Characterization of microsatellite loci in a seed chalcid,Megastigmus spermotrophus (Hymenoptera: Torymidae)

Highly polymorphic microsatellite markers can supply demographic information on founder events and range expansion following initial introduction of invasive insect species. Six microsatellite loci were isolated from a partial DNA library in order to study the invasion patterns of a seed chalcid, Megastigmus spermotrophus, introduced to Europe and New Zealand. Allelic diversity at all described loci was high, ranging from 17 to 30 alleles per locus. All six loci were successfully amplified in 15 congeneric species.     

Olfactory responses of seed wasps Megastigmus pinus Parfitt and Megastigmus rafni Hoffmeyer (Hym., Torymidae) to host-tree odours and some monoterpenes

Megastigmus pinus and Megastigmus rafni are able to colonize the seed cones in eight different species of Abies in Denmark. Olfactory responses of M. pinus females from Abies alba and Abies procera seeds and of M. rafni females from A. alba and Abies grandis seeds to odours of different host-trees cones, needles and pure alpha-pinene and limonene were studied in a Y tube Plexiglas olfactometer. The odours of young cones significantly influenced the behaviour of females. The results obtained in experiments with cones from different trees indicate the occurrence of biotypes depending on the host tree within the M. pinus and M. rafni species. Megastigmus pinus females from A. procera cones preferred the cone odours of A. procera and were significantly repelled by the cone odours of other possible host trees. Megastigmus pinus females from A. alba cones preferred A. alba cone odour but were not indifferent to A. procera cones. This suggests that the M. pinus population in A. alba apparently originates from the A. procera population. Megastigmus rafni from A. grandis cones preferred only A. grandis cone odours. Megastigmus rafni females from A. alba cones preferred A. alba cone odour but were also significantly attracted by A. grandis cone odours. This probably indicates that the M. rafni population living in A. alba originates from the A. grandis population. Neither M. pinus nor M. rafni responded to the odours of the host-tree needles or alpha-pinene. The limonene odour significantly acted as a repellent to both seed chalcid species, independent of the origin-tree.     

Comparative phylogeography across two trophic levels: the oak gall wasp Andricus kollari and its chalcid parasitoid Megastigmus stigmatizans

Insect parasitoids are important components of many terrestrial ecosystems. However, relatively little is known about the mechanisms responsible for structuring their populations. Here we investigate the ability of Megastigmus stigmatizans, an oak gall wasp parasitoid, to track its host Andricus kollari over two different timescales, and examine its current population structure across a divide in host population structure. The divide represents a transition in gall wasp host-plant species and offers the opportunity to examine whether the split, which divides gall wasp populations, manifests itself in the next trophic level. Analysis of mitochondrial haplotype data for parasitoid and host reveals: (i) A similar phylogeographic population structure for both, with Iberian populations more derived with respect to more eastern populations. (ii) It is likely that the host colonized the Iberian refuge earlier than the parasitoid, probably by at least one glacial cycle. (iii) Recent range expansion of central European host populations northwards has resulted in pursuit by parasitoids from the same geographic origin. (iv) In addition, Iberian parasitoid populations have crossed a major divide in host population structure to invade northern Europe. Such human-facilitated escape from natural refugial distributions may have important implications for the composition and structure of northern European gall wasp communities.     

Chromosome-level de novo genome assembly of two conifer-parasitic wasps,Megastigmus duclouxiana and Megastigmus sabinae,reveals genomic imprints of adaptation to hosts

Conifers make up about one third of global forests but are threatened by seed parasitoid wasp species. Many of these wasps belong to the genus Megastigmus, yet little is known about their genomic background. In this study, we provide chromosome-level genome assemblies for two oligophagous conifer parasitoid species of Megastigmus, which represent the first two chromosome-level genomes of the genus. The assembled genomes of Megastigmus duclouxiana and M. sabinae are 878.48 Mb (scaffold N50 of 215.60 Mb) and 812.98 Mb (scaffold N50 of 139.16 Mb), respectively, which are larger than the genome size of most hymenopterans due to the expansion of transposable elements. Expanded gene families highlight the difference in sensory-related genes between the two species, reflecting the difference in their hosts. We further found that these two species have fewer family members but more single-gene duplications than polyphagous congeners in the gene families of ATP-binding cassette transporter (ABC), cytochrome P450 (P450) and olfactory receptors (OR). These findings shed light on the pattern of adaptation to a narrow spectrum of hosts in oligophagous parasitoids. Our findings suggest potential drivers underlying genome evolution and parasitism adaptation, and provide valuable resources for understanding the ecology, genetics and evolution of Megastigmus, as well as for the research and biological control of global conifer forest pests.     

