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Vertical transmission in feather mites: Insights into its adaptive value
Abstract and Figures
1. The consequences of symbiont transmission strategies are better understood than their adaptive causes.
2. Feather mites are permanent ectosymbionts of birds assumed to be transmitted mainly vertically from parents to offspring. The transmission of Proctophyllodes doleophyes G aud ( A stigmata, P roctophyllodidae) was studied in two E uropean populations of pied flycatchers, Ficedula hypoleuca P allas ( P asseriformes, M uscicapidae).
3. The vertical transmission of this mite species is demonstrated here with an acaricide experiment. This study also compared (for two distant populations during 4 years) patterns in reductions in mite intensity in adult birds, from egg incubation to chick‐rearing periods, with the predictions of three hypotheses on how host survival prospects and mite intraspecific competition might drive feather mites' transmission strategy.
4. The results are in agreement with previous studies and show that feather mites transmit massively from parents to chicks.
5. The magnitude of the transmission was closer to that predicted by the hypothesis based on intraspecific competition, while a bet‐hedging strategy is also partially supported.
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... Many basic biological aspects of the symbioses, such as feather mite dispersal depending on the host specificity (Mironov and Malyshev, 2002;Matthews et al., 2022) and patterns of their prevalence and abundance within and between host populations (Diaz-Real et al., 2014;Matthews et al., 2018), including the phenological relationships between hosts and their mites (Blanco and Frías, 2001;Peet et al., 2022) are yet to be investigated. Feather mites transmit vertically from caring parents to nestlings (Proctor, 2003;Doña et al., 2017;Peet et al., 2022; but see Blanco et al., 1997), and the incidence of infestation and ectosymbiont abundance are likely to be greater in species with social behavior, e.g. group-living or commonly roosting (Blanco et al., 1997; but see Poiani, 1992;Figuerola, 2000). ...
... However, little is known about the influence of the host's mating and parental care system on the nature of the feather mite-bird relationship. Passing mites to nestlings may lead to a drop in their number in adults tending young (Pap et al., 2010); in previous studies on vertical transmission, if males were less involved in parental care, their mite load increased during the brood stage or the reduction in feather mite numbers was less pronounced than in females (Mironov, 2000;Doña et al., 2017). Feather mite load, which is positively affected by the activity (size) of the uropygial gland, whose productivity is stimulated by androgen levels, should be greater in breeding males (but see Pap et al., 2010). ...
... While a mite load increase was predicted in males, the hypothesis of a within-season reduction in the number of mites by females via a vertical transmission to nestlings (e.g. Mironov, 2000;Doña et al., 2017) was not substantiated, although the female is the single carer of the brood and thus is in frequent touch with chicks. Theoretically, adult mites can reproduce and remain on females until the feathers of the nestlings are fully developed (but see Hamstra and Badyaev 2009 on potential preference of mites for new feathers, including growing pinfeathers). ...
The effects of ectosymbiotic feather mites on avian host fitness and factors driving the variation in mite infestation levels, such as host mating and brood care system, are poorly understood. We investigated patterns of feather mite prevalence and abundance, and relationships between infestation and body condition in breeding Aquatic Warblers Acrocephalus paludicola, a promiscuous songbird with female-only parental care. In plumage, the dominant mite species was Trouessartia bifurcata, whose prevalence more than doubled during the breeding season, to reach 95% (95% confidence limits 71–99) during the second-brood period. Approximately 5% of birds were co-infested with Proctophyllodes cf. clavatus. While mite prevalence did not differ between sexes, mite abundance was significantly greater in Aquatic Warbler females than in males, and it increased between the first- and the second-brood period irrespective of sex. No significant relationship was found between mite prevalence or abundance and host condition expressed as mass scaled to size. However, in breeding females, this relationship could be confounded by the effects of nest-dwelling ectoparasites present in some nests but only sporadically if at all detected on adult birds; 2% of adult birds were heavily infested with the hematophagous mite Dermanyssus hirundinis (Mesostigmata). Our findings indicate that the mating system may affect symbiont variability between and within host species. The high prevalence of feather mites on adult birds at the late stage of the breeding season supports the hypothesis that promiscuous species have high infestation levels. Greater mite loads on Aquatic Warbler females than males reveal a different pattern from previously studied birds. However, we did not identify any consequences of mite infestation for the female body condition or current breeding success; hence, the apparently commensal relationship does not imply costs of female promiscuity.
... In contrast, conspecific vertical transmission, i.e., from biological parents to offspring ( Fig. 1: q vc ), is expected to maintain single-host symbionts (i.e., high host specificity) and produce congruent host and symbiont phylogenies (strict codiversification) 22,23 . Yet, despite the perceived dominance of vertical transmission and low horizontal transmission rates [24][25][26][27][28] , some host-symbiont systems may simultaneously display both incongruent cophylogenetic patterns and high host specificity 3,5,16,29,30 . This conundrum challenges the role of vertical conspecific transmission in promoting codiversification and maintaining host specificity. ...
... With a few exceptions (e.g., some skin mites), they do not have a specialized dispersal stage and seem to lack any other adaptations for long-range dispersal between hosts 33,35,36 . Therefore, the most important dispersal mode of feather mites across host individuals should be via parental care, i.e., vertical conspecific transmission from host parents to offspring ( Fig. 1A: q vc ) 16,25,[37][38][39] . Consequently, the diversification of these symbionts is expected to be driven largely by host evolution. ...
... Therefore, it is crucial to understand the relative contribution of two types of conspecific transmission: vertical and horizontal (q vc and q hc ), promoting cophylogenetic concordance and high host specificity vs interspecific transmission (q vi and q hi ), that can generate cophylogenetic discordance and low host specificity (Fig. 1). In feather mites, vertical conspecific transmission (q vc ) occurring from parents to chicks during the nesting period can be accurately measured 25,39 . However, quantifying conspecific horizontal transmission (q hc ), which occurs in the form of social transmission (physical contact between hosts), is particularly difficult as it takes place outside of the nesting period. ...
In host-symbiont systems, interspecific transmissions create opportunities for host switches, potentially leading to cophylogenetic incongruence. In contrast, conspecific transmissions often result in high host specificity and congruent cophylogenies. In most bird-feather mite systems, conspecific transmission is considered dominant, while interspecific transmission is supposedly rare. However, while mites typically maintain high host specificity, incongruent cophylogenies are common. To explain this conundrum, we quantify the magnitude of conspecific vs. interspecific transmission in the brood parasitic shiny cowbird (Molothrus bonariensis). M. bonariensis lacks parental care, allowing the assessment of the role of horizontal transmission alone in maintaining host specificity. We found that despite frequent interspecific interactions via foster parental care, mite species dispersing via conspecific horizontal contacts are three times more likely to colonize M. bonariensis than mites transmitted vertically via foster parents. The results highlight the previously underappreciated rate of transmission via horizontal contacts in maintaining host specificity on a microevolutionary scale. On a macroevolutionary scale, however, host switches were estimated to have occurred as frequently as codivergences. This suggests that macroevolutionary patterns resulting from rare events cannot be easily generalized from short-term evolutionary trends.
... Reflecting their specialisation of permanent life on feathers, these mites have numerous morphological features which allow them to hold fast to specific feathers (Dabert & Mironov, 1999), and specialised diets consisting of feather preen oils and microbes (Doña et al., 2019;Proctor, 2003). Additionally, they are primarily transmitted vertically from parent to offspring at the nest (Doña et al., 2017;Peet et al., 2022) and do not engage in phoresis (Jovani et al., 2001). These adaptations and mode of transmission have led to the general presumption that mites are "diffusely" host specific (i.e., at broad taxonomic scales; Klimov et al., 2017, Doña et al., 2018, although host specificity in the feather mite system occurs along a continuum, ranging from species that are highly host-specific to those that are relatively host-general (Dabert et al., 2022;Stefan et al., 2018). ...
... First, when remaining on an individual host, mites need to disperse short distances during periods of feather moult to other nearby feathers, in order to avoid being ejected along with the moulting feather (Dubinin, 1951;Pap et al., 2005), which presumably would nearly always lead to reduced fitness. Second, mites may disperse slightly longer (although still minimal) distances to new individual hosts during vertical transmission at the nest (i.e., from adult hosts to juvenile hosts), possibly to escape intraspecific competition (Doña et al., 2017). Finally, if mites are unable to disperse before a feather is lost or their host dies (or again in response to density dependent factors), they would likely need to disperse much longer distances to a new host in order to survive once remaining resources are utilised, or potentially to escape predation by scavengers. ...
... There are multiple additional potential future extensions to this study which would add insight to our understanding of feather mite survival, dispersal, and behaviour. For example, mites may disperse more quickly to an unoccupied feather if given the option, as is observed during vertical transmission events (Doña et al., 2017;Peet et al., 2022). This could be tested using a similar laboratory setup as presented here, but by providing a feather (from the same host) that is free of mites and measuring how quickly they disperse from the occupied feather. ...
Host specificity is a fundamental life history trait of symbionts and exists on a broad continuum from symbionts that are specific to one or a few hosts (host specialists), to those associated with multiple different host species (host generalists). However, the biological mechanisms underlying the complexity and wide variation in symbiont host specificity are poorly understood from both the symbiont and host perspectives across many symbiotic systems.
Feather mites are common avian symbionts that vary in their host specificity from extreme host generalists to host specialists, even among species within the same genus.
Here, we measured and compared survival probability and rate of dispersal to determine how these traits differ between two species of feather mites in the same genus: one host generalist associated with 17 host species ( Amerodectes ischyros ) and one host specialist with only one known host ( A. protonotaria ).
We initially predicted that the host generalist would live longer and disperse more rapidly but discovered that while the host generalist mite survived longer, the host specialist mite dispersed more quickly.
The differing environmental and ecological conditions in which the hosts of these mites are associated may explain the survival and dispersal patterns we uncovered, as differential microclimates may have led to different selective pressures on each species of mite. We also noted mite behavioural observations and suggest experiments to extend our understanding of feather mite ecology and evolution.
... Yearling wagtails acquire their first remiges and rectrices during the nestling period until June (Yamashina 1934). Nestling wagtails likely receive their first set of mites vertically transmitted from their female parents (Doña et al. 2017), and provide feather mites with new feathers where they can proliferate. Because of the timing of breeding, the feather mite populations on yearling wagtails would have had eight or more months to increase by the time I trapped them at the winter roost. ...
... Because feather mites are too morphologically specialized to walk well on non-feather surfaces (Gaud and Atyeo 1996a, b, Proctor and Owens 2000), most mites are transmitted between hosts through physical contact between mite-bearing parents and their offspring, between mates or between members of communal roosts (Proctor and Owens 2000). Especially, feather mites are vertically transmitted from brooding parents to their nestlings (OConnor 1994, Pap et al. 2010, Doña et al. 2017, but see Blanco et al. 1997), and a host's feather mite numbers may fall during the breeding season because of vertical transmission to their new offspring, as is the cases in the house sparrow Passer domesticus (Pap et al. 2010), and the chaffinch Fringilla coelebs (Mironov and Malyshev 2002). Although feather mites are considered capable of knowing when feathers are about to be moulted and transfer to other feathers Serrano 2001, but see Dubinin 1951), it is likely that some feather mites do fall with moulted feathers because, as has been shown for the common starling Sturnus vulgaris (Boyd 1951) and house finch (Hamstra and Badyaev 2009), there is a decrease in FML during and after the moulting period. ...
... Recent information about the behaviour of feather mites has shown that feather mites are most active at night (Labrador et al. 2021b). Although most feather mite species show a high degree of host specificity (Proctor 2003, Doña et al. 2017, three different species of wagtails have been found hosting the same mite species (Doña et al. 2019), which is indicative of horizontal transmission. If horizontal transmission of mites between wagtails sharing roosting sites is occurring (i.e. ...
In order to investigate the relationship between feather mites and their hosts taking into account host ecology I examined relationships among feather mite load, and sex, age, wing length and body‐condition in the white wagtail Motacilla alba lugens. I captured 288 wagtails in January (the first period) 2002 at a communal roost in Osaka, central Japan. All the wagtails were ringed individually, aged as yearlings (first‐winter) or adults (older) and sexed. I measured wing length, tarsus length and body mass, calculated a body condition index (BCI) and determined the feather mite loads (FML) of each individual by visual examination of the flight feathers of one wing, giving a score using the range 0–5. I recaptured 121 wagtails after an average of 45 days (the second period), and redetermined their FML. FML was not correlated with wing length or body‐condition. Yearlings had higher FML than adults in both periods. Males had greater FML than females in the second period. No significant differences in FML between the first and second periods were detected among yearling females, or adult males, but adult females had significantly lower FML and yearling males had significantly higher FML than the other age–sex classes in the second period. The sexual difference was caused by the lower FML of adult females and the higher FML of yearling males. The BCI of yearling males was the lowest among the four combinations of sex and age‐class. I conclude that wagtails may be able to prevent overpopulation of feather mites on their own plumage. The ability to control mite populations may be related to the condition of the host.
