Lack of field-based recruitment to carbohydrate food in the Korean yellowjacket, <Emphasis Type="Italic">Vespula koreensis</Emphasis>

We investigated field-based recruitment via visual, chemical and acoustic cues provided by conspecific wasps on carbohydrate feeders in Vespula koreensis. A wild colony nest was excavated and artificially installed in a field site. Naïve foragers were individually marked and trained to an experimental feeder. We conducted three separate experiments in which foragers were presented with feeder dishes with different cue intensities. For the first, a different number of decoys were posed as if feeding (visual cue). In the second, dishes had been previously visited by different numbers of individuals, thus presenting different concentrations of a possible food site marking substance (chemical cue). In the third, each dish was placed in front of a covered flask with a different number of nestmates inside (acoustic cue combined with body-odor cue). We observed no social facilitation or social inhibition due to any of the experimental cues. Previous studies in Vespula species have shown a variety of foraging strategies ranging from local enhancement to local inhibition. Field-based recruitment mechanisms in yellowjackets may have evolved independently in different lineages.     

Hybrid origin of Baltic salmon-specific parasite Gyrodactylus salaris: a model for speciation by host switch for hemiclonal organisms

Host switching explains the high species number of ectoparasitic, viviparous, mainly parthenogenetic but potentially hermaphroditic flatworms of the genus Gyrodactylus. The starlike mitochondrial phylogeny of Gyrodactylus salaris suggested parallel divergence of several clades on grayling (also named as Gyrodactylus thymalli) and an embedded sister clade on Baltic salmon. The hypothesis that the parasite switched from grayling to salmon during the glacial diaspora was tested using a 493-bp nuclear DNA marker ADNAM1. The parasites on salmon in lakes Onega and Ladoga were heterozygous for divergent ADNAM1 alleles WS1 and BS1, found as nearly fixed in grayling parasites in the White Sea and Baltic Sea basins, respectively. In the Baltic salmon-specific mtDNA clade, the WS/BS heterozygosity was maintained in 23 out of the 24 local clones. The permanently heterozygous clade was endemic in the Baltic Sea basin, and it had accumulated variation in mtDNA (31 variable sites on 1600 bp) and in the alleles of the nuclear locus (two point mutations and three nucleotide conversions along 493 bp). Mendelian shuffling of the nuclear alleles between the local clones indicated rare sex within the clade, but the WS/BS heterozygosity was lost in only one salmon hatchery clone, which was heterozygous WS1/WS3. The Baltic salmon-specific G. salaris lineage was monophyletic, descending from a single historical hybridization and consequential host switch, frozen by permanent heterozygosity. A possible time for the hybridization of grayling parasite strains from the White Sea and Baltic Sea basins was during the Eemian interglacial 132 000 years bp. Strains having a separate divergent mtDNA observed on farmed rainbow trout, and on salmon in Russian lake Kuito were suggested to be clones derived from secondary and tertiary recombination events.     

Influence of diversity and road access on palm extraction at landscape scale in SE Ecuador

The relationship between biodiversity and the activities of small-scale farmers remains poorly understood despite its importance for conservation. In tropical forest areas farmers often include extraction of forest products in their subsistence strategies, and it has been suggested that factors such as market access and diversity levels influence people’s use of forest products. To investigate these relationships, we studied the use of palms in five villages inhabited by colonists and indigenous Shuar in the lower montane forest in south-eastern Ecuador by means of interviews and line transects around the villages. We found that use of palms was not driven by the diversity of palms available in the forest surrounding each village. Instead, the most important factor seemed to be lack of market access so in villages furthest away from the nearest road people used more palm products for their subsistence life compared to villages closer to the road. Forests around more remote villages had higher utility levels when evaluated on the basis of the villagers’ use of palms, despite lower levels of palm diversity and richness in these forests. The lower diversity levels may reflect past human activity or ecological factors, or a combination of both. In either case, our results show that forests with higher diversity levels are not necessarily more valuable to local people compared to less diverse forests. Instead, socio-economic factors such as market access may be more important in shaping people’s relationship with the natural environment.     

Coevolution between the large hawk‐cuckoo (Cuculus sparverioides) and its two sympatric Leiothrichidae hosts: evidence for recent expansion and switch in host use?

