A hitchhiker’s guide to parasite transmission: The phoretic behaviour of feather lice

First report of the morphological and molecular characterization of Pseudolynchia canariensis (Diptera: Hippoboscidae) from Al-Baha region, Saudi Arabia

This study aims to study the morphological and molecular characterization of (Pseudolynchia canariensis; Macquart, 1839)in the Al-Baha region of Saudi Arabia. Ninety-four pigeons were obtained from traditional pigeon breeding farms of the Al-Baha region, and fly samples were collected. Taxonomic keys were used to define the morphology of flies, whereas molecular characteristics were identified based on cytochrome c oxidase subunit 1. The rate of Pseudolynchia canariensis infestation in the examined pigeons was 44.5%. The genetic sequences of the fly samples were deposited in GenBank (accession number OQ073507). The match rate between the fly samples from the present study and those previously recorded in GenBank (accession numbers: EF531220, OM073981, and MW853922) displayed 99.66%. This study demonstrates that Pseudolynchia canariensis is common in the Al-Baha region; thus, further studies are required to detect other species from the same genus and their geographical distribution.

Parasite escape mechanisms drive morphological diversification in avian lice

Organisms that have repeatedly evolved similar morphologies owing to the same selective pressures provide excellent cases in which to examine specific morphological changes and their relevance to the ecology and evolution of taxa. Hosts of permanent parasites act as an independent evolutionary experiment, as parasites on these hosts are thought to be undergoing similar selective pressures. Parasitic feather lice have repeatedly diversified into convergent ecomorphs in different microhabitats on their avian hosts. We quantified specific morphological characters to determine (i) which traits are associated with each ecomorph, (ii) the quantitative differences between these ecomorphs, and (iii) if there is evidence of displacement among co-occurring lice as might be expected under louse-louse competition on the host. We used nano-computed tomography scan data of 89 specimens, belonging to four repeatedly evolved ecomorphs, to examine their mandibular muscle volume, limb length and three-dimensional head shape data. Here, we find evidence that lice repeatedly evolve similar morphologies as a mechanism to escape host defences, but also diverge into different ecomorphs related to the way they escape these defences. Lice that co-occur with other genera on a host exhibit greater morphological divergence, indicating a potential role of competition in evolutionary divergence.

Distribution of phoretic mites and lice in Pseudolynchia canariensis living on pigeons and the relationship with seasonality, carrier sex, plumage coloration and age of definitive hosts

Among the parasites, some groups that have a limited capacity for locomotion, such as mites and lice, the transmission is challenging to win. These ectoparasites disperse through direct contact between hosts or, in some cases, through phoresy. However, these processes are not well-documented in detail because they are difficult to observe and quantify. In the present study, the patterns of distribution of skin mites and phoretic lice on hippoboscid louse fly Pseudolynchia canariensis sampled from Columba livia were evaluated. The analyzed pigeons were juveniles and adults, with three distinct plumage colors: blue checker, spread, or wild type, and were caught over 24 months. A total of 1,381 hippoboscid flies were collected on 377 hosts. The plumage color did not influence the infestation patterns of louse flies on juvenile and adult pigeons, nor did it influence the infestation patterns of skin mites and phoretic lice on the hippoboscid flies. However, the environmental temperature was directly related to higher prevalence, mean infestation intensity, and phoretic species richness on P. canariensis during the hottest seasons. Furthermore, a higher abundance of phoretic mite eggs, including embryonated eggs, was observed in females of P. canariensis in all seasons.

Prevalence and diversity of parasitic bird lice (Insecta: Psocodea) in northeast Arkansas

Many groups of parasites lack basic information on biodiversity and host associations, which poses challenges for conservation and understanding the ecological relationships between hosts and their parasites. This gap in knowledge is particularly relevant for parasitic species with obscure lifestyles. Ectoparasitc bird lice (Insecta: Psocodea: Phthiraptera) are a group of parasites that has received a relatively substantial research focus, yet patterns of bird-louse relationships and louse diversity remain understudied in many geographic regions, including in parts of the southeastern United States. In this study, we assessed the diversity, prevalence, abundance, and intensity of lice from live and salvaged birds in northeastern Arkansas. We also focused on the frequency of co-occurrence of lice and symbiotic feather mites. Finally, we used nuclear and mitochondrial genes to assess the phylogenic relationships among the most common genera of lice in our sample. We found a total louse prevalence of 10.57% with the highest prevalence on the Passeriformes families Turdidae, Passerellidae, and Parulidae. We also found the louse genera Myrsidea and Brueelia to be the most prevalent and abundant in our sample. Additionally, we reported several novel associations among well-studied bird species. We also found that louse phylogenic patterns tend to reflect host taxonomy and/or ecology. Overall, our results provide important insight into the biodiversity, community structure, and host interactions of parasitic lice from North American birds.