... Analgoid feather mites cannot live independently of their hosts, other than for very brief periods, and are therefore best regarded as obligatory ecto-symbionts/ecto-mutualists. Transmission between hosts is most likely via contact when birds roost together (Jovani & Blanco, 2000) or during courtship and mating (horizontal transmission), and in the nesting period when mites can transfer to the nestlings once the latter have started growing flight feathers (vertical transmission; Blanco et al., 1997;Doña et al., 2017). Insect-mediated transmission, via hippoboscid flies, has also been considered, but is now thought to be highly unlikely . ...
... Since robins lead solitary lives throughout most of the year, opportunities for transmission for feather mites are essentially restricted to the breeding season, as with many other contact-transmitted agents (Tinsley, 1990). At this time, transfer between the pairs becomes possible (during copulation and when the cocks feed incubating hens) and from the parents to their young during brooding and feeding in the nest (Doña et al., 2017), once the latter have acquired flight feathers in the limited nestling period. ...
... In turn, the mites appeared on the nestlings on days 7-9 after hatching, depending on species, and their burdens increased steadily until fledging on the 11th day. Doña et al. (2017) treated adult European flycatchers, Ficedula hypoleuca, with an acaricide during the nesting period and showed that the nestlings of treated parents did not acquire feather mites, in contrast to those of untreated controls. Concurrently, a reduction in feather mites was observed on non-treated parent birds between when assessed first during egg incubation and then subsequently when rearing nestlings. ...
European robins (Erithacus rubecula) were mist netted and assessed for wing feather mite infestations in north‐east Nottinghamshire, England from June 1998 until March 2014. We analysed records of 899 first capture birds using three measures of infestation: prevalence of mites (% showing evidence of infestation), number of wing feathers infested with mites on one wing (NIWF), and the total mite infestation score (TOTMIS). The latter is the sum of scores (range 0–4) allocated to each of the 19 flight feathers on the assessed wing. The overall prevalence of infestation was 90.9% (95% confidence limits = 88.19–93.02), and average NIWFs and TOTMIS (±sem) were 6.0 ± 0.15 and 6.5 ± 0.23, respectively. All three measures varied significantly between age classes of birds, but not between the sexes, and varied markedly between months of the year. TOTMIS values were highest in late winter/early spring months and then dropped markedly in May to a low in summer months (usually by August), the dip in abundance of mites coinciding with the breeding season of robins. The best mixed‐effects generalised statistical model was one that comprised month of capture and age of birds but there was also a highly significant negative correlation between TOTMIS values of individual birds and the mean monthly ambient temperature in the month of capture as well as that of the preceding month. The most parsimonious interpretation of our data is that the highly consistent dip in mite abundance on adult robins from spring to summer months reflects vertical transmission of mites to their nestlings/fledgelings. These results are discussed in the context of the biology of both hosts and mites.
... Among avian arthropod ectosymbionts, feather mites are the most abundant and diverse (Kanegae et al. 2008;Arzua & Valim 2010;Doña et al. 2017;Doña et al. 2018), but their relationship with hosts has been puzzling researchers for decades. Mites inhabiting the epidermis, feather calamus and follicles may negatively affect their hosts (Proctor & Owens 2000;Proctor 2003), though those living on barbs and barbules of flight feathers (i.e. ...
... Regarding feather growth, we must consider that moult, horizontal transmission of ectosymbionts, grooming behaviour or simply the flight movements could also influence the number of arthropods. Despite the fact that feather mites mainly depend upon vertical transmission (Doña et al. 2017) and have adaptations to reduce their chances of falling off during host movement or moulting (Jovani & Serrano 2001;Proctor 2003;Doña et al. 2017), we present these results with caveat. ...
... Regarding feather growth, we must consider that moult, horizontal transmission of ectosymbionts, grooming behaviour or simply the flight movements could also influence the number of arthropods. Despite the fact that feather mites mainly depend upon vertical transmission (Doña et al. 2017) and have adaptations to reduce their chances of falling off during host movement or moulting (Jovani & Serrano 2001;Proctor 2003;Doña et al. 2017), we present these results with caveat. ...
Many organisms live in or on birds, with arthropods being the best studied ones. Ectosymbiotic arthropods may parasitise birds by feeding upon blood or feathers, thereby causing injury or competing for essential resources. Nevertheless, ectosymbionts sometimes cause no adverse effect to birds because they consume only excess preening oil, debris and microorganisms on feathers. The influence of these ectosymbionts on host body condition is still poorly understood, especially for species living in one of the most endangered biomes, the Atlantic Forest in South America. We tested for the relationships between ectosymbionts and host’s morphological traits: flight muscle condition, mass index and feather growth rate. We inspected the body surface of 282 individual birds of 45 understory‐dwelling species looking for ectosymbionts and estimated vane‐dwelling feather mite load in their remiges. We calculated ectosymbiont prevalence and mean infestation intensity in 193 individual birds from 11 species. In seven species (n = 106 individual birds), we tested for the relationship between ectosymbionts and morphological traits using generalised linear mixed models. We found a negative relationship between the presence of ectoparasites and the host pectoral muscle condition, supporting the parasitic nature of tissue‐feeding symbionts. Nevertheless, we found no relationship between vane‐dwelling feather mite loads and hosts’ morphological traits, which supports the hypothesis of likely commensalism between these organisms.
... Feather mites lack specific life-history stages for transmission and except some members of the family Epidermoptidae and the genus Strelkoviacarus Dubinin, 1953 (Analgidae) are not known to disperse by phoresis on parasitic insects associated with birds, such as hippoboscid flies (Dabert & Mironov, 1999;Doña, Potti, et al., 2017;Jovani, Tella, Sol, & Ventura, 2001;Proctor, 2003). Current knowledge suggests that their primary mode of transmission is vertical from parents to offspring in the nest (Doña, Potti, et al., 2017). ...
... Feather mites lack specific life-history stages for transmission and except some members of the family Epidermoptidae and the genus Strelkoviacarus Dubinin, 1953 (Analgidae) are not known to disperse by phoresis on parasitic insects associated with birds, such as hippoboscid flies (Dabert & Mironov, 1999;Doña, Potti, et al., 2017;Jovani, Tella, Sol, & Ventura, 2001;Proctor, 2003). Current knowledge suggests that their primary mode of transmission is vertical from parents to offspring in the nest (Doña, Potti, et al., 2017). In addition, they likely maintain a mutualistic relationship with birds in which they feed upon fungi and bacteria and likely on the uropygial gland oil that birds smear on the plumage . ...
... Circle size is proportional to haplotype frequency related to host morphology. The fact that unexpected mites coexisted with another (typical) mite species in the same host infracommunity more frequently than typical mite species (which usually do not coexist with congeneric species in the same host infracommunity) suggests that interspecific competition may preclude host range expansion (Johnson et al., 2009;Fernández-González et al., 2015;Doña, Potti, et al., 2017). Indeed, feather mite species from the same genera rarely coinhabit the same host, likely as a consequence of interspecific competition (Doña et al., 2016). ...
The high relevance of host‐switching for the diversification of highly host‐specific symbionts (i.e., those commonly inhabiting a single host species) demands a better understanding of host‐switching dynamics at an ecological scale. Here we used DNA metabarcoding to study feather mites on passerine birds in Spain, sequencing mtDNA (COI) for 25,540 individual mites (representing 64 species) from 1,130 birds (representing 71 species). Surprisingly, 1,228 (4.8%) mites from 84 (7.4%) birds were found on host species that were not the expected to be a host according to a recent bird‐feather mite associations catalog. Unexpected associations were widespread across studied mite (40.6%) and bird (43.7%) species and showed smaller average infrapopulation sizes than typical associations. Unexpected mite species colonized hosts being distantly related to the set of their usual hosts, but with similar body size. The network of bird‐mite associations was modular (i.e., some groups of bird and mite species tended to be more associated with each other than with the others), with 75.9% of the unexpected associations appearing within the module of the typical hosts of the mite species. Lastly, 68.4% of mite species found on unexpected hosts showed signatures of genetic differentiation, and we found evidence for reproduction or the potential for it in many of the unexpected associations. Results show host colonization as a common phenomenon even for these putatively highly host‐specific symbionts. Thus, host‐switching by feather mites, rather than a rare phenomenon, appears as a relatively frequent phenomenon shaped by ecological filters such as host morphology and is revealed as a fundamental component for a dynamic coevolutionary and codiversification scenario
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... They are dispersal-limited as they do not have a dedicated transmission stage like other free-living astigmatans, and they are also non-phoretic, so they do not attach to other organisms (e.g., hippoboscid flies; Jovani et al., 2001) to transmit across hosts. Instead, they are thought to primarily transmit vertically from parent to offspring during the host breeding period (Doña, Potti, et al., 2017;Peet et al., 2022). As a result, feather mites typically show a relatively high degree of host specificity, particularly at the host order level (Doña et al., 2018). ...
... The most easily observed period of feather mite transmission occurs during the hosts' breeding season during which transmission primarily occurs vertically from parent to offspring (Proctor & Owens, 2000). Evidence supporting vertical transmission during this period includes a decrease in parental feather mite loads between incubation and rearing (Doña, Potti, et al., 2017), a subsequent increase of nestling mite loads (Mironov & Malyshev, 2002) and annual fluctuations of mite loads on adult hosts that correspond with the breeding season (Peet et al., 2022). However, despite the important role of the breeding season in influencing host fitness and likely the bulk of mite transmission, it comprises only a small portion of the host's full annual cycle, particularly for longdistance migratory species. ...
Researchers often examine symbiont host specificity as a species-level pattern, but it can also be key to understanding processes occurring at the population level, which are not as well understood. The specialist-generalist variation hypothesis (SGVH) attempts to explain how host specificity influences population-level processes, stating that single-host symbionts (specialists) exhibit stronger population genetic structure than multi-host symbionts (generalists) because of fewer opportunities for dispersal and more restricted gene flow between populations. However, this hypothesis has not been tested in systems with highly mobile hosts, in which population connectivity may vary temporally and spatially. To address this gap, we tested the SGVH on proctophyllodid feather mites found on migratory warblers (family Parulidae) with contrasting host specificities, Amerodectes protonotaria (a host specialist of Protonotaria citrea) and A. ischyros (a host generalist of 17 parulid species). We used a pooled-sequencing approach and a novel workflow to analyse genetic variants obtained from whole genome data. Both mite species exhibited fairly weak population structure overall, and contrary to predictions of the SGVH, the generalist was more strongly structured than the specialist. These results may suggest that specialists disperse more freely among conspecifics, whereas generalists sort according to geography. Furthermore, our results may reflect an unexpected period for mite transmission - during the nonbreeding season of migratory hosts - as mite population structure more closely reflects the distributions of hosts during the nonbreeding season. Our findings alter our current understanding of feather mite biology and highlight the potential for studies to explore factors driving symbiont diversification at multiple evolutionary scales.
... Doña et al., 2017a). For example, on pigeons, body lice compete for resources (food and 395 space) with wing lice(Bush and Malenke, 2008). ...
... For example, the magnitude of 399 vertical transmission in feather mites has been found to respond to the degree of intraspecific 400 competition. Specifically, by transmitting vertically, feather mites abandon a more stable host 401(i.e., the adult bird), but reduce intraspecific competition for resources and space by dispersing to 402 young birds (Doña et al., 2017a). ...
Symbionts have a unique mode of life that has attracted the attention of ecologists and evolutionary biologists for centuries. As a result of this attention, these disciplines have produced a mature body of literature on host-symbiont interactions. In contrast, the discipline of symbiont conservation is still in a foundational stage. Here, we aim to integrate methodologies on symbiont coevolutionary biology with the perspective of conservation. We focus on host-symbiont cophylogenies, because they have been widely used to study symbiont diversification history and contain information on symbiont extinction. However, cophylogenetic information has never been used nor adapted to the perspective of conservation. Here, we propose a new statistic, “cophylogenetic extinction rate” (Ec), based on coevolutionary knowledge, that uses data from event-based cophylogenetic analyses, and which could be informative to assess relative symbiont extinction risks. Finally, we propose potential future research to further develop estimation of symbiont extinction risk from cophylogenetic analyses and continue the integration of this existing knowledge of coevolutionary biology and cophylogenetics into future symbiont conservation studies and practices.
... This could be due to the DNA extraction method, as described above, and also to the low feather mite content of many of the samples. This low abundance of mites could be explained by the fact that mites were sampled throughout the year, that is, including the bird's post-breeding stage when the mite infrapopulation size is much lower due to a massive vertical transmission to chicks (Doña et al. 2017a). In view of this, whenever possible, we recommend merging the mites from both wings (and even the tail, if the study allows it) into the same sample and sampling mite infrapopulations at those periods of higher abundance of mites (i.e., during the bird's pre-breeding stage and autumn, Pap et al. 2010;Diaz-Real et al. 2014;Doña et al. 2017a). ...
