Search

Brood parasitism involves the exploitation of host parental care rather than the extraction of resources directly from hosts. We identify defining characteristics of this strategy and consider its position along continua with adjacent behaviors but focus on canonical brood parasites, where parasitism is obligate and hosts are noneusocial (thereby distinguishing from social parasitism). A systematic literature survey revealed 59 independently derived brood parasitic lineages with most origins (49) in insects, particularly among bees and wasps, and other origins in birds (seven) and fish (three). Insects account for more than 98% of brood parasitic species, with much of that diversity reflecting ancient (≥100-million-year-old) brood parasitic lineages. Brood parasites usually, but not always, evolve from forms that show parental care. In insects, brood parasitism often first evolves through exploitation of a closely related species, following Emery's rule, but this is less typical in birds, which we discuss. We conducted lineage-level comparisons between brood parasitic clades and their sister groups, finding mixed results but an overall neutral to negative effect of brood parasitism on species richness and diversification. Our review of brood parasites reveals many unanswered questions requiring new research, including further modeling of the coevolutionary dynamics of brood parasites and their hosts. [ABSTRACT FROM AUTHOR]

Abstract Background Parasite evolution has been conceptualized as a process of genetic loss and simplification. Contrary to this model, there is evidence of expansion and conservation of gene families related to essential functions of parasitism in some parasite genomes, reminiscent of widespread mosaic evolution—where subregions of a genome have different rates of evolutionary change. We found evidence of mosaic genome evolution in the cnidarian Myxobolus honghuensis, a myxozoan parasite of fish, with extremely simple morphology. Results We compared M. honghuensis with other myxozoans and free-living cnidarians, and determined that it has a relatively larger myxozoan genome (206 Mb), which is less reduced and less compact due to gene retention, large introns, transposon insertion, but not polyploidy. Relative to other metazoans, the M. honghuensis genome is depleted of neural genes and has only the simplest animal immune components. Conversely, it has relatively more genes involved in stress resistance, tissue invasion, energy metabolism, and cellular processes compared to other myxozoans and free-living cnidarians. We postulate that the expansion of these gene families is the result of evolutionary adaptations to endoparasitism. M. honghuensis retains genes found in free-living Cnidaria, including a reduced nervous system, myogenic components, ANTP class Homeobox genes, and components of the Wnt and Hedgehog pathways. Conclusions Our analyses suggest that the M. honghuensis genome evolved as a mosaic of conservative, divergent, depleted, and enhanced genes and pathways. These findings illustrate that myxozoans are not as genetically simple as previously regarded, and the evolution of some myxozoans is driven by both genomic streamlining and expansion.

Background: Parasite evolution has been conceptualized as a process of genetic loss and simplification. Contrary to this model, there is evidence of expansion and conservation of gene families related to essential functions of parasitism in some parasite genomes, reminiscent of widespread mosaic evolution—where subregions of a genome have different rates of evolutionary change. We found evidence of mosaic genome evolution in the cnidarian Myxobolus honghuensis, a myxozoan parasite of fish, with extremely simple morphology. Results: We compared M. honghuensis with other myxozoans and free-living cnidarians, and determined that it has a relatively larger myxozoan genome (206 Mb), which is less reduced and less compact due to gene retention, large introns, transposon insertion, but not polyploidy. Relative to other metazoans, the M. honghuensis genome is depleted of neural genes and has only the simplest animal immune components. Conversely, it has relatively more genes involved in stress resistance, tissue invasion, energy metabolism, and cellular processes compared to other myxozoans and free-living cnidarians. We postulate that the expansion of these gene families is the result of evolutionary adaptations to endoparasitism. M. honghuensis retains genes found in free-living Cnidaria, including a reduced nervous system, myogenic components, ANTP class Homeobox genes, and components of the Wnt and Hedgehog pathways. Conclusions: Our analyses suggest that the M. honghuensis genome evolved as a mosaic of conservative, divergent, depleted, and enhanced genes and pathways. These findings illustrate that myxozoans are not as genetically simple as previously regarded, and the evolution of some myxozoans is driven by both genomic streamlining and expansion. [ABSTRACT FROM AUTHOR]

Nematodes are naturally infected by the fungal-related pathogen microsporidia. These ubiquitous eukaryotic parasites are poorly understood, despite infecting most types of animals. Identifying novel species of microsporidia and studying them in an animal model can expedite our understanding of their infection biology and evolution. Nematodes present an excellent avenue for pursuing such work, as they are abundant in the environment and many species are easily culturable in the laboratory. The protocols presented here describe how to isolate bacterivorous nematodes from rotting substrates, screen them for microsporidia infection, and molecularly identify the nematode and microsporidia species. Additionally, we detail how to remove environmental contaminants and generate a spore preparation of microsporidia from infected samples. We also discuss potential pitfalls and provide suggestions on how to mitigate them. These protocols allow for the identification of novel microsporidia species, which can serve as an excellent starting point for genomic analysis, determination of host specificity, and infection characterization. © 2024 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: Gathering samples Support Protocol 1: Generating 10× and 40× Escherichia coli OP50 and seeding NGM plates Basic Protocol 2: Microsporidia screening, testing for Caenorhabditis elegans susceptibility, and sample freezing Basic Protocol 3: DNA extraction, PCR amplification, and sequencing to identify nematode and microsporidia species Basic Protocol 4: Removal of contaminating microbes and preparation of microsporidia spores Support Protocol 2: Bleach-synchronizing nematodes., (© 2024 The Authors. Current Protocols published by Wiley Periodicals LLC.)

Background: Rodent malaria parasites (RMPs) serve as tractable tools to study malaria parasite biology and host-parasite-vector interactions. Among the four RMPs originally collected from wild thicket rats in sub-Saharan Central Africa and adapted to laboratory mice, Plasmodium vinckei is the most geographically widespread with isolates collected from five separate locations. However, there is a lack of extensive phenotype and genotype data associated with this species, thus hindering its use in experimental studies. Results: We have generated a comprehensive genetic resource for P. vinckei comprising of five reference-quality genomes, one for each of its subspecies, blood-stage RNA sequencing data for five P. vinckei isolates, and genotypes and growth phenotypes for ten isolates. Additionally, we sequenced seven isolates of the RMP species Plasmodium chabaudi and Plasmodium yoelii, thus extending genotypic information for four additional subspecies enabling a re-evaluation of the genotypic diversity and evolutionary history of RMPs. The five subspecies of P. vinckei have diverged widely from their common ancestor and have undergone large-scale genome rearrangements. Comparing P. vinckei genotypes reveals region-specific selection pressures particularly on genes involved in mosquito transmission. Using phylogenetic analyses, we show that RMP multigene families have evolved differently across the vinckei and berghei groups of RMPs and that family-specific expansions in P. chabaudi and P. vinckei occurred in the common vinckei group ancestor prior to speciation. The erythrocyte membrane antigen 1 and fam-c families in particular show considerable expansions among the lowland forest-dwelling P. vinckei parasites. The subspecies from the highland forests of Katanga, P. v. vinckei, has a uniquely smaller genome, a reduced multigene family repertoire and is also amenable to transfection making it an ideal parasite for reverse genetics. We also show that P. vinckei parasites are amenable to genetic crosses. Conclusions: Plasmodium vinckei isolates display a large degree of phenotypic and genotypic diversity and could serve as a resource to study parasite virulence and immunogenicity. Inclusion of P. vinckei genomes provide new insights into the evolution of RMPs and their multigene families. Amenability to genetic crossing and transfection make them also suitable for classical and functional genetics to study Plasmodium biology. [ABSTRACT FROM AUTHOR]

