Wen-Zhu Li

A Second New Species of Ice Crawlers from China (Insecta: Grylloblattodea), with Thorax Evolution and the Prediction of Potential Distribution

Modern grylloblattids are one of the least diverse of the modern insect orders. The thorax changes in morphology might be associated with the changes of the function of the forelegs, wing loss, changes in behavior and adaptation to habitat. As temperature is the main barrier for migration of modern grylloblattids, the range of each species is extremely limited. The potential distribution areas of grylloblattids remain unclear. A second new species of ice crawlers (Insecta: Grylloblattodea), Grylloblattella cheni Bai, Wang et Yang sp. nov., is described from China. The distribution map and key to species of Grylloblattella are given. A comparison of the thorax of extant and extinct Grylloblattodea is presented, with an emphasis on the pronotum using geometric morphometric analysis, which may reflect thorax adaptation and the evolution of Grylloblattodea. Potential global distribution of grylloblattids is inferred. Highly diversified pronota of extinct Grylloblattodea may reflect diverse habitats and niches. The relatively homogeneous pronota of modern grylloblattids might be explained by two hypotheses: synapomorphy or convergent evolution. Most fossils of Grylloblattodea contain an obviously longer meso- and metathorax than prothorax. The length of the meso- and metathorax of modern grylloblattids is normally shorter than the prothorax. This may be associated with the wing loss, which is accompanied by muscle reduction and changes to the thoracic skeleton system. Threats to grylloblattids and several conservation comments are also provided.

Male mate recognition via cuticular hydrocarbons facilitates sexual isolation between sympatric leaf beetle sister species

Chemical signals in insects have been documented to play an important role in mate recognition, and divergence in chemical signals can often cause sexual isolation between closely related species or populations within species. We investigated the role of cuticular hydrocarbons (CHCs), short distance chemical signals, in male mate recognition between the two sympatric elm leaf beetles, Pyrrhalta maculicollis and Pyrrhaltaaenescens. Mating experiments demonstrated that strong sexual isolation between the two species was driven by CHCs divergence. Males preferred to mate with conspecific females with intact conspecific CHCs or conspecific CHCs reapplied after removal. Males also preferred heterospecific females that were treated with conspecific CHCs. Chemical analysis showed that the CHC profiles differ significantly between species. In P. maculicollis dimethyl-branched alkanes between C29 and C35 account for the majority of the saturated alkanes while the CHC profile of P. aenescens mostly consisted of monomethyl-branched alkanes between C22 and C29. Additionally, some compounds, such as 12,18-diMeC32, 12,18-diMeC34, are unique to P. maculicollis.

Post-Pleistocene demographic history of the North Atlantic endemic Irish moss Chondrus crispus: glacial survival, spatial expansion and gene flow

Range expansions and gene flow as micro‐evolutionary processes played a leading role in the population demographic history of marine organisms. Herein, we sequenced partial mtDNA Cox1 gene from 26 assigned geographical populations to understand how Irish moss (Chondrus crispus) responded to severe climatic oscillations during the Pleistocene glaciations and contemporary forces such as gene flow. Phylogeographic patterns indicated that haplotype frequency distributions were strongly skewed, with nearly half found only in single samples and thus restricted to a single population. Analysis of molecular variance revealed that most of the variation was within populations with no significant genetic structuring on either side of the Atlantic. Demographic analyses indicated that ISI (Irish Sea and Ireland) and NS (the North Sea) areas experienced a slight trend of increase in population size over time, whereas EC (the English Channel) area experienced expansion beginning approximately 170 000–360 000 BP. The observed complex genetic pattern of C. crispus is consistent with a scenario of multiple unrelated founding events by survival of this species in at least three putative Pleistocene refugia along the European coastline, and subsequent trans‐Atlantic dispersal combined with contiguous northward population expansion predating the LGM and geographically gene flow.

Reproductive barriers between two sympatric beetle species specialized on different host plants

Knowledge on interspecific pre‐ and post‐zygotic isolation mechanisms provides insights into speciation patterns. Using crosses (F1 and backcrosses) of two closely related flea beetles species, Altica fragariae and A. viridicyanea, specialized on different hosts in sympatry, we measured: (a) the type of reproductive isolation and (b) the inheritance mode of preference and host‐specific performance, using a joint‐scaling test. Each species preferred almost exclusively its host plant, creating strong prezygotic isolation between them, and suggesting that speciation may occur at least partly in sympatry. Reproductive isolation was intrinsic between females of A. fragariae and either A. viridicyanea or F1 males, whereas the other crosses showed ecologically dependent reproductive isolation, suggesting ecological speciation. The genetic basis of preference and performance was at least partially independent, and several loci coded for preference, which limits the possibility of sympatric speciation. Hence, both ecological and intrinsic factors may contribute to speciation between these species.

Genetic analysis of feeding preference in two related species of Altica (Coleoptera: Chrysomelidae: Alticinae)

Abstract 1. Genetic analysis of feeding preference can make an important contribution to our understanding of the evolution of host‐plant selection in phytophagous insects. Two closely related flea beetles, Altica viridicyanea (Baly) and Altica fragariae Nakane, with separate host plants [Geranium wilfordii Maxim. and Duchesnea indica (Andrews) Focke respectively] were hybridised to analyse the inheritance mode of feeding preference.

