Elevation and experimental snowmelt manipulation affect emergence phenology and abundance of soil‐hibernating arthropods

1. Effects of climate change, such as higher average temperatures and earlier snowmelt, are already apparent, especially in alpine regions. However, community responses of functionally important arthropod taxa to changing climatic conditions are mostly unknown. 2. In this study, an earlier snowmelt was simulated at 15 plots along an elevational gradient in the German Alps. At each study site, soil emergence traps were established for sampling soil‐hibernating arthropods on earlier and control snowmelt treatments during the growing season. The abundance and emergence phenology of the five most common arthropod orders (Araneae, Coleoptera, Diptera, Hemiptera, Hymenoptera) were analysed, as well as the species richness of Coleoptera. 3. There was increasing abundance and species richness of Coleoptera along the elevational gradient, indicating that at higher altitudes more individuals and species hibernate in the soil. Abundances of Diptera also increased with elevation. By contrast, abundances of Hemiptera declined with increasing elevation, while abundances of Araneae and Hymenoptera did not show significant elevational patterns. Arthropods at higher elevations emerged, on average, 5 weeks later than arthropods at lower elevations, because of a longer‐lasting snow cover. The earlier snowmelt treatment resulted in higher abundances of Araneae and Hymenoptera compared with the control plots, indicating that the time of snowmelt influenced the abundance of predators, such as spiders or parasitic wasps, more than that of herbivores. 4. An earlier emergence of certain arthropod guilds and a change in relative abundance of guilds might desynchronise species interactions, leading to a possible loss of biodiversity.     

The influence of seed quality and pregermination treatment on cauliflower and cabbage transplant production and field growth

Seedling emergence and subsequent growth from untreated seeds and selected-germinated seeds which had been dried before sowing (low-moisture-content germinated (LMCG) seeds) were compared in cellular trays in a glasshouse and in the field following transplanting. Three seed lots of different quality of the same cultivar were used for cabbage and cauliflower. In all cases, seedling emergence was greater, earlier and more uniform from LMCG seed than that from untreated seeds. LMCG seed effectively eliminated the differences due to seed quality shown by untreated seeds at emergence suggesting an improvement in seed vigour as well as viability from the selection treatment. Higher quality seed and LMCG cauliflower seed led to larger curd weights and therefore an increase in marketable yield at harvest compared to that from lower quality seeds. However, differences in transplant uniformity due to seed quality and seed treatment had little impact of agronomic significance following transplanting.     

用性信息素预测棉铃虫发生期的可靠性

利用棉铃虫（Ｈｅｌｉｃｏｖｅｒｉｐａ ａｍｉｇｅｒａ）性信息素诱蛾,预测下一代棉铃虫的卵高峰,幼虫孵化高峰,通过田间调查印证是准确的,它比黑光诱蛾以及田间调查方法简便,省工省时,指导化学农药防治时间准确,经济效益明显。可为棉铃虫发生期预测预报增添一种新的有效方法。     

Emergence of adult female Sirex nigricornis F. and Sirex noctilio F. (Hymenoptera: Siricidae) coincides with a decrease in daily minimum and maximum temperature

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Consequence of emergence pattern on inbreeding risk in the aphid parasitoid Aphidius matricariae (Hymenoptera: Braconidae)

In insect parasitoids, mating strategy depends on mate availability and is influenced by the spatial and temporal emergence patterns of adults. For quasi-gregarious species, simultaneous emergence favors local mating and reduces search costs for partners while increasing the risk of inbreeding, particularly when only one female parasitizes the initial host patch. Consequently, in inbreeding sensitive species, mating on the place of adult emergence (patch mating) between siblings should be counter selected. In practice, the timing of male and female emergence and of their dispersal influences mate availability and can limit on patch mating. To test the role of these two factors, we analyzed the daily distribution of emergence and patch residence time of a cohort in the aphid parasitoid Aphidius matricariae (Hymenoptera: Braconidae). We observed that adult emergence is concentrated on the morning with males emerging on average before females with some overlaps. A more precise evaluation of emergence pattern within a brood suggests that brothers and sisters rarely emerge at the same time and rapid dispersal of males and females favors off-patch mating. The relationships between timing of emergence including differences between sex and consequences on inbreeding probability in these species are thus discussed.     