Classical theory suggests that parasites will exhibit higher fitness in sympatric relative to allopatric host populations (local adaptation). However, evidence for local adaptation in natural host–parasite systems is often equivocal, emphasizing the need for infection experiments conducted over realistic geographic scales and comparisons among species with varied life history traits. Here, we used infection experiments to test how two trematode (flatworm) species (Paralechriorchis syntomentera and Ribeiroia ondatrae) with differing dispersal abilities varied in the strength of local adaptation to their amphibian hosts. Both parasites have complex life cycles involving sequential transmission among aquatic snails, larval amphibians and vertebrate definitive hosts that control dispersal across the landscape. By experimentally pairing 26 host‐by‐parasite population infection combinations from across the western USA with analyses of host and parasite spatial genetic structure, we found that increasing geographic distance—and corresponding increases in host population genetic distance—reduced infection success for P. syntomentera, which is dispersed by snake definitive hosts. For the avian‐dispersed R. ondatrae, in contrast, the geographic distance between the parasite and host populations had no influence on infection success. Differences in local adaptation corresponded to parasite genetic structure; although populations of P. syntomentera exhibited ~10% mtDNA sequence divergence, those of R. ondatrae were nearly identical (<0.5%), even across a 900 km range. Taken together, these results offer empirical evidence that high levels of dispersal can limit opportunities for parasites to adapt to local host populations. [ABSTRACT FROM AUTHOR]

The identification keys are the main tool for plant identification. However, the absence of a recent and up-to-date key to the botanical families present in Cuba greatly hinders the identification process by non-specialist researchers of the different groups. Here are seven keys for the identification of families of angiosperms of the flora of Cuba within selected morphological groups: terrestrial plants with compound and opposite leaves, plants with trifoliolate leaves, with translucent punctuation, with latex, climbing with tendrils, parasites and epiphytic angiosperms. [ABSTRACT FROM AUTHOR]

Abstract Background The specialist-generalist variation hypothesis (SGVH) in parasites suggests that, due to patchiness in habitat (host availability), specialist species will show more subdivided population structure when compared to generalist species. In addition, since specialist species are more prone to local stochastic extinction events with their hosts, they will show lower levels of intraspecific genetic diversity when compared to more generalist. Results To test the wider applicability of the SGVH we compared 337 cytochrome oxidase I mitochondrial DNA and 268 nuclear tropomyosin DNA sequenced fragments derived from two co-distributed Laelaps mite species and compared the data to 294 COI mtDNA sequences derived from the respective hosts Rhabdomys dilectus, R. bechuanae, Mastomys coucha and M. natalensis. In support of the SGVH, the generalist L. muricola was characterized by a high mtDNA haplotypic diversity of 0.97 (±0.00) and a low level of population differentiation (mtDNA Fst = 0.56, p

Understanding how ecology and phylogeny shape parasite communities can inform parasite control and wildlife conservation initiatives while contributing to the study of host species evolution.We tested the relative strengths of phylogeny and ecology in driving parasite community structure in a host whose ecology diverges significantly from that of its closest phylogenetic relatives.We characterized the gastrointestinal (GI) parasite community of wild geladas Theropithecus gelada, primates that are closely related to baboons but specialized to graminovory in the Ethiopian Highlands.Geladas exhibited very constrained GI parasite communities: only two genera (Oesophagostomum and Trichostrongylus) were identified across 305 samples. This is far below the diversity reported for baboons (Papio spp.) and at the low end of the range of domestic grazers (e.g. Bos taurus, Ovis aries) inhabiting the same region and ecological niche.Using deep amplicon sequencing, we identified 15 amplicon sequence variants (ASVs) within the two genera, seven of which matched to Oesophagostomum sp., seven to Trichostrongylus sp., and one to T. vitrinus.Population was an important predictor of ASV richness. Geladas in the most ecologically disturbed area of the national park exhibited approximately four times higher ASV richness than geladas at a less disturbed location within the park.In this system, ecology was a stronger predictor of parasite community structure than was phylogeny, with geladas sharing more elements of their parasite communities with other grazers in the same area than with closely related sister taxa. A free Plain Language Summary can be found within the Supporting Information of this article. [ABSTRACT FROM AUTHOR]

Many hypotheses attempt to explain parasite–host associations, but rarely are they examined together in a single community. For hosts, key traits are the proportion of infected individuals (prevalence) and the diversity of parasites infecting them. A key parasite trait is host specificity, ranging from specialists infecting one or a few closely related species to generalists infecting many species. We tested 10 hypotheses to explain host‐parasite associations; five 'host‐centric' (e.g. prevalence is related to host abundance) and five 'parasite‐centric' (e.g. parasite abundance is related to host specificity). We analyzed a community of 67 locally transmitted avian haemosporidian parasite lineages (genera Plasmodium, Haemoproteus or Leucocytozoon), sampled from 2726 birds (64 species) in southern Sweden. Among host‐centric hypotheses, Haemoproteus and Leucocytozoon prevalence and Haemoproteus diversity were related to host habitat preferences, whereas there were no relationships with host abundance or body mass. Haemoproteus and Leucocytozoon prevalences were more similar among closely related than among distantly related host species. Haemoproteus prevalence and diversity were lower in host species with few close relatives ('evolutionarily distinct' hosts). Among parasite‐centric hypotheses, most lineages, even relative generalists, infected closely related host species more often than expected by chance. However, the host species of Haemoproteus and Leucocytozoon lineages overlapped less among lineages than expected by chance. Specialists did not reach higher prevalences than generalists on single host species. However, the abundance of Haemoproteus lineages was related to host specificity with generalists more common than specialists; this was driven by three closely related generalists. Host specificity of parasites was unrelated to the abundance or evolutionarily distinctiveness of their hosts. Parasite communities are likely structured by many factors and cannot be explained by hypotheses focusing solely on hosts or parasites. However, we found consistent effects of host phylogenetic relationships, plausibly a result of evolutionarily conserved host immune systems limiting parasite distributions. [ABSTRACT FROM AUTHOR]

In order to gain an evolutionary perspective on host-parasite-microbe interactions, evolutionary studies encompassing microbes across host and parasite species are necessary to identify patterns of cospeciation and speciation following host shifts. With appropriate experimental systems, geographic variations affecting the role of microbes in host-parasite interactions can be assessed by using a complete cross-experimental design, in which hosts from different localities are infected with parasites from their corresponding localities in the presence of either microbes isolated from the same localities or microbes from different test localities. Finally, when possible, experimental evolution of parasites and hosts in the presence or absence of the identified microbes can been used to test the effect of specific microbes on the evolution of the system and to identify mechanisms involved in parasite-microbe interaction. Phase one will compile information on previously characterized parasite-associated microbes and parasite-microbe interactions (already partially reviewed in [[15]-[16], [53]]), mine genomic and transcriptomic databases to detect microbial sequences, and characterize the complete microbiome of a set of parasites representing diverse taxa and environments. [Extracted from the article]

