Comparing and contrasting development and reproductive strategies in the pupal hyperparasitoids Lysibia nana and Gelis agilis (Hymenoptera: Ichneumonidae)

In most animals, the optimal phenotype is determined by trade-offs in life-history traits. Here, I compare development and reproductive strategies in two species of solitary secondary hyperparasitoids, Lysibia nana and Gelis agilis, attacking pre-pupae of their primary parasitoid host, Cotesia glomerata. Parasitoid larvae of both species exploit a given amount of host resources with similar efficiency. However, adults exhibit quite different reproductive strategies. Both species are synovigenic, and female wasps emerge with no mature eggs. However, G. agilis must first host-feed to produce eggs, while L. nana does not host-feed but mobilizes internal resources carried over from larval feeding to initiate oogenesis. Further, G. agilis is wingless, produces large eggs, has a long life-span, and generates only small numbers of progeny per day, whereas these traits are reversed in L. nana. Given unlimited hosts, the fecundity curve in L. nana was “front-loaded,” whereas in G. agilis it was depressed and extended over much of adult life. In L. nana (but not G. agilis), wasps provided with honey but no hosts lived significantly longer than wasps provided with both honey and hosts. Differences in the fecundity curves of the two hyperparasitoids are probably based on differing costs of reproduction between them, with the wingless G. agilis much more constrained in finding hosts than the winged L. nana. Importantly, L. nana is known to be a specialist hyperparasitoid of gregarious Cotesia species that pupate in exposed locations on the food plant, whereas Gelis sp. attack and develop in divergent hosts such as parasitoid cocoons, moth pupae and spider egg sacs. Consequently, there is a strong match between brood size in C. glomerata and egg production in L. nana, but a mismatch between these parameters in G. agilis.

Intrinsic competition and its effects on the survival and development of three species of endoparasitoid wasps

In natural systems, pre-adult stages of some insect herbivores are known to be attacked by several species of parasitoids. Under certain conditions, hosts may be simultaneously parasitized by more than one parasitoid species (= multiparasitism), even though only one parasitoid species can successfully develop in an individual host. Here, we compared development, survival, and intrinsic competitive interactions among three species of solitary larval endoparasitoids, Campoletis sonorensis (Cameron) (Hymenoptera: Ichneumonidae), Microplitis demolitor Wilkinson, and Microplitis croceipes (Cresson) (Hymenoptera: Braconidae), in singly parasitized and multiparasitized hosts. The three species differed in certain traits, such as in host usage strategies and adult body size. Campoletis sonorensis and M. demolitor survived equally well to eclosion in two host species that differed profoundly in size, Pseudoplusia includens (Walker) and the larger Heliothis virescens (Fabricius) (both Lepidoptera: Noctuidae). Egg-to-adult development time in C. sonorensis and M. demolitor also differed in the two hosts. Moreover, adult body mass in C. sonorensis (and not M. demolitor) was greater when developing in H. virescens larvae. We then monitored the outcome of competitive interactions in host larvae that were parasitized by one parasitoid species and subsequently multiparasitized by another species at various time intervals (0, 6, 24, and 48 h) after the initial parasitism. These experiments revealed that M. croceipes was generally a superior competitor to the other two species, whereas M. demolitor was the poorest competitor, with C. sonorensis being intermediate in this capacity. However, competition sometimes incurred fitness costs in M. croceipes and C. sonorensis, with longer development time and/or smaller adult mass observed in surviving wasps emerging from multiparasitized hosts. Our results suggest that rapid growth and large size relative to competitors of a similar age may be beneficial in aggressive intrinsic competitio

D0-brane tension in string field theory

We compute the D0-brane tension in string field theory by representing it as a tachyon lump of the D1-brane compactified on a circle of radius $R$. To this aim, we calculate the lump solution in level truncation up to level L=8. The normalized D0-brane tension is independent on $R$. The compactification radius is therefore chosen in order to cancel the subleading correction $1/L^2$. We show that an optimal radius $R^*$ indeed exists and that at $R^*$ the theoretical prediction for the tension is reproduced at the level of $10^{-5}$. As a byproduct of our calculation we also discuss the determination of the marginal tachyon field at $R\to 1$.Comment: 13 pages, 3 Eps figure

Non-Commutative Instantons and the Seiberg-Witten Map

We present several results concerning non-commutative instantons and the Seiberg-Witten map. Using a simple ansatz we find a large new class of instanton solutions in arbitrary even dimensional non-commutative Yang-Mills theory. These include the two dimensional ``shift operator'' solutions and the four dimensional Nekrasov-Schwarz instantons as special cases. We also study how the Seiberg-Witten map acts on these instanton solutions. The infinitesimal Seiberg-Witten map is shown to take a very simple form in operator language, and this result is used to give a commutative description of non-commutative instantons. The instanton is found to be singular in commutative variables.Comment: 26 pages, AMS-LaTeX. v2: the formula for the commutative description of the Nekrasov-Schwarz instanton corrected (sec. 4). v3: minor correction

