Increases in drought and temperature associated with climate change may facilitate corresponding increases in the frequency and severity of insect population outbreaks (Hammond et al. 2001, Levine and Paige 2004, Hamilton et al. 2005, Dermody et al. 2008). The Plant Stress Hypothesis predicts that environmental stress increases a plant‟s susceptibility to insect herbivory by altering leaf chemistry and whole plant physiology (White 1984). Specifically, abiotic stress can cause a reduction in plant defense compounds and an increase in available nitrogen and digestible proteins relative to carbon availability (White 1984), leading to more palatable food for insect herbivores. Thus, the compounded effects of increased population outbreaks and environmental stress could lead to larger reductions in growth and production in natural and managed systems. It is therefore important to begin to understand how climate change will influence plant-herbivoreinteractions, especially in agriculture.
climate change may increase herbivore abundance indirectly. Dis- rupted phenological synchrony between predator and prey (Hance et al., 2007) may be one mechanism, another may be a reduction in plant production of chemical attractants (synomones) that recruit natural enemies, which then regulate herbivore numbers (Yuan et al., 2009). Alternatively, climate change may beneﬁt the prey and antagonist equally, with any increase in herbivore abundance merely supporting greater numbers of natural enemies and thus leading to no net change in populations (e.g., Chen et al., 2005). An integrated approach considering trophic interactions as an inte- gral part of an ecosystem comprising above- and belowground components will provide a more accurate estimation of climate change impacts. For example, a positive effect of root herbivores on folivores at higher temperatures may, if climate change positively affected antagonist efﬁcacy (e.g., Bezemer et al., 1998; Hance et al., 2007), be canceled-out with the inclusion of an above- or below- ground antagonist. For the most part this remains to be tested empirically. Moreover, with more empirical data it may be possi- ble that – as has been observed with other areas of climate change research (Robinson et al., 2012) – apparent idiosyncratic outcomes of climate change impacts on plant-herbivoreinteractions give way to reveal generalities. Trends have become apparent in some aspects of insect herbivory in elevated CO 2 (Zavala et al., 2013), for
The mathematical framework for plant–herbivore models is identical to interaction be- tween preys and their predators. In other words, such type models are basically modiﬁ- cations of prey–predator systems . The interaction between plants and herbivores has been investigated by many researchers both in diﬀerential and diﬀerence equations. Kartal  investigated the dynamical behavior of a plant–herbivore model including both diﬀer- ential and diﬀerence equations. Kang et al.  discussed bistability, bifurcation, and chaos control in a discrete-time plant–herbivore model. Liu et al.  investigated stability, limit cycle, Hopf bifurcations, and homoclinic bifurcation for a plant–herbivore model with toxin-determined functional response. Li et al.  discussed period-doubling and Hopf bifurcations for a plant–herbivore model incorporating plant toxicity in the functional re- sponse of plant–herbivoreinteractions. Similarly, for some other discussions related to qualitative behavior of plant–herbivore models, we refer the interested reader to [6–13] and references therein.
Lepidoptera, as a species-rich herbivore group with a rela- tively broad host-use spectrum, are a useful and widely-used model taxon. It remains to be seen whether the trends shown here will apply to other herbivore guilds with varying host- use patterns. However, the extremely high beta diversity both between and within all succession stages would suggest that network structure may be determined by processes which act largely independently of community composition and spe- cific species interactions per se, where perhaps fundamental rules govern assembly of these networks (Morris et al. 2014) or replacement of species occurs between topologically similar species (Dupont et al. 2009). This idea is supported by stud- ies of changes to networks across landscape (Kaartinen and Roslin 2011, Kemp et al. 2017), through time (Kaartinen and Roslin 2012, Kemp et al. 2017) and by comparisons of multiple independent networks across a latitudinal gradi- ent (Morris et al. 2014). Future research directions include developing a perspective of these plant-herbivoreinteractions which directly accounts for differences in plant traits, and not only host species composition. Traits related to growth and defense, for example specific leaf area and C:N ratios, can vary both within and between species throughout tropical succession (Poorter et al 2004), with these likely impacting herbivoreinteractions also.