NAD kinase (NADK) is the sole enzyme that phosphorylates nicotinamide adenine dinucleotide (NAD+/NADH) into NADP+/NADPH, which provides the chemical reducing power in anabolic (biosynthetic) pathways. While prokaryotes typically encode a single NADK, eukaryotes encode multiple NADKs. How these different NADK genes are all related to each other and those of prokaryotes is not known. Here we conduct phylogenetic analysis of NADK genes and identify major clade-defining patterns of NADK evolution. First, almost all eukaryotic NADK genes belong to one of two ancient eukaryotic sister clades corresponding to cytosolic (“cyto”) and mitochondrial (“mito”) clades. Secondly, we find that the cyto-clade NADK gene is duplicated in connection with loss of the mito-clade NADK gene in several eukaryotic clades or with acquisition of plastids in Archaeplastida. Thirdly, we find that horizontal gene transfers from proteobacteria have replaced mitochondrial NADK genes in only a few rare cases. Last, we find that the eukaryotic cyto and mito paralogs are unrelated to independent duplications that occurred in sporulating bacteria, once in mycelial Actinobacteria and once in aerobic endospore-forming Firmicutes. Altogether these findings show that the eukaryotic NADK gene repertoire is ancient and evolves episodically with major evolutionary transitions. [ABSTRACT FROM AUTHOR]

The origin and subsequent maintenance of sex and recombination are among the most elusive and controversial problems in evolutionary biology. Here, we propose a novel hypothesis, suggesting that sexual reproduction not only evolved to reduce the negative effects of the accumulation of deleterious mutations and processes associated with pathogen and/or parasite resistance but also to prevent invasion by transmissible selfish neoplastic cheater cells, henceforth referred to as transmissible cancer cells. Sexual reproduction permits systematic change of the multicellular organism's genotype and hence an enhanced detection of transmissible cancer cells by immune system. Given the omnipresence of oncogenic processes in multicellular organisms, together with the fact that transmissible cancer cells can have dramatic effects on their host fitness, our scenario suggests that the benefits of sex and concomitant recombination will be large and permanent, explaining why sexual reproduction is, despite its costs, the dominant mode of reproduction among eukaryotes. [ABSTRACT FROM AUTHOR]

Within‐host interactions between co‐infecting parasites can significantly influence the evolution of key parasite traits, such as virulence (pathogenicity of infection). The type of interaction is expected to predict the direction of selection, with antagonistic interactions favouring more virulent genotypes and synergistic interactions less virulent genotypes. Recently, it has been suggested that virulence can further be affected by the genetic identity of co‐infecting partners (G × G interactions), complicating predictions on disease dynamics. Here, we used a natural host–parasite system including a fish host and a trematode parasite to study the effects of G × G interactions on infection virulence. We exposed rainbow trout (Oncorhynchus mykiss) either to single genotypes or to mixtures of two genotypes of the eye fluke Diplostomum pseudospathaceum and estimated parasite infectivity (linearly related to pathogenicity of infection, measured as coverage of eye cataracts) and relative cataract coverage (controlled for infectivity). We found that both traits were associated with complex G × G interactions, including both increases and decreases from single infection to co‐infection, depending on the genotype combination. In particular, combinations where both genotypes had low average infectivity and relative cataract coverage in single infections benefited from co‐infection, while the pattern was opposite for genotypes with higher performance. Together, our results show that infection outcomes vary considerably between single and co‐infections and with the genetic identity of the co‐infecting parasites. This can result in variation in parasite fitness and consequently impact evolutionary dynamics of host–parasite interactions. [ABSTRACT FROM AUTHOR]

MHC genes, which code for proteins responsible for presenting pathogen-derived antigens to the host immune system, show remarkable copy-number variation both between and within species. However, the evolutionary forces driving this variation are poorly understood. Here, we use computer simulations to investigate whether evolution of the number of MHC variants in the genome can be shaped by the number of pathogen species the host population encounters (pathogen richness). Our model assumed that while increasing a range of pathogens recognised, expressing additional MHC variants also incurs costs such as an increased risk of autoimmunity. We found that pathogen richness selected for high MHC copy number only when the costs were low. Furthermore, the shape of the association was modified by the rate of pathogen evolution, with faster pathogen mutation rates selecting for increased host MHC copy number, but only when pathogen richness was low to moderate. Thus, taking into account factors other than pathogen richness may help explain wide variation between vertebrate species in the number of MHC genes. Within population, variation in the number of unique MHC variants carried by individuals (INV) was observed under most parameter combinations, except at low pathogen richness. This variance gave rise to positive correlations between INV and host immunocompetence (proportion of pathogens recognised). However, within-population variation in host immunocompetence declined with pathogen richness. Thus, counterintuitively, pathogens can contribute more to genetic variance for host fitness in species exposed to fewer pathogen species, with consequences to predictions from “Hamilton-Zuk” theory of sexual selection. [ABSTRACT FROM AUTHOR]

The impact of infectious disease is often very different in juveniles and adults, but theory has focused on the drivers of stage‐dependent defense in hosts rather than the potential for stage‐dependent virulence evolution in parasites. Stage structure has the potential to be important to the evolution of pathogens because it exposes parasites to heterogeneous environments in terms of both host characteristics and transmission pathways. We develop a stage‐structured (juvenile–adult) epidemiological model and examine the evolutionary outcomes of stage‐specific virulence under the classic assumption of a transmission‐virulence trade‐off. We show that selection on virulence against adults remains consistent with the classic theory. However, the evolution of juvenile virulence is sensitive to both demography and transmission pathway with higher virulence against juveniles being favored either when the transmission pathway is assortative (juveniles preferentially interact together) and the juvenile stage is long, or in contrast when the transmission pathway is disassortative and the juvenile stage is short. These results highlight the potentially profound effects of host stage structure on determining parasite virulence in nature. This new perspective may have broad implications for both understanding and managing disease severity. [ABSTRACT FROM AUTHOR]

Background: Alveolar echinococcosis (AE) is a lethal zoonosis caused by the metacestode larva of the tapeworm Echinococcus multilocularis. The infection is characterized by tumour-like growth of the metacestode within the host liver, leading to extensive fibrosis and organ-failure. The molecular mechanisms of parasite organ tropism towards the liver and influences of liver cytokines and hormones on parasite development are little studied to date. Methodology/Principal findings: We show that the E. multilocularis larval stage expresses three members of the fibroblast growth factor (FGF) receptor family with homology to human FGF receptors. Using the Xenopus expression system we demonstrate that all three Echinococcus FGF receptors are activated in response to human acidic and basic FGF, which are present in the liver. In all three cases, activation could be prevented by addition of the tyrosine kinase (TK) inhibitor BIBF 1120, which is used to treat human cancer. At physiological concentrations, acidic and basic FGF significantly stimulated the formation of metacestode vesicles from parasite stem cells in vitro and supported metacestode growth. Furthermore, the parasite’s mitogen activated protein kinase signalling system was stimulated upon addition of human FGF. The survival of metacestode vesicles and parasite stem cells were drastically affected in vitro in the presence of BIBF 1120. Conclusions/Significance: Our data indicate that mammalian FGF, which is present in the liver and upregulated during fibrosis, supports the establishment of the Echinococcus metacestode during AE by acting on an evolutionarily conserved parasite FGF signalling system. These data are valuable for understanding molecular mechanisms of organ tropism and host-parasite interaction in AE. Furthermore, our data indicate that the parasite’s FGF signalling systems are promising targets for the development of novel drugs against AE. [ABSTRACT FROM AUTHOR]

