Host personality predicts cuckoo egg rejection in Daurian redstarts Phoenicurus auroreus

In species that are subject to brood parasitism, individuals often vary in their responses to parasitic eggs, with some rejecting the eggs while others do not. While some factors, such as host age (breeding experience), the degree of egg matching and the level of perceived risk of brood parasitism have been shown to influence host decisions, much of the variation remains unexplained. The host personality hypothesis suggests that personality traits of the host influence its response to parasitic eggs, but few studies have tested this. We investigated the relationship between two personality traits (exploration and neophobia) and a physiological trait (breathing rate) of the host, and egg-rejection behaviour in a population of Daurian redstarts Phoenicurus auroreus in northeast China. We first show that exploratory behaviour and the response to a novel object are repeatable for individual females and strongly covary, indicating distinct personality types. We then show that fast-exploring and less neophobic hosts were more likely to reject parasitic eggs than slow-exploring and more neophobic hosts. Variation in breathing rate—a measure of the stress-response—did not affect rejection behaviour. Our results demonstrate that host personality, along the bold-shy continuum, predicts the responses to parasitic eggs in Daurian redstarts, with bold hosts being more likely to reject parasitic eggs.

The disproportionate effect of drift on a hypervariable master regulator of density

Symbiosis is a continuum of long-term interactions ranging from mutualism to parasitism, according to the balance between costs and benefits for the protagonists. The density of endosymbiont density is in both cases a key factor that determines both the transmission of symbiont and the host extended phenotype and is thus tightly regulated within hosts. However, the evolutionary and molecular mechanisms underlying bacterial density regulation are currently poorly understood. In this context, the symbiosis between the fruit fly and its intracellular bacteria Wolbachia (wMelPop strain) is particularly interesting to study. Although vertically-transmitted, the symbiont is pathogenic, and a positive correlation between virulence and wMelPop density is observed. In addition, the number of repeats of a bacterial genomic region -Octomom- varies between individuals, but most likely also within them, and is positively correlated to the Wolbachia density. Such genetic heterogeneity within the host could promote conflicts between partners by increasing within-host competition between symbiont genotypes through a process analogous to the tragedy of the common. To characterize the determinisms at play in the regulation of bacterial density, we first introgressed wMelPop in different genetic backgrounds of D. melanogaster. We found different density levels and Octomom copy numbers in each host lineage, suggesting a host influence on density regulation through Octomom copy number selection. To confirm this hypothesis, we performed new replicated introgressions on the two Drosophila populations that exhibited the most extreme density levels. However, we found no evidence of host influence on density regulation. Instead, we found instability in infection patterns across generations, which rather suggests an influence of drift. Moreover, using reciprocal crosses with the two extreme lineages, we confirmed the absence of host regulation on density levels and Octomom copy number, and a strong influence of drift. We then discuss how drift, both on the symbiont population during transmission and on the host population, could limit the efficiency of selection in such a symbiotic system, and the consequences of drift on the regulation of density and composition of bacterial populations.

Variability of the Sheep Lung Microbiota

ABSTRACTSequencing technologies have recently facilitated the characterization of bacterial communities present in lungs during health and disease. However, there is currently a dearth of information concerning the variability of such data in health both between and within subjects. This study seeks to examine such variability using healthy adult sheep as our model system. Protected specimen brush samples were collected from three spatially disparate segmental bronchi of six adult sheep (age, 20 months) on three occasions (day 0, 1 month, and 3 months). To further explore the spatial variability of the microbiotas, more-extensive brushing samples (n= 16) and a throat swab were taken from a separate sheep. The V2 and V3 hypervariable regions of the bacterial 16S rRNA genes were amplified and sequenced via Illumina MiSeq. DNA sequences were analyzed using the mothur software package. Quantitative PCR was performed to quantify total bacterial DNA. Some sheep lungs contained dramatically different bacterial communities at different sampling sites, whereas in others, airway microbiotas appeared similar across the lung. In our spatial variability study, we observed clustering related to the depth within the lung from which samples were taken. Lung depth refers to increasing distance from the glottis, progressing in a caudal direction. We conclude that both host influence and local factors have impacts on the composition of the sheep lung microbiota.IMPORTANCEUntil recently, it was assumed that the lungs were a sterile environment which was colonized by microbes only during disease. However, recent studies using sequencing technologies have found that there is a small population of bacteria which exists in the lung during health, referred to as the “lung microbiota.” In this study, we characterize the variability of the lung microbiotas of healthy sheep. Sheep not only are economically important animals but also are often used as large animal models of human respiratory disease. We conclude that, while host influence does play a role in dictating the types of microbes which colonize the airways, it is clear that local factors also play an important role in this regard. Understanding the nature and influence of these factors will be key to understanding the variability in, and functional relevance of, the lung microbiota.

Seasonal changes in the infestation parameters of the sucking louse, Linognathoides laeviusculus (Phthiraptera: Anoplura: Polyplacidae), infesting Richardson’s ground squirrel (Rodentia: Sciuridae) in Manitoba, Canada

Linognathoides laeviusculus (Grube) (Phthiraptera: Anoplura: Polyplacidae) is a louse found on holarctic ground squirrels but little is known about how the life history, physiology, and hibernation of the host influence its population dynamics. Two hundred and fourteen Richardson’s ground squirrels (Urocitellus richardsonii (Sabine); Rodentia: Sciuridae) were trapped over the summer of 2010, and the age, sex, and mass of all euthanised squirrels were recorded. Squirrels were hand-washed to remove lice, which were then identified to species, stage of development, and sex. Linognathoides laeviusculus was the only louse collected. In total, 5057 lice were collected with 63.6% of the squirrels infested at a mean intensity of 37.2 (90% confidence interval=29.98–48.66). Two peaks in prevalence of L. laeviusculus infestations occurred (April and mid-June), and one peak in intensity (June). Juvenile squirrels had higher prevalence and mean intensity when compared to adults. Adult