圆柏大痣小蜂幼虫龄期测定

明确圆柏大痣小蜂Megastigmus sabinae Xu et He（1989）幼虫的最佳分龄指标、幼虫龄数与各虫龄龄期,为探明圆柏大痣小蜂幼虫期的生长规律奠定基础。本研究通过测量圆柏大痣小蜂幼虫上颚关节宽、头宽、体宽和体长4个形态指标,利用频次分布推测幼虫龄数,运用Crosby生长法则和线性回归的方法判断圆柏大痣小蜂幼虫的最佳分龄指标并验证幼虫的龄数。将最佳分龄指标作为龄期判断依据,根据测量结果对其幼虫龄期进行划分。圆柏大痣小蜂幼虫共划分为5个龄期,上颚关节宽为圆柏大痣小蜂幼虫龄期划分的最佳形态指标,各龄幼虫的历期约为30 d、200 d、30 d、30 d、15 d,共305 d,主要以2龄越冬。     

Twelve polymorphic microsatellites in Oriental river prawn, Macrobrachium nipponense

Oriental river prawn, Macrobrachium nipponense, is a commercially important freshwater prawn species in China, Japan, Korea and Vietnam. Due to overfishing for food, the wild stocks M. nipponense are endangered. Twenty microsatellite loci were isolated from the M. nipponense. Twelve of these loci were polymorphic (seven to 16 alleles per locus), with expected heterozygosity ranging from 0.68 to 0.86 (n = 48). These polymorphic loci provide a valuable tool for assessing genetic diversity of wild and cultured populations.     

Development of Genomic SSR Markers and Molecular Characterization of Magnaporthe oryzae Isolates from Wheat in Brazil

Magnaporthe oryzae, the causal agent of wheat blast, was characterized on a molecular level with 38 newly isolated genomic SSR loci. Among the 31 wheat isolates analyzed, 15 polymorphic loci were detected, with an average of 1.7 alleles per locus, 28.9% of them being highly or reasonably informative. The number of polymorphic loci was higher in isolates from Londrina in the Brazilian state of Paraná and Coromandel in Minas Gerais compared with Goiânia in Goiás and São Borja in Rio Grande do Sul. The rice isolate was clearly different from the wheat isolates, and the size difference in polymorphic SSR loci between one isolate from wheat and one isolate from rice was associated with the number of repeats. Some isolates collected from different states and in different years demonstrated similarities of 100%. The markers developed here are useful for the genetic analysis of M. oryzae isolated from wheat, and isolates representing the variability detected in the field can be used to search for better wheat blast resistance.     

Development of eighteen tetranucleotide microsatellite markers in Tibetan Macaque (Macaca thibetana) and genetic diversity analysis of captive population

In this study, eighteen tetranucleotide microsatellite loci were isolated from AAAG-enriched and GATA-enriched libraries of the Tibetan macaque, Macaca thibetana. These loci were tested on 53 individuals of M. thibetana, and most loci were proved to be highly polymorphic. A total of 109 alleles were detected with an average of 6.06 alleles per locus. The PIC values of these loci ranged from 0.192 to 0.879, with an average of 0.624. The observed and expected heterozygosities ranged from 0.170 to 0.800 and from 0.217 to 0.898, with an average of 0.583 and 0.675, respectively. 5 loci significantly deviated from Hardy–Weinberg equilibrium (HWE). Significant linkage disequilibrium (LD) was found between 9 pairs of loci. The newly identified polymorphic markers would facilitate the study of M. thibetana on the population structure and genetic diversity.     

Microsatellite markers for the common vole (<Emphasis Type="Italic">Microtus arvalis</Emphasis>) and their cross-species utility

Fragmentation of natural habitats of the common vole (Microtus arvalis) provides an excellent model system to study the consequences of restricted gene flow and small population sizes for isolated populations. Here we describe the isolation and characteristics of 10 autosomal and one X-linked microsatellite marker. These new markers were tested in 24 voles from a natural population in eastern Germany. Loci were highly polymorphic with numbers of alleles per locus ranging from three to 26 and expected heterozygosities from 0.51 to 0.97. All loci except for the X-linked locus Mar105 followed Hardy–Weinberg expectations. Cross-species amplifications revealed that most loci were polymorphic as well in M. agrestis, M. thomasi, and M. pennsylvanicus.     

