Gene flow in the endophyte Neotyphodium and implications for coevolution with Festuca arizonica

Arizona fescue (Festuca arizonica) often harbours asymptomatic, asexual endophytic fungi from the genus Neotyphodium. In agronomic grasses, Neotyphodium endophytes are often credited with a wide range of mutualistic benefits to its host many of which are related to fungal production of alkaloids for herbivore deterrence. Neotyphodium in the native grass Arizona fescue, however, usually produces alkaloids at levels too low to deter herbivores, and in general, does not behave mutualistically. This study uses microsatellite markers to examine rates of gene flow among four Arizona populations of Neotyphodium. Haplotypic diversity was generally low; only one population contained more than two haplotypes. Haplotypes carrying multiple loci for some or all of the microsatellite loci were also found, indicating a vegetative hybridization event between Neotyphodium and the grass choke pathogen from the genus Epichloë. Gene flow between Neotyphodium populations is very low, and likely much lower than the pollen mediated gene flow of its host. These differing rates of gene flow are predicted to create trait mismatching between endophyte and host and may explain the low, or lack of, alkaloid production by Neotyphodium in Arizona fescue and other native grass species.     

Role of volatiles emitted by host and non-host plants in the foraging behaviour of Dentichasmias busseolae, a pupal parasitoid of the spotted stemborer Chilo partellus

The role of volatiles from stemborer host and non‐host plants in the host‐finding process of Dentichasmias busseolae Heinrich (Hymenoptera: Ichneumonidae) a pupal parasitoid of Chilo partellus (Swinhoe) (Lepidoptera: Crambidae) was studied. The non‐host plant, molasses grass (Melinis minutiflora Beauv. (Poaceae)), is reported to produce some volatile compounds known to be attractive to some parasitoid species. The studies were conducted to explore the possibility of intercropping stemborer host plants with molasses grass in order to enhance the foraging activity of D. busseolae in such a diversified agro‐ecosystem. Olfactometric bioassays showed that volatiles from the host plants maize, Zea mays L., and sorghum, Sorghum bicolor (L.) (Poaceae), were attractive to the parasitoid. Infested host plants were the most attractive. Volatiles from molasses grass were repellent to the parasitoid. Further tests showed that volatiles from infested and uninfested host plants alone were preferred over those from infested and uninfested host plants combined with the non‐host plant, molasses grass. In dual choice tests, the parasitoid did not discriminate between volatiles from maize infested by either of the two herbivore species, C. partellus or Busseola fusca Fuller (Lepidoptera: Noctuidae). Volatiles from sorghum infested by C. partellus were preferred over those from C. partellus‐infested maize. The study showed that the pupal parasitoid D. busseolae uses plant volatiles during foraging, with those from the plant–herbivore complex being the most attractive. The fact that volatiles from molasses grass were deterrent to the parasitoid suggested that intercropping maize or sorghum with molasses grass was not likely to enhance the foraging behaviour of D. busseolae. Volatiles from the molasses grass may hinder D. busseolae's host location efficiency.     

Chloris gayana (Rhodes grass), a better host for the mas production ofGlomus fasciculatum inoculum

Seven different hosts,Panicum maximum, Chrysopogon fulvis, Themeda triandra, Chloris gayana, Brachiaria brizantha, Paspalum scrobiculatum andEleusine coracana were screened in order to select a better host for mass multiplication ofGlomus fasciculatum inoculum. Of these,Chloris gayana (Rhodes grass) was found to be the best host on the basis of root colonization and spore production and of the infective propagules of the potball.     

Close-Range Host Searching Behavior of the Stemborer Parasitoids <Emphasis Type="Italic">Cotesia sesamiae</Emphasis> and <Emphasis Type="Italic">Dentichasmias busseolae</Emphasis>: Influence of a Non-Host Plant <Emphasis Type="Italic">Melinis minutiflora</Emphasis>

