Number Of Host Plant Species Research Articles

Puke or poop? Comparison of regurgitate and faecal samples to infer alpine grasshopper (Paprides nitidus Hutton) diet in experimental plant communities.

Characterising plant-herbivore interactions is important to understanding the processes that influence community structure and ecosystem functioning. Traditional methods used to identify plant-herbivore interactions are being superseded by non-destructive molecular approaches that can infer interactions with greater resolution and accuracy from environmental DNA (e.g. faeces and regurgitate). However, few studies have compared the success of using different sample types and whether they provide similar or contrasting information about species' diet. Here we compared the success of DNA amplification and host plant species identification using restriction fragment length polymorphism (RFLP) applied to faecal and regurgitate samples collected from alpine grasshoppers Paprides nitidus Hutton during a grassland community mesocosm experiment. We found that DNA amplification success was 23% and 86% higher for faecal than regurgitate samples from female and male grasshoppers, respectively. In contrast, successful host plant identification using RFLP was 9% higher for regurgitate than faecal samples. The mean number of host plant species identified per sample (1.40) did not differ between sample types or grasshopper sexes. Of the 136 paired faecal-regurgitate samples, just 41% and 74% produced exactly or partially matching host plant identifications, respectively, indicating that different sample types provided complementary information about herbivore diet. Some plant species were more likely to be identified from faecal samples than expected by chance, and we found that this identification bias skewed towards plant species with higher investment in leaf tissue. We conclude that multiple sample types may be required to fully characterise an invertebrate herbivore species' diet.

Diversidade, distribuição e plantas hospedeiras de cochonilhas escama (Hemiptera: Diaspididae) no Espírito Santo, Brasil

Abstract: Armored scale insects (Hemiptera: Diaspididae), are phytophagous species that occur in major biogeographic regions of the world. Because of the importance of diaspidids as pests, there is widespread interest in countries that export and import unprocessed agricultural products in increased knowledge of this group which includes invasive and quarantine pests of great economic concern. The diversity, geographic distribution, and host of diaspidids were studied from November 2002 to December 2018 in 34 municipalities in the state of Espírito Santo, Brazil. Forty species of Diaspididae from 27 genera were collected and identified. The species Acutaspis perseae (Comstock), A. umbonifera (Newstead), Aonidiella aurantii (Maskell), Comstockaspis perniciosa (Comstock), Lepidosaphes beckii (Newman), Lepidosaphes gloverii (Packard), Morganella longispina (Morgan), Mycetaspis apicata (Newstead), and Thysanofiorinia nephelii (Maskel) were found for the first time in Espírito Santo. The plant families Myrtaceae, Moraceae, Arecaceae, Asparagaceae, and Rutaceae had the greatest number of host plant species of armored scale. Fifty-seven new host associations were observed for 25 species of diaspidids and 11 diaspidid species were recorded for the first time from nine families of plants. Selenaspidus articulatus (Morgan) was the most polyphagous species observed with 17 host plant species from 12 families, followed by Pseudaonidia trilobitiformis (Green), and Parlatoria proteus (Curtis). With these new records, 41 species and 28 genera of Diaspididae have been recorded in Espírito Santo.

The study of agricultural pests of the genus Liriomyza (Diptera: Agromyzidae) in Nagorno-Karabakh

The goal of the research is to study polyphagous species of the genus Liriomyza (Diptera, Agromyzidae) in Nagorno-Karabakh. The vegetable leaf-miner L. sativae (Blanchard, 1938), the tomato leaf-miner L. bryoniae (Kaltenbach, 1858) and the cabbage or serpentine leaf-miner L. brassicae (Riley, 1885) have been revealed among them. They affect mainly plants from the families Brassicaceae, Cucurbitaceae, Fabaceae, Solanaceae, Asteraceae. The quarantine species L. sativae has been described in the Caucasus for the first time. The paper presents distinctive features of the genus Liriomyza, a morpho-biological description of the imagoes, a structure of their wings, male genitalia, in particular the aedeagus, structural features of larvae and pupae of certain species, mines formed by the feeding of larvae, their harmfulness on the leaves of various plants. In terms of the number of host plant species, as well as the extensiveness and intensity of plant infection, the most common pest is L. sativae, the least common and harmful is L. brassicae. The larvae of L. sativae often mine the leaves of Phaseolus vulgaris and Solanum lycopersicum. Methods of a variance analysis have revealed that the sexual dimorphism of the studied species is most expressed in L. bryoniae.

