Population synchrony and environmental variation: an experimental demonstration

Understanding the causes of population synchrony is an important issue for population management. Its study in field populations involves disentangling the effects of dispersal and correlated environmental noise. Here we report on an experimental investigation of the synchronizing effects of noise in closed laboratory populations of a soil mite, Sancassania berlesei . Mite life-histories are highly plastic with respect to resource availability (which is a function of food supply and population density). By varying the food supply we imposed environmental variation. We show that (a) population synchrony is a function of environmental synchrony, (b) perceived population synchrony depends on the life-history stage counted, and (c) average population synchrony tends to be lower than environmental synchrony: even when populations were supplied with food with a correlation of 1.0, the correlation between populations was 0.63 (bootstrapped 95%CI 0.54–0.71). This supports recent theoretical work suggesting that the Moran theorem (indicating that population synchrony equals environmental synchrony) generally overestimates the population synchrony of nonlinear systems.     

Setal variability of <Emphasis Type="Italic">Hydrozetes lemnae</Emphasis> and <Emphasis Type="Italic">H. thienemanni</Emphasis> (Acari: Oribatida: Hydrozetidae)

Setal variability and the other morphological characters of juvenile stages and adult of Hydrozetes lemnae (Coggi, 1897) and H. thienemanni Strenzke, 1943 were investigated. In the juveniles of both species the length and shape of some setae vary, especially in the gastronotic region, more so in H. lemnae, which is parthenogenetic and reproduces by thelytoky, than in H. thienemanni, which is dioecious. The former species usually has more thick setae in the anterior and medial regions of the gastronotum, especially in the larva, compared to the latter. In the juveniles of H. lemnae the prodorsal setae le and in are longer, and in the nymphs the gastronotal setae of the l-series are usually longer than in H. thienemanni. These species differ distinctly by the number of long setae in the posterior part of the nymphs; in H. lemnae three pairs of long setae occur, while in H. thienemanni only two pairs; the respective juvenile stages of H. lemnae are also smaller than those of H. thienemanni. In the adults the number of c-series setae varies, as seta c ₁ is lost, and in some individuals also seta c ₃, and only seta c ₂ remains.     

中国蚌螨属水螨1新种记述

记述了从我国浙江省淡水蚌中采到的蚌螨科Unionicolidae水螨1新种,壮肢蚌螨Unionicola（Anodontinatax）ischyropalpus sp．nov．,模式标本保存于南昌大学生物科学工程系。     

Exotic vs endemic biocontrol agents: would the real Stratiolaelaps miles (Berlese) (Acari: Mesostigmata: Laelapidae), please stand up?

The ability of introduced organisms to invade undisturbed native habitats is a major concern in conservation biology and has resulted in a re-evaluation of the introduction of exotic biocontrol agents, especially of generalist predators. One such agent is Stratiolaelaps miles (Berlese), a predatory mite described from Italy, known from throughout the Holarctic, and apparently accidentally introduced to other areas of the world, including Australia. Initial investigations revealed that putative S. miles could be found in both disturbed and relatively pristine habitats in Queensland, Australia. However, analysis of the mitochondrial DNA of five populations showed most to be highly divergent genetically. Subsequent morphological analysis established two species groups: the lamington-group from cool-temperate to subtropical rainforests in Eastern Australia and the more eurytopic miles-group with a cosmopolitan distribution. We describe two new species from each of these complexes (Stratiolaelaps womersleyi, Stratiolaelaps lamington; Stratiolaelaps marilyn, Stratiolaelaps lorna, respectively), and resurrect Stratiolaelaps scimitus (Womersley), a species which often appears to have been confused with S. miles. Additionally, the large genetic distances among morphologically homogenous species in the miles-group suggest that the apparently cosmopolitan S. miles may be composed of a suite of cryptic species of potentially varying utility in biological control.     

山楂叶螨在苹果不同品种上的生长发育及繁殖

室内试验结果表明 ,山楂叶螨TetrancychusvienensisZacher在苹果不同品种上的生长发育和繁殖有较大的差异。其中在红星上存活率高 ,发育速度快 ,生殖力强 ;而在秦冠上存活率低、发育速度慢、生殖力低。对山楂叶螨种群年结龄构的分析表明 ,卵在种群中所占比例较高 ,而成虫所占比例甚低 ,建议在对其进行防治时选用杀卵力强的药剂     

Dwarf shrub and grass vegetation resistant to long‐term experimental warming while microarthropod abundance declines on the Falkland Islands

Dwarf shrubs are a dominant plant type across many regions of the Earth and have hence a large impact on carbon and nutrient cycling rates. Climate change impacts on dwarf shrubs have been extensively studied in the Northern Hemisphere, and there appears to be large variability in response between ecosystem types and regions. In the Southern Hemisphere, less data are available despite dwarf shrub vegetation being a dominant feature of southern South America and mountainous regions of the Southern Hemisphere. Here, we present the response of an Empetrum rubrum dwarf shrub and a Poa grass community to 12 years of experimental climate manipulation achieved using open top chambers on the Falkland Islands, a cold temperate island group in the South Atlantic. The dwarf shrub and grass vegetation did not change significantly in cover, biomass or species richness over the 12 years period in response to climate warming scenarios of up to 1°C reflecting annual warming levels predicted in this region for the coming decades. The soil microarthropod community, however, responded with declines in abundance (37%) under warming conditions in the grass community, but no such changes were observed in the dwarf shrub community. Overall, our data indicate that dwarf shrub communities are resistant to the levels of climate warming predicted over the coming decades in the southern South America region and will, therefore, remain a dominant driver of local ecosystem properties.     

