The MOTOM toolbox:
•Allows complete software control of the Optotrak system.•Runs on both 32- and 64-bit systems with reverse compatibility.•Includes additional functions to help simplify the ...experimental code.
We present a Matlab toolbox that allows the user to control and collect data using Northern Digital's Optotrak system. The Optotrak is a modular motion capture system, which tracks the positions of infrared markers. It also supports grouping markers together as a single body. The body's position, orientation as well as all the marker position data can be obtained simultaneously. The installation, set-up and alignment procedures are highly automated, and thus require minimal human interaction. We provide additional scripts, functions, documentation and examples to help experimenters integrate the Optotrak system into experiments using recent 64-bit computers and existing Matlab toolboxes.
Parasitoid lifespan is influenced by nutrient availability, thus the lifespan of parasitoids that rely on their hosts for nutritional resources (either via host feeding or by consuming honeydew) ...should vary with host density. We assessed the survival and reproduction of one such species, Aphelinus certus—a parasitoid of the soybean aphid, Aphis glycines—over a range of host densities using a laboratory assay. We found a positive, asymptotic relationship between host density and the lifespan and fecundity of A. certus that was supported by a traditional survivorship analysis as well as a logistic model. Parasitoids from this assay were also used to develop a wing wear index relating setae damage to parasitoid age. This index was used to estimate the life expectancy of field-collected parasitoids, which was shorter than the life expectancy of laboratory-reared female parasitoids. Finally, host-density-dependent parasitoid lifespan was incorporated into a coupled-equations matrix population model that revealed that decreasing the degree of host density dependence leads to higher equilibrium host densities and changes in the quality of equilibrium (e.g. stable limit cycles). These results detail the relatively unstudied phenomenon of host-density-dependent parasitoid lifespan and suggest that differences between laboratory- and field-determined parasitoid life expectancy have important implications for population dynamics and the biological control of insects.
We consider the possibility of an extensive invasional meltdown occurring in central North America involving eleven Eurasian species. The scenario begins with the potential co-facilitation between ...the European earthworm Lumbricus terrestris and European buckthorn, Rhamnus cathartica. Once introduced, European buckthorn has served as the overwintering host for two important invasive crop pests, oat crown rust, Puccinea coronata and the soybean aphid, Aphis glycines. The spread of R. cathartica itself may have been aided by seed dispersal by the European starling, Sturnus vulgaris, and the presence of L. terrestris has likely facilitated the invasion of Bipalium adventitium, an Asian predatory flatworm that specializes on earthworms. Beyond this, the soybean aphid is consumed by a number of introduced species, including the lady beetle Harmonia axyridis, the ground beetle Agonum muelleri and the parasitoid Aphelinus certus. We hypothesize that the presence of soybean aphid increases regional abundances of these species. We discuss both the evidence for this multi-species invasional meltdown scenario and potential implications of meltdown dynamics for invasive species management. The particular management issues that we discuss are: (1) opportunities for managing multiple invasive species simultaneously by targeting facilitator species, and (2) implications of meltdown dynamics for biological control introductions against the soybean aphid.
Parasitoids used as biological control agents often parasitize more than a single host species and these hosts tend to vary in suitability for offspring development. The population dynamics of ...parasitoids and hosts may be altered by these interactions, with outcomes dependent on the levels of suitability and acceptance of both host species. Parasitism of individuals of an unsuitable host species may indirectly increase populations of a suitable host species if eggs laid into unsuitable hosts do not develop into adult parasitoids. In this case, the unsuitable host is acting as an egg sink for parasitoids and this can reduce parasitism of suitable hosts under conditions of egg limitation. We studied parasitoid‐mediated indirect interactions between two aphid hosts, Aphis glycines (the soybean aphid) and A. nerii (the milkweed, or oleander aphid), sharing the parasitoid Aphelinus certus. While both of these aphid species are accepted by A. certus, soybean aphid is a much more suitable host than milkweed aphid is. We observed a drastic reduction of parasitoid offspring production (45%) on the suitable host in the presence of the unsuitable host in microcosm assays. Aphelinus certus females laid eggs into the unsuitable hosts (Aphis nerii) in the presence of the suitable host leading to egg and/or time limitation and reduced fitness. The impact of these interactions on the equilibrium population sizes of the three interacting species was analyzed using a consumer–resource modeling approach. Both the results from the laboratory experiment and the modeling approaches identified apparent predation between soybean aphid and milkweed aphid, in which milkweed aphid acts as a sink for parasitoid eggs leading to an increase in the soybean aphid population. The presence of soybean aphids had the opposite effect on milkweed aphid populations as it supported increases in parasitoid abundance and thus reduced the fitness and abundance of this aphid species.
