Can chemical communication be cryptic? Adaptations by herbivores to natural enemies exploiting prey semiochemistry

Predators and parasites commonly use chemical cues associated with herbivore feeding and reproduction to locate prey. However, we currently know little about mechanisms by which herbivores may avoid such natural enemies. Pheromones are crucial to many aspects of herbivore life history, so radical alterations of these compounds could be disadvantageous despite their exploitation by predators. Instead, minor modifications in pheromone chemistry may facilitate partial escape while maintaining intraspecific functionality. We tested this hypothesis using Ips pini, an endophytic beetle that develops in the phloem tissue of pine trees. Its predominant predators in the Great Lakes region of North America are Thanasimus dubius and Platysoma cylindrica, both of which are highly attracted to I. pini’s pheromones. However, there are significant disparities between prey and predator behaviors that relate to nuances of pheromone chemistry. Thanasimus dubius is most attracted to the (+) stereoisomer of ipsdienol, and P. cylindrica is most attracted to the (−) form; Ips pini prefers racemic mixtures intermediate between each predator’s preferences. Further, a component that is inactive by itself, lanierone, greatly synergizes the attraction of I. pini to ipsdienol, but has a weak or no effect on its predators. A temporal component adds to this behavioral disparity: lanierone is most important in the communication of I. pini during periods when its predators are most abundant. The difficulties involved in tracking prey are further compounded by spatial and temporal variation in prey signaling on a local scale. For example, the preferences of I. pini vary significantly among sites only 50 km apart. This chemical crypsis is analogous to morphological forms of camouflage, such as color and mimicry, that are widely recognized as evasive adaptations against visually searching predators. Presumably these relationships are dynamic, with predators and prey shifting responses in microevolutionary time. However, several factors may delay predator counter adaptations. The most important appears to be the availability of alternate prey, specifically I. grandicollis, whose pheromone ipsenol is highly attractive to the above predators but not cross-attractive with I. pini. Consistent with this view, the specialist parasitoid, Tomicobia tibialis, has behavioral preferences for pheromone components that closely correspond with those of I. pini. These results are discussed in terms of population dynamics and coevolutionary theory. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Electrophysiological identification of the sugar cell in antennal taste sensilla of the predatory ground beetle Pterostichus aethiops

By single sensillum tip recording technique, in addition to the salt and pH cells found in antennal taste sensilla of some ground beetles earlier, the third chemosensory cell of four innervating these large sensilla was electrophysiologically identified as a sugar cell in the ground beetle Pterostichus aethiops. This cell generated action potentials of considerably smaller amplitude than those of the salt and pH cells, and phasic-tonically responded to sucrose and glucose over the range of 1-1000 mM tested. Responses were concentration dependent, with sucrose generating more spikes than glucose. During the first second of the response, maximum rates of firing of the sugar cell reached up to 19 and 37 imp/s when stimulated with 1000 mM glucose and sucrose, respectively. Three to four seconds later, the responses decreased close to zero. Both sugars are important in plant carbohydrate metabolism. These ground dwelling insects may come into contact with live and decayed plant material everywhere in their habitat including their preferred overwintering sites in brown-rot decayed wood. In conclusion, we hypothesize that high content of soluble sugars in their overwintering sites and refugia is unfavourable for these ground beetles, most probably to avoid contact with dangerous fungi.     

干旱胁迫下胡杨茎流日变化分析——以塔里木河下游英苏断面为例

用PHYTALK植物生理生态监测系统对塔里木河下游英苏断面胡杨的茎流和相关环境因子的日变化进行了监测.结果表明:在极端干旱区塔里木河下游的胡杨茎流日变化表现多峰值,且夜晚仍保持一定流速;主枝与侧枝茎流日变化趋势相似,主枝流速高于侧枝;侧枝对环境变化响应更加灵敏,波动强烈,主枝相对侧枝,茎流变化响应迟钝且有明显滞后效应;茎流变化受太阳辐射、风速和大气温度影响明显,而其它环境因子如空气湿度、土壤湿度等影响则不大,气温与叶温表现出极佳相关性,气温与空气湿度呈显著负相关;同时,日变化中,不同时段起主导作用的因子不尽相同.     

Foliar Extrafloral Nectar of Humboldtia brunonis (Fabaceae), a Paleotropic Ant‐plant,is Richer than Phloem Sap and More Attractive than Honeydew

The ant‐plant Humboldtia brunonis secretes extrafloral nectar (EFN) despite the lack of antiherbivore protection from most ants. EFN was richer in composition than phloem sap and honeydew from untended Hemiptera on the plant, suggesting that EFN could potentially distract ants from honeydew, since ants rarely tended Hemiptera on this plant.     

