New species and record of <Emphasis Type="Italic">Zygophiala</Emphasis> on apple fruit from China

Up to now, four species of Zygophiala have been recorded, most of them as agents of flyspeck disease on apples. Two species of Zygophiala associated with flyspeck on apple in China are described in this paper. Zygophiala cylindrica is described as a new fungal species based on morphological characteristics and analysis of DNA sequences, and a phylogenetic analysis of the DNA sequences data is presented. Zygophiala cryptogama is recorded for the first time in China.     

Herbivory by Strongylocoris leucocephalus (Hemiptera: Miridae) on a novel host plant Adenophora triphylla var. japonica in Japan

When monophagous and oligophagous insect herbivores colonize new areas, they sometimes use novel hosts. The availability of the new hosts can facilitate further expansion into regions beyond the geographic range of the original hosts, resulting in specialization on different host plant taxa in different parts of the herbivore's geographic range. Strongylocoris leucocephalus Linnaeus (Hemiptera: Miridae), which is a plant bug attacking Campanula spp., is widely distributed in the Eurasian continent, North Africa, and northern Japan. In the process of geographic range expansion, S. leucocephalus may incorporate novel host plants into their host range. I investigated the host plant species of S. leucocephalus in central Japan. Field observations revealed that the plant bug fed on the novel host plant Adenophora triphylla (Thunb.) A. DC. var. japonica (Regel) H. Hara (Campanulaceae), although feeding by S. leucocephalus was not associated with plant mortality. However, S. leucocephalus never fed on Campanula punctata Lam. var. hondoensis (Kitam.) Ohwi, the only Campanula species at the study site. The plant bug S. leucocephalus and the novel host plant A. triphylla var. japonica are not entirely distributed sympatrically, suggesting that the plant bug has expanded its geographic range by incorporating new hosts.     

A new species of Devriesia causing sooty blotch and flyspeck on Rubber Trees in China

Sooty blotch and flyspeck is a fungal disease complex that colonizes a wide range of plants. In a survey of host plants for sooty blotch and flyspeck fungi, we obtained an isolate associated with discrete flyspeck symptom on stems of the Rubber Trees, Ficus elastica, from Haikou, Hainan, China. A pure culture was obtained, and the nuclear ITS region of rDNA was amplified by PCR. Molecular phylogeny inferred from ITS sequence data suggested that it was close to Devriesia strelitziae, reported from South Africa. Morphologically, it was characterized by longer conidia, more conidial septa, and having chlamydospores. Therefore, we describe our isolate as a novel species of Devriesia.     

Comparative phylogenetic relationships and genetic structure of the caterpillar fungus Ophiocordyceps sinensis and its host insects inferred from multiple gene sequences

Ophiocordyceps sinensis (Ascomycota: Ophiocordycipitaceae) is a native fungal parasite of Hepialidae caterpillars and one of the most economically important medicinal caterpillar fungi in China. However, little is known about the phylogenetic and evolutionary relationships between O. sinensis and its host insects. In this study, nuclear ITS and β-tubulin sequences from O. sinensis and mitochondrial COI, COII, and Cytb sequences from its hosts were analyzed across 33 populations sampled from five regions in China. Phylogenetically, both O. sinensis and its hosts were divided into three geographically correlated clades, and their phylogenies were congruent. Analysis of molecular variance and calculated coefficients of genetic differentiation revealed significant genetic divergence among the clades within both O. sinensis (F_ST= 0.878, N_ST=0.842) and its hosts (F_ST=0.861, N_ST=0.816). Estimated gene flow was very low for O. sinensis (Nm=0.04) and the host insects (Nm=0.04) among these three clades. Mantel tests demonstrated a significant correlation (P<0.01) between the genetic distances for O. sinensis and its hosts, as well as a significant association (P<0.05) between geographic and genetic distances in both. The similar phylogenetic relationships, geographic distributions, and genetic structure and differentiation between O. sinensis and its hosts imply that they have coevolved.     

