Scale-dependent effects of windthrow disturbance on forest arthropod communities

The effect of disturbance on local communities may operate within the context of the spatial landscape. We examined the scale-dependent effects of windthrow disturbance caused by a large typhoon on three arthropod communities in a temperate forest of Japan. Canopy arthropods were collected by beating foliage, forest-floor arthropods were collected by sweeping the vegetation, and flying arthropods were collected in Malaise traps. To assess the “functional spatial scale” at which arthropods responded to tree-fall disturbance, the gap rate was quantified at different spatial scales by sequentially enlarging the radius of a circular landscape sector in 10-m increments from 10 to 500 m. We then analyzed the responses of order richness and abundance to the gap rate for each arthropod community. The spatial scale of the significant best-fitting model, which was selected from the models fitted to the gap rate at stepwise spatial scales, was regarded as the arthropod-specific functional spatial scale. Arthropod order richness was not dependent on the gap rate. In contrast, arthropod order abundance depended significantly on the gap rate in many orders, but varied in the response direction and functional spatial scale. These order-specific, scale-dependent responses to tree-fall gaps could complicate interactions among organisms, leading to complex community organization. An understanding of the spatial processes that link the use of space by organisms with the spatial scale at which ecological processes are experienced is required to elucidate the responses of populations, communities, and biotic interactions to disturbances in a spatial landscape context.     

Natural enemy impacts on Bemisia tabaci (MEAM1) dominate plant quality effects in the cotton system

1. Plant quality (bottom‐up effects) and natural enemies (top‐down effects) affect herbivore performance. Furthermore, plant quality can also influence the impact of natural enemies. 2. Lower plant quality through reduced irrigation increased the abundance of the cryptic species from the Bemisia tabaci complex [hereafter B. tabaci Middle East Asia Minor 1 (MEAM1)], but not its natural enemies on cotton. It was therefore predicted that lower plant quality would diminish the impact of natural enemies in regulating this herbivore. 3. Over three cotton seasons, plant quality was manipulated via differential irrigation and natural enemy abundance with insecticides. Life tables were used to evaluate the impact of these factors on mortality of immature B. tabaci (MEAM1) over nine generations. 4. Mortality of B. tabaci (MEAM1) was consistently affected by natural enemies but not by plant quality. This pattern was driven by high levels of sucking predation, which was the primary (key) factor associated with changes in immature mortality across all irrigation and natural enemy treatments. Dislodgement (chewing predation and weather) and parasitism contributed as key factors in some cases. Analyses also showed that elimination of sucking predation and dislodgement would have the greatest effect on overall mortality. 5. The top‐down effects of natural enemies had dominant effects on populations of B. tabaci (MEAM1) relative to the bottom‐up effects of plant quality. Effects were primarily due to native generalist arthropod predators and not more host‐specific aphelinid parasitoids. The findings of this study demonstrate the important role of arthropod predators in population suppression and validate the importance of conservation biological control in this system for effective pest control.     

A geographic distribution database of Mononychellus mites (Acari,Tetranychidae) on cassava (Manihot esculenta)

The genus Mononychellus is represented by 28 herbivorous mites. Some of them are notorious pests of cassava (Manihot esculenta Crantz), a primary food crop in the tropics. With the exception of Mononychellus tanajoa (Bondar), their geographic distribution is not widely known. This article therefore reports observational and specimen-based occurrence data of Mononychellus species associated with cassava. The dataset consists of 1,513 distribution records documented by the International Center for Tropical Agriculture (CIAT) between 1975 and 2012. The specimens are held at CIAT’s Arthropod Reference Collection (CIATARC). Most of the records are from the genus’ native range in South America and were documented between 1980 and 2000. Approximately 61% of the records belong to M. tanajoa, 25% to M. caribbeanae (McGregor), 10% to M. mcgregori (Flechtmann and Baker) and 2% to M. planki (McGregor). The complete dataset is available in Darwin Core Archive format via the Global Biodiversity Information Facility (GBIF).     