Studies were conducted on the host searching behavior of the larval parasitoid Cotesia sesamiae (Cameron) (Hymenoptera: Braconidae) and the pupal parasitoid Dentichasmias busseolae Heinrich (Hymenoptera: Ichneumonidae), both of which attack lepidopteran (Crambidae, Noctuidae) cereal stemborers. The behavior of D. busseolae was observed in a diversified habitat that consisted of stemborer host plants (maize, Zea mays L. and sorghum, Sorghum bicolor (L). Moench (Poaceae)) and a non-host plant (molasses grass, Melinis minutiflora Beauv. (Poaceae)), while C. sesamiae was observed separately on host plants and molasses grass. In previous olfactometer studies, C. sesamiae was attracted to molasses grass volatiles while hboxD. busseolae was repelled. The aim of the present study was to investigate the influence of molasses grass on close-range foraging behavior of the parasitoids in an arena that included infested and uninfested host plants. Dentichasmias busseolae strongly discriminated between host and non-host plants, with female wasps spending most of the time on infested host plants and least time on molasses grass. Likewise, C. sesamiae spent more time on uninfested and infested host plants than it did on molasses grass in single choice bioassays. While on infested plants, the wasps spent more time foraging on the stem, the site of damage, than on other areas of the plant. Overall, the results indicate that presence of the non-host plant does not hinder close range foraging activities of either parasitoid.     

Host plant selection behaviour of Chilo partellus and its implication for effectiveness of a trap crop

Female lepidopterans can display a hierarchy of preference among potential host species, a trait thought to arise from the balance between attractants and deterrents to which the insects respond. Host plant ranking by moths and larvae of Chilo partellus Swinhoe (Lepidoptera: Crambidae), an important pest of cereals in Africa, was investigated, and whether eggs deposited on specific host plants yield larvae of particular host preferences. Trap plants are used in management of this pest. However, any ‘disagreement’ in host ranking between moths and larvae could potentially reduce effectiveness of trap crops as larvae emigrate to the main crop from the parent’s preferred trap plant. We also investigated whether host plant preference is influenced by the diet upon which larvae fed as part of an integrated assessment of the relationship between host plant selection and learning in C. partellus. Five host plants (all Poaceae) were used: maize (Zea mays L.), sorghum (Sorghum bicolor Moench), Napier grass (Pennisetum purpureum Schumach), and two varieties of signal grass [Brachiaria brizantha (A. Rich.) Stapf], viz., local (henceforth signal grass) and improved (‘Mulato’). In multiple choice tests, C. partellus female moths preferentially oviposited on Napier grass, followed by sorghum, maize, and signal grass, and least preferred ‘Mulato’. Larvae however equally orientated and settled on leaf cuts of maize, sorghum, signal grass, and Napier grass, but least preferred ‘Mulato’. Moreover, eggs from specific host plants did not yield larvae of particular host preferences. Furthermore, oviposition preference was not altered by the larval food. These results imply only a slight ‘disagreement’ in host ranking behaviour between moths and larvae, which is beneficial for trap cropping as larvae would not ‘reject’ the trap plant and appreciably disperse to the neighboring plants. Moreover, absence of larval learning behaviour indicates that regardless of the larval food C. partellus moths would still be attracted to the selected trap plant.     

Host preference and suitability of grasses for Oebalus pugnax

The rice stink bug, Oebalus pugnax (Fabricius) (Hemiptera: Pentatomidae: Carpocorini), though graminaceous, discriminates among its numerous host grass species. This could represent a feeding preference, it could be related to host suitability for growth and development. To clarify the role of host grass discrimination, two laboratory studies were conducted: (1) free‐choice tests to evaluate preferences of O. pugnax among 11 wild host grass species found in three rice‐producing counties of the central Mississippi Delta (MS, USA), and (2) no‐choice tests to evaluate the impact of rice (Oryza sativa L.), junglerice [Echinochloa colona (L.) Link], and dallisgrass (Paspalum dilatatum Poir.) (all Poaceae), on the development of O. pugnax from second instar to adult. In the free‐choice test, four experiments were conducted, each with four sets of host grass species and observed 1, 2, 4, 8, and 16 h after release in cages. Approximately 4 h was necessary for O. pugnax to settle on preferred host grasses. Oebalus pugnax showed a feeding preference for junglerice over all 10 other grass species. Bahiagrass, Paspalum notatum Flueggé, was the least preferred. The no‐choice tests showed significant effect of host grass species on O. pugnax mean development time of nymphal survival to adults. Survival of nymphs was lower and mean development time was longer on dallisgrass compared to rice and junglerice. Knowledge of O. pugnax rate of growth and development on host grasses could be useful in the future development of rice integrated pest management strategies.     