Dispersal-Limited Symbionts Exhibit Unexpectedly Wide Variation in Host Specificity

A fundamental aspect of symbiotic relationships is host specificity, ranging from extreme specialists associated with only a single host species to generalists associated with many different species. Although symbionts with limited dispersal capabilities are expected to be host specialists, some are able to associate with multiple hosts. Understanding the micro- and macro-evolutionary causes of variations in host specificity is often hindered by sampling biases and the limited power of traditional evolutionary markers. Here, we studied feather mites to address the barriers associated with estimates of host specificity for dispersal-limited symbionts. We sampled feather mites (Proctophyllodidae) from a nearly comprehensive set of North American breeding warblers (Parulidae) to study mite phylogenetic relationships and host-symbiont codiversification. We used pooled-sequencing (Pool-Seq) and short-read Illumina technology to interpret results derived from a traditional barcoding gene (cytochrome c oxidase subunit 1) versus 11 protein-coding mitochondrial genes using concatenated and multispecies coalescent approaches. Despite the statistically significant congruence between mite and host phylogenies, mite-host specificity varies widely, and host switching is common regardless of the genetic marker resolution (i.e., barcode vs. multilocus). However, the multilocus approach was more effective than the single barcode in detecting the presence of a heterogeneous Pool-Seq sample. These results suggest that presumed symbiont dispersal capabilities are not always strong indicators of host specificity or of historical host-symbiont coevolutionary events. A comprehensive sampling at fine phylogenetic scales may help to better elucidate the microevolutionary filters that impact macroevolutionary processes regulating symbioses, particularly for dispersal-limited symbionts. [Codiversification; cophylogenetics; feather mites; host switching; pooled sequencing; species delineation; symbiosis, warblers.].

PHYLOGENETIC RELATIONSHIPS OF GUIMARAESIELLA AND PRICEIELLA (PHTHIRAPTERA: ISCHNOCERA) FROM BABBLERS AND NON-BABBLERS (PASSERIFORMES)

Babblers (Passeriformes: Leiothrichidae, Pellorneidae, Timaliidae) are parasitized by more genera of lice of the Brueelia complex than any other group of songbirds. However, the relationships of these louse groups are poorly known. We here try to resolve the relationships between Guimaraesiella (Guimaraesiella), Guimaraesiella (Cicchinella), and their putative sister group Priceiella by using mitochondrial cytochrome c subunit 1 (COI), 12S, and 16S sequences. Our data indicate that G. (Cicchinella) forms a monophyletic group of lice from babblers, but the relationship between G. (Guimaraesiella), G. (Cicchinella), and Priceiella could not be resolved. Moreover, the position of the third lineage of babbler-specific lice, containing only the aberrant species Guimaraesiella montisodalis, is unresolved. Morphologically, this species is different from all other Guimaraesiella in several characters and may represent a distinct lineage. We present some data indicating that (1) the Nanling Mountain range may be a biogeographical barrier to chewing lice and (2) host participation in mixed-species feeding flocks may influence host associations in Brueelia-complex chewing lice.

REVIEW OF THE DAUER HYPOTHESIS: WHAT NON-PARASITIC SPECIES CAN TELL US ABOUT THE EVOLUTION OF PARASITISM

Parasitic lineages have acquired suites of new traits compared to their nearest free-living relatives. When and why did these traits arise? We can envision lineages evolving through multiple stable intermediate steps such as a series of increasingly exploitative species interactions. This view allows us to use non-parasitic species that approximate those intermediate steps to uncover the timing and original function of parasitic traits, knowledge critical to understanding the evolution of parasitism. The dauer hypothesis proposes that free-living nematode lineages evolved into parasites through two intermediate steps, phoresy and necromeny. Here we delve into the proposed steps of the dauer hypothesis by collecting and organizing data from genetic, behavioral, and ecological studies in a range of nematode species. We argue that hypotheses on the evolution of parasites will be strengthened by complementing comparative genomic studies with ecological studies on non-parasites that approximate intermediate steps.

The interplay between host biogeography and phylogeny in structuring diversification of the feather louse genus Penenirmus

Parasite diversification is influenced by many of the same factors that affect speciation of free-living organisms, such as biogeographic barriers. However, the ecology and evolution of the host lineage also has a major impact on parasite speciation. Here we explore the interplay between biogeography and host-association on the pattern of diversification in a group of ectoparasitic lice (Insecta: Phthiraptera: Penenirmus) that feeds on the feathers of woodpeckers, barbets, and honeyguides (Piciformes) and some songbirds (Passeriformes). We use whole genome sequencing of 41 ingroup and 12 outgroup samples to develop a phylogenomic dataset of DNA sequences from a reference set of 2395 single copy ortholog genes, for a total of nearly four million aligned base positions. The phylogenetic trees resulting from both concatenated and gene-tree/species-tree coalescent analyses were nearly identical and highly supported. These trees recovered the genus Penenirmus as monophyletic and identified several major clades, which tended to be associated with one major host group. However, cophylogenetic analysis revealed that host-switching was a prominent process in the diversification of this group. This host-switching generally occurred within single major biogeographic regions. We did, however, find one case in which it appears that a rare dispersal event by a woodpecker lineage from North America to Africa allowed its associated louse to colonize a woodpecker in Africa, even though the woodpecker lineage from North America never became established there.

