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I've just seen a report about specialized herbivorous plants which build special traps to catch falling leaves from trees above them.
The only thing, which I'm missing is the correct name of this plant. Do you have any idea what plant(s) could this be?
Many plants do this, with varying degrees of specialization - for some it is perhaps incidental, others have evolved this strategy to gain nutrients (often water as well). You are probably thinking of bromeliads, a diverse group of plants in which many species have specialized leaves that form cups at the base to collect water and litter. These structures, a type of phytotelmata, have similarities to some carnivorous plant traps.
These tank bromeliads are able to efficiently absorb nutrients from animal or plant matter which falls into the tank:
Considerable absorbed nitrogen is mobilized in the rosette center. Tested bromeliads appear to be well equipped to utilize minerals and organic nitrogen originating from tank-impounded plant and animal debris as nutrients.
This litter catching habit occurs in other lithophytic and epiphytic plants, i.e. those which don't grow in soil, because it allows them to capture nutrients when growing on rocks or trees. Examples include the staghorns/elkhorns and basket ferns:
They form a characteristic 'basket' that collect litter and organic debris, hence the common name. The collected debris decompose into humus, providing the plants with nutrients it would otherwise not have received from being suspended above the ground.
After all, I found the answer myself.
The special plant I'm looking for is the Nepenthes ampullaria. It has developed away from the "normal" carnivorous plants to a more detritivorous species.
Nepenthes ampullaria has specialized her pitcher to catch falling leaves from trees above her.
Browsing is a type of herbivory in which a herbivore (or, more narrowly defined, a folivore) feeds on leaves, soft shoots, or fruits of high-growing, generally woody plants such as shrubs.  This is contrasted with grazing, usually associated with animals feeding on grass or other lower vegetations. Alternatively, grazers are animals eating mainly grass, and browsers are animals eating mainly non-grasses, which include both woody and herbaceous dicots. In either case, an example of this dichotomy are goats (which are browsers) and sheep (which are grazers) these two closely related ruminants utilize dissimilar food sources.
My main research focuses on the evolution of plant-animal interactions—flower-pollinator associations and plant-herbivore interactions. I am particularly interested in how plant behaviors enhance reproductive success. Flower-pollinator studies include the evolution of exploding flowers— e.g., explosive flowering in bunchberry (Cornus canadensis) and stinging nettles (Urtica spp.), and other flower behaviors—e.g., studies on pollen protection in wood lilies (Lilium philadelphicum) (see PDF) and in jewelweed or touch-me-not (Impatiens spp.), and patterns of flower longevity in boreal plants. My plant-herbivore studies include sawfly (Empria obscurata) herbivory on shrubby cinquefoil (Potentilla fruticosa) and other plants in the rose family (Rosaceae) and moose-plant interactions.
In Williamstown, I am studying the conservation of fall blooming asters and goldenrods. These species are an important part of our New England biodiversity heritage. We are in the center of diversity for goldenrods (Solidago spp.). In New England as forest is replacing field habitat, the number of asters and goldenrods is declining. These are species are not only important for maintaining floral diversity but they also provide nectar and pollen for pollinators just before they overwinter. Currently we are studying how mowing practices impact both the flowers and their pollinators.
I also have two long-term studies of plant population dynamics. Both studies have permanently marked quadrats, which are checked annually. The first are rocky shoreline plants at the northeastern end of Isle Royale National Park. The second are populations of the invasive plant, garlic mustard (Alliaria petiolata), in temperate deciduous forest of Hopkins Memorial Forest.
More on Research
Each research project is described briefly below:
One typically thinks of plants as sedentary and slow moving, but the most rapid movements in animals rely on stored mechanical energy (not muscle power!), thus plants should be able to match or surpass the fastest plant movement. Using ultra high-speed video (10,000fps) we measured the speed of rapid movements in plants. Our web site on the exploding dogwood flowers gives more details. We are also studying other rapid plant movements from the explosion of Impatiens fruits to the air-gun propulsion of spores in Sphagnum. And we worked with Dr. Dave Kelly at the University of Christchurch, New Zealand on exploding Mistletoes (PDF of paper and link to Dave’s web site).
