Di‐ and trinucleotide repeat microsatellites for the parasitoid wasp,Aphidius transcaspicus

The Mediterranean parasitoid Aphidius transcaspicus is currently under investigation as a potential biological control agent for the mealy plum aphid, Hyalopterus pruni, in California. To better understand the biology of this parasitoid, including the potential existence of distinct strains or geographic races, we have developed a set of nine di‐ and trinucleotide repeat microsatellite markers. These markers were examined for variability in individuals from throughout the geographic distribution of A. transcaspicus, and we found between three and 19 alleles per locus. These are the first loci developed for A. transcaspicus and they will be of value in studying the population structure of this potential biocontrol agent and for future diagnostics.     

Genetic heterogeneity, reproductive isolation and host preferences in mealy aphids of the Hyalopterus pruni complex (Homoptera, Aphidoidea)

Three taxa were detected by allozyme markers within the mealy aphids of the Hyalopterus pruni complex, having different cultivated Prunus species as main primary hosts. The genetically closer H. pruni and H. amygdali A ( D _Nei= 0.10) never share primary hosts, whereas H. amygdali A and B ( D _Nei= 0.32) may occasionally share them, producing few F₁ hybrids. The three species proved reproductively isolated in the field, with no gene exchange. Their speciation seem to have occurred long before the agricultural revolution, crop colonization representing a host range expansion rather than a host shift, as in sympatric speciation.     

Genetic evidence from mitochondrial, nuclear, and endosymbiont markers for the evolution of host plant associated species in the aphid genus Hyalopterus (Hemiptera: Aphididae)

Over the past several decades biologists' fascination with plant-herbivore interactions has generated intensive research into the implications of these interactions for insect diversification. The study of closely related phytophagous insect species or populations from an evolutionary perspective can help illuminate ecological and selective forces that drive these interactions. Here we present such an analysis for aphids in the genus Hyalopterus (Hemiptera: Aphididae), a cosmopolitan group that feeds on plants in the genus Prunus (Rosaceae). Hyalopterus currently contains two recognized species associated with different Prunus species, although the taxonomy and evolutionary history of the group is poorly understood. Using mitochondrial COI sequences, 16S rDNA sequences from the aphid endosymbiont Buchnera aphidicola, and nine microsatellite loci we investigated population structure in Hyalopterus from the most commonly used Prunus host species throughout the Mediterranean as well as in California, where the species H. pruni is an invasive pest. We found three deeply divergent lineages structured in large part by specific associations with plum, almond, and peach trees. There was no evidence that geographic or temporal barriers could explain the overall diversity in the genus. Levels of genetic differentiation are consistent with that typically attributed to aphid species and indicate divergence times older than the domestication of Prunus for agriculture. Interestingly, in addition to their typical hosts, aphids from each of the three lineages were frequently found on apricot trees. Apricot also appears to act as a resource mediated hybrid zone for plum and almond associated lineages. Together, results suggest that host plants have played a role in maintaining host-associated differentiation in Hyalopterus for as long as several million years, despite worldwide movement of host plants and the potential for ongoing hybridization.     

Tracing the invasion history of mealy plum aphid, Hyalopterus pruni (Hemiptera: Aphididae), in North America: a population genetics approach

Biological invasions are typically the outcome of complex patterns of introduction, establishment, and spread, and genetic methods are excellent tools to resolve such histories for non-native organisms. The mealy plum aphid, Hyalopterus pruni, is an invasive pest of dried plum in California. We examined nine microsatellite loci and DNA sequences from three mitochondrial genes (1,148 bp) in populations throughout the native and invaded ranges of H. pruni to assess key invasion parameters, including geographic origins of invasive populations, number of introductions, and levels of genetic diversity and gene flow. Our results provide evidence for multiple invasions of H. pruni into North America, suggesting that aphids in California may have been introduced from Spain, and aphids in the eastern United States and Vancouver, Canada were likely introduced from central or northern Europe. H. pruni populations in California were characterized by low genetic diversity relative to native populations, while the two other North American populations were less genetically impoverished. Gene flow among introduced populations was low, but does appear to occur with some regularity. These findings provide a framework for more detailed studies of H. pruni, but also represent a model for how population genetics approaches can be used to study invasion biology and aid the development of optimized management methods for agricultural pests. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Paragus hyalopteri n. sp. an aphidophagous hoverfly (Dipt.: Syrphidae) attacking the mealy plum aphid (Hom.: Aphididae)

Paragus hyalopteri Marcos-García et Rojo n. sp. is described. The new species was caught in Alicante province (SE Spain). This species is morphologically close toParagus quadrifasciatus Meigen, 1822. It was collected on several species of fruit trees of the genusPrunus, upon the mealy plum aphidHyalopterus pruni (Geoffroy, 1762).     