Parameter optimization for production of ligninolytic enzymes using agro-industrial wastes by response surface method

Lignin and manganese peroxidase (LiP, MnP) and laccase production by Phanerocheate chrysosporium was optimized by response surface methodology for brewery waste and apple pomace. The effect of moisture, copper sulphate, and veratryl alcohol (VA) concentrations on enzyme production was studied. Moisture and VA had significant positive effect on MnP and LiP production and the viability of P. chrysosporium (p < 0.05) and copper sulphate produced a negative effect. However, moisture and copper sulphate had a significant positive (p < 0.05) effect on laccase production, but VA had an insignificant positive effect (p < 0.05). Higher values of MnP, LiP and viability of P. chrysosporium on apple pomace (1287.5 U MnP/gds (units/gram dry substrate), 305 U LiP/gds, and 10.38 Log 10 viability) and brewery waste (792 U MnP/gds and 9.83 Log 10 viability) were obtained with 80% moisture, 3 mmol/kg VA, and 0.5 mmol/kg copper. LiP production in brewery waste (7.87 U/gds) was maximal at 70% moisture, 2 mmol/kg VA, and 1 mmol/kg copper. Higher production of laccase in apple pomace (789 U/gds) and brewery waste (841 U/gds) were obtained with 80% moisture, 3 mmol/kg VA, and 1.5 mmol/kg copper. Thus, moisture along with VA and copper sulphate was pertinent for the production of ligninolytic enzymes and increased cell viability.     

Transfer of endophyte-origin defensive alkaloids from a grass to a hemiparasitic plant

Plants growing in natural environments experience myriad interactions with a diverse assemblage of pathogens, parasites and mutualists. Many of these interactions involve symbiotic bacteria and fungi, but they also include macroparasitic plants. In this study, we investigated the interactions among a host grass (Lolium pratense, ex., Festuca pratensis), its symbiotic endophytic fungus (Neotyphodium uncinatum), a root hemiparasitic plant (Rhinanthus serotinus) of the host grass and a generalist herbivore (aphid Aulacorthum solani) of the hemiparasite. We demonstrate that the hemiparasitic plant acquires defending mycotoxins produced by the endophytic fungus living within their shared host grass. The uptake of defensive mycotoxins from the endophyte‐infected host grass enhances the resistance of the hemiparasitic plant to the generalist aphid herbivore. Endophyte infection increases the performance of the hemiparasitic plant, but reduces the growth of the host grass. In other words, the mutualistic endophytic fungus becomes parasitic in the presence of the hemiparasitic plant. Our results suggest that the outcomes of grass–endophyte interactions are conditional on the complexity of community‐level interactions; thus, the outcome of multispecies interactions may not be predictable from pair‐wise combinations of species.     

Inherited fungal symbionts enhance establishment of an invasive annual grass across successional habitats

Plants infected with vertically transmitted fungal endophytes carry their microbial symbionts with them during dispersal into new areas. Yet, whether seed-borne endophytes enhance the host plant’s ability to overcome colonisation barriers and to regenerate within invaded sites remains poorly understood. We examined how symbiosis with asexual endophytic fungi (Neotyphodium) affected establishment and seed loss to predators in the invasive annual grass Lolium multiflorum (Italian ryegrass) across contrasting successional plots. Italian ryegrass seeds with high and low endophyte incidence were sown into three communities: a 1-year-old fallow field, a 15-year-old grassland, and a 24-year-old forest, which conformed to an old-field chronosequence in the eastern Inland Pampa, Argentina. We found that endophyte infection consistently increased host population recruitment and reproductive output. Endophyte presence also enhanced aerial biomass production of ryegrass in a low recruitment year but not in a high recruitment year, suggesting that symbiotic effects on growth performance are density dependent. Endophyte presence reduced seed removal by rodents, although differential predation may not account for the increased success of infected grass populations. Overall, there was no statistical evidence for an endophyte-by-site interaction, indicating that the fungal endosymbiont benefitted host establishment regardless of large differences in biotic and abiotic environment among communities. Our results imply that hereditary endophytes may increase the chances for host grass species to pass various ecological filters associated with invasion resistance across a broad range of successional habitats.     

