Corticosterone (
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CORT ) is the main glucocorticoid hormone of amphibians, reptiles, birds and some mammals. This hormone may have evolved as an adaptive metabolic mechanism, in part because increased concentrations ofCORT are essential for individuals to manage energy resources and thus cope with negative perturbations such as predation and storms. The benefits ofCORT are offset by costs, because elevated levels can suppress inflammatory responses of individuals, making them more susceptible to parasites and pathogens. In this study, we investigated the relationships between featherCORT levels, infection status and diversity of haemosporidian parasites in the Blue‐crowned ManakinLepidothrix coronata , considering possible effects related to the sex and age of individuals. We predicted higher levels of featherCORT in infected individuals. We observed that featherCORT levels were similar among individuals of different sexes and ages. Although haemosporidian infection status did not vary among sexes, occurrence probability was higher among younger individuals, which may indicate that the less developed immune system of these individuals makes them more susceptible to avian malaria. Contrary to expectations, we found that featherCORT levels were not associated with the infection status and diversity of haemosporidian parasites. That haemosporidian occurrence probability does not increase with elevated featherCORT levels suggests that individuals are not immunosuppressed by elevated levels of this hormone, at least to the extent that featherCORT truly reflects individual differences in the level of this hormone. -
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Hylexetastes woodcreepers are endemic to theterra firme forests of the Amazon basin. Currently, most taxonomic sources recognize two species ofHylexetastes (H. perrotii andH. stresemanni ), each divided into three subspecies. Some authors maintain that theH. perrotii subspecies should be elevated to full species status. In particular,Hylexetastes perrotii brigidai is endemic to the eastern Amazon, the second Amazonian area of endemism (Xingu) most affected by deforestation and habitat degradation. Consequently, the taxonomic status ofH. p. brigidai is of particular concern for conservation. Thus far, only morphological characters have been evaluated for the taxonomic delimitation of species and subspecies ofHylexetastes . We present a molecular phylogenetic analysis of all subspecies to help delimitHylexetastes interspecific limits. Fragments of two mitochondrial (Cytb andND 2) and three nuclear genes (FGB 5, G3PDH andMUSK ) from 57Hylexetastes specimens were sequenced. An ecological niche model was estimated to describe more accurately the potential distributions of taxa and to evaluate their vulnerability to ongoing deforestation. Phylogenetic analyses support the paraphyly of the polytypicH. perrotii as currently delimited and the elevation ofHylexetastes perrotii uniformis to full species rank, as well as the presence of three evolutionary significant units (ESU s) within this newly delimited species, including one grouping allH. p. brigidai specimens. Alternatively, under lineage‐based species concepts, our results support at least five evolutionary species inHylexetastes :H. stresemanni ,H. undulatus ,H. perrotii ,H. uniformis andH. brigidai . Each of these taxa andESU s are distributed in different interfluvial areas of the Amazon basin, which have different degrees of disturbance. Because they occupy the most heavily impacted region among allHylexetastes ESU s, regular assessments of the conservation statuses ofH. p. brigidai and bothH. uniformis ESU s are paramount. -
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Abstract Aim Macroecological analyses provide valuable insights into factors that influence how parasites are distributed across space and among hosts. Amid large uncertainties that arise when generalizing from local and regional findings, hierarchical approaches applied to global datasets are required to determine whether drivers of parasite infection patterns vary across scales. We assessed global patterns of haemosporidian infections across a broad diversity of avian host clades and zoogeographical realms to depict hotspots of prevalence and to identify possible underlying drivers.
Location Global.
Time period 1994–2019.
Major taxa studied Avian haemosporidian parasites (genera
Plasmodium ,Haemoproteus ,Leucocytozoon andParahaemoproteus ).Methods We amalgamated infection data from 53,669 individual birds representing 2,445 species world‐wide. Spatio‐phylogenetic hierarchical Bayesian models were built to disentangle potential landscape, climatic and biotic drivers of infection probability while accounting for spatial context and avian host phylogenetic relationships.
Results Idiosyncratic responses of the three most common haemosporidian genera to climate, habitat, host relatedness and host ecological traits indicated marked variation in host infection rates from local to global scales. Notably, host ecological drivers, such as migration distance for
Plasmodium andParahaemoproteus , exhibited predominantly varying or even opposite effects on infection rates across regions, whereas climatic effects on infection rates were more consistent across realms. Moreover, infections in some low‐prevalence realms were disproportionately concentrated in a few local hotspots, suggesting that regional‐scale variation in habitat and microclimate might influence transmission, in addition to global drivers.Main conclusions Our hierarchical global analysis supports regional‐scale findings showing the synergistic effects of landscape, climate and host ecological traits on parasite transmission for a cosmopolitan and diverse group of avian parasites. Our results underscore the need to account for such interactions, in addition to possible variation in drivers across regions, to produce the robust inference required to predict changes in infection risk under future scenarios.
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Abstract Geographic variation in environmental conditions as well as host traits that promote parasite transmission may impact infection rates and community assembly of vector‐transmitted parasites.
Identifying the ecological, environmental and historical determinants of parasite distributions and diversity is therefore necessary to understand disease outbreaks under changing environments. Here, we identified the predictors and contributions of infection probability and phylogenetic diversity of
Leucocytozoon (an avian blood parasite) at site and species levels across the New World.To explore spatial patterns in infection probability and lineage diversity for
Leucocytozoon parasites, we surveyed 69 bird communities from Alaska to Patagonia. Using phylogenetic Bayesian hierarchical models and high‐resolution satellite remote‐sensing data, we determined the relative influence of climate, landscape, geography and host phylogeny on regional parasite community assembly.Infection rates and parasite diversity exhibited considerable variation across regions in the Americas. In opposition to the latitudinal gradient hypothesis, both the diversity and prevalence of
Leucocytozoon parasites decreased towards the equator. Host relatedness and traits known to promote vector exposure neither predicted infection probability nor parasite diversity. Instead, the probability of a bird being infected withLeucocytozoon increased with increasing vegetation cover (NDVI) and moisture levels (NDWI), whereas the diversity of parasite lineages decreased with increasing NDVI. Infection rates and parasite diversity also tended to be higher in cooler regions and higher latitudes.Whereas temperature partially constrains
Leucocytozoon diversity and infection rates, landscape features, such as vegetation cover and water body availability, play a significant role in modulating the probability of a bird being infected. This suggests that, forLeucocytozoon , the barriers to host shifting and parasite host range expansion are jointly determined by environmental filtering and landscape, but not by host phylogeny. Our results show that integrating host traits, host ancestry, bioclimatic data and microhabitat characteristics that are important for vector reproduction are imperative to understand and predict infection prevalence and diversity of vector‐transmitted parasites. Unlike other vector‐transmitted diseases, our results show thatLeucocytozoon diversity and prevalence will likely decrease with warming temperatures.
