Energy input, habitat heterogeneity and host specificity drive avian haemosporidian diversity at continental scales.

The correct identification of variables affecting parasite diversity and assemblage composition at different spatial scales is crucial for understanding how pathogen distribution responds to anthropogenic disturbance and climate change. Here, we used a database of avian haemosporidian parasites to test how the taxonomic and phylogenetic diversity and phylogenetic structure of the genera Plasmodium, Haemoproteus and Leucocytozoon from three zoogeographic regions are related to surrogate variables of Earth's energy input, habitat heterogeneity (climatic diversity, landscape heterogeneity, host richness and human disturbance) and ecological interactions (resource use), which was measured by a novel assemblage-level metric related to parasite niche overlap (degree of generalism). We found that different components of energy input explained variation in richness for each genus. We found that human disturbance influences the phylogenetic structure of Haemoproteus while the degree of generalism explained richness and phylogenetic structure of Plasmodium and Leucocytozoon genera. Furthermore, landscape attributes related to human disturbance (human footprint) can filter Haemoproteus assemblages by their phylogenetic relatedness. Finally, assembly processes related to resource use within parasite assemblages modify species richness and phylogenetic structure of Plasmodium and Leucocytozoon assemblages. Overall, our study highlighted the genus-specific patterns with the different components of Earth's energy budget, human disturbances and degree of generalism.

The influence of humidity and temperature on the vertical richness and abundance of blood-sucking flies (Culicidae and Ceratopogonidae) in a montane cloud forest in Mexico.

Because the vertical distribution and diversity of blood-sucking flies are poorly known, we determined the diversity, structure, and composition of culicids between vertical vegetation strata. We evaluated the influence of microclimatic variables during different times of the day over a year. We used eight CDC traps baited with CO2 at a height of 1.5 m and 12-15 m. We conducted rank-abundance curves, similarity analysis (ANOSIM and SIMPER), and multivariate clustering with incidence and abundance data. We used GAM models to analyze the influence of strata (understory vs canopy), humidity, and temperature on insect richness and abundance. During the day, the difference between strata was mainly due to higher abundance of Wyeomyia arthrostigma and Wyeomyia ca. adelpha in the understory. During the night, the differences were mainly due to higher abundance of Culex stigmatosoma, Culex salinarius, and Aedes allotecnon in the canopy, and Wyeomyia arthrostigma in the understory. Seasonality played a role in the similarity between the strata. Diversity during the day was positively related to humidity and temperature, and nocturnal diversity increased with temperature but decreased with higher humidity. The effects of environmental factors on the spatiotemporal distribution of fly species are essential for epidemiological surveillance.

Climate predictors and climate change projections for avian haemosporidian prevalence in Mexico.

Long-term, inter-annual and seasonal variation in temperature and precipitation influence the distribution and prevalence of intraerythrocytic haemosporidian parasites. We characterized the climatic niche behind the prevalence of the three main haemosporidian genera (Haemoproteus, Plasmodium and Leucocytozoon) in central-eastern Mexico, to understand their main climate drivers. Then, we projected the influence of climate change over prevalence distribution in the region. Using the MaxEnt modelling algorithm, we assessed the relative contribution of bioclimatic predictor variables to identify those most influential to haemosporidian prevalence in different avian communities within the region. Two contrasting climate change scenarios for 2070 were used to create distribution models to explain spatial turnover in prevalence caused by climate change. We assigned our study sites into polygonal operational climatic units (OCUs) and used the general haemosporidian prevalence for each OCU to indirectly measure environmental suitability for these parasites. A high statistical association between global prevalence and the bioclimatic variables 'mean diurnal temperature range' and 'annual temperature range' was found. Climate change projections for 2070 showed a significant modification of the current distribution of suitable climate areas for haemosporidians in the study region.

Haemosporidian prevalence, parasitaemia and aggregation in relation to avian assemblage life history traits at different elevations.

The transmission of vector-borne protozoa such as parasites of the Order Haemosporida is dependent on both biotic and abiotic factors such as host life history traits and environmental conditions. This study aimed to identify the variables that determine haemosporidian prevalence, parasitaemia and aggregation within the context of elevation and avian life history traits in Central Veracruz, Mexico. We sampled 607 birds from 88 species; we used microscopy and the mtDNA cytochrome b gene to detect parasites. We found an overall prevalence of 32.3%. Haemosporidian prevalence was 21.6% in tropical sub-deciduous forest (at sea level), 38% in tropical deciduous forest (265 m above sea level (asl)), 19.4% in montane cloud forest (1630 m asl), and 51.7% in pine-oak forest (2790 m asl). The prevalence of each parasite genus was strongly influenced by elevation (a proxy of habitat type). Plasmodium showed the highest prevalence at low elevation. Haemoproteus increased in prevalence with elevation. Leucocytozoon displayed the highest prevalence at the highest elevation (pine-oak forest). Haemoproteus spp. and Leucocytozoon spp. prevalences were higher in open cup than in closed nests. Haemoproteus prevalence and haemosporidian parasitaemia were lower in solitary birds than birds with pairing and gregarious behavior. Haemosporidian aggregation decreased with elevation, yielding the significantly lowest values at the pine-oak forest. Elevation distribution patterns of prevalence for each genus were similar to those previously reported in other geographical areas (e.g., South America, Europe).

