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Host Specificity (host + specificity)
Selected AbstractsThe Beta-Binomial Model for Host Specificity among Organisms in Trophic InteractionsBIOMETRICS, Issue 3 2000Ola H. Diserud Summary. In this paper, we present a new stochastic model where the host specificity among organisms in trophic interactions in a community, say parasite-host interactions, is estimated by a beta-binomial model. The expected proportion of the host species in a community that a given parasite species is utilizing is modeled as a realization from an inhomogeneous Poisson process, where the rate of this process is assumed to be proportional to a beta probability distribution. The observed number of host species utilized by the parasites is then binomially distributed with the number of trials equaling the number of different host species in the sample. When the degree of polyphagy is estimated by the parameters of the beta-binomial model, quantities like community host specificity and the expected total number of parasite species that will utilize the host species in the community can be predicted as functions of the number of host species available. The predictions can then be applied in analysis of, e.g., symbiotic interactions among organisms, local species richness, and community structure. [source] Host specificity of ambrosia and bark beetles (Col., Curculionidae: Scolytinae and Platypodinae) in a New Guinea rainforestECOLOGICAL ENTOMOLOGY, Issue 6 2007JIRI HULCR Abstract 1.,Bark and ambrosia beetles are crucial for woody biomass decomposition in tropical forests worldwide. Despite that, quantitative data on their host specificity are scarce. 2.,Bark and ambrosia beetles (Scolytinae and Platypodinae) were reared from 13 species of tropical trees representing 11 families from all major lineages of dicotyledonous plants. Standardised samples of beetle-infested twigs, branches, trunks, and roots were taken from three individuals of each tree species growing in a lowland tropical rainforest in Papua New Guinea. 3.,A total of 81 742 beetles from 74 species were reared, 67 of them identified. Local species richness of bark and ambrosia beetles was estimated at 80,92 species. 4.,Ambrosia beetles were broad generalists as 95% of species did not show any preference for a particular host species or clade. Similarity of ambrosia beetle communities from different tree species was not correlated with phylogenetic distances between tree species. Similarity of ambrosia beetle communities from individual conspecific trees was not higher than that from heterospecific trees and different parts of the trees hosted similar ambrosia beetle communities, as only a few species preferred particular tree parts. 5.,In contrast, phloeophagous bark beetles showed strict specificity to host plant genus or family. However, this guild was poor in species (12 species) and restricted to only three plant families (Moraceae, Myristicaceae, Sapindaceae). 6.,Local diversity of both bark and ambrosia beetles is not driven by the local diversity of trees in tropical forests, since ambrosia beetles display no host specificity and bark beetles are species poor and restricted to a few plant families. [source] High host specificity of obligate ectoparasitesECOLOGICAL ENTOMOLOGY, Issue 5 2007CARL W. DICK Abstract 1.,Host specificity is the degree to which a parasite species occurs in association with a host species. 2.,The degree to which obligate ectoparasites are host specific has been debated, but effects of sampling contamination were usually not addressed. Data from a controlled mammal,ectoparasite survey were used to assess host specificity of an obligate group of ectoparasites , streblid bat flies. 3.,Host,parasite associations were categorised as primary or non-primary. Non-primary host associations were evaluated against primary associations via proportional comparison. 4.,Results indicate that host specificity was high, exceeding previous reports. Natural host transfers were rare. 5.,Non-primary host associations were almost completely explained by disturbance transfers during sampling of the host or by contamination upon sampling the parasite. These conclusions likely hold for other taxa of obligate parasites. [source] Novel insect-tree associations resulting from accidental and intentional biological ,invasions': a meta-analysis of effects on insect fitnessECOLOGY LETTERS, Issue 4 2010Coralie Bertheau Ecology Letters (2010) 13: 506,515 Abstract The translocation of species beyond their native range is a major threat to biodiversity. Invasions by tree-feeding insects attacking native trees and the colonization of introduced trees by native insects result in new insect,tree relationships. To date there is uncertainty about the key factors that influence the outcome of these novel interactions. We report the results of a meta-analysis of 346 pairwise comparisons of forest insect fitness on novel and ancient host tree species from 31 publications. Host specificity of insects and phylogenetic relatedness between ancient and novel host trees emerged as key factors influencing insect fitness. Overall, fitness was significantly lower on novel host species than on ancient hosts. However, in some cases, fitness increased on novel hosts, mainly in polyphagous insects or when close relatives of ancient host trees were colonized. Our synthesis enables greatly improved impact prediction and risk assessment of biological invasions. [source] SPECIFICITY AND SPECIALIZATION OF CONGENERIC MONOGENEANS PARASITIZING CYPRINID FISHEVOLUTION, Issue 5 2006Andrea, Imková Abstract Patterns and likely processes connected with evolution of host specificity in congeneric monogeneans parasitizing fish species of the Cyprinidae were investigated. A total of 51 Dactylogyrus species was included. We investigated (1) the link between host specificity and parasite phylogeny; (2) the morphometric correlates of host specificity, parasite body size, and variables of attachment organs important for host specificity; (3) the evolution of morphological adaptation, that is, attachment organ; (4) the determinants of host specificity following the hypothesis of specialization on more predictable resources considering maximal body size, maximal longevity, and abundance as measures of host predictability; and (5) the potential link between host specificity and parasite diversification. Host specificity, expressed as an index of host specificity including phylogenetic and taxonomic relatedness of hosts, was partially associated with parasite phylogeny, but no significant contribution of host phylogeny was found. The mapping of host specificity into the phylogenetic tree suggests that being specialist is not a derived condition for Dactylogyrus species. The different morphometric traits of the attachment apparatus seem to be selected in connection with specialization of specialist parasites and other traits favored as adaptations in generalist parasites. Parasites widespread on several host species reach higher abundance within hosts, which supports the hypothesis of ecological specialization. When separating specialists and generalists, we confirmed the hypothesis of specialization on a predictable resource; that is, specialists with larger anchors tend to live on fish species with larger body size and greater longevity, which could be also interpreted as a mechanism for optimizing morphological adaptation. We demonstrated that ecology of host species could also be recognized as an important determinant of host specificity. The mapping of morphological characters of the attachment organ onto the parasite phylogenetic tree reveals that morphological evolution of the attachment organ is connected with host specificity in the context of fish relatedness, especially at the level of host subfamilies. Finally, we did not find that host specificity leads to parasite diversification in congeneric monogeneans. [source] Use of Bacteriophages to Control Salmonella in Experimentally Contaminated Sprout SeedsJOURNAL OF FOOD SCIENCE, Issue 5 2004S. Pao ABSTRACT: Trials were conducted to evaluate the potential for using bacteriophages to control Salmonella in sprouting seeds. Two phages (Phage-A, capable of lysing S. Typhimurium and S. Enteritidis, and Phage-B, capable of lysing S. Montevideo) were isolated and characterized as members of the Myoviridae and Siphoviridae families, respectively. Salmonella counts increased in all inoculated seeds during soaking and mustard seeds supported greater growth of the inoculated Salmonella than broccoli seeds. A 1.37 log suppression of Salmonella growth was achieved by applying Phage-A on mustard seeds. The mixture of Phage-A and Phage-B caused a 1.50 log suppression of Salmonella growth in the soaking water of broccoli seeds. Host specificity observed in the study stresses the importance of developing phage mixtures that can control a broad range of potential contaminants. [source] Cryptic diversity and patterns of host specificity in trematode flatwormsMOLECULAR ECOLOGY, Issue 13 2010ALEXANDER HAYWARD The widespread utilization of molecular markers has revealed that a broad spectrum of taxa contain sets of morphologically cryptic, but genetically distinct lineages (Bickford et al. 2007). The identification of cryptic taxa is important as an accurate appreciation of diversity is crucial for a proper understanding of evolutionary and ecological processes. An example is the study of host specificity in parasitic taxa, where an apparent generalist may be found to contain a complex of several more specific species (Smith et al. 2006). Host specificity is a key life history trait that varies greatly among parasites (Poulin & Keeney 2007). While some can exploit a wide range of hosts, others are confined to just a single species. Access to additional hosts increases the resources available to a parasite. However, physiological or ecological constraints can restrict the extension of host range. Furthermore, there may be a trade-off between relaxed specificity and performance: generalism can decrease a parasites ability to adapt to each individual host species, and increase exposure to competition from other parasites (Poulin 1998). Despite the central role that host specificity plays in parasite life history, relatively little is known about how host range is determined in natural systems, and data from field studies are required to evaluate among competing ideas. In this issue, an exciting paper by Locke et al. (2010) makes a valuable contribution toward the understanding of host specificity in an important group of trematode flatworms. Using molecular methods, Locke et al. reveal an almost four-fold increase in the appreciated diversity of their focal group. In combination with a large and elegant sampling design this allows them to accurately assess host specificity for each taxon, and thus draw key insights into the factors that control host range in a dominant parasite group. [source] Host specificity, phenotype matching and the evolution of reproductive isolation in a coevolved plant,pollinator mutualismMOLECULAR ECOLOGY, Issue 24 2009ANNA G. HIMLER Coevolutionary interactions between plants and their associated pollinators and seed dispersers are thought to have promoted the diversification of flowering plants (Raven 1977; Regal 1977; Stebbins 1981). The actual mechanisms by which pollinators could drive species diversification in plants are not fully understood. However, it is thought that pollinator host specialization can influence the evolution of reproductive isolation among plant populations because the pollinator's choice of host is what determines patterns of gene flow in its host plant, and host choice may also have important consequences on pollinator and host fitness (Grant 1949; Bawa 1992). In this issue of Molecular Ecology, Smith et al. (2009) present a very interesting study that addresses how host specialization affects pollinator fitness and patterns of gene flow in a plant host. Several aspects of this study match elements of a seminal mathematical model of plant,pollinator codivergence (Kiester et al. 1984) suggesting that reciprocal selection for matched plant and pollinator reproductive traits may lead to speciation in the host and its pollinator when there is strong host specialization and a pattern of geographic subdivision. Smith et al.'s study represents an important step to fill the gap in our understanding of how reciprocal selection may lead to speciation in coevolved plant,pollinator mutualisms. [source] Host specificity and reproductive success of yucca moths (Tegeticula spp.MOLECULAR ECOLOGY, Issue 24 