Is selection of host plants by Plagiodera versicolora based on plant‐related performance?

Plant-related performance may be one of the most important factors in the selection of host plants by insect herbivores. We investigated the importance of plant-related performance in host selection by the willow leaf beetle, Plagiodera versicolora (Laicharting) (Coleoptera: Chrysomelidae), on four willow species: Salix chaenomeloides Kimura, Salix eriocarpa Fr. et Sav., Salix   integra Thunb., and Salix serissaefolia Kimura (Salicaceae). Bagging experiments in the field revealed that the performance of P. versicolora adults and larvae differed significantly among willow species under enemy-free conditions and at constant densities. Egg clutch and larval abundance were positively related to adult abundance. Plagiodera versicolora adults did not discriminate strongly among willow species for feeding and oviposition. Larval performance did not differ among willow species in the presence of natural enemies, suggesting that interspecific differences in host quality were overridden by mortality from natural enemies. Adult and egg clutch abundance of P. versicolora changed seasonally despite the temporal stability of adult and larval performance under enemy-free field conditions. Thus, plant-related performance of P. versicolora adults and larvae may contribute little to population growth and temporal dynamics of host use in P. versicolora . Potential factors that reduce discrimination of P. versicolora among host willow species are discussed.     

Differential herbivory of the specialist beetle Stolas punicea on chemical phenotypes of its host Mikania micrantha

We assessed the preference of two populations of the specialist beetle Stolas punicea, on plants from three phytochemically differentiated geographical mosaics of the American weed Mikania micrantha. Our results show a significant geographic variation in host preference in S. punicea that could affect its success as a biocontrol agent.     

Plant volatiles moderate response to aggregation pheromone in Colorado potato beetle

Abstract:  The orientation of the Colorado potato beetle, Leptinotarsa decemlineata , to a male-produced aggregation pheromone, ( S )-3,7-dimethyl-2-oxo-oct-6-ene-1,3-diol, a three-component plant attractant blend [comprised of ( Z )-3-hexenyl acetate + (±)-linalool + methyl salicylate], and other potato volatiles (nonanal and 2-phenylethanol) were tested. All compounds were previously shown to be active in coupled gas chromatography/electroantennogram experiments. Both the three-component plant attractant blend and 2-phenylethanol were attractive to adult beetles. While male beetles oriented preferentially to both plant attractants vs. a control, females showed little preference. Combining the plant attractants with the pheromone resulted in sexually dimorphic responses similar to those seen with either plant attractant alone. Addition of nonanal abolished the sexually dimorphic response to the pheromone + 2-phenylethanol blend; the new three-component blend was attractive to both sexes. In both laboratory bioassays and field experiments, a combination of the pheromone + the three-component plant attractant was preferred over the plant attractant alone. Thus, it seems likely that combinations of pheromone + plant volatiles may be the most efficacious for field use.     

植食性昆虫取食行为过程及机制研究

昆虫取食行为包括定向、趋性、辨认、取食等一系列的活动,涉及复杂的行为生理过程,如视觉、嗅觉、味觉感受及神经调控等。昆虫取食行为不仅受外界物理环境因素、寄主植物化学成份影响,而且跟昆虫自身生理状态紧密相关。本文综述了昆虫取食过程、寄主定位的感受机制、神经肽调节机制、影响取食的理化因素、环境因素等方面的研究进展,旨在为深入研究昆虫与环境关系、开发害虫取食行为调控新技术提供参考。     

A test of the sympatric host race formation hypothesis in Neodiprion (Hymenoptera: Diprionidae)

Theory suggests that sympatric speciation is possible; however, its prevalence in nature remains unknown. Because Neodiprion sawflies are host specialists and mate on their hosts, sympatric speciation via host shifts may be common in this genus. Here, we test this hypothesis using near-complete taxonomic sampling of a species group, comprehensive geographical and ecological data, and multiple comparative methods. Host-use data suggest that host shifts contributed to the evolution of reproductive isolation in Neodiprion and previous work has shown that gene flow accompanied divergence. However, geographical data provide surprisingly little support for the hypothesis that host shifts occurred in sympatry. While these data do not rule out sympatric host race formation in Neodiprion, they suggest that this speciation mode is uncommon in the genus and possibly in nature.     

GENETIC CONSTRAINTS AND THE PHYLOGENY OF INSECT-PLANT ASSOCIATIONS: RESPONSES OF OPHRAELLA COMMUNA (COLEOPTERA: CHRYSOMELIDAE) TO HOST PLANTS OF ITS CONGENERS

We ask whether patterns of genetic variation in a phytophagous insect's responses to potential host plants shed light on the phylogenetic history of host association. Ophraella communa feeds chiefly, and in eastern North America exclusively, on Ambrosia (Asteraceae: Ambrosiinae). Using mostly half-sib breeding designs, we screened for genetic variation in feeding responses to and larval survival on its own host and on seven other plants that are hosts (or, on one case, closely related to the host) of other species of Ophraella. We found evidence for genetic variation in feeding responses to five of the seven test plants, other than the natural host. We found no evidence of genetic variation in feeding responses to two plant species, nor in capacity for larval survival on six. These results imply constraints on the availability of genetic variation; however, little evidence for constraints in the form of negative genetic correlations was found. These results are interpreted in the context of a provisional phylogeny of, and a history of host shifts within, the genus. Ophraella communa does not present evidence of genetic variation in its ability to feed and/or survive on Solidago, even though it is probably descended from a lineage that fed on Solidago or related plants, possibly as recently as 1.9 million years ago. Genetic variation in performance on this plant may have been lost. Based on evidence for genetic variation and on mean performance, by far the greatest potentiality for adaptation to a congener's host was evinced in responses to Iva frutescens, which not only is related and chemically similar to Ambrosia, but also is the host of a closely related species of Ophraella that may have been derived from an Ambrosia-associated ancestor. Genetic variation in O. communa's capacity to feed and/or survive on its congeners' hosts is less evident for plants that do not represent historically realized host shifts (with one exception) than for those that may (but see Note Added in Proof). The results offer some support for the hypothesis that the evolution of host shifts has been guided in part by constrained genetic variation.