Reversible Cryptic Coloration in the sawfly, Empria obscurata (Early Strawberry Slug) (Hymenoptera)
Many animals use cryptic coloration to avoid predators. Most have fixed colors to match one background. A few can some alter their color to match different background. We discovered that the larvae of Empria obscurata are translucent, taking on the color of their food. We are studying the adaptive significance of this extraordinary trait.
Pollination Biology and Seed Dispsersal in Impatiens
Rhingia nasica (Syrphidae, Diptera) on Impatiens pallida (Balsaminiferae) flowers. Rhingia collects both pollen from the anthers and nectar from the spur on the sepal (see below), but is a “robber” as it does not make the correct contacts to effect pollination.
Floral Behavior of Boreal Forest Plants
I studied moose-plant interactions at Isle Royale National Park where I observed moose feeding behavior (300+ hours of observing moose and recording their diet in terms of the number of bites of each plant species) and studied their impact on plants. See papers on Aralia nudicaulis (2 pdf’s) and moose behavior (3pdf’s).
Long-term Population Dynamics of Great Lakes-Arctic disjuncts. Isle Royale National Park, Lake Superior, Michigan.
The rocky shoreline at the Northeastern end of Isle Royale National Park harbors relict populations of arctic plants. Often the next closest population is in the arctic. Since 1999 we have mapped and kept track of individual plants on three different islands and seven different sites.
Long-term Population Dynamics of the invasive Eurasian Plant, Garlic Mustard (Alliaria petiolata, Brassicaceae). Hopkins Memorial Forest, Williamstown, Massachusetts.
We designed permquads (stainless steel quadrats) that are 0.5 x 0.5 meters on a side and are anchored to the ground with u-shaped stainless steel pins). Each year we record the number of rosettes, flowering plants in the quadrat. We also count the number of seeds on each plant and in each seed trap. These data provide information to chart invasion, fluctuations in populations levels, and to project future population sizes.
Recent Honors Students* and Research Assistants
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Our results demonstrate that biological pests significantly increase the frequency of a hereditary symbiont over time. This experimental study identifies herbivory as an important mechanism in the dynamics of hereditary symbiosis. The increase in frequency of the Neotyphodium endophyte in tall fescue grass was 2.5 times greater in control plots with herbivores than in the dual mammalian and invertebrate herbivore-exclusion treatment. This effect was presumably in part due to the herbivore-deterrent alkaloids present only in endophyte-infected plants (31). Although we did not quantify alkaloids in this study, their production in endophyte-infected tall fescue is well documented (31, 66).
The importance of herbivores in the dynamics of plant–microbe interactions may be widespread. Although our results provide the first evidence for long-term impacts of herbivores on a hereditary symbiont, other studies have found strong interactions between herbivores and horizontally transmitted symbionts such as mycorrhizal fungi, pathogens, and other endophytic fungi (7, 67). For example, in one of the few long-term studies of herbivore effects, high densities of scale insects reduced colonization by mycorrhizal fungi on pinyon pines that were susceptible to scale attack (70). However, with herbivores and mycorrhizal fungi, the effects are typically in the opposite direction of the results presented here, in which the herbivores suppress, rather than promote, the symbiont. The direction of the herbivore effect may hinge on how the symbiont alters the herbivore resistance of its host.
The increase in symbiont frequency that occurred even when both mammalian and insect herbivores were reduced (a 12% increase) suggests that even low levels of herbivory may benefit infected plants. Our exclusion treatments were not 100% effective, and other groups of plant consumers (such as plant pathogens, nematodes, and mollusks) were not experimentally manipulated. Also, other benefits of the endophyte, such as enhanced drought tolerance or nutrient acquisition, may also have contributed to increasing endophyte frequency in the dual exclusion plots (24, 25). However, in the absence of interactive effects with our treatments (e.g., plants treated with insecticide have increased drought tolerance or reduced pathogen attack), these alternative benefits and uncontrolled consumption of tall fescue would have been spread evenly over all replicates. Thus, the 2.5-fold difference in infection frequency (30% vs. 12%) represents the effect of our experimental reduction in vertebrate and invertebrate herbivory. Had this experiment continued longer, endophyte frequency may have reached fixation (100% of plants with the endophyte), but metabolic costs of infection, variation in environmental conditions (including herbivore pressure), and/or loss of infection from dormant seeds could maintain variation in infection frequency (28, 29).
