A comparison of genetic variation in two sibling species pairs of haplodiploid insects

Sibling species pairs of sweat bees (Halictus confusus andH. tumulorum) and pine sawflies (Neodiprion pratti andN. maurus) were surveyed for genetic variability using enzyme electrophoresis. Levels of heterozygosity were found to be within the ranges earlier recorded for Hymenoptera. Expected heterozygosities were not significantly higher in the sawflies than in the sweat bees. Estimates of genetic identity between the sibling species were not lower than those generally found for diplodiploid insect species: no evidence was found for an increased rate of evolution in these haplodiploids. Genetic identity data among populations ofH. confusus and betweenHalictus species were within the range expected for conspecific populations and sibling species, respectively. InNeodiprion all genetic distances were low but the two populations ofN. pratti had similar genetic distances as each did toN. maurus, indicating the necessity for further systematic studies of the genus. The research reported here was supported by NSERC operating grants to the junior author. Collections of samples were made through NSERC funding previously available to Drs. R. E. Owen and G. Knerer, L. R. was supported by an Internationaliserringsstipendium from the University of Copenhagen, and L. P. by an NSERC University Research Fellowship.     

Functional and evolutionary aspects of mouthpart structure in parasitoid wasps

This paper considers specializations in mouthpart structure among parasitoid wasps. I commence with a brief survey of mouthpart specializations (mostly involving the mandibles only) that serve functions other than feeding: facilitating emergence of the parasitoid adult from its place of pupation; facilitating grasping of the partner in mating (phoretic copulation); facilitating excavation and/or protecting vulnerable mouthpart components during host searching; facilitating handling of the host; and facilitating nest excavation and construction. I then consider in detail mouthpart specializations for feeding (mostly involving the labiomaxillary complex), and place them in an evolutionary context. Whereas the digitate labrum of Perilampidae and Eucharitidae and the stoudy setose labrum of chrysolampine Pteromalidae are purported to be devices for filtering pollen grains from nectar, I conclude that they are not a feeding-related specialization whatsoever. I recognize seven functional types of mouthpart specialization relating to the extraction of floral nectar from long, narrow, tubular corollas (‘concealed nectar extraction apparatus’ [CNEA]) (Braconidae, Ichneumonidae, Leucospidae, Chrysididae), and postulate a transformation series for them. An eighth type of CNEA possibly occurs in Scoliidae. No such specializations occur in either Orussoidea, Trigonalyoidea, Megalyroidea, parasitoid Evanioidea, Stephanoidea, Cynipoidea, Proctotrupoidea, Ceraphonoidea or parasitoid Aculeata other than Chrysididae and Pompilidae. From examination of published cladograms I conclude that the evolution of CNEA has occurred several times independendy within the parasitoid Hymenoptera. So far as Ichneumonoidea are concerned, possession of CNEA is an autapomorphy for taxa at least below subfamily level. Possession of CNEA appears to be a synapomorphy for the family Leucospidae (Chalcidoidea) as a whole, and the same applies to the subfamily Parnopinae (Chrysididae). Hitherto not noted in the literature is the strong degree of evolutionary parallelism, with respect to CNEAs, between the Ichneumonoidea (Ichneumonidae, Braconidae) and the Aculeata (Chrysididae, Pompilidae, Vespidae [Vespinae, Masarinae, Eumeminae], Apidae, non-parasitoid Sphecidae). Also, Apocrita and Symphyta have two types of CNEA in common. Functional comparisons are made between the CNEAs of the parasitoids and those of other Hymenoptera. Compared to parasitoid flies, very few parasitoid wasps possess CNEA. Mouthpart specialization for conveying a nuptial gift of nectar or honeydew to the female occurs in the males of thynnine Tiphidae, while in the females of regurgitation feeders there is a trend towards reduction in labiomaxillary components, constituting a specialization for receiving and processing the gift. Mouthpart specialization for pollen feeding occurs in Mutillidae and Scoliidae. No mouthpart specialization for host feeding occurs in any parasitoid wasps, in contrast to parasitoid flies, despite host feeding being more common among the former. Sexual dimorphism in feeding-related mouthpart specializations is rare among parasitoid wasps; where it occurs, both sexes share the same type of CNEA, and the dimorphism is attributable to allometry.     

Host stress influences oviposition preference and performance of a pine sawfly

Abstract.

• 1 The effect of ponderosa pine (Pinus ponderosa Doug]. ex Laws) water stress, measured by xylem water potential, on oviposition preference and egg development of Neodiprion fulviceps was determined by two laboratory experiments in 1987 and 1988.
• 2 In the first experiment, adult females were allowed to choose between foliage from water-stressed, watered, and untreated control trees.
• 3 Significant differences were found between treatments in xylem water potential in 1987 but not in 1988.
• 4 Females chose water-stressed trees and a positive correlation was found between female preference and xylem water potential in 1987 but not in 1988.
• 5 In the second experiment, females were placed in globe cages with a single branch from each treatment and allowed to oviposit.
• 6 Significant differences were found among treatments in egg survival in 1987 but not in 1988.
• 7 These results indicate that sawflies can distinguish between stressed and non-stressed trees and that this behaviour is adaptive in that egg survival was greatest on the preferred treatment.

