Patterns Of Host Association Research Articles

Global macroecological patterns in host plant associations of Cryptocephalinae case-bearer leaf beetles (Coleoptera: Chrysomelidae)

Abstract The aim of our work is to catalogue host plant records of the leaf beetle subfamily Cryptocephalinae at the global scale and use it as the foundation to analyse host plant relationships, one proposed key driver in the evolution of phytophagan hyperdiversity. We describe macro-scale host association patterns and assess the trophic range of Cryptocephalinae at the generic level. We assembled 532 sources and extracted 14 253 host plant records (1894 species of plants) for 1436 species of Cryptocephalinae. The results revealed that most genera of Cryptocephalinae are either polyphagous or strongly polyphagous, yet the five tribes exhibit intrinsic patterns of host association. Clear macroecological constraints exist for Cryptocephalinae within major lineages of plants. Polyphagy is also maintained for most of the documented juvenile stages and the 19 genera with myrmecophilous species. The most common host plants for Cryptocephalinae are eudicots, especially among the rosids the order Fabales has the most records, and Asterales, Fagales, Malpighiales, Myrtales, Rosales, and Sapindales are common hosts within all Cryptocephalinae tribes. Our meta-analysis approach and assessing the quality of host plant records permit detection of patterns in host association at the global scale and allows detection of all levels of plant–beetle interactions, from unlikely hosts to potential or real feeders. Our criteria for assessing host plant records and our working model can be applied to other chrysomelid subfamilies and phytophagous insects. The analysis of macroecological patterns and host checklist provide a basis for generic revisions and hypothesis construction in future ecological, molecular, and morphological studies.

Assessing the diversity of freshwater fish trematodes from Laguna Escondida, Los Tuxtlas tropical rainforest, Mexico, using morphology and 28S rDNA sequences as barcodes.

Despite a great effort made for almost 90 years, the diversity of freshwater fish trematodes in Mexico is still far from being fully known. The addition of molecular data to the description of trematode diversity in the last two decades added the potential to establish more robust species limits and a more accurate biodiversity estimation, but also led in some instances to the recognition of cryptic species complexes. Here, we used sequences of the large subunit of the nuclear ribosomal gene (28S rRNA) as barcodes, and morphological data, to assess the diversity of freshwater fish trematodes from a lake within a tropical rainforest. Eighty freshwater fish specimens of eight species were studied, and 120 trematode specimens were collected. Morphologically, specimens were allocated into nine genera; molecular phylogenetic analyses along with sequence divergence data provided evidence for recognising 11 trematode taxa, six adults and five metacercariae; six of them were identified to species level. Geographical distribution and host association patterns are briefly discussed for each trematode taxa.

Population genetic analyses reveal host association and genetically distinct populations of social parasite Solenopsis daguerrei (Hymenoptera: Formicidae)

Inquiline ant social parasites exploit other ant species for their reproductive benefit because they do not possess a worker caste. Due to their relative rarity in nature, the biology and natural history of inquilines are largely unknown. Likewise, not much research exists that details the close relationship between inquilines and their host(s), and how each organism influences the genetic structure of the other. Here, we conducted a comparative population genetics study to assess patterns of genetic structure within and among populations of inquiline Solenopsis daguerrei and its known fire ant hosts, which includes invasive Solenopsis invicta. Using nuclear and mitochondrial markers, we show that four genetically distinct groups of S. daguerrei likely exist, each with different degrees of host association. Consistent with previous inferences of the inquiline lifestyle, we find that inbreeding is common in S. daguerrei, presumably a result of intranidal mating and restricted dispersal. Results from this study, specifically host association patterns, may inform future biological control strategies to mitigate invasive S. invicta populations.

