) Central Argentina, and (c) Northern Argentina. A distance‐based redundancy analysis, including the explanatory variables geographical distances, altitude, latitude, and basin, was able to explain up to 65% of the genetic structure. A variance partitioning analysis showed that the two most important variables underlying the structuration in J. lineata were altitude (isolation by environment) and type of basin (isolation by barrier).
4. Our results show that in this species, the processes of population diversification are complex and are not limited to a single mechanism. The processes that play a prominent role in this study could explain the high rate of diversity that characterizes freshwater fish species. And these processes in turn are the basis for possible speciation events.

     

Genetic diversity of Helosciadium repens (Jacq.) W.D.J. Koch (Apiaceae) in Germany,a Crop Wild Relative of celery

• Helosciadium repens (Jacq.) W.D.J. Koch is threatened by genetic erosion. It is a Crop Wild Relative (CWR) of celery and celeriac and a potentially valuable genetic resource for plant breeding. The objective of this study was the analysis of distribution of genetic diversity with a set of selected populations in Germany. The results of the genetic analysis and data obtained during the site visits were used to identify a subset which was chosen to best represent the genetic diversity of H. repens in Germany. The chance of long‐term conservation by securing the identified populations in genetic reserves is distinctly possible.
• Seven hundred and fifteen individuals from 27 sites were assessed using six simple sequence repeat markers. Discriminant analysis of principal components was used to identify six clusters of genetically similar individuals. The complementary compositional genetic differentiation Δj was calculated to designate a subset of populations chosen to best represent the overall genetic diversity. Entry 18R (Δ_18R = 0.2498) represented its pooled remainder the best, while entry 22R (Δ_22R = 0.4902) differed the most from its complement.
• Based on the results of the genetic analysis and information regarding the current conservation status, 14 most appropriate wild populations for potential genetic reserve were identified. The used markers display a low level of genetic variation between the analyzed populations, and a split between Northern and Southern populations was observed.
• CWR species are essential genetic resources for plant breeding and food security. However, 11.5% of the European CWRs are threatened. Therefore, it is of utmost importance to determine their genetic compositions. These insights will provide the fundamental basis for making crucial decisions concerning future conservation strategies for H. repens.

     

Crayfish populations genetically fragmented in streams impounded for 36–104 years

1. Dams and their associated impoundments may restrict dispersal and gene flow among populations of numerous freshwater species within stream networks, leading to genetic isolation. This can reduce effective population sizes and genetic diversity, increasing the risk of local extinction.
2. We studied crayfishes from multiple up- and downstream sites in three impounded and two unimpounded streams in the Bear Creek and Cahaba River drainages, Alabama, U.S.A. Using mitochondrial DNA (cytochrome oxidase subunit I gene) sequence data generated from population-level sampling of two abundant native crayfishes, Faxonius validus and Faxonius erichsonianus (Decapoda: Cambaridae), we assessed species’ spatial genetic structure and genetic diversity, estimated the magnitude and directionality of gene flow, and compared results between the species.
3. For both species, levels of genetic diversity (number of haplotypes, and haplotypic and nucleotide diversity) were the same or higher in impounded compared to unimpounded streams. Conversely, crayfish populations in up- and downstream sections of unimpounded streams displayed high genetic similarity and bidirectional gene flow, whereas in impounded streams, crayfish populations typically had greater up- and downstream genetic differentiation and predominantly unidirectional, downstream gene flow.
4. Although impoundments were associated with lower connectivity between up- and downstream sections for F. validus and F. erichsonianus, the magnitude of genetic effects was species-specific, with greater differentiation between F. validus populations up- and downstream of impoundments.
5. In an ecologically short timeframe, impoundments appear to have fragmented stream crayfish populations, and even species with relatively high abundances and large ranges had lower gene flow among populations in impounded streams compared to unimpounded streams. In addition, feedbacks between genetic and demographic effects on fragmented populations may decrease the probability of long-term persistence.

