Are galling insects better protected against parasitoids than exposed feeders?: a test using tenthredinid sawflies

ABSTRACT.

• 1 Data mostly from the published literature were used to assess the effect of galling on the number of parasitoid species per host species in the phylogeny of nematine sawflies from free external feeders (colonial and solitary) to leaf gallers and shoot gallers.
• 2 The strongest effects of galling were the total elimination of the species-rich cocoon-attacking guild of parasitoids, and eonymphal parasitoids, from the parasitoid community on shoot gallers, all of which are in the genus Euura.
• 3 All tachinid larval parasitoids were also eliminated by the galling habit.
• 4 The cumulative effects of these exclusions resulted in a decline in mean number of parasitoid species per host species from almost sixteen species on external colonial feeders to 4.0 species on shoot gallers.
• 5 General patterns in per cent parasitism by non-tachinid and tachinid larval parasitoids, eonymphal and cocoon parasitoids, on exposed feeders to shoot gallers, showed declines in non-tachinid attack and elimination of tachinid, eonymphal and cocoon parasitoids. But leaf gallers tended to be attacked more than exposed feeders by non-tachinid larval parasitoids.
• 6 The galling habit had a long-term impact by reducing the number of parasitoid species attacking nematine sawfly gallers and per cent mortality inflicted, so that natural enemies may have been important as a selective factor in the evolution of galling nematine sawflies.

     

Crucial factors determining the spatio-temporal distribution patterns of threeAthalia sawflies feeding on common cruciferous plants

Three Athalia sawflies, A. japonica, A. rosae and A. infumata, feeding on cruciferous plants, coexist in Japan. However, it is not known what ecological strategies they use and what environmental factors are crucial to such strategies. I attempted to explain these questions by examining the relationship between the spatio-temporal distribution patterns of three Athalia sawflies and their habitats in three districts (Lowland, Intermediate and Mountain). The three sawflies have different spatio-temporal distribution patterns, though they usually used common cruciferous plants. A. japonica was abundant in spring and autumn but disappeared during summer in all the districts. In the Lowland, populations of A. rosae and A. infumata, like that of A. japonica, crashed in summer. However A. rosae occurred mainly in summer in the Intermediate and Mountain. Although A. infumata occurred in the same seasons as A. rosae in all districts, population levels of A. infumata were always lower than those of A. rosae. The crucial factors controlling their population patterns were the availability of host plants and temperature. Population crashes of A. rosae and A. infumata were due to food depletion, and those of A. japonica were due to heat stress. On the other hand, their population patterns may be interpreted as phenological synchronization with their original host plants, though they all existed on common cruciferous plants. The three sawflies may have evolved different strategies to escape from unfavorable habitat conditions. Such strategies are speculated to be summer diapause in A. japonica, long distance migration in A. rosae, and local dispersal in A. infumata.     

Correlation of phenotypes of the apterous mutation in Drosophila melanogaster

The apterous (ap) mutant in Drosophila melanogaster exhibits phenotypes of wing deficiency, precocious adult death, and nonvitellogenic oocyte development. The latter phenotype previously has been shown to result from juvenile hormone (JH) deficiency in the adult stage. To explore the relationship between the hormone deficiency and the other phenotypes, the expression of each phenotype was measured in five alleles of ap (including a new, chemically-induced allele, ap^77f) as wing length, survival five days after eclosion, and initiation and progress of vitellogenic oocyte development. No correlation could be found between severity of wing phenotype and that of precocious adult death or nonvitellogenesis. However, the latter phenotypes were correlated in both ap homozygotes and allelic heterozygotes, since adults that survive have wild-type vitellogenesis, and those fated for precocious death fail to develop vitellogenic oocytes. These results indicate that no relationship exists between wing and JH deficiencies, but that precocious adult death is related to hormone deficiency — probably through pleiotropy, rather than through causality.     

中国钩瓣叶蜂属Macrophya annulitibia种团二新种及分种检索表（膜翅目：叶蜂科）

记述采自中国四川和西藏钩瓣叶蜂属Macrophya Dahlbom环胫钩瓣叶蜂种团M annulitibia group 2新种:凯文钩瓣叶蜂 Macrophya kaiweni Liu,Li&Wei sp.nov.和拟盛氏钩瓣叶蜂 M.pseudoshengi Liu,Li&Wei sp.nov.;提供了 M.annulitibia group中国已知种类检索表和分布图.     