Environmental factors driving the abundance of Philaenus spumarius in mesomediterranean habitats of Corsica (France)

Philaenus spumarius (Ps) is considered the main insect vector of the bacterium Xylella fastidiosa (Xf) in Europe. As such, it is a key actor of the Xf pathosystem on which surveillance and management strategies could be implemented. Although research effort has increased in the past years, the ecological factors shaping Ps abundance and distribution across landscapes are still poorly known in most regions of Europe. We selected 64 plots of 500m2 in Corsican semi-natural habitats in which we sampled nymphs and adults of Ps during three years. While local or surrounding vegetation structure (low or high scrubland) had little effect on Ps abundance, we highlighted a positive relationship between Ps abundance and the density of Cistus monspeliensis in the plots. We also found larger populations of Ps in cooler and moister plots. The pattern of host association highlighted here is unique, which calls for more studies on the ecology of Ps in Europe, to help designing surveillance and management strategy for Xf.

Species richness of bat flies and their associations with host bats in a subtropical East Asian region

BackgroundUnderstanding the interactions between bat flies and host bats offer us fundamental insights into the coevolutionary and ecological processes in host-parasite relationships. Here, we investigated the identities, host specificity, and patterns of host association of bat flies in a subtropical region in East Asia, which is an understudied region for bat fly research.MethodsWe used both morphological characteristics and DNA barcoding to identify the bat fly species found on 11 cavernicolous bat species from five bat families inhabiting Hong Kong. We first determined the phylogenetic relationships among bat fly species. Then, we elucidated the patterns of bat-bat fly associations and calculated the host specificity of each bat fly species. Furthermore, we assembled the mitogenomes of three bat fly species from two families (Nycteribiidae and Streblidae) to contribute to the limited bat fly genetic resources available.ResultsWe examined 641 individuals of bat flies and found 20 species, of which many appeared to be new to science. Species of Nycteribiidae included five Nycteribia spp., three Penicillidia spp., two Phthiridium spp., one Basilia sp., and one species from a hitherto unknown genus, whereas Streblidae included Brachytarsina amboinensis, three Raymondia spp., and four additional Brachytarsina spp. Our bat-bat fly association network shows that certain closely related bat flies within Nycteribiidae and Streblidae only parasitized host bat species that are phylogenetically more closely related. For example, congenerics of Raymondia only parasitized hosts in Rhinolophus and Hipposideros, which are in two closely related families in Rhinolophoidea, but not other distantly related co-roosting species. A wide spectrum of host specificity of these bat fly species was also revealed, with some bat fly species being strictly monoxenous, e.g. nycteribiid Nycteribia sp. A, Phthiridium sp. A, and streblid Raymondia sp. A, while streblid B. amboinensis is polyxenous.ConclusionsThe bat fly diversity and specificity uncovered in this study have shed light on the complex bat-bat fly ecology in the region, but more bat-parasite association studies are still needed in East Asian regions like China as a huge number of unknown species likely exists. We highly recommend the use of DNA barcoding to support morphological identification to reveal accurate host-ectoparasite relationships for future studies.Graphical

Population Diversity and Genetic Structure Reveal Patterns of Host Association and Anthropogenic Impact for the Globally Important Fungal Tree Pathogen Ceratocystis manginecans.

Species in the Ceratocystis manginecans complex are important fungal pathogens of plantation trees globally. The most important hosts include species of Eucalyptus, Acacia, Mangifera, and Punica. Despite their relevance and widespread occurrence, little is known regarding their population genetics and how this might relate to their host associations or geographic regions in which they occur. A global collection of 491 isolates representing the C. manginecans complex, from four different plant hosts and nine countries, were genotyped using microsatellite markers. Population genetic analyses using numerous tools were conducted to interrogate how their genetic diversity and structure might be affected by host or areas of occurrence. Results of genetic diversity studies showed that when grouping isolates into populations based on their host associations, the population on Eucalyptus was most diverse, and it also has a broad global distribution. When considering countries of origin as a basis for defining populations, the gene and genotypic diversity were highest in populations from China, Indonesia, and Brazil. In contrast, populations from Oman and Pakistan collected from Mangifera had the lowest genetic diversity and were clonal. Molecular variance, population differentiation, and network and structure analyses showed that the genetic structure of isolates in the C. manginecans complex is influenced by both host association as well as geographical isolation. Furthermore, the results reflected the movement of genotypes between plant hosts and geographic regions that have implications regarding the broad global distribution of this pathogen.

