Effects of Natural Habitat and Season on Cursorial Spider Assemblages in Mediterranean Vineyards.

Natural habitats adjacent to vineyards are presumed to have a positive effect on the diversity of natural enemies within the vineyards. However, these habitats differ in vegetation structure and seasonal phenology and in turn could affect the species composition of natural enemies. Here, we compared the species richness and diversity and the composition of spider assemblages in several locations within three commercial vineyards and the nearby natural habitats in a Mediterranean landscape in northern Israel. We sampled spiders by means of pitfall traps in early and in late summer. Both the time in the season and the habitat (natural versus vineyard) affected spider species richness and diversity. More species were found in early summer (47) than in late summer (33), and more occurred in the natural habitat (34 species) than in the vineyards (27-31 species). Fifteen species were found exclusively in the natural habitat, and only 11 species were shared by the vineyards and natural habitat, four of which were the most abundant and geographically widely distributed species in the samples. In late summer, spider diversity in the natural habitat was higher than within the vineyards: the spider assemblages in the vineyards became dominated by a few species late in the crop season, while those of the natural habitat remained stable. Overall, the natural habitat differed in assemblage composition from all within-vineyard locations, while the three locations within the vineyard did not differ significantly in assemblage composition. Season (early vs. late summer), however, significantly affected the spider assemblage composition. This study documents the large diversity of spiders in a local Mediterranean vineyard agroecosystem. Over 60% of the known spider families in the region occurred in our samples, highlighting the importance of this agroecosystem for spider diversity and the potential for conservation biocontrol, where natural habitats may be a source of natural enemies for nearby vineyards.

Does mating disruption of Planococcus ficus and Lobesia botrana affect the diversity, abundance and composition of natural enemies in Israeli vineyards?

BACKGROUND: Mating disruption (MD) employs high doses of a pest's synthetic sex pheromone in agricultural plots, to interfere with its reproduction. MD is assumed to have few behavioral effects on non-target arthropods, because sex pheromones are highly species-specific and non-toxic. Nevertheless, some natural enemies use their host's sex pheromones as foraging cues, and thus may be attracted to MD plots. To investigate this hypothesis, we compared parasitoid and spider assemblages in paired plots in five Israeli vineyards during 2015. One plot was MD-treated against two key pests, Lobesia botrana (Denis & Schiffermüller) and Planococcus ficus (Signoret). Both plots were insecticide-treated as needed. Natural enemies were suction-sampled and collected from pheromone-baited monitoring traps. RESULTS: The total abundance, species diversity and species composition of most natural enemies were unaffected by MD. An important exception involved P. ficus' main parasitoid, Anagyrus sp. nr. pseudococci (Girault). Anagyrus sp. nr. pseudococci females were mainly captured in control plots, while male captures were low and not influenced by MD. Parasitized P. ficus occurred only in MD plots. CONCLUSION: Non-target effects of MD involved mostly A. sp. nr. pseudococci females and hardly affected other natural enemies. These findings support the use of MD as an environmentally friendly pest management strategy. © 2018 Society of Chemical Industry.

Copulation with immature females increases male fitness in cannibalistic widow spiders.

Copulatory cannibalism of male 'widow' spiders (genus Latrodectus) is a model example of the extreme effects of sexual selection, particularly in L. hasselti and L. geometricus where males typically facilitate cannibalism by females and mate only once. We show that these males can increase their reproductive success by copulating with final-instar, immature females after piercing the female's exoskeleton to access her newly developed sperm storage organs. Females retain sperm through their final moult and have similar fecundity to adult-mated females. This is an adaptive male tactic because immature mating increases insemination success relative to adult mating (which predicts higher paternity) and moreover, rarely ends in cannibalism, so males can mate again. Although successful only during a brief period before the female's final moult, males may employ this tactic when they associate with final-instar females in nature. Consistent with this, one-third of L. hasselti females collected as immatures in nature were already mated. Immature mating alters sexual selection on these otherwise monogynous males, and may explain male traits allowing facultative polygyny in Latrodectus Since male cohabitation with immature females is common among invertebrates, immature mating may be a widespread, previously unrecognized mating tactic, particularly when unmated females are of high reproductive value.

Female detection of the synthetic sex pheromone contributes to the efficacy of mating disruption of the European grapevine moth, Lobesia botrana.