The relative importance of pre- and post-germination determinants for recruitment of an annual plant community on moving sandy land

• Background and Aims The relative importance of pre- and post-germination determinants for recruitment of natural plant communities is rarely explored. An annual plant community on moving sandy land was chosen for a case study. Answers to the following questions were sought: (a) Does recruitment of new individuals within the community of annual plants differ in time and space? (b) Is there spatial concordance between seed deposition, seedling emergence, survival and recruitment? (c) What are the direct and indirect effects of pre- and post-germination determinants on plant recruitment.• Methods An integrative approach combining investigation of natural recruitment processes with regression, correlation and path analyses was adopted. Data on seed deposition and seedling recruitment were collected by monitoring the number of seeds deposited in the top 5 cm of the soil and the numbers of seedlings emerged and recruited from all annual plants at sites to a range of distances from the existing shrub Artemisia halodendron (Asteraceae) in eight compass directions for two consecutive growing seasons.• Key Results Community-level recruitment was strongly affected by inter-annual rainfall variation and was highly site- and density-dependent. Low recruitment rate in this system was due to low emergence rate and low post-emergence survival rate. Of the pre- and post-germination determinants studied, it was the number of seedlings which emerged and the post-emergence survival rate that had the greatest direct effects on recruitment, with a combination of both variables explaining the majority of the variance (97 %) in recruitment.• Conclusions This study suggests that post-germination determinants (emergence and survival) rather than pre-germination determinants (seed deposition) substantially determined the final pattern of recruitment. Although the density of seeds deposited did not have a significant direct effect on recruitment, it contributed to observed variation in recruitment indirectly through density-dependent emergence of seedlings.     

Hatching from the sediment egg-bank,or aerial dispersing? – the use of mesocosms in assessing rotifer biodiversity

Rotifer emergence from dry billabong sediments was studied from 3 sites on the River Murray floodplain, near Wodonga, northern Victoria, Australia. The sites had different flood histories, ranging from annual to approximately 25-year flooding intervals. Half of each sediment type was sterilized by -radiation to contrast the contribution of recruitment from the egg bank with recruitment from passive dispersal. A series of mesocosms was employed to assess differences between treatments, i.e. sediment sterilization and flood history. Analysis by Canonical Correspondence Analysis and Similarity Percentages suggested that some species were passively dispersed. Of the 54 species colonizing after 35 days, four were undescribed, one was a new record to Australia, three species had previously been recorded only from Tasmania and five more were new to the study area. Overall, 22% of species were previously unrecorded from the study area. This suggests that habitat poor mesocosms, may be more successful in locating passively dispersed taxa than examination of natural temporary waters.     

Emergence of flies from overwintering populations of cabbage root fly pupae

ABSTRACT.

• 1 Once pupal diapause had been terminated, over-wintering cabbage root fly (Delia radicum (L.)) pupae from Wellesbourne required a further 14 days at 20°C for most of the flies to emerge.
• 2 There were considerable variations in the rates of fly emergence from thirteen populations of cabbage root fly pupae collected between latitudes 50° 42′ and 54° 59′ in England and Wales. These thirteen populations could be grouped into early-, intermediate- and late-emerging types. In the early-emerging type, flies emerged within 14 days at 20°C whereas in the late-emerging type emergence was protracted and was completed only after 100 days at 20°C in one population from Halsall, Lancashire. In the intermediateemerging type, approximately two-thirds of the flies emerged within 14 days at 20° C, the remainder taking considerably longer.
• 3 The intermediate-emerging types could be just mixtures of the early- and late-emerging types.
• 4 Subjecting pupae to diapause-breaking temperatures (4°C) for up to 1 year failed to shorten the time to subsequent fly emergence in any of the populations.
• 5 Populations of early, intermediate- and late-emerging fies could be selected from a parental population, heterogeneous with respect to emergence, within one generation.
• 6 The type of emergence that occurred in a locality was not correlated with latitude.
• 7 Any models developed for forecasting the most appropriate time to apply insecticide in a locality will have to include information about the emergence pattern of the fly population in that locality.

     

Genetic variations and physical activity as determinants of limb bone morphology: an experimental approach using a mouse model

To gain insight into past human physical activity, anthropologists often infer functional loading history from the morphology of limb bone remains. It is assumed that, during life, loading had a positive, dose-dependent effect on bone structure that can be identified despite other effects. Here, we investigate the effects of genetic background and functional loading on limb bones using mice from an artificial selection experiment for high levels of voluntary wheel running. Growing males from four replicate high runner (HR) lines and four replicate nonselected control (C) lines were either allowed or denied wheel access for 2 months. Using μCT, femoral morphology was assessed at two cortical sites (mid-diaphysis, distal metaphysis) and one trabecular site (distal metaphysis). We found that genetic differences between the linetypes (HR vs. C), between the replicate lines within linetype, and between individuals with and without the so-called "mini-muscle" phenotype (caused by a Mendelian recessive gene that halves limb muscle mass) gave rise to significant variation in nearly all morphological indices examined. Wheel access also influenced femoral morphology, although the functional response did not generally result in enhanced structure. Exercise caused moderate periosteal enlargement, but relatively greater endocortical expansion, resulting in significantly thinner cortices and reduced bone area in the metaphysis. The magnitude of the response was independent of distance run. Mid-diaphyseal bone area and area moments, and trabecular morphology, were unaffected by exercise. These results underscore the strong influence of genetics on bone structure and the complexity by which mechanical stimuli may cause alterations in it.