We investigated indirect interactions that can occur when a single parasitoid species attacks two aphid species that differ in their suitability for parasitism. Laboratory studies showed that the presence of unsuitable hosts indirectly increased populations of suitable hosts through an egg sink experienced by the shared parasitoid, and a parameterized population model confirmed and extended this result to longer time scales. These results show how such indirect effects can affect community structure and affect biological control interactions.
The cascading effects of microbe–plant symbioses on the second trophic level, such as phytophagous insects, have been most studied. However, few studies have examined the higher third trophic level, ...i.e., their natural enemies. We investigated the effects of the symbiotic associations between an arbuscular mycorrhizal (AM) fungus, Rhizophagus irregularis (Glomerales: Glomeraceae), a nitrogen-fixing bacterium, Bradyrhizobium japonicum (Rhizobiales: Bradyrhizobiaceae), and soybean, Glycine max (L.) Merr. (Fabaceae) on two natural enemies of the soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), the ladybird beetle Coleomegilla maculata (De Geer) (Coleoptera: Coccinellidae), and the parasitoid Aphelinus certus Yasnosh (Hymenoptera: Aphelinidae). We measured the growth and survival in the predator and parasitoid reared on aphids feeding on soybean inoculated seedlings. The rhizobium symbiosis alone was affected with a decreased rate of parasitoid emergence, presumably due to decreased host quality. However, number of mummies, sex-ratio, development time, and parasitoid size were all unaffected by inoculation. AM fungus alone or co-inoculated with the rhizobium was unaffected with any of the parameters of the parasitoid. For the predator, none of the measured parameters was affected with any inoculant. Here, it appears that whatever benefits the microbe–plant symbioses confer on the second trophic level are little transferred up to the third.
We have established ex situ assurance colonies of two endangered Panamanian harlequin frogs, Atelopus certus and Atelopus glyphus, but observed that males fought with each other when housed as a ...group. Housing frogs individually eliminated this problem, but created space constraints. To evaluate the potential stress effects from aggressive interactions when grouping frogs, we housed male frogs in replicated groups of one, two, and eight. We measured aggressive behavioral interactions and fecal glucocorticoid metabolite (GC) concentrations as indicators of stress in each tank. In both small and large groups, frogs initially interacted aggressively, but aggressive interactions and fecal GCs declined significantly after the first 2 weeks of being housed together, reaching the lowest levels by week 4. We conclude that aggressive interactions in same-sex groups of captive Atelopus may initially cause stress, but the frogs become habituated within a few weeks and they can safely be housed in same-sex groups for longer periods of time.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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•Soybean aphid resistance genes, Rag1 and Rag2, affected parasitism by wasp species.•Neither gene affected oviposition by Aphelinus glycinis or Aphelinus certus.•Both genes reduced ...parasitism by A. glycinis.•Rag1 did not effect parasitism by A. certus, but Rag2 reduced parasitism A. certus.•These wasps are nonetheless able to parasitize soybean aphid on resistant soybean.