2009Lepidoptera: Prodoxidae) mirror patterns of gene flow between host plant varieties of the Joshua tree (Yucca brevifolia: Agavaceae) Abstract Coevolution between flowering plants and their pollinators is thought to have generated much of the diversity of life on Earth, but the population processes that may have produced these macroevolutionary patterns remain unclear. Mathematical models of coevolution in obligate pollination mutualisms suggest that phenotype matching between plants and their pollinators can generate reproductive isolation. Here, we test this hypothesis using a natural experiment that examines the role of natural selection on phenotype matching between yuccas and yucca moths (Tegeticula spp.) in mediating reproductive isolation between two varieties of Joshua tree (Yucca brevifolia var. brevifolia and Y. brevifolia var. jaegeriana). Using passive monitoring techniques, DNA barcoding, microsatellite DNA genotyping, and sibship reconstruction, we track host specificity and the fitness consequences of host choice in a zone of sympatry. We show that the two moth species differ in their degree of host specificity and that oviposition on a foreign host plant results in the production of fewer offspring. This difference in host specificity between the two moth species mirrors patterns of chloroplast introgression from west to east between host varieties, suggesting that natural selection acting on pollinator phenotypes mediates gene flow and reproductive isolation between Joshua-tree varieties. [source] Host specificity and incidence of Trypanosoma in some African rainforest birds: a molecular approachMOLECULAR ECOLOGY, Issue 9 2001Ravinder N. M. Sehgal Abstract Studies of host,parasite interactions in birds have contributed greatly to our understanding of the evolution and ecology of disease. Here we employ molecular techniques to determine the incidence and study the host-specificity of parasitic trypanosomes in the African avifauna. We developed a polymerase chain reaction (PCR)-based diagnostic test that amplified the small subunit ribosomal RNA gene (SSU rRNA) of Trypanosoma from avian blood samples. This nested PCR assay complements and corroborates information obtained by the traditional method of blood smear analysis. The test was used to describe the incidence of trypanosomes in 479 host individuals representing 71 rainforest bird species from Cameroon, the Ivory Coast and Equatorial Guinea. Forty-two (59%) of these potential host species harboured trypanosomes and 189 individuals (35%) were infected. To examine host and geographical specificity, we examined the morphology and sequenced a portion of the SSU rRNA gene from representative trypanosomes drawn from different hosts and collecting locations. In traditional blood smear analyses we identified two trypanosome morphospecies, T. avium and T. everetti. Our molecular and morphological results were congruent in that these two morphospecies had highly divergent SSU rRNA sequences, but the molecular assay also identified cryptic variation in T. avium, in which we found seven closely allied haplotypes. The pattern of sequence diversity within T. avium provides evidence for widespread trypanosome mixing across avian host taxa and across geographical locations. For example, T. avium lineages with identical haplotypes infected birds from different families, whereas single host species were infected by T. avium lineages with different haplotypes. Furthermore, some conspecific hosts from geographically distant sampling locations were infected with the same trypanosome lineage, but other individuals from those locations harboured different trypanosome lineages. This apparent lack of host or geographical specificity may have important consequences for the evolutionary and ecological interactions between parasitic trypanosomes and their avian hosts. [source] Host specificity and geographic range in haematophagous ectoparasitesOIKOS, Issue 3 2005Boris R. Krasnov A negative interspecific correlation between the degree of habitat specialization and the size of a species' geographic range has been documented for several free living groups of organisms, providing support for the niche breadth hypothesis. In contrast, practically nothing is known about the geographic range sizes of parasitic organisms and their determinants. In the context of the niche breadth hypothesis, parasites represent ideal study systems, because of the well documented variation in host specificity among parasite species. Here, we investigated the relationship between host specificity (a measure of niche breadth) and geographic range size among flea species parasitic on small mammals, using data from seven distinct geographical regions. Two measures of host specificity were used: the number of host species used by a flea species, and a measure of the average taxonomic distance between the host species used by a flea; the latter index provides an evolutionary perspective on host specificity. After correcting for phylogenetic influences, and using either of our two measures of host specificity, the degree of host specificity of fleas was negatively correlated with the size of their geographic range in all seven regions studied here, with only one minor exception. Overall, these results provide strong support for the niche breadth hypothesis, although other explanations cannot be ruled out. [source] Genetic Diversity of Parasitic Dinoflagellates in the Genus Amoebophrya and Its Relationship to Parasite Biology and BiogeographyTHE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 1 2008SUNJU KIM ABSTRACT. We determined 18S rRNA gene sequences of Amoebophrya strains infecting the thecate dinoflagellates Alexandrium affine and Gonyaulax polygramma from Korean coastal waters and compared those data with previously reported sequences of Amoebophrya from cultures, infected cells concentrated from field samples, and environmental 18S rRNA gene sequences obtained from a variety of marine environments. Further, we used these data to examine genetic diversity in Amoebophrya strains relative to geographic origin, host phylogeny, site of infection, and host specificity. In our analyses of known dinoflagellate taxa, the 13 available Amoebophrya sequences clustered together within the dinoflagellates as three groups forming a monophyletic group