Geographic variation in feeding preference of a generalist herbivore: the importance of seaweed chemical defenses

The ecological impacts of generalist herbivores depend on feeding preferences, which can vary across and within herbivore species. Among mesoherbivores, geographic variation in host use can occur because host plants have a more restricted geographic distribution than does the herbivore, or there is local evolution in host preference, or both. We tested the role of local evolution using the marine amphipod Ampithoe longimana by rearing multiple amphipod populations from three regions (subtropical Florida, warm-temperate North Carolina and cold-temperate New England) and assaying their feeding preferences toward ten seaweeds that occur in some but not all regions. Six of the ten seaweeds produce anti-herbivore secondary metabolites, and we detected geographic variation in feeding preference toward five (Dictyota menstrualis, Dictyota ciliolata, Fucus distichus, Chondrus crispus and Padina gymnospora, but not Caulerpa sertularioides). Amphipod populations that co-occur with a chemically-rich seaweed tended to have stronger feeding preferences for that seaweed, relative to populations that do not co-occur with the seaweed. A direct test indicated that geographic variation in feeding preference toward one seaweed (D. ciliolata) is mediated by feeding tolerance for lipophilic secondary metabolites. Among the four seaweeds that produce no known secondary metabolites (Acanthophora, Ectocarpus, Gracilaria and Hincksia/Feldmannia spp.), we detected no geographic variation in feeding preference. Thus, populations are more likely to evolve greater feeding preferences for local hosts when those hosts produce secondary metabolites. Microevolution of feeding behaviors of generalist marine consumers likely depends on the availability and identity of local hosts and the strength of their chemical defenses.     

Factors affecting host range in a generalist seed pathogen of semi-arid shrublands

Generalist pathogens can exhibit differential success on different hosts, resulting in complex host range patterns. Several factors operate to reduce realized host range relative to potential host range, particularly under field conditions. We explored factors influencing host range of the naturally occurring generalist ascomycete grass seed pathogen Pyrenophora semeniperda. We measured potential host range in laboratory experiments at high inoculum loads with 26 grass species, including the primary host Bromus tectorum, and developed models to predict susceptibility and tolerance based on host traits, including germination speed, seed hardness, seed size, and phylogenetic relations. We also examined pathogen and host density effects on infection and mortality. All species tested were at least somewhat susceptible to the pathogen at high inoculum loads, but both infection and mortality varied widely. Species more closely related to the original host (B. tectorum) were more susceptible to infection, whereas species with slower germination were less tolerant and therefore more likely to suffer mortality. Infection and mortality were sharply reduced as inoculum load was reduced. Intermediate loads had major negative impacts on dormant B. tectorum seeds but generally minimal effects on native species. In addition, field seed bank studies determined that P. semeniperda rarely exploits native grass species as hosts. This marked reduction in realized host range relative to potential host range indicates that laboratory host range studies are potentially a poor predictor of either the current or possible future realized host range for wildland plant pathogens.     

Can You Judge a Disease Host by the Company It Keeps? Predicting Disease Hosts and Their Relative Importance: A Case Study for Leishmaniasis

Zoonoses are an important class of infectious diseases. An important element determining the impact of a zoonosis on domestic animal and human health is host range. Although for particular zoonoses some host species have been identified, until recently there have been no methods to predict those species most likely to be hosts or their relative importance. Complex inference networks infer potential biotic interactions between species using their degree of geographic co-occurrence, and have been posited as a potential tool for predicting disease hosts. Here we present the results of an interdisciplinary, empirical study to validate a model based on such networks for predicting hosts of Leishmania (L.) mexicana in Mexico. Using systematic sampling to validate the model predictions we identified 22 new species of host (34% of all species collected) with the probability to be a host strongly dependent on the probability of co-occurrence of vector and host. The results confirm that Leishmania (L.) mexicana is a generalist parasite but with a much wider host range than was previously thought. These results substantially change the geographic risk profile for Leishmaniasis and provide insights for the design of more efficient surveillance measures and a better understanding of potential dispersal scenarios.     