Localized tachyon condensation and G-parity conservation

We study the condensation of localized tachyon in non-supersymmetric orbifold {\C^2/\Z_n}. We first show that the G-parities of chiral primaries are preserved under the condensation of localized tachyon(CLT) given by the chiral primaries. Using this, we finalize the proof of the conjecture that the lowest-tachyon-mass-squared increases under CLT at the level of type II string with full consideration of GSO projection. We also show the equivalence between the $G$-parity given by $G=[jk_1/n]+ [jk_2/n]$ coming from partition function and that given by $G=\{jk_1/n\}k_2 -\{jk_2/n\}k_1$ coming from the monomial construction for the chiral primaires in the dual mirror picture.Comment: 12 pages, 2 figures, final form to appear in JHE

Parasitoid load affects plant fitness in a tritrophic system

Plants attacked by herbivorous insects emit volatile compounds that attract predators or parasitoids of the herbivores. Plant fitness increases when these herbivorous insects are parasitized by solitary parasitoids, but whether gregarious koinobiont parasitoids also confer a benefit to plant fitness has been disputed. We investigated the relationship between parasitoid load of the gregarious Cotesia glomerata (L.) (Hymenoptera: Braconidae), food consumption by larvae of their host Pieris brassicae L. (Lepidoptera: Pieridae), and seed production in a host plant, Brassica nigra L. (Brassicaceae), in a greenhouse experiment. Plants damaged by caterpillars containing single parasitoid broods produced a similar amount of seeds as undamaged control plants and produced significantly more seeds than plants with unparasitized caterpillars feeding on them. Increasing the parasitoid load to levels likely resulting from superparasitization, feeding by parasitized caterpillars was significantly negatively correlated with plant seed production. Higher parasitoid brood sizes were negatively correlated with pupal weight of Cotesia glomerata, revealing scramble competition leading to a fitness trade-off for the parasitoid. Our results suggest that in this tritrophic system plant fitness is higher when the gregarious parasitoid deposits a single brood into its herbivorous host. A prediction following from these results is that plants benefit from recruiting parasitoids when superparasitization is prevented. This is supported by our previous results on down-regulation of synomone production when Brassica oleracea was fed on by parasitized caterpillars of P. brassicae. We conclude that variable parasitoid loads in gregarious koinobiont parasitoids largely explain existing controversies about the putative benefit of recruiting these parasitoids for plant reproduction

Comments on Noncommutative Sigma Models

We review the derivation of a noncommutative version of the nonlinear sigma model on \CPn and it's soliton solutions for finite $\theta$ emphasizing the similarities it bears to the GMS scalar field theory. It is also shown that unlike the scalar theory, some care needs to be taken in defining the topological charge of BPS solitons of the theory due to nonvanishing surface terms in the energy functional. Finally it is shown that, like its commutative analogue, the noncommutative \CPn-model also exhibits a non-BPS sector. Unlike the commutative case however, there are some surprises in the noncommutative case that merit further study.Comment: 22 pages, 4 figures, LaTeX (JHEP3), Minor changes, Discussion expanded and references adde

Quasi-localized states on noncommutative solitons

We consider noncommutative gauge theories which have zero mass states propagating along both commutative and noncommutative dimensions. Solitons in these theories generically carry U(m) gauge group on their world-volume. From the point of view of string theory, these solitons correspond to ``branes within branes''. We show that once the world-volume U(m) gauge theory is in the Higgs phase, light states become quasi-localized, rather than strictly localized on the soliton, i.e. they mix with light bulk modes and have finite widths to escape into the noncommutative dimensions. At small values of U(m) symmetry breaking parameters, these widths are small compared to the corresponding masses. Explicit examples considered are adjoint scalar field in the background of a noncommutative vortex in U(1)-Higgs theory, and gauge fields in instanton backgrounds in pure gauge noncommutative theories.Comment: 27 pages, references and comments added, final version to appear in JHE

Transmogrifying Fuzzy Vortices

We show that the construction of vortex solitons of the noncommutative Abelian-Higgs model can be extended to a critically coupled gauged linear sigma model with Fayet-Illiopolous D-terms. Like its commutative counterpart, this fuzzy linear sigma model has a rich spectrum of BPS solutions. We offer an explicit construction of the degree$-k$ static semilocal vortex and study in some detail the infinite coupling limit in which it descends to a degree$-k$ \C\Pk^{N} instanton. This relation between the fuzzy vortex and noncommutative lump is used to suggest an interpretation of the noncommutative sigma model soliton as tilted D-strings stretched between an NS5-brane and a stack of D3-branes in type IIB superstring theory.Comment: 21 pages, 4 figures, LaTeX(JHEP3