... This low abundance of mites could be explained by the fact that mites were sampled throughout the year, that is, including the bird's post-breeding stage when the mite infrapopulation size is much lower due to a massive vertical transmission to chicks (Doña et al. 2017a). In view of this, whenever possible, we recommend merging the mites from both wings (and even the tail, if the study allows it) into the same sample and sampling mite infrapopulations at those periods of higher abundance of mites (i.e., during the bird's pre-breeding stage and autumn, Pap et al. 2010;Diaz-Real et al. 2014;Doña et al. 2017a). Nevertheless, collecting mites from both wings and tail using cotton swabs soaked with ethanol may be stressful for birds, and therefore it should be done carefully by experts who always should prioritize birds' welfare. ...
Feather mites are among the most common and diverse ectosymbionts of birds, yet basic questions such as the nature of their relationship remain largely unanswered. One reason for feather mites being understudied is that their morphological identification is often virtually impossible when using female or young individuals. Even for adult male specimens this task is tedious and requires advanced taxonomic expertise, thus hampering large-scale studies. In addition, molecular-based methods are challenging because the low DNA amounts usually obtained from these tiny mites do not reach the levels required for high-throughput sequencing. This work aims to overcome these issues by using a DNA metabarcoding approach to accurately identify and quantify the feather mite species present in a sample. DNA metabarcoding is a widely used molecular technique that takes advantage of high-throughput sequencing methodologies to assign the taxonomic identity to all the organisms present in a complex sample (i.e., a sample made up of multiple specimens that are hard or impossible to individualise). We present a high-throughput method for feather mite identification using a fragment of the COI gene as marker and Illumina Miseq technology. We tested this method by performing two experiments plus a field test over a total of 11,861 individual mites (5360 of which were also morphologically identified). In the first experiment, we tested the probability of detecting a single feather mite in a heterogeneous pool of non-conspecific individuals. In the second experiment, we made 2 × 2 combinations of species and studied the relationship between the proportion of individuals of a given species in a sample and the proportion of sequences retrieved to test whether DNA metabarcoding can reliably quantify the relative abundance of mites in a sample. Here we also tested the efficacy of degenerate primers (i.e., a mixture of similar primers that differ in one or several bases that are designed to increase the chance of annealing) and investigated the relationship between the number of mismatches and PCR success. Finally, we applied our DNA metabarcoding pipeline to a total of 6501 unidentified and unsorted feather mite individuals sampled from 380 European passerine birds belonging to 10 bird species (field test). Our results show that this proposed pipeline is suitable for correct identification and quantitative estimation of the relative abundance of feather mite species in complex samples, especially when dealing with a moderate number (> 30) of individuals per sample.
... Besides differences in mite prevalence among, there was a higher mite prevalence for male than female hummingbirds. For our study, mite presence on feathers was evaluated during times when female birds were both off and on nests with chicks, therefore it is possible that this sex difference in mite prevalence could have been attributed to vertical transmission of Novel imaging and presence of mites on hummingbird feathers feather mites to juvenile birds [21,22]. Unfortunately, due to our limited data set, mite prevalence based on hummingbird sex and nesting female hummingbirds was not possible to evaluate. ...
... However, these findings of lower mite prevalence on female relative to male hummingbirds and a higher prevalence in juvenile hummingbirds are consistent with previous reports. [21,22] P. huitzilopochtlii was only observed on the ventral aspect of hummingbird tail feathers, and the percentage of the rachial long axis with mites present varied from a single mite up to 90% of the rachis length inhabited by mites. There was a higher percentage of mites on the lateral rectrices (R4 and R5) compared to the inner rectrices (R1 and R2). ...
Proctophyllodes huitzilopochtlii Atyeo & Braasch 1966 (Acariformes: Astigmata: Proctophyllodidae), a feather mite, was found on feathers collected from five hummingbird species in California. This mite has not been previously documented on feathers from Anna’s (Calypte anna [Lesson 1829]) or Black-chinned (Archilochus alexandri [Bourcier & Mulsant 1846]) Hummingbirds. A total of 753 hummingbirds were evaluated for the presence of mites by species (Allen’s n = 112; Anna’s n = 500; Black-chinned n = 122; Rufous n = 18; Calliope n = 1), sex (males n = 421; females n = 329; 3 unidentified), and age (juvenile n = 199; after-hatch-year n = 549; 5 unidentified). Of these 753 hummingbirds evaluated, mites were present on the rectrices of 40.9% of the birds. Significantly more Anna’s Hummingbirds were positive for rectricial mites (59.2%) compared with 8.2% of Black-chinned, 0.9% of Allen’s, 5.6% of Rufous Hummingbirds, and 0% for Calliope (p-value < 0.0001). Across all hummingbird species, male hummingbirds (44.9%) had a higher prevalence of rectricial mites compared to female hummingbirds (36.2%; p-value = 0.004), while juvenile hummingbirds (46.2%) had a non-significantly higher prevalence compared to after-hatch-year hummingbirds (39.0%; p-value = 0.089). On average, the percentage of the long axis of the rachis occupied by mites for the outer rectrices (R4 and R5) was 19%, compared to 11% for inner rectrices (R1 and R2), a significant difference (p-value = <0.0001). There was a marginal lack of significance for symmetrical distribution of tail mites with the mean left side percentage of long axis of the rachis occupied by mites being 16% and very close to the mean right side score of 18% (p-value = 0.003). The identification of the feather mite species was based on light microscopic morphometry, and mite distribution on feathers was further evaluated using tabletop scanning electron microscopy (TSEM). The hummingbird–feather mite relationship is not well understood, but the specialized TSEM technique may be especially useful in examining natural positioning and developmental aspects of the mites since it allows in situ feather examination of live mites.
... Not only this feeding activity, but also ovoposition occur during the night in feather mites living on European passerines (Labrador et al. 2022). Feather mites are thought to arrive to birds mainly by direct contact between individuals (Dabert and Mironov 1999, Proctor 2003, Doña et al. 2017a. They are dispersal-limited organisms that present different degrees of host specificity, being host-switching an important phenomenon to understand their evolution (Doña et al. 2018, 2019b, Stefan et al. 2018, Mironov and Galloway 2021, Matthews et al. 2023. ...
Symbionts are key elements of ecosystems, by playing important roles in shaping the biology and ecology of their hosts. However, the factors determining symbiont loads across host species are still unclear. Nowadays, we know that the intensity and prevalence of feather mites, the most diverse group of avian ectosymbionts, differ strongly between species. To understand those differences, we studied 17 bird species traits and two feather mite community features (species richness and composition in bird species) potentially related to interspecific differences in feather mite intensity and prevalence across bird species. We analyzed a large dataset of feather mite occurrence across European passerines: for feather mite intensity a sample of 27 424 birds from 119 bird species, and 1 805 566 feather mites counted, and for prevalence a sample of 76 126 birds from 122 bird species. Feather mite intensity and prevalence covaried positively across bird species, reinforcing the previous observation that species differ in feather mite load. Comparative analyses of the association of bird traits and feather mite richness with feather mite intensity or prevalence showed a moderate explanatory power, high model selection uncertainty, inconsistent results for both prevalence and intensity data, and contrasting results with previous comparative studies on feather mite occurrence. Furthermore, even though closely related bird species had similar feather mite communities, there was a low evolutionary conservatism of both the prevalence and intensity of feather mites across bird species (i.e. low phylogenetic signal). Finally, feather mite community composition did not explain feather mite intensity or prevalence across bird species. Overall, our large number of host and mite traits failed to satisfactorily explain the high variability in feather mite occurrence across bird species. We discuss that this difficult‐to‐understand apparent idiosyncrasy of bird species in their feather mite intensity and prevalence may be the outcome of the interaction between host and symbiont traits.
... These mites are permanent arthropods that live as commensal or ectoparasites on birds and have extremely high host specificity (Gaud and Atyeo, 1996;Dabert and Mironov, 1999). Generally transmitted from parents to fledgeling vertically or by contact outside the nest, and rarely by phoresis, the nutritional content of these mites consists of fungi and bacteria found on feathers (Doña et al., 2017(Doña et al., , 2019. Dependent on their hosts, feather mites have developed a number of morphological (e.g. ...
Feather mites (Astigmata: Analgoidea, Pterolichoidea) are arthropods that live parasitically or commensal on the wing, tail and body feathers of birds. These mites have high host specificity and diversity. Here we studied feather mites collected from birds subjected to ectoparasitic examination during ringing at the Boğazkent Bird Ringing Station (Antalya, Türkiye). Feather mite infestation was detected in 50 of 103 hosts representing 30 species during the study. As a result of microscopic examinations, 16 feather mites were identified, five of which are new records for Türkiye: Dermonoton parallelus (Mégnin and Trouessart, 1884), Gymnolichus secundus Černý and Schumilo, 1973, Proctophyllodes anthi (Vitzthum, 1922), Pteronyssus robini (Faccini and Atyeo, 1981), and Pteroherpus africanus Mironov and Kopij, 2000. Additionally, new host-parasite associations for the feather mite fauna of Türkiye were revealed in the species Dolichodectes edwardsi (Trouessart, 1885), P. clavatus Fritsch, 1961, P. pinnatus (Nitzsch, 1818), and Trouessartia kratochvili Černý, 1979.
... Most ecological research has focused on feather mites that dwell on the vanes of flight feathers due to the relative ease of observing them on live birds. However, despite their ubiquity in almost every avian order (Doña et al., 2016), specialized adaptations to reside permanently on feathers (Gaud & Atyeo, 1996), and obligate reliance on hosts for survival and transmission (Doña et al., 2017), relatively little is known about the basic biology of feather vane-dwelling mites (e.g. behaviour, diet, reproduction; Proctor, 2003). ...
Individual organisms can function as ecosystems inhabited by symbionts. Symbionts may interact with each other in ways that subsequently influence their hosts positively or negatively, although the details of how these interactions operate collectively are usually not well understood.
Vane‐dwelling feather mites are common ectosymbionts of birds and are proposed to confer benefits to hosts by consuming feather‐degrading microbes. However, it is unknown whether these mites exhibit generalist or selective diets, or how their dietary selection could potentially impact their symbiotic functional nature.
In this study, we conducted 16S rDNA and ITS1 amplicon sequencing to examine the microbial diet of feather mites. We characterized and compared the diversity and composition of bacteria and fungi in the bodies of mites living on feathers of the Prothonotary Warbler, Protonotaria citrea, to microbial assemblages present on the same feathers.
We found less diverse, more compositionally similar microbial assemblages within mites than on feathers. We also found that mites were resource‐selective. Based on the identity and known functions of microbes found within and presumably preferred by mites, our results suggest that these mites selectively consume feather‐degrading microbes. Therefore, our results support the proposition that mites confer benefits to their hosts.
This study provides insight into symbioses operating at multiple biological levels, highlights the ecological and evolutionary importance of the synergistic interactions between species, and greatly expands our understanding of feather mite biology.
... These mites live on specific feathers and microsites on feathers, primarily consuming fungi and bacteria (Doña et al. 2019). They are mainly transmitted vertically from parents to offspring (Doña et al. 2017), and because of these characteristics, they exhibit high host specificity (OConnor 1982;Gaud and Atyeo 1996;Dabert and Mironov 1999;Proctor 2003). Feather mites living on endangered birds could be at risk of extinction due to their high host specificity, as a decrease in the host population could affect them (Waki et al. 2023). ...
A new feather mite species, Mycterialges boycianae sp. nov. (Xolalgidae), was identified from the Oriental Stork, Ciconia boyciana Swinhoe, 1873, in Korea. Males of M. boycianae sp. nov. are distinguished from Mycterialges mesomorphus Gaud & Atyeo, 1981, in having a single triangular prodorsal shield, sinuous margins of the opisthosoma located between setae e 2 and h 2 on the hysteronotal shield, an oval-shaped epiandrum without posterior extensions, a shorter tibia + tarsus IV than femoragenu IV, and an absent ambulacral disc of leg IV. Females differ in having a prodorsal shield with a posterior margin that is blunt-angular, and a concave posterior margin of the hysteronotal shield with posterior extensions. This study presents the first record of the feather mite genus Mycterialges in birds of the genus Ciconia (Ciconiidae). Additionally, we determined the phylogenetic relationship among Ingrassiinae using the mitochondrial cytochrome c oxidase subunit (COI).
... European birds indicates that their abundance peaks from winter until the onset of birds' reproductive season (Blanco et al., 1997;Peet et al., 2022), when mites are transmitted from parents to offspring birds, causing a lowering of feather mite abundance in adult birds (Doña, Potti, et al., 2017;Mironov & Malyshev, 2002). ...