Specificity of attachment sites of larval water mites (Hydrachnidia, Acari) on their insect hosts (Chironomidae, Diptera) – evidence from some stream-living species

This study concerns the parasite-host associations of water mite larvae and their chironomid hosts in a small stream on the North German Plain. The different feeding sites on the host were tested as to whether they represented a strategy of the parasites regarding host partitioning. The attachment sites of nine ectoparasitic water mite species were observed in detail: Aturus fontinalis, Atractides nodipalpis, Feltria rouxi, Hygrobates nigromaculatus, Protzia eximia, Sperchonopsis verrucosa, Sperchon clupeifer, S. setiger and Lebertia inaequalis. Aturus fontinalis, A. nodipalpis, F. rouxi and H. nigromaculatus distinctly preferred sites on the abdomen of the host, whereas the other species preferred feeding sites on the thorax. The four species that preferentially attached to the abdomen of the host showed a distinct specificity for selected segmental and/or intersegmental regions. All species differed in their sites along the length of the abdomen. The order of attachment on the abdominal segments was, from anterior to posterior: H. nigromaculatus, F. rouxi, A. fontinalis and A. nodipalpis. The sites were analysed with regard to segmental and intersegmental attachment, the proportion of dorsal and ventral sites and the differences between attachment to different host species. Larvae attached to their hosts as single individuals showed only slight differences from the sites of mites on hosts that carried many mite larvae. The finding that less than 10% of the chironomids were parasitized by more than one water mite species suggested that, at least in the zoocoenosis of the studied collecting site, the interspecific competition for attachment sites was not strong. However, the specificity of attachment sites clearly had the potential of diminishing competition between water mite species by host partitioning. Intra- and interspecific competition for preferred sites and preparasitic constraints are discussed.     

Zoogeography and host associations of the Heterodoxus octoseriatus group and H. ampullatus (Phthiraptera: Boopiidae) from rock-wallabies (Marsupialia: Petrogale)

Species of the Heterodoxus octoseriatus group infest five species, comprising eight chromosome races, of Petrogale in Queensland and northern New South Wales, Australia. The precise host and geographic ranges of the 11 species of the H. octoseriatus group were determined. Individual hosts and host populations were infested by single species of lice only. The geographic ranges of lice were discrete. In some cases the geographic ranges of louse species and their hosts were approximately congruent. In others they were completely incongruent and it was unclear which species originally infested which hosts or even which was the most recent colonizer. In at least one case, expansion of the geographic range of one species of louse apparently led to fragmentation of the range of another and subsequently, to allopatric speciation.     

我国鱊头槽绦虫的鱼类宿主种类及其地理分布

本文结合野外调查数据和文献资料,报道了鱊头槽绦虫(Bothriocephalus acheilognathi)在我国感染的鱼类宿主种类及其地理分布。鱊头槽绦虫是一种世界性广布鱼类寄生绦虫;它起源于亚洲地区并伴随着宿主鱼类向外引种在世界范围内广泛扩散。在我国鱊头槽绦虫广泛分布于从北至南的自然水域或养殖水体中(辽河、海河、额尔齐斯河、伊犁河、黄河、淮河、长江、闽江、珠江等流域);感染宿主鱼类达31种,其中鲤科(Cyprinidae)26种、鳢科(Channidae)1种、塘鳢科(Eleotridae)1种、慈鲷科(Cichlidae)1种、胎鳉科(Poeciliidae)2种。在调查的各水系野生鱼类中,马口鱼(Opsariichthys bidens)和赤眼鳟(Squaliobarbus curriculus)具有较高的感染率;各大流域池塘养殖的草鱼(Ctenopharyngodon idella)几乎都有头槽绦虫的寄生。作者根据头槽绦虫的流行特征认为马口鱼和赤眼鳟可能为该绦虫在自然水体中的主要宿主。     