with high bootstrap support (maximum likelihood, ML: 100%) or a posterior probability (PP) of 1. When the Amoebophrya sequences were analyzed along with environmental sequences associated with Marine Alveolate Group II, nine subgroups formed a monophyletic group with high bootstrap support (ML: 100%) and PP of 1. Sequences known to be from Amoebophrya spp. infecting dinoflagellate hosts were distributed in seven of those subgroups. Despite differences in host species and geographic origin (Korea, United States, and Europe), Amoebophrya strains (Group II) from Gymnodinium instriatum, A. affine, Ceratium tripos (AY208892), Prorocentrum micans, and Ceratium lineatum grouped together by all of our tree construction methods, even after adding the environmental sequences. By contrast, strains within Groups I and III divided into several lineages following inclusion of environmental sequences. While Amoebophrya strains within Group II mostly developed within the host cytoplasm, strains in Groups I and III formed infections inside the host nucleus, a trait that appeared across several of the subgroups. Host specificity varied from moderately to extremely species-specific within groups, including Group II. Taken together, our results imply that genetic diversity in Amoebophrya strains does not always reflect parasite biology or biogeography. [source] Structure and vertical stratification of plant galler,parasitoid food webs in two tropical forestsECOLOGICAL ENTOMOLOGY, Issue 3 2009MIGUEL R. PANIAGUA Abstract 1.,Networks of feeding interactions among insect herbivores and natural enemies such as parasitoids, describe the structure of these assemblages and may be critically linked to their dynamics and stability. The present paper describes the first quantitative study of parasitoids associated with gall-inducing insect assemblages in the tropics, and the first investigation of vertical stratification in quantitative food web structure. 2.,Galls and associated parasitoids were sampled in the understorey and canopy of Parque Natural Metropolitano in the Pacific forest, and in the understorey of San Lorenzo Protected Area in the Caribbean forest of Panama. Quantitative host,parasitoid food webs were constructed for each assemblage, including 34 gall maker species, 28 host plants, and 57 parasitoid species. 3.,Species richness was higher in the understorey for parasitoids, but higher in the canopy for gall makers. There was an almost complete turnover in gall maker and parasitoid assemblage composition between strata, and the few parasitoid species shared between strata were associated with the same host species. 4.,Most parasitoid species were host specific, and the few polyphagous parasitoid species were restricted to the understorey. 5.,These results suggest that, in contrast to better-studied leaf miner,parasitoid assemblages, the influence of apparent competition mediated by shared parasitoids as a structuring factor is likely to be minimal in the understorey and practically absent in the canopy, increasing the potential for coexistence of parasitoid species. 6.,High parasitoid beta diversity and high host specificity, particularly in the poorly studied canopy, indicate that tropical forests may be even more species rich in hymenopteran parasitoids than previously suspected. [source] Host specificity of ambrosia and bark beetles (Col., Curculionidae: Scolytinae and Platypodinae) in a New Guinea rainforestECOLOGICAL ENTOMOLOGY, Issue 6 2007JIRI HULCR Abstract 1.,Bark and ambrosia beetles are crucial for woody biomass decomposition in tropical forests worldwide. Despite that, quantitative data on their host specificity are scarce. 2.,Bark and ambrosia beetles (Scolytinae and Platypodinae) were reared from 13 species of tropical trees representing 11 families from all major lineages of dicotyledonous plants. Standardised samples of beetle-infested twigs, branches, trunks, and roots were taken from three individuals of each tree species growing in a lowland tropical rainforest in Papua New Guinea. 3.,A total of 81 742 beetles from 74 species were reared, 67 of them identified. Local species richness of bark and ambrosia beetles was estimated at 80,92 species. 4.,Ambrosia beetles were broad generalists as 95% of species did not show any preference for a particular host species or clade. Similarity of ambrosia beetle communities from different tree species was not correlated with phylogenetic distances between tree species. Similarity of ambrosia beetle communities from individual conspecific trees was not higher than that from heterospecific trees and different parts of the trees hosted similar ambrosia beetle communities, as only a few species preferred particular tree parts. 5.,In contrast, phloeophagous bark beetles showed strict specificity to host plant genus or family. However, this guild was poor in species (12 species) and restricted to only three plant families (Moraceae, Myristicaceae, Sapindaceae). 6.,Local diversity of both bark and ambrosia beetles is not driven by the local diversity of trees in tropical forests, since ambrosia beetles display no host specificity and bark beetles are species poor and restricted to a few plant families. [source] High host specificity of obligate ectoparasitesECOLOGICAL ENTOMOLOGY, Issue 5 2007CARL W. DICK Abstract 1.,Host specificity is the degree to which a parasite species occurs in association with a host species. 2.,The degree to which obligate ectoparasites are host specific has been debated, but effects of sampling contamination were usually not addressed. Data from a controlled mammal,ectoparasite survey were used to assess host specificity of an obligate group of ectoparasites , streblid bat flies. 3.,Host,parasite associations were categorised as primary or non-primary. Non-primary host associations were evaluated against primary associations via proportional comparison. 4.,Results indicate that host specificity was high, exceeding previous reports. Natural host transfers were rare. 5.,Non-primary host associations were almost completely explained by disturbance transfers during sampling of the host or by contamination upon sampling the parasite. These conclusions likely hold for other taxa of obligate parasites. [source] Community structure of arboreal caterpillars within and among four tree species of the eastern deciduous forestECOLOGICAL ENTOMOLOGY, Issue 6 2003Keith S. Summerville Abstract., 1.,A seasonally replicated experimental design was used to address the question of how differences within and among host tree species affect arboreal caterpillar communities. 