The effects of foliar pubescence and nutrient enrichment on arthropod communities of Metrosideros polymorpha (Myrtaceae)

Abstract.  1. Nutrient resource availability and host-plant foliar pubescence both influence arthropod food webs, but multifactor studies are needed to understand their interdependence and relative importance. Arthropods were sampled by clipping foliage from Metrosideros polymorpha (Myrtaceae) trees of pubescent, glabrous, and intermediate leaf forms on fertilised and unfertilised plots.
2. Fertilisation decreased leaf mass per area (LMA) but did not change the relative mass of pubescence within leaf morphological classes.
3. Fertilisation increased densities of individuals in four taxonomic orders, densities of individuals and species of all trophic levels, and the biomass of Collembola and Homoptera. Herbivore relative diversity (Shannon H ') also increased with fertilisation, but detritivore diversity declined due to increasing dominance of Salina celebensis (Schaeffer) (Collembola).
4. Detritivore density, driven again by S. celebensis , increased with decreasing leaf pubescence, but Heteroptera and Acari were most abundant on the intermediate pubescence class, and Psocoptera density and biomass increased with increasing pubescence. Trophic-level species density did not change with leaf morphological class, but relative diversity of all arthropods and of detritivores increased with increasing pubescence.
5. Both resource availability and leaf pubescence affected Metrosideros arthropod communities. However, the pervasive positive influence of fertilisation did not translate to compositional shifts, and there were no interactions with leaf morphological class. In contrast, the effects of leaf pubescence on arthropod density, biomass, and diversity were more restricted taxonomically, and non-parametric manova and redundancy analyses demonstrated significant differentiation in community composition on the pubescent morphology.     

A geographic distribution database of the Neotropical cassava whitefly complex (Hemiptera,Aleyrodidae) and their associated parasitoids and hyperparasitoids (Hymenoptera)

Whiteflies (Hemiptera, Aleyrodidae) are represented by more than 1,500 herbivorous species around the world. Some of them are notorious pests of cassava (Manihot esculenta), a primary food crop in the tropics. Particularly destructive is a complex of Neotropical cassava whiteflies whose distribution remains restricted to their native range. Despite their importance, neither their distribution, nor that of their associated parasitoids, is well documented. This paper therefore reports observational and specimen-based occurrence records of Neotropical cassava whiteflies and their associated parasitoids and hyperparasitoids. The dataset consists of 1,311 distribution records documented by the International Center for Tropical Agriculture (CIAT) between 1975 and 2012. The specimens are held at CIAT’s Arthropod Reference Collection (CIATARC, Cali, Colombia). Eleven species of whiteflies, 14 species of parasitoids and one species of hyperparasitoids are reported. Approximately 66% of the whitefly records belong to Aleurotrachelus socialis and 16% to Bemisia tuberculata. The parasitoids with most records are Encarsia hispida, Amitus macgowni and Encarsia bellottii for Aleurotrachelus socialis; and Encarsia sophia for Bemisia tuberculata. The complete dataset is available in Darwin Core Archive format via the Global Biodiversity Information Facility (GBIF).     

Exoskeletal cuticle of cavernicolous and epigean terrestrial isopods: A review and perspectives

Comparative ultrastructural studies of the integument in terrestrial isopod crustaceans show that specific environmental adaptations of different eco-morphotypes are reflected in cuticle structure. The biphasic molting in isopods is a valuable experimental model for studies of cuticular matrix secretion and degradation in the same animal. The aim of this review is to show structural and functional adaptations of the tergal cuticle in terrestrial isopods inhabiting cave habitats. Exoskeletal cuticle thickness, the number of cuticular layers, epicuticle structure, mineralization, pigmentation and complexity of sensory structures are compared, with greater focus on the well-studied cave trichoniscid Titanethes albus. A large number of thinner cuticular layers in cave isopods compared to fewer thicker cuticular layers in related epigean species of similar body-sizes is explained as a specific adaptation to the cavernicolous life style. The epicuticle structure and composition are compared in relation to their potential waterproofing capacity in different environments. Cuticle mineralization is described from the functional point of view as well as from the aspect of different calcium storage sites and calcium dynamics during the molt cycle. We also discuss the nature and reduction of pigmentation in the cave environment and outline perspectives for future research.     