Isolation and characterization of 16 polymorphic microsatellite loci in the endemic Hawaiian damselfly Megalagrion xanthomelas (Odonata: Coenagrionidae)

Microsatellite loci have been isolated from two species of endemic Hawaiian damselflies, Megalagrion xanthomelas and M. eudytum, that are of conservation concern. Sixteen polymorphic loci were characterized in 32 M. xanthomelas from one population on Molokai and one on Hawaii Island. The total number of alleles per locus ranged from two to 16 and observed population heterozygosity ranged from 0.0 to 0.963. Eleven of these loci amplified successfully in M. eudytum as well. These loci will be used to further conservation efforts and infer genetic consequences of Pleistocene glaciations.     

PERMANENT GENETIC RESOURCES: Characterization of eight microsatellite loci in the woolly mouse opossum, Micoureus paraguayanus, isolated from Micoureus demerarae

Eight novel microsatellite markers were isolated from the woolly mouse opossum from the Amazon Forest in Peru, Micoureus demerarae, using a partial genomic DNA library and an enrichment protocol. These loci were polymorphic in M. demerarae and Micoureus paraguayanus populations from the Atlantic Forest in Brazil with the number of alleles ranging from two to 23. Those eight loci plus another five already described for M. paraguayanus will allow for the evaluation of genetic diversity of populations from the 'Rio Doce' Park, one of the last Atlantic Forest fragments in Minas Gerais state, Brazil.     

Isolation and characterization of 15 microsatellite loci from mango (Mangifera indica L.) and cross‐species amplification in closely related taxa

We report here on the development and characterization of 15 microsatellite loci isolated from Mangifera indica L. These markers were evaluated using 59 Florida cultivars and four related species from the USDA germplasm collection for mango. Two loci were monomorphic and 13 polymorphic, with two to seven alleles per locus. Four loci departed significantly from Hardy–Weinberg equilibrium and have significant heterozygote deficiency. Nine loci exhibited significant linkage disequilibrium. Cross‐species amplification was successful in four related species. These loci are being used to investigate patterns of genetic variation within M. indica and between closely related species.     

Effect of temperature and photoperiod on diapause development in a Douglas fir seed chalcid, Megastigmus spermotrophus

Douglas fir seeds infested by diapausing larvae of a chalcid, Megastigmus spermotrophus, were transferred under different temperature and photoperiod regimes at various dates during autumn and winter. Both winter diapause and prolonged diapause were compared to the diapause patterns observed in control lots kept under natural conditions. The results showed that exposure to low temperatures in autumn and winter is required for the completion of diapause development. Median adult emergence dates and the date of transfer of larvae to 20°C were negatively correlated. The frequency of prolonged diapause of larvae transferred to 20°C decreased significantly after November. When larvae were submitted to different constant temperatures, the longer the daylength, the higher and faster the reactivation. These results suggest that chalcid larvae can perceive daylength through the seed coat. This phenomenon is probably related to the fact that most of the infested seeds falling in autumn are usually covered by a layer of leaf litter during the winter. Received: 14 June 1996 / Accepted: 24 February 1997     

Isolation and characterization of microsatellite markers from the entomopathogenic fungus Metarhizium anisopliae

Fourteen polymorphic microsatellite markers were isolated from the entomopathogenic fungus, Metarhizium anisopliae, based on enriched genomic libraries. In order to assess allelic variability, the microsatellite loci were analysed in a collection of 34 isolates sampled from across Switzerland. The number of detected alleles in 14 loci ranged from two to eight and expected heterozygosity from 0.265 to 0.808. Because of the high expected heterozygosity, the 14 microsatellite loci are very useful for ecological studies and analysis of population diversity, and to identifying, monitoring, and tracking M. anisopliae strains applied as biological control agents.     

A multiplex panel of microsatellite markers for widespread sub‐Saharan rodents of the genus Mastomys

We isolated and characterized 12 polymorphic microsatellite loci in the sub‐Saharan rodent Mastomys huberti. We tested cross‐species amplification of all these loci in three closely related Mastomys species: M. coucha, M. erythroleucus and M. natalensis. Multiplex panels comprising 11 loci were developed and their application to a set of individuals in each species allowed clear and easy characterization of allele sizes. Statistics from 31 M. huberti coming from one locality in Mali showed no deviation from Hardy–Weinberg equilibrium except for one locus, and no significant linkage disequilibria between loci.     