Variable colour patterns indicate multidimensional, intraspecific trait variation and ecological generalization in moths

Animal colour patterns long have provided information about key processes that drive the ecological and evolutionary dynamics of biological diversity. Theory and empirical evidence indicate that variation in colour patterns and other traits among individuals generally improves the performance of populations and species, for example by reducing predation risk, increasing establishment success, improving resilience to environmental change, and decreasing risk of extinction. However, little is known about whether and how variation in colour pattern among species is associated with variation in other phenotypic dimensions. To address this issue, we analysed associations of colour pattern with morphological, behavioural and life‐history traits on the basis of data for nearly 400 species of noctuid moths. We found that moths with more variable colour patterns had longer flight activity periods, more diverse habitats and a greater number of host plant species than species with less variable colour patterns. Variable coloration in adult noctuid moths therefore can be considered as indicative of broader niches and generalist diets. Colour pattern variability was not significantly associated with overwintering stage or body size (wing span), and it was independent of whether the colour pattern of the larvae was non‐variable, variable or highly variable. Colour pattern variation during the larval stage tended to increase as the duration of the flight activity period increased, but was independent of the length of the larval period, diet breadth and habitat use. The realization that information on colour pattern variation in adult moths, and possibly other organisms, offers a proxy for niche breadth and dietary generalization can inform management and conservation biology.

Plant traits shape soil legacy effects on individual plant–insect interactions

Plant‐mediated soil legacy effects can be important determinants of the performance of plants and their aboveground insect herbivores, but, soil legacy effects on plant–insect interactions have been tested for only a limited number of host plant species and soils. Here, we tested the performance of a polyphagous aboveground herbivore, caterpillars of the cabbage moth Mamestra brassicae, on twelve host plant species that were grown on a set of soils conditioned by each of these twelve species. We tested how growth rate (fast‐ or slow‐growing) and functional type (grass or forb) of the plant species that conditioned the soil and of the responding host plant species growing in those soils affect the response of insect herbivores to conditioned soils. Our results show that plants and insect herbivores had lower biomass in soils that were conditioned by fast‐growing forbs than in soils conditioned by slow‐growing forbs. In soils conditioned by grasses, growth rate of the conditioning plant had the opposite effect, i.e. plants and herbivores had higher biomass in soils conditioned by fast‐growing grasses, than in soils conditioned by slow‐growing grasses. We show that the response of aboveground insects to soil legacy effects is strongly positively correlated with the response of the host plant species, indicating that plant vigour may explain these relationships. We provide evidence that soil communities can play an important role in shaping plant–insect interactions aboveground. Our results further emphasize the important and interactive role of the conditioning and the response plant in mediating soil–plant–insect interactions.

Host Specialization in Plant-galling Interactions: Contrasting Mites and Insects

Galling arthropods represent one of the most specialized herbivore groups. On an evolutionary scale, different taxa of insects and mites have convergently adapted to a galling lifestyle. In this study, we have used a multi-taxonomic approach to analyze the interaction specialization between gall-inducing mites and insects and their host plants in the Nitra City Park (Nitra, Slovakia). We used four ecological descriptors for describe plant-galling interactions: number of host plant species used by each arthropod species, galling specificity on host plant species (specificity), exclusivity of interactions between galling and plant species (specialization) and overlap of the interactions between arthropod species (similarity). We have found 121 species of gall-inducing arthropods, totaling 90 insects and 31 mites occurring on 65 host plant species. Our results reveal that mites have high specialization and low similarity of interactions in comparison to insects. A multiple-taxonomic comparison showed that these differences are triggered by gall-wasps (Hymenoptera: Cynipidae), the taxon with the lowest levels of specificity of plant-galling interactions (i.e., occurring on different host plant species). Our findings are indicative of different patterns of interaction between distinct gall-inducing arthropods taxa and their host plants, despite the ecological convergence of different taxa to a highly specialized herbivorous habitat.

Areas of endemism in the Nearctic: a case study of 1339 species of Miridae (Insecta: Hemiptera) and their plant hosts.