The urban contrast: A nationwide assessment of avian diversity in Mexican cities.

In this study we focused on urban bird diversity across Mexico, a megadiverse country, with a special focus on the relative role of urban greenspaces and heavily-built sites. We considered a country-wide approach, including 24 different sized Mexican cities. Our aims were to describe the urban bird diversity in focal cities and further assess the relationships between it and the biogeographic region where cities are located, their size, elevation, and annual rainfall. Additionally, we evaluated differences in the functional composition of bird communities in both studied urban scenarios (i.e., urban greenspaces, heavily-built sites). Our results confirm that urban greenspaces are home to a large proportion of species when contrasted with heavily-built sites. While total species richness and species richness of greenspaces were related with the cities' biogeographic region -with higher species richness in the Neotropical region and Transition Zone-, the relationship did not hold true in heavily-built sites. We found that annual rainfall was negatively related to bird richness in heavily-built sites, suggesting that species from arid systems can be more tolerant to urbanization. Regarding the bird functional group assessment, results show a clear differentiation between the functional groups of greenspaces and those of heavily-built sites, with granivores and omnivores associated with the latter and a highly diverse array of functional groups associated with urban greenspaces.

Within-Lineage Divergence of Avian Haemosporidians: A Case Study to Reveal the Origin of a Widespread Haemoproteus Parasite.

Avian haemosporidian parasites are particularly diverse and widespread. To date, more than 3,000 distinct cytochrome b lineages have been recorded, of which some present extremely wide geographical distributions, even including multiple continents. Whether these isolates represent one or several cryptic species remains unknown. Here we carried out a case study of SISKIN1, a common haemosporidian parasite lineage belonging to the morphologically described species Haemoproteus tartakovskyi. To shed light on its evolutionary origin, we investigated the divergence between SISKIN1 isolates obtained from siskins and redpolls in Europe (Russia and Sweden) and house finches in North America (Mexico). First, we used sequence capture of a small data set (2 Russian isolates and 1 Mexican isolate) to investigate the genetic structure based on the full-length mitochondrial genome and ∼1,000 genes. The mitochondrial genomes of Russian isolates were identical with each other but differed from the Mexican one at 6 positions. The nuclear divergence between Russian and Mexican isolates was on average 2.8%, close to what has been observed between 2 species of malaria parasites that respectively infect humans (Plasmodium falciparum) and gorillas (Plasmodium praefalciparum). Second, we used the expanded data set (15 samples in total) to investigate the genetic structure in 3 genes known to be involved in host invasion. The European isolates were identical across all sequenced genes, whereas the Mexican isolates were highly diverse. The lack of shared alleles between European and Mexican populations suggests that they might have diverged in isolation without gene flow. From the MalAvi database we examined the lineages most similar to the SISKIN1 barcode fragment (part of the cyt b gene) and found that most of them had been recorded in North and South America. This suggests that the lineage SISKIN1 originated in North America and subsequently spread to Europe. Our analyses support that the cyt b gene barcoding region is a useful marker for identification of avian haemosporidian lineages that can classify them into clusters of closely related parasites, but to further investigate species limits and evolutionary history, molecular data from multiple faster-evolving genes are required.

Arsenic and lead contamination in soil and in feathers of three resident passerine species in a semi-arid mining region of the Mexican plateau.

The current study aimed at quantifying arsenic and lead in feathers from three passerine species that are residents from areas exposed to mining activities (Toxostoma curvirostre, Campylorhynchus brunneicapillus, and Melozone fusca). Lead and As contents in bird feathers and in superficial soil samples were measured with AAS. Levels of these metals were compared between sites exposed and unexposed to mining. Possible correlations of As and Pb between superficial soil and bird feathers were also investigated. Soil metal concentrations were significantly higher near mining sites, and metal concentrations in bird feathers showed a behavior similar to those recorded for soil samples. Individual birds from polluted sites had higher mean feather metal concentrations in comparison with non-polluted sites; no differences in metal concentrations were recorded among bird species. This work constitutes a basis for monitoring contaminants, and for future toxicological studies attempting to understand the impact that some mining activities may have on bird populations.