Ixodes scapularis (Acari: Ixodidae) Nymphal Survival and Host-Finding Success in the Eastern United States.

The blacklegged tick (Ixodes scapularis Say) is the primary vector of Borrelia burgdorferi sensu stricto (Spirochaetales: Spirochaetaceae), the Lyme disease agent in North America. The basic reproduction number (R0) for B. burgdorferi in I. scapularis in the Northeast is highly sensitive to the probability that engorged larvae survive the winter, molt into nymphs, and find a host. These processes are dependent on local environmental variables, including climate, host population size and movement, and tick behavior. A simple model is presented for estimating host-finding success from the ratio of tick abundance in two subsequent years, accounting for overwinter survival and possible differences in host associations between nymphs and larvae. This model was parameterized using data from two sites in mainland Connecticut and two on Block Island, RI. Host abundance and tick burdens were estimated via mark-recapture trapping of the primary host, Peromyscus leucopus Rafinesque. Overwintering survival was estimated using engorged larvae placed in field enclosures at each site. Only nymphs were recovered alive, and no significant differences in model parameters were observed between Connecticut and Block Island. Host-finding success was predicted to be high across a wide range of host association patterns at three of four sites. Assuming equivalent host association between larvae and nymphs, R0 was also estimated to be greater than one at three of four sites, suggesting these conditions allow for the persistence of B. burgdorferi. The model output was highly sensitive to differences between nymphal and larval host associations.

Phylogeny and species reassessment of Hyalopterus (Aphididae, Aphidinae)

AbstractThe broadly distributed genus Hyalopterus currently comprises three formally recognized species that are highly similar morphologically and hence difficult to be identified with certainty. This group has undergone multiple revisions in the past century, but none of these has assessed species from Asia, which has hampered our understanding of the species diversity within this genus. Based on a comprehensive data set from morphological data and host‐associated data, and by coalescent‐based delimitation approaches, the Hyalopterus species boundaries, distribution and diversity were clarified here to further reveal the composition of the species. Two single‐locus (ML‐GMYC and mPTP) and two multilocus (BPP and STACEY) delimitation methods were conducted based on extensive sampling. Then, the phylogenetic relationships and morphological divergence were assessed. Our data strongly supported that the number of recognized species in Hyalopterus had likely been underestimated. The phylogenetic analyses recovered four major clades, which corresponded to distinct host‐plant preferences. Also, the morphological analyses showed significant differentiation for only one of the newly recognized candidate species uncovered by the delimitation approaches, suggesting the existence of at least two independent evolutionary lineages within Hyalopterus arundiniformis, which showed different patterns of host association. Moreover, based on our data, the taxonomic misidentification of H. arundiniformis in China was corrected here. This study lays the groundwork for the thorough taxonomic revision of Hyalopterus and for future evolutionary studies and underlines the importance of an integrated framework for species determination.

A core phyllosphere microbiome exists across distant populations of a tree species indigenous to New Zealand.

The phyllosphere microbiome is increasingly recognised as an influential component of plant physiology, yet it remains unclear whether stable host-microbe associations generally exist in the phyllosphere. Leptospermum scoparium (mānuka) is a tea tree indigenous to New Zealand, and honey derived from mānuka is widely known to possess unique antimicrobial properties. However, the host physiological traits associated with these antimicrobial properties vary widely, and the specific cause of such variation has eluded scientists despite decades of research. Notably, the mānuka phyllosphere microbiome remains uncharacterised, and its potential role in mediating host physiology has not been considered. Working within the prevailing core microbiome conceptual framework, we hypothesise that the phyllosphere microbiome of mānuka exhibits specific host association patterns congruent with those of a microbial community under host selective pressure (null hypothesis: the mānuka phyllosphere microbiome is recruited stochastically from the surrounding environment). To examine our hypothesis, we characterised the phyllosphere and associated soil microbiomes of five distinct and geographically distant mānuka populations across the North Island of New Zealand. We identified a habitat-specific and relatively abundant core microbiome in the mānuka phyllosphere, which was persistent across all samples. In contrast, non-core phyllosphere microorganisms exhibited significant variation across individual host trees and populations that was strongly driven by environmental and spatial factors. Our results demonstrate the existence of a dominant and ubiquitous core microbiome in the phyllosphere of mānuka, supporting our hypothesis that phyllosphere microorganisms of mānuka exhibit specific host association and potentially mediate physiological traits of this nationally and culturally treasured indigenous plant. In addition, our results illustrate biogeographical patterns in mānuka phyllosphere microbiomes and offer insight into factors contributing to phyllosphere microbiome assembly.