Assortative mating between two sympatric closely-related specialists: inferred from molecular phylogenetic analysis and behavioral data

Host plant shifting of phytophagous insects can lead to the formation of host associated differentiation and ultimately speciation. In some cases, host plant specificity alone acts as a nearly complete pre-mating isolating barrier among insect populations. We here test whether effective pre-mating isolation and host-independent behavioral isolation have evolved under the condition of extreme host specilization using two sympatric flea beetles with incomplete post-mating isolation under laboratory conditions. Phylogenetic analysis and coalescent simulation results showed that there is a limited interspecific gene flow, indicating effctive isolation between these species. Three types of mating tests in the absence of host plant cues showed that strong host-independent behavioral isolation has evolved between them. We conclude that almost perfect assortative mating between these two extreme host specialists results from a combination of reduced encounter rates due to differential host preference and strong sexual isolation.

Recent Speciation in Three Closely Related Sympatric Specialists: Inferences Using Multi-Locus Sequence, Post-Mating Isolation and Endosymbiont Data

Shifting between unrelated host plants is relatively rare for phytophagous insects, and distinct host specificity may play crucial roles in reproductive isolation. However, the isolation status and the relationship between parental divergence and post-mating isolation among closely related sympatric specialists are still poorly understood. Here, multi-locus sequence were used to estimate the relationship among three host plant–specific closely related flea beetles, Altica cirsicola, A. fragariae and A. viridicyanea (abbreviated as AC, AF and AV respectively). The tree topologies were inconsistent using different gene or different combinations of gene fragments. The relationship of AF+(AC+AV) was supported, however, by both gene tree and species tree based on concatenated data. Post-mating reproductive data on the results of crossing these three species are best interpreted in the light of a well established phylogeny. Nuclear-induced but not Wolbachia-induced unidirectional cytoplasmic incompatibility, which was detected in AC-AF and AF-AV but not in AC-AV, may also suggest more close genetic affinity between AC and AV. Prevalence of Wolbachia in these three beetles, and the endosymbiont in most individuals of AV and AC sharing a same wsp haplotype may give another evidence of AF+(AC+AV). Our study also suggested that these three flea beetles diverged in a relative short time (0.94 My), which may be the result of shifting between unrelated host plants and distinct host specificity. Incomplete post-mating isolation while almost complete lineage sorting indicated that effective pre-mating isolation among these three species should have evolved.

Study of Phygasia (Coleoptera: Chrysomelidae) from China, with descriptions of eight new species

Eight new species of Phygasia Chevrolat (Coleoptera: Chrysomelidae) are described from China, P. gracilicornis, P. nigricollis, P. parva, P. pseudomedia, P. pseudornata, P. simidorsata, P. suturalis and P. yunnana. A list and a key with distribution records to the 21 Chinese species of Phygasia are provided. Antennae, male and female genitalia of most species are illustrated. P. wittmeri Medvedev and P. potanini Medvedev are proposed as new synonyms of P. diancangana Wang and P. potanini Lopatin, respectively. P. pallidipennis Medvedev, 2004 is the homonym of P. pallidipennis Chen et Wang, 1980.

Endogenous cellulolytic enzyme systems in the longhorn beetle Mesosa myops (Insecta: Coleoptera) studied by transcriptomic analysis

The Cerambycidae (longhorn beetle) is a large family of Coleoptera with xylophagous feeding habits. Cellulose digestion plays an important role in these wood-feeding insects. In this study, transcriptomic technology was used to obtain one glycoside hydrolase family 45 (GH45) cellulase and seven GH5 cellulases from Mesosa myops, a typical longhorn beetle. Analyses of expression dynamics and evolutionary relationships provided a complete description of the cellulolytic system. The expression dynamics related to individual development indicated that endogenous GH45 and GH5 cellulases dominate cellulose digestion in M. myops. Evolutionary analyses suggested that GH45 cellulase gene is a general gene in the Coleoptera Suborder Polyphaga. Evolutionary analyses also indicated that the GH5 cellulase group in Lamiinae longhorn beetles is closely associated with wood feeding. This study demonstrated that there is a complex endogenous cellulolytic system in M. myops that is dominated by cellulases belonging to two glycoside hydrolase families.

Your chemical coat tells me you are my delicacy: a predatory stink bug uses cuticular hydrocarbons to identify prey

Extensive studies have shown that cuticular hydrocarbons (CHCs) are among the major cues that allow many insects to identify interspecific and intraspecific variation between individuals. CHCs often have mutually nonexclusive functions that can provide multiple types of signals, while their role in predator–prey interactions has received little attention. Here, we used a predatory stink bug, Zicrona caerulea (Hemiptera: Pentatomidae), and one of its favorite flea beetle prey, Altica viridicyanea (Coleoptera: Chrysomelidae), to test the hypothesis that CHCs of prey are important chemical cues for a predator. Two-choice bioassays using dead beetles and glass dummies clearly indicated that the CHC profile of A. viridicyanea is the pivotal cue in prey identification for Z. caerulea. The results also suggested that the role of acoustic and visual cues can be ignored in prey recognition at close range.