Isolation and characterization of di‐ and trinucleotide microsatellites in the freshwater snail Potamopyrgus antipodarum

The freshwater prosobranch snail Potamopyrgus antipodarum is an important model system for studying the maintenance of sexual reproduction in its native New Zealand. Since introduction to the UK in the 1850s, the species has spread throughout Europe and recently the USA. We present the first microsatellites for P. antipodarum. Using two isolation protocols, which are qualitatively compared, we have developed PCR primers for three di‐ and four trinucleotide microsatellites. All loci proved to be polymorphic, when screened for variability in several UK populations. These markers should be of considerable utility in future population and ecological genetics studies of this species.     

Simple‐sequence repeat (SSR) markers of Japanese plum (Prunus salicina Lindl.) are highly polymorphic and transferable to peach and almond

Thirty‐five polymorphic microsatellites were developed using a CT/AG enriched genomic library of Japanese plum cv. Santa Rosa. Twenty‐seven of them detected a single locus and eight two or more loci. A high level of variability was observed in a set of eight cultivars for the 27 single‐locus microsatellites: 5.7 average number of alleles per locus; 73% mean observed heterozygosity and 74% discrimination power. Most SSRs were transferable to peach (85%) and almond (78%).     

Relative consumption of three aphid species by the lacewing, Chrysoperla rufilabris, and effects on its development and survival

Relative consumption of three aphid species, Aphis gossypii Glover, Myzus persicae (Sulzer) and Lipaphis erysimi (Kaltenbach) (Homoptera: Aphididae), by larvae of the lacewing, Chrysoperla rufilabris (Burmeister) (Neuroptera: Chrysopidae), was determined in the laboratory, together with effects on lacewing development and survival. Percentages of survival of C. rufilabris from first instar to adult eclosion were significantly different among lacewing larvae fed different aphid species. When larvae were fed A. gossypii and M. persicae, all larvae developed to adulthood. All larvae died prematurely when they were fed L. erysimi. Developmental duration of C. rufilabris larvae was significantly shorter when larvae were fed A. gossypii (18.0 d) than when larvae were fed M. persicae (19.2 d). The number of fourth instar aphids consumed during development by C. rufilabris larvae differed significantly among individuals fed different aphid species. Chrysoperla rufilabris consumed an average of 168 M. persicae, followed by 141.6 A. gossypii, and only 26.6 L. erysimi. The percentage of these total number of aphids consumed by each larval stadium of C. rufilabris varied significantly among aphid species. The percentage of A. gossypii consumed by each larval stadium was similar to that for M. persicae, 12.1 and 11.4% by the first instar, 15.7 and 13.1% by the second instar, and 72.2 and 75.5% by the third instar, respectively; whereas in the case of L. erysimi, 23.3% of the total number of aphids were consumed by the first instar, 30.1% by the second instar, and 46.6% by the third instar.     

Impact of predation on establishment of the soybean aphid, <Emphasis Type="Italic">Aphis glycines</Emphasis> in soybean, <Emphasis Type="Italic">Glycine max</Emphasis>

The soybean aphid, Aphis glycines Matsumura is a new invasive pest of soybean in North America. We studied the ability of the existing predator community in soybean to reduce A. glycines establishment in field studies using either predator exclusion, open, or leaky cages that allowed aphid emigration but limited predation. Cages were infested with uniform initial densities of A. glycines adults and subsequent populations of aphids and predators were monitored over 24 h. The most abundant predators in these trials included the carabid beetles Elaphropus anceps (Le Conte), Clavina impressefrons Le Conte, Bembidion quadrimaculatum Say and spiders (Salticidae and Lycosidae). Foliar predators were less abundant and included; Harmonia axyridis Pallas, Coccinella septempunctata (L.), and Orius insidious (Say). Over the 2-year study, we found statistically significant predation on adult A. glycines in one out of six trials at 15 h and two out of six trials at 24 h. There was never significant evidence for predation of nymphs in any trial, however overall survival (adults + nymphs) was significantly reduced in one out of six trials at 15 h and three out of six trials at 24 h. Based on these results we suggest that generalist predators can be a significant but variable factor influencing the establishment of A. glycines populations in soybean. The impact of existing predator communities should be further investigated as a means of managing A.␣glycines populations in North American soybean production systems.     