Biology and phenology of the eriophyid mite, <Emphasis Type="Italic">Floracarus perrepae</Emphasis>, on its native host in Australia,Old World climbing fern, <Emphasis Type="Italic">Lygodium microphyllum</Emphasis>

The biology and phenology of the eriophyid mite, Floracarus perrepae Knihinicki and Boczek, a potential biological control agent of Lygodium microphyllum (Cav.) R. Br., was studied in its native range – Queensland, Australia. F. perrepae forms leaf roll galls on the subpinnae of L. microphyllum. It has a simple biology, with females and males produced throughout the year. The population was female biased at 10.5 to 1. The immature development time was 8.9 ± 0.1 and 7.0 ± 0.1 days; adult longevity was 30.6 ± 1.6 and 19.4 ± 1.2 days and mean fecundity per female was 54.5 ± 3.2 and 38.5 ± 1.6 eggs at 21 and 26 °C, all respectively. Field studies showed that the mite was active year round, with populations peaking when temperatures were cool and soil moisture levels were highest. Two species of predatory mites, Tarsonemus sp. and a species of Tydeidae, along with the pathogen Hirsutella thompsonii, had significant effects on all life stages of F. perrepae. Despite high levels of predators and the pathogen, F. perrepae caused consistent damage to L. microphyllum at all the field sites over the entire 2 years of the study.This revised version was published online in May 2005 with a corrected cover date.     

Have Genetic Trade-Offs in Host Use been Overlooked in Arthropods?

A popular hypothesis to explain the high degree of host specialisation observed among mites and insects is the existence of host-associated fitness trade-offs. According to this theory, adaptation to a host results in a relatively poorer performance on alternative hosts due to the antagonistic pleiotropic action of one or more genes. Evidence in favour of the genetic trade-off hypothesis is however scarce. Recent ecological work has shown that the optimisation of adult performance drives the evolution of host choice in at least some phytophagous insects. Yet, most ecological and evolutionary studies on host choice assume that females maximise their fitness by optimising offspring performance. In this paper, we investigate whether a general lack of attention for the role of adult performance in host choice may have diminished the chance of detecting genetic trade-offs. We reviewed the literature on genetic trade-offs and showed that most studies neglected host specific variation in adult performance. Moreover, studies that considered both adult and offspring performance had a higher chance of detecting genetic fitness trade-offs. Our results also suggested that studies on asexual reproducing species tend to detect trade-offs more often than studies on obligate sexual reproducing species. We argue that future studies on genetic trade-offs should take all fitness parameters into account in order to be conclusive. This approach may reveal (i) that genetic trade-offs are more common than hitherto reported and/or (ii) that genetic trade-offs are more common, or more easily detected among asexual reproducing species like mites and aphids. Co-ordinating editor: Dr. F. Stuefer     

Structure and function of the gnathosoma of the mange mite,Psoroptes ovis

Mites of the genus Psoroptes (Acari: Psoroptidae) are obligate, non-burrowing, astigmatid ectoparasites of mammals. A detailed understanding of the morphology of the gnathosoma is an important step towards elucidation of the feeding behaviour of this mite and, hence, the pathology of psoroptic mange. Scanning and transmission electron microscopy were used to examine Psoroptes ovis (Hering) (syn. P. cuniculi). The gnathosoma is composed of an infracapitulum (hypostome), which forms the floor of an extended U-shaped pre-oral trough, bounded by laterally compressed palps and enclosing paired chelicerae. Distally, each palp terminates in a flap-like process and four tapered terminal sensillae. The floor of the infracapitulum is interrupted along its length by a dorsally projecting ridge. At the distal end of the infracapitulum are paired, grooved pseudorutellae and, between them, paired, ungrooved lateral lips. Between the lateral lips is a grooved, elongate labium. Medially, a pair of finger-like projections emanates from the paraxial walls of the palps and project anteriorly. Each chelicera is made up of fixed and mobile digits, with a cheliceral membranous fold articulating the two. The distal ends of both digits are chelated. For much of its length, the mobile cheliceral digit appears to lie within a fold formed by the infracapitular ridge, thereby creating a central channel between the chelicerae. It is suggested that this arrangement of elements may facilitate a two-way flow of liquid, where saliva flows down a central salivary canal and spills out onto the host's skin over the labium at the point where the chelated tips of the chelicerae meet and abrade the skin. Liquid food may move along the grooves of the pseudorutellae and then be sucked up a food canal formed by the paraxial walls of the palps and the outer wall of the chelicerae.     

Bulbs mycoflora and their relation with three stored product mites

The distribution of moulds on stored and field onion and garlic plants infested by bulb mites in Assiut area (Egypt) was studied using PDA medium at 28 °C. Among 40 host samples and the three mite species tested no significant difference was noted in the contamination by moulds. A total of 20 species appertaining to 11 genera were identified from the tested mites and their habitats. The predominant moulds on all samples were “storage moulds” from the genera Aspergillus (A. niger, A. versicolor)and Penicillium (P. chrysogenum, P. funiculosum,and ``field moulds' among which Alternaria, Cladosporium,Fusarium (and its teleomorphs) and Setosphaeria were encountered most frequently. One fungus well known facultative pathogen was obtained: Beauveria bassiana. The tested mites transferA. niger, N. haematococca, R. stolonifer andP. chrysogenum outside their bodies while, A. flavusand A. ochraceus transfer through their digestive tracts along with the foods. Individuals of all mites could survived till the end of the experiment on all fungal species tested except A. niger, A. ochraceus and A. sydowii.Among 48 isolates screened for their ability to produce chitinase, about 83% of the isolates could produce this enzyme. Most of the positive isolates (17 isolates) had moderate producers This revised version was published online in June 2006 with corrections to the Cover Date.