Phylogenetic reassessment and biogeography of the Ectateus generic group (Coleoptera: Tenebrionidae: Platynotina)

Owing to the reinterpretation of its morphological synapomorphies, the taxonomic composition of the Ectateus generic group had been ambiguous. The present study scrutinized all existing taxonomic concepts of the group based on a cladistic analysis of the adult morphology of all of the Afrotropical platynotoid Platynotina genera. The phylogenetic relationships were reconstructed using parsimony and Bayesian inference. The results show that all previous taxonomic concepts of the Ectateus generic group concerned paraphyletic entities. The cladistic analysis revealed the following synapomorphies for the taxon: (1) presence of basal indentations of the pronotal disc, (2) ratio of prothorax width to its maximal height > 6.0, and (3) ratio of maximal height of the prothorax to total height < 0.3. Moreover, phylogenetic studies revealed the existence of the Upembarus generic group, a sister‐taxon group to the Ectateus generic group, within the Afrotropical platynotoid Platynotina. Autapomorphic and synapomorphic character mapping show that several taxonomic and nomenclatural changes are needed to consider the particular generic‐level entities traditionally assigned to Afrotropical platynotoid Platynotina as monophyletic lineages. The following taxonomic and nomenclatural adjustments are made in this paper: P teroselinus gen. nov. is erected to accommodate a single species that was previously assigned to Zidalus: Pteroselinus insularis comb. nov. Additionally, the following synonymies are proposed: Anchophthalmops (= Platykochius syn. nov. ), Angolositus (= Aberlencus syn. nov. , = Platymedvedevia syn. nov. ), Glyptopteryx (= Microselinus syn. nov. , = Quadrideres syn. nov. , = Synquadrideres syn. nov. ). In addition, Kochogaster is lowered in rank and is treated as one of the subgenera of Anchophthalmus. Moreover, Pseudoselinus is treated as a subgenus of Upembarus. An identification key to all Afrotropical platynotoid Platynotina genera and subgenera is presented. Zoogeographical analyses revealed the following dispersal barriers for the Ectateus generic group: (1) the Sahara (northern barrier); (2) the dry ecosystems of Botswana, Namibia, and South Africa (southern barrier); and (3) the Congolian rainforests (internal distributional gap). The ancestor of the taxon probably originated in East African ecoregions that predominantly contained wattletrees (acacias) and Commiphora Jacq. Moreover, past climate changes seem to have had a great impact on the observed generic distribution. © 2015 The Linnean Society of London     

基于树干液流及涡动相关技术的葡萄冠层蒸腾及蒸散发特征研究

针对西北干旱区绿洲经济作物葡萄树冠层蒸腾及蒸散发特征的相关问题,在甘肃省敦煌市南湖绿洲开展无核白葡萄树液流速率及蒸散发观测试验,采用基于热平衡原理的包裹式茎流计,详细分析了典型生长季7—9月份葡萄树蒸腾耗水规律,使用"单位叶面积上的平均液流速率SF×叶面积指数LAI"的方法,实现了从单株到林分冠层蒸腾的尺度扩展,并通过与涡动相关技术所测蒸散发数据对比,详细研究了葡萄地冠层蒸腾及蒸散发规律。结果表明:典型生长季中葡萄树液流速率日变化为单峰型曲线,日均耗水量从2.76 kg到10 kg不等,胸径越大的葡萄树日均耗水量越大;冠层蒸腾及蒸散发日变化曲线亦为单峰型,白天8:00—12:00与17:00—20:00期间,葡萄冠层蒸腾与蒸散发曲线均比较吻合,该时间段葡萄地蒸散发绝大部分来源于葡萄冠层蒸腾,而12:00—17:00之间由于午后太阳辐射强烈土壤蒸发量增加,葡萄蒸散发大于冠层蒸腾;典型生长季3个月中,葡萄冠层蒸腾量的变化范围在1.88—8.12 mm/d之间,日均冠层蒸腾量为6.12 mm/d,蒸散发在1.74 mm/d至10.78 mm/d之间,日均蒸散发量为7.13 mm/d;日均土壤蒸发量约为1.01 mm/d,只占总蒸散发量的14.2%,日均冠层蒸腾占日均蒸散发的比重达到85.8%,说明该生长阶段冠层蒸散发以作物蒸腾为主。     

The Maghreb – one more important biodiversity hot spot for tiger beetle fauna (Coleoptera,Carabidae, Cicindelinae) in the Mediterranean region

The tiger beetle fauna of the Maghreb region is one of the richest in the Palaearctic, including 22 species and 5 subspecies and 19% of all Palaearctic species of Cicindelinae. Assembled to their chorotypes, the Maghreb tiger beetles fall into eight different groups that include Maghreb endemics (26% of fauna), Mediterranean (7%), West Mediterranean (40%), North African (4%), Mediterranean-Westturanian (4%), West Palaearctic (4%), Afrotropico-Indo-Mediterranean (4%), and Saharian (11%) species. The Mediterranean Sclerophyl and Atlas Steppe are the Maghreb biogeographical provinces with the highest species richness, while the Sahara Desert has the lowest Cicindelinae diversity. Twenty-five cicindelid species and subspecies (93% of Maghreb fauna) are restricted to only one or two habitat types in lowland areas. Only Calomera littoralis littoralis and Lophyra flexuosa flexuosa are recognized as eurytopic species and occur in three types of habitat. The highest tiger beetle diversity characterizes salt marshes and river banks (in both cases 11 species and subspecies or 41% of Maghreb fauna). Approximately 85% of all Maghreb tiger beetle species and subspecies are found in habitats potentially endangered by human activity.     