     

Time-concentration interplay in insecticide resistance among populations of the Neotropical coffee leaf miner,Leucoptera coffeella

1. Leucoptera coffeella is one of the main coffee pests in the Neotropical region and particularly important in crops cultivated under full sun, as in Brazil. The intensive use of insecticides in the last two decades, including molecules of recent use such as chlorantranilprole, has not been successful in suppressing this pest species.
2. Thus, study aimed to detect insecticide resistance and determine the levels of resistance to commercial formulations of the insecticides chlorantraniliprole, chlorpyrifos and thiamethoxam in populations of L. coffeella from Arabica coffee fields in western and the highlands of the state Bahia (Brazil). Furthermore, as the expression of insecticide toxicity varies with the length of exposure and the compound concentration, what is frequently neglected, these two variables were considered while determining the levels of resistance in nine populations.
3. Moderate levels of resistance were detected to chlorantranilprole in two populations, whereas the others exhibited low levels of resistance. All populations were resistant to thiamethoxam ranging from low to moderate levels. Low levels of resistance to chlorpyrifos were detected in all populations from western, but none from highlands region.
4. The western presents a more concerning scenario of insecticide resistance the L. coffeella, but the phenomenon requires attention in both regions.

     

Genetic structure of two Plusiinae species suggests recent expansion of Chrysodeixis includens in the American continent

1. The Plusiinae subfamily has many polyphagous species, many of which occur in South America. Chrysodeixis includens and Rachiplusia nu are two representatives that mainly occurs in soybeans, cotton, common beans, sunflower and alfalfa.
2. A population genetic study of C. includens and R. nu collected in the Southern Cone of America was performed using a partial COI gene sequencing data and compared with specimens from other American countries.
3. Six haplotypes were identified in C. includens populations of Brazil, Argentina, Paraguay and Uruguay, organized within a star-like haplotype network, with the most common haplotype identified as Chin_MC.
4. R. nu populations are more diverse and stable in comparison to C. includens. Populations from Argentina and Uruguay had the highest haplotype diversity, sharing five haplotypes and putatively indicating haplotype exchange.
5. Demographic change analysis suggested a recent population expansion of C. includens over the American continent.
6. Some C. includens haplotypes were country-specific, suggesting population expansion in the countries where specimens were collected.

     

Communication interference in sympatrically occurring moth species

In moth species, females emit a species‐specific sex pheromone that is perceived over long distance by conspecific males. The species‐specificity in the chemical communication channel is achieved by a combination of unique components in specific ratios and sometimes also by interspecific behavioural antagonists to deter sympatrically occurring heterospecific males. In this study, we determined possible antagonistic effects in Helicoverpa gelotopoeon Dyar (Lepidoptera: Noctuidae) males to the major sex pheromone component of sympatrically occurring heliothine moths, Z11‐16:Ald, as well as to the sex pheromone of the sympatrically occurring Heliothis virescens (Fabricius) (Lepidoptera: Noctuidae) (Z11‐16:Ald and Z9‐14:Ald). We also explored whether other co‐occurring species are attracted to these pheromone blends. Our field experiments showed that the addition of Z11‐16:Ald alone or in combination with Z9‐14:Ald inhibited trap catches of H. gelotopoeon males and that this inhibition depended on the concentration of these compounds. In addition, other moth species were attracted to the blends. Together, our results confirm the antagonistic effect of heterospecific sex pheromone compounds of H. virescens to H. gelotopoeon.     

Is population genetic structure of vascular plants shaped more by ecological or geographic factors? A study case on the Mediterranean endemic Centaurea filiformis (Asteraceae)

• All known populations of the Sardinian endemic Centaurea filiformis Viv. (Asteraceae) were studied in order to understand the impact of both geographic and ecological factors on the genetic structuring of this species.
• Fourteen populations and 234 individuals were sampled. The demographic structure of the populations and the reproductive ecology were estimated in 28 plots. Population genetic analyses were based on SSR markers. Genetic structure was investigated by spatial Bayesian methods.
• Average densities of 0.51 individuals m^?2 were detected, with a prevalence of adults. Ten species of pollinators were identified; C. filiformis ability to self‐pollinate and myrmecochory were demonstrated experimentally. The populations displayed an average heterozygosity value of H _e = 0.576 and high genetic differentiation (overall F _ST = 0.218). Bayesian analysis suggests that five is the most probable number of gene pools of origin. A strong correlation between geographic distances and genetic distances among populations was highlighted.
• The demographic population structure of C. filiformis is dominated by adults, suggesting that it is a stable‐regressive or senile species, investing more in local persistence than colonisation ability. Despite the scattered distribution, the populations studied do not present evidence of genetic erosion. The analysis of genetic differentiation reveals very high differentiation levels among populations, thus indicating that effective barriers exist against gene flow. A general conclusion is that population distribution results in a clear genetic structure for the populations studied, and that geography and not ecology is shaping the present distribution of this species.