Comprehending symbiont abundance among host species is a major ecological endeavour, and the metabolic theory of ecology has been proposed to understand what constrains symbiont populations.
We parameterized metabolic theory equations to investigate how bird species' body size and the body size of their feather mites relate to mite abundance according to four potential energy (uropygial gland size) and space constraints (wing area, total length of barbs and number of feather barbs). Predictions were compared with the empirical scaling of feather mite abundance across 106 passerine bird species (26,604 individual birds sampled), using phylogenetic modelling and quantile regression.
Feather mite abundance was strongly constrained by host space (number of feather barbs) but not by energy. Moreover, feather mite species' body size was unrelated to the body size of their host species.
We discuss the implications of our results for our understanding of the bird–feather mite system and for symbiont abundance in general.
... We reveal that this species has persisted in the country despite the development of industrial rearing of chickens in large facilities, where young chicks are isolated from parental contact. This system impedes the primary mode of feather mite transmission between individuals -the vertical transmission (Doña et al. 2017). As demonstrated, small rural and backyard farms facilitate intergenerational contact between adult chickens and young chicks, maintaining populations of P. obtusus and other feather mites associated with chickens. ...
The feather mite Pterolichus obtusus Robin, 1877 (Astigmata: Pterolichidae) is associated with Gallus gallus domesticus (L.) worldwide. Here, we report new records of this species from rustic chickens in Brazil after a gap of 45 years, and for the first time in a northern area of this country. The major role of Brazil as one of the main chicken meat producers and exporters highlights the importance of these new findings. Knowing and keeping track of the distribution of this ectoparasitic species might offer valuable information for the development of animal health programs and policies aimed at mitigating mite pest infestations, in addition to support decision-making processes regarding research funding to study the damage caused by P. obtusus in domestic and wild fowl populations, contributing to the advancement of aviculture.
... Feather mites are ubiquitous, obligate symbionts of birds [24,25] with variable infrapopulation sizes [26][27][28]. Although they are dispersallimited and typically vertically transmitted [29,30], macroevolutionary (i.e., species level) studies have demonstrated that they often do not perfectly coevolve with their hosts. Instead, there is evidence for clade-limited host switching and a wide range of host specificity, which could be associated with the differential life histories of mites [31] or hosts [32][33][34]. ...
Microscopic symbionts represent crucial links in biological communities. However, they present technical challenges in high-throughput sequencing (HTS) studies due to their small size and minimal high-quality DNA yields, hindering our understanding of host–symbiont coevolution at microevolutionary and macroevolutionary scales. One approach to overcome those barriers is to pool multiple individuals from the same infrapopulation (i.e., individual host) and sequence them together (Pool-Seq), but individual-level information is then compromised. To simultaneously address both issues (i.e., minimal DNA yields and loss of individual-level information), we implemented a strategic Pool-Seq approach to assess variation in sequencing performance and categorize genetic diversity (single nucleotide polymorphisms (SNPs)) at both the individual-level and infrapopulation-level for microscopic feather mites. To do so, we collected feathers harboring mites (Proctophyllodidae: Amerodectes protonotaria) from four individual Prothonotary Warblers (Parulidae: Protonotaria citrea). From each of the four hosts (i.e., four mite infrapopulations), we conducted whole-genome sequencing on three extraction pools consisting of different numbers of mites (1 mite, 5 mites, and 20 mites). We found that samples containing pools of multiple mites had more sequencing reads map to the feather mite reference genome than did the samples containing only a single mite. Mite infrapopulations were primarily genetically structured by their associated individual hosts (not pool size) and the majority of SNPs were shared by all pools within an infrapopulation. Together, these results suggest that the patterns observed are driven by evolutionary processes occurring at the infrapopulation level and are not technical signals due to pool size. In total, despite the challenges presented by microscopic symbionts in HTS studies, this work highlights the value of both individual-level and infrapopulation-level sequencing toward our understanding of host–symbiont coevolution at multiple evolutionary scales.
... As some parasites are transmitted vertically from parents to their offspring (Clayton & Tompkins, 1994;Skoracki, 2011;Doña et al., 2017; but see e.g. Darolov a et al., 2001), it is reasonable to expect that brood parasite nestlings will acquire at least generalist parasites from their foster species. ...
Interactions between avian brood parasites, their hosts and their parasites provide an ideal model system for studying coevolutionary processes across multiple hierarchical levels. Despite this, how brood parasitism affects the ecology and transmission of bird ectoparasites is not well known. Here, we examined the mite fauna of great reed warbler Acrocephalus arundinaceus nests successfully parasitized and unparasitized by the common cuckoo Cuculus canorus to find whether there is vertical transmission of northern fowl mites Ornithonyssus sylviarum, a generalist blood‐feeding parasite of birds, through infected nests. Although there was no difference in the prevalence of mites between successfully parasitized and unparasitized nests, the former nests exhibited two times lower mite abundances than the latter nests. Importantly, none of the common cuckoo nestlings examined shortly before fledging carried mites, whereas the great reed warbler nestlings were infested in almost half of the contaminated nests. Thus, our results indicate that, despite their high dispersal abilities, northern fowl mites may be unable to survive or reproduce on the common cuckoo nestlings. Factors that can contribute to the observed patterns are discussed.
... 13. Inter-and intraspecific competition: Symbionts interact on or in their hosts within diverse symbiont communities Clayton et al., 2015;Doña et al., 2017a;Harbison et al., 2008;Johnson et al., 2009;Perez and Atyeo, 1984;Proctor, 2003). Overall, competitively superior species are expected to be less vulnerable to extinction than competitively inferior species (Clayton et al., 2015). ...
Symbionts have a unique mode of life that has attracted the attention of ecologists and evolutionary biologists for centuries. As a result of this attention, these disciplines have produced a mature body of literature on host-symbiont interactions. In contrast, the discipline of symbiont conservation is still in a foundational stage. Here, we aim to integrate methodologies for symbiont coevolutionary biology with symbiont conservation. We focus on host-symbiont cophylogenies, because they have been widely used to study symbiont diversification history and contain information on symbiont extinction. However, cophylogenetic information has never been used nor adapted to the perspective of conservation. Here, we propose a new statistic, “cophylogenetic extinction rate” (Ec), which is based on coevolutionary knowledge from event-based cophylogenetic analyses and could be informative to assess relative symbiont extinction risks. Finally, we propose potential future research to further develop methods to estimate symbiont extinction risk from cophylogenetic analyses, and to continue the integration of this existing knowledge of coevolutionary biology and cophylogenetics into future symbiont conservation studies and practices.
... Feather mites are host-specific symbionts with limited dispersal capabilities, but also with some clade-limited host-switching [25][26][27][35][36][37][38][39] . Previous studies have documented multi-host species [35][36][37]40 and cases of morphologically-cryptic but genetically different mite species [35][36][37]40 . ...
Some symbiont species are highly host-specific, inhabiting only one or a very few host species, and typically have limited dispersal abilities. When they do occur on multiple host species, populations of such symbionts are expected to become genetically structured across these different host species, and this may eventually lead to new symbiont species over evolutionary timescales. However, a low number of dispersal events of symbionts between host species across time might be enough to prevent population structure and species divergence. Overall, processes of evolutionary divergence and the species status of most putative multi-host symbiont systems are yet to be investigated. Here, we used DNA metabarcoding data of 6,023 feather mites (a total of 2,225 OTU representative sequences) from 147 infracommunities (i.e., the assemblage consisting of all mites of different species collected from the same bird host individual) to investigate patterns of population genetic structure and species status of three different putative multi-host feather mite species Proctophyllodes macedo Vitzthum, 1922, Proctophyllodes motacillae Gaud, 1953, and Trouessartia jedliczkai (Zimmerman, 1894), each of which inhabits a variable number of different closely related wagtail host species (genus Motacilla). We show that mite populations from different host species represent a single species. This pattern was found in all the mite species, suggesting that each of these species is a multi-host species in which dispersal of mites among host species prevents species divergence. Also, we found evidence of limited evolutionary divergence manifested by a low but significant level of population genetic structure among symbiont populations inhabiting different host species. Our study agrees with previous studies showing a higher than expected colonization opportunities in host-specific symbionts. Indeed, our results support that these dispersal events would allow the persistence of multi-host species even in symbionts with limited dispersal capabilities, though additional factors such as the geographical structure of some bird populations may also play a role.
... However, in the case of the shearwaters in Cape Verde, although they share habitat, they are often temporally isolated during the breeding season. Temporal segregation should "a priori" prevent host-switching given that feather mites are not able to live for long periods outside of the host body (Dubinin, 1951;Proctor, 2003;Doña et al., 2017c). It could be that feather mites survive in molted feathers in the nest substrate for relatively long periods of time, but this explanation seems unlikely given the escape behavior of feather mites during molting (Jovani and Serrano, 2001). ...
Feather mites are useful models for studying speciation due to their high diversity and strong degree of host specialization. However, studies to date have focused on the evolution of higher-level mite taxa while much hidden diversity likely occurs at the level of host genera and species. In this study, we examined the diversity and evolution of feather mites infesting six sympatric seabird species from six genera, breeding in the Cape Verde archipelago. We report 32 feather mite morphospecies categorized into 10 genera and three families, of which nine correspond to new, undescribed species. Molecular data corroborated morphological species descriptions, except for two morphologically-cryptic, but genetically distinct mite lineages related to Zachvatkinia oceanodromae and Laminalloptes simplex. Using these communities, we then applied a co-structure approach to test the contribution of ectosymbiont and host factors in driving feather mite evolution. Most seabird species hosted specific and unique feather mite species, even under sympatric conditions, and in general, feather mite species exhibited strong host-driven genetic structure. However, patterns of genetic differentiation were variable. That is, some mite species are more generalist than others and mite lineages/haplotypes can be shared by related seabird species. Interestingly, host-specific mites (e.g., Zachvatkinia spp.) tend to display much higher intra-specific diversity compared to more generalist mites (e.g., Microspalax and Plicatalloptes spp.). We discuss ectosymbiont and host life-history traits that might generate these patterns, such as host dispersal and breeding behavior and/or mite spatial and trophic specialization. Our findings highlight both the vast and largely unrecognized diversity of avian feather mites on seabirds, and the intrinsic complexity of the ecological processes underlying the evolution of these ectosymbionts.
... (iii) specific distribution on particular feathers and microsites on feathers (Fern andez-Gonz alez, P erez-Rodr ıguez, de la Hera, Proctor, & P erez-Tris, 2015;Jovani & Serrano, 2001Stefan et al., 2015); and (iv) mainly vertical mode of transmission (Doña, Potti, et al., 2017;Jovani, Tella, Sol, & Ventura, 2001;Mironov & Malyshev, 2002). However, as with many other symbionts, they are challenging to study, and this has strongly hampered our comprehension of this system (Doña, Diaz-Real, et al., 2015;Proctor, 2003;Proctor & Owens, 2000). ...
Parasites and other symbionts are crucial components of ecosystems, regulating host populations and supporting food webs. However, most symbiont systems, especially those involving commensals and mutualists, are relatively poorly understood. In this study, we have investigated the nature of the symbiotic relationship between birds and their most abundant and diverse ectosymbionts: the vane‐dwelling feather mites. For this purpose, we studied the diet of feather mites using two complementary methods. First, we used light microscopy to examine the gut contents of 1,300 individual feather mites representing 100 mite genera (18 families) from 190 bird species belonging to 72 families and 19 orders. Second, we used high‐throughput sequencing (HTS) and DNA metabarcoding to determine gut contents from 1,833 individual mites of 18 species inhabiting 18 bird species. Results showed fungi and potentially bacteria as the main food resources for feather mites (apart from potential bird uropygial gland oil). Diatoms and plant matter appeared as rare food resources for feather mites. Importantly, we did not find any evidence of feather mites feeding upon bird resources (e.g., blood, skin) other than potentially uropygial gland oil. In addition, we found a high prevalence of both keratinophilic and pathogenic fungal taxa in the feather mite species examined. Altogether, our results shed light on the long‐standing question of the nature of the relationship between birds and their vane‐dwelling feather mites, supporting previous evidence for a commensalistic–mutualistic role of feather mites, which are revealed as likely fungivore–microbivore–detritivore symbionts of bird feathers.
... During the breeding season, much of the host's environment is at the nest, especially for females. In addition, it is at the nest where feather mites primarily disperse to new hosts (the offspring; Doña et al., 2017), which means that they would be even more affected by the nest environment as they move from host to host. Specifically, understory dwelling, cavity-nesting species may occupy nests that make them more susceptible to parasitic mite abundances than their canopy dwelling, open-cup nesting counterparts (Galván & Sanz, 2006). ...