Genome sequencing data have recently demonstrated that eukaryote evolution has been remarkably influenced by the acquisition of a large number of genes by horizontal gene transfer (HGT) across different kingdoms. However, in depth-studies on the physiological traits conferred by these accidental DNA acquisitions are largely lacking. Here we elucidate the functional role of Sl gasmin, a gene of a symbiotic virus of a parasitic wasp that has been transferred to an ancestor of the moth species Spodoptera littoralis and domesticated. This gene is highly expressed in circulating immune cells (haemocytes) of larval stages, where its transcription is rapidly boosted by injection of microorganisms into the body cavity. RNAi silencing of Sl gasmin generated a phenotype characterized by a precocious suppression of phagocytic activity by haemocytes, which was rescued when these immune cells were incubated in plasma samples of control larvae, containing high levels of the encoded protein. Proteomic analysis demonstrated that the protein Sl gasmin is released by haemocytes into the haemolymph, where it opsonizes the invading bacteria to promote their phagocytosis, both in vitro and in vivo. Our results show that important physiological traits do not necessarily originate from evolution of pre-existing genes, but can be acquired by HGT events, through unique pathways of symbiotic evolution. These findings indicate that insects can paradoxically acquire selective advantages with the help of their natural enemies. [ABSTRACT FROM AUTHOR]

Avian malaria and related haemosporidians (Plasmodium, [Para]Haemoproteus and Leucocytoozoon) represent an exciting multihost, multiparasite system in ecology and evolution. Global research in this field accelerated after the publication in 2000 of PCR protocols to sequence a haemosporidian mitochondrial (mtDNA) barcode and the development in 2009 of an open‐access database to document the geographic and host ranges of parasite mtDNA haplotypes. Isolating haemosporidian nuclear DNA from bird hosts, however, has been technically challenging, slowing the transition to genomic‐scale sequencing techniques. We extend a recently developed sequence capture method to obtain hundreds of haemosporidian nuclear loci from wild bird samples, which typically have low levels of infection, or parasitemia. We tested 51 infected birds from Peru and New Mexico and evaluated locus recovery in light of variation in parasitemia, divergence from reference sequences and pooling strategies. Our method was successful for samples with parasitemia as low as ~0.02% (2 of 10,000 blood cells infected) and mtDNA divergence as high as 15.9% (one Leucocytozoonsample), and using the most cost‐effective pooling strategy tested. Phylogenetic relationships estimated with >300 nuclear loci were well resolved, providing substantial improvement over the mtDNA barcode. We provide protocols for sample preparation and sequence capture including custom probe sequences and describe our bioinformatics pipeline using atram 2.0, phyluce and custom Perl/Python scripts. This approach can be applied to thousands of avian samples that have already been found to have haemosporidian infections of at least moderate intensity, greatly improving our understanding of parasite speciation, biogeography and evolutionary dynamics. [ABSTRACT FROM AUTHOR]

Adaptation in extended populations often occurs through multiple independent mutations responding in parallel to a common selection pressure. As the mutations spread concurrently through the population, they leave behind characteristic patterns of polymorphism near selected loci—so-called soft sweeps—which remain visible after adaptation is complete. These patterns are well-understood in two limits of the spreading dynamics of beneficial mutations: the panmictic case with complete absence of spatial structure, and spreading via short-ranged or diffusive dispersal events, which tessellates space into distinct compact regions each descended from a unique mutation. However, spreading behaviour in most natural populations is not exclusively panmictic or diffusive, but incorporates both short-range and long-range dispersal events. Here, we characterize the spatial patterns of soft sweeps driven by dispersal events whose jump distances are broadly distributed, using lattice-based simulations and scaling arguments. We find that mutant clones adopt a distinctive structure consisting of compact cores surrounded by fragmented “haloes” which mingle with haloes from other clones. As long-range dispersal becomes more prominent, the progression from diffusive to panmictic behaviour is marked by two transitions separating regimes with differing relative sizes of halo to core. We analyze the implications of the core-halo structure for the statistics of soft sweep detection in small genomic samples from the population, and find opposing effects of long-range dispersal on the expected diversity in global samples compared to local samples from geographic subregions of the range. We also discuss consequences of the standing genetic variation induced by the soft sweep on future adaptation and mixing. [ABSTRACT FROM AUTHOR]

Abstract Regeneration, the ability to restore body parts after an injury or an amputation, is a widespread but highly variable and complex phenomenon in animals. While having fascinated scientists for centuries, fundamental questions about the cellular basis of animal regeneration as well as its evolutionary history remain largely unanswered. Here, we present a study of regeneration of the marine annelid Platynereis dumerilii , an emerging comparative developmental biology model, which, like many other annelids, displays important regenerative abilities. When P. dumerilii worms are amputated, they are able to regenerate the posteriormost differentiated part of their body and a stem cell-rich growth zone that allows the production of new segments replacing the amputated ones. We show that posterior regeneration is a rapid process that follows a well reproducible path and timeline, going through specific stages that we thoroughly defined. Wound healing is achieved one day after amputation and a regeneration blastema forms one day later. At this time point, some tissue specification already occurs, and a functional posterior growth zone is re-established as early as three days after amputation. Regeneration timing is only influenced, in a minor manner, by worm size. Comparable regenerative abilities are found for amputations performed at different positions along the antero-posterior axis of the worm, except when amputation planes are very close to the pharynx. Regenerative abilities persist upon repeated amputations without important alterations of the process. We also show that intense cell proliferation occurs during regeneration and that cell divisions are required for regeneration to proceed normally. Finally, 5-ethynyl-2'-deoxyuridine (EdU) pulse and chase experiments suggest that blastemal cells mostly derive from the segment immediately abutting the amputation plane. The detailed characterization of P. dumerilii posterior body regeneration presented in this article provides the foundation for future mechanistic and comparative studies of regeneration in this species. Highlights • Upon amputation Platynereis worms regenerate their posterior body part. • Regeneration is a rapid process that passes through reproducible stages. • Regeneration involves the formation of a blastema and requires cell proliferation. • Blastemal cells express markers of pluripotent/multipotent stem cells. • Blastemal cells mostly derive from the segment adjacent to the amputation site. [ABSTRACT FROM AUTHOR]

Acoustic signals play an important role in premating isolation based on sexual selection within many taxa. Many male parasitic wasps produce characteristic courtship songs used by females in mate selection. In Cotesia (Hymenoptera: Braconidae: Microgastrinae), courtship songs are generated by wing fanning with repetitive pulses in stereotypical patterns. Our objectives were to sample the diversity of courtship songs within Cotesia and to identify e underlying patterns of differentiation. We compared songs among 12 of ca. 80 Cotesia species in North America, including ten species that have not been recorded previously. For Cotesia congregata, we compared songs of wasps originating from six different host-foodplant sources, two of which are considered incipient species. Songs of emergent males from wild caterpillar hosts in five different families were recorded, and pattern, frequency, and duration of song elements analyzed. Principal component analysis converted the seven elements characterized into four uncorrelated components used in a hierarchical cluster analysis and grouped species by similarity of song structure. Species songs varied significantly in duration of repeating pulse and buzz elements and/or in fundamental frequency. Cluster analysis resolved similar species groups in agreement with the most recent molecular phylogeny for Cotesia spp., indicating the potential for using courtship songs as a predictor of genetic relatedness. Courtship song analysis may aid in identifying closely related cryptic species that overlap spatially, and provide insight into the evolution of this highly diverse and agriculturally important taxon. [ABSTRACT FROM AUTHOR]