Zombie-Ant Fungi Emerged from Non-manipulating, Beetle-Infecting Ancestors.

The manipulation of animal behavior by parasitic organisms is one of the most complex adaptations to have arisen via natural selection. Among the most impressive examples of behavioral manipulation are the zombie-ant fungi [1]. In this association, ants are controlled to leave the colony and perform a stereotyped death grip behavior, where they bite onto vegetation over foraging trails, before being killed for the post mortem fungal growth. Manipulation functions to provide a platform outside the nest, from which fungal parasites actively shoot out spores, targeting foraging ants because within colony transmission is prevented by strong social immunity exhibited by social insect societies [2, 3]. It is not clear how such complex examples of host manipulation arose. To address this, we performed a broad-scale phylogenetic reconstruction of the order Hypocreales, to which the zombie-ant fungi, Ophiocordyceps, belong. In order to understand the patterns of host association and host switching along the evolution of Ophiocordyceps, we performed ancestral character state reconstruction analysis. We found that zombie-ant fungi likely arose from an ancestor that infected beetle larvae residing in soil or decaying wood, similar to extant beetle-infecting Ophiocordyceps species. Surprisingly, the jump led to an extensive species radiation observed after the development of behavioral manipulation. We suggest that the jump from solitary beetle larva to ants within a colony exposed the fungus to the robust social immunity of ant societies.

Microsporidian infections in the species complex Gammarus roeselii (Amphipoda) over its geographical range: evidence for both host\u2013parasite co-diversification and recent host shifts

BackgroundMicrosporidians are obligate endoparasites infecting taxonomically diverse hosts. Both vertical (from mother to eggs) and horizontal (between conspecifics or between species) transmission routes are known. While the former may promote co-speciation and host-specificity, the latter may promote shifts between host species. Among aquatic arthropods, freshwater amphipod crustaceans are hosts for many microsporidian species. However, despite numerous studies, no general pattern emerged about host specificity and co-diversification. In south-eastern Europe, the gammarid Gammarus roeselii is composed of 13 cryptic lineages of Miocene to Pleistocene age but few genotypes of one lineage have spread postglacially throughout north-western Europe. Based on nearly 100 sampling sites covering its entire range, we aim to: (i) explore the microsporidian diversity present in G. roeselii and their phylogenetic relationships, especially in relation to the parasites infecting other Gammaridae; (ii) test if the host phylogeographical history might have impacted host–parasite association (e.g. co-diversifications or recent host shifts from local fauna).MethodsWe used part of the small subunit rRNA gene as source of sequences to identify and determine the phylogenetic position of the microsporidian taxa infecting G. roeselii.ResultsMicrosporidian diversity was high in G. roeselii with 24 detected haplogroups, clustered into 18 species-level taxa. Ten microsporidian species were rare, infecting a few individual hosts in a few populations, and were mostly phylogenetically related to parasites from other amphipods or various crustaceans. Other microsporidians were represented by widespread genera with high prevalence: Nosema, Cucumispora and Dictyocoela. Two contrasting host association patterns could be observed. First, two vertically transmitted microsporidian species, Nosema granulosis and Dictyocoela roeselum, share the pattern of infecting G. roeselii over most of its range and are specific to this host suggesting the co-diversification scenario. This pattern contrasted with that of Dictyocoela muelleri, the three species of Cucumispora, and the rare parasites, present only in the recently colonised region by the host. These patterns suggest recent acquisitions from local host species, after the recent spread of G. roeselii.ConclusionsMicrosporidians infecting G. roeselii revealed two scenarios of host–parasite associations: (i) ancient associations with vertically transmitted parasites that probably co-diversified with their hosts, and (ii) host shifts from local host species, after the postglacial spread of G. roeselii.

