Vector-Borne Blood Parasites of the Great-Tailed Grackle (Quiscalus mexicanus) in East-Central Texas, USA.

Great-tailed grackles (Quiscalus mexicanus) have dramatically expanded into North America over the past century. However, little is known about the blood that parasites they support. Here, for the first time, we document an assemblage of trypanosome, haemosporida, and filarial nematodes co-circulating in invasive great-tailed grackles. Between February and July, 2015, 61 individuals were captured in an urban environment of College Station, Texas. Field microscopy and molecular diagnostics indicate that 52% (24/46) were visually infected with filarioid nematodes, 24% (11/46) with avian trypanosomes, and 73% (n = 44/60) with haemosporida parasites, such as Haemoproteus (Parahaemoproteus) and Plasmodium cathemerium. Overall, 87% of great-tailed grackles were infected with blood parasites. Although 50% of individuals hosted parasites from multiple phylum, no patterns of parasite assembly were observed. Results indicate that great-tailed grackles can support a relatively high level of blood parasitism. However, the consequences for avian health remain to be determined.

Host associations and turnover of haemosporidian parasites in manakins (Aves: Pipridae).

Parasites of the genera Plasmodium and Haemoproteus (Apicomplexa: Haemosporida) are a diverse group of pathogens that infect birds nearly worldwide. Despite their ubiquity, the ecological and evolutionary factors that shape the diversity and distribution of these protozoan parasites among avian communities and geographic regions are poorly understood. Based on a survey throughout the Neotropics of the haemosporidian parasites infecting manakins (Pipridae), a family of Passerine birds endemic to this region, we asked whether host relatedness, ecological similarity and geographic proximity structure parasite turnover between manakin species and local manakin assemblages. We used molecular methods to screen 1343 individuals of 30 manakin species for the presence of parasites. We found no significant correlations between manakin parasite lineage turnover and both manakin species turnover and geographic distance. Climate differences, species turnover in the larger bird community and parasite lineage turnover in non-manakin hosts did not correlate with manakin parasite lineage turnover. We also found no evidence that manakin parasite lineage turnover among host species correlates with range overlap and genetic divergence among hosts. Our analyses indicate that host switching (turnover among host species) and dispersal (turnover among locations) of haemosporidian parasites in manakins are not constrained at this scale.

Species formation by host shifting in avian malaria parasites.

The malaria parasites (Apicomplexa: Haemosporida) of birds are believed to have diversified across the avian host phylogeny well after the origin of most major host lineages. Although many symbionts with direct transmission codiversify with their hosts, mechanisms of species formation in vector-borne parasites, including the role of host shifting, are poorly understood. Here, we examine the hosts of sister lineages in a phylogeny of 181 putative species of malaria parasites of New World terrestrial birds to determine the role of shifts between host taxa in the formation of new parasite species. We find that host shifting, often across host genera and families, is the rule. Sympatric speciation by host shifting would require local reproductive isolation as a prerequisite to divergent selection, but this mechanism is not supported by the generalized host-biting behavior of most vectors of avian malaria parasites. Instead, the geographic distribution of individual parasite lineages in diverse hosts suggests that species formation is predominantly allopatric and involves host expansion followed by local host-pathogen coevolution and secondary sympatry, resulting in local shifting of parasite lineages across hosts.

Thermal stability and muscle efficiency in hovering orchid bees (Apidae: Euglossini).

To test whether variation in muscle efficiency contributes to thermal stability during flight in the orchid bee, Euglossa imperialis, we measured CO2 production, heat loss and flight kinematics at different air temperatures (Ta). We also examined the relationship between wingbeat frequency (WBF) and Ta in five additional species of orchid bees. Mean thoracic temperature (Tth) for Eg. imperialis hovering in a screened insectary and in the field was 39.3+/-0.77 degrees C (mean +/- 95% C.I.), and the slope of Tth on Ta was 0.57. Head and abdominal temperature excess ratios declined with Ta, indicating that Eg. imperialis were not increasing heat dissipation from the thorax at high Ta. Elevation of Tth above Ta was correlated with WBF, but Tth alone was not. Estimates of heat production from both respirometry and heat loss experiments decreased 33% as Ta rose from 24 to 34 degrees C. Mean muscle efficiency over this temperature range was 18% assuming perfect elastic energy storage and 22% assuming zero elastic energy storage. Both efficiency estimates increased significantly as Ta rose from 24 to 34 degrees C. In all six species examined, WBF declined significantly with Ta. These data indicate that hovering orchid bees regulate heat production through changes in wingbeat kinematics and consequent changes in energy conversion by the flight motor. Temperature-dependent variation in elastic energy storage or muscle contraction efficiency or both may contribute to the observed trends.