     

EVOLUTION OF DIFFERENT GALL TYPES IN WILLOW-FEEDING SAWFLIES (HYMENOPTERA: TENTHREDINIDAE)

The sawflies that feed on the plant family Salicaceae can be divided into eight informal groups based on larval feeding habit or gall type: (1) species with free-living larvae; (2) leaf folders; (3) leaf blade gallers; (4) apical leaf gallers; (5) basal leaf gallers; (6) midrib and petiole gallers; (7) stem gallers; and (8) bud gallers. It has been proposed that the galling habit evolved from free-living larvae via leaf folders, and that the different gall types evolved gradually in the sequence mentioned above. Thus, the galling site would have “wandered” from the leaf margin toward the stem as a result of gradual changes in oviposition site preference. Allozyme data from eight informative loci were used to reconstruct the phylogeny of 18 representative sawfly species. The results suggest that indeed leaf folders seem to be a basal group; leaf blade gallers evolved independently of the other true gallers; apical and basal leaf gallers are not the ancestors of petiole and bud gallers, but they may share a common galling ancestor; bud gallers evolved from midrib/petiole gallers; and stem gallers are polyphyletic. The cause for the observed wandering of the galling site could be intraspecific competition due to a possible “nutrient shading effect” of galls situated closer to the host plant's main vascular system.     

Bracken, ants and extrafloral nectaries. III. How insect herbivores avoid ant predation

Abstract. 1. Ants (Myrmica spp. and Formica lemani) visiting the extrafloral nectaries of bracken, Pteridium aquilinum, imposed heavy mortality on caterpillars of a novel moth species experimentally introduced onto bracken fronds. However, the exclusion of ants from bracken fronds had no significant effect on adapted bracken-feeding herbivores in Britain.
2. The feeding stages of British bracken-feeding insects are immune to, or can largely avoid, predation by ants in a variety of ways. Gall formers and miners cannot be attacked by these ants. Two other species hide, one inside tied leaves, the other in a mass of 'spittle'. Another group of species jumps away from, or falls off the plant when touched by ants. Sawfly caterpillars in the genera Strongylogaster, Aneugmenus and Tenthredo have viscous, distasteful haemolymph that repels ants.
3. No species of bracken herbivore has an absolute temporal refuge from ants; during their development they all overlap with ants to some degree.
4. Ant predation appears to have played a significant role in determining the contemporary structure of British bracken-feeding insect communities. Distasteful haemolymph in sawfly caterpillars may have evolved in response to selection from ant predation. Other species may fortuitously possess characteristics, evolved in response to a variety of selective forces, that also reduce the impact of ants; without such characteristics, however, we postulate that they would be unable to live on this plant. An absence of external, foliage feeding Lepidoptera early in the spring, a high proportion of sawfly species, and a high proportion of gall-formers and miners may all be characteristics of the bracken herbivore community which have been influenced by ant predation.     

中国细锤角叶蜂属格氏细锤角叶蜂Leptocimbex grahami种团二新种（膜翅目：锤角叶蜂科）

记述采自中国浙江天目山与湖北神农架的细锤角叶蜂属格氏细锤角叶蜂种团Leptocimbex grahami group 2新种:黑毛细锤角叶蜂L.nigropilosus Yan&Wei sp.nov.和神农架细锤角叶蜂L.shennongjiaensis Yan,Wei&Deng sp.nov.;总结了格氏细锤角叶蜂种团各已知种的特征及关系,并提供了分种检索表.     

Differences in host plant selection among three Athalia sawflies feeding on crucifers in Japan

Abstract 1. The ways of using host plants were compared among the three Athalia sawflies [ A. japonica (Klug), A. rosae ruficornis Jakovlev, and A. infumata (Marlatt)] feeding on crucifers in Japan to determine whether host specialisation can explain the difference in their life-history traits. The occurrence of their larvae was examined on each crucifer species in the field, and the suitability of each crucifer species for the three successive steps of host use by the sawflies was evaluated: microhabitat selection by adult females, female oviposition, and larval growth.
2. There were 11 species of crucifer in the study area, and A. japonica , A. rosae , and A. infumata used nine, seven, and eight species respectively. Thus, sawfly host ranges overlapped.
3. Adult females of A. japonica , A. rosae , and A. infumata preferred shady clumps of crucifers, sunny clumps of crucifers, and disturbed areas respectively.
4. Unsuitable hosts for larval performance such as Brassica oleracea and Arabis plants were eliminated from the host ranges of the three sawflies.
5. Once they chose microhabitats, the suitability of each host plant for female oviposition and larval growth was similar.
6. Because of the divergent preferences for microhabitats, the host plants that were suitable for all the three steps were restricted to different sets of plants among the sawflies: Cardamine for A. japonica , cultivated crucifers ( Raphanus and Brassica ) for A. rosae , and Rorippa for A. infumata . These plants could be recognised as the respective primary host plants.
7. The spatio-temporal distributions of primary hosts were consistent with and explained the pattern of diapause and migration of each sawfly, suggesting that host specialisation caused their life-history traits to differentiate.     

Identification of sawflies and horntails (Hymenoptera, ‘Symphyta’) through DNA barcodes: successes and caveats

The ‘Symphyta’ is a paraphyletic assemblage at the base of the order Hymenoptera, comprising 14 families and about 8750 species. All have phytophagous larvae, except for the Orussidae, which are parasitoids. This study presents and evaluates the results of DNA barcoding of approximately 5360 specimens of ‘Symphyta’, mainly adults, and 4362 sequences covering 1037 species were deemed of suitable quality for inclusion in the analysis. All extant families are represented, except for the Anaxyelidae. The majority of species and specimens are from Europe, but approximately 38% of the species and 13% of the specimens are of non‐European origin. The utility of barcoding for species identification and taxonomy of ‘Symphyta’ is discussed on the basis of examples from each of the included families. A significant level of cryptic species diversity was apparent in many groups. Other attractive applications include the identification of immature stages without the need to rear them, community analyses based on metabarcoding of bulk samples and association of the sexes of adults.