New record in the Hawaiian Islands of Orasema minutissima (Hymenoptera: Eucharitidae), an ant-parasitic wasp and a potential biocontrol agent against the Little Fire Ant, Wasmannia auropunctata (Hymenoptera: Formicidae)

Orasema minutissima Howard (Hymenoptera: Eucharitidae) is recorded fromthe Hawaiian Islands for the first time. It has been established on the island of Hawai?isince at least 2019. The wasp is a parasitoid of the immature stages of Pheidole andWasmannia (Formicidae: Myrmicinae), both of which are significant pests on several ofthe Hawaiian Islands. Already found in substantial numbers, the wasp is a potential biological control agent for Wasmannia auropunctata, the Little Fire Ant.Fil: Heraty, John Michael. University of California; Estados UnidosFil: Rogers, Valle D.. University of California; Estados UnidosFil: Johnson, M. Tracy. Institute of Pacific Islands Forestry; Estados UnidosFil: Perreira, Williams D.. No especifíca;Fil: Baker, Austin J.. University of California; Estados UnidosFil: Bitume, Ellyn. Institute of Pacific Islands Forestry; Estados UnidosFil: Murray, Elizabeth. Washington State University; Estados UnidosFil: Varone, Laura. Fundación para el Estudio de Especies Invasivas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Heritability and Artificial Selection on Ambulatory Dispersal Distance in Tetranychus urticae: Effects of Density and Maternal Effects

Dispersal distance is understudied although the evolution of dispersal distance affects the distribution of genetic diversity through space. Using the two-spotted spider mite, Tetranychus urticae, we tested the conditions under which dispersal distance could evolve. To this aim, we performed artificial selection based on dispersal distance by choosing 40 individuals (out of 150) that settled furthest from the home patch (high dispersal, HDIS) and 40 individuals that remained close to the home patch (low dispersal, LDIS) with three replicates per treatment. We did not observe a response to selection nor a difference between treatments in life-history traits (fecundity, survival, longevity, and sex-ratio) after ten generations of selection. However, we show that heritability for dispersal distance depends on density. Heritability for dispersal distance was low and non-significant when using the same density as the artificial selection experiments while heritability becomes significant at a lower density. Furthermore, we show that maternal effects may have influenced the dispersal behaviour of the mites. Our results suggest primarily that selection did not work because high density and maternal effects induced phenotypic plasticity for dispersal distance. Density and maternal effects may affect the evolution of dispersal distance and should be incorporated into future theoretical and empirical studies

Genetic and environmental contributions to dispersal distance in the two-spotted spider mite, Tetranychus urticae

Dispersal, the movement of individuals leading to gene flow, is a life-history trait found in virtually all organisms. Understanding the mechanisms behind why some individuals move when others remain is crucial to the study of population dynamics and conservation biology. Dispersal is comprised of three phases: emigration, transfer, and settlement. While emigration is well studied, the causes of differing dispersal distances resulting from decisions made at each of these phases are less well investigated. In this thesis, we attempted to distinguish genetic mechanisms of dispersal distance and to quantify plastic responses to different environmental and individual condition. To achieve this goal, we first attempted two different methods of artificial selection: one experiment on emigration and another on dispersal distance. While unable to produce differently dispersing lines in either of these experiments, the results revealed the importance of different environmental factors on dispersal decisions, i.e. the importance of phenotypic plasticity in the expression of this trait. We then performed experiments investigating the effects of population density, genetic relatedness, and maternal density on dispersal distance and the shape of the dispersal kernel. We found that increases in population density and relatedness increased dispersal distances, and that relatedness increased the distance traveled by the furthest moving 10% of individuals. We also found that in general, maternal and even grand-maternal density can influence the distance at which offspring will disperse, almost regardless of the offspring’s own environment. Our results contribute to the field of dispersal ecology by demonstrating that dispersal distance, in addition to emigration, can be affected by the interaction between external environmental factors (context-dependent dispersal) and the phenotypic condition of the individual (condition-dependent dispersal). We propose additional experiments to further clarify and augment the results of this thesis. Finally, we suggest that these results can be used in predictive modeling to know how a population might disperse when faced with differing environments. Thus, our results are useful in terms of predicting dispersal behavior by species undergoing range expansion, and for conservation biologists attempting to rescue populations that are affected by habitat fragmentation.(BIOL 3) -- UCL, 201