Obligate brood parasites only account for 1% of birds in the world, but utilize a great variety of avian species as hosts. Host switch theory predicts that parasites should shift from one host to another during the long‐term arms race with hosts whenever such a shift would be facilitated by similarity in ecology and distribution. However, few studies have been conducted to address this puzzle because it is extremely difficult for humans to witness such host shifts during the long‐lasting process of evolution. Here we adopted an alternative way to understand host switch behaviour of brood parasites by comparing egg colour variation, cuckoo egg mimicry and egg recognition capacity between two sympatric hosts, the Chinese babax (Babax lanceolatus) and the white‐browed laughing thrush (Garrulax sannio), which are both parasitized by the large hawk‐cuckoo (Cuculus sparverioides). The babax lays dark blue eggs whilst the laughing thrush lays white to pale blue eggs, and the large hawk‐cuckoo parasitizes them by laying eggs that optimally match laughing thrush eggs according to avian vision. The laughing thrush possesses a greater capacity of egg recognition than the babax because it rejected all non‐mimetic eggs while the babax is an intermediate rejecter. Furthermore, all the nest characteristics measured were similar in these two host species with no statistical significant differences. These results are consistent with the hypothesis that the white‐browed laughing thrush is the original and main host species that has a longer coevolutionary interaction with the large hawk‐cuckoo than the Chinese babax, which is a recent host acquired through a host switch by the hawk‐cuckoo. We discuss the possible outcome of the interaction between the large hawk‐cuckoo and these two host species, and emphasize that host switch behaviour in brood parasites is more likely an adaptation to expand the range of host species rather than a change in host species favoring an increase in reproductive output. © 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, ●● , ●●–●●.     

The costs and benefits of multiple mating in a mostly monandrous wasp

The taxonomically widespread nature of polyandry remains a puzzle. Much of the empirical work regarding the costs and benefits of multiple mating to females has, for obvious reasons, relied on species that are already highly polyandrous. However, this makes it difficult to separate the processes that maintain the current level of polyandry from the processes that facilitate its expression and initiated its evolution. Here we consider the costs and benefits of polyandry in Nasonia vitripennis, a species of parasitoid wasp that is “mostly monandrous” in the wild, but which evolves polyandry under laboratory culture conditions. In a series of six experiments, we show that females gain a direct fecundity and longevity benefit from mating multiply with virgin males. Conversely, mating multiply with previously mated males actually results in a fecundity cost. Sexual harassment may also represent a significant cost of reproduction. Harassment was, however, only costly during oviposition, resulting in reduced fecundity, longevity, and disrupted sex allocation. Our results show that ecological changes, in our case associated with differences in the local mating structure in the laboratory can alter the costs and benefits of mating and harassment and potentially lead to shifts in mating patterns.     

The immune signaling pathways of Manduca sexta

Signal transduction pathways and their coordination are critically important for proper functioning of animal immune systems. Our knowledge of the constituents of the intracellular signaling network in insects mainly comes from genetic analyses in Drosophila melanogaster. To facilitate future studies of similar systems in the tobacco hornworm and other lepidopteran insects, we have identified and examined the homologous genes in the genome of Manduca sexta. Based on 1:1 orthologous relationships in most cases, we hypothesize that the Toll, Imd, MAPK-JNK-p38 and JAK-STAT pathways are intact and operative in this species, as are most of the regulatory mechanisms. Similarly, cellular processes such as autophagy, apoptosis and RNA interference probably function in similar ways, because their mediators and modulators are mostly conserved in this lepidopteran species. We have annotated a total of 186 genes encoding 199 proteins, studied their domain structures and evolution, and examined their mRNA levels in tissues at different life stages. Such information provides a genomic perspective of the intricate signaling system in a non-drosophiline insect.     