Aphids (Hemiptera,Aphididae) on ornamental plants in greenhouses in Bulgaria

Investigations on the species composition and host range of aphids on ornamental greenhouse plants in Bulgaria was conducted over a period of five years, from 2008 to 2012. Twenty greenhouses, growing ornamentals for landscaping, plant collections and other purposes were observed. They were located in the regions of Sofia, Plovdiv, Smolyan, Pavlikeni, Varna and Burgas. The total number of collected aphid samples was 279. Their composition included 33 aphid species and one subspecies from 13 genera and 5 subfamilies. Twenty-eight species were found to belong to subfamily Aphidinae. Almost 70 % of all recorded species were polyphagous. The most widespread aphid species was Myzus persicae, detected in 13 greenhouses all year round, followed by Aulacorthum solani (10 greenhouses) and Aphis gossypii (9 greenhouses). The widest host range was shown by Myzus persicae (43 hosts), Aulacorthum solani (32 hosts) and Aulacorthum circumflexum (23 hosts).The list of host plants includes 114 species from 95 genera and 58 families. The greatest variety of aphid species was detected on Hibiscus (9 species). Out of all aphid samples 12.9 % were collected on Hibiscus and 6.8 %, on Dendranthema. The greatest variety of aphid species was detected on Hibiscus (9 species).Periphyllus californiensis and Aphis (Aphis) fabae mordvilkoi are reported for the first time for Bulgaria. Furthermore, Aphis spiraecola has been found in new localities and has widened its host range in this country.     

Population Genetics of Schistosoma japonicum within the Philippines Suggest High Levels of Transmission between Humans and Dogs

Background

Schistosoma japonicum, which remains a major public health problem in the Philippines and mainland China, is the only schistosome species for which zoonotic transmission is considered important. While bovines are suspected as the main zoonotic reservoir in parts of China, the relative contributions of various non-human mammals to S. japonicum transmission in the Philippines remain to be determined. We examined the population genetics of S. japonicum in the Philippines in order to elucidate transmission patterns across host species and geographic areas.

Methodology/Principal Findings

S. japonicum miracidia (hatched from eggs within fecal samples) from humans, dogs, pigs and rats, and cercariae shed from snail-intermediate hosts, were collected across two geographic areas of Samar Province. Individual isolates were then genotyped using seven multiplexed microsatellite loci. Wright''s F_ST values and phylogenetic trees calculated for parasite populations suggest a high frequency of parasite gene-flow across definitive host species, particularly between dogs and humans. Parasite genetic differentiation between areas was not evident at the definitive host level, possibly suggesting frequent import and export of infections between villages, although there was some evidence of geographic structuring at the snail–intermediate host level.

Conclusions/Significance

These results suggest very high levels of transmission across host species, and indicate that the role of dogs should be considered when planning control programs. Furthermore, a regional approach to treatment programs is recommended where human migration is extensive.     

Gene flow between alien and native races of the holoparasitic angiosperm Orobanche minor (Orobanchaceae)

The holoparasitic angiosperm Orobanche minor parasitizes a diverse range of flowering plants from at least 16 orders in both the monocots and eudicots. However, populations of O. minor show host specificity at a local level. Our previous work identified the potential for host specificity to act as a catalyst for genetic divergence among populations of O. minor. Here we have extended this investigation by sampling populations from multiple hosts, across a broad geographic range. Sequence characterised amplified region (SCAR) data identified an exotic host-generalist lineage and a native host-specialist lineage of O. minor, suggesting genetic structure in this species is defined by both host specificity and geography. In addition, host-range overlap, discordant tree topologies, and cryptic morphology indicate the presence of gene flow between alien races and endemic populations. Therefore, repeated introductions of alien races of O. minor from disparate sources leading to introgression with native populations, and cryptic race formation, seem to have contributed to the taxonomic confusion associated with this species. We speculate that radiations associated with broad host range and divergent host ecologies may have promoted the unusually wide geographic distribution and diversification of this species. Finally, evidence of multiple shifts to exotic hosts, coupled with the predicted northward shift in climatic suitability, identify the potential for range expansion in alien races of O. minor, which may threaten nationally scarce native taxa with genetic assimilation. Our phylogenetic analysis provides a framework for identifying host races in Orobanche with a view to setting conservation priorities.     

A new species of Scolecobasidium associated with the sooty blotch and flyspeck complex on banana from China

Sooty blotch and flyspeck is caused by a complex of epiphytic fungi on diverse hosts. A fungus morphologically similar to Scolecobasidium humicola was isolated from a banana fruit exhibiting SBFS signs in Hainan, China. ITS and LSU sequences of rDNA corroborated that it was a Scolecobasidium species. The results of LSU rDNA analysis support the interpretation that Ochroconis is synonymous with Scolecobasidium. Five new combinations, S. anomalum, S. calidifluminale, S. gallopavum, S. gamsii, and S. lascauxense, were proposed. A new species, S. musae, was described based on morphological characteristics and sequence comparison with previous species.     