Aerotolerance and multilocus sequence typing among Campylobacter jejuni strains isolated from humans, broiler chickens, and cattle in Miyazaki Prefecture, Japan.

Campylobacter jejuni is one of the leading causes of human gastroenteritis in Japan. As chickens and cattle are common reservoirs for C. jejuni, this microaerophilic, stress-sensitive bacterium can overcome and survive various stress conditions during zoonotic transmission, particularly foodborne, to humans. How C. jejuni overcomes stress conditions is, however, unclear. In the present study, 70 C. jejuni strains isolated from various sources (26 human, 20 broilers, and 24 cattle isolates) in Miyazaki, Japan, from 2010 to 2012, were subjected to multilocus sequence typing (MLST) and aerotolerance testing (aerobic shaking at 200 rpm). The results demonstrated that C. jejuni strains from Miyazaki belonged to 12 clonal complexes (CCs) and 43 sequence types (STs). CC-21 and CC-460 were mainly detected in human clinical strains. Most tested strains were aerotolerant, and only one (1.4%) was deemed sensitive to aerobic stress. Approximately 40% strains survived the 24-hr vigorous aerobic shaking at 200 rpm, and these hyper-aerotolerant strains were more prevalent in broiler and cattle isolates than in human isolates. Phylogenetic analysis divided the strains into five clusters, each showing a different pattern of host association. Thus, we have demonstrated for the first time that C. jejuni strains with increased tolerance to aerobic stress are highly prevalent in broilers and cattle in Miyazaki, Japan, and that certain clonal populations are frequently implicated in human infection in this area.

Diversity and Plant Pathogenicity of Bursaphelenchus and Related Nematodes in Relation to Their Vector Bionomics

The nematode genus Bursaphelenchus is a highly divergent group containing fungal feeders and obligate and facultative plant parasites. The genus is also known as the phoretic (and parasitic) associates of many groups of insects. Further, two major plant pathogens, B. xylophilus and B. cocophilus, are members of this genus, and several other species are suspected to be weak to moderate plant pathogens. Here, the diversity of vector insects and host/habitat/plant species interactions, as well as phylogenetic relationships, are summarized for Bursaphelenchus species. The hypothetical origins of plant pathogenicity for different species of Bursaphelenchus are then discussed in relation to the bionomics of their vector insects. Phylogenetic analyses suggest that the genus is separated into four clades, and the basal clade will be further separated into two new genera. Based on a literature survey, the phoretic host association patterns appear different among the other three true Bursaphelenchus clades, i.e., one clade is mostly associated with bark beetles that occupy relatively dry niches (under bark), whereas the other two clades are associated with various groups of insects inhabiting diverse niches in other relatively humid conditions. Plant pathogenicity for a few members is hypothetically derived from the nematodes’ tolerance to the static resistance of host plants, i.e., the nematode species vectored by the insects attacking or interfacing with live plant tissue were provided an opportunity and, in a few cases, possessed the means to manifest plant pathogenicity with serious consequences, i.e., B. xylophilus and B. cocophilus.

Systematics and diversification of Anindobothrium Marques, Brooks & Lasso, 2001 (Eucestoda: Rhinebothriidea).