Feather mites are obligatory ectosymbionts of birds that primarily feed on the oily secretions from the uropygial gland. Feather mite abundance varies within and among host species and has various effects on host condition and fitness, but there is little consensus on factors that drive variation of this symbiotic system. We tested hypotheses regarding how within-species and among-species traits explain variation in both (1) mite abundance and (2) relationships between mite abundance and host body condition and components of host fitness (reproductive performance and apparent annual survival). We focused on two closely related (Parulidae), but ecologically distinct, species: Setophaga cerulea (Cerulean Warbler), a canopy dwelling open-cup nester, and Protonotaria citrea (Prothonotary Warbler), an understory dwelling, cavity nester. We predicted that feather mites would be more abundant on and have a more parasitic relationship with P. citrea, and within P. citrea, females and older individuals would harbor greater mite abundances. We captured, took body measurements, quantified feather mite abundance on individuals’ primaries and rectrices, and monitored individuals and their nests to estimate fitness. Feather mite abundance differed by species, but in the opposite direction of our prediction. There was no relationship between mite abundance and any measure of body condition or fitness for either species or sex (also contrary to our predictions). Our results suggest that species biology and ecological context may influence mite abundance on hosts. However, this pattern does not extend to differential effects of mites on measures of host body condition or fitness.
... Females of some feather mite lineages inhabiting the skin engage in phoresy on more vagile bird-associates, such as hippoboscid flies (Philips andFain 1991, Proctor andJones 2004). Vane-dwelling feather mites are thought to be transmitted between host individuals only by direct contact, typically vertically from parent to offspring at the nest (Proctor 2003, Doña et al. 2017a. Rare cases of feather mite horizontal transmission have been documented (Hernandes et al. 2014), and experiments have shown that individual feather mites have the ability to move to heterospecifics when given the opportunity (Dubinin 1951, Bridge 2002. ...
Host-symbiont relationships are ubiquitous in nature, yet evolutionary and ecological processes that shape these intricate associations are often poorly understood. All orders of birds engage in symbioses with feather mites, which are ectosymbiotic arthropods that spend their entire life on hosts. Due to their permanent obligatory association with hosts, limited dispersal, and primarily vertical transmission, we hypothesized that the cospeciation between feather mites and hosts within one avian family (Parulidae) would be perfect (strict cospeciation). We assessed cophylogenetic patterns and tested for congruence between species in two confamiliar feather mite genera (Proctophyllodidae: Proctophyllodes, Amerodectes) found on 13 species of migratory warblers (and one other closely related migratory species) in the eastern United States. Based on COI sequence data, we found three Proctophyllodes lineages and six Amerodectes lineages. Distance- and event-based cophylogenetic analyses suggested different cophylogenetic trajectories of the two mite genera, and although some associations were significant, there was little overall evidence supporting strict cospeciation. Host switching is likely responsible for incongruent phylogenies. In one case, we documented Prairie Warblers (Setophaga discolor) harboring two mite species of the same genus. Most interestingly, we found strong evidence that host ecology may influence the likelihood of host switching occurring. For example, we documented relatively distantly related ground-nesting hosts (Ovenbird, Seiurus aurocapilla, and Kentucky Warbler, Geothlypis formosa) sharing a single mite species, while other birds are shrub/canopy or cavity nesters. Overall, our results suggest that cospeciation is not the case for feather mites and parulid hosts at this fine phylogenetic scale, and raise the question if cospeciation applies for other symbiotic systems involving hosts that have complex life histories. We also provide preliminary evidence that incorporating host ecological traits into cophylogenetic analyses may be useful for understanding how symbiotic systems have evolved.
... Feather mites cannot survive off the host (Dubinin, 1951;Proctor, 2003) and have very restricted transmission capabilities because they lack a specific stage for transmission found in many free-living astigmatan mites (a morphologically modified deutonymph also referred to as a hypopus), and other stages do not engage in phoretic behaviour (i.e., they do not attach to larger and more mobile symbionts for transmission, in contrast to many feather lice that hitch rides on hippoboscid flies). Hence, they are mainly transmitted vertically from parents to offspring (Doña, Potti et al., 2017;Jovani, Tella, Sol, & Ventura, 2001;Proctor, 2003). ...
Aim
Highly host‐specific symbionts are very rarely found except with their typical host species. Although switches to new hosts are rare and difficult to detect, a switch to a host phylogenetically distant from the original one (a ‘major host switch’) could allow diversification of the symbionts onto the new host lineage. The consequences of such major host switches on the diversification of highly host‐specific symbionts of animals have rarely been explored. Here, we examine the host specificity of vane‐dwelling feather mites, a group that shows strong specificity, together with their host‐switching dynamics and the consequences of major host switches for their diversification.
Location
Global.
Time period
From 1882 to 2015.
Major taxa studied
Feather mites and birds.
Methods
Using the largest published dataset of feather mite–bird associations, we analysed raw, phylogenetic and geographical host specificity of feather mites. We studied host‐switching dynamics by describing the sharing by feather mites of bird species with different phylogenetic distances. For three of the most species‐rich feather mite families, we quantified the consequences of major host switches for feather mite diversification.
Results
Most feather mite species (84%) inhabit one to three very closely related host species. Assemblages of feather mites on birds do not show a geographical signature, but rather show strong host‐driven structuring. The probability that a mite species occurs on two host species decays sharply with host phylogenetic distance, with only one instance of a feather mite species occupying distantly related hosts from different orders. However, results suggest that despite the strong host specificity, a few major host switches triggered the origin of 21% of the species and 38% of the genera of the mite families studied.
Main conclusions
We show that feather mites are highly host‐specific symbionts, whose assemblages do not show geographical structure, even at a continental scale. We conclude that major host switches are very rare events with strong macroevolutionary consequences for feather mite diversity.
... Feather mites only leave the host during transmission, mainly when they pass from parents to offspring (i.e. vertical transmission) (Mironov & Malishev 2002;Doña et al. 2017). ...
Research Highlight: del Mar Labrador, M., Serrano, D., Doña, J., Aguilera, E., Arroyo, J. L., Atiénzar, F., Barba, E., Bermejo, A., Blanco, G., Borràs, A., Calleja, J. A., Cantó, J. L., Cortés, V., de la Puente, J., de Palacio, D., Fernández-González, S., Figuerola, J., Frías, Ó., Fuertes-Marcos, B. Garamszegi, L. Z., Gordo, Ó., Gurpegui, M., Kovács, I., Martínez, J. L., Meléndez, L., Mestre, A., Møller, A. P., Monrós, J. S., Moreno-Opo, R., Navarro, C., Pap, P. L., Pérez-Tris, J., Piculo, R., Ponce, C., Proctor, H., Rodríguez, R., Sallent, Á., Senar, J., Tella, J. L., Vágási, C. I., Vögeli, M., & Jovani, R. (2023). Host space, not energy or symbiont size, constrains feather mite abundance across passerine bird species. Journal of Animal Ecology, https://doi.org/10.1111/1365-2656.14032. Symbionts represent crucial links between species in ecosystems. Consequently, understanding their patterns of abundance is a major goal in the study of symbioses. However, multiple biotic and abiotic factors may regulate symbionts, and disentangling the mechanisms that drive variation in their abundance across host species is challenging. One promising strategy to approach this challenge is to incorporate biologically relevant data into theoretical models. In a recent study, Labrador et al. (2023) used this strategy to investigate the poorly understood symbiosis between feather mites and their avian hosts. They integrate a remarkable amount of empirical data with models based on the metabolic theory of ecology to determine what factors limit feather mite abundance across European passerines. Their quantitative analyses indicate that the number of feather barbs limits mite abundance across host species, suggesting that mite populations are spatially, but not energetically, constrained. These findings not only reveal mechanisms that may drive the variation in feather mite abundances across hosts, but also advance our understanding of the ecology of interspecific interactions more generally.
This paper reviews the state of knowledge of the feather mites of Australia (Arachnida: Acariformes: Astigmata). The known fauna includes 149 species arranged in 95 genera and 24 families, in the Superfamilies Analgoidea and Pterolichoidea. A checklist of the fauna is provided, including bibliographic details for every species and genus. The bird host and collecting localities are listed for every species, and taxonomic and nomenclatural problems are discussed where necessary. The total fauna may include as many as 800 undescribed species. The checklist is preceded by a brief review of some aspects of the biology of feather mites, which have not been studied in the context of the Australian fauna.The correct spelling for a family of respiratory tract parasites is confirmed as Kytoditidae. Dabertia indistincta (Dabert & Atyeo, 1993) comb. n. (Syringobiidae) and Hemialges australis (Trouessart, 1885) comb. n. (Analgidae) are new combinations proposed herein.
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 macroevolutionary 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 versus 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. 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.
Most humans carry mites in the hair follicles of their skin for their entire lives. Follicular mites are the only metazoans tha continuously live on humans. We propose that Demodex folliculorum (Acari) represents a transitional stage from a host-injuring obligate parasite to an obligate symbiont. Here, we describe the profound impact of this transition on the genome and physiology of the mite. Genome sequencing revealed that the permanent host association of D. folliculorum led to an extensive genome reduction through relaxed selection and genetic drift, resulting in the smallest number of protein-coding genes yet identified among panarthropods. Confocal microscopy revealed that this gene loss coincided with an extreme reduction in the number of cells. Single uninucleate muscle cells are sufficient to operate each of the three segments that form each walking leg. While it has been assumed that the reduction of the cell number in parasites starts early in development, we identified a greater total number of cells in the last developmental stage (nymph) than in the terminal adult stage, suggesting that reduction starts at the adult or ultimate stage of development. This is the first evolutionary step in an arthropod species adopting a reductive, parasitic or endosymbiotic lifestyle. Somatic nuclei show underreplication at the diploid stage. Novel eye structures or photoreceptors as well as a unique human host melatonin-guided day/night rhythm are proposed for the first time. The loss of DNA repair genes coupled with extreme endogamy might have set this mite species on an evolutionary dead-end trajectory.
Obligate symbionts may be genetically structured among host individuals and among phenotypically distinct host populations. Such processes may in turn determine within-host genetic diversity of symbionts, which is relevant for understanding symbiont population dynamics. We analysed the population genetic structure of two species of feather mites ( Proctophyllodes sylviae and Trouessartia bifurcata ) in migratory and resident blackcaps Sylvia atricapilla that winter sympatrically. Resident and migratory hosts may provide mites with habitats of different qualities, what might promote specialization of mite populations. We found high genetic diversity of within-host populations for both mite species, but no sign of genetic structure of mites between migratory and resident hosts. Our results suggest that, although dispersal mechanisms between hosts during the non-breeding season are unclear, mite populations are not limited by transmission bottlenecks that would reduce genetic diversity among individuals that share a host. Additionally, there is no evidence that host phenotypic divergence (associated with the evolution of migration and residency) has promoted the evolution of host-specialist mite populations. Unrestricted dispersal among host types may allow symbiotic organisms to avoid inbreeding and to persist in the face of habitat heterogeneity in phenotypically diverse host populations.
Phoresy is a behavior where one organism hitches a ride on another more mobile organism. This is a common dispersal mechanism among relatively immobile species that specialize on patchy resources. Parasites specialize on patchily distributed resources: their hosts. Although host individuals are isolated in space and time, parasites must transmit between hosts or they will die with their hosts. Lice are permanent obligate ectoparasites that complete their entire life cycle on their host. They typically transmit when hosts come into direct contact; however, lice are also capable of transmitting phoretically. Yet, phoresy is rare among some groups of lice. Fundamental morphological differences have traditionally been used to explain the phoretic differences among different suborders of lice; however, these hypotheses do not fully explain observed patterns. We propose that a more fundamental natural history trait may better explain variation in phoresy. Species able to disperse under their own power should be less likely to engage in phoresy than more immobile species. Here we experimentally tested the relationship between independent louse mobility and phoresy using a system with four species of lice (Phthiraptera: Ischnocera and Amblycera) that all parasitize a single host species, the Rock Pigeon (Columba livia). We quantified the relative ability of all four species of lice to move independently off the host, and we quantified their ability to attach to, and remain attached to, hippoboscid flies (Pseudolynchia canariensis). Our results show that the most mobile louse species is the least phoretic, and the most phoretic species is quite immobile off the host. Our findings were consistent with the hypothesis that phoretic dispersal should be rare among species of lice that are capable of independent dispersal; however other factors such as interspecific competition may also play a role.
Understanding what shapes variation in genetic diversity among species remains a major challenge in evolutionary ecology, and it has been seldom studied in parasites and other host-symbiont systems. Here, we studied mtDNA variation in a host-symbiont non-model system: 418 individual feather mites from 17 feather mite species living on 17 different passerine bird species. We explored how a surrogate of census size, the median infrapopulation size (i.e., the median number of individual parasites per infected host individual), explains mtDNA genetic diversity. Feather mite species genetic diversity was positively correlated with mean infrapopulation size, explaining 34% of the variation. As expected from the biology of feather mites, we found bottleneck signatures for most of the species studied but, in particular, three species presented extremely low mtDNA diversity values given their infrapopulation size. Their star-like haplotype networks (in contrast with more reticulated networks for the other species) suggested that their low genetic diversity was the consequence of severe bottlenecks or selective sweeps. Our study shows for the first time that mtDNA diversity can be explained by infrapopulation sizes, and suggests that departures from this relationship could be informative of underlying ecological and evolutionary processes.