BACKGROUND: Studies of the mechanisms by which mating-disruption techniques control insect pest populations have traditionally focused on the effects of the species-specific sex pheromone on the male moths, while neglecting possible direct effects of the pheromone on females. Here, the effects of exposure to synthetic species-specific sex-pheromone on Lobesia botrana (European grapevine moth) females were tested. RESULTS: Females in vineyards that were treated with mating-disruption pheromone burst into short bouts of flying more frequently, but called significantly less frequently than females in untreated plots. Reduced calling caused by exposure to the species-specific sex-pheromone may increase the age at which females mate and thereby reduce female fecundity. Females that called in a pheromone-saturated environment experienced a decrease in number of oviposited eggs. A further decrease in reproductive success may occur if females delay oviposition when exposed to access of the synthetic pheromone. CONCLUSIONS: In addition to reducing the ability of males to locate females, the mating-disruption technique can suppress pest numbers as a consequence of its direct effects on females. The two mechanisms probably act synergistically.

Fitness cost of pheromone production in signaling female moths.

A secondary sexual character may act as an honest signal of the quality of the individual if the trait bears a cost and if its expression is phenotypically condition dependent. The cost of increasing the trait should be tolerable for individuals in good condition but not for those in a poor condition. The trait thus provides an honest signal of quality that enables the receiver to choose higher quality mates. Evidence for sex pheromones, which play a major role in shaping sexual evolution, inflicting a signaling cost is scarce. Here, we demonstrate that the amount of the major component of the pheromone in glands of Lobesia botrana (Lepidoptera) females at signaling time was significantly greater in large than in small females, that male moths preferred larger females as mates when responding to volatile signals, and small virgin females, but not large ones, exposed to conspecific pheromone, produced, when mated, significantly fewer eggs than nonexposed females. The latter indicates a condition-dependent cost of signaling. These results are in accordance with the predictions of condition-dependent honest signals. We therefore suggest that female signaling for males using sex pheromones bears a cost and thus calling may serve as honest advertisement for female quality.

Developmental patterns in the polyembryonic parasitoid wasp Copidosoma koehleri.

Polyembryony is a unique mode of development in which multiple genetically identical embryos develop from a single egg. In some polyembryonic species a proportion of the embryos develop into soldier larvae, which attack competitors in the host. We studied the development of the polyembryonic wasp Copidosoma koehleri in its host Phthorimaea opercullela. We dissected hosts parasitized by either virgin or mated female wasps at 2day intervals from hatching to the final instars. We documented host mass and head width, the number and size of developing wasps and the presence of a soldier larva. Additionally, we kept a sample of parasitized hosts until emergence of wasps and measured the head width of emerging adults. We characterized wasp development in relation to host development. One half of the broods produced by mated wasps contained one soldier larva throughout development. This suggests that in C. koehleri each female brood produces a single soldier larva, and that the soldier probably survives and grows gradually during host development. Additionally, we found that female broods were larger than male broods during development and also upon emergence. Accordingly, body size was larger for males during development as well as upon emergence. These findings may extend the existing knowledge on polyembryonic development in general, and serve as a baseline for further experiments.

Pest management programmes in vineyards using male mating disruption.

Israeli vine growers have been reluctant to adopt the mating disruption technique for control of the European vine moth, Lobesia botrana Den. & Schiff. Since the chemically controlled honeydew moth, Cryptoblabes gnidiella Mill., coexists with the European vine moth, growers have maintained that the use of mating disruption would fail to bring about a significant reduction in pesticide use. In this study, the efficacy of mating disruption techniques against C. gnidiella was tested, as well as the effect of these methods on pesticide use and damage to clusters when the method was employed against both of the pests in wine grapes. Comparisons were made between plots treated with (1) L. botrana mating disruption pheromone, (2) L. botrana and C. gnidiella mating disruption pheromones and (3) control plots. A significant difference in the number of clusters infested with the developmental stages of the moths was seen between pheromone-treated plots and controls, while no such difference was observed between plots treated with one versus two pheromones. A similar pattern was observed in the number of insecticide applications; the greatest number of applications was used in control plots, followed by plots treated with L. botrana mating disruption pheromone and by plots treated with pheromones against both pests, in which no pesticides were applied.