Not only were the dynamics of the symbiont altered by herbivores, but the relative biomass of the host plant shifted also. Mammalian herbivory increased tall fescue biomass by 58% in unfenced plots compared with fenced plots. Biomass is an important component of fitness for this clonal species, and it is also highly correlated with inflorescence production and, therefore, reproductive fitness. Thus, when the endophyte is present, tall fescue clearly benefits from mammalian herbivory. We estimated the percentage of total live biomass that consisted of infected tall fescue by multiplying the percentage of total biomass that was tall fescue in fenced plots (38%) vs. unfenced plots (58%) by their mean endophyte-infection frequencies. In fenced plots, 26% of the total biomass was infected tall fescue, vs. 39% in unfenced plots (a 48% increase). Given the lower initial infection in unfenced plots, this is a conservative estimate of the increase in endophyte-infected biomass. This result is relevant to previous research on the possible benefits to plants from herbivory (71) and shows that herbivores can increase the competitive dominance of toxic plants. However, in the case of tall fescue, the herbivore resistance traits are not intrinsic to the plant but are rather provided by the endophyte symbiont. Although herbivory may be harmful to individual plants, it is clearly advantageous to infected tall fescue populations (74).
Mammalian herbivory not only increased the biomass of tall fescue but also reduced the biomass of forb and nonfescue grass species in the community. In contrast to mammalian herbivory, insect herbivory did not affect tall fescue biomass or plant composition, although it did affect endophyte frequency in combination with mammalian herbivory. Therefore, the change in endophyte frequency was not the only factor altering composition of the plant community. These results suggest that mammalian herbivores affect plant composition both directly by preferentially consuming nonfescue plants as well as indirectly by altering endophyte frequency. It has been found that voles consume significantly more nonfescue plants in plots of 100% endophyte-infected tall fescue than in endophyte-free plots (J.A.R., S. P. Orr, and K.C., unpublished data). The observed shift in plant composition was consistent with ref. 34, which reported reduced species richness and increased tall fescue biomass in experimental grasslands, with 100% infected tall fescue compared with endophyte-free tall fescue. Results presented here demonstrate that herbivores modify community structure by increasing the biomass of herbivore-resistant, endophyte-infected tall fescue.
Although our focus was on tall fescue and changes in the plant community, our results point to an important role of herbivores for the fitness of the fungal endophyte. Because it has no free-living or contagious stage, N. coenophialum can increase its fitness in only two ways: by clonal spread of its host plants or vertical transmission to seeds. Our data suggest that both mechanisms are enhanced by herbivory. The percentage of biomass infected with the endophyte increased most in the presence of herbivores, and biomass is highly correlated with seed production in this system. Our calculations in the above paragraph suggest that fungal fitness is 48% higher in the presence (unfenced plots) than absence (fenced plots) of mammalian herbivores. There was no evidence for a net cost to the fungus of symbiosis with tall fescue because the frequency of endophyte infection increased over time in all of our experimental treatments.
Our results have broad implications for understanding the success of invasive species. Plants invading novel habitats may frequently suffer less damage from pests and parasites than native species (75). Also, invasive plants may possess novel chemistry to which resident species are not adapted (78). In the case of tall fescue, the mixture and quantities of endophyte alkaloids may represent formidable barriers to resident herbivores. However, there have been no comparable studies examining the interaction among the endophyte symbiont, herbivores, and the resident plant community in tall fescue or in any other grass species. It would be useful to replicate this experiment at multiple locations around the world where tall fescue occurs. In particular, it would be useful to determine whether European and African herbivores are more adapted to endophyte-infected tall fescue. In our experiment, the relative biomass of infected tall fescue was enhanced by herbivores, suggesting that this grass may be better able to invade novel habitats with high levels of herbivore pressure. More generally, our results confirm the important role of mammalian herbivores (particularly voles) in shaping the composition and dynamics of plant communities (79).