Trissolcus brochymenae also responded to leaves that were above a leaf with M. histrionica feeding punctures, oviposition and footprints, whereas they did not react to leaves that were below the treated leaf. These results indicate that there is a systemic effect of the induction both in the leaf and in the plant, and that in the plant this effect is acropetous. Whether such systemic effect is the consequence of internal or external signalling within the plant (Heil and Silva Bueno, 2007) is unknown, and needs further investigation for this and other systems. Indeed, almost all of the oviposition- induced synomones known so far show a systemic distribution in the plant (Colazza et al., 2004a; Fatouros et al., 2005; Fatouros et al., 2008; Hilker et al., 2002a; Hilker and Meiners, 2006). This is important for both long-range and short-range synomones. In the first case, by maximising the releasing surface and because of its biomass, the plant is expected to emit high amounts of volatile synomones, making it easily detectable by the parasitoids. In the second case, by changing the chemistry of a large surface area, the plant would inform the parasitoid of the presence of the host eggs independent of the alighting site. The systemic synomone emission by the plant faded quicker than the local emission from the treated leaf portion and in the vicinity from the same leaf, as the parasitoids stopped responding 48h after the end of the treatment. Although the reasons for such a difference between local and systemic effects have not been elucidated yet, it appears that the plant stimulates host searching in the parasitoid only when the herbivore’s eggs are still fresh and suitable for successful parasitization. Therefore, synomone distribution in time seems to be finely tuned with parasitoid behaviour and biology, as has also been observed for a similar tritrophic system, bean–N. viridula–T. basalis, when volatile synomones were used as cues by the scelionid egg parasitoid (Colazza et al., 2004a), as well as for the cabbage–P. brassicae–T. maidis system (Fatouros et al., 2005).
Arthropods from three trophic levels were more abundant within the MeSA treatment than within the control in the field. This is the first time a higher-order parasitoid has been shown to be attracted to a synthetically-produced HIPV. The leafmining fly S. flava also responded positively to MeSA. Previous studies have shown herbivores to be attracted to HIPVs (Dicke and Minkenberg 1991, Finidori-Logli et al. 1996). Leafminers can induce the production of plant volatiles (Dicke and Minkenberg 1991, Finidori-Logli et al. 1996) and one explanation for the attraction of them could be the plants are more apparent to the herbivores (Feeny 1976, Vet and Dicke 1992) or weakened and are therefore more susceptible to them (Dicke and van Loon 2000). This is the first study showing that synthetically-produced MeSA increases the number of D. semiclausum (TL3) and A. zealandica (TL4). Hymenopterans have previously been shown to be affected by MeSA. The abundance of micro-Hymenoptera in grape vines and hop yards can be increased with synthetically-produced MeSA (James and Price 2004, James et al. 2005, James and Grasswitz 2005) and two other parasitoid species with hosts on brassica, Cotesia vestalis Haliday and C. glomerata L. (Hymenoptera: Braconidae), perceive MeSA produced by herbivore-damaged Brussels sprouts (Smid et al. 2002). Female D. semiclausum (TL3) were significantly more attracted to MeSA than males. Previous
The fitness and performance of a plant can depend greatly on the conditions of the soil it grows in (Bardgett and Wardle 2010). The soil is where plants get their water and nutrients from, but it is also the center stage for interactions with a wide range of soil biota. Soil biota profoundly contribute to plant growth and productivity, and their effects range from positive to negative via respectively mutualistic or antago- nistic interactions (Berendsen et al. 2012; van der Putten et al. 2013). Plants, in turn, influence the composition of the soil community around their roots via the excretion of root exudates or sheathing of dead root cells. Plant species can differ greatly in the composition and amount of these deposits, and this can lead to plant species-specific soil com- munities (Philippot et al. 2013; Shahzad et al. 2015). These specific soil communities can influence the performance of other plants that grow later in the same soil, a process called plant–soil feedback (PSF) (Bever 1994; van der Putten et al. 2013). PSFs can be conspecific, when the plant that grew previously in the soil affects future growth of plants of the same species, or heterospecific, when the plant species that grew previously in the soil affects future growth of other plant species. During the past decade, PSF and its legacy effects have been extensively studied in the context of plant community dynamics, such as environmental change-related range shifts, ecological succession, biological invasion and biodiversity (van der Putten et al. 2013). Recent studies revealed that induced changes in the composition of soil biota by plants could also affect aboveground multitrophic plant–insect interactions (Kostenko et al. 2012; Kos et al. 2015a; Heinen et al. 2018). Moreover, aboveground her- bivory in turn can affect the outcome of PSF effects (Heinze and Joshi 2018). The functional group that a plant belongs to may also explain the way in which it influences its soil. Several studies have observed that grasses induce more positive PSF effects than forbs (van de Voorde et al. 2011; Kos et al. 2015b), and that aboveground insect herbivores perform differently on plants growing in forb-conditioned and grass-conditioned soil (Heinen et al. 2018). So far, the mechanistic understanding of how PSFs influence above- ground plant–insect interactions through affecting induced defensive responses in the plant, and how this interacts with