2.,Seasonal variation influenced caterpillar community composition most significantly, and the similarity among caterpillar assemblages did not necessarily follow the pattern of phylogenetic relatedness among host trees. 3.,Species richness and abundance of caterpillars were higher on oaks and maples than on American beech. Diversity partitioning models revealed that , diversity was only occasionally greater or less than expected by chance alone. 4.,When , diversity was significant, values tended to be greater than expected by chance among replicate trees within each species and lower than expected by chance among the four tree species. 5.,Differences among trees appeared important for determining patterns of species presence/absence for rare species and influencing patterns of species dominance within caterpillar assemblages. Differences among tree species had a significant effect on overall lepidopteran community composition and mean species diversity (i.e. , diversity). 6.,Because , diversity of caterpillars among host trees was lower than expected by chance, host specificity within the Lepidoptera may be less prevalent than thought previously. [source] A novel host shift and invaded range of a seed predator, Acanthoscelides macrophthalmus (Coleoptera: Chrysomelidae: Bruchinae), of an invasive weed, Leucaena leucocephalaENTOMOLOGICAL SCIENCE, Issue 1 2009Midori TUDA Abstract An endophagous seed predator, Acanthoscelides macrophthalmus (Coleoptera: Chrysomelidae: Bruchinae), utilizes Neotropical Leucaena (Fabaceae: Mimosoideae). One of its hosts, Leucaena leucocephala, is a fast-growing nitrogen-fixing tree that serves as a multipurpose beneficial plant but eventually becomes an aggressive invader where it was introduced. Herein, we report A. macrophthalmus invasion of the Far East, South Asian tropics and subtropics (Japanese Pacific Islands, Taiwan, Southern China, Northern Thailand and Southern India). Of other field-collected mimosoid legumes, an introduced tree, Falcataria moluccana, in Taiwan was found to be used by the seed predator. Conversely, our published work review revealed that the seed predator had retained high host specificity to Leucaena species in its native and introduced regions. Acanthoscelides macrophthalmus was able to utilize aphagously postharvest mature seeds for oviposition and larval development, which is a trait of post-dispersal seed predators. We confirmed that A. macrophthalmus that was reared on L. leucocephala was able to utilize F. moluccana as well. Although the relatively high host specificity of the oligophagous beetle is suitable for controlling the weedy L. leucocephala, the potential host range expansion confirmed by this study must be cautioned. [source] Life history and host specificity of the Japanese flea beetles Trachyaphthona sordida and T. nigrita (Coleoptera: Chrysomelidae), potential biological control agents against skunk vine, Paederia foetida (Rubiaceae), in the southeastern parts of the United States and HawaiiENTOMOLOGICAL SCIENCE, Issue 2 2008Chie OKAMOTO Abstract Skunk vine, Paederia foetida (Rubiaceae), is native to Asia and has been recognized as an invasive weedy vine of natural areas in Florida and Hawaii. Two insects, Trachyaphthona sordida and Trachyaphthona nigrita (Coleoptera: Chrysomelidae) from Japan are being considered as potential biological control agents against skunk vine. To gather fundamental information on their biology, we carried out field surveys and laboratory experiments in Kyushu, southern Japan, between 2003 and 2006. We found that T. sordida is commonly distributed in Kyushu and T. nigrita is restricted to the southern parts of Kagoshima Prefecture on the southern part of Kyushu. These species are fundamentally univoltine and adults appear in late April to early July. Trachyaphthona sordida overwinters as mature larvae and T. nigrita as mature larvae or rarely as adults. Larvae of both species feed on fine roots of P. foetida in the field and Serissa foetida (Rubiaceae) under rearing conditions, and they appear to have tribe-level host specificity in their host range. On the basis of these results, we suggest that both species are suitable as biological control agents. [source] SPECIFICITY AND SPECIALIZATION OF CONGENERIC MONOGENEANS PARASITIZING CYPRINID FISHEVOLUTION, Issue 5 2006Andrea, Imková Abstract Patterns and likely processes connected with evolution of host specificity in congeneric monogeneans parasitizing fish species of the Cyprinidae were investigated. A total of 51 Dactylogyrus species was included. We investigated (1) the link between host specificity and parasite phylogeny; (2) the morphometric correlates of host specificity, parasite body size, and variables of attachment organs important for host specificity; (3) the evolution of morphological adaptation, that is, attachment organ; (4) the determinants of host specificity following the hypothesis of specialization on more predictable resources considering maximal body size, maximal longevity, and abundance as measures of host predictability; and (5) the potential link between host specificity and parasite diversification. Host specificity, expressed as an index of host specificity including phylogenetic and taxonomic relatedness of hosts, was partially associated with parasite phylogeny, but no significant contribution of host phylogeny was found. The mapping of host specificity into the phylogenetic tree suggests that being specialist is not a derived condition for Dactylogyrus species. The different morphometric traits of the attachment apparatus seem to be selected in connection with specialization of specialist parasites and other traits favored as adaptations in generalist parasites. Parasites widespread on several host species reach higher abundance within hosts, which supports the hypothesis of ecological specialization. When separating specialists and generalists, we confirmed the hypothesis of specialization on a predictable resource; that is, specialists with larger anchors tend to live on fish species with larger body size and greater