Leeches are a unique group of annelids arising from an ancestor that would be characterized as a freshwater oligochaete worm. Comparative biology of the oligochaetes and the leeches reveals that body plan changes in the oligochaete‐to‐leech transition probably occurred by addition or modification of the terminal steps in embryonic development and that they were likely driven by a change in the feeding behavior in the ancestor of leeches. In this review article, developmental changes that are associated with the evolution of several leech‐specific traits are discussed. These include (1) the evolution of suckers, (2) the loss of chaetae, (3) the loss of septa, and (4) a fixed number of segments. An altered developmental fate of the teloblast is further proposed to be a key factor contributing to the fixation of the segment number, and the evolutionary change in teloblast development may also account for the loss of the ability to regenerate the lost body segments in the leech. Comparative biology of the oligochaetes and the leeches reveals that body plan changes in the oligochaete‐to‐leech transition probably occurred by addition or modification of the terminal steps in embryonic development and that they were likely driven by a change in the feeding behavior in the ancestor of leeches. In this review article, developmental changes that are associated with the evolution of several leech‐specific traits are discussed. [ABSTRACT FROM AUTHOR]

Background: This study aimed to investigate the prevalence of fascioliasis and to perform a climatological analysis of different regions of Iran based on the current situation of the parasite and its intermediate host using Geographical Information System (GIS). Methods: Meteorological data were obtained from Iran Meteorological Organization. Risk map of fascioliasis transmission was prepared based on this data and using forecasting indices. Further, the number of fascioliasis cases from 31 provinces reported to the Iran Veterinary Organization were collected and prevalence maps of livestock fascioliasis were drawn. Results: The main risk hotspots were found in Northern provinces like Golestan, Mazandaran and Gilan as well as some Southern provinces such as Kohgiluyeh and Boyer-Ahmad and Chaharmahal and Bakhtiari and Fars, which have ideal conditions for completion of the parasite life cycle. Moreover, Gilan Province with 10.83% had the highest rate of fascioliasis infection in slaughtered animal. Conclusion: Iran is one of the most important foci of fascioliasis globally. Several provinces of Iran have appropriate conditions for evolution of parasite life cycle and presence of its intermediate host. These regions require special attention and serious determination in order to control fascioliasis in human and animals. [ABSTRACT FROM AUTHOR]

Parasitemia generated by Anaplasma marginale causes significant losses in the cattle industry. A major constraint to the effective control and management of anaplasmosis in livestock is the lack of a rapid and reliable diagnostic test to identify the parasite and allow for immediate therapy. In the present study, we developed a novel DNA-based assay for the detection of A. marginale in bovine blood samples, using loop-mediated isothermal amplification (LAMP). DNA from six cattle and hemoparasite samples (Babesia bovis, Babesia bigemina, Anaplasma centrale and A. marginale) were tested for specificity, sensitivity and cross-reactions. The developed LAMP procedures were also confirmed and compared with the qPCR method. The same gene sequence (major surface protein 1b, msp1b) of A. marginale was used to design a set of primers for the LAMP and qPCR assays. The results showed that LAMP is specific, as no positive signal was observed for the other tested hemoparasites. However, the sensitivity of the qPCR assay was ten times higher than LAMP. Our findings indicate that this LAMP method has a good sensitivity and high specificity for the detection of A. marginale and may have a potential application in the detection and differentiation of bovine anaplasmosis. [ABSTRACT FROM AUTHOR]

The success of biological control may depend on the control agent co-evolving with its target pest species, precluding the emergence of resistance that often undermines chemical control. However, recent evidence of a decline in attack rates of a sexual pest weevil by its asexual parasitoid suggests that evolutionary arms races may not prevent the emergence of resistance if the host and parasitoid do not have reproductive strategies that generate equal amounts of genetic variation. To understand how these asymmetries in reproductive strategies may drive the emergence of resistance, we combined life history data from two pest weevils and their parasitoids (one sexual and one asexual) in the New Zealand pastoral ecosystem, with a population dynamic model that allows the coevolution of hosts and parasitoids. We found that the ratio of the genetic variance of hosts to parasitoids was a key determinant of the emergence of resistance. Host resistance eventually occurred unless the parasitoids had considerably greater additive genetic variance than their host. The higher reproductive rate of asexual parasitoids did little to offset the cost of reduced additive genetic variance. The model predictions were congruent with long-term parasitism rates observed in the field for both of the pests considered (one with a sexual and one with an asexual parasitoid). We then explored the consequences of introducing two parasitoids with different reproductive strategies that attack the same sexual host. The model showed that the sexually reproducing parasitoid always out-competed the asexually reproducing one. Our study shows that any asymmetry in reproductive strategies is extremely important for predicting the long-term success of biological control agents. Fortunately, introduction of sexually reproducing individuals after an initial introduction of asexual strains may overcome the problems of host resistance. We conclude that evolution must be considered when evaluating the long-term outcomes of importation biological control. [ABSTRACT FROM AUTHOR]

Parasite dispersal can shape host–parasite interactions at both deep and shallow timescales. One approach to understanding the effects of dispersal is to study parasite lineages that differ in dispersal capability but are from the same group of hosts. In this study, we compared phylogenetic and population genetic patterns of wing and body lice from ground‐doves. Wing lice are more capable of dispersal than body lice. We sequenced full genomes of individual lice for multiple representatives of several wing and body louse species. From these data, we assembled genes for phylogenetic analysis and called SNPs for population genetic analysis. At the phylogenetic level, body lice showed more codivergence with their hosts than did wing lice. However, both wing and body lice exhibited some phylogenetic congruence with their hosts. Within species, body lice showed more population genetic structure than wing lice, although both types of lice showed some structure according to biogeography. Body lice also had significantly lower heterozygosity than wing lice, suggesting more inbreeding. Our results demonstrate that dispersal can shape a host–parasite system across evolutionary time, but also that other factors (e.g., host association and biogeography) can have varying degrees of influence on different groups of parasites and at different evolutionary scales. [ABSTRACT FROM AUTHOR]

Organisms are locked in an eternal struggle with parasitic DNA sequences that live inside their genomes and wreak havoc on their host’s chromosomes as they spread through populations. To combat these parasites, host species have evolved elaborate mechanisms of resistance that suppress their activity. A new study in Drosophila indicates that, prior to the acquisition of resistance, individuals can vary in their ability to tolerate the activity of these genomic parasites, ignoring or repairing the damage they induce. This tolerance results from variation at genes involved in germline development and DNA damage checkpoints and suggests that these highly conserved cellular processes may be influenced by current and historical intragenomic parasite loads. [ABSTRACT FROM AUTHOR]

Nematode parasites rely on successful host infection to perpetuate their species. Infection by individual nematode parasites can be risky, however; any one individual could be killed by the host’s immune response. Here we use a model system to show that environmental cues and parasite past experience can be used by entomopathogenic nematodes to reduce individual risk of infection. Past parasite experience can more than double the infective virulence (number of host invaders) of a given cohort of entomopathogenic nematode parasites. This plasticity in individual parasite risk-taking and associated infection can be used to manage infection of parasitic nematodes: enhancing biological control with entomopathogenic nematodes and developing behavioral and chemical strategies to reduce infection by vertebrate and plant parasitic nematodes. [ABSTRACT FROM AUTHOR]

Sexual reproduction and meiotic recombination generate new genetic combinations and may thereby help an individual infected by a parasite to protect its offspring from being infected. While this idea is often used to understand the evolutionary forces underlying the maintenance of sex and recombination, it also suggests that infected individuals should increase plastically their rate of recombination. We tested the latter idea with the mosquito Aedes aegypti and asked whether females infected by the microsporidian Vavraia culicis were more likely to have recombinant offspring than uninfected females. To measure the rate of recombination over a chromosome we analysed combinations of microsatellites on chromosome 3 in infected and uninfected females, in the (uninfected) males they copulated with and in their offspring. As predicted, the infected females were more likely to have recombinant offspring than the uninfected ones. These results show the ability of a female to diversify her offspring in response to parasitic infection by plastically increasing her recombination rate. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • We quantified phylogenetic signal in avian haemosporidian host specificity. • Sister lineages differ in host specificity. • Larger clades can be relatively specialised or generalised. Abstract Parasites can vary in the number of host species they infect, a trait known as "host specificity". Here we quantify phylogenetic signal—the tendency for closely related species to resemble each other more than distantly related species—in host specificity of avian haemosporidian parasites (genera Plasmodium , Haemoproteus and Leucocytozoon) using data from MalAvi, the global avian haemosporidian database. We used the genetic data (479 base pairs of cytochrome b) that define parasite lineages to produce genus level phylogenies. Combining host specificity data with those phylogenies revealed significant levels of phylogenetic signal while controlling for sampling effects; phylogenetic signal was higher when the phylogenetic diversity of hosts was taken into account. We then tested for correlations in the host specificity of pairs of sister lineages. Correlations were generally close to zero for all three parasite genera. These results suggest that while the host specificity of parasite sister lineages differ, larger clades may be relatively specialised or generalised. [ABSTRACT FROM AUTHOR]

Metchnikovellids are highly specialized hyperparasites, which infect and reproduce inside gregarines (Apicomplexa) inhabiting marine invertebrates. Their phylogenetic affiliation was under constant discussion until recently, when analysis of the first near-complete metchnikovellid genome, that of Amphiamblys sp. placed it in a basal position with respect to most Microsporidia. Microsporidia are a highly diversified lineage of extremely reduced parasites related to Rozellida (Rozellosporidia = Rozellomycota = Cryptomycota) within the Holomycota clade of Opisthokonta. By sequencing DNA from a single-isolated infected gregarine cell we obtained an almost complete genome of a second metchnikovellid species, and the first one of a taxonomically described and well-documented species, Metchnikovella incurvata. Our phylogenomic analyses show that, despite being considerably divergent from each other, M. incurvata forms a monophyletic group with Amphiamplys sp. and confirm that metchnikovellids are one of the deep branches of Microsporidia. Comparative genomic analysis demonstrates that, like most Microsporidia, metchnikovellids lack mitochondrial genes involved in energy transduction and are thus incapable of synthesizing their own ATP via mitochondrial oxidative phosphorylation. They also lack the horizontally acquired ATP transporters widespread in most Microsporidia. We hypothesize that a family of mitochondrial carrier proteins evolved to transport ATP from the host into the metchnikovellid cell. We observe the progressive reduction of genes involved in DNA repair pathways along the evolutionary path of Microsporidia, which might explain, at least partly, the extremely high evolutionary rate of the most derived species. Our data also suggest that genome reduction and acquisition of novel genes co-occurred during the adaptation of Microsporidia to their hosts. [ABSTRACT FROM AUTHOR]

Abstract Toxoplasma gondii (T. gondii) possesses a highly polarized secretory system, which efficiently assembles de novo micronemes (MIC) and rhoptries (ROP) during parasite replication. Pioneer works have studied the sorting motifs within MIC and ROP proteins, required for their trafficking towards their final destination. These studies led to the conclusion that protein processing and protein sorting are inter-dependent activities. More recent works have revealed the trafficking routes taken by the MIC and ROP proteins by examining the functions of the endo-exocytic compartments and identified key molecules involved in protein sorting and transport. These recent findings have suggested that T. gondii has repurposed the evolutionarily conserved regulators of the endosomal system to the secretory pathway. This review reports the pioneer as well as the most recent findings on the molecular mechanisms regulating apical organelle and dense granule biogenesis and portrays the parasite as a remarkable secretory machine that has efficiently remodeled its trafficking system to adapt to an intracellular lifestyle. [ABSTRACT FROM AUTHOR]

Parasitism is a common life strategy throughout the eukaryotic tree of life. Many devastating human pathogens, including the causative agents of malaria and toxoplasmosis, have evolved from a photosynthetic ancestor. However, how an organism transitions from a photosynthetic to a parasitic life history strategy remains mostly unknown. This is largely because few systems present the opportunity to make meaningful comparisons between a parasite and a close free-living relative. Parasites have independently evolved dozens of times throughout the Florideophyceae (Rhodophyta), and often infect close relatives. The accepted evolutionary paradigm proposes that red algal parasites arise by first infecting a close relative and over time diversify and infect more distantly related species. This provides a natural evolutionary gradient of relationships between hosts and parasites that share a photosynthetic common ancestor. Elegant microscopic work in the late 20th century provided detailed insight into the infection cycle of red algal parasites and the cellular interactions between parasites and their hosts. Those studies led to the use of molecular work to further investigate the origins of the parasite organelles and reveal the evolutionary relationships between hosts and their parasites. Here we synthesize the research detailing the infection methods and cellular interactions between red algal parasites and their hosts. We offer an alternative hypothesis to the current dogma of red algal parasite evolution and propose that red algae can adopt a parasitic life strategy through multiple evolutionary pathways, including direct infection of distant relatives. Furthermore, we highlight potential directions for future research to further evaluate parasite evolution in red algae.

Sulfadoxine-pyrimethamine (SP) is used as malaria chemoprophylaxis for pregnant women and children in Ghana. Plasmodium falciparum resistance to SP is linked to mutations in the dihydropteroate synthase gene (pfdhps), dihydrofolate reductase gene (pfdhfr) and amplification of GTP cyclohydrolase 1 (pfgch1) gene. The pfgch1 duplication is associated with pfdhfr L164, a crucial mutant for high level pyrimethamine resistance which is rare in Ghana. The presence of amplified pfgch1 in Ghanaian isolates could be an indicator of the evolution of the L164 mutant. This study therefore determined the pfgch1 copy number variations and SP resistance mutations in clinical isolates from Ghana. One hundred and ninety-two (192) blood samples collected from children aged ≤14 years with uncomplicated malaria in 2013–14 and 2015–16 were used. Quantitative real-time polymerase chain reaction (qRT-PCR) was used to detect the pfgch1 copy number and nested PCR-Sanger sequencing used to detect mutations in pfdhps and pfdhfr genes. Twelve parasites (6.3%) harbored double copies of the pfgch1 gene out of the 192 samples. Of the 12, 75% had the pfdhfr I51-R59-N108, 92% had the pfdhps G437 mutant, 8% had the pfdhps E540 and 67% had the SP resistance haplotype IRNG. No L164 was detected in samples with amplified pfgch1. The rare T108 mutant associated with cycloguanil resistance showed predominance (60%) over N108 in the 2015–16 isolates. The observation of parasites with increased copy number of pfgch1 gene is indicative of the future evolution of the rare quadruple pfdhfr mutant, I51-R59-N108-L164, in Ghanaian parasites. Mutant pfdhps isolates also had increased gch1 copy number suggestive that it may also facilitate sulphadoxine resistance. The selection of parasites with pfgch1 gene amplification will enhance the sustenance and persistence of parasites with SP resistance in the country. Policy makers need to begin the search for a replacement chemoprophylaxis drug for malaria vulnerable groups in Ghana. [ABSTRACT FROM AUTHOR]

Host populations are under continual selection by parasites due to reduced fitness of infected individuals relative to uninfected individuals. This should select for host resistance against parasites, and ample evidence from the laboratory and natural populations demonstrates that hosts can respond rapidly to parasitism by evolving resistance. Why then do parasites still exist? In part, this is due to ongoing arms races as parasites evolve counteradaptations to overcome resistance and to the presence of spatial structure and refuges. However, host–parasite coexistence can also be explained through loss of resistance over time due either to selection against costly resistance mechanisms or constant loss of resistance via reversion mutations. [ABSTRACT FROM AUTHOR]

As a result of great diversity in life histories and a large number of described species, taxonomic and phylogenetic uncertainty permeates the entire crustacean order of Isopoda. Large molecular datasets capable of providing sufficiently high phylogenetic resolution, such as mitochondrial genomes (mitogenomes), are needed to infer their evolutionary history with confidence, but isopod mitogenomes remain remarkably poorly represented in public databases. We sequenced the complete mitogenome of Cymothoa indica, a species belonging to a family from which no mitochondrial genome was sequenced yet, Cymothoidae. The mitogenome (circular, 14484 bp, A+T = 63.8%) is highly compact, appears to be missing two tRNA genes (trnI and trnE), and exhibits a unique gene order with a large number of rearrangements. High compactness and the existence of palindromes indicate that the mechanism behind these rearrangements might be associated with linearization events in its evolutionary history, similar to those proposed for isopods from the Armadillidium genus (Oniscidea). Isopods might present an important model system to study the proposed discontinuity in the dynamics of mitochondrial genomic architecture evolution. Phylogenetic analyses (Bayesian Inference and Maximum Likelihood) conducted using nucleotide sequences of all mitochondrial genes resolved Oniscidea and Cymothoida suborders as paraphyletic. Cymothoa indica was resolved as a sister group (basal) to all remaining isopods, which challenges the accepted isopod phylogeny, where Cymothoida are the most derived, and Phreatoicidea the most basal isopod group. There is growing evidence that Cymothoida suborder might be split into two evolutionary distant clades, with parasitic species being the most basal split in the Isopoda clade, but a much larger amount of molecular resources carrying a high phylogenetic resolution will be needed to infer the remarkably complex evolutionary history of this group of animals with confidence. [ABSTRACT FROM AUTHOR]

Although Plasmodium vivax is responsible for the majority of malaria infections outside Africa, little is known about its evolution and pathway to humans. Its closest genetic relative, P. vivax-like, was discovered in African great apes and is hypothesized to have given rise to P. vivax in humans. To unravel the evolutionary history and adaptation of P. vivax to different host environments, we generated using long- and short-read sequence technologies 2 new P. vivax-like reference genomes and 9 additional P. vivax-like genotypes. Analyses show that the genomes of P. vivax and P. vivax-like are highly similar and colinear within the core regions. Phylogenetic analyses clearly show that P. vivax-like parasites form a genetically distinct clade from P. vivax. Concerning the relative divergence dating, we show that the evolution of P. vivax in humans did not occur at the same time as the other agents of human malaria, thus suggesting that the transfer of Plasmodium parasites to humans happened several times independently over the history of the Homo genus. We further identify several key genes that exhibit signatures of positive selection exclusively in the human P. vivax parasites. Two of these genes have been identified to also be under positive selection in the other main human malaria agent, P. falciparum, thus suggesting their key role in the evolution of the ability of these parasites to infect humans or their anthropophilic vectors. Finally, we demonstrate that some gene families important for red blood cell (RBC) invasion (a key step of the life cycle of these parasites) have undergone lineage-specific evolution in the human parasite (e.g., reticulocyte-binding proteins [RBPs]). [ABSTRACT FROM AUTHOR]

Aphids are serious agricultural insect pests which exploit the phloem sap of host plants and thus transmit pathogens to their hosts. However, the degree to which aphid parsitism affects the fitness of the host plants is not well understood. The aphid, Macrosiphoniella yomogicola, parasitizes the mugwort Artemisia montana in Japan. During summer most mugworts carry aphids, but most aphid colonies die out after the budding of A. montana inflorescences in late summer. A few aphid colonies survive to late autumn, at which point sexuparae appear to later lay overwintering eggs after copulation. The death of the aphid colonies seems to be caused by biochemical changes in the phloem sap in the host plant coincident with the budding of inflorescences. The surviving aphid colonies may suppress the budding of inflorescences to allow persistence of their genetic line into the following year. Our investigations demonstrate that aphid parasitism did not affect host plant growth, but that it did significantly decrease the number of inflorescences and the average weight of floral buds. Our results indicate that aphid parasitism has a strong negative effect on the fitness of host plants. The manner in which the aphids suppress floral budding in their hosts is worth examining from the perspective of the evolution of aphid-plant interactions. [ABSTRACT FROM AUTHOR]

In the malaria parasite P. falciparum, drug resistance generally evolves first in low-transmission settings, such as Southeast Asia and South America. Resistance takes noticeably longer to appear in the high-transmission settings of sub-Saharan Africa, although it may spread rapidly thereafter. Here, we test the hypothesis that competitive suppression of drug-resistant parasites by drug-sensitive parasites may inhibit evolution of resistance in high-transmission settings, where mixed-strain infections are common. We employ a cross-scale model, which simulates within-host (infection) dynamics and between-host (transmission) dynamics of sensitive and resistant parasites for a population of humans and mosquitoes. Using this model, we examine the effects of transmission intensity, selection pressure, fitness costs of resistance, and cross-reactivity between strains on the establishment and spread of resistant parasites. We find that resistant parasites, introduced into the population at a low frequency, are more likely to go extinct in high-transmission settings, where drug-sensitive competitors and high levels of acquired immunity reduce the absolute fitness of the resistant parasites. Under strong selection from antimalarial drug use, however, resistance spreads faster in high-transmission settings than low-transmission ones. These contrasting results highlight the distinction between establishment and spread of resistance and suggest that the former but not the latter may be inhibited in high-transmission settings. Our results suggest that within-host competition is a key factor shaping the evolution of drug resistance in P. falciparum. [ABSTRACT FROM AUTHOR]

Wildlife parasitology is a highly diverse area of research encompassing many fields including taxonomy, ecology, pathology and epidemiology, and with participants from extremely disparate scientific fields. In addition, the organisms studied are highly dissimilar, ranging from platyhelminths, nematodes and acanthocephalans to insects, arachnids, crustaceans and protists. This review of the parasites of wildlife in Australia highlights the advances made to date, focussing on the work, interests and major findings of researchers over the years and identifies current significant gaps that exist in our understanding. The review is divided into three sections covering protist, helminth and arthropod parasites. The challenge to document the diversity of parasites in Australia continues at a traditional level but the advent of molecular methods has heightened the significance of this issue. Modern methods are providing an avenue for major advances in documenting and restructuring the phylogeny of protistan parasites in particular, while facilitating the recognition of species complexes in helminth taxa previously defined by traditional morphological methods. The life cycles, ecology and general biology of most parasites of wildlife in Australia are extremely poorly understood. While the phylogenetic origins of the Australian vertebrate fauna are complex, so too are the likely origins of their parasites, which do not necessarily mirror those of their hosts. This aspect of parasite evolution is a continuing area for research in the case of helminths, but remains to be addressed for many other parasitic groups. Wildlife parasitology is a highly diverse area of research encompassing disparate scientific disciplines and practitioners investigating highly dissimilar organisms. This review highlights advances made to date and identifies current significant gaps which exist in our understanding. Modern molecular methods are providing major advances in documenting and re-structuring the phylogeny of parasitic groups and facilitating recognition of species complexes in taxa previously defined by traditional morphological methods. Photo courtesy of Ian Beveridge, Australian Society for Parasitology and Lee Skerratt. [ABSTRACT FROM AUTHOR]

Predators often cause prey to adopt defensive strategies that reduce predation risk. The ‘ecology of fear’ examines these trait changes and their consequences. Similarly, parasites can cause hosts to adopt defensive strategies that reduce infection risk. However the ecological and evolutionary consequences of these behaviors (the ‘ecology of disgust’) are seldom considered. Here we identify direct and indirect effects of parasite avoidance on hosts and parasites, and examine differences between predators and parasites in terms of cost, detectability, and aggregation. We suggest that the nonconsumptive effects of parasites might overshadow their consumptive effects, as has been shown for predators. We emphasize the value of uniting predator–prey and parasite–host theory under a general consumer–resource framework. [ABSTRACT FROM AUTHOR]

Santalales is a large order, with over 2200 species, most of which are root or aerial (stem) hemiparasites. In this study, we report the newly assembled chloroplast genome of Dendrotrophe varians (140,666 bp) in the family Amphorogynaceae and the cp genomes of Helixanthera parasitica (124,881 bp) and Macrosolen cochinchinensis (122,986 bp), both in the family Loranthaceae. We compared the cp genomes of 11 Santalales including eight currently available cp genomes. Santalales cp genomes are slightly or not reduced in size (119–147 kb), similar to other hemiparasitic species, when compared with typical angiosperm cp genomes (120–170 kb). In a phylogeny examining gene content, the NADH dehydrogenase gene group is the only one among eight functional gene groups that lost complete functionally in all examined Santalales. This supports the idea that the functional loss of ndh genes is the initial stage in the evolution of the plastome of parasitic plants, but the loss has occurred independently multiple times in angiosperms, while they are not found in some parasites. This suggests that the functional loss of ndh genes is not essential for the transition from autotroph to parasite. We additionally examined the correlation between gene content and type of parasitism (obligate/facultative and stem/root parasites) of all hemiparasitic species in which cp genomes have been reported to date. Correlation was not found in any types of parasitism. [ABSTRACT FROM AUTHOR]

Comparisons of host and parasite phylogenies often show varying degrees of phylogenetic congruence. However, few studies have rigorously explored the factors driving this variation. Multiple factors such as host or parasite morphology may govern the degree of phylogenetic congruence. An ideal analysis for understanding the factors correlated with congruence would focus on a diverse host–parasite system for increased variation and statistical power. In this study, we focused on the Brueelia -complex, a diverse and widespread group of feather lice that primarily parasitise songbirds. We generated a molecular phylogeny of the lice and compared this tree with a phylogeny of their avian hosts. We also tested for the contribution of each host–parasite association to the overall congruence. The two trees overall were significantly congruent, but the contribution of individual associations to this congruence varied. To understand this variation, we developed a novel approach to test whether host, parasite or biogeographic factors were statistically associated with patterns of congruence. Both host plumage dimorphism and parasite ecomorphology were associated with patterns of congruence, whereas host body size, other plumage traits and biogeography were not. Our results lay the framework for future studies to further elucidate how these factors influence the process of host–parasite coevolution. [ABSTRACT FROM AUTHOR]

Abstract: Seed (egg) banking is a common bet‐hedging strategy maximizing the fitness of organisms facing environmental unpredictability by the delayed emergence of offspring. Yet, this condition often requires fast and drastic stochastic shifts between good and bad years. We hypothesize that the host seed banking strategy can evolve in response to coevolution with parasites because the coevolutionary cycles promote a gradually changing environment over longer times than seed persistence. We study the evolution of host germination fraction as a quantitative trait using both pairwise competition and multiple mutant competition methods, while the germination locus can be genetically linked or unlinked with the host locus under coevolution. In a gene‐for‐gene model of coevolution, hosts evolve a seed bank strategy under unstable coevolutionary cycles promoted by moderate to high costs of resistance or strong disease severity. Moreover, when assuming genetic linkage between coevolving and germination loci, the resistant genotype always evolves seed banking in contrast to susceptible hosts. Under a matching‐allele interaction, both hosts’ genotypes exhibit the same seed banking strategy irrespective of the genetic linkage between loci. We suggest host–parasite coevolution as an additional hypothesis for the evolution of seed banking as a temporal bet‐hedging strategy. [ABSTRACT FROM AUTHOR]

A challenge in studying diverse multi-copy gene families is deciphering distinct functional types within immense sequence variation. Functional changes can in some cases be tracked through the evolutionary history of a gene family; however phylogenetic approaches are not possible in cases where gene families diversify primarily by recombination. We take a network theoretical approach to functionally classify the highly recombining var antigenic gene family of the malaria parasite Plasmodium falciparum. We sample var DBLα sequence types from a local population in Ghana, and classify 9,276 of these variants into just 48 functional types. Our approach is to first decompose each sequence type into its constituent, recombining parts; we then use a stochastic block model to identify functional groups among the parts; finally, we classify the sequence types based on which functional groups they contain. This method for functional classification does not rely on an inferred phylogenetic history, nor does it rely on inferring function based on conserved sequence features. Instead, it infers functional similarity among recombining parts based on the sharing of similar co-occurrence interactions with other parts. This method can therefore group sequences that have undetectable sequence homology or even distinct origination. Describing these 48 var functional types allows us to simplify the antigenic diversity within our dataset by over two orders of magnitude. We consider how the var functional types are distributed in isolates, and find a nonrandom pattern reflecting that common var functional types are non-randomly distinct from one another in terms of their functional composition. The coarse-graining of var gene diversity into biologically meaningful functional groups has important implications for understanding the disease ecology and evolution of this system, as well as for designing effective epidemiological monitoring and intervention. [ABSTRACT FROM AUTHOR]