Direct horizontal transmission of pathogenic and mutualistic symbionts has profound consequences for host and symbiont fitness alike. While the importance of contact rates for transmission is widely recognized, the processes that underlie variation in transmission during contact are rarely considered. Here, we took a symbiont's perspective of transmission as a form of dispersal and adopted the concept of condition-dependent dispersal strategies from the study of free-living organisms to understand and predict variation in transmission in the cleaning symbiosis between crayfish and ectosymbiotic branchiobdellidan worms. Field study showed that symbiont reproductive success was correlated with host size and competition among worms for microhabitats. Laboratory experiments demonstrated high variability in transmission among host contacts. Moreover, symbionts were more likely to disperse when host size and competition for microhabitat created a fitness environment below a discrete minimum threshold. A predictive model based on a condition-dependent symbiont dispersal strategy correctly predicted transmission in 95% of experimental host encounters and the exact magnitude of transmission in 67%, both significantly better than predictions that assumed a fixed transmission rate. Our work provides a dispersal-based understanding of symbiont transmission and suggests adaptive symbiont dispersal strategies can explain variation in transmission dynamics and complex patterns of host infection. © 2015 The Author(s) Published by the Royal Society. All rights reserved.
The matching habitat choice hypothesis holds that individuals with different phenotypes actively select the habitats to which they are best adapted, hence maximizing fitness. Despite the potential implications of matching habitat choice for many ecological and evolutionary processes, very few studies have tested its predictions. Here, we use a 26-year dataset on a spatially structured population of pied flycatchers (Ficedula hypoleuca) to test whether phenotype-dependent dispersal and habitat selection translate into increased fitness, as measured by recruitment success. In our study system, males at the extremes of the body size range segregate into deciduous and coniferous forests through nonrandom dispersal. According to the matching habitat choice hypothesis, fitness of large-sized males is expected to be higher in the deciduous habitat, where they preferentially settle to breed, while the reverse would be true for small-sized males, which are more frequent in the coniferous forest. Our results showed that recruitment success in the coniferous forest increased non-linearly with body size, with males at the middle of the size range having higher fitness than both large and small-sized males. However, no clear trend was observed in the deciduous forest where males of either size had similar fitness. After empirically discarding other important processes potentially confounding matching habitat choice, as genotype- and body condition-dependent dispersal, competitive exclusion remains the most likely force shaping the nonrandom distribution of male pied flycatchers. A conclusive demonstration of the operation and occurrence of matching habitat choice in nature remains therefore to be done.
Recent molecular phylogenetic analyses have revealed that some apparently oligoxenous feather mite species are in fact monoxenous cryptic species with little morphological differentiation. In this study we analyzed two species, Zachvatkinia isolata (Avenzoariidae) and Alloptes (Sternalloptes) stercorarii (Alloptidae) which prefer different parts of the plumage of two sister species of birds: arctic skua (Stercorarius parasiticus) and long-tailed skua (S. longicaudus) breeding on tundra in the High Arctic archipelago of Svalbard. Given that there are no reports about hybridization events between the host species, we expected that both skuas would have a species-specific acarofauna. The genetic distances among DNA-barcode sequences (COI and 28S rDNA), phylogenetic tree topologies, and haplotype networks of the COI sequences of mites suggested extensive gene flow in Z. isolata between and within populations inhabiting both skua species, whereas the Alloptes populations were host specific and sufficiently genetically separated as to warrant species-level status. The discrepancy in the genetic structure of Alloptes and Zachvatkinia populations suggests frequent but transient contacts between the two skua species in which the probability of mite exchange is much higher for Zachvatkinia, which is present in high numbers and inhabits exposed parts of primary flight feathers, than for the less abundant Alloptes that lives primarily in more protected and inaccessible parts of the plumage. We discuss the possible nature of these contacts between host species and the area(s) where they might take place. The star-like structures in the haplotype network as well as high haplotype diversity and low nucleotide diversity observed in Z. isolata are concordant with the known dispersal strategy of feather mites: vertical colonization of new host individuals followed by rapid growth of founder populations.
The seasonal dynamics of the Monojoubertia microphylla micropopulations in different sex and age groups of the chaffinch Fringilla coelebs (Passeriformes: Fringillidae) have been studied during the nest and migration periods in the North-West of Russia. Three bird groups were determined within the chaffinch population during the study: adult males, adult females, immature chaffinches. Total number of bird specimens examined — 353.
In all chaffinch groups, the mean mite numbers and age structure of mite micropopulations were similar during the spring migration. The number of mites gradually increased from April to May. During the nest and autumn migration periods the seasonal dinamics of M. microphylla micropopulations were quite different on adult males and females of the chaffinch, because of different roles of male and female in the process of infestation the young bird generation. On the adult chaffinch males, the mite number continued to increase during the breeding period (June) and began to decrease significantly in July because of the post-breeding plumage molt. The mite number slowly decreased in the end of summer and the autumn migration. On the adult chaffinch females, the mite number decreased abruptly during the nest period. During this period, the chaffinch female sits together with nestlings for a long time, and the great number of its mites (about 60 % of a mite micropopulation) moves from the female onto the nestlings. The mite micropopulation migrated onto nestling is represented mainly by males, females (about 25 % each) and tritonymphs (38 %). Total mite number on the chaffinch females continued to decrease in July under the influence of post-breeding molt and slightly increased up to the autumn migration only. On the young chaffinches, the number of M. microphylla quickly increased during the second part of summer. It is the result of the great quota of mite instars being ready for the reproduction (imago, tritonymphs) within the micropopulation migrated from the chaffinch female onto the nestlings. The decrease of the M. microphylla micropopulation on the young birds was observed in the autumn only.
In the end autumn migration (October), the mean numbers of mites on all chaffinch groups became approximately similar, but did not reach the mean rate observed in the beginning of the spring migration. During both migration periods, the imago and all preimaginal instars of M. microphylla were active, the diapause was not observed. In the beginning of spring migration and the end of autumn migration the main part of the mite micropopulations was represented by females, while in all other periods of chaffinch's stay in the North-West of Russia the immature instars predominated.
Polygyny was studied for 4 years in a central Spanish montane population of Pied Flycatchers. The frequency of Polygyny was low (4.4%) and limited to two females per male. Bigamous males only differed from monogamous males in that they were older. Secondary females had a lower reproductive success and their surviving nestlings were smaller and undernourished, probably due to the absence of the male during most of the early nestling period. Primary and secondary nests were separated by short distances, which makes it hard to explain the mating system by male ‘cheating’ or female-female aggression. Secondary females were mainly young inexperienced birds which might not otherwise have bred in their first potential breeding season.
Except for Dubinin's classic works in the 1950s, there is very little information on the natural history or population dynamics of feather mites (Astigmata: Acariformes, Pterolichoidea). We studied variation in numbers of the different life stages of the feather mite Proctophyllodes pinnatus (Nitzsch) (Analgoidea: Proctophyllodidae) on captive House Finches Carpodacus mexicanus (Müller) (Passeriformes: Fringillidae) from December 2003 to November 2004. Simultaneously, we also studied how preen gland secretion varied in those birds. We monitored 20 House Finches (10 individuals of each sex) for the presence of mites on their wing feathers. There was seasonal variation in the abundance and prevalence of mites on different individual birds. Most birds did not show any mites from December to April. Mite numbers started to increase in July and peaked in August–September. In September, we observed more mites of early stages than in any other months. We also observed higher proportions of adults in August and October and fewer adults than expected in September, suggesting that more than one generation was involved. By November, very few mites were present on the wing feathers. The variation in mite numbers paralleled variation in the composition and quantity of preen gland secretions produced by the host House Finches. In most of the captive birds, secretion peaked in the month following peak mite-abundance. During the period when mite abundance was highest, secretions contained a higher diversity of chemicals. Prevalence of mites on wild House Finches showed similar trends to those observed in captive birds. Relative abundances of life stages on wild birds collected in July were similar to those observed for captive House Finches in the same month.
This paper investigates patterns of age-related variation among pairs in a Spanish population of pied flycatchers (Aves: Muscicapidae) studied over a five-year period. Ages of birds in the sample ranged from one to seven years. Pairs formed at random with respect to size and body condition but age-based assortative mating was significant. Earliest breeding dates were observed in older (≥ 2 years) individuals, followed by mixed-age pairs, while younger pairs bred at later dates. However, when variation in breeding dates in relation to age of pair members was taken into account, quantity (number of recruits) and quality (size, body condition) of young did not differ among pairs of diverse age composition, although pairs composed of very old males and young females had fledglings with a lower weight. No positive evidence that age-assortative bonds were caused by active mate choice for absolute male age was found. However, the within-female repeatability of the absolute differences between her age and that of her mates was significant, indicating that the age difference between pairs may be a criterion for mate choice. Experimental studies are needed to determine whether age-assortative bonds and consistency of age differences between a female and her mates are caused by similar age-related patterns of arrival from spring migration in both sexes, or whether they are due to mate choice. Overall, the age of the pair did not play a significant role in the reproductive success of individual pied flycatchers, but showed a strong influence on arrival dates and onset of breeding. Variation in individual quality and high variance in reproductive success may override any fitness benefit resulting from pairing with older more experienced birds. In addition, age-assortative mating patterns in this population do not appear to alter the process of sexual selection based on variation among males in the expression of secondary sex ornaments.
Protandry, the earlier arrival of males than females to breeding areas, is widespread in birds, but its underlying mechanisms are far from well understood. The two, not mutually exclusive most highly supported hypoth-eses to explain avian protandry postulate that it has evolved from intrasexual male competition to acquire the best territories ("rank advantage" hypothesis) and/or to maxi-mize the number of mates ("mate opportunity" hypothesis). We studied for two consecutive years the relative impor-tance of both hypotheses in a population of pied flycatchers (Ficedula hypoleuca), a territorial songbird with a mixed mating strategy. We measured territory quality using a long-term dataset on nest occupation and breeding output, and we used molecular techniques to assess male fitness across the range of social and genetic mating options. Territory quality was unrelated to breeding date and had no influence on extra-pair paternity or social polygynous events. However, males breeding early increased their chances of becoming socially polygynous and/or of attaining extra-pair paternity and, as a consequence, increased their total reproductive success. These results support the "mate opportunity" hypothesis, suggesting that sexual selection is the main mechanism driving protandry in this population.
Feather mites (suborder Astigmata, superfamilies Analgoidea, Pterolichoidea and Freyaniidae) are among the commonest ec-tosymbionts of birds. Most researchers have assumed they are parasites, having negative effects on hosts. Here we present evidence that suggests that feather mites may not be parasites. We develop a framework for considering conditional outcomes in these interspecific associations, dealing with different kinds of relationships between symbionts. The non-parasitic status of feather mites is supported by a literature review as well as by preliminary data on mites' food. We illustrate symbiotic rela-tionships with a graphical model showing different scenarios in which hosts' cost-benefit relations are determined by the interac-tions among their symbionts. Birds are hosts to numerous symbionts, some of which can be parasitic, i.e decreasing the fitness of their hosts. Failure to detect costs of parasitism might be due to methodological problems or analytical limitations, be-cause detrimental effects may be confounded or masked by other factors (e.g. Clayton et al. 1992), including infections by other parasitic taxa (e.g. Merino and Potti 1995) and changes in host behaviour to minimise the costs of being parasitised (Hart 1997). Alternatively, some symbionts assumed to be parasitic might have negligible effects on hosts. This kind of symbionts could be considered as commensals, facultative parasites or facultative mutualists rather than true parasites depend-ing on host condition, the symbiont under study, and the nature of the usually diverse community of symbi-otic organisms (Bronstein 1994). In fact, commensal-ism, where there are neither costs nor benefits to hosts, and mutualism, where both host and symbiont benefit, are common in nature (Thompson 1994) although among birds and their symbionts next to nothing is known about how common they are.
Feather mites are arthropods that live on or in the feathers on birds, and are among the commonest avian ectosymbionts. However, the nature of the ecological interaction between feather mites and birds remains unclear, some studies reporting negative effects of feather mites on their hosts and others reporting positive or no effects. Here we use a large dataset com-prising 20 189 measurements taken from 83 species of birds collected during 22 yr in 151 localities from seven countries in Europe and North Africa to explore the correlation between feather mite abundance and body condition of their hosts. We predicted that, if wing-dwelling feather mites are parasites, a negative correlation with host body condition should be found, while a mutualistic interaction should yield positive correlation. Although negative relationships between feather mite abundance and host body condition were found in a few species of birds, the sign of the correlation was positive in most bird species (69%). The overall effect size was only slightly positive (r 0.066). The effect of feather mite abundance explained 10% of variance in body condition in most species (87%). Results suggest that feather mites are not parasites of birds, but rather that they hold a commensalistic relationship where feather mites may benefit from feeding on uropygial gland secretions of their hosts and birds do not seem to obtain a great benefit from the presence of feather mites.
