Brood size: a major factor influencing male dimorphism in the non‐pollinating fig wasp Sycobia sp.

• 1 Male polymorphisms have been described in some non‐pollinating fig wasps, as well as in other animals. The proximal basis and the maintenance of alternative male reproductive strategies are either genetic or environmental.
• 2 Here we studied male dimorphism in the non‐pollinating fig wasp Sycobia sp. We conducted experimental manipulations to study the factors influencing offspring male morph allocations and explore a possible basis for the determination and maintenance of male dimorphism in Sycobia sp.
• 3 The results showed that brood size was the major and underlying factor influencing the male morph ratio. When the brood size increases, the wingless male ratio also increases.
• 4 Also, our results indicated that there was no direct maternal control on offspring male morph allocation.
• 5 Male dimorphism in Sycobia sp. probably represents an environmentally determined conditional strategy, which responded to offspring population density at the level of the individual fig.

     

Permanent Genetic Resources added to Molecular Ecology Resources Database 1 May 2009-31 July 2009

This article documents the addition of 512 microsatellite marker loci and nine pairs of Single Nucleotide Polymorphism (SNP) sequencing primers to the Molecular Ecology Resources Database. Loci were developed for the following species: Alcippe morrisonia morrisonia, Bashania fangiana, Bashania fargesii, Chaetodon vagabundus, Colletes floralis, Coluber constrictor flaviventris, Coptotermes gestroi, Crotophaga major, Cyprinella lutrensis, Danaus plexippus, Fagus grandifolia, Falco tinnunculus, Fletcherimyia fletcheri, Hydrilla verticillata, Laterallus jamaicensis coturniculus, Leavenworthia alabamica, Marmosops incanus, Miichthys miiuy, Nasua nasua, Noturus exilis, Odontesthes bonariensis, Quadrula fragosa, Pinctada maxima, Pseudaletia separata, Pseudoperonospora cubensis, Podocarpus elatus, Portunus trituberculatus, Rhagoletis cerasi, Rhinella schneideri, Sarracenia alata, Skeletonema marinoi, Sminthurus viridis, Syngnathus abaster, Uroteuthis (Photololigo) chinensis, Verticillium dahliae, Wasmannia auropunctata, and Zygochlamys patagonica. These loci were cross-tested on the following species: Chaetodon baronessa, Falco columbarius, Falco eleonorae, Falco naumanni, Falco peregrinus, Falco subbuteo, Didelphis aurita, Gracilinanus microtarsus, Marmosops paulensis, Monodelphis Americana, Odontesthes hatcheri, Podocarpus grayi, Podocarpus lawrencei, Podocarpus smithii, Portunus pelagicus, Syngnathus acus, Syngnathus typhle,Uroteuthis (Photololigo) edulis, Uroteuthis (Photololigo) duvauceli and Verticillium albo-atrum. This article also documents the addition of nine sequencing primer pairs and sixteen allele specific primers or probes for Oncorhynchus mykiss and Oncorhynchus tshawytscha; these primers and assays were cross-tested in both species.     

Permanent Genetic Resources added to Molecular Ecology Resources Database 1 June 2010 - 31 July 2010

This article documents the addition of 205 microsatellite marker loci to the Molecular Ecology Resources Database. Loci were developed for the following species: Bagassa guianensis, Bulweria bulwerii, Camelus bactrianus, Chaenogobius annularis, Creontiades dilutus, Diachasmimorpha tryoni, Dioscorea alata, Euhrychiopsis lecontei, Gmelina arborea, Haliotis discus hannai, Hirtella physophora, Melanaphis sacchari, Munida isos, Thaumastocoris peregrinus and Tuberolachnus salignus. These loci were cross-tested on the following species: Halobaena caerulea, Procellaria aequinoctialis, Oceanodroma monteiroi, Camelus ferus, Creontiades pacificus, Dioscorea rotundata, Dioscorea praehensilis, Dioscorea abyssinica, Dioscorea nummularia, Dioscorea transversa, Dioscorea esculenta, Dioscorea pentaphylla, Dioscorea trifida, Hirtella bicornis, Hirtella glandulosa, Licania alba, Licania canescens, Licania membranaceae, Couepia guianensis and 7 undescribed Thaumastocoris species.     