Molecular phylogeny of Macrolycus (Coleoptera: Lycidae) with description of new species from China

Macrolycus is a genus of net‐winged beetles with 69 species distributed in the eastern Palearctic and northernmost part of the Oriental region. The first molecular phylogeny of Macrolycus was produced using an rrnL + tRNA‐Leu + nad1 mtDNA fragment. The major lineages and species limits were identified with morphology and molecular data. We propose that Cerceros is a subgenus of Macrolycus to enable identification of all adult specimens in the genus without DNA sequencing. Two species groups are proposed in Macrolycus s. str. and six in Cerceros. Additionally, twelve Macrolycus species are newly described from China: M. aquilinus, M. baihualingensis, M. bicolor, M. guangxiensis, M. jianfenglingensis, M. kuatunensis, M. lizipingensis, M. parvus, M. phoeniceus, M. rhodoneurus, M. rosaceus and M. sichuanensis. Macrolycus holzschuhi is proposed to be a junior subjective synonym of M. jeanvoinei. The highest diversity of Macrolycus is found in southern China. The species from the main islands of Japan are placed in two species groups: M. excellens is a sister to remaining species of the M. murzini group and the M. flabellatus group is a monophylum of closely related species in a sister position to the M. bicolor group.     

Minimizing the biodiversity impact of Neotropical oil palm development

Oil palm agriculture is rapidly expanding in the Neotropics, at the expense of a range of natural and seminatural habitats. A key question is how this expansion should be managed to reduce negative impacts on biodiversity. Focusing on the Llanos of Colombia, a mixed grassland–forest system identified as a priority zone for future oil palm development, we survey communities of ants, dung beetles, birds and herpetofauna occurring in oil palm plantations and the other principal form of agriculture in the region – improved cattle pasture – together with those of surrounding natural forests. We show that oil palm plantations have similar or higher species richness across all four taxonomic groups than improved pasture. For dung beetles, species richness in oil palm was equal to that of forest, whereas the other three taxa had highest species richness in forests. Hierarchical modelling of species occupancy probabilities indicated that oil palm plantations supported a higher proportion of species characteristic of forests than did cattle pastures. Across the bird community, occupancy probabilities within oil palm were positively influenced by increasing forest cover in a surrounding 250 m radius, whereas surrounding forest cover did not strongly influence the occurrence of other taxonomic groups in oil palm. Overall, our results suggest that the conversion of existing improved pastures to oil palm has limited negative impacts on biodiversity. As such, existing cattle pastures of the Colombian Llanos could offer a key opportunity to meet governmental targets for oil palm development without incurring significant biodiversity costs. Our results also highlight the value of preserving remnant forests within these agricultural landscapes, protecting high biodiversity and exporting avian ‘spill‐over’ effects into oil palm plantations.     

Identification of potential natural enemies of the pea leaf weevil,Sitona lineatus L. in western Canada

Sitona lineatus L., the pea leaf weevil, is an invasive pest of Pisum sativum L. (field pea) that has recently become established in Alberta, Canada. Adults consume seedling foliage and larvae feed on Rhizobium root nodules thereby reducing nitrogen fixation; both life stages can reduce yield. Eggs and adults are vulnerable to predators and parasitoids. In 2009, a series of experiments was undertaken to identify potential indigenous natural enemies of S. lineatus in southern Alberta. In three test arenas, eggs were exposed to starved ground beetles in no‐choice tests for 48 h. Egg debris was observed when eggs were exposed to Bembidion quadrimaculatum L., Microlestes linearis (LeConte), Bembidion rupicola (Kirby), Bembidion timidum (LeConte), Poecilus scitulus LeConte, and staphylinid beetles. Of the two most abundant carabid species, the smaller B. quadrimaculatum consistently removed significantly more eggs (94.6%) than the larger Pterostichus melanarius (17.4%). Similar results were observed in Petri dish and egg card tests. No egg debris was observed in tests with Pt. melanarius. Presence of the larger beetle, Pt. melanarius, resulted in a lower rate of egg removal by the smaller B. quadrimaculatum relative to the rates observed for B. quadrimaculatum alone. Intraguild predation of B. quadrimaculatum by Pt. melanarius was observed in 47% of tests. These results suggest that B. quadrimaculatum is a potential predator of S. lineatus eggs in field pea agroecosystems and should be considered for use in conservation biological control and integrated pest management programs.