Areas of endemism are essential first hypotheses in investigating historical biogeography, but there is a surprising paucity of such hypotheses for the Nearctic region. Miridae, the plant bugs, are an excellent taxon to study in this context, because this group combines high species diversity, often small distribution ranges, a history of modern taxonomic revisions, and comprehensive electronic data capture and data cleaning that have resulted in an exceptionally error-free geospatial data set. Many Miridae are phytophagous and feed on only one or a small number of host plant species. The programs ndm/vndm are here used on plant bug and plant data sets to address two main objectives: (i) identify areas of endemism for plant bugs based on parameters used in a recent study that focused on Nearctic mammals; and (ii) discuss hypotheses on areas of endemism based on plant bug distributions in the context of areas identified by their host plant species. Given the narrow distribution ranges of many species of Miridae, the analytical results allow for tests of the prediction that areas of endemism for Miridae are smaller and more numerous, especially in the Western Nearctic, than are those of their host plants. Analyses of the default plant bug data set resulted in 45 areas of endemism, 35 of them north of Mexico and many located in the Western Nearctic; areas in the Nearctic are more numerous and smaller than those identified by mammals. The host plant data set resulted in ten areas of endemism, and even though the size range of areas is similar between the Miridae and plant data sets, the average area size is smaller in the Miridae data set. These results allow for the conclusion that the Miridae indeed present a valuable model system to investigate areas of endemism in the Nearctic.

DNA barcode variability and host plant usage of fruit flies (Diptera: Tephritidae) in Thailand.

The objectives of this study were to examine the genetic variation in fruit flies (Diptera: Tephritidae) in Thailand and to test the efficiency of the mitochondrial cytochrome c oxidase subunit I (COI) barcoding region for species-level identification. Twelve fruit fly species were collected from 24 host plant species of 13 families. The number of host plant species for each fruit fly species ranged between 1 and 11, with Bactrocera correcta found in the most diverse host plants. A total of 123 COI sequences were obtained from these fruit fly species. Sequences from the NCBI database were also included, for a total of 17 species analyzed. DNA barcoding identification analysis based on the best close match method revealed a good performance, with 94.4% of specimens correctly identified. However, many specimens (3.6%) had ambiguous identification, mostly due to intra- and interspecific overlap between members of the B. dorsalis complex. A phylogenetic tree based on the mitochondrial barcode sequences indicated that all species, except for the members of the B. dorsalis complex, were monophyletic with strong support. Our work supports recent calls for synonymization of these species. Divergent lineages were observed within B. correcta and B. tuberculata, and this suggested that these species need further taxonomic reexamination.

CytochromecOxidase I and CytochromebGene Sequences Indicate Low Genetic Diversity in South AfricanBusseola fusca(Lepidoptera: Noctuidae) from maize

The African maize stem borer, Busseola fusca, feeds on a limited number of host plant species (Calatayud et al. 2014), which include crops such as maize, pearl millet and sorghum. This pest occurs throughout sub-Saharan Africa where it causes economic damage to maize and sorghum crops (Kfir et al. 2002). In an attempt to combat lepidopteran stem borers, genetically modified Bt maize that express insecticidal Cry toxins were developed to kill larvae that feed on these plants (George et al. 2011). Bt maize was introduced into South Africa during 1998 and within the first decade after release, field-evolved resistance of B. fusca to Bt maize was reported (Van Rensburg 2007). Since this first report, resistant populations have been reported from several parts of the maize-production region of South Africa (Kruger et al. 2011; Van den Berg et al. 2013). Explanations provided for this rapid resistance development were confined to agronomical reasons (VanRensburg 2007; Kruger et al. 2009, 2011),non-compliance to refuge requirements (Kruger etal. 2009) and non-recessive inheritance of resistance (Campagne et al. 2013). Notmuchis however understood about the molecular genetics of B.fusca. Previously, Sezonlin et al. (2006b) noted that limited population genetic and phylogeography data are available for B. fusca.

Evolutionary conserved function of barley and Arabidopsis 3-KETOACYL-CoA SYNTHASES in providing wax signals for germination of powdery mildew fungi.