Exploring landscape structure effect on termite territory size using a model approach

The foraging territory of the Formosan subterranean termite, Coptotermes formosanus Shiraki, was simulated by using a lattice model in order to study how landscape structure affects the foraging territory. Three kinds of landscape were generated on lattice space: ideal, random and fractal landscape. Each lattice cell had a value ranging from 0.0 to 1.0, interpreted as transition probability, P_trans, which represents spatially distributed property of the landscapes. The heterogeneity of the fractal landscape was characterized by a parameter, H, controlling aggregation of lattice cells with higher value of P_trans. Higher H values corresponded to higher aggregation levels. The model made use of minimized local rules based on empirical data that determines the development of the foraging territory. Additionally, seasonal cycle (summer and winter season), and obstacles which hinder the growth of the territory were incorporated in the model as environmental variables. Territory size was largest in the ideal landscape while it was larger in the random landscape than in the fractal landscape. As obstacle density increased, the territory size decreased. In the fractal landscape, the territory size increased, decreased, and increased again as H increased.     

Juvenile hormone esterase activity in the pupating and diapausing larvae of Sesamia nonagrioides

The development of the Mediterranean corn borer, Sesamia nonagrioides, under long-day (LD) photoperiod is associated with juvenile hormone (JH) decline and pupation in the 5th or 6th larval instar. The larvae grown under short-day (SD) conditions maintain a moderate JH titer and enter diapause during which they undergo several extra larval molts. Both types of larvae exhibit similar levels of juvenile hormone esterase (JHE) activity that increases in each instar during the period of low ecdysteroid titer and drops when the titer rises to a molt-inducing peak. A suppression of JHE activity within 24h after application of an ecdysteroid agonist suggests that the drop of activity is a rapid and possibly direct response to ecdysteroids or their agonist. Esterase inhibitor 3-octylthio-1,1,1-trifluoro-2-propanone (OTFP) suppressed more than 98% of the JHE activity without affecting pupation timing and adult development. The data indicate that JHE is not crucial for the switch between larval development, diapause, and metamorphosis in S. nonagrioides.     

Natural occurrence of insect pathogenic fungi and insect parasitic nematodes in <Emphasis Type="Italic">Diabrotica virgifera virgifera</Emphasis> populations

The Western Corn Rootworm D. virgifera virgifera Le Conte (Coleoptera: Chrysomelidae), a serious pest of maize, has been recently introduced into Europe. Several approaches for its control are presently under investigation including microbial agents. In order to get information on the role of naturally occurring pathogens in the regulation of Diabrotica populations, we started an investigation in established populations in Hungary, Romania, Serbia, Austria, and Italy in 2005 and 2006. In infested maize fields in Hungary, plants and their root systems were grubbed out and larvae and pupae were collected. Adult D. v. virgifera were collected in Hungary, Austria, Romania, Serbia and Italy. Additionally, the occurrence of entomopathogenic fungi in soils of maize fields was determined using Galleria mellonella and Tenebrio molitor larvae as bait insects. The density of entomopathogenic fungi was obtained by plating soil suspension on selective medium. Metarhizium anisopliae and Beauveria spp. infections were found in 1.4% of field collected larvae, 0.2% of field collected pupae and 0.05% of field collected adults. Whereas natural infections of D. v. virgifera were rarely found, a high density of insect pathogenic fungi was recorded in Hungarian soils. M. anisopliae could be detected in every maize field either using the “bait method” or a “selective medium” method. This is the first report of a natural occurrence of entomoparasitic nematodes (Heterorhabditis sp., Steinernema sp.) in Diabrotica v. virgifera in Europe.     