Egg size manipulation in the migrant skipper, Parnara guttata guttata (Lepidoptera: Hesperiidae), in response to different host plants

Female adults of the migrant skipper, Parnara guttata guttata, lay different-sized eggs on different host plants in different generations. Moreover, P. g. guttata maintains large egg size variation either in the population or in the individual. Why such phenotypic plasticity in egg size is maintained has not been clarified. In the present study we performed a series of experiments to verify whether or not females of P. g. guttata discriminate between the different host plants, i.e., rice plant Oriza sativa in the first and second generations and cogon grass Imperata cylindrica in the third (overwintering) generation and manipulate egg size accordingly on these host plants. When a caged female was allowed to lay eggs alternatively on soft-leafed rice plant and tough-leafed cogon grass, the size of the eggs laid on cogon grass was significantly larger than that on rice plant. When a caged female was allowed to lay eggs on the two host plants that were supplied on alternate days, the size of eggs laid on cogon grass was also significantly larger than that on rice plant. A preliminary experiment using crude extract from the plants suggested that females did not manipulate egg size in response to chemical stimulants alone. The skipper female was able to lay different-sized eggs instantaneously after assessing the host plant. However, the reaction norm to different host plants differed among females. Eggs of various sizes were matured in each ovariole, and egg size variation at the lowest part of the ovariole ranged from the size of the larger eggs laid on cogon grass to that of the smaller eggs laid on rice plant, although how the female chose the appropriate-sized egg at each occasion is unknown.     

Effect of crop rotations involving host and non-host plants on vesicular-arbuscular mycorrhizal infection of host plants

Summary The effects of crop rotations involving two host (lettuce and lavender) and two non-host (cabbage and radish) plants on the development of mycorrhizal infection in host plants were studied in unsterile soil and in sterilized soil with or without rock phosphate and inoculated withGlomus mosseae. As in previous experiments, pre-cropping with non-host plants did not decrease VA infection in the host plants. On the other hand, pre-cropping with a host plant increased VA infection in the same or another host plant grown afterwards. These effects were noted irrespectively of rock phosphate additions and of soil sterilization.     

Is the Cereal Rust Mite, Abacarus Hystrix Really a Generalist? – Testing Colonization Performance on Novel Hosts

The majority of eriophyoid mites are highly host specific and restricted to a narrow range of acceptable host plant species. The cereal rust mite, Abacarus hystrix was considered to be one of a few exceptions among them and has been found to be using a relatively wide host range. Since this species is a vagrant, inhabiting short-lived plants and aerially dispersing, it has commonly been considered to be a host generalist. Here the opposite hypothesis is tested, that host populations of A. hystrix are specialized on their local host plants and may represent host races. For this purpose, females from two host populations (quack grass, Agropyron repens and ryegrass, Lolium perenne) were transferred, and subsequently reared, on their normal (grass species from which females came from) and novel (other grass species) hosts. The female's fitness was assessed by survival and fecundity on the normal and novel host. Females of both populations had no success in the colonization of the novel host. They survived significantly better and had significantly higher fecundity on their normal host than on the novel one. These findings correspond with observations on host-dependent phenotype variability and host acceptance. The presence of locally specialized host populations in A. hystrix may be evidence for high host specificity among eriophyoids and the viruses they transmit. The main conclusion is that A. hystrix, which so far has been considered as a host generalist, in fact may be a complex species consisting of highly specialized host races.     

Oviposition acceptance and larval development of Chilo partellus stemborers in drought‐stressed wild and cultivated grasses of East Africa

Maternal host choices during oviposition by herbivorous insects determine the fitness of their offspring and may be influenced by environmental changes that can alter host‐plant quality. This is of particular relevance to ‘push‐pull’ cropping systems where host preferences are exploited to manage insect pest populations. We tested how drought stress in maize and companion plants that are used in these systems affect oviposition preference, larval feeding, and development of the spotted stemborer, Chilo partellus Swinhoe (Lepidoptera: Crambidae). Five host species were tested (all Poaceae): maize (Zea mays L.), Napier grass (Pennisetum purpureum Schumach), signal grass [Brachiaria brizantha (A. Rich) Stapf], Brachiaria cv. ‘Mulato’, and molasses grass [Melinis minutiflora (Beauv.)]. Under drought stress, maize experienced as much oviposition as control unstressed maize in choice and no‐choice experiments. Similarly, larval leaf damage was not significantly different in drought‐stressed vs. unstressed maize. In contrast, oviposition occurred less on drought‐stressed than on unstressed Napier and signal grass. Oviposition acceptance and leaf damage remained low in both drought‐stressed and unstressed molasses grass and Mulato. Larval survival and development remained high in drought‐stressed maize, but not in Napier, signal, and molasses grass and Mulato, where survival and development were low in both drought‐stressed and unstressed plants. Our results indicate that herbivore responses to drought‐stressed plants depend on the plant species and that drought stress can change host preference and acceptance rankings. In particular, trap‐crops such as Napier grass may not divert oviposition from the main maize crop under drought stress conditions.     