The soybean aphid, Aphis glycines, is native to Asia, but during the last decade it has invaded North America, where it has spread to most soybean growing regions and become the most important insect pest of soybean. Current control of soybean aphid relies primarily on insecticides, but alternatives to insecticidal control are being explored, especially host plant resistance and biological control, which may interact positively or negatively. Research on host plant resistance to the soybean aphid has revealed six genes that affect resistance. We measured the impact of the two most studied resistance loci, Rag1 and Rag2, on two parasitoid species: Aphelinus glycinis, a recently described species from Asia, which is being introduced into the USA to control the soybean aphid, and Aphelinus certus, also from Asia but accidentally introduced into the USA. Resistance did not affect oviposition by either parasitoid species. However, resistance did reduce successful parasitism by A. glycinis, with each resistance allele causing a two-fold reduction in number of mummified aphids. The resistance alleles did not affect adult emergence, sex ratio, or the size of A. glycinis. For A. certus, the Rag1 resistance allele had no effect on parasitism, while the Rag2 resistance allele reduced parasitism four-fold. On the other hand, the Rag1 resistance allele increased the frequency of males among progeny and decreased female size of A. certus. Despite the reduction in parasitism, these parasitoids are nonetheless able to parasitize the soybean aphid on resistant soybean, which means that they should still contribute to the management of soybean aphid on resistant varieties.
► We model population dynamics of soybean aphid and its natural enemies using a mechanistic population model including a natural enemy unit module. ► The model provides a quantitative synthesis of ...the available literature on soybean aphid biology and ecology. ► The natural enemy unit standardizes the impact a species has on prey by relative voracity. ► Aphid populations are more strongly impacted by natural enemies than by host plant phenology and environmental conditions. ► The effect of predation is stronger than host plant phenology on numbers of overwintering aphids.
Soybean aphid (Aphis glycines) is a severe pest of soybean in North America with a diverse natural enemy guild. A large body of literature exists examining aspects of the biology and ecology of this species, but these studies have not been synthesized in a quantitative context, limiting the understanding of the relative importance of environmental and ecological factors in the population dynamics of this species. Existing models for population dynamics of A. glycines are geographically restricted, and do not incorporate host plant phenology or natural enemy impact on aphid population dynamics and phenology. In this paper, a mechanistic tritrophic population and phenology model is developed for this species, incorporating environmental cues, host plant cues and natural enemy dynamics. Individual natural enemy species differ with respect to prey consumption rates and foraging behaviours and may occur at different times in the lifecycle of a prey species in response to environmental cues, densities, or the availability of alternate prey. Additionally, the natural enemy complex of A. glycines differs in composition and abundance in different parts of the aphids range. Because of these factors, we developed a strategy to quantify impact of the natural enemy guild that would facilitate the incorporation of natural enemy complexes occurring at multiple locations. In order to standardize the impact of natural enemy guilds on prey species, we used the Natural Enemy Unit (NEU), where NEU is defined as the number of individuals of a predatory species that can kill 100 individual prey in 24h. After calibration of the NEU calculation to incorporate a type III functional response to prevent natural enemies from driving aphid populations to local extinction, the model performed very well in predicting the dynamics between populations of natural enemies and A. glycines when compared to field observations. Simulations suggest that natural enemy abundance impacts A. glycines abundance more strongly than environmental conditions, but host plant phenology also dramatically influences dynamics of this species.
Nine new stonefly species of the suborder Perlina from the Middle Permian Kostovaty locality, Udmurtia are described. Two species,
Boreoperlidium callopterus
Sinitshenkova sp. nov. and
B. certus
...Sinitshenkova sp. nov., belong to the family Eustheniidae and six species,
Properla incrassata
Sinitshenkova, sp. nov.,
P. umbrosa
Sinitshenkova, sp. nov., Kargaloperla fibrosa Sinitshenkova, sp. nov.,
K. queata
Sinitshenkova, sp. nov.,
K. gratum
Sinitshenkova, sp. nov., and
K. postica
Sinitshenkova, sp. nov., belong to the family Palaeoperlidae. Unusually great abundance and diversity of representatives of the suborder Perlina is discussed.
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