     

Environmental gradients shape the genetic structure of two medicinal Salvia species in Jordan

• Environmental gradients, and particularly climatic variables, exert a strong influence on plant distribution and, potentially, population genetic diversity and differentiation. Differences in water availability can cause among‐population variation in ecological processes and can thus interrupt populations’ connectivity and isolate them environmentally. The present study examines the effect of environmental heterogeneity on plant populations due to environmental isolation unrelated to geographic distance.
• Using AFLP markers, we analyzed genetic diversity and differentiation among 12 Salvia spinosa populations and 13 Salvia syriaca populations from three phytogeographical regions (Mediterranean, Irano‐Turanian and Saharo‐Arabian) representing the extent of the species’ geographic range in Jordan. Differences in geographic location and climate were considered in the analyses.
• For both species, flowering phenology varied among populations and regions. Irano‐Turanian and Saharo‐Arabian populations had higher genetic diversity than Mediterranean populations, and genetic diversity increased significantly with increasing temperature. Genetic diversity in Salvia syriaca was affected by population size, while genetic diversity responded to drought in S. spinosa. For both species, high levels of genetic differentiation were found as well as two well‐supported phytogeographical groups of populations, with Mediterranean populations clustering in one group and the Irano‐Turanian and Saharo‐Arabian populations in another. Genetic distance was significantly correlated to environmental distance, but not to geographic distance.
• Our data indicate that populations from moist vs. arid environments are environmentally isolated, where environmental gradients affect their flowering phenology, limit gene flow and shape their genetic structure. We conclude that environmental heterogeneity may act as driver for the observed variation in genetic diversity.

     

Phylogeography of a salmonid fish,masu salmon Oncorhynchus masou subspecies-complex,with disjunct distributions across the temperate northern Pacific

1. Climate oscillations during the Pleistocene had profound effects on the evolutionary history of freshwater fishes now distributed across northern temperate regions. The extent of continental glaciation on the western side of the North Pacific, including areas of East Asia, was more limited as compared with regions of North America, Europe and high-latitude areas of the North Pacific. Therefore, the effects of climate oscillations might have influenced species in dissimilar ways depending on the species' distribution.
2. We used mitochondrial DNA (mtDNA) and microsatellite DNA (msDNA) markers to clarify the evolutionary history of masu salmon Oncorhynchus masou subspecies-complex (family Salmonidae) distributed in historically non-glaciated regions in the western North Pacific.
3. No marked regional or subspecies-specific mtDNA haplotype associations were recognised, except for O. masou subsp., a lacustrine form endemic to Lake Biwa, an ancient lake in central Honshu. The landlocked subspecies O. masou formosanus, with a disjunct distribution on Taiwan Island, exhibited no diagnostic population features differing from the other subspecies, in either mtDNA or msDNA markers. Mismatch distribution and Bayesian skyline plot analyses indicated relatively recent range expansion and rapid population growth for masu salmon during the last glacial period (c. 0.1–0.15 Ma).
4. Contrary to the mtDNA genealogy, Bayesian clustering using msDNA showed two main genetic clusters, mainly northern populations of the subspecies O. m. masou and populations of the subspecies O. m. ishikawae in southern areas of the Japanese Archipelago. Notably, O. m. formosanus on Taiwan Island was included in the O. m. masou group, and O. masou subsp. was included in the O. m. ishikawae group.
5. Our results suggest that the masu salmon subspecies-complex in historically non-glaciated regions of the Temperate Northern Pacific is characterised by weak population structuring and shallow genetic differentiation among the subspecies, except for O. masou subsp. owing to its long isolation in Lake Biwa. Incomplete lineage sorting and historical inter-subspecies hybridisation, possibly due to secondary contact, seem to be plausible explanations for discrepancies in the mitochondrial DNA genealogy and nuclear DNA genetic structure.