How Did Host Domestication Modify Life History Traits of Its Pathogens?

Understanding evolutionary dynamics of pathogens during domestication of their hosts and rise of agro-ecosystems is essential for durable disease management. Here, we investigated changes in life-history traits of the fungal pathogen Venturia inaequalis during domestication of the apple. Life traits linked to fungal dispersal were compared between 60 strains that were sampled in domestic and wild habitats in Kazakhstan, the center of origin of both host and pathogen. Our two main findings are that transition from wild to agro-ecosystems was associated with an increase of both spore size and sporulation capacity; and that distribution of quantitative traits of the domestic population mostly overlapped with those of the wild population. Our results suggest that apple domestication had a considerable impact on fungal characters linked to its dispersal through selection from standing phenotypic diversity. We showed that pestification of V. inaequalis in orchards led to an enhanced allocation in colonization ability from standing variation in the wild area. This study emphasizes the potential threat that pathogenic fungal populations living in wild environments represent for durability of resistance in agro-ecosystems.     

Sharing roosts but not ectoparasites: high host-specificity in bat flies and wing mites of Miniopterus schreibersii and Rhinolophus ferrumequinum (Mammalia: Chiroptera)

Schreiber’s bent-winged bat Miniopterus schreibersii and the greater horseshoe bat Rhinolophus ferrumequinum are widespread and common cavernicolous species across southern Europe that host numerous specialized ectoparasite species. The objective of this study was to characterize the species assemblage, genetic diversity, and host specificity of bat flies (Nycteribiidae, Diptera) and wing mites (Spinturnicidae, Acari) found on these bat hosts in Serbia and Bosnia and Herzegovina. Notably, while bat flies lay puparia on the cave walls and can thus be transmitted indirectly, wing mites require direct body contact for transmission. Morphological identification and sequencing of a 710-bp fragment of cytochrome oxidase I gene of 207 bat flies yielded 4 species, 3 on M. schreibersii and 1 on R. ferrumequinum. Sequencing of a 460-bp small subunit ribosomal RNA fragment, in all 190 collected wing mites revealed 2 species, 1 per host. In no case was a parasite associated with 1 host found on the other host. Species and genetic diversity of flies were higher in M. schreibersii, likely reflecting their host’s larger colony sizes and migratory potential. Mite species of both hosts showed similarly low diversity, likely due to their faster life history and lower winter survival. Our findings highlight a remarkably high host-specificity and segregation of ectoparasite species despite direct contact among their hosts in the roost, suggesting a defined host preference in the investigated ectoparasite species. Furthermore, the differences in ectoparasite genetic diversity exemplify the interplay between host and parasite life histories in shaping parasite population genetic structure.     

REPEAT SEQUENCE PRIMER‐PCR STUDY ON DNA POLYMORPHISM OF GEOGRAPHIC POPULATIONS OF COTTON APHID,APHIS GOSSYPII,IN CHINA*

Abstract The repeat sequence primer‐PCR technique was used to determine DNA polymorphism of the aphid Aphis gossypii (Glover) collected from 8 different localites in China. Three primers were selected and used for similarity index (SI) and cluster analysis based on the data of Nei's genetic distance (D). We found that the populations in the north and northwest of China was linked before they were joined by those in southern China. A proposed explanation emphasizes the populations in the north and northwest of China were located near — 4 °C isotherm or lower in January with less than 200 frost‐free days per year, whereas populations in southern China were located near 0 °C isotherm or higher with more than 300 frost ‐ free days per year. So it may be the over‐winter host plants instead of the geographic distance or gene flow, exert pronounced influence on the geographic population differentiation of A. gossypii. Species on different over‐winter host plants may directly lead to the genetic differentiation of their summer offsprings.     