longevity, which could be also interpreted as a mechanism for optimizing morphological adaptation. We demonstrated that ecology of host species could also be recognized as an important determinant of host specificity. The mapping of morphological characters of the attachment organ onto the parasite phylogenetic tree reveals that morphological evolution of the attachment organ is connected with host specificity in the context of fish relatedness, especially at the level of host subfamilies. Finally, we did not find that host specificity leads to parasite diversification in congeneric monogeneans. [source] LINKING COEVOLUTIONARY HISTORY TO ECOLOGICAL PROCESS: DOVES AND LICEEVOLUTION, Issue 10 2003Dale H. Clayton Abstract Many host-specific parasites are restricted to a limited range of host species by ecological barriers that impede dispersal and successful establishment. In some cases, microevolutionary differentiation is apparent on top of host specificity, as evidenced by significant parasite population genetic structure among host populations. Ecological barriers responsible for specificity and genetic structure can, in principle, reinforce macroevolutionary processes that generate congruent host-parasite phylogenies. However, few studies have explored both the micro- and macroevolutionary ramifications of close association in a single host-parasite system. Here we compare the macroevolutionary histories of two genera of feather lice (Phthiraptera: Ischnocera) that both parasitize New World pigeons and doves (Aves: Columbiformes). Earlier work has shown that dove body lice (genus Physconelloides) are more host specific and have greater population genetic structure than dove wing lice (Columbicola). We reconstructed phylogenies for representatives of the two genera of lice and their hosts, using nuclear and mitochondrial DNA sequences. The phylogenies were well resolved and generally well supported. We compared the phylogenies of body lice and wing lice to the host phylogeny using reconciliation analyses. We found that dove body lice show strong evidence of cospeciation whereas dove wing lice do not. Although the ecology of body and wing lice is very similar, differences in their dispersal ability may underlie these joint differences in host specificity, population genetic structure, and coevolutionary history. [source] Effects of parasite specificity and previous infestation of hosts on the feeding and reproductive success of rodent-infesting fleasFUNCTIONAL ECOLOGY, Issue 3 2008I. S. Khokhlova Summary 1We examined whether identity of the rodent host and previous infestation of the host affect feeding and reproduction of fleas. We predicted that feeding and reproductive success of fleas would be higher when feeding on (i) a typical host than on an atypical host; and (ii) a pristine host than on a host previously exposed to parasitism. We also predicted that the negative effect of previous infestation would not be manifested in a host-specific flea feeding on its typical host. 2To test these predictions, we measured blood meal size, egg production and latency of oviposition in host-specific Parapulex chephrenis and host-opportunistic Xenopsylla ramesis during seven daily feedings on the Egyptian spiny mouse Acomys cahirinus (typical host of the former) and Wagner's gerbil Dipodillus dasyurus (typical host of the latter). 3Blood meal size in P. chephrenis did not depend on either host species or previous host infestation with fleas. However, when this flea fed on D. dasyurus as opposed to A. cahirinus, blood meal size increased to the end of 7-day period. Xenopsylla ramesis took larger blood meals (i) during the first feeding; (ii) from D. dasyurus than from A. cahirinus; and (iii) from pristine than from previously infested D. dasyurus, but the blood meals taken from pristine and previously infested A. cahirinus were similar. 4Egg production of P. chephrenis was significantly higher and oviposition started earlier when it fed on A. cahirinus; this was true for X. ramesis when it fed on D. dasyurus. Surprisingly, P. chephrenis laid more eggs and started oviposition earlier when it fed on previously infested rodents. However, egg production in X. ramesis and start of oviposition were similar in pristine and previously infested hosts. 5These results suggest that the response of a parasite to acquired immunity of a host may depend on the host species, level of parasite host specificity as well as the degree of ,tightness' of a particular parasite,host association. [source] Beta diversity of plant,insect food webs in tropical forests: a conceptual frameworkINSECT CONSERVATION AND DIVERSITY, Issue 1 2009VOJTECH NOVOTNY Abstract., 1Beta diversity of plant,herbivore food webs, defined as turnover of trophic interactions between the food webs, represents a potentially useful extension of traditional studies of plant and herbivore beta diversity as it integrates spatial turnover of plant and herbivore species with changes in herbivore host plant preferences. 2Beta diversity of plant,herbivore food webs can be partitioned into four components, corresponding to the turnover of plant,herbivore interactions due to change in (i) both plant and herbivore species, (ii) plant, but not herbivore, species, (iii) herbivore, but not plant, species, and (iv) herbivore host preferences between food webs. These components can be quantified using a range of existing beta diversity indices. 