For plant pathogenic fungi, such as powdery mildews, that survive only on a limited number of host plant species, it is a matter of vital importance that their spores sense that they landed on the right spot to initiate germination as quickly as possible. We investigated a barley (Hordeum vulgare) mutant with reduced epicuticular leaf waxes on which spores of adapted and nonadapted powdery mildew fungi showed reduced germination. The barley gene responsible for the mutant wax phenotype was cloned in a forward genetic screen and identified to encode a 3-KETOACYL-CoA SYNTHASE (HvKCS6), a protein participating in fatty acid elongation and required for synthesis of epicuticular waxes. Gas chromatography-mass spectrometry analysis revealed that the mutant has significantly fewer aliphatic wax constituents with a chain length above C-24. Complementation of the mutant restored wild-type wax and overcame germination penalty, indicating that wax constituents less present on the mutant are a crucial clue for spore germination. Investigation of Arabidopsis (Arabidopsis thaliana) transgenic plants with sense silencing of Arabidopsis REQUIRED FOR CUTICULAR WAX PRODUCTION1, the HvKCS6 ortholog, revealed the same germination phenotype against adapted and nonadapted powdery mildew fungi. Our findings hint to an evolutionary conserved mechanism for sensing of plant surfaces among distantly related powdery mildews that is based on KCS6-derived wax components. Perception of such a signal must have been evolved before the monocot-dicot split took place approximately 150 million years ago.

The effect of multiple host species on a keystone parasitic plant and its aphid herbivores

Summary The exploitation of shared resources by diverse organisms underpins the structure of ecological communities. Hemiparasitic plants and the insect herbivores feeding on them both rely, directly and indirectly, on the resources supplied by the parasite's host plant. Therefore, the identity and number of host plant species providing these resources is likely to be critical for parasite and herbivore performance. We tested the effect of single and multiple host species on the biomass of the generalist parasitic plant Rhinanthus minor and the abundance of its aphid (Aphis gossypii) herbivores. Parasite biomass was proportional to the number of haustorial connections to host roots and was determined by host species identity rather than host functional group. Host species identity was also an important influence on aphid population size, and parasites attached to Lotus corniculatus experienced a considerable reduction in aphid herbivory. The effects on the parasite attaching to multiple hosts depended on the combination of species present. However, host mixtures generally benefitted aphids by diluting the negative effects of particular host species. Our findings suggest that the specificity of host attachment alters the impact of this keystone parasitic plant on its own herbivores and, potentially, on the wider plant and herbivore community.

Nest architecture and use of floral oil in the oil-collecting South African solitary bee Rediviva intermixta (Cockerell) (Hymenoptera: Apoidea: Melittidae)

Nest architecture, use of floral oil for brood cell lining and pollen collecting are described for the first time for the genus Rediviva, using the South African endemic oil-collecting solitary bee species Rediviva intermixta. The nest consists of a dead-end vertical tunnel with a single brood cell located at the end of each of several horizontally branching lateral tunnels. Brood cells are lined with a thin layer of waxy material, presumably derived from chemically modified floral oil. Rediviva intermixta is a pollen generalist but relies on a small number of host plant species for oil-collecting. Brood cells are provisioned with pollen from at least six plant families, but with a preference for non-oil-producing Scrophulariaceae. The nesting biology and Dufour’s gland size of the species are discussed and compared with the closely related genera Melitta and Redivivoides (non-oil-collecting) and Macropis (oil-collecting). The differences between Macropis and Rediviva suggest that oil-collecting in the two genera evolved independently.

Biological control reduces herbivore’s host range

The enemy release hypothesis predicts that alien populations are more vigorous and grow faster in introduced areas than within their natural range due to lack of natural enemies. An extension of this theory would be that the lack of natural enemies on an herbivore species will indirectly increase the number of host plant species that it can infest. The eucalyptus gall wasp Ophelimus maskelli is a recent introduction to the Mediterranean basin. Its arrival was followed after about two years by its parasitoid, Closterocerus chamaeleon. We evaluated the range of hosts used by the gall wasp by surveying 50 Eucalyptus species, 37 Eucalyptus hybrids and 18 E. globulus half-sibling families, before and after the establishment of the parasitoid. We found a consistent reduction in the observed host range of the gall wasp after the establishment of the parasitoid with a reduction of 83% on Eucalyptus species, 84% on hybrids, and 94% on E. globulus half-siblings. Host range narrowed down from 18 to three closely-related host species, all in the section Exsertaria, series Exsertae, E. camaldulensis, E. tereticornis and E. rudis, which are probably the standard hosts of O. maskelli. In the remaining affected species the intensity of attack decreased significantly in all studied regions. These findings show that, besides the direct gains from classical biological control, there may be indirect benefits through a natural-enemy-induced reduction in the range of host plants used by herbivorous insect pests.