Studies carried out in a wide array of ecosystems and regions in East Asia are required because the research on plant- pollinator interactions done so far has not been evenly distributed geographically. The majority of pollination studies in China have conducted in mountainous regions (Ren et al. 2018). In East Asia, relatively few studies have been conducted in the subtropics, coastal ecosystems, and wetland ecosystems. Although the Korean peninsula and Taiwan are biologically diverse and biogeographically important components of East Asia (Kong & Watts 1999; Choe et al. 2016; Zhu 2016; Tojo et al. 2017), very few studies on plant- pollinator interactions have been conducted in these regions. The relationship between habitat type and the composition of pollinator fauna in East Asia is still unclear because few community-level studies that were comparable among habitat types have been conducted. However, some trends can be observed (Fig. 2). Although very few studies have been conducted in wetland habitats, dipteran pollinators are known to be abundant in wetland habitats (Kato & Miura 1996). Bees, especially bumblebees, and Diptera are dominant flower visitors in alpine regions (Yumoto 1986; Fang & Huang 2012; Mizunaga & Kudo 2017; Ishii et al. 2019). Wasps tend to be more abundant in coastal sand dunes than in other habitats (Inoue & Endo 2006b; Hiraiwa & Ushimaru 2017). More studies are needed to definitively elucidate the relationships between different habitat types and their pollinator fauna.
1.1. Biotechnology promises to tackle global food security problems Food and agriculture globally are estimated to be a $5 trillion in- dustry experiencing continuous growth (Denis, 2015). The socioeconom- ic and environmental impact of agribusiness represents 10% of global consumer spending, 20% of employment as well as 30% of greenhouse- gas emissions. By current trends, with an exponentially growing world population expected to reach 10 billion people by 2050, caloric demands for both human and animal feed will double. In order to meet this grow- ing demand, food production must continue to increase, despite a sizeable improvement in productivity improvement observed over the past 50 years (Fuglie et al., 2012). However, agriculture today faces important challenges, which render this objective a difficult task. The increased agri- cultural activity suggests that 40% of water demand in 2030 is unlikely to be met, whilst the continuous loss of arable land and changing climates are some of the most highlighted and well-studied problems. In addition, approximately 26% of the worldwide crop production each year is lost due to pests and pathogens even before harvest. With rapidly advancing global trades, changing climates and agricultural intensification, the spread of plant diseases is expected to increase further. Different geogra- phies may face some of these problems to different levels, nevertheless, the above considerations represent global issues (Bebber et al., 2013). Al- together, this means that increases in food production will largely rely not only on increasing current agricultural efforts, but also on the develop- ment of existing technologies to improve output from the same amount of arable land. The four staples, which feed more than half the population includes wheat (Triticum aestivum), maize (Zea mays), banana (Musa acumi- nata) and rice (Oryza sativa). Importantly, the challenges facing these ma-
Although most biodiversity studies have focused on plants and their consumers, organisms feeding at higher trophic levels such as predators are predicted to be at greater risk of extinction than more basal species (Duffy 2003, Dobson et al. 2006). This is particularly evident in intensively-managed agroecosystems where predator abundance and diversity is consistently lower than in more diverse cropping or natural systems (Crowder et al. 2010, Krauss et al. 2011, Thies et al. 2011). The loss of predator diversity is significant because predators play an economically important role as agents of natural pest suppression (Losey and Vaughan 2006). Thus, declines in the abundance or diversity of predator species could have important implications for the management of herbivore pests, as well as cascading effects on plant yield (Cardinale et al. 2003). Manipulation of predator species richness has yielded a spectrum of results ranging from no response, to positive or negative impacts on natural pest suppression, with the majority of studies documenting a positive relationship (Cardinale et al. 2006, Bruno and Cardinale 2008, Finke and Snyder 2010, Tylianakis and Romo 2010).