A wingless alpine stonefly from New Zealand,and further information on genus Holcoperla (Plecoptera: Gripopterygidae)

Abstract

Holcoperla magna n.sp. is described and figured from material collected on Headlong Peak, Mt Aspiring National Park. New information is given on H. angularis (Wisely) and H. jacksoni McLellan, and the 3 species are compared. Larvae designated as type specimens of H. angularis are shown to be Apteryoperla monticola Wisely.     

A new species of Macrophya Dahlbom (Hymenoptera: Tenthredinidae) with a key to species of the Macrophya coxalis group from China

A new species, Macrophyra pseudocoxalis Li, Liu & Wei, sp. nov., of the genus Macrophya Dahlbom (Hymenptera: Tenthredinidae) from China is described. A key to known Chinese species of the Macrophya coxalis group is provided. The type specimens of the new species are deposited in the Lishui Academy of Forestry, Lishui, Zhejiang, China.     

Antenna to leg transformation: Dynamics of developmental competence

We explore the transformation of antenna to leg in Drosophila melanogaster, using ectopically expressed transgenes with heat shock promoters: heat shock Antennapedia, heat shock Ultrabithorax, and heat shock mouse Hox A5. We determined the frequency of transformation of several leg markers in response to Antennapedia protein delivered by heat shock at different times and doses. We also studied stage-specific responses to the transgene, heat shock mouse Hox A5. Results show that each marker has its own stage and dose-specific pattern of response. The same marker could pass through a period of high-dose inhibition followed by a dose-independent response and then a positive dose-dependent phase. The heat shock-induced transgenes and spineless aristapedia transformed the apterous enhancer trap antenna disc expression pattern toward the pattern found in leg discs. These results are considered in relation to developmental competence—the ability of developing tissue to respond to internal or external influences. The results suggest that all genes tested interact with the same competence system and that at least two classes of mechanisms are associated with antenna to leg transformation: one comprises global mechanisms that permit transformation over approximately 24 hr; the second class of mechanisms act very locally and are responsible for changes in dose response on the order of 4–8 hr. © 1996 Wiley-Liss, Inc.     

Release of phylogenetic constraints through low resource heterogeneity: the case of gall-inducing sawflies

Abstract. 1. A group of six unusual sawfly species, which do not conform to the phylogenetic constraints hypothesis as it has been applied to sawflies, was examined in natural populations. All species were in the genus Pontania (Hymenoptera: Tenthredinidae), which induce galls on leaves of willow species (Salicaceae). An understanding of these non‐conformist species was important as a test of the validity of the general hypothesis. 2. The six species of sawfly, Pontania mandshurica, P. cf. arcticornis, P. aestiva, P. arcticornis, P. pacifica, and P. nr. pacifica, showed no oviposition preference for long, vigorous shoots, in contrast to 37 documented tenthredinid species that have demonstrated such a preference. Rather, the non‐conformist species attacked the shortest shoot length classes more frequently and larval establishment in galls was successful. 3. The evident escape from the phylogenetic constraint, which commonly limits sawfly attack to the most vigorous shoots in a willow population, resulted from low apparent heterogeneity of the resources exploited by these Pontania species. At the time of female oviposition, shoots and leaves were too uniform to allow discrimination by females among shoot length classes, resulting in random, or near random attack of shoots. 4. The unusual relative uniformity of resources to which sawflies were exposed resulted from several characteristics. (1) Females emerged early relative to shoot growth phenology, making discrimination among shoot length and vigour difficult or impossible. (2) Low heterogeneity in leaf length resulted in resource similarity independent of shoot length. (3) Abscission of leaves occurred after emergence of larvae from leaf galls so that differential abscission of leaves in relation to shoot length became irrelevant. (4) In some cases, low variance in shoot lengths was evident in old ramets lacking long, vigorous shoots. Probably as a result of low resource heterogeneity, larvae survived well across all shoot length classes, revealing no ovipositional preference and larval performance linkage related to the exploitation of the longest shoot length classes in a population of willows, as in the conformist species. Therefore, larval survival did not provide positive feedback on female preferential behaviour for long shoots, as in the conformist species studied.