Considering the role of species interactions extrinsic to symbioses, such as predation or competition, may prove to be crucial to understanding the long-term dynamics of host–symbiont interactions, the fixation or loss of hereditary symbioses, the evolution of mutualism, and the mechanisms driving associated changes in community structure. Here, we show that herbivory reduced the biomass of symbiont-free tall fescue, as well as other plant species, and increased the biomass of symbiotic tall fescue.
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Leaf-Eating Caterpillars Use Their Poop to Trick Plants
Caterpillars that munch on corn leaves have developed a clever way to get the most nutrients from their meals: They use their poop to trick the plants into lowering their defenses.
Scientists at Pennsylvania State University recently discovered that fall armyworm caterpillars (Spodoptera frugiperda) can send chemical signals to plants through their poop, or frass.
"It turns out that the caterpillar frass tricks the plant into sensing that it is being attacked by fungal pathogens," study co-author Dawn Luthe, a professor of plant stress biology at Pennsylvania State University, said in a statement. [In Photos: Animals That Mimic Plants]
Corn plants can deal with only one kind of attack at a time, so while a corn plant is dealing with the perceived "fungal infection," the caterpillar is left to feast on the plant's leaves. Normally, a plant will recognize chemical signatures from insect secretions, which helps the plant know when to raise its defenses. In many cases, this includes producing a biochemical that repels herbivores, such as insects.
But chemical signals from the caterpillar's poop act as crafty diversions, the researchers said.
"The plant perceives that it is being attacked by a pathogen and not an insect, so it turns on its defenses against pathogens, leaving the caterpillar free to continue feeding on the plant," Swayamjit Ray, a doctoral student in plant biology at Penn State and co-author of the paper, said in a statement. "It is an ecological strategy that has been perfected over thousands of years of evolution."
Caterpillars usually feed on the leaves in the confined whorls of corn plants. The critters typically defecate in the crevasses where the leaves meet the stalk, the researchers said.
Scientists studied the biochemical relationship between fall armyworm caterpillar frass and a plant's defensive mechanisms by performing two tests. In the first test, the scientists applied frass extract to the leaves of some corn plants and compared caterpillar growth of those that fed on treated leaves with those that munched on untreated leaves.
The second test involved measuring how frass-treated corn leaves affected defensive performance on plants exposed to a fungal pathogen &mdash in this case, spores of a fungus that causes blight in corn (Cochliobolus heterostrophus). The scientists observed that, initially, proteins in the frass activated an insect defense in the plant, but over time, as the corn plants were exposed to more of the protein, the plants' defenses became altered and instead began to recognize the frass protein as a fungal pathogen instead of an insect waste product. This caused the plant to defend itself against what it saw as a fungal threat instead of an insect threat.
While this may not be good news for plants suffering from a caterpillar infestation, the researchers think it may be possible to isolate the specific components in caterpillar poop that heighten a plant's defenses against pathogens. If this is the case, the scientists said, farmers could one day develop an organic and sustainable pesticide to prevent infection and disease in crops.
The findings were published online Aug. 26 in the Journal of Chemical Ecology.
Herbivorous plants that consume falling leaves - Biology
Common Name: Garlic Mustard
Scientific Name: Alliaria petiolata
Classification: Division: Magnoliophyta
There are several native plants that are similar in appearance to the garlic mustard. These include: toothworts (Dentaria), sweet cicely (Osmorthiza claytonii), and early sexifrage (Saxifraga virginica). The garlic mustard can be distinguished from these plants by the garlic/onion smell that the leaves, and stem emit when crushed.
Original Distribution: Garlic mustard was originally found in Northeastern Europe, from England east to Czechoslovakia and from Sweden and Germany south to Italy.
Current Distribution: At the present time garlic mustard is distributed throughout the northeastern and midwestern United States. It is found in 30 eastern/midwestern states, as well as 3 canadian provinces. It is found from Canada to South Carolina and west to Kansas, North Dakota, and as far as Colorado and Utah.
Garlic mustard is also found in North Africa, India, Sri Lanka, and New Zealand.
Site and Date of Introduction: The first sighting of the garlic mustard herb in the U.S.A. was in 1868 in Long Island, New York.
