Species richness in macroalgae and macrofauna assemblages on Fucus serratus L. (Phaeophyceae) and Zostera marina L. (Angiospermae) in Skagerrak, Norway

The macrophytes Fucus serratus and Zostera marina form similar substrates for associated flora and fauna in shallow waters in Norway. While F. serratus forms a more or less continuous belt on rocky substrate along the coast, Z. marina forms disjunct populations on sandy or muddy bottoms. This study focused on the organisms associated with these two macrophytes in two localities in the Skagerrak region. In total, 130 taxa of epiphytic organisms were identified: 22 green algae, 41 red algae, 32 brown algae, eight diatoms and 27 sessile animals. One hundred and twenty-seven taxa of mobile macrofauna were registered. The dominant group was crustaceans, with amphipods as the order containing most species. Many species of both plants and animals preferred one or the other habitat. It is concluded that coastal macrophyte systems have high species diversity.     

Host instar suitability of Aphis gossypii (Hemiptera: Aphididae) for Lysiphlebus testaceipes (Hymenoptera: Braconidae) and parasitism effect on aphid life table

Lysiphlebus testaceipes (Cresson) (Hymenoptera: Braconidae, Aphidiinae) has constituted a well-studied parasitoid insect model, but very little is known about the host-instar suitability of aphid for the wasp so far. One of the hosts of L. testaceipes is Aphis gossypii Glover (Hemiptera: Aphididae). The latter is a serious aphid pest to vegetable production in Benin. Therefore, the objectives of our study were to: (1) examine the oviposition behavior of L. testaceipes on A. gossypii; (2) investigate the host-instar suitability of A. gossypii for L. testaceipes; and (3) compare the life table parameters of A. gossypii with aphids parasitized by L. testaceipes and unparasitized aphids (control). The study was conducted in a laboratory at 26 ± 1 °C in petri dishes and revealed that the parasitoid utilized up to seven stabbing stings to handle and oviposit, particularly in older A. gossypii. In aphids parasitized at the third instar, the net reproductive rate R _o as well as the intrinsic rate of natural increase r _m was significantly lower (2.119 ± 0.272 and 0.110 ± 0.018) compared to the control (15.529 ± 1.287 and 0.272 ± 0.008), respectively (p < 0.01).     

Migration potential of the banana weevil Cosmopolites sordidus

• 1 The banana weevil Cosmopolites sordidus Germar (Coleoptera: Curculionidae) is a major pest in banana (Musa spp.) growing areas. The weevil is known to be relatively sedentary and closely associated with its host plant but little is known about the species' ability to migrate between banana fields and in nonhost habitats.
• 2 Mark–recapture experiments were conducted to assess the weevils' migration potential, possible differences between the sexes, and the relative attractiveness of pseudostem and pheromone baits.
• 3 One thousand two hundred marked weevils were released in the nonhost habitat at five distances (5, 10, 20, 40 and 70 m) from fresh pseudostem, and from pitfall traps baited with 45 mg of sordidin.
• 4 Two hundred males and 200 females were marked and released at five distances (5, 10, 20, 40 and 70 m) from the pheromone traps.
• 5 Distance and distance/bait interactions had a significant effect on recaptured weevils (binary logistic regression). The two baits were almost equally attractive to weevils in the range 0–10 m, whereas the pheromone was more attractive in the range 10–100 m.
• 6 Distance, bait and distance/bait interactions had a significant effect on the time elapsed from release to recapture (regression with life data) but the pattern observed was not consistent.
• 7 There was no significant difference between males and females with respect to distance or time elapsed from release to recapture.
• 8 The results obtained in the present study show that the migration potential of the banana weevil is greater than previously reported. This should be taken into account when new banana fields are established with clean planting material.

     

Carotenoids‐based reddish pelvic spines in nonreproducing female and male sticklebacks (Gasterosteus aculeatus) – Signalling social dominance?

Conspicuous ornaments are often considered a result of evolution by sexual selection. According to the social selection hypothesis, such conspicuous traits may also evolve as badges of status associated with increased boldness or aggression toward conspecifics in conflicts about ecological resources. This study tested predictions from the social selection hypothesis to explain evolution of conspicuous red color of the pelvic spines of the three‐spine stickleback (Gasterosteus aculeatus). Wild nonreproducing sticklebacks were presented to pairs of dummies which differed at their pelvic spines, having either (i) normal‐sized gray or red pelvic spines or (ii) normal‐sized gray or large red pelvic spines. The experimental tank was illuminated by white or green light, since green light impedes the sticklebacks’ ability to detect red color. The dummies moved slowly around in circles at each end of the experimental tank. We quantified the parameters (i) which of the two dummies was visited first, (ii) time taken before the first visit to a dummy, (iii) distribution of the focal sticklebacks in the two zones close to each of the two dummies and in the neutral zone of the tank, (iv) close to which of the two dummies did the focal fish eat its first food‐piece, and (v) time spent until the first piece of food was eaten. This was carried out for 22 females and 29 males sticklebacks. The results suggested no effect of the color or size of the dummies’ pelvic spines, on none of the five behavioral parameters. Moreover, neither the color of the pelvic spines of the focal sticklebacks themselves (as opposed to redness of the dummies’ spines) nor their body length was associated with behavior toward the dummies. Thus, this study did not support predictions from the social selection hypothesis to explain evolution of red pelvic spines in sticklebacks.     

Spatial and temporal distribution of bioclimatic potential for the Codling moth and the Colorado potato beetle in Norway: model predictions versus climate and field data from the 1990s

Abstract 1 Based on climate data from a network of agrometeorological stations in Norway, the effects of current and future climate regimes on the spatial and temporal distribution of the Codling moth (Cydia pomonella) and the establishment potential of the Colorado potato beetle (Leptinotarsa decemlineata) were investigated. 2 The study was accomplished using climex , a dynamic climate matching‐ and climate response estimation model, which predicts potential distribution of an organism based on its known geographical distribution. 3 Validation of the climex model predictions for C. pomonella against field data on spatial distribution of the species in Norway resulted in a refined set of climate response parameters for C. pomonella. Temporal occurrence of C. pomonella seems to be affected by climate (temperature) and insecticide treatment against the Apple fruit moth (Argyresthia conjugella) in the previous season. 4 Climate change scenarios (0.1 °C increase per degree in latitude in daily maximum and minimum temperatures) indicated an extension of the potential geographical range for C. pomonella, and 23 new locations were found favourable for its long‐term survival. The abundance and pest status of C. pomonella could increase dramatically in those locations where the species is already established. 5 Leptinotarsa decemlineata would only temporarily find suitable climate conditions in Norway and hence only be able to establish interim populations in a few regions under current climate conditions. Climate change scenarios for L. decemlineata indicated that the species would be able to establish as far north as 64°N, mainly in the inland of eastern Norway. 6 In general, the methods applied support the process of decreasing the uncertainty both in our knowledge about the pests themselves and about the environment, which are crucial elements in predicting whether a species is able to establish in a new area.