먹이식물·흡밀식물·식생이 나비 군집에 미치는 영향

본 연구는 먹이식물과 흡밀식물의 수 그리고 식생이 나비의 개체수 및 다양성에 미치는 영향을 조사하기 위하여 2008-09년까지 충북 보은군 속리산 법주사 지역을 4개 구간으로 나누어 모니터링을 실시하였으며 이를 단순회귀분석 및 다중회귀분석하였다. 그 결과 나비 개체수와 식물종수, 흡밀식물 그리고 먹이식물 수를 다중회귀분석 한 결과에서 상관관계를 보였으며, 서식지 면적이 클수록 개체수는 많아지는 것으로 나타났다. 그러나 단순회귀 분석 시 나비의 종수와 다양도지수는 먹이식물 수 및 구간면적과 각각 낮은 상관관계를 나타냈다. 또한 보다 다양한 식생을 보이는 구간에서 나비 종수가 증가하였다. 나비의 다양성과 개체군 보전을 위해서는 다양한 수종의 식물과 함께 나비의 먹이식물과 흡밀식물이 복합적으로 분포하고, 식생은 각각의 요소들이 서로 보완관계를 유지할 수 있도록 다른 형태로 존재하는 것이 필요함을 시사한다. The effects of number of host plants and nectar plants on the number and diversity of butterflies were monitored and analyzed by simple and multiple regression from May 2008 to Sep 2009 in the Bubjusa region (Mt. Sokri, Boeun-gun, Chungcheongbuk-do), which was divided into four regions. The results demonstrate that the number of butterflies has a positive correlation with the number of host plant species, the number of nectar plant species, and the number of host plants multiple regression analysis. The number of butterflies also increased habitat area. However, the butterfly species number and diversity index showed lower correlation with the number of host plants and the area size of the divided region, respectively, when analyzed by simple regression. In addition, increased species diversity in a region with more diverse plant flora. These results suggest that the composite distribution of host and nectar plants with diverse plant flora is required for butterfly diversity and population preservation. Additionally, it also suggest that vegetation types complementarity all factors.

Moscas-das-frutas (Diptera, Tephritidae) no Estado de Goiás: ocorrência e distribuição

O Estado de Goiás apresenta grande número de espécies vegetais hospedeiras de moscas-das-frutas, cujos frutos amadurecem em diferentes estações do ano, proporcionando o aumento da densidade populacional da praga e sua ampla distribuição. Em todo o território goiano, são observadas moscas-das-frutas em alta ou baixa frequência, tanto em áreas rurais quanto urbanas. Além da mosca-do-mediterrâneo (Ceratitis capitata), são conhecidas, até o momento, 21 espécies de moscas do gênero Anastrepha, destacando-se as espécies A. obliqua, A. fraterculus, A. sororcula e A. zenildae, pela importância econômica, e A. grandis, pelo destaque como praga quarentenária. A espécie A. grandis foi registrada, até o momento, em 13 municípios goianos, porém, esta informação não inviabiliza os programas de exportação de frutos implantados no Estado, pois verificou-se que, nas unidades de produção, o índice MAD (moscas armadilha-1 dia-1) foi inferior a 0.1, mantendo-se dentro dos índices estabelecidos pela legislação, para a exportação de frutos de cucurbitáceas.