Data from: Establishment of the wasp Tetramesa romana for biological control of Arundo donax in northern California and the role of release plot manipulation

Arundo donax is a non-native, invasive large-statured grass of riparian systems in the southwestern U.S.A., including the Sacramento and San Joaquin River watersheds of northern California and the Sacramento-San Joaquin Delta. In 2017, the shoot tip-galling wasp Tetramesa romana was released at nine sites, three in each region. Shoots in some release plots were manipulated prior to release by cutting to ground or pruning to 1 m height, while others were left uncut. One year later, exit holes made by emerging adult wasps were found at two of nine sites. Exit hole density per main shoot length was 16-fold higher on regrowth shoots in ground-cut plots than in uncut plots. An additional plot manipulation study at two other sites found that exit hole density per shoot length was 19-fold higher in plots that were double-cut (cut to ground and regrowth pruned) than in single-cut plots. By 2023, T. romana was established at eight sites spanning both river watersheds and their Delta with dispersal up to 6.4 km, based on dissection of shoots, multi-year counts of exit holes and galls, and trapping of adult T. romana with sticky traps. The abundance of T. romana may be limited in northern California by low annual heat unit accumulation. The results show that physical manipulation of host plants improves short-term establishment and demonstrate the importance of using multiple monitoring methods to determine long-term establishment.</p

Density and genetic relatedness increase dispersal distance in a subsocial organism

Although dispersal distance plays a major role in determining whether organisms will reach new habitats, empirical data on the environmental factors that affect dispersal distance are lacking. Population density and kin competition are two factors theorised to increase dispersal distance. Using the two-spotted spider mite as a model species, we altered these two environmental conditions and measured the mean dispersal distance of individuals, as well as other attributes of the dispersal kernel. We find that both density and relatedness in the release patch increase dispersal distance. Relatedness, but not density, changes the shape of the dispersal kernel towards a more skewed and leptokurtic shape including a longer 'fat-tail'. This is the first experimental demonstration that kin competition can shape the whole distribution of dispersal distances in a population, and thus affect the geographical spread of dispersal phenotypes

Comparative Transcriptomic Analysis Reveals Molecular Profiles of Central Nervous System in Maternal Diapause Induction of Locusta migratoria

Egg diapause in Locusta migratoria L. (Orthoptera: Acridoidea) is believed to be influenced by maternal photoperiod. However, the molecular mechanism regulating the phenomenon of maternal diapause induction is unclear. Here we performed transcriptomic analyses from the central nervous system (CNS) of migratory locusts under long and short photoperiods to identify differentially expressed genes (DEGs) related to diapause induction. There were total of 165750 unigenes from 569491 transcripts, and 610 DEGs were obtained in S_CNS (CNS of short photoperiod treated locusts) vs. L_CNS (CNS of long photoperiod treated locusts). Of these, 360 were up-regulated, 250 were down-regulated, and 84 DEGs were found to be related to FOXO signaling pathways, including citrate cycle/TCA cycle, glycolysis/ gluconeogenesis, oxidative phosphorylation, and PI3K-Akt. The qRT-PCR validation of mRNA expression of 12 randomly selected DEGs showed consistency with transcriptome analysis. Furthermore, the takeout gene thought to be involved in circadian rhythm was cloned and used for RNAi to observe its function in maternal diapause induction. We found that the mRNA level of Lm-takeout was significantly lower in dstakeout treatments as compared to the control under both long and short photoperiods. Similarly, the offspring diapause rate was significantly higher in dstakeout treatment as compared to the control only in short photoperiod. This shows that the Lm-takeout gene might be involved in the inhibition of maternal diapause induction of L. migratoria under short photoperiods. The present study provides extensive data of the CNS transcriptome and particular insights into the molecular mechanisms of maternal effects on egg diapause of L. migratoria. As well for the future, the researchers can explore other factors and genes that may promote diapause in insect species

Figure 3

Code to produce figure 3

Figure S4

Code to produce figure S4

Predicted means from ordinal regression (JH)

Predicted means from ordinal regression for juvenile density by habitat quality treatment combinations