     

Historical,human, and environmental drivers of genetic diversity in the red swamp crayfish (Procambarus clarkii) invading the Iberian Peninsula

1. Patterns of genetic diversity in invasive populations can be modulated by a range of factors acting at different stages of the invasion process, including the genetic composition of the source population(s), the introduction history (e.g. propagule pressure), the environmental suitability of recipient areas, and the features of secondary introductions.
2. The North American red swamp crayfish, Procambarus clarkii, is one of the most widely introduced freshwater species worldwide. It was legally introduced into Spain twice, near the city of Badajoz in 1973 and in the Guadalquivir marshes in 1974. Thereafter the species rapidly colonised almost the entire Iberian Peninsula.
3. We used seven nuclear microsatellites to describe the genetic diversity and structure of 28 locations distributed across the Iberian Peninsula and to explain the expansion process of the red swamp crayfish. Additionally, we analysed the relationship between environmental suitability and genetic diversity of the studied locations.
4. The red swamp crayfish had a clear spatial genetic structure in the Iberian Peninsula, probably determined by the two independent introduction events in the 1970s, which produced two main clusters separated spatially, one of which was dominant in Portugal and the other in Spain.
5. The human-mediated dispersal process seemed to have involved invasion hubs, hosting highly genetically diverse areas and acting as sources for subsequent introductions. Genetic diversity also tended to be higher in more suitable environments across the Iberian Peninsula .
6. Our results showed that the complex and human-mediated expansion of the red swamp crayfish in the Iberian Peninsula has involved several long- and short-distance movements and that both ecological and anthropogenic factors have shaped the genetic diversity patterns resulting from this invasion process. Early detection of potential invasion hubs may help to halt multiple short-distance translocations and thus the rapid expansion of highly prolific invasive species over non-native areas.

     

Genetic relationships among populations of Aedes aegypti from Uruguay and northeastern Argentina inferred from ISSR‐PCR data

Aedes aegypti (L.) (Diptera: Culicidae), the main vector of yellow fever and dengue viruses, was eradicated from Argentina between 1955 and 1963, but reinvaded the country in 1986. In Uruguay, the species was reintroduced in 1997. In this study we used highly polymorphic inter‐simple sequence repeats (ISSR) markers to analyse the genetic structure of Ae. aegypti populations from Uruguay and northeastern Argentina to identify possible colonization patterns of the vector. Overall genetic differentiation among populations was high (F_ST = 0.106) and showed no correlation with geographic distance, which is consistent with the short time since the reintroduction of the species in the area. Differentiation between pairs of Argentine populations (F_ST 0.072 to 0.221) was on average higher than between Uruguayan populations (F_ST?0.044 to 0.116). Bayesian estimation of population structure defined four genetic clusters and most populations were admixtures of two of them: Mercedes and Treinta y Tres (Uruguay) were mixtures of clusters 1 and 3; Salto (Uruguay) and Paraná (Argentina) of clusters 1 and 4; Fray Bentos (Uruguay) of clusters 2 and 3, and Gualeguaychú (Argentina) of clusters 2 and 3. Posadas and Buenos Aires in Argentina were fairly genetically homogeneous. Our results suggest that Ae. aegypti recolonized Uruguay from bordering cities in Argentina via bridges over the Uruguay River and also from Brazil.     