Tapeworms of the genus Anindobothrium Marques, Brooks & Lasso, 2001 are found in both marine and Neotropical freshwater stingrays of the family Potamotrygonidae. The patterns of host association within the genus support the most recent hypothesis about the history of diversification of potamotrygonids, which suggests that the ancestor of freshwater lineages of the Potamotrygonidae colonized South American river systems through marine incursion events. Despite the relevance of the genus Anindobothrium to understand the history of colonization and diversification of potamotrygonids, no additional efforts were done to better investigate the phylogenetic relationship of this taxon with other lineages of cestodes since its erection. This study is a result of recent collecting efforts to sample members of the genus in marine and freshwater potamotrygonids that enabled the most extensive documentation of the fauna of Anindobothrium parasitizing species of Styracura de Carvalho, Loboda & da Silva, Potamotrygon schroederi Fernández-Yépez, P. orbignyi (Castelnau) and P. yepezi Castex & Castello from six different countries, representing the eastern Pacific Ocean, Caribbean Sea, and river basins in South America (Rio Negro, Orinoco, and Maracaibo). The newly collected material provided additional specimens for morphological studies and molecular samples for subsequent phylogenetic analyses that allowed us to address the phylogenetic position of Anindobothrium and provide molecular and morphological evidence to recognize two additional species for the genus. The taxonomic actions that followed our analyses included the proposition of a new family, Anindobothriidae fam. n., to accommodate the genus Anindobothrium in the order Rhinebothriidea Healy, Caira, Jensen, Webster & Littlewood, 2009 and the description of two new species—one from the eastern Pacific Ocean, A. carrioni sp. n., and the other from the Caribbean Sea, A. inexpectatum sp. n. In addition, we also present a redescription of the type species of the genus, A. anacolum (Brooks, 1977) Marques, Brooks & Lasso, 2001, and of A. lisae Marques, Brooks & Lasso, 2001. Finally, we discuss the paleogeographical events mostly linked with the diversification of the genus and the protocols adopted to uncover cryptic diversity in Anindobothrium.

Plant host relationships of three lineages of the gall-inducing fly Fergusonina Malloch (Diptera: Fergusoninidae) on Eucalyptus L’Hérit.

The gall-inducing fly family Fergusoninidae, in association with a mutualist nematode, induces galls on Myrtaceae. Each fly species typically targets a particular site on its host plant, giving rise to a range of gall types, and one plant species may host at least four fly species. While incongruent fly–host evolutionary time scales preclude early cospeciation, it is possible that Fergusoninidae have been diverging with their host plants more recently at correspondingly finer taxonomic levels, such as within host subgenera. To test this possibility, we reduced the scale of our analysis and focussed on a clade of ten Eucalyptus species, sampling intensively and using a phylogenetic approach to compare the relationships between these plant hosts and their associated flies. We also took advantage of the fact that three different gall types, each with its own clade of Fergusonina flies, could be sampled on this focal host clade, in effect giving us three different host/fly association tests on the one set of hosts. The phylogenies of flies from the three different gall types were estimated using Bayesian analysis of mtCOI sequences and compared with an existing phylogeny of the eucalypt host clade. While each gall type showed a different pattern of host relationships, heuristic and quantitative analyses showed that there was little correspondence between plant and fly phylogenies and we conclude that host switching is prevalent in this system. There was more host fidelity in the flower bud gallers on this group of eucalypts, and there was least in the leaf blade gallers, with the shoot bud gallers demonstrating an intermediate level of host fidelity. We discuss the possible factors which may have led to their patterns of host association. This is the first study of Fergusonina to focus on one clade of Eucalyptus L’Herit. (Myrtaceae) with intensive sampling and shows that each host plant species is commonly used by multiple fergusoninid species. This has provided us with the opportunity to study in detail the host relationships of three separate clades of Fergusonina from different plant tissue types, and has revealed many previously unrecorded host plant/gall site associations.