Systemic Control of Cutaneous Leishmaniasis Sand-Fly Vectors: Fipronil-Treated Rodent Bait Is Effective in Reducing Phlebotomus papatasi (Diptera: Psychodidae) Female Emergence Rate From Rodent Burrows

The strong dependency of some vectors on their host as a source of habitat can be viewed as a weak link in pathogen's transmission cycles using the vertebrate host as a 'Trojan horse' to deliver insecticides directly to the vector-host point of contact (hereafter 'systemic control'). This could, simultaneously, affect the survival of blood-feeding females and coprophagic larvae. Sand-flies, vectors of leishmaniasis worldwide, are often dependent on their bloodmeal host as a source of habitat and may therefore be good candidates for systemic control. In the present study, we field-tested this methodology by baiting Meriones crassus (Sundevall, 1842) (Rodentia:Muridea) with Fipronil-treated food pellets and evaluated its effect on reducing sand-fly emergence rate, in general, and of that of blood-fed females, in particular. We demonstrated 86% reduction in the abundance of female sand-flies that exit burrows of Fipronil-treated jirds, whereas male abundance was unaffected. Furthermore, whereas in control burrows 20% of the females were blood-fed, in treatment burrows no blood-fed females were detected. Sand-fly abundance outside the burrows was not affected by burrow treatment. This highlights the focal specificity of this method: affecting female sand-flies that feed on the reservoir host. This should result in the reduction of the pathogen transmission rate in the vicinity of the treated area by reducing the prevalence of leishmania-infected sand-fly females. These results hold promise for the potential of the systemic control approach in this system. Our next-step goal is to test this methodology at a large-scale cutaneous leishmaniasis control program.

Analysis of phoretic relation between chewing lice and hippoboscid flies of Columba livia

Phoresy is a biologically mechanical phenomena where an immobile organism hitches on a other mobile organism to translocate. This behaviour is not studied very well on the field level especially between two important parasites infesting the same host. Parasite/parasite interaction is rarely studied through most biological host-parasite systems. Here, we evaluated the phoretic relation between parasitic chewing lice and hippoboscid flies (Pseudolynchia canariensis) on rock pigeons. A total of 69 captivated rock pigeons, Columba livia, were examined for the parasitic chewing lice and hippoboscid flies in Giza Zoo and two local farms near Cairo, Egypt. Results indicated that there is a positive correlation between infestation of hippoboscid flies and chewing lice. Also, the analysis of louse/louse interaction using ANOVA indicated a significant difference between the three chewing louse species which were recorded on the rock pigeons with relatively high abundance of two species, Columbicola columbae and Campanulotes compar. The analysis of hippoboscid flies' abundance and its relation with chewing lice infestation indicate a significant increase of lice intensity in case of high infestation with the fly. The level of hygiene of nest may be inversely related to level of parasite infestation. This work forms a step in the process of understanding parasite/parasite and host/parasite interactions using two parasitic species with a characteristic phoretic behaviour in nature.

Insect ectoparasites from wild passerine birds in the Azores Islands

A total of 266 wild passerine birds (Passeriformes) representing eight species and nine subspecies from three islands of the Archipelago of the Azores were examined for ectoparasites. Two species of louse-flies Ornithomya avicularia and Ornithoica turdi (Diptera: Hippoboscidae), three species of fleas Ceratophyllus gallinae, Ceratophyllus sp. and Dasypsyllus gallinulae (Siphonaptera: Ceratophyllidae), and 11 species of chewing lice belonging to the genera Menacanthus, Myrsidea (Phthiraptera: Menoponidae), Ricinus (Phthiraptera: Ricinidae), Brueelia, Guimaraesiella, Philopterus, Sturnidoecus and Turdinirmus (Phthiraptera: Philopteridae) were recorded. At least one species of ectoparasite was found on 114 birds of six species. Guimaraesiella tovornikae and Myrsidea sylviae from Sylvia atricapilla are redescribed. Records of Ceratophyllus sp. and Sturnidoecus sp. from Turdus merula represent new parasite-host associations. Phoresy of Guimaraesiella amsel on Ornithoica turdi was also found. Parasitological parameters such as prevalence, intensity and abundance and geographic distribution of recorded ectoparasites are provided.

Arthropod parasites of Antarctic and Subantarctic birds and pinnipeds: A review of host-parasite associations

Due to its cold and dry climate and scarcity of ice-free land, Antarctica has one of the most extreme environments on our planet. To survive in the Antarctic region, parasitic arthropods must either remain closely associated with their hosts throughout the entire life cycle or develop physiological adaptations to survive in the terrestrial habitat while their hosts are away foraging at sea or overwintering at lower latitudes. Forty-eight species of birds and seven species of pinnipeds breed in the Antarctic region, with 158 species/subspecies of parasitic arthropods recorded thus far, comprising: sucking lice (Echinophthiriidae), chewing lice (Menoponidae, Philopteridae), fleas (Ceratophyllidae, Pygiopsyllidae, Rhopalopsyllidae), pentastomes (Reighardiidae), hard ticks (Ixodidae), nest-associated haematophagous mites (Laelapidae), nasal mites (Halarachnidae, Rhinonyssidae) and feather mites (Alloptidae, Avenzoariidae, Xolalgidae, Freyanidae). In this review, we provide an updated compilation of the available information on the host-parasite associations of arthropods infesting birds and pinnipeds in the Antarctic region, and discuss some over-arching ecological patterns and gaps of knowledge.

Comparing rates of introgression in parasitic feather lice with differing dispersal capabilities

Organisms vary in their dispersal abilities, and these differences can have important biological consequences, such as impacting the likelihood of hybridization events. However, there is still much to learn about the factors influencing hybridization, and specifically how dispersal ability affects the opportunities for hybridization. Here, using the ecological replicate system of dove wing and body lice (Insecta: Phthiraptera), we show that species with higher dispersal abilities exhibited increased genomic signatures of introgression. Specifically, we found a higher proportion of introgressed genomic reads and more reticulated phylogenetic networks in wing lice, the louse group with higher dispersal abilities. Our results are consistent with the hypothesis that differences in dispersal ability might drive the extent of introgression through hybridization.