Host‐associated differentiation and evidence for sexual reproduction in Iranian populations of the cotton aphid,Aphis gossypii

Phytophagous insects with wide host ranges often exhibit host‐associated genetic structure. We used microsatellite analysis to assess the population structure of the cotton aphid, Aphis gossypii Glover (Hemiptera: Aphididae), a serious pest on many economically important crops worldwide. We sampled aphids from five host plant species in Iran and detected strong population subdivision, with an overall multilocus F_ST of 0.191. The matrix of pairwise F_ST values indicated that differentiation between populations collected from different hosts was significantly stronger than between populations from the same hosts. Host‐associated differentiation was further supported by Bayesian clustering analyses, which grouped all samples from cotton together with aubergine, and all samples from cucumber together with pumpkin and hibiscus. This adds to the growing body of evidence that many seemingly generalist aphids are in fact an assemblage of host‐specialized lineages. Although we detected a clear genetic signature of clonal reproduction, the genotypic diversity of A. gossypii in Iran is much higher than in other parts of the world. Particularly samples from cotton exhibited a surprisingly high genotypic diversity, suggesting that many lineages on this host are cyclical parthenogens that engage in regular bouts of sexual reproduction.     

Di‐ and tetranucleotide microsatellite markers for the Alpine newt (Triturus alpestris): characterization and cross‐priming in five congeners

We developed a set of di‐ and tetranucleotide microsatellite markers for the Alpine newt, Triturus alpestris. Polymorphism as detected in 39 individuals ranged from 3 to 32 alleles at a locus. Cross‐priming with samples of five other Triturus species showed extremely poor levels of cross‐species utility. Still, these markers are suitable for studies of inter‐ and intrapopulation genetic diversity in the focal species.     

When North and South don’t mix: genetic connectivity of a recently endangered oceanic cycad,Cycas micronesica,in Guam using EST‐microsatellites

Subject to environmental changes and recurrent isolation in the last ca. 250 Ma, cycads are often described as relicts of a previously common lineage, with populations characterized by low genetic variation and restricted gene flow. We found that on the island of Guam, the endemic Cycas micronesica has most of the genetic variation of 14 EST‐microsatellites distributed within each of 18 genetic populations, from 24 original sampling sites. There were high levels of genetic variation in terms of total number of alleles and private alleles, and moderate levels of inbreeding. Restricted but ongoing gene flow among populations within Guam reveals a genetic mosaic, probably more typical of cycads than previously assumed. Contiguous cycad populations in the north of Guam had higher self‐recruitment rates compared to fragmented populations in the south, with no substantial connection between them except for one population. Guam’s genetic mosaic may be explained by the influence of forest continuity, seed size, edaphic differences, and human transport of cycads. Also important are the extent of synchrony among flushes of reproductive female seed‐bearing sporophylls and restricted pollen movement by an obligate mutualist and generalist insects. An NADH EST‐locus under positive selection may reflect pressure from edaphic differences across Guam. This and three other loci are ideal candidates for ecological genomic studies. Given this species’ vulnerability due to the recent introduction of the cycad aulacaspis scale, we also identify priority populations for ex situ conservation, and provide a genetic baseline for understanding the effects of invasive species on cycads in the Western Pacific, and islands in general.     

Response of the melon aphid, Aphis gossypii, to host-plant resistance: evidence for high adaptive potential despite low genetic variability

In agrosystems, pests are submitted to strong human-imposed selective pressures to which they sometimes adapt rapidly, either through selection of genotypes resulting from mutation and/or recombination events, or through phenotypic plasticity. Understanding how insects respond to such selective pressures is of great importance for sustainable pest management strategies, such as the use of resistant plants. In this study, we investigated the genetic and phenotypic variability of anholocyclic Aphis gossypii Glover (Hemiptera: Aphididae) strains, in response to the resistance gene Vat that is present in melon crops. Forty-nine aphid colonies were sampled on several melon crops in southern France, genotyped using 15 microsatellite loci, and tested in phenotypic experiments using Vat or non- Vat melons. The level of genetic polymorphism between these colonies was low, as only seven multilocus genotypes were detected. In contrast, the phenotypic variability for life-history and behavioral traits between colonies, including those sharing the same genotype, was unexpectedly high, with a continuum of response to the Vat gene from complete susceptibility to strong virulence. The low genetic polymorphism associated with a strong phenotypic variability highlights the high adaptive potential of A. gossypii and the major role of environmental cues in shaping phenotypic responses of this aphid to pest management strategies.     

Di‐, tri‐ and tetranucleotide microsatellite loci for the giant panda,Ailuropoda melanoleuca

We describe 10 polymorphic microsatellite loci for the giant panda, Ailuropoda melanoleuca. Microsatellite sequences were isolated from three partial genomic libraries of giant panda DNA that were enriched for (i) (GT), (ii) (GAA) & (CAA), and (iii) (GATA) repeat sequences. The markers were tested for polymorphism in up to 82 pandas. Number of alleles at each locus varied between four and 11, and the observed and expected heterozygosities varied between 0.267 and 0.732, and between 0.601 and 0.799, respectively.     