Peripheral genetic structure of Helicoverpa zea indicates asymmetrical panmixia

Seasonal climatic shifts create peripheral habitats that alternate between habitable and uninhabitable for migratory species. Such dynamic peripheral habitats are potential sites where migratory species could evolve high genetic diversity resulting from convergence of immigrants from multiple regionally distant areas. Migrant populations of Helicoverpa zea (Boddie) captured during two different seasons were assessed for genetic structure using microsatellite markers and for host plant type using stable carbon isotope analysis. Individuals (N = 568) were genotyped and divided into 13 putative populations based on collection site and time. Fixation indices (F‐statistics), analysis of molecular variance (AMOVA), and discriminant analysis of principal components (DAPC) were used to examine within and among population genetic variation. Mean number of alleles per locus was 10.25 (± 3.2 SD), and allelic richness ranged from 2.38 to 5.13 (± 3.2 SD). The observed and expected heterozygosity ranged from 0.07 to 0.48 and 0.08 to 0.62, respectively. Low F_ST (0.01 to 0.02) and high F_IS (0.08 to 0.33) values suggest captured migrants originated from breeding populations with different allele frequencies. We postulate that high genetic diversity within migrant populations and low genetic differentiation among migrant populations of H. zea are the result of asymmetrical immigration due to the high dispersal and reproductive behavior of H. zea, which may hinder the adaptation and establishment of H. zea to peripheral habitat. These findings highlight the importance of assessing peripheral population structure in relation to ecological and evolutionary dynamics of this and other highly reproductive and dispersive species.     

Comparison of susceptibility to a toxic alien toad (Bufo japonicus formosus) between predators in its native and invaded ranges

1. To manage biological invasions effectively, the impacts of alien species on the demography and traits of native species must be known, but determining those impacts can be challenging. We used a comparative approach to gain insight into the impacts that an alien toad (Bufo japonicus formosus) might have on native Japanese predatory amphibians. We compared the susceptibility of native predator species to alien toad toxins in the alien-invaded range and the susceptibility of closely related native predator species to the toxins in the alien toad's native range to investigate the impacts of an alien on a native species.
2. Bufo japonicus formosus is native to Honshu, but was recently introduced to Hokkaido and Sado. In laboratory experiments, we compared individual mortality of predators exposed to a toad hatchling between novel predators on the toad-invaded islands and ecologically similar congeneric or conspecific species on Honshu, where the toad is native. We also compared (1) the percentage of individuals that consumed a toad hatchling and (2) toxin resistance (i.e. survival and growth of individuals after toad consumption) between these two groups of predators, as mechanistic components behind the susceptibility of the predators to the toxic prey.
3. The mortality of Rana pirica from all populations after consumption of a toad hatchling was almost 100%, and that of Hynobius retardatus ranged from 14 to 90%, depending on the population. In contrast, the mortality of Rana ornativentris and Hynobius nigrescens was near 0% regardless of population. These differences between congeneric predators were mostly due to differences in their toxin resistance.
4. These results suggest that the alien toad is a potential threat to the novel amphibian predators on Hokkaido, although they also imply that the novel predators on Hokkaido have the potential to develop toxin resistance through adaptive evolution. However, this counteradaptation may have a higher chance of evolving in H. retardatus than in R. pirica because of differences in their genetic backgrounds.

     

Genetic patterns and changes in availability of suitable habitat support a colonisation history of a North American perennial plant

• Climatic fluctuations during the Pleistocene influenced the geographical distribution of plant species across the southern region of California. Following an integrative approach, we combined genetic data analysis with Environmental Niche Models (ENMs) to assess the historical range expansion of Yucca schidigera, a long‐lived desert perennial native of the Baja California Peninsula.
• We genotyped 240 individuals with seven nuclear microsatellite to investigate genetic diversity distribution across 13 populations. Indeed, we used Environmental Niche Models to examine the changes on the distribution of suitable climatic conditions for this species during the LIG (~120 ka), LGM (~22 ka) and Mid Holocene (~6 ka).
• We detected high genetic diversity across Y. schidigera populations (A_R = 9.94 ± 0.38 SE; H_exp = 0.791 ± 0.011 SE) with genetic variation decreasing significantly with latitude (allelic richness: R ² = 0.38, P = 0.023; expected heterocigosity: R² = 0.32, P = 0.042). We observed low, but significant genetic differentiation (F_ST = 0.0678; P < 0.001) which was consistent with the parapatric distribution of the three genetic groupings detected by the Bayesian clustering algorithm. The ENMs suggest that suitable habitat for this species increased since the LGM.
• Our results support a range expansion of Y. schidigera across northwestern Baja California during the late Quaternary. Genetic data suggest that colonization of the current distribution followed a southward directionality as suitable climatic conditions became widely available in this region. High genetic variation across our sample suggests large historic effective population sizes for this section of the geographical range.