Identification of two lineages of host-associated eriophyoid mites predisposed to different levels of host diversification

Herbivorous arthropods can diversify as a consequence of evolutionary changes in response to their plant hosts. Current patterns of host association of herbivores are likely to reflect a long evolutionary history of herbivore-plant co-evolution. Here, we used molecular phylogenetics to track the evolutionary history of host shifts and diversification of 66 eriophyoid mites (Acari, Eriophyoidea), and linked past patterns of evolutionary diversification to more recent patterns of divergence by tracking population genetic variation in 13 of the eriophyoid mite species feeding on different gymnosperm hosts. This allowed us to explore the relationship between a past history of diversification and the current potential of mites to undergo host range shifts. We found that population-level diversity across gymnosperm hosts as measured by 28S rRNA markers was greater in species from the mite clade that had radiated across evolutionary time to utilize a variety of hosts including angiosperms, compared to species from the clade that has remained restricted to ancestral gymnosperm hosts. Species from the radiated clade exhibited higher variation in host use. Lineages of mites that have in the past been able to radiate and adapt to diverse plants may therefore be predisposed to continue their expansion on new hosts, although additional clades need to be tested.

The life-cycle of Gorgocephalus yaaji Bray & Cribb, 2005 (Digenea: Gorgocephalidae) with a review of the first intermediate hosts for the superfamily Lepocreadioidea Odhner, 1905.

Using novel molecular and morphological data we elucidated the life-cycle of Gorgocephalus yaaji Bray & Cribb, 2005 from off Lizard Island, on the northern Great Barrier Reef, Australia. ITS2 rDNA sequences generated for larval trematodes from the infected snail species Echinolittorina austrotrochoides Reid (Littorinidae) were identical to those from adult G.yaaji from the fish Kyphosus cinerascens (Forsskål) (Kyphosidae). Cercariae develop in rediae in E. austrotrochoides, emerge from the snail, encyst on algae as metacercariae, and are inferred to then be consumed by the herbivorous definitive fish host, K.cinerascens. In addition, we generated the first ITS2 rDNA sequences for a gorgocephalid previously reported from the littorind gastropod Austrolittorina unifasciata Gray. Although infections previously reported from A.unifasciata were the first larval gorgocephalids characterised, this study is the first to connect an intramolluscan infection to a sexual adult. In light of the new life-cycle information, a review of mollusc associations for the digenean superfamily Lepocreadioidea was performed, highlighting gaps in the knowledge and revealing patterns of host-parasite association. We find that distinct patterns of first intermediate host association are discernible for three lepocreadioid lineages: the Aephnidiogenidae Yamaguti, 1934, Gorgocephalidae Manter, 1966, and the Lepocreadiidae Odhner, 1905. However, the evolutionary origin for these patterns of host association remains unclear.

Host‐adapted aphid populations differ in their migratory patterns and capacity to colonize crops

Summary Although phytophagous insects can vary genetically in host use and exhibit long‐range movements, the combined implications of these phenomena for pest management have received limited attention. To address this, we surveyed the genetic diversity of pea aphid Acyrthosiphon pisum using twelve microsatellite loci and assessed host association patterns and annual movement from a putative source region (Columbia River Basin) to the Palouse region of northern Idaho and western Washington, where the aphid is a pest of pea Pisum sativum. A total of 320 identified unique genotypes clustered into four genetic groups, with two host plant associations: alfalfa Medicago sativa (three genetic groups), and pea Pisum sativum and vetch Vicia villosa (one genetic group). All four genetic groups occurred in the Columbia River Basin and in migrant aphids collected in pan traps during spring colonization in the Palouse during 2 years of this study. Patterns of group arrival on the Palouse were spatially structured early in the season, consistent with differing migration patterns. Despite genetic diversity of migrants, a single genetic group became predominant in pea crops each year. Clonal laboratory colonies of pea aphids established from field‐collected specimens and representing two predominant genetic groups exhibited reciprocal performance trade‐offs, with alfalfa being a poor host for a pea‐associated aphid genotype and vice versa. Synthesis and applications. Annual spring migrants of pea aphids in the pea production region of the Palouse are genetically diverse, with different host plant affinities consistent with origination from source populations in the Columbia River Basin. As the season progresses, a single genetic group adapted to pea becomes predominant in the crop. Management of pea aphid in the Palouse will be improved by monitoring the temporal and spatial variation of specific genetic groups of the aphid arriving as immigrants during each crop season, providing this information to producers and adjusting estimates of risk of crop damage accordingly. The principle could apply to other pest species with host‐adapted populations that colonize crops on an annual basis.