禾草内生真菌对其它微生物的影响研究进展

禾草内生真菌在宿主植物的茎叶等地上组织中普遍存在,不仅能够提高禾草对生物与非生物逆境的抗性,而且能够对周围环境中的不同微生物类群产生影响。主要总结了禾草Neotyphodium/Epichlo内生真菌对病原真菌、丛枝菌根真菌和土壤微生物的影响及其作用机理。发现禾草内生真菌普遍存在对病原真菌的抑制作用,而对丛枝菌根真菌存在不对称的竞争作用,且因种类而异。禾草内生真菌对土壤微生物群落的作用则会随着土壤类型和时间等外界因素发生变化。禾草内生真菌对不同类群微生物的影响机制主要包括:通过生态位竞争、抑菌物质分泌、诱导抗病性等对病原真菌造成影响;通过根系化学物质释放、营养元素调节、侵染条件差异等对丛枝菌根真菌造成影响;通过根际沉积物和凋落物等对土壤微生物群落造成影响。禾草内生真菌产生的生物碱能提高宿主植物对包括昆虫在内草食动物采食的抗性,影响病原菌的侵入、定殖和扩展;根组织分泌物中包含次生代谢产物能够抑制菌根真菌、土传病原真菌及其它土壤微生物的侵染与群落组成;也可能通过次生代谢物影响禾草的其它抗性。因此,禾草内生真菌在植物-微生物系统中的作用应该给予更多的关注和深入研究。     

Oviposition Choice of Two Fall Armyworm (Lepidoptera: Noctuidae) Host Strains

Fall armyworm, Spodoptera frugiperda (J. E. Smith), is a noctuid species that is composed of two morphologically identical sympatric host strains (corn and rice) that differ in their distribution among plant hosts. In an effort to explain observations of host fidelity in the field, ovipositional preference of the two strains on corn (Zea mays L.) or pasture grass (Cynodon nlemfuensis Vanderyst var. nlemfuensis) was determined using two greenhouse bioassays. In the first bioassay, corn strain females placed more eggmasses on the screen enclosure than on corn plants while grass plants contained an intermediate number of eggmasses. Rice strain females placed most of their eggmasses on grass plants. In the second bioassay, corn strain females placed an equal number of eggmasses on corn and grass plants in comparison to rice strain females which placed >3.5× more eggmasses on grass plants than on corn plants. Individual eggs as part of the eggmasses were also counted on plants and on the screen enclosure. Corn strain females equally placed eggs on the two host plants and on the screen enclosures, however rice strain females placed more eggs on grass plants compared to corn plants or the screen enclosure. This is the first report of consistent differential oviposition between corn and rice strain fall armyworm females.     

Specialisation pattern of the aphid Rhopalosiphum maidis is not modified by experience on a novel host

The effect of alternative host condition on the pattern of specialisation of the aphid Rhopalosiphum maidis (Fitch) was studied. R. maidis commonly occurs in Chile on Johnson grass (Sorghum halepense L.) but rarely on contiguous wheat (Triticum durum L.) crops. The performance of 23 clones of R. maidis on S. halepense (established host) and T. durum (novel host) before and after rearing on wheat for 20 asexual generations was evaluated. Prior and after the period of conditioning on wheat no negative correlation of performance parameters between both hosts was found. Only 8 out of 23 clones survived the 20 asexual generations on wheat. Further, after conditioning on wheat, survival of three out of eight clones increased on wheat and three clones improved r _m on Johnson grass but not on wheat. Although some genotypes of R. maidis were able to withstand wheat stressing conditions, the conditioning on this alternative host did not cause a decreased capacity to use Johnson grass as host. The results suggest that R. maidis performance on wheat is not genetically constrained, and also that conditioning on wheat cannot substantially modify this pattern.     