Jorge Doña, Andrew Sweet and Kevin Johnson find that dove lice species with higher dispersal abilities have stronger genomic signatures of introgression. By using sequence data from multiple species of both wing and body lice from the same species of hosts, the authors are able to control for nearly all factors besides dispersal ability, demonstrating the power of this study system.

Phoresy in animals: review and synthesis of a common but understudied mode of dispersal

Phoresy is a type of interaction in which one species, the phoront, uses another species, the dispersal host, for transportation to new habitats or resources. Despite being a widespread behaviour, little is known about the ecology and evolution of phoresy. Our goal is to provide a comprehensive review of phoretic dispersal in animals and to bring renewed attention to this subject. We surveyed literature published between 1900 and 2020 to understand the extent of known higher-level taxonomic diversity (phyla, classes, and orders) and functional aspects of animals that use phoretic dispersal. Species dispersing phoretically have been observed in at least 13 animal phyla, 25 classes, and 60 orders. The majority of known phoronts are arthropods (Phylum Euarthropoda) in terrestrial habitats, but phoronts also occur in freshwater and marine environments. Marine phoronts may be severely under-represented in the literature due to the relative difficulty of studying these systems. Phoronts are generally small with low mobility and use habitats or resources that are ephemeral and/or widely dispersed. Many phoronts are also parasites. In general, animals that engage in phoresy use a wide variety of morphological and behavioural traits for locating, attaching to, and detaching from dispersal hosts, but the exact mechanisms behind these activities are largely unknown. In addition to diversity, we discuss the evolution of phoresy including the long-standing idea that it can be a precursor to parasitism and other forms of symbioses. Finally, we suggest several areas of future research to improve our understanding of phoresy and its ecological and evolutionary significance.

Lousy grouse: Comparing evolutionary patterns in Alaska galliform lice to understand host evolution and host-parasite interactions

Understanding both sides of host-parasite relationships can provide more complete insights into host and parasite biology in natural systems. For example, phylogenetic and population genetic comparisons between a group of hosts and their closely associated parasites can reveal patterns of host dispersal, interspecies interactions, and population structure that might not be evident from host data alone. These comparisons are also useful for understanding factors that drive host-parasite coevolutionary patterns (e.g., codivergence or host switching) over different periods of time. However, few studies have compared the evolutionary histories between multiple groups of parasites from the same group of hosts at a regional geographic scale. Here, we used genomic data to compare phylogenomic and population genomic patterns of Alaska ptarmigan and grouse species (Aves: Tetraoninae) and two genera of their associated feather lice: Lagopoecus and Goniodes. We used whole-genome sequencing to obtain hundreds of genes and thousands of single-nucleotide polymorphisms (SNPs) for the lice and double-digest restriction-associated DNA sequences to obtain SNPs from Alaska populations of two species of ptarmigan. We found that both genera of lice have some codivergence with their galliform hosts, but these relationships are primarily characterized by host switching and phylogenetic incongruence. Population structure was also uncorrelated between the hosts and lice. These patterns suggest that grouse, and ptarmigan in particular, share habitats and have likely had historical and ongoing dispersal within Alaska. However, the two genera of lice also have sufficient dissimilarities in the relationships with their hosts to suggest there are other factors, such as differences in louse dispersal ability, that shape the evolutionary patterns with their hosts.

High prevalence and genetic diversity of Haemoproteus columbae (Haemosporida: Haemoproteidae) in feral pigeons Columba livia in Cape Town, South Africa

In this study, we explore blood parasite prevalence, infection intensity, and co-infection levels in an urban population of feral pigeons Columba livia in Cape Town. We analyze the effect of blood parasites on host body condition and the association between melanin expression in the host's plumage and parasite infection intensity and co-infection levels. Relating to the haemosporidian parasite itself, we study their genetic diversity by means of DNA barcoding (cytochrome b) and show the geographic and host distribution of related parasite lineages in pigeons worldwide. Blood from 195 C. livia individuals was collected from April to June 2018. Morphometric measurements and plumage melanism were recorded from every captured bird. Haemosporidian prevalence and infection intensity were determined by screening blood smears and parasite lineages by DNA sequencing. Prevalence of Haemoproteus spp. was high at 96.9%. The body condition of the hosts was negatively associated with infection intensity. However, infection intensity was unrelated to plumage melanism. The cytochrome b sequences revealed the presence of four Haemoproteus lineages in our population of pigeons, which show high levels of co-occurrence within individual birds. Three lineages (HAECOL1, COLIV03, COQUI05) belong to Haemoproteus columbae and differ only by 0.1% to 0.8% in the cytochrome b gene. Another lineage (COLIV06) differs by 8.3% from the latter ones and is not linked to a morphospecies, yet. No parasites of the genera Leucocytozoon and Plasmodium were detected.

Defining host range: host-parasite compatibility during the non-infective phase of the parasite also matters

Host range and parasite specificity determine key epidemiological, ecological and evolutionary aspects of host-parasite interactions. Parasites are usually classified as generalists or specialists based on the number of hosts they feed on. Yet, the requirements of the various stages of a parasite may influence the suitability of a given host species. Here, we investigate the generalist nature of three common ectoparasites (the dipteran Carnus hemapterus and two species of louse flies, Pseudolynchia canariensis and Ornithophila metallica), exploiting two avian host species (the European roller Coracias garrulus and the Rock pigeon Columba livia), that frequently occupy the same breeding sites. We explore the prevalence and abundance of both the infective and the puparial stages of the ectoparasites in both host species. Strong preferences of Pseudolynchia canariensis for pigeons and of Carnus hemapterus for rollers were found. Moderate prevalence of Ornithophila metallica was found in rollers but this louse fly avoided pigeons. In some cases, the infestation patterns observed for imagoes and puparia were consistent whereas in other cases host preferences inferred from imagoes differed from the ones suggested by puparia. We propose that the adult stages of these ectoparasites are more specialist than reported and that the requirements of non-infective stages can restrict the effective host range of some parasites.