     

Habitat requirements of Tetanocera elata (Diptera: Sciomyzidae): case study of a dry meadow in western Ireland

1. Terrestrial slugs are pervasive pests of agriculture throughout temperate regions and have the potential to disrupt the germination of seedlings, cause damage to fruiting bodies of crops, and vector plant pathogens.
2. Tetanocera elata Fabricius (Diptera: Sciomyzidae), a widely distributed Palaearctic species, is an obligate mesoparasitoid and predator of pestiferous slugs including Deroceras reticulatum Müller (Stylommatophora: Agriolimacidae). It has the potential to be developed as a native natural enemy in a conservation biological control programme as an alternative to chemical molluscicides.
3. To better understand the ecological requirements of this species, a detailed observational study was conducted at a site in the west of Ireland possessing naturally occurring T. elata populations.
4. Comparison of local patches where T. elata were recovered revealed no association with plant community composition.
5. Taller dead vegetation was associated with T. elata presence throughout the site. Within the area of greatest T. elata aggregation, there was a significantly greater percentage cover of dead vegetation where T. elata occurred. Abundance of T. elata was also significantly correlated to hedgerow proximity. Results of this study are directly applicable for the design of a conservation biological control programme, which effectively satisfies the principal habitat requirements of T. elata populations.

     

Host selection behaviour of the banded pine weevil,Pissodes castaneus (Coleoptera: Curculionidae)

1. Pissodes castaneus represents an emerging pest species for Pinus spp. production in Latin America. This species attacks all the cultivated pine species in Patagonia Argentina causing wood damage and tree death. The objectives of this work were to describe the host preference behaviour of P. castaneus and the influence of wood damage by conspecifics on its host selection.
2. In two-choice bioassays, P. castaneus showed a feeding preference for Pinus contorta over P. ponderosa. However, percent weight gain when feeding on either species was similar.
3. In other bioassays, P. castaneus spent more time in areas with twigs on which other conspecifics had recently fed, although they were able to successfully feed on twigs without previous damage.
4. These results show that while P. castaneus can successfully colonize different pine species, P. contorta may be more susceptible to attack than P. ponderosa. Silvicultural management should be prioritized considering the weevil's preference for attacking damaged hosts.

     

Postintroduction evolution contributes to the successful invasion of Chromolaena odorata

1. The evolution of increased competitive ability (EICA) hypothesis states that, when introduced in a novel habitat, invasive species may reallocate resources from costly quantitative defense mechanisms against enemies to dispersal and reproduction; meanwhile, the refinement of EICA suggests that concentrations of toxins used for qualitative defense against generalist herbivores may increase. Previous studies considered that only few genotypes were introduced to the new range, whereas most studies to test the EICA (or the refinement of EICA) hypotheses did not consider founder effects.
2. In this study, genetic and phenotypic data of Chromolaena odorata populations sampled across native and introduced ranges were combined to investigate the role of postintroduction evolution in the successful invasion of C. odorata.
3. Compared with native populations, the introduced populations exhibited lower levels of genetic diversity. Moreover, different founder effects events were interpreted as the main cause of the genetic structure observed in introduced ranges. Three Florida, two Trinidad, and two Puerto Rico populations may have been the sources of the invasive C. odorata in Asia.
4. When in free of competition conditions, C. odorata plants from introduced ranges perform better than those from native ranges at high nutrient supply but not at low nutrient level. The differences in performance due to competition were significantly greater for C. odorata plants from the native range than those from the introduced range at both nutrient levels. Moreover, the differences in performance by competition were significantly greater for putative source populations than for invasive populations.
5. Quantities of three types of secondary compounds in leaves of invasive C. odorata populations were significantly higher than those in putative source populations. These results provide more accurate evidence that the competitive ability of the introduced C. odorata is increased with postintroduction evolution.