26 herbaceous species present. Herbaceous and woody plant richness and abundance are expected to change at different rates because they have different life history strategies (Silvertown et al. 1993). The subsetting was carried out to ensure that only plots with the target life-form were included in the models because some plots have only herbaceous or only woody plants. Each model included the proportion of exotic species per quadrat as a binomial response variable. Explanatory variables added to the models were year, substrate type, distance from the sea and distance along the beach. I also included a null model in the candidate model sets to allow me to determine whether or not the best model(s) were explaining the data better than what could be expected at random (Burnham and Anderson 2002). The response and explanatory variables were linked using a logit link function and fitted using maximum likelihood estimation (McCullagh and Nelder 1989). When comparing models, second-order Akaike Information Criterion (AICc) was used to correct for the small sample sizes (Burnham and Anderson 2002, Millsap et al. 2013). Models were selected using quasi AICc values to account for the over-dispersion in the data. Over-dispersion occurs when there is more variability in the data than what is expected from a fitted model; this is indicated by a variance-inflation factor (ĉ) greater than 1, which is calculated during the model fitting process (Burnham and Anderson 2001, Symonds and Moussalli 2011).
A promising method in CBC is the attract-and- reward strategy, in which the colonization of crop fields by natural enemies is enhanced via attraction from surrounding habitats and their persistence and population growth is enhanced via the reward (Simpson et al., 2011a). The attractants are synthetically-produced molecules similar to natural herbivore-induced plant volatiles (HIPVs), such as methyl salicylate (MeSA) and methyl jasmonate. Plants naturally emit large amounts of HIPVs in response to herbivorous attacks, and these chemicals are long-distance attractants of herbivorous arthropods’ natural enemies (Turlings & Erb, 2018). The effect of synthetic MeSA is comparable to that of naturally emitted MeSA, and it has been widely implemented in CBC targeting natural enemies such as hemipteran bugs, coccinellids and hoverflies (Zhu & Park, 2005; Rodriguez-Saona et al., 2011; Gadino et al., 2012). In particular, the MeSA plant-defence pathway is induced by phloem-sucking insects such as aphids, while the methyl jasmonate pathway is induced by leaf chewers (Soler et al., 2012). Therefore MeSA is likely more relevant to coccinellids, which essentially depend on aphids as a food resource (Vandereycken et al., 2013; Ali et al., 2018).
In plants and other organisms, HSP70 family members play important roles in protein folding (Forreiter et al., 1997; Lee and Vierling, 2000), protein complex assembly and disassembly (Liu et al., 2007) and protein trafficking across membranes (Zhang and Glaser, 2002; Vojta et al., 2007). In addition, plant HSP70s may traffic non-cell autonomous proteins through plasmodesmata, because an intercellular class has been discovered (Aoki et al., 2002). A potential role for plant HSP70s in promoting virus infections in susceptible plants has also been implied based on the following reasons. First, in response to different plant viruses like potyviruses and tobamoviruses, HSP70 mRNAs accumulate to higher levels (Aranda et al., 1996; Escaler et al., 2000; Whitham et al., 2003; Aparicio et al., 2005). Second, the replicase protein, p33 of Cucumber necrosis tombusvirus (CNV) was found to interact with yeast HSP70s to presumably enhance replication of a Tomato bushy stunt tombusvirus (TBSV) replicon in yeast (Serva and Nagy, 2006). Third, a HSP70 homolog (HSP70h) encoded among members of the Closteroviridae family of plant viruses (Dolja et al., 2006), is required for Beet yellows closterovirus (BYV) virion assembly and intercellular movement (Peremyslov et al., 1999; Prokhnevsky et al., 2002). Fourth, several animal viruses require HSP70s to facilitate viral processes in host cells (Mayer, 2005).