Food quality of Ephestia eggs,the aphid Rhopalosiphum padi and mixed diet for Orius majusculus

We studied the food quality of the aphid Rhopalosiphum padi to the pirate bug Orius majusculus using Ephestia eggs as high-quality comparison prey. Several performance parameters were tested on individuals that had been reared and maintained on each of the two single-prey diets or on a mixed diet. All fitness parameters were lower in individuals fed aphids only, indicating poor food quality of this prey. Compared with the pure Ephestia egg diet, the mixed diet enhanced teneral mass, while adult survival and female starvation tolerance were negatively affected and all other traits were unaffected. Body protein proportions were constant across diets, whereas lipid proportion was low in the aphid treatment. Preference for aphids was lower following a monotypic aphid diet than when reared on Ephestia eggs or a mixed diet. The results confirm that R. padi is low-quality food for O. majusculus as it is for other generalist predators, even though O. majusculus may contribute significantly to population suppression of the aphid.     

Additional microsatellites for Sparus aurata and cross‐species amplification within the Sparidae family

Six new microsatellite loci were isolated and characterized in 32 individuals from a farm population of gilthead seabream (Sparus aurata). Expected heterozygosity at all loci was high, ranging from 0.835 to 0.958 with between 10 and 27 alleles per locus. A multiplex polymerase chain reaction protocol was developed using four of the loci. Cross‐species amplification of the loci was tested in six species of the Sparidae family and four loci were successfully amplified in two or more related species.     

Isolation and characterization of polymorphic microsatellites in the Potato Tuber Moth Tecia solanivora (Povolny, 1973) (Lepidoptera: Gelechiidae)

Nine polymorphic microsatellite markers were isolated from Tecia solanivora, one of the most serious pests of potato tubers in Central and South America. As found in other studies of Lepidoptera, development of microsatellites is a difficult task: in our case, despite the large number of clones sequenced (796), of which 70 were unique, only nine loci were found to be both variable, and in Hardy-Weinberg equilibrium, No null alleles were detected. The loci were tested in three other co-occurring Gelechiidae species, one of which was variable. These loci will be used to provide a greater understanding of the genetic changes occurring during the invasive process in this species.     

Mealybug, Phenococcus solani, and barley aphid, Sipha maydis, response to endophyte-infected tall and meadow fescues

Mealybugs and aphids are insects which damage grass species. The effects of fungal endophytes on the feeding of the mealybug, Phenococcus solani Ferris (Homoptera: Pseudococcidae), and barley aphid, Sipha maydis Passerini (Homoptera: Aphididae), on tall fescue, Festuca arundinacea Schreb. and meadow fescue, Festuca pratensis Huds., were studied under greenhouse conditions. Mealybugs preferred endophyte‐free (E–) clones over their endophyte‐infected (E+) counterparts. E+ plants had a significantly lower number of mealybugs than E– plants. A mixture of E+ and E– plants supported intermediate mealybug numbers, between pure plantings of E+ and E– grasses. Barley aphids released on to plant materials were deterred from feeding and could not persist on E+ plants. E– plants did not survive because of aphid damage, while E+ plants generally re‐grew, but were damaged to some degree. The results showed that the use of pure stands of endophyte‐infected grasses or a mixed stand of infected and non‐infected plants may increase the persistence and durability of turf and forage grass species in the presence of foliar damaging insects.     

Bottom‐up effects mediated by an organic soil amendment on the cabbage aphid pests Myzus persicae and Brevicoryne brassicae

Earthworm‐produced compost or vermicompost has been shown to increase resistance of plants to a variety of insect pests, but it is still unclear whether this resistance is dose dependent and whether the mechanisms responsible are the same for insect species with differing feeding habits and preferences. Therefore, we tested the effects of plants grown in various vermicompost concentrations (0, 20, 40, and 60%) on the preference and performance of generalist, Myzus persicae L., and specialist, Brevicoryne brassicae L. (both Hemiptera: Aphididae), aphid pests. Preference was evaluated with leaf disk (apterous) and whole plant (alate) choice assays. After 24 h of feeding, there was no significant negative effect on the feeding preference noted for apterae of either species of any of the treatments tested. To the contrary, apterae B. brassicae showed a significant preference for vermicompost treatments over control leaf disks. Alate M. persicae preferred alighting on control plants over vermicompost‐grown plants, but B. brassicae showed no preference toward any of the treatments tested. Both aphid species deposited significantly more nymphs on control plants than on those grown in 20% vermicompost. Furthermore, plants grown in soil amended with 20% vermicompost significantly suppressed mass accumulation, as well as numbers of adults and nymphs of both aphid species compared to controls. These data clearly show that vermicompost soil amendments can significantly influence pest aphid preference and performance on plants and that these effects are not dose dependent, but rather species and morph dependent.