Mode of Introduction: Garlic mustard was intentionally introduced into the northeastern United States for food, erosion control, and medicine. Early European settlers brought the herb over to use as a garlic flavored herb with a good source of vitamin A and C. The herbs medicinal purposes include being used to treat gangrene and ulcers. The herb was also planted as a form of erosion control.
Reasons Why it has Become Established: The success of garlic mustard as an invasive species seems to be related to: the absence of natural enemies in North America, it's ability to self fertilize, high production of 15,000 seeds annually, rapid growth during the second growing season, and the release of phytotoxins from its root tissue.
In Europe, the original range of garlic mustard, there are over 30 insects that attack its leaves, stem, and seeds. There are also specialist herbivores that use garlic mustard as a food source. In North America there are no such enemies. A common herbivore found in northeasern U.S.A and southern Canada, the white-tailed deer prefers to eat native plants. The white-tailed deer thus facilitates the spread of garlic mustard by clearing out competitors, while at the same time spreading the seeds on its fur and exposing soil and seedbed by trampling.
The herb has a autogamous breeding system which produces 15,000 seeds annually, allowing for a small number of individuals to create large populations. These seeds remain viable for up to 5 years. After a dormant season, garlic mustard has a rapid growth period in the late fall to early spring, when most of the native plants are dormant. This allows the plant to dominate nutrients, space, and light when other plants cannot get to it.
Several phytotoxins were isolated from the tissue of garlic mustard. These phytotoxins may inhibit the growth of other plants and allow the garlic mustard to be invasive.
Garlic mustard may also reduce the competitive ability of native plants by interfering with the formation of mycorrihizal associations and root growth.
Ecological Role: In Europe, the original range of the garlic mustard, some herbivores relied on the plant for food.
Benefits: Garlic mustard has uses as a medicine for treatment if gangrene, and ulcers. It can also be used as garlic flavored herb with vitamin A and C. Additionally, garlic mustard can be planted for erosion control.
Threats: Garlic mustard is currently displacing native understory species in the forests of northeastern America and southern Canada. Native wildflowers include spring beauty, wild ginger, bloodrot, Dutchman's breeches, hepatica, toothwortsm, and trilliums. It displaces native herbaceous species within 10 years of establishment. Garlic mustard can invade undisturbed areas as well as disturbed areas.
Garlic mustard is also a threat to species that depend on the native understory species. For example, the endangered Virginia white butterfly (Pieris virginiensis) uses toothworts as a food supply during the caterpillar stage. Garlic mustard displaces toothworts, and is toxic to the eggs of the butterfly. Similarly, the native American butterfly (Pieris napi aleracea) which commonly use native mustards as their host plants, tries to use garlic mustard, but their larvae die.
Control Level Diagnosis: Highest Priority- Garlic mustard has spread far from the original place of introduction in Long Island. It has proven to be a highly invasive plant with characteristics that allow it to contine to be invasive. If left alone, garlic mustard will continue to displace forest understory plants across the United Stated in both disturbed and undisturbed forests.
Control Method: There are many methods currently used to try and remove garlic mustard. These include mechanical controls, chemical controls, and biological controls.
Mechanical control: Garlic mustard can be pulled out by hand at or before the onset of flowering. The whole root must be removed because new plants can sprout from root fragments. After pulling, the soil must be thoroughly tamped to prevent soil disturbance, and bringing up seeds from the seed bank.
Cutting the plant is a less destructive control. The flower stalk can be cut at ground level or within several inches from the ground, only once the flowering begins. Cutting too soon may cause resprouting, and cutting too high may cause the plant to produce additional flowers.
If too large an area is infested for pulling or cutting to be effective, fall or early spring burning is an option. Spring burns must take place early, so they do not cause harm to wild flowers. 3-5 years of fires are needed, and should be supplemented by hand pulling or cutting afterward. Fire may enhance the spread by surviving seedlings by exposing bare soil. A study done in 2000 shows that repeated burning may actually increase the number of flowering stems.
Chemical control: 1-2% active ingredient solution of glyphosoate can be applied to the foliage of individual plants, and dense patches during late fall or early spring when most native plants are dormant. The temperature should be above 50 degrees F, with no rain expected for 8 hours. Glyphosate is a non selective herbicide that will kill non target plants. DIRECTIONS AND WARNINGS SHOULD BE READ CAREFULLY BEFORE USING ANY CHEMICAL CONTROL.