Phoretic dispersal influences parasite population genetic structure

Dispersal is a fundamental component of the life history of most species. Dispersal influences fitness, population dynamics, gene flow, genetic drift and population genetic structure. Even small differences in dispersal can alter ecological interactions and trigger an evolutionary cascade. Linking such ecological processes with evolutionary patterns is difficult, but can be carried out in the proper comparative context. Here, we investigate how differences in phoretic dispersal influence the population genetic structure of two different parasites of the same host species. We focus on two species of host-specific feather lice (Phthiraptera: Ischnocera) that co-occur on feral rock pigeons (Columba livia). Although these lice are ecologically very similar, "wing lice" (Columbicola columbae) disperse phoretically by "hitchhiking" on pigeon flies (Diptera: Hippoboscidae), while "body lice" (Campanulotes compar) do not. Differences in the phoretic dispersal of these species are thought to underlie observed differences in host specificity, as well as the degree of host-parasite cospeciation. These ecological and macroevolutionary patterns suggest that body lice should exhibit more genetic differentiation than wing lice. We tested this prediction among lice on individual birds and among lice on birds from three pigeon flocks. We found higher levels of genetic differentiation in body lice compared to wing lice at two spatial scales. Our results indicate that differences in phoretic dispersal can explain microevolutionary differences in population genetic structure and are consistent with macroevolutionary differences in the degree of host-parasite cospeciation.

How do seasonality and host traits influence the distribution patterns of parasites on juveniles and adults of Columba livia?

Parasites may influence host fitness and consequently exert a selective pressure on distinct phenotypes of the host population. This pressure can result in an evolutionary response, maintaining only individuals with certain traits in the population. The present study was aimed at identifying the morphological characteristics of juveniles and adults of Columba livia that may influence the distribution patterns of lice, Pseudolynchia canariensis and Haemoproteus columbae and how the populations of these parasites vary throughout the seasons of the year. Between July 2012 and July 2014, 377 specimens of C. livia were captured. We observed a significant increase in the mean intensities of infestation by pigeon flies and lice, as well as in species richness of ectoparasites during the warmest seasons, suggesting a reproductive synchrony between ectoparasites and host species. Bill length, body mass, and body length did not affect the infestation levels of ectoparasites on adults and juveniles of C. livia with three distinct plumage colors. In juveniles, plumage color affected only the mean intensity of infestation by lice, with Spread individuals as the most infested. This indicates that melanin in feathers was not an effective barrier against ectoparasites.

Integrating phylogenomic and population genomic patterns in avian lice provides a more complete picture of parasite evolution

Parasite diversity accounts for most of the biodiversity on earth, and is shaped by many processes (e.g., cospeciation, host switching). To identify the effects of the processes that shape parasite diversity, it is ideal to incorporate both deep (phylogenetic) and shallow (population) perspectives. To this end, we developed a novel workflow to obtain phylogenetic and population genetic data from whole genome sequences of body lice parasitizing New World ground-doves. Phylogenies from these data showed consistent, highly resolved species-level relationships for the lice. By comparing the louse and ground-dove phylogenies, we found that over long-term evolutionary scales their phylogenies were largely congruent. Many louse lineages (both species and populations) also demonstrated high host-specificity, suggesting ground-dove divergence is a primary driver of their parasites' diversity. However, the few louse taxa that are generalists are structured according to biogeography at the population level. This suggests dispersal among sympatric hosts has some effect on body louse diversity, but over deeper time scales the parasites eventually sort according to host species. Overall, our results demonstrate that multiple factors explain the patterns of diversity in this group of parasites, and that the effects of these factors can vary over different evolutionary scales. The integrative approach we employed was crucial for uncovering these patterns, and should be broadly applicable to other studies.

Pigeonetics takes flight: Evolution, development, and genetics of intraspecific variation

Intensive artificial selection over thousands of years has produced hundreds of varieties of domestic pigeon. As Charles Darwin observed, the morphological differences among breeds can rise to the magnitude of variation typically observed among different species. Nevertheless, different pigeon varieties are interfertile, thereby enabling forward genetic and genomic approaches to identify genes that underlie derived traits. Building on classical genetic studies of pigeon variation, recent molecular investigations find a spectrum of coding and regulatory alleles controlling derived traits, including plumage color, feather growth polarity, and limb identity. Developmental and genetic analyses of pigeons are revealing the molecular basis of variation in a classic example of extreme intraspecific diversity, and have the potential to nominate genes that control variation among other birds and vertebrates in general.