Parasitism and haustorium anatomy of Krameria lappacea (Dombey) Burdet & B.B. Simpson (Krameriaceae), an endangered medicinal plant from the Andean deserts

Krameria lappacea (Rhatany or Ratanhia, Krameriaceae) is an endangered, overexploited medicinal plant from the semi-deserts of Andean South America, and is destructively harvested from nature. There are published data on parasitism of Krameria from three North American species, but not on K. lappacea, the only economically important species. The present study investigates the presence or absence of hemiparasitism, host plant range and haustorium morphology/anatomy. The study was carried out at two sites in Peru, Department Arequipa, Prov. Arequipa. Hemiparasitism was confirmed, with 106 haustorical connections to 18 host plant species from 17 genera and 12 plant families observed, nearly doubling the number of host plant species known for Krameria (incl. four additional angiosperm families). Root and haustorium architecture and anatomy were found to be similar to the North American species. K. lappacea is a highly generalistic hemiparasite and host distribution and abundance are likely not limiting factors for Krameria recruitment and establishment. Due to its wide range of host plants K. lappacea likely influences the performance of the bulk of perennial species in its habitat and overcollection affects the overall vegetation. Conservation strategies and adequate management should have high priority because of the likely ecological and known economical importance of this species.

Cotton leaf curl Multan betasatellite as a plant gene delivery vector trans-activated by taxonomically diverse geminiviruses

Cotton leaf curl Multan betasatellite (CLCuMB) replicates in tobacco, tomato and datura plants in the presence of the helper viruses tomato leaf curl virus-Australia, Iranian isolates of tomato yellow leaf curl virus, tomato leaf curl Karnataka virus, and beet severe curly top virus (BSCTV). Infectious recombinant CLCuMB constructs were made in which segments of either the CaMV 35S or the petunia ChsA promoter replaced the CLCuMB βC1 ORF, and these were designated pBinβΔC1-35S and pBinβΔC1-ChsA, respectively. Inoculation of tobacco plants containing a functional 35S-GUS transgene with pBinβΔC1-35S, and normal petunia plants with pBinβΔC1-ChsA, in the presence of helper viruses resulted in silencing of GUS and ChsA activities in transgenic tobacco and non-transgenic petunia plants, respectively. Replication of CLCuMB with different geminiviruses, especially BSCTV, a curtovirus with a broad host range, makes it a valuable gene delivery vector to the large number of host plant species of geminiviruses that support CLCuMB.

Population Abundance ofFrankliniella occidentalis(Thysanoptera: Thripidae) and Natural Enemies on Plant Hosts in Central Chile

Populations of the invasive Frankliniella occidentalis (Pergande) are serious pests of agricultural crops in the Aconcagua Valley of central Chile. An extensive survey was conducted of 55 plant species in 24 families to identify plant hosts of F. occidentalis and to determine its relative abundance on each host during each season. A more intensive study was conducted on selected plant species serving as reproductive hosts to determine the population dynamics of F. occidentalis and to evaluate the potential importance of Orius species and other natural enemies for controlling F. occidentalis. Adults of F. occidentalis were active during each season of the year inhabiting the flowers of 91% of the sampled plant species in 22 families, and 86% of these plant species in 19 families served as reproductive hosts. The number of host plant species used was greatest in the spring and least in the winter. All of the hosts except Medicago sativa L. were used only when flowering. Populations of F. occidentalis were significantly aggregated in M. sativa in the terminal buds over the leaves when the host was not flowering, and in the flowers, followed by the terminal buds, followed by the leaves when the host was flowering. Larvae were 1.3-2.3 times more abundant on dates when M. sativa was flowering. There were no identifiable patterns in plant hosts based on endemicity or plant family. Most of the plant species used by F. occidentalis were inferior quality hosts where populations either declined or were stable. Populations of F. occidentalis on low-quality hosts generally escaped predation by Orius species and competition by other species of thrips. Only 25% of the food hosts and 28% of the reproductive hosts for F. occidentalis in the extensive survey, respectively, were host plants for Orius. Parasitoids and other predators were not found to be important in suppressing thrips on any of the plant hosts. Populations of F. occidentalis increased on only a few hosts, including M. sativa and Sisymbrium officinale L. Scop. These apparently are major sources of F. occidentalis adults invading crops. We conclude that F. occidentalis is established in central Chile and that it has replaced and possibly displaced the native Frankliniella australis (Morgan) as the most common thrips species.