Biological control: Research towards biological control are currently taking place at Cornell University.
Pine Bark Beetles
K.F. Raffa , . F. Schlyter , in Advances in Insect Physiology , 2016
2.3 Modulation by Antiattractive Signals and the Semiochemical Diversity Hypothesis
A meta-analysis showed that there is a general reduction in herbivory by oligophagous insects as the biodiversity of forests increases ( Jactel and Brockerhoff, 2007 ). The semiochemical diversity hypothesis (SDH), as postulated by Zhang and Schlyter (2003) , suggests that this decrease might be due to the presence of antiattractive volatiles from non-host plants, reducing the searching efficiency of specialist and oligophagous insects. Thus, bark beetles may actively avoid diverse habitats because they worsen the odds of finding a potential host as compared to searching in conifer-dominated habitats. Numerous studies on bark beetles have shown that NHV reduce the attraction to individual point sources (reviewed in Zhang and Schlyter, 2004 ). In addition, several studies have also indicated area-wide or ‘habitat-scale’ inhibitory effects of NHV in bark beetles and other forest insects ( Jactel et al., 2011 Schlyter, 2012 ).
By using passive (unbaited) traps around point sources baited with aggregation pheromone and NHV, the ‘active inhibitory radius’ of NHV mixtures on I. typographus was estimated at 2–4 m, suggesting that the effect of NHV is not restricted to individual point sources ( Zhang and Schlyter, 2003 ). In addition, odour source spacing experiments, in which single pheromone dispensers were separated from single NHV dispensers on multiple-funnel ‘Lindgren’ traps, indicated that one point source of an NHV mixture can reduce the attraction of I. typographus to a pheromone released > 1 m away from the NHV source ( Andersson et al., 2011 ). It was also shown that eight NHV dispensers, again releasing a mixture of compounds, positioned in a circle around a central pheromone trap reduced trap catches up to a radius of 2–3 m ( Andersson et al., 2011 ). While these studies all suggest that individual dispensers releasing a mixture of NHV compounds inhibit pheromone attraction over a few metres distance, they do not conclusively demonstrate that inhibition scales up to habitat-scale effects. However, Schiebe et al. (2011) treated groups of susceptible Norway spruce trees (Picea abies (L.) Karst) at forest edges with NHV mixtures (ie, no synthetic attractant was used), which diverted I. typographus attacks from the experimental zones to untreated trees 15–30 m away. This observation indicates habitat-scale effects of NHV on bark beetle host selection behaviour. Avoiding searching for a suitable host in habitats where the chances of finding one are slim seems adaptive, as it likely reduces host selection costs, such as energy expenditure, predation risk, and time that otherwise could have contributed to reproduction by the short-lived adults. The variation in the observed active distance of NHV in the different studies is likely due to the use of aggregation pheromone as attractant, which is a very strong signal, vs the absence of such a signal when applying NHV to non-attacked trees. This difference also highlights the profound difference between the decisions facing pioneering individuals, which must select optimal hosts in the absence of conspecific cues, vs the responding beetles that can ignore negative olfactory signals from the host or surrounding plants in the presence of cues indicating success by pioneers.