3Relative magnitude of plant and herbivore beta diversity of plant,herbivore food webs can be analysed as an outcome of herbivore (i) host specificity, (ii) ability to track host plant populations by dispersal, and (iii) response to environmental conditions, competitors and enemies. The relative importance of these factors in tropical ecosystems remains to be determined. [source] Characterization of HCF-1, a determinant of Autographa californica multiple nucleopolyhedrovirus host specificityINSECT MOLECULAR BIOLOGY, Issue 6 2003K. L. Hefferon Abstract Autographa californica multiple nucleopolyhedrovirus (AcMNPV) infects a wide variety of insect species. A number of AcMNPV late expression factors that are involved in replication have been identified as playing a role in determining host specificity. Host cell factor-1, or HCF-1, was previously demonstrated to be essential for viral replication in Tn -368 cells. Here we demonstrate that HCF-1 is an early protein and localizes to the cell nucleus. Coprecipitation experiments revealed that HCF-1 interacts with itself but none of the other late expression factors required for replication in Tn -368 cells. HCF-1 mutants were constructed and utilized to search for the domains involved in HCF-1 biological function and oligomerization. Possible roles of HCF-1 in determining host specificity are discussed. [source] Spanning the gap: experimental determination of paratenic host specificity of horsehair worms (Nematomorpha: Gordiida)INVERTEBRATE BIOLOGY, Issue 1 2003Ben Hanelt Abstract. Details of the life cycle of freshwater nematomorphs (gordiids) remain unclear. Free-living aquatic larval gordiids must make a critical transition from an epibenthic aquatic environment to terrestrial hosts. In order to identify potential hosts capable of bridging this ecological gap, the specificity of paratenic hosts of three common species of North American gordiids was investigated. All three species were characterized by an identical infection pattern: low host specificity. Gordiids were able to encyst within annelids, mollusks, crustaceans, insects and a vertebrate. Three species of putative host (a turbellarian, a water mite, and a mosquito larva) were not infected with any of the gordiid species. Internal defense reactions (IDR) and feeding behaviors are implicated as preventing infection in these species. Several of the other host species produced either an IDR or an immune reaction to the cysts, although reactions to the cysts were highly variable between species. In most species, IDR did not cause noticeable harm to the encysted larvae. It is proposed that although many species are easily infected with gordiid cysts, most do not act as natural paratenic hosts. For some of these host groups, especially snails, a role as reservoir host is suggested. Of all hosts included in this study, aquatic insects were identified as the hosts likely responsible for spanning the ecological gap and acting as true hosts for gordiids. [source] Do threatened hosts have fewer parasites?JOURNAL OF ANIMAL ECOLOGY, Issue 2 2007A comparative study in primates Summary 1Parasites and infectious diseases have become a major concern in conservation biology, in part because they can trigger or accelerate species or population declines. Focusing on primates as a well-studied host clade, we tested whether the species richness and prevalence of parasites differed between threatened and non-threatened host species. 2We collated data on 386 species of parasites (including viruses, bacteria, protozoa, helminths and arthropods) reported to infect wild populations of 36 threatened and 81 non-threatened primate species. Analyses controlled for uneven sampling effort and host phylogeny. 3Results showed that total parasite species richness was lower among threatened primates, supporting the prediction that small, isolated host populations harbour fewer parasite species. This trend was consistent across three major parasite groups found in primates (helminths, protozoa and viruses). Counter to our predictions, patterns of parasite species richness were independent of parasite transmission mode and the degree of host specificity. 4We also examined the prevalence of selected parasite genera among primate sister-taxa that differed in their ranked threat categories, but found no significant differences in prevalence between threatened and non-threatened hosts. 5This study is the first to demonstrate differences in parasite richness relative to host threat status. Results indicate that human activities and host characteristics that increase the extinction risk of wild animal species may lead simultaneously to the loss of parasites. Lower average parasite richness in threatened host taxa also points to the need for a better understanding of the cascading effects of host biodiversity loss for affiliated parasite species. [source] Biology and host specificity of Aulacobaris fallax (Coleoptera: Curculionidae), a potential biological control agent for dyer's woad, Isatis tinctoria (Brassicaceae) in North AmericaJOURNAL OF APPLIED ENTOMOLOGY, Issue 5 2009E. Gerber Abstract Dyer's woad, Isatis tinctoria, a plant of Eurasian origin is a problematic weed in western North America against which a classical biological weed control programme was initiated in 2004. Three European insect species were selected as candidate agents to control this invasive species, including the root-mining weevil Aulacobaris fallax. To determine its suitability as an agent, the biology and host specificity of A. fallax were studied in outdoor plots and in the field between 2004 and 2006 in its native European range. Aulacobaris fallax is a univoltine species that lays its eggs from March to August into leaf stalks and roots of dyer's woad. Larvae mine and pupate in the roots and adults emerge from August to October. Up to 62% of the dyer's woad plants at the field sites investigated were attacked by this weevil. In no-choice host-specificity tests, A. fallax attacked 16 out of 39 species and varieties within the Family Brassicaceae. Twelve of these are native to North America. In subsequent multiple-choice tests, seven species, all native to North America, suffered a similar level of attack as dyer's woad, while none of the European species were attacked. Our results demonstrate the importance of including test plant species that have not co-evolved with the respective candidate agent. In sum, we conclude that the risk of non-target effects is too high for A. fallax to be considered as a biological control agent for dyer's woad in the United States. [source] Maximized virulence in a sterilizing pathogen: the anther-smut fungus and its co-evolved hostsJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 6 2008D. B. SLOAN Abstract Host sterilization is a common feature of sexually transmitted diseases (STDs). Because host reproductive failure may free up resources for pathogen reproduction and transmission, theory predicts that selection on sterilizing pathogens will favour maximum virulence (i.e. complete sterilization). We examined patterns of infection in sexually transmitted anther-smut fungi (Microbotryum) on four of their host species in the Caryophyllaceae. Using controlled fungal matings and