The distribution of feather mites (Astigmata) along the wing of passerine birds could change dramatically within minutes because of the rapid movement of mites between feathers. However, no rigorous study has answered how fine-tuned is the pattern of distribution of feather mites at a given time. Here we present a multiscale study of the distribution of feather mites on the wing of non-moulting blackcaps Sylvia atricapilla in a short time period and at a single locality. We found that the number and distribution of mites differed among birds, but it was extremely similar between the wings of each bird. Moreover, mites consistently avoided the first secondary feather, despite that it is placed at the centre of the feathers most used by them. Thus, our results suggest that feather mites do precise, feather-level decisions on where to live, contradicting the current view that mites perform “mass”, or “blind” movements across wing feathers. Moreover, our findings indicate that “rare” distributions are not spurious data or sampling errors, but each distribution of mites on the wing of each bird is the outcome of the particular conditions operating on each ambient-bird-feather mite system at a given time. This study indicates that we need to focus on the distribution of feather mites at the level of the individual bird and at the feather level to improve our understanding of the spatial ecology of mites on the wings of birds.
The seasonal change, i.e. the marked differences between seasons of low and high productivity, in the abundance of ectosymbionts and the defence intensity of the host against pathogens is a well defined characteristic of temperate zone organisms. Here we investigate the seasonal variation in the uropygial gland size and the abundance of Proctophyllodes feather mites on the wing feathers of house sparrows Passer domesticus in two breeding populations. The size of the uropygial gland varied significantly in male and female house sparrows over the annual cycle. The gland was small during the non-breeding and mating season, after that it started to grow sharply, reaching its maximum size during breeding. Females had larger gland volumes than males during breeding, and the increase in gland size during breeding was more pronounced in females than in males. The number of feather mites was the lowest during breeding, followed by an increase during moult, and reaching its maximum between the wintering and mating seasons. The absence of a significant relationship between the uropygial gland size and the abundance of feather mites, after controlling for potential confounding variables, supports the view that gland oils do not regulate the number of mites. To investigate further this hypothesis, through a full factorial experimental design we tested the effect of uropygial gland and photoperiod manipulation on the population size and population dynamics of feather mites. The manipulation of uropygial gland had no effect on mites, supporting our observational results. As a result of the experimentally increased day-length, the abundance of feather mites on wing feathers decreased significantly and more sharply than in the control group, supporting the previous anecdotal evidence about the photosensitivity of these organisms. Using photoperiodic cues, feather mites may respond to seasonal changes that affect their life-history and population dynamics.
The moult of birds could greatly perturb the life cycle of feather mites (Astigmata). These mites live on the surface of feathers and are unlikely to survive if they are on one when it is moulted. Therefore, we hypothesized that they would escape to other feathers to avoid this risk of mortality. We analysed the distribution of feather mites on the wings of 63 moulting individuals of 13 species of passerine birds. We used generalized linear mixed models to test whether the distribution of feather mites depends on the stage of moult of feathers. Feather mites were significantly less abundant on the next feather to fall out than on the other feathers. This ability to escape seems to be higher on primaries and secondaries than on tertials. At least on primaries, feather mites avoided not only the next feather to be moulted but also the second one. For primaries and secondaries the new full-grown feathers harboured more feather mites than those still growing. This study shows that feather mites have an escape behaviour from moulting wing feathers in passerine birds that is consistent with a model of adaptive behaviour.
Feather mites (Astigmata) are distributed around the world, living on the feathers of birds, but their mechanisms for transmission among hosts are not fully understood. There is anecdotal evidence of feather mites attached to louseflies (Diptera: Hippoboscidae), suggesting that feather mites may use these flies as a mode of phoretic transmission among birds. Two bird-lousefly associations (alpine swift Apus melba-Crataerina melbae and feral pigeon Columba livia-Pseudolynchia canariensis) were inspected to test the hypothesis that feather mites use hippoboscid flies as major mode of transmission. Both bird species showed a high prevalence and abundance of feather mites and louseflies. However, no feather mites were found attached to the 405 louseflies inspected, although skin mites (Epidermoptidae and Cheyletiellidae) were found on louseflies collected from feral pigeons. This study suggests that feather mites do not use hippoboscid flies as a major mode of transmission among birds.
A process of infecting the chaffinch nestlings Fringilla coelebs with three analgoid feather mites, Analges passerinus L., 1758, Monojoubertia microphylla (Robin, 1877), and Pteronyssoides striatus (Robin, 1977), commonly occurred on this bird species was investigated. 15 nests contained totally 65 nestlings, from 2 to 6 individuals in a brood, have been examined from the day of hatching till 11th day. Observations were held in the neighbourhood of the bird banding station "Rybachy" (Russia, Kaliningrad Province) in June of 1982. Number of mites on alive nestlings taken temporarily from their nest was counted by means of binocular lens under the magnification x12.5 and x25. The nestlings receive the mites from the chaffinch female during the night time, when the female sits together with the young birds and heats them. In the condition of this prolonged direct contact the mites migrate from the female onto the nestlings. As it was shown in our study of seasonal dynamics of mites on the chaffinch (Mironov, 2000), the chaffinch female only gives its mites to young generation and looses about three quarter of its mite micropopulation during the nesting period (June), hile in the chaffinch males the number of mites continues to increase during all summer. The infections with three feather mite species happen in the second part of the nestling's stay in the nest. The starting time of this process, its intensity, and sex and age structure of mite micropopulations on the nestlings just before their leaving the nest are different in the mite species examined. These peculiarities of feather mite species are determined by the biology of examined species, and first of all by their morphological characteristic and specialisation to different microhabitats, i.e. certain structural zones of plumage. Pteronyssoides striatus (Pteronyssidae) is rather typical mite specialised to feathers with vanes. In adult birds with completely developed plumage this species occupies the ventral surface of the big upper coverts of primary flight feathers. This species appears on the chaffinch nestlings in a significant number on 7th day. The mites occupy the basal parts of primary flight feathers represented in that moment by the rods only. They sit on practically open and smooth surface of this microhabitat, which is uncommon for them, because the vanes of the big upper coverts are not yet open and also represented by thin rods. During the period of the last 5 days (from 7 to 11th day) the mean number of mites per one nestling increases from 2.3 +/- 0.5 to 17.1 +/- 1.8 mites. Just before the day, when the nestling leave the nest, the tritonymphs absolutely predominate (82.4%) in the micropopulation of P. striatus. Analges passerinus (Analgidae) is specialised to live in the friable layer formed by numerous not-engaged thread barbles of the down feathers and basal parts of the body covert feathers. Mites have special hooks on legs used for hard attaching to the barbles and for fast moving in the friable layer of feathers. On the chaffinch nestlings, these mites appear usually on 8th day, when the rod-like body covert feathers begin to open on apices and form short brushes; however some individuals occur on the skin of nestlings even on 6th day. The mean number of mites per nestling on the 11th day reaches 16.5 +/- 1.4 individuals. The micropopulation of A. passerinus is represented on the nestlings mainly by the females (45.5%), tritonymphs (23.6%) and males (11.5%). Monojobertia microphylla (Proctophyllodidae) is a typical dweller of feathers with large vanes. Mites of this species commonly occupy the ventral surface of primary and secondary flight feathers and also respective big upper covert feathers of wings. M. microphylla appears on the nestlings in a significant number (7.1 +/- 1.2 mites) on 9th day, only when the primary flight feathers already have short vanes about 10 mm in length. In next three days the number of mites increases very fast and reaches on 11th day 60.3 +/- 5.7 mites per nestling. In the micropopulation of this species, the tritonymphs count 38.3%, and the quota of males and females is 25.3% each. The migration of this species goes most intensively, than in two other species. An analitic selection of logistic curves shows, that the increasing of mite number during the process of infection with three mite species may be most adequately described by the sigmoid curves with clearly recognizable levels of saturation, which can be theoretically reached. Indeed, the number of mite individuals being able to migrate onto the nestlings is limited by their number on a respective chaffinch female. In a contrast, the increasing of plumage indices, for instance the length of flight feathers, has almost linear character during the period of observation. The beginning of mite migration is determined by the development of respective microhabitats in the plumage of nestlings, or at least by the development of certain structure elements of plumage, where mites are able to attach for a while, before that moment, when the nestlings will develop the plumage completely and begin to fly. In three mite species examined, the process of infection was performed by older stages, namely by the imago and/or tritonymphs. This can be explained by two reasons. On the one hand, the older stages are most active in their movement, resistible and able to survive successfully on new host individuals. On the other hand, the older stage are ready for the reproduction or will be ready after one moulting. The older stages of mites can quickly create a large and self-supporting micropopulations on the birds, therefore this strategy ensures a successful subsequent existence of the parasite species. In cases, when mites (A. passerinus, M. microphylla) migrate into the respective microhabitats structurally corresponding to their normal microhabitats on adult birds, the micropopulations of these mite species include a significant or dominant quota of females and males. When the normal microhabitat is not yet formed, feather mites migrate into neighboring structure elements of plumage, where they can survive and wait for the development of normal microhabitat, to which they are well adapted. Therefore, in the case of P. striatus, its micropopulations on the chaffinch nestlings are represented mainly by the tritonymphs.
Parasites are ubiquitous and shape almost every aspect of their hosts, including physiology, behaviour, life histories, the structure of the microbiota, and entire communities. Hence, parasitism is one of the most potent forces in nature and, without parasites, the world would look very different. The book gives an overview over the parasite groups and the diversity of defences that hosts have evolved, such as immune systems. Principles of evolutionary biology and ecology analyse major elements of host–parasite interactions, including virulence, infection processes, tolerance, resistance, specificity, memory, polymorphisms, within-host dynamics, diseases spaces, and many other aspects. Genetics is always one of the key elements in these topics. Modelling, furthermore, can predict best strategies for host and parasites. Similarly, the spread of an infectious disease in epidemiology combines with molecular data and genomics. Furthermore, parasites have evolved ways to overcome defences and to manipulate their hosts. Hosts and parasites, therefore, continuously co-evolve, with changes sometimes occurring very rapidly, and sometimes requiring geological times. Many infectious diseases of humans have emerged from a zoonotic origin, in processes governed by the basic principles discussed in the different sections. Hence, this book integrates different fields to study the diversity of host–parasite processes and phenomena. It summarizes the essential topics for the study of evolutionary parasitology and will be useful for a broad audience.
Understanding host–symbiont networks is a major question in evolutionary ecology. Birds host a great diversity of endo- and ectosymbiotic organisms, with feather mites (Arachnida: Acariformes: Analgoidea, Pterolichoidea) being among the most diverse of avian symbionts. A global approach to the ecology and evolution of bird–feather-mite associations has been hampered because of the absence of a centralized data repository. Here we present the most extensive data set of associations between feather mites and birds. Data include 12 036 records of 1887 feather mite species located on the flight feathers of 2234 bird species from 147 countries. Feather mites typically located inside quills, on the skin, or on downy body feathers are not included. Data were extracted from 493 published sources dating from 1882 to 2015. Data exploration shows that although most continents and bird families are represented, most bird species remain unexplored for feather mites. Nevertheless, this is the most comprehensive data set available for enabling global macroecological analyses of feather mites and their hosts, such as ecological network analyses. This metadata file outlines the structure of these data and provides primary references for all records used.
Obligate symbionts (including parasites, commensals and mutualists) often share host species and host-based food resources. Such symbionts are frequently distributed unequally among hosts with different phenotypic features, or occupy different regions on a host. However, the processes leading to distinct within-host symbiont distributions remain obscure. We aimed to test whether distinct in-host symbiont distributions arise as the outcome of species-specific habitat preferences or interspecific competition, and how host phenotype influences such processes. To this end, we studied the distribution within and among individual bird hosts of two feather mites (Proctophyllodes sylviae and Trouessartia bifurcata) of migratory and sedentary European blackcaps, Sylvia atricapilla, wintering in sympatry. Trouessartia bifurcata was mostly restricted to resident blackcaps, while P. sylviae was abundant on both host types. Within hosts, each species tended to settle on different feather sectors (proximal or distal, respectively), which they filled by spreading on the wing following ordered but opposite patterns, thereby supporting the view that spatial segregation was primarily the outcome of dissimilar space preferences. However, we also found evidence of competition finely tuning mite distributions: when P. sylviae increased abundance and expanded onto the range of T. bifurcata, abundances of the two species were negatively correlated in the shared areas. In addition, the presence of T. bifurcata on a host was associated with a more restricted distribution of P. sylviae. Our results show that both species-specific preferences and interspecific interactions contribute to shaping mite distributions among and on individual hosts, a situation likely mirrored by other host-multi-symbiont systems.