Niche Partitioning of Feather Mites within a Seabird Host, Calonectris borealis

According to classic niche theory, species can coexist in heterogeneous environments by reducing interspecific competition via niche partitioning, e.g. trophic or spatial partitioning. However, support for the role of competition on niche partitioning remains controversial. Here, we tested for spatial and trophic partitioning in feather mites, a diverse and abundant group of arthropods. We focused on the two dominant mite species, Microspalax brevipes and Zachvatkinia ovata, inhabiting flight feathers of the Cory’s shearwater, Calonectris borealis. We performed mite counts across and within primary and tail feathers on free-living shearwaters breeding on an oceanic island (Gran Canaria, Canary Islands). We then investigated trophic relationships between the two mite species and the host using stable isotope analyses of carbon and nitrogen on mite tissues and potential host food sources. The distribution of the two mite species showed clear spatial segregation among feathers; M. brevipes showed high preference for the central wing primary feathers, whereas Z. ovata was restricted to the two outermost primaries. Morphological differences between M. brevipes and Z. ovata support an adaptive basis for the spatial segregation of the two mite species. However, the two mites overlap in some central primaries and statistical modeling showed that Z. ovata tends to outcompete M. brevipes. Isotopic analyses indicated similar isotopic values for the two mite species and a strong correlation in carbon signatures between mites inhabiting the same individual host suggesting that diet is mainly based on shared host-associated resources. Among the four candidate tissues examined (blood, feather remains, skin remains and preen gland oil), we conclude that the diet is most likely dominated by preen gland oil, while the contribution of exogenous material to mite diets is less marked. Our results indicate that ongoing competition for space and resources plays a central role in structuring feather mite communities. They also illustrate that symbiotic infracommunities are excellent model systems to study trophic ecology, and can improve our understanding of mechanisms of niche differentiation and species coexistence.

Effect of body size on the abundance of ectoparasitic mites on the wild rodent Oligoryzomys nigripes

The abundance of parasites on a host can be affected by several factors; in this study, we investigated the influence of sex and body size of the host rodent Oligoryzomys nigripes on the abundance of ectoparasitic mites (Acari: Mesostigmata). The generalized linear model indicated that body size (indicative of age) of the host rodent O. nigripes significantly contributed to the variation in the abundance of mites on host rodents at the Experimental Station of Itirapina. This trend of increased parasitism on hosts with larger body sizes may be linked to the fact that larger individuals are able to support the coexistence of a larger number of parasites, and being more mobile, are more exposed to infection by parasites.

Host generalists and specialists emerging side by side: an analysis of evolutionary patterns in the cosmopolitan chewing louse genus Menacanthus

Parasites with wide host spectra provide opportunities to study the ecological parameters of speciation, as well as the process of the evolution of host specificity. The speciose and cosmopolitan louse genus Menacanthus comprises both multi-host and specialised species, allowing exploration of the ecological and historical factors affecting the evolution of parasites using a comparative approach. We used phylogenetic analysis to reconstruct evolutionary relationships in 14 species of Menacanthus based on the sequences of one mitochondrial and one nuclear gene. The results allowed us to validate species identification based on morphology, as well as to explore host distribution by assumed generalist and specialist species. Our analyses confirmed a narrow host use for several species, however in some cases, the supposed host specialists had a wider host spectrum than anticipated. In one case a host generalist (Menacanthus eurysternus) was clustered terminally on a clade almost exclusively containing host specialists. Such a clade topology indicates that the process of host specialisation may not be irreversible in parasite evolution. Finally, we compared patterns of population genetic structure, geographic distribution and host spectra between two selected species, M. eurysternus and Menacanthus camelinus, using haplotype networks. Menacanthus camelinus showed limited geographical distribution in combination with monoxenous host use, whereas M. eurysternus showed a global distribution and lack of host specificity. It is suggested that frequent host switching maintains gene flow between M. eurysternus populations on unrelated hosts in local populations. However, gene flow between geographically distant localities was restricted, suggesting that geography rather than host-specificity is the main factor defining the global genetic diversity of M. eurysternus.

Campanulotes compar (Burmeister, 1838) (Phthiraptera: Ischnocera) in chickens (Gallus gallus domesticus) from Rio Grande do Norte State, Brazil. The reemergence of an ectoparasite?

The importance of ectoparasites in the transmission of pathogens, as well as the variability of species from one region to another, motivated this notification of the ectoparasite lice Campanulotes compar in range chickens (Gallus gallus domesticus L.) reared in an extensive system in the city of Apodi, Rio Grande do Norte state, in the Northeast region of Brazil. The examined birds were infested with ten males and six females of C. compar. Thus, C. compar is recorded as parasitizing chickens in the state of Rio Grande do Norte after 77 years from its unique citation in the Southeast region of Brazil. We further discuss the possible risks of this finding.

Comparative host–parasite population genetic structures: obligate fly ectoparasites on Galapagos seabirds

Parasites often have shorter generation times and, in some cases, faster mutation rates than their hosts, which can lead to greater population differentiation in the parasite relative to the host. Here we present a population genetic study of two ectoparasitic flies, Olfersia spinifera and Olfersia aenescens compared with their respective bird hosts, great frigatebirds (Fregata minor) and Nazca boobies (Sula granti). Olfersia spinifera is the vector of a haemosporidian parasite, Haemoproteus iwa, which infects frigatebirds throughout their range. Interestingly, there is no genetic differentiation in the haemosporidian parasite across this range despite strong genetic differentiation between Galapagos frigatebirds and their non-Galapagos conspecifics. It is possible that the broad distribution of this one H. iwa lineage could be facilitated by movement of infected O. spinifera. Therefore, we predicted more gene flow in both fly species compared with the bird hosts. Mitochondrial DNA sequence data from three genes per species indicated that despite marked differences in the genetic structure of the bird hosts, gene flow was very high in both fly species. A likely explanation involves non-breeding movements of hosts, including movement of juveniles, and movement by adult birds whose breeding attempt has failed, although we cannot rule out the possibility that closely related host species may be involved.