Haemosporidian parasite prevalence, parasitemia, and diversity in three resident bird species at a shrubland dominated landscape of the Mexican highland plateau.

BACKGROUND: Studies of avian haemosporidians allow understanding how these parasites affect wild bird populations, and if their presence is related to factors such as habitat loss, degradation and fragmentation, and climate change. Considering the importance of the highland Plateau of Mexico as part of the North American bird migratory route and as a region containing important habitat for numerous bird species, the purpose of this study was to document haemosporidian species richness and how habitat degradation, bird body condition, and distance from water sources correlate with bird parasitemia. METHODS: We assessed the presence of avian haemosporidians in three resident bird species through microscopy and PCR amplification of a fragment of the haemosporidian cytochrome b gene. Average parasitemia was estimated in each species, and its relationship with habitat degradation through grazing, bird body condition and distance from water bodies was assessed. RESULTS: High levels of parasitemia were recorded in two of the three bird species included in this study. Four lineages of haemosporidians were identified in the study area with nearly 50 % prevalence. Areas with highly degraded shrublands and villages showed higher parasitemia relative to areas with moderately degraded shrublands. No strong relationship between parasitemia and distance from water bodies was observed. There were no significant differences in prevalence and parasitemia between the two bird species infected with the parasites. Two of the sequences obtained from the fragments of the parasite's cytochrome b gene represent a lineage that had not been previously reported. CONCLUSIONS: Haemosporidian diversity in arid zones of the Mexican highland plateau is high. Shrubland habitat degradation associated to the establishment of small villages, as well as tree extraction and overgrazing in the surroundings of these villages, significantly enhances parasitemia of birds by haemosporidians.

Ecophysiological and anatomical mechanisms behind the nurse effect: which are more important? A multivariate approach for cactus seedlings.

BACKGROUND: Cacti establish mostly occurs under the canopy of nurse plants which provide a less stressful micro-environment, although mechanisms underlying this process are unknown. The impact of the combination of light and watering treatments on Opuntia streptacantha (Cactaceae) seedlings was examined. METHODS/PRINCIPAL FINDINGS: Ecophysiological [titratable acidity, osmotic potential ('solute potential', Ψs ), relative growth rate (RGR) and their components (NAR, SLA, and LWR)], anatomical (chloroplast density, chloroplast frequency, and cell area), and environmental [photosynthetic photon flux density (PPFD) and air temperature] sets of variables were analyzed, assessing relationships between them and measuring the intensity of the relationships. Three harvests were carried out at days 15, 30, and 45. Ψs and acidity content were the most important responses for seedling establishment. The main anatomical and environmental variables were chloroplast density and water availability, respectively. Opuntia streptacantha seedlings establish better in the shade-watering treatment, due to higher Ψs and acidity, unaffected chloroplasts, and lower PPFD. In addition, the chloroplasts of cells under high-light and non-watering treatment were clumped closer to the center of the cytosol than those under shade-drought, to avoid photoinhibition and/or to better distribute or utilize the penetrating light in the green plant tissue. CONCLUSIONS: Opuntia seedlings grow better under the shade, although they can tolerate drought in open spaces by increasing and moving chloroplasts and avoiding drastic decreases in their Ψs . This tolerance could have important implications for predicting the impact of climate change on natural desert regeneration, as well as for planning reforestation-afforestation practices, and rural land uses.

Blood lead concentrations in wild birds from a polluted mining region at Villa de La Paz, San Luis Potosi, Mexico.

This investigation was undertaken to determine the concentrations of lead in bird blood samples from a mining region in central Mexico and to compare concentrations among several different feeding guilds. The study took place in the Mexican state of San Luis Potosi in a region known as "Villa de la Paz." This is one of the most intensely exploited mining regions in central Mexico and has been actively mined for over four centuries. Lead concentrations from bird blood samples taken from four polluted sites were significantly higher than those from a control, unpolluted site (F = 6.3, P < 0.0002). Similarly, mean blood lead concentrations in birds from a highly polluted site were higher than those from a site that has intermediate pollution levels (P < 0.05). In addition, samples from insectivorous birds had significantly lower lead concentrations compared to granivores, frugivores-insectivores, and omnivores (F = 4.86, P = 0.004), and a large proportion of all individuals had blood lead concentrations indicative of low, sub-lethal toxic effects. Finally, in two polluted sites, remarkably small numbers of insectivore-frugivores, and granivores were trapped, and in one polluted site a large number of insectivores was trapped (X(2) = 29.9, P = 0.03), and no differences in proportions of migrants and non-migrants were found among sampling sites (X(2) = 0.6, P = 0.96). To date, it has not been determined to what extent constant exposure to these levels of pollution can influence health at the individual level, lifespan, and, therefore, population demography of birds from this region.