Given the high concentrations of terpenes in the leaves of Melaleuca alternifolia, it is likely that volatile terpenes are released constitutively from the secretory cavities but ever more following mechanical damage by herbivores. M. alternifolia occurs as well-characterised monoterpene chemotypes, which are chemical polymorphisms with a different mixture of monoterpenes (Homer et al. 2000; Keszei et al. 2010). Three cardinal chemotypes have been described and are dominated by terpinen-4-ol (Chemotype 1), terpinolene (Chemotype 2) or 1,8- cineole (Chemotype 5) whereas three other chemotypes are intermediate and might be the result of crossing between the cardinal chemotypes (Shelton et al. 2002). Whether plant chemotypes determine the VOC emission profiles remains unknown. The characterized chemical profiles of M. alternifolia make it an excellent candidate species for exploring how diversity in foliar chemistry translates to diversity in VOC emission in different genotypes. Also, volatile emissions may influence the ecological interactions between M. alternifolia and two specialist leaf beetle species, which are the main leaf consumers in natural populations and plantations (Campbell & Maddox 1999; Bustos-Segura et al. 2015). Therefore, in this study we analysed the VOC emissions of M. alternifolia from the three cardinal monoterpene chemotypes and also explored how
The hypothesis for a role for mannitol in host-pathogen interactions has come from direct and indirect observations. While some have reported mannitol accumulation in liver tissue and blood of rats suffering from aspergillosis (Wong, et al., 1989), others have shown that mutants of C. neoformans that produced less mannitol were found to be less virulent than wild type (Chaturvedi et al., 1996 a ). C. neoformans produces large amounts of the mannitol in culture and infected animals. A UV generated mutant of C. neoformans that produced less mannitol was more susceptible to stresses such as heat and high NaCl concentrations than wild type. In addition, mice that were inoculated with the mutant survived, while the ones inoculated with the wild type at the same inoculum concentration died. The same mutant and wild type were used in an assay with polymorphonuclear neutrophils. Polymorphonuclear neutrophils killed more mutants than wild type C. neoformans after 2 and 4 hrs of exposure (p < than 0.05). While the usage of catalase in the assay did not prevent the death of the two strains, using superoxide dismutase, mannitol, and DMSO prevented both strains from being killed. It was suggested that C. neoformans produced and secreted mannitol to protect itself against oxidative killing mechanisms of phagocytic cells (Chaturvedi et al., 1996 b ). The yeast C. albicans produces arabinitol in cultured, as well as in animals and humans suffering from candidiasis (Kiehn, et al., 1979). Link et al., 2005 recently showed that arabinitol, which is also made by the fungus U. fabae, can also quench ROS. However, similar studies as those with C. neoformans have not been done with C. albicans and arabinitol.
Our top model demonstrates that at the population level, TmKnown, ruggedness, productivity, distance to road, and interactions between distance to road and herd and TmKnown and productivity were the most influen- tial environmental covariates determining return counts at patches across the season. The importance of prod- uctivity in return models supports the underlying thesis of Van Moorter et al.’s  model which values patches based on replenishment of resources. As expected our results demonstrate that productive patches are returned to more often than less productive patches. An attrac- tion to productive forage is consistent with previous work demonstrating that elk migration often follows the start of spring photosynthetic activity, or greenup; as new growth extends into higher elevations over summer so do elk . Forage research on elk also shows attrac- tion to intermediate levels of biomass, often more di- gestible and productive than tall late-season stands, and forage abundance has been shown to encourage site fi- delity in nonmigratory elk populations on short time in- tervals, supporting our results that productivity may strongly influence returns [23-25].