Avian brood parasitism and ectoparasite richness-scale-dependent diversity interactions in a three-level host-parasite system

Brood parasitic birds, their foster species and their ectoparasites form a complex coevolving system composed of three hierarchical levels. However, effects of hosts' brood parasitic life-style on the evolution of their louse (Phthiraptera: Amblycera, Ischnocera) lineages have never been tested. We present two phylogenetic analyses of ectoparasite richness of brood parasitic clades. Our hypothesis was that brood parasitic life-style affects louse richness negatively across all avian clades due to the lack of vertical transmission routes. Then, narrowing our scope to brood parasitic cuckoos, we explored macroevolutionary factors responsible for the variability of their louse richness. Our results show that taxonomic richness of lice is lower on brood parasitic clades than on their nonparasitic sister clades. However, we found a positive covariation between the richness of cuckoos' Ischnoceran lice and the number of their foster species, possibly due to the complex and dynamic subpopulation structure of cuckoo species that utilize several host species. We documented diversity interactions across a three-level host parasite system and we found evidence that brood parasitism has opposing effects on louse richness at two slightly differing macroevolutionary scales, namely the species richness and the genera richness.

River barriers and cryptic biodiversity in an evolutionary museum

The Riverine Barriers Hypothesis (RBH) posits that tropical rivers can be effective barriers to gene flow, based on observations that range boundaries often coincide with river barriers. Over the last 160 years, the RBH has received attention from various perspectives, with a particular focus on vertebrates in the Amazon Basin. To our knowledge, no molecular assessment of the RBH has been conducted on birds in the Afrotropics, despite its rich avifauna and many Afrotropical bird species being widely distributed across numerous watersheds and basins. Here, we provide the first genetic evidence that an Afrotropical river has served as a barrier for birds and for their lice, based on four understory bird species collected from sites north and south of the Congo River. Our results indicate near-contemporaneous, Pleistocene lineage diversification across the Congo River in these species. Our results further indicate differing levels of genetic variation in bird lice; the extent of this variation appears linked to the life-history of both the host and the louse. Extensive cryptic diversity likely is being harbored in Afrotropical forests, in both understory birds and their lice. Therefore, these forests may not be "museums" of old lineages. Rather, substantial evolutionary diversification may have occurred in Afrotropical forests throughout the Pleistocene, supporting the Pleistocene Forest Refuge Hypothesis. Strong genetic variation in birds and their lice within a small part of the Congo Basin forest indicates that we may have grossly underestimated diversity in the Afrotropics, making these forests home of substantial biodiversity in need of conservation.

How effective is preening against mobile ectoparasites? An experimental test with pigeons and hippoboscid flies

Birds combat ectoparasites with many defences but the first line of defence is grooming behaviour, which includes preening with the bill and scratching with the feet. Preening has been shown to be very effective against ectoparasites. However, most tests have been with feather lice, which are relatively slow moving. Less is known about the effectiveness of preening as a defence against more mobile and evasive ectoparasites such as hippoboscid flies. Hippoboscids, which feed on blood, have direct effects on the host such asanaemia, as well as indirect effects as vectors of pathogens. Hence, effective defence against hippoboscid flies is important. We used captive Rock Pigeons (Columba livia) to test whether preening behaviour helps to control pigeon flies (Pseudolynchia canariensis). We found that pigeons responded to fly infestation by preening twice as much as pigeons without flies. Preening birds killed twice as many flies over the course of our week-long experiment as birds with impaired preening; however, preening did not kill all of the flies. We also tested the role of the bill overhang, which is critical for effective preening against feather lice, by experimentally removing the overhang and re-measuring the effectiveness of preening against flies. Birds without overhangs were as effective at controlling flies as were birds with overhangs. Overall, we found that preening is effective against mobile hippoboscid flies, yet it does not eliminate them. We discuss the potential impact of preening on the transmission dynamics of blood parasites vectored by hippoboscid flies.

Antennal lobe organization in the slender pigeon louse, Columbicola columbae (Phthiraptera: Ischnocera)

This study reports on the structure of the antennal lobe of the pigeon louse, Columbicola columbae. Anterograde staining of antennal receptor neurons revealed an antennal lobe with a few diffuse compartments, an organization distinct from the typical spheroidal glomerular structure found in the olfactory bulb of vertebrates and the antennal lobe of many other insects. This anatomical arrangement of neuronal input is somewhat reminiscent of the aglomerular antennal lobe previously reported in psyllids and aphids. As in psyllids, reports on the odor-mediated behavior of C. columbae suggest that the olfactory sense is important in these animals and indicates that a glomerular organization of the antennal lobe may not be necessary to subtend odor-mediated behaviors in all insects. The diffuse or aglomerular antennal lobe organization found in these two Paraneopteran insect orders might represent an independently evolved reduction due to similar ecological constraints.