Geographic analysis of host use, development, and habitat use of an acanthocephalan species, Leptorhynchoides thecatus

Leptorhynchoides thecatus (Linton, 1891), an acanthocephalan parasite of freshwater fishes, varies in host use, development, and habitat use throughout North America. Spatial structure of these characteristics was examined from data extracted from the literature. Geographic patterns were inferred from point comparisons using correllograms and then tested with Moran's I statistic for global and local significance, and visually from regional means within major river drainages. Species of Micropterus Lacepède, 1802 (black basses) were common hosts in most regions, except the Lower Mississippi and South Atlantic regions where species of Lepomis Rafinesque, 1819 (sunfishes) were common hosts. Development, described as the proportions of adults relative to cystacanths (extraintestinal juveniles), decreased with latitude. Habitat use of L. thecatus showed marked geographic patterns. Leptorhynchoides thecatus occurred in the intestine of sunfishes in the South Atlantic and Lower Mississippi regions, in the ceca in fish of all species included in the study in the Missouri and Texas-Gulf regions, and both in ceca and intestines in fish of all species in northern regions. Leptorhynchoides thecatus showed geographic patterning within the variable traits across the range of the species. These patterns may be the result of ecological factors or of genetic differences that might indicate L. thecatus comprises multiple cryptic species.     

Novel application of species richness estimators to predict the host range of parasites

Host range is a critical life history trait of parasites, influencing prevalence, virulence and ultimately determining their distributional extent. Current approaches to measure host range are sensitive to sampling effort, the number of known hosts increasing with more records. Here, we develop a novel application of results-based stopping rules to determine how many hosts should be sampled to yield stable estimates of the number of primary hosts within regions, then use species richness estimation to predict host ranges of parasites across their distributional ranges. We selected three mistletoe species (hemiparasitic plants in the Loranthaceae) to evaluate our approach: a strict host specialist (Amyema lucasii, dependent on a single host species), an intermediate species (Amyema quandang, dependent on hosts in one genus) and a generalist (Lysiana exocarpi, dependent on many genera across multiple families), comparing results from geographically-stratified surveys against known host lists derived from herbarium specimens. The results-based stopping rule (stop sampling bioregion once observed host richness exceeds 80% of the host richness predicted using the Abundance-based Coverage Estimator) worked well for most bioregions studied, being satisfied after three to six sampling plots (each representing 25 host trees) but was unreliable in those bioregions with high host richness or high proportions of rare hosts. Although generating stable predictions of host range with minimal variation among six estimators trialled, distribution-wide estimates fell well short of the number of hosts known from herbarium records. This mismatch, coupled with the discovery of nine previously unrecorded mistletoe-host combinations, further demonstrates the limited ecological relevance of simple host-parasite lists. By collecting estimates of host range of constrained completeness, our approach maximises sampling efficiency while generating comparable estimates of the number of primary hosts, with broad applicability to many host-parasite systems.     

On the origin and spread of the Scab disease of apple: out of central Asia

Background

Venturia inaequalis is an ascomycete fungus responsible for apple scab, a disease that has invaded almost all apple growing regions worldwide, with the corresponding adverse effects on apple production. Monitoring and predicting the effectiveness of intervention strategies require knowledge of the origin, introduction pathways, and population biology of pathogen populations. Analysis of the variation of genetic markers using the inferential framework of population genetics offers the potential to retrieve this information.

Methodology/Principal Findings

Here, we present a population genetic analysis of microsatellite variation in 1,273 strains of V. inaequalis representing 28 orchard samples from seven regions in five continents. Analysis of molecular variance revealed that most of the variation (88%) was distributed within localities, which is consistent with extensive historical migrations of the fungus among and within regions. Despite this shallow population structure, clustering analyses partitioned the data set into separate groups corresponding roughly to geography, indicating that each region hosts a distinct population of the fungus. Comparison of the levels of variability among populations, along with coalescent analyses of migration models and estimates of genetic distances, was consistent with a scenario in which the fungus emerged in Central Asia, where apple was domesticated, before its introduction into Europe and, more recently, into other continents with the expansion of apple growing. Across the novel range, levels of variability pointed to multiple introductions and all populations displayed signatures of significant post-introduction increases in population size. Most populations exhibited high genotypic diversity and random association of alleles across loci, indicating recombination both in native and introduced areas.

Conclusions/Significance

Venturia inaequalis is a model of invasive phytopathogenic fungus that has now reached the ultimate stage of the invasion process with a broad geographic distribution and well-established populations displaying high genetic variability, regular sexual reproduction, and demographic expansion.