Linking gene regulation to cell behaviors in the posterior growth zone of sequentially segmenting arthropods

Virtually all arthropods all arthropods add their body segments sequentially, one by one in an anterior to posterior progression. That process requires not only segment specification but typically growth and elongation. Here we review the functions of some of the key genes that regulate segmentation: Wnt, caudal, Notch pathway, and pair-rule genes, and discuss what can be inferred about their evolution. We focus on how these regulatory factors are integrated with growth and elongation and discuss the importance and challenges of baseline measures of growth and elongation. We emphasize a perspective that integrates the genetic regulation of segment patterning with the cellular mechanisms of growth and elongation.     

Insights from functional morphology and neoichnology for determining tracemakers: a case study of the reconstruction of an ancient glacial arthropod‐dominated fauna

Apportioning trace fossils to producers is significant for palaeoecological and palaeoenvironmental studies. A tracemaker is usually attributed through the comparison of the morphology of the trace to the body plans of modern and extinct animals. However, hypotheses of tracemaker identifications may be tested with the use of further methods. This contribution aims to evaluate the potential tracemakers of a trackway‐dominated ichnofauna preserved in the siltstone–claystone rhythmites of the Pennsylvanian Rio do Sul Formation in the southern Brazil. These deposits are typical of the deglaciation phase of the Late Palaeozoic Ice Age of Gondwana in the Paraná Basin. Thus, the parameters applied in this work are as follows: (1) functional analyses of the traces to infer the biomechanics of the locomotion of the producer; and (2) neoichnology, whereby modern traces whose producers are known are compared to those of the ichnofauna in question. The conclusions obtained with these methods strongly support millipedes as the producers of Diplichnites gouldi and Diplopodichnus biformis. The malacostracan crustacean‐related ichnogenera are Umfolozia sinuosa and Gluckstadtella elongata, produced by syncarids or peracarids, while isopods are suggested as the tracemakers of Glaciichnium isp. and Protovirgularia dichotoma. In terms of branchiopod crustaceans, Cruziana problematica is attributed to notostracans. Helminthoidichnites tenuis, Mermia carickensis and Treptichnus pollardi are considered traces produced by insect larvae. The palaeobiology of the tracemakers that produced the ichnofauna preserved in the rhythmites of the Rio do Sul Formation permits inferences that terrestrial (millipedes) and aquatic (crustaceans and insect larvae) animals colonized the sediments. This conclusion points to a dynamic depositional environment, with changing physical and chemical parameters conditioning the biota.     

两种除草剂对棉田节肢动物群落多样性指数的影响

系统地研究了棉田地面和棉株节肢动物群落及各亚群落施用克无踪(A)、高盖(B)与对照(CK)之间在群落生物多样性、丰富度和均匀度的差异.结果表明,对地面肉食动物群落生物多样性(H′)的A-CK的t值为3.099,B-CK的t值为2.449,t＞t_0.05=2.228,差异显著;地面植食动物亚群落的(H′)A-CK的t值为2.377,A-B为2.260,t＞t_0.05=2.228,差异均显著.棉株节肢动物群落及亚群落A-CK、B-CK和A-B之间差异不显著.地面节肢动物亚群落丰富度A-CK的t值为4.759,地面植食类节肢动物亚群落为4.359,地面肉食节肢动物亚群落为2.963,均t＞t0.0=2.228,表明A与CK之间差异显著;在均匀度上,A和B及A-CK、B与CK之间两类群落及亚群落上差异均不显著.A和B对棉株节肢动物群落影响很小.施用A和B及CK的生物多样性的变化总趋势一致.