Natural selection drives leaf divergence in experimental populations of Senecio lautus under natural conditions

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Local control rates in stereotactic body radiotherapy (SBRT) of lung metastases associated with the biologically effective dose

AimTo evaluate dose differences in lung metastases treated with stereotactic body radiotherapy (SBRT), and the correlation with local control, regarding the dose algorithm, target volume and tissue density.BackgroundSeveral studies showed excellent local control rates in SBRT for lung metastases, with different fractionation schemes depending on the tumour location or size. These results depend on the dose distributions received by the lesions in terms of the tissue heterogeneity corrections performed by the dose algorithms.Materials and methodsForty-seven lung metastases treated with SBRT, using intrafraction control and respiratory gating with internal fiducial markers as surrogates (ExacTrac, BrainLAB AG), were calculated using Pencil Beam (PB) and Monte Carlo (MC) (iPlan, BrainLAB AG).Dose differences between both algorithms were obtained for the dose received by 99% (D_99%) and 50% (D_50%) of the planning treatment volume (PTV). The biologically effective dose delivered to 99% (BED_99%) and 50% (BED_50%) of the PTV were estimated from the MC results. Local control was evaluated after 24 months of median follow-up (range: 3–52 months).ResultsThe greatest variations (40.0% in ΔD_99% and 38.4% in ΔD_50%) were found for the lower volume and density cases. The BED_99% and BED_50% were strongly correlated with observed local control rates: 100% and 61.5% for BED_99% > 85 Gy and <85 Gy (p < 0.0001), respectively, and 100% and 58.3% for BED_50% > 100 Gy and <100 Gy (p < 0.0001), respectively.ConclusionsLung metastases treated with SBRT, with delivered BED_99% > 85 Gy and BED_50% > 100 Gy, present better local control rates than those treated with lower BED values (p = 0.001).     

Factors affecting female-biased sex ratio in a trap-nesting wasp, Trypoxylon malaisei

We examined the female-biased sex ratio of a trap-nesting wasp Trypoxylon malaisei considering the following factors: (1) local mate competition (LMC), (2) resource quality, (3) partial bivoltinism, and (4) presence of constrained females. The sex ratio (expressed as male ratio) at emergence was strongly female biased, i.e., 0.30 and 0.19, in terms of the number and investment, respectively. To evaluate the primary sex ratio, we analyzed the data from nests where all the offspring successfully emerged, excluding nests composed of single-sex offspring. The primary sex ratio was also female biased, at 0.33 and 0.21, in terms of the number and investment, respectively. LMC was highly responsible for the female-biased sex ratio because both the nonrandom oviposition sequence [females at inner cells and male(s) at outer cells] and earlier emergence of males allowed sib-matings to occur. In contrast, the other three factors little affected the female-biased sex ratio: the sex ratio was fairly constant when resource quality (nest size) varied, partial bivoltinism was extremely rare or absent, and constrained females were absent or did not reproduce at all. Received: June 19, 1998 / Accepted: January 18, 1999     

Performance of native grape phylloxera on host plants within and among terrestrial islands in Arizona, USA

In Arizona, USA, the canyon grape, Vitis arizonica Englemann, and grape phylloxera (Daktulosphaira vitifoliae Fitch, Homoptera, Phylloxeridae) are distributed among mountain ranges that are surrounded by expanses of desert lacking Vitis habitat, thus forming a system of terrestrial islands. Both herbivore and host populations may have diverged genetically among mountain ranges under the influence of restricted gene flow and variable selection among sites. Herbivore adaptation to local hosts would be expected to ensue, with the potential to promote divergence, both in traits under selection and by further reducing the probability of interisland colonization. To test the hypothesis that phylloxera are adapted to local hosts, demographic components of fitness of field-collected native grape phylloxera were measured in the greenhouse on vines of V. arizonica that were categorized as either natal, neighboring, and or isolated hosts. There was no evidence for greater adaptation to natal or neighboring hosts but there were significant interactions between herbivore and host treatments in one experiment. There was genetic variation for gall formation among six clones tested. Though a failure to detect local adaptation could have resulted from low statistical power, benign experimental conditions, or inadequate genetic variation, the divergence of isolated grape populations is suggested to have been insufficient to promote local adaptation in grape phylloxera at the level of isolated mountain ranges. It is further suggested that, within populations, adaptation to individual host plants could be forestalled by selection for ’general purpose genotypes’ through wind-borne displacement of colonizers into the unpredictable environment of a heterogeneous array of hosts. In addition, short-term extinction/colonization dynamics could promote gene flow such that time is insufficient for adaptive mutations or gene combination to arise. Received: 26 December 1998 / Accepted: 24 May 1999