It is possible that the different constituents of the NHV mixtures are active at different steps in the host selection sequence. It has been hypothesized that general green leaf volatiles (GLV, mostly C6-alcohols), primarily released by angiosperm trees, might serve as a negative signal at the habitat level ( Schlyter and Birgersson, 1999 ), whereas more specific NHV from the bark (eg, C8-alcohols and the spiroacetal trans-conophthorin) might represent unsuitable host species signals ( Zhang and Schlyter, 2004 ). Antiattractive pheromonal compounds, such as verbenone, produced primarily by yeasts in bark beetle galleries ( Leufvén et al., 1984 ), might signal host unsuitability at the host individual level ( Zhang and Schlyter, 2004 ). Bark beetles are thought to use these compounds to avoid trees with high intraspecific competition and low nutritional value ( Schlyter et al., 1989 ). In addition, it was recently shown that the amounts of certain host compounds, including 1,8-cineole and p-cymene, increase in P. abies heavily attacked by I. typographus ( Andersson et al., 2010 ). 1,8-Cineole (and p-cymene to some extent) was shown to strongly inhibit pheromone attraction of I. typographus and thus might also serve as a negative signal in host suitability assessment ( Andersson et al., 2010 ). Schiebe et al. (2012) demonstrated that 1,8-cineole is present in significantly higher amounts in P. abies that were resistant to bark beetle attack (ie, trees in which pioneering individuals were unsuccessful), as compared to those that were successfully attacked and killed. Thus, a bark beetle is likely to increase its chances of survival and reproduction by avoiding trees with strong chemical defences as signalled and/or mediated by 1,8-cineole ( Andersson et al., 2010 Binyameen et al., 2014 ). Similarly, the host phenylpropanoid 4-allylanisole (also known as estragole), which inhibits growth of bark beetle-associated fungi, inhibits pheromone attraction of several North American Ips and Dendroctonus spp. ( Hayes and Strom, 1994 Hayes et al., 1994 ). In addition, a mixture of major host monoterpenes interrupted pheromone attraction of the Asian larch bark beetle Ips subelongatus Motschulsky ( Zhang et al., 2007 ). It was hypothesized that the high release rates of monoterpenes that were used might have been indicative of a healthy tree—too vigorous to succumb to bark beetle colonization. Thus, host-derived compounds can serve as both attractants and antiattractants, with their exact behavioural effects being context dependent and varying among species, sexes, physiological state, and release rate. Finally, inhibition of attraction to aggregation pheromones by heterospecific pheromone compounds is common across Scolytinae ( Birch et al., 1980 Byers, 1993 Poland and Borden, 1998a ). This inhibition is likely to represent a mechanism for preventing interspecific competition and/or mating mistakes.
Professor Sue Hartley OBE
Sue Hartley is Director of the York Environmental Sustainability Institute, which builds interdisciplinary partnerships to generate sustainable solutions to global environmental challenges. She is also the University&rsquos Research Champion for Environmental Sustainability and Resilience, a trustee of Royal Botanic Gardens, Kew and a board member of Natural England, the UK Government&rsquos statutory adviser for the natural environment in England. Her research group are interested in understanding the interactions between organisms exploiting plants, how those interactions are mediated by plant defences, particularly silicon, and how a better understanding of those processes can improve both the sustainability of agriculture and agri-environmental policy.
Her research and scientific publications fall into three main areas:
Plants are at the centre of a complex web of interactions with other organisms which seek to exploit them: herbivores, the natural enemies of those herbivores, pathogens, parasites and mutualists. I am interested in the chemical basis of these interactions between plants and other organisms, particularly herbivores the impact of these plant-mediated interactions on the structure and function of ecological communities and how this complex web of species interactions is affected by climate change.
Silicon-based plant defences
Grasses, both native species and crops such as rice, wheat and barley, take up silicon from the soil in unusually high amounts and deposit on their leaves (figure 1), making them more resistant to herbivores such as crop pests. Silicon also protects crops from pathogens and alleviates abiotic stresses, such as drought. A better understanding of the biochemical and genetic mechanisms underpinning silicon accumulation in plants will enable the development of strategies for improving the resilience of our crops to both environmental change and to the pests and diseases which threaten our food supply.
Leaf surface of Deschampsia caespitosa, a grass species high in silicon. The yellow colour shows the location of silicon in SEM pictures of the leaf surface in undamaged and damaged leaves, showing the increases in silicon deposition, number and diversity of silicon-containing spines in response to herbivory.
Sustainable agriculture and agri-environmental policy
There is increasing interest in making agriculture more sustainable and less reliant on chemical inputs whilst still maintaining food production for a growing population. The use of natural plant defences such as silicon is one approach, but many others are gaining traction globally (figure 2). This is a fast-moving policy area where there are opportunities to move the UK Government&rsquos agri-environmental policy towards a so-called &ldquopublic money for public goods&rdquo approach, where farm subsidies are linked to ecosystem services rather than agricultural production, with concomitant benefits for farmland biodiversity.
Increasing global use of seven approaches to increase the sustainability of agriculture while maintaining yield.