experimental inoculations, we compared disease expression in inoculations ranging from host-specific pathogens to hybrids and cross-species treatments. Our data support the existence of host-specific sibling species within the genus Microbotryum based on a low infection rate from cross-inoculations and reduced fitness for hybrid pathogens. These patterns of host specificity and reproductive isolation, however, were not absolute. We did observe some successful cross-species and hybrid infections, but the expression of disease was frequently incomplete, including only partial host sterilization and the failed dehiscence of pathogen spores. The prevalence of these maladapted disease phenotypes may greatly inhibit the emergence of novel host pathogen combinations. Infections by hybrid pathogen genotypes were intermediate, in terms of both infection rate and the normality of disease symptoms, between host-specific and cross-inoculated pathogens. In addition, the frequency with which hybrid and cross-inoculated anther-smut pathogens were able to infect but not sterilize new hosts supports the prediction that sterilizing STDs are under selection to maximize virulence in natural populations. [source] Genetic architecture for normal and novel host-plant use in two local populations of the herbivorous ladybird beetle, Epilachna pustulosaJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 5 2003H. Ueno Abstract Trade-offs in host-plant use are thought to promote the evolution of host specificity. However, usually either positive or no genetic correlations have been found. Whereas factors enhancing variation in overall viability have been claimed to mask negative genetic correlations, alternative hypotheses emphasize the sequential changes in genetic correlation in the course of host-range evolution. In this study, the genetic architectures of performances on different hosts were compared in two populations of the herbivorous ladybird beetle, Epilachna pustulosa, using three host plants, one being normal for both, one novel for only one population, and the other novel for both populations. The genetic correlations between larval periods on normal hosts were significantly positive whereas those between normal and novel hosts were not different from zero. There was no evidence for reduced genetic variation on the normal host-plants. These results suggest that the host-range is not restricted by the antagonistic genetic associations among exploitation abilities on different plant species, but rather that selection of different host-plants may improve the coordination between genes responsible for the use of different plants. [source] Iridovirus infections in finfish , critical review with emphasis on ranavirusesJOURNAL OF FISH DISEASES, Issue 2 2010R J Whittington Abstract Viruses in three genera of the family Iridoviridae (iridoviruses) affect finfish. Ranaviruses and megalocytiviruses are recently emerged pathogens. Both cause severe systemic disease, occur globally and affect a diversity of hosts. In contrast, lymphocystiviruses cause superficial lesions and rarely cause economic loss. The ranavirus epizootic haematopoietic necrosis virus (EHNV) from Australia was the first iridovirus to cause epizootic mortality in finfish. Like other ranaviruses, it lacks host specificity. A distinct but closely related virus, European catfish virus, occurs in finfish in Europe, while very similar ranaviruses occur in amphibians in Europe, Asia, Australia, North America and South America. These viruses can be distinguished from one another by conserved differences in the sequence of the major capsid protein gene, which informs policies of the World Organisation for Animal Health to minimize transboundary spread of these agents. However, limited epidemiological information and variations in disease expression create difficulties for design of sampling strategies for surveillance. There is still uncertainty surrounding the taxonomy of some putative ranaviruses such as Singapore grouper iridovirus and Santee-Cooper ranavirus, both of which cause serious disease in fish, and confusion continues with diseases caused by megalocytiviruses. In this review, aspects of the agents and diseases caused by ranaviruses are contrasted with those due to megalocytiviruses to promote accurate diagnosis and characterization of the agents responsible. Ranavirus epizootics in amphibians are also discussed because of possible links with finfish and common anthropogenic mechanisms of spread. The source of the global epizootic of disease caused by systemic iridoviruses in finfish and amphibians is uncertain, but three possibilities are discussed: trade in food fish, trade in ornamental fish, reptiles and amphibians and emergence from unknown reservoir hosts associated with environmental change. [source] Isolation and Characterization of Lactobacillus Species Having Potential for Use as Probiotic Cultures for DogsJOURNAL OF FOOD SCIENCE, Issue 3 2007S. McCoy ABSTRACT:, The need to control pathogenic microorganisms in the intestinal tract of dogs is a growing concern. There is interest in using probiotics such as species of Lactobacillus to help control canine intestinal infections. For successful use as a probiotic, the bacterial species should be of canine intestinal origin since these species exhibit host specificity. Serial dilutions of freshly voided dog feces were plated on Lactobacillus selection (LBS) agar to isolate the cultures. Isolates were identified based on Gram stain, catalase test, and fermentation patterns using API 50 CH kits. All potential isolates were compared for bile resistance based on relative ability to grow in broth containing 0.3% Oxgall, the ability to inhibit Salmonella Typhimurium in associative broth cultures, and the production of reuterin. Of the lactobacilli isolated, Lactobacillus reuteri was the dominant species. However, some cultures of L. acidophilus also were isolated. We found variations among the isolates of L. reuteri and L. acidophilus with respect to bile tolerance. In general, isolates of L. reuteri appeared to be more bile resistant than were isolates of L. acidophilus. There were also variations in the ability to inhibit growth of S. Typhimurium. Some isolates of L. reuteri produced reuterin while others did not. [source] | ||||||||||||||||||||||||||||||||||