Exotic grass invasion impacts fitness of an endangered prairie butterfly, <Emphasis Type="Italic">Icaricia icarioides fenderi</Emphasis>

Fender’s blue butterfly is an endangered species restricted to fragmented, grassland remnants that are becoming increasingly dominated by tall, invasive grasses in western Oregon, USA. I performed a removal experiment to assess the impacts of structural degradation accompanying the invasion of Arrhenatherum elatius, tall oat grass, on butterfly fitness and fitness related behaviors. Clipping of A. elatius to native grass sward height resulted in 2.5–5 times as many eggs laid per leaf of host plant. Both male and female butterflies basked more frequently in areas removed of A. elatius inflorescences and upon encountering the treatment edge butterflies had a high rate of return into a large area removed of the grass inflorescences. Although butterfly behavior appeared to be affected by the change in sward height on the treatment edge, there was no evidence for the edge causing a disproportionate egg load. Invasion and dominance by A. elatius appeared to diminish host plant apparency which may result in overloading of eggs on conspicuous host plants, increased incidence of emigration, and a decrease in the likelihood of colonization because female butterflies appeared indifferent to larval resources beneath A. elatius inflorescences. Dominance of natural shortgrass prairies by tall stature grasses like A. elatius may be an insidious form of habitat degradation for grassland Lepidoptera worldwide, but it may go largely unnoticed because larval and adult resources can persist under the unnaturally tall grass canopy.     

Stimulation of vesicular-arbuscular mycorrhiza by fungicides or rhizosphere bacteria

Stimulation of vesicular-arbuscular (VA) mycorrhizal fungi may secure the early establishment of symbiosis and benefit the host plant at an earlier stage of development. The application of Bacillus mycoides resulted in particular in the acceleration of early VA mycorrhiza formation. An increase in vigour of the symbiosis could be measured later in terms of increased sporulation of the mycorrhizal fungi after shoot removal. Natural sporulation during later mycorrhizal development was affected by combination of bacteria and just one mycorrhizal isolate. The stimulation of mycorrhizal development was shown to be non-specific with regard to host plant and the isolate of the VAM fungus. However, the effect could not be achieved in all combinations of soil types and host plants. Application of the systemic fungicides triadimefon and pyrazophos promoted VAM formation. Combinations of fungicide and bacterial treatments were not synergistic.     

Mycorrhizal symbiosis increases growth,reproduction and recruitment of Abutilon theophrasti Medic. in the field

We examined in the field the effect of the vesicular-arbuscular (VA) mycorhizal symbiosis on the reproductive success of Abutilon theophrasti Medic., an early successional annual member of the Malvaceae. Mycorrhizal infection greatly enhanced vegetative growth, and flower, fruit and seed production, resulting in significantly greater recruitment the following year. In addition, the seeds produced by mycorrhizal plants were significantly larger and contained significantly more phosphorus than seeds from non-mycorrhizal plants, an effect which may improve offspring vigor. Infection by mycorrhizal fungi may thus contribute to the overall fitness of a host plant and strongly influence long-term plant population dynamics.     

Ecological significance of wing polymorphism in Fulgoroidea which inhabit tidal salt marshes

• 1 The vegetation of New Jersey tidal salt marshes is composed primarily of two grasses, Spartina patens, which occupies a narrow elevational zone of high marsh and varies little in structure from site to site, and Spartina alterniflora, an intertidal species which occurs as two spacially separated growth forms (tall and short). Fulgoroids, polymorphic for wing length, inhabit these grasses.
• 2 Populations of the common fulgoroid inhabiting short form S.alterniflora were composed of equal numbers of macropters and brachypters. Mesothoracic wings of brachypters were subequal in length to the abdomen allowing for short but inefficient flights compared to macropters.
• 3 Fulgoroids residing in S.patens produced mostly brachypters having small meso-and vestigial metathoracic wings and were incapable of flight.
• 4 Brachypter density of all fulgoroids was correlated with the seasonal increase in biomass of the host grass, while macropter density was not.
• 5 Peak macropter density occurred shortly before maximum biomass of the host grass was attained.
• 6 The production of macropterous forms was correlated with high levels of crowding incurred during nymphal stages.
• 7 Spatial and temporal variation in the structure of the host grasses and habitat reliability are suggested as important factors dictating the wing-polymorphism strategies of fulgoroids.