The effect of spatial scale on interactions between two weevils and their food plant

The effect of spatial scale on the interactions between the weevils Gymnetron pascuorum Gyll. and Mecinus pyraster Herbst and their host plant, ribwort plantain Plantago lanceolata L., was studied. Both weevils developed in plantain seedheads but occupied different niches within the seedhead. Seedheads were sampled annually from 162 plants at each of two experimental sites consisting of a series of habitat patches of two distinct sizes. Data were analysed from three site-years. Our results suggest that the density of available seedheads varied among years and this had a direct effect on abundance. M. pyraster, which develops in the stem within the seedhead, was more sensitive to changes in seedhead density than was G. pascuorum, which develops within the seeds themselves. The presence of a hedgerow along one side of the experimental site affected the pattern of colonisation of newly-created habitat patches by G. pascuorum but not by M. pyraster. Changes in spatial scale did not affect the variability of seedhead and insect densities. G. pascuorum had an aggregated distribution at all the spatial scales considered, but the distribution of M. pyraster was very scale dependent. The distributions of the two weevil species were positively associated amongst infested plants but not amongst infested seedheads. Behavioural and ecological factors that could explain the results of the data analyses are discussed.     

Lineage specific evolution of an alternative social strategy in Tetramorium ants (Hymenoptera: Formicidae)

The western Palearctic ant, Tetramorium moravicum , is the only species of the large genus known to display two alternative social strategies: macrogyny-monoygyny (characterized by one large queen per colony) and microgyny-polygyny (multiple small queens per colony). The microgyne colonies of this ant are confined to the westernmost part of its distribution area and occasionally co-occur with macrogyne colonies. We investigated phylogenetic and geographical patterns in relation to social strategy by analysing 1031 bp of the mitochondrial cytochrome c oxidase subunit I gene of T. moravicum from the entire known species range. Phylogenetic analyses revealed two clear-cut lineages coinciding with the eastern and western populations, which probably were separated after the late Quaternary glacial periods. Geographical distance analysis suggested allopatric fragmentation of the two lineages. We hypothesize that the two lineages colonized Central Europe postglacially from two directions. The current distribution gap of 500 km between the tip of the eastern lineage, in the Czech Republic, Austria and Hungary, and the western lineage, in Germany, was confirmed by hierarchical population analysis. Macrogyny-monogyny probably was the original condition in T. moravicum ; the alternative strategy of microgyny-polygyny may have evolved at the tip of the western lineage, as recently as the early Holocene.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 91 , 247–255.     

Selection of entomopathogenic fungi for the control of the western corn rootworm Diabrotica virgifera virgifera

Abstract:  The western corn rootworm Diabrotica virgifera virgifera Le Conte (Col., Chrysomelidae), a serious pest of maize, has been recently introduced into Europe. Several approaches for its control are presently under investigation including microbial agents. During a field survey in Hungary in 2005, naturally occurring entomopathogenic fungi were found to attack this pest. These novel isolates together with standard isolates were tested for virulence against D. v. virgifera larvae and adults. Twenty strains of Metarhizium anisopliae , Beauveria bassiana and Beauveria brongniartii were used in bioassays in the laboratory. Larvae and adults were dipped into a spore suspension with a concentration of 1 × 10⁷ conidia (con.)/ml. They were kept for 14 days at 22°C (±2°C) and 70% relative humidity. The number of infected larvae and adults were counted and infection rates were calculated. Adults were significantly more susceptible to entomopathogenic fungi than larvae. The most virulent isolate infected about 47% of larvae ( M. anisopliae Ma2277), whereas the infection rate in adults was up to 97% ( M. anisopliae Ma2275). Isolates of M. anisopliae caused significantly higher mortalities than isolates of B. brongniartii and B. bassiana . Most of the adult beetles were killed within 12 days. Isolates from D. v. virgifera were more virulent than those from other hosts.