Trinucleotide Microsatellite Loci and Increased Heterozygosity in Cross-Species Applications in the Social Wasp, Polistes

Though microsatellite loci are usually found to be most polymorphic in the species in which they are first identified, we have found significant increases in polymorphisms in some cross-species applications. We present eight new trinucleotide microsatellite loci derived from two species of social wasps, Polistes annularis and Polistes bellicosus. We assessed the primers designed from these species and the degree of polymorphism in two additional species, P. dorsalis, which is very closely related to P. bellicosus, and P. dominulus, which is an Old World congener, thought to have diverged from New World Polistes over 80 million years ago. Cross-species applications for these microsatellite loci indicate that the priming sites from P. bellicosus loci are conserved in P. dorsalis and amplified similarly sized products with higher heterozygosities than the original species in two of three cases. A locus that was monomorphic in P. annularis had a heterozygosity of 1.0 in the distantly related P. dominulus. Cross-species applications of these loci indicated that alleles were generally of similar lengths in the new and original species when they retained their heterozygosity.     

Tracing the geographical origin of Megastigmus transvaalensis (Hymenoptera: Torymidae): an African wasp feeding on a South American plant in North America

Determining the geographical origin of an introduced organism can be critical to understanding or managing a non-native species, but is often difficult when the organism is small or inconspicuous. We used a phylogeographical approach to identify the region of endemism and determine the geographical origin of world populations of the seed-feeding wasp Megastigmus transvaalensis (Hussey). This wasp feeds on African Rhus species and South American Schinus species in various locations around the world. Because it is present both in Africa and in South America, it is unclear whether the wasp was originally an African Rhus-feeder that has begun feeding on Schinus or a South American Schinus-feeder that has started feeding on Rhus. Phylogenetic analysis of 800 bp of mitochondrial cytochrome oxidase I sequence data found extensive variation and phylogeographical structure within African M. transvaalensis. Specimens from other locations around the world were all identical in COI sequence and were phylogenetically nested within the African samples. We conclude that M. transvaalensis was originally an African Rhus-feeder that readily attacks Schinus. We evaluate potential pathways of introduction of this wasp to the New World, and we discuss implications of our results for biocontrol efforts against invasive Schinus populations.     

New microsatellite loci isolated from the field cricket Gryllus bimaculatus characterized in two cricket species, Gryllus bimaculatus and Gryllus campestris

We have developed a new set of 27 polymorphic markers for each of two cricket species, Gryllus bimaculatus and Gryllus campestris. Initially, 14 published G. bimaculatus loci were tested in G. campestris; however, only five loci were polymorphic. Therefore, we isolated an additional 50 new microsatellite loci from G. bimaculatus and tested these in both species. In a minimum of 20 individuals, 27 of the new loci were polymorphic in G. bimaculatus and 25 in G. campestris.     

An electrophoretic and morphological analysis of Labiostrongylus (Labiosimplex) bancrofti (Johnston & Mawson, 1939) (Nematoda: Cloacinidae), from macropodid marsupials,with the description of two new species

Allozyme electrophoresis was used to compare specimens of Labiostrongylus (Labiosimplex) bancrofti from two species of Australian macropodids, Macropus dorsalis and M. parryi, with a related species, L. (Labiomultiplex) uncinatus which also infests M. dorsalis. Each nematode was characterised genetically at 18 enzyme loci. The level of fixed genetic differences detected between L. (Ls.) bancrofti from M. parryi and M. dorsalis (83%) is equivalent to that when each is compared to the morphologically distinct species L. (Lm.) uncinatus (89–94%), demonstrating unequivocally that the taxon L. (Ls.) bancrofti represents at least two species, one in M. parryi and one in M. dorsalis. In addition, morphological evidence from additional specimens collected from M. parryi suggested the existence of a third sibling species in this group. All three species differ in the shape of the spicule tips; L. (Ls.) bancrofti has longer spicules than either of the two new species. L. (Ls.) quasibancrofti n. sp. has smaller cephalic papillae, larger oesophago-intestinal diverticula, a larger genital cone and a longer female tail than L. (Ls.) turnbulli n. sp. The taxon L. (Ls.) bancrofti consists, therefore, of three species, L. (Ls.) turnbulli in M. parryi, L. (Ls.) quasibancrofti in M. dorsalis, and L. (Ls.) bancrofti found in both host species, as well as in four species of rock wallabies.     

Microsatellite markers for the fungal banana pathogens Mycosphaerella fijiensis, Mycosphaerella musicola and Mycosphaerella eumusae

We developed a total of 50 microsatellite markers for the three fungal pathogens causing the most important leaf spot diseases of banana: 32 loci for Mycosphaerella fijiensis are presented, and nine loci each for Mycosphaerella musicola and Mycosphaerella eumusae. All these loci were polymorphic within each species on a sample of isolates collected from various locations around the world. Within M. fijiensis and M. musicola, most of the loci tested (> 80%) in a sample of isolates from a single location in Cameroon were also polymorphic. Multiplex polymerase chain reaction systems were developed with 15 loci for M. fijiensis.