The Identification of Haemonchus Species and Diagnosis of Haemonchosis.

Diagnosis is often equated with identification or detection when discussing parasitic diseases. Unfortunately, these are not necessarily mutually exclusive activities; diseases and infections are generally diagnosed and organisms are identified. Diagnosis is commonly predicated upon some clinical signs; in an effort to determine the causative agent, identification of genera and species is subsequently performed. Both identification and diagnosis play critical roles in managing an infection, and involvethe interplay of direct and indirect methods of detection, particularly in light of the complex and expanding problem of drug-resistance in parasites. Accurate and authoritative identification that is cost- and time-effective, based on structural and molecular attributes of specimens, provides a foundation for defining parasite diversity and changing patterns of geographical distribution, host association and emergence of disease. Most techniques developed thus far have been grounded in assumptions based on strict host associations between Haemonchus contortus and small ruminants, that is, sheep and goats, and between Haemonchus placei and bovids. Current research and increasing empirical evidence of natural infections in the field demonstrates that this assumption misrepresents the host associations for these species of Haemonchus. Furthermore, the capacity of H. contortus to utilize a considerably broad spectrum of ungulate hosts is reflected in our understanding of the role of anthropogenic forcing, the 'breakdown' of ecological isolation, global introduction and host switching as determinants of distribution. Nuanced insights about distribution, host association and epidemiology have emerged over the past 30years, coincidently with the development of increasingly robust means for parasite identification. In this review and for the sake of argument, we would like to delineate the diagnosis of haemonchosis from the identification of the specific pathogen. As a foundation for exploring host and parasite biology, we will examine the evolution of methods for distinguishing H. contortus from other common gastrointestinal nematodes of agriculturally significant and free-ranging wild ruminants using morphological, molecular and/or immunological methods for studies at the species and genus levels.

Fossils of parasites: what can the fossil record tell us about the evolution of parasitism?

Parasites are common in many ecosystems, yet because of their nature, they do not fossilise readily and are very rare in the geological record. This makes it challenging to study the evolutionary transition that led to the evolution of parasitism in different taxa. Most studies on the evolution of parasites are based on phylogenies of extant species that were constructed based on morphological and molecular data, but they give us an incomplete picture and offer little information on many important details of parasite-host interactions. The lack of fossil parasites also means we know very little about the roles that parasites played in ecosystems of the past even though it is known that parasites have significant influences on many ecosystems. The goal of this review is to bring attention to known fossils of parasites and parasitism, and provide a conceptual framework for how research on fossil parasites can develop in the future. Despite their rarity, there are some fossil parasites which have been described from different geological eras. These fossils include the free-living stage of parasites, parasites which became fossilised with their hosts, parasite eggs and propagules in coprolites, and traces of pathology inflicted by parasites on the host's body. Judging from the fossil record, while there were some parasite-host relationships which no longer exist in the present day, many parasite taxa which are known from the fossil record seem to have remained relatively unchanged in their general morphology and their patterns of host association over tens or even hundreds of millions of years. It also appears that major evolutionary and ecological transitions throughout the history of life on Earth coincided with the appearance of certain parasite taxa, as the appearance of new host groups also provided new niches for potential parasites. As such, fossil parasites can provide additional data regarding the ecology of their extinct hosts, since many parasites have specific life cycles and transmission modes which reflect certain aspects of the host's ecology. The study of fossil parasites can be conducted using existing techniques in palaeontology and palaeoecology, and microscopic examination of potential material such as coprolites may uncover more fossil evidence of parasitism. However, I also urge caution when interpreting fossils as examples of parasites or parasitism-induced traces. I point out a number of cases where parasitism has been spuriously attributed to some fossil specimens which, upon re-examination, display traits which are just as (if not more) likely to be found in free-living taxa. The study of parasite fossils can provide a more complete picture of the ecosystems and evolution of life throughout Earth's history.