Copyright © 2015. Published by Elsevier Ltd.
Feather mites (Astigmata: Analgoidea, Pterolichoidea) are among the most abundantand commonly occurring bird ectosymbionts. Basic questions on the ecology and evolution of feather mites remain unanswered because feather mite species identification is often only possible for adult males and it is laborious even for specialised taxonomists, thus precluding large-scale identifications. Here, we tested DNA barcoding as a useful molecular tool to identify feather mites from passerine birds. 361 specimens of 72 species of feather mites from 68 species of European passerine birds from Russia and Spain were barcoded. The accuracy of barcoding and mini-barcoding was tested. Moreover, threshold choice (a controversial issue in barcoding studies) was also explored in a new way, by calculating through simulations the effect of sampling effort (in species number and species composition) on threshold calculations. We found one 200 bp mini-barcode region that showed the same accuracy as the full-length barcode (602 bp) and was surrounded by conserved regions potentially useful for group-specific degenerate primers. Species identification accuracy was perfect (100%) but decreased when singletons or species of the Proctophyllodes pinnatus group were included. In fact, barcoding confirmed previous taxonomic issues within the Proctophyllodes pinnatus group. Following an integrative taxonomy approach, we compared our barcode study with previous taxonomic knowledge on feather mites, discovering three new putative cryptic species and validating three previous morphologically different (but still undescribed) new species.
Salmon louse Lepeophtheirus salmonis Kroyer infection levels in both wild sea trout Salmo trutta L. and sentinel Atlantic salmon Salmo salar L. smolts were investigated inside and outside a temporary protected zone with limits on fish farming in the intensively farmed Romsdalsfjord system. Wild sea trout outside the protected zone had higher prevalence and significantly higher abundances than those inside the zone. Furthermore, sentinel caged Atlantic salmon smolts confirmed significant differences in infection pressure: Eresfjord (non-farmed inner part of the protected zone) had the lowest infection risk, a moderate risk was found in Langfjord (intermediately farmed middle part of the protected zone), while Karlsoyfjord (intensively farmed area outside the protected zone) had the highest infection risk. No clear bias between the near-shore and pelagic areas of the fjord were found, although significant differences between pelagic and near-shore cages were occasionally observed. Results show that small sentinel cages can be used as an alternative method to monitor the infection pressure in a fjord system. Overall, our results indicate that wild salmonids may benefit from the protection zone. However, the infection level on wild sea trout inside the temporary protected zone was higher compared to completely farm-free fjords in Norway, and infection levels likely to have a negative physiological impact on wild sea trout were found. This may indicate that the zone is too small to have the necessary protective effect against salmon lice.
Most reports of interactions between feather mites and their avian hosts have assumed that mites have detrimental effects on their hosts, i.e. that they behave as parasites. We investigate the effects of feather mites Gabucinia delibata on the body condition of Red-billed Choughs Pyrrhocorax pyrrhocorax, a highly social, medium-sized corvid species. Feather mites were absent in fledglings al the nest and were probably acquired by Choughs from 1 to 5 months after fledging, when they joined communal roosts. The abundance of feather mites on both wing and tail increased with age and development of social habits in non-breeding Choughs, but decreased when they reached breeding status. Mated Choughs had similar abundances of feather mites. The abundance of mites correlated positively with body condition (computed as the residuals of mass on a ''size factor'') in both males and females, and body condition was in general better for Choughs holding mites than for those lacking mites. The conclusion that feather mites do not have detrimental effects on Choughs was reinforced by the fact that feather mite abundance did not differ between Choughs with normal and crossed bills, respectively, suggesting that preening does not remove mites from the feathers. This particular association thus could be labelled as non-parasitic, suggesting at least a commensal, and possibly a mutualistic relationship. In the latter case, the hypothesised benefits accrued to Chough hosts from their association with mites may derive from an improved feather cleaning, and from the supposed protection against pathogenic organisms achieved primarily by preemption of resources by more benign species, such as feather mites.
Despite considerable research into the mechanisms that lead to the persistence of parasites, the huge diversity of macroparasite transmission strategies observed both within and among species has yet to be explained. This may be because questions of parasite persistence are typically addressed at the population level, even though observed transmission rates are determined by infection events at the level of the individual parasite. To help overcome this disparity, a simple model is developed to explore the optimal infection strategy for a macroparasite under a range of selection pressures. The model calculates the fitness of the parasite by considering explicitly the probability of the individual infective stages surviving and infecting. The optimal strategy is highly sensitive to the rate of host availability and, considering the parasite's fitness, it is often preferable to have sub-maximal infectivity to maximise survival during periods of host absence. An important finding is that when parasites are faced with unpredictable conditions such as the time of host availability, the optimum strategy may be to produce offspring that differ in their infection strategies. By spreading the risk in this way, known as bet hedging, parasites can increase the chances that at least some of their offspring will infect successfully. This potential for variation in infection strategies has not been considered explicitly before and may have wide reaching implications for current epidemiology theory.
Wing feather mite burdens on seven species of passerine birds (Carduelis carduelis– goldfinch; C. chloris– greenfinch; Serinus serinus– serin; Sylvia atricapilla– blackcap; Sylvia melanocephala– Sardinian warbler; Turdus merula– blackbird; Passer domesticus– house sparrow) from Portugal were assessed by the subjective semi-quantitative scoring system of Behnke et al. (1995) in order to evaluate more fully the accuracy and reliability of the technique. Our analysis indicated that in all species, scores allocated to flight feathers showed a significant positive relationship with mite counts as assessed through microscopical examination of the same feathers. However, there were differences between species of birds. Of the species examined, goldfinches and greenfinches showed the weakest relationships between assigned mite scores and actual mite numbers indicating that the technique was less accurate when applied to these species compared with the remaining five. No evidence was found that anything more was to be gained from scoring both wings, rather than just one. Feather mites (Proctophyllodes spp., Trouessartia incisa) were also detected on tail feathers, but the assessment of these feathers presented additional problems and it was concluded that in the interests of minimizing handling time of birds, tail scores had little more to offer. We conclude that scoring all the flight feathers (including all primary, secondary, and tertiary feathers) on one entire wing, but alternating between left and right wings of birds within a species, represents an acceptable compromise between sufficiently detailed examination and minimization of bird handling time in the field.
proportion of the biodiversity of life. Not only do they impact humans and other animals in fundamental ways, but in recent years they have become a powerful model system for the study of ecology and evolution, with practical applications in disease prevention. Here, in a thoroughly revised and updated edition of his influential earlier work, Robert Poulin provides an evolutionary ecologist's view of the biology of parasites. He sets forth a comprehensive synthesis of parasite evolutionary ecology, integrating information across scales from the features of individual parasites to the dynamics of parasite populations and the structuring of parasite communities.Evolutionary Ecology of Parasitespresents an evolutionary framework for the study of parasite biology, combining theory with empirical examples for a broader understanding of why parasites are as they are and do what they do. An up-to-date synthesis of the field, the book is an ideal teaching tool for advanced courses on the subject. Pointing toward promising directions and setting a research agenda, it will also be an invaluable reference for researchers who seek to extend our knowledge of parasite ecology and evolution.
There is limited information about the natural history of the transmission of feather lice (Phthiraptera) from parent birds to their young. This article therefore examines the transmission of 4 species of feather lice from parent blackbirds to their nestlings in an English population, and addresses questions formulated from the perspective of the lice. The lice that disperse onto the several young in the nest were mostly found on the larger chicks, those with higher survival prospects. The lice dispersing to chicks were overwhelmingly nymphs, which cannot be sexed morphologically, and so the prediction that the adult lice dispersing would be disproportionately female, potential founders of a new population, was only supported for the most numerous species, Brueelia merulensis. There was no evidence that louse dispersal to chicks was density dependent and more likely when the parents were more heavily infested. Finally, I predicted that lice might aggregate on female blackbirds, which undertake more brooding, to increase their chance of transmission to nestlings. For 1 louse species, B. merulensis, prevalence, but not louse intensity, was higher on female than male blackbirds. For 2 other louse species, Philopterus turdi and Menacanthus eurysternus, no differences between male and female blackbirds were detected.
Competition-colonization trade-off models explain the coexistence of competing species in terms of a trade-off between competitive ability and the ability to colonize competitor-free patches of habitat. A simple prediction of these models is that inferior competitors will be superior dispersers. This prediction has seldom been tested in natural populations because measuring dispersal is difficult. Journal Article
Theory suggests that the evolution of parasite virulence is linked to the dynamics of parasite transmission. All else being equal, parasites transmitted vertically from parents to offspring should be less virulent than parasites capable of horizontal transmission to unrelated hosts. This is because the fitness of vertically transmitted parasites is tightly linked to the reproductive success of the host, whereas the fitness of horizontally transmitted parasites is relatively independent of host reproduction. The virulence-transmission relation has seldom been tested because of difficulties inherent in comparing virulences of different parasite-host systems. We compared the virulence of lice and mites infesting a single group of captive rock doves (Columba livia). Lice, which were vertically transmitted, had no detectable effect on host fitness, whereas horizontally transmitted mites drove host reproductive success to zero. These results, in conjunction with a survey of the literature, support the hypothesis that ectoparasite virulence is linked to the mode of transmission.
Frequency distributions from 49 published wildlife host-macroparasite systems were analysed by maximum likelihood for goodness of fit to the negative binomial distribution. In 45 of the 49 (90%) data-sets, the negative binomial distribution provided a statistically satisfactory fit. In the other 4 data-sets the negative binomial distribution still provided a better fit than the Poisson distribution, and only 1 of the data-sets fitted the Poisson distribution. The degree of aggregation was large, with 43 of the 49 data-sets having an estimated k of less than 1. From these 49 data-sets, 22 subsets of host data were available (i.e. host data could be divided by either host sex, age, where or when hosts were sampled). In 11 of these 22 subsets there was significant variation in the degree of aggregation between host subsets of the same host-parasite system. A common k estimate was always larger than that obtained with all the host data considered together. These results indicate that lumping host data can hide important variations in aggregation between hosts and can exaggerate the true degree of aggregation. Wherever possible common k estimates should be used to estimate the degree of aggregation. In addition, significant differences in the degree of aggregation between subgroups of host data, were generally associated with significant differences in both mean parasite burdens and the prevalence of infection.
Ectoparasites play important roles in the lives of birds. Among these parasites, mites offer unique potential because of their extraordinary ecological and evolutionary diversity. However, the basic biology of most mites is poorly understood, and misleading extrapolations are sometimes made from better studied systems involving lice and fleas. Most importantly, not all bird-associated mites are parasitic; indeed, recent research suggests that some might even be beneficial. Here, we summarize what is known about the diversity of bird-mite relationships, and highlight how mites provide an ideal tool for the study of host life histories, sexual selection, immunocompetence and cospeciation.
Dispersal of avian ectoparasites can occur through either vertical transmission from adult birds to their offspring in the nest or through horizontal transmission between adult birds or through phoresy. In this study, we investigated the importance of the 2 main transmission modes in the colonial European bee-eater and examined whether individual differences in ectoparasite intensity exist in relation to age, sex, and morphological features of the birds. The intensity of 3 chewing lice species was investigated. Almost all adult bee-eaters (98.3%, n = 176) were infested with 1 of the 3 ectoparasite species, whereas only 10.8% (n = 167) of all chicks were infested. Meropoecus meropis was the most frequent ectoparasite species on adult bee-eaters (prevalence 94.3%), whereas Meromenopon meropis was the most common species on chicks (prevalence 9.6%). Our results suggest that chewing lice are mainly horizontally transmitted among adult bee-eaters and mainly among pair members, whereas vertical transmission between parents and nestlings is less frequent. These conclusions were supported by a relation in ectoparasite intensity of pair members and a parasite removal experiment. Ectoparasite intensity was in general low in nestlings and did not correlate with ectoparasite intensity of their parents. Host age, sex, weight, and other morphological features did not explain variation in chewing lice infestation.
Birds host many lineages of symbiotic mites, but the greatest diversity is shown by the three superfamilies of astigmatan feather mites: Analgoidea, Pterolichoidea, and Freyanoidea. Members of this diphyletic grouping have colonized all parts of the avian integument from their ancestral nidicolous habitat. Whereas some clearly feed on feather pith or skin, acting as parasites, other feather mites are paraphages and consume feather oils without causing structural damage. Sexual dimorphism in feather mites is often extreme, and little is known of the function of many elaborate male structures. Abundance and location of vane-dwelling mites is affected by season, temperature, light, humidity, and host body condition. Because transmission between hosts usually depends on host body contact, it is unsurprising that feather mite phylogeny often parallels host phylogeny; however, recent cladistic analyses have also found evidence of host-jumping and "missing the boat" in several mite lineages.
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Feather mites (Acari: Astigmata) and body condition of their avian hosts: a large correlative study
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