The role of wild host plants in the abundance of lepidopteran stem borers along altitudinal gradient in Kenya

Presence of wild host plants of stem borers in cereal-growing areas has been considered as reservoirs of lepidopteran stem borers, responsible for attack of crops during the growing season. Surveys to catalogue hosts and borers as well as to assess the abundance of the hosts were carried out during the cropping and non-cropping seasons in different agro-ecological zones along varying altitude gradient in Kenya. A total of 61 stem borer species belonging to families Noctuidae (25), Crambidae (14), Pyralidae (9), Tortricidae (11) and Cossidae (2) were recovered from 42 wild plant species. Two noctuids, Busseola fusca (Fuller), Sesamia calamistis Hampson, and two crambids, Chilo partellus (Swinhoe) and Chilo orichalcociliellus (Strand) were the four main borer species found associated with maize plants. In the wild, B. fusca was recovered from a limited number of host plant species and among them were Sorghum arundinaceum (Desvaux) Stapf, Setaria megaphylla (Steudel) T. Durand & Schinz, Arundo donax L. and Pennisetum purpureum Schumacher. In contrast, the host range of C. partellus was considerably wider [13 for S. calamistis]. However, the number of larvae of these species was lower in the wild compared to cultivated fields, thus the role of natural habitat as a reservoir for cereal stem borers requires further studies. Importance of the wild host plants as well as borer diversity along the altitudinal gradient is discussed.

Investigating the Disparity in Host Specificity between AM and EM Fungi: Lessons from Theory and Better-Studied Systems

Over 80% of vascular plant species are associated with some type of mycorrhizal fungus (Trappe 1987). These associations are thought to be mutualistic in many cases, with the host plant exchanging photosynthate with the fungus in return for mineral nutrients (Harley and Smith 1983, Smith and Read 1997). The two most abundant and studied mycorrhizal types are ectomycorrhizal (EM) fungi and arbuscular mycorrhizal (AM) fungi. A generally agreed-upon phenomenon is that AM fungi are broad generalists with respect to the number of host plant species with which they can associate (Smith and Read 1997). Because of the difficulty of detecting variation in the relative abundances of AM fungal species on plant roots, as well as the difficulty of understanding the causes (environmental factors, host genotype, interspecific interactions) of such variation, there exist gaps in our knowledge about the extent to which AM fungal species associate with different plant species, especially in complex natural fungal communities. However, based on evidence accumulated so far from field and laboratory observations, AM fungi exhibit broad host ranges, and the rare exceptions to this (e.g., Graw et al. 1979) must not be allowed to cloud the observation that VA mycorrhizal fungi and their host plants have generally non-specific (Smith and Read 1997). In contrast, specificity among EM fungi ranges from very broad to extremely specific, with many EM fungi associating with only a single host plant species (Janos 1 980a, Alexander 1989, Harley 1989, Borowicz and Juliano 1991, Molina et al. 1992, Smith and Read 1997). Explanations for the disparity in host specificity between the two types of fungi have been mentioned briefly in other contexts, but have not been developed, tested, or compared with other potential explanations (e.g., Janos 1980b, 1983, Malloch et al. 1980, Connell and Lowman 1989, Molina et al. 1992). There is clearly a need to explicitly develop and test a set of hypotheses explaining the higher incidence of host-specificity among EM fungi than among AM fungi. The general topic of specificity is one of broad interest to ecologists and evolutionary biologists, as the degree of specificity in interactions is predicted to strongly influence the nature of evolution of those interactions (e.g., whether two species co-evolve) (Janzen 1980, Thompson 1994). As a result, it has received a great deal of attention both theoretically and empirically. Much of this work has focused on specificity in interactions between plants and their herbivores (e.g., Futuyma and Moreno 1988, Berenbaum 1996), pollinators (e.g., Kiester et al. 1984, Waser et al. 1996), and fruit dispersers (e.g., Jordano 1987, Fleming et al. 1993). The voluminous literature generated from investigations of these three types of interactions provides valuable information and predictions about specificity phenomena. Many of these predictions are particular to specific systems, but some are very general and could aid in attempts to understand specificity in mycorrhizal mutualisms. However, these results have not been utilized to help understand the disparity in host specificity between AM and EM fungi. Here I discuss three principles regarding the evolution of specificity that emerge from an examination of the plant-herbivore, plant-pollinator, and plant-fruit-disperser literature and other theoretical literature. These three principles suggest three hypotheses (not mutually exclusive) for the disparity in host specificity between AM and EM fungi, which I discuss and evaluate.