Mapping the social network: tracking lice in a wild primate (Microcebus rufus) population to infer social contacts and vector potential

BACKGROUND

Studies of host-parasite interactions have the potential to provide insights into the ecology of both organisms involved. We monitored the movement of sucking lice (Lemurpediculus verruculosus), parasites that require direct host-host contact to be transferred, in their host population of wild mouse lemurs (Microcebus rufus). These lemurs live in the rainforests of Madagascar, are small (40 g), arboreal, nocturnal, solitary foraging primates for which data on population-wide interactions are difficult to obtain. We developed a simple, cost effective method exploiting the intimate relationship between louse and lemur, whereby individual lice were marked, without removal from their host, with an individualized code, and tracked throughout the lemur population. We then tested the hypotheses that 1) the frequency of louse transfers, and thus interactions, would decrease with increasing distance between paired individual lemurs; 2) due to host polygynandry, social interactions and hence louse transfers would increase during the onset of the breeding season; and 3) individual mouse lemurs would vary in their contributions to the spread of lice.

RESULTS

We show that louse transfers involved 43.75% of the studied lemur population, exclusively males. Louse transfers peaked during the breeding season, perhaps due to increased social interactions between lemurs. Although trap-based individual lemur ranging patterns are restricted, louse transfer rate does not correlate with the distance between lemur trapping locales, indicating wider host ranging behavior and a greater risk of rapid population-wide pathogen transmission than predicted by standard trapping data alone. Furthermore, relatively few lemur individuals contributed disproportionately to the rapid spread of lice throughout the population.

CONCLUSIONS

Using a simple method, we were able to visualize exchanges of lice in a population of cryptic wild primates. This method not only provided insight into the previously unseen parasite movement between lemurs, but also allowed us to infer social interactions between them. As lice are known pathogen vectors, our method also allowed us to identify the lemurs most likely to facilitate louse-mediated epidemics. Our approach demonstrates the potential to uncover otherwise inaccessible parasite-host, and host social interaction data in any trappable species parasitized by sucking lice.

Community interactions govern host-switching with implications for host-parasite coevolutionary history

Reciprocal selective effects between coevolving species are often influenced by interactions with the broader ecological community. Community-level interactions may also influence macroevolutionary patterns of coevolution, such as cospeciation, but this hypothesis has received little attention. We studied two groups of ecologically similar feather lice (Phthiraptera: Ischnocera) that differ in their patterns of association with a single group of hosts. The two groups, "body lice" and "wing lice," are both parasites of pigeons and doves (Columbiformes). Body lice are more host-specific and show greater population genetic structure than wing lice. The macroevolutionary history of body lice also parallels that of their columbiform hosts more closely than does the evolutionary history of wing lice. The closer association of body lice with hosts, compared with wing lice, can be explained if body lice are less capable of switching hosts than wing lice. Wing lice sometimes disperse phoretically on parasitic flies (Diptera: Hippoboscidae), but body lice seldom engage in this behavior. We tested the hypothesis that wing lice switch host species more often than body lice, and that the difference is governed by phoresis. Our results show that, where flies are present, wing lice switch to novel host species in sufficient numbers to establish viable populations on the new host. Body lice do not switch hosts, even where flies are present. Thus, differences in the coevolutionary history of wing and body lice can be explained by differences in host-switching, mediated by a member of the broader parasite community.

The evolution of host specificity in dove body lice

Objective:Conventional wisdom suggests that parasites evolve increased host specialization over time. Host specificity, which describes the number of host species parasitized, is one aspect of host specialization. Recent studies of vertebrate parasites indicate that highly host-specific parasite lineages are not, in fact, evolutionary dead ends; host generalists can evolve from host specialists.

Methods:Using phylogenetic reconstruction methods, we evaluate these patterns in the body lice (Insecta: Phthiraptera) of pigeons and doves, which are permanent ectoparasites that complete their entire life cycle on the body of the host.

Results:We find that species of body lice that parasitize more than one species of host (generalists) are invariably derived from lice parasitizing only one species of host (specialists). A previous study of the wing lice of pigeons and doves also found that generalists were derived from specialists, and that these changes were correlated with the presence of a potentially competing species of wing louse on the same host. For body lice we did not find such a correlation with competition. Instead, the evolution of host generalists in body lice was correlated with host ecology. When we compared body lice that parasitize terrestrial versus arboreal hosts, we found that the evolution of host generalists was associated with terrestrial hosts. In contrast, wing lice showed no correlation between the evolution of generalists and host ecology.

Conclusion:The correlation in body lice suggests that dispersal between host species may occur via the ground. This, in turn, suggests that body lice may fall to the ground more often than wing lice. To test this hypothesis, we conducted an experiment to compare the rate at which body and wing lice are dislodged from the bodies of preening pigeons. Interestingly, our results showed that body lice are dislodged four times more often than wing lice. Therefore, species of terrestrial doves are far more likely to encounter body lice than wing lice on the ground.

Competition promotes the evolution of host generalists in obligate parasites

Ecological theory traditionally predicts that interspecific competition selects for an increase in ecological specialization. Specialization, in turn, is often thought to be an evolutionary 'dead end,' with specialist lineages unlikely to evolve into generalist lineages. In host-parasite systems, this specialization can take the form of host specificity, with more specialized parasites using fewer hosts. We tested the hypothesis that specialists are evolutionarily more derived, and whether competition favours specialization, using the ectoparasitic feather lice of doves. Phylogenetic analyses revealed that complete host specificity is actually the ancestral condition, with generalists repeatedly evolving from specialist ancestors. These multiple origins of generalists are correlated with the presence of potentially competing species of the same genus. A competition experiment with captive doves and lice confirmed that congeneric species of lice do, in fact, have the potential to compete in ecological time. Taken together, these results suggest that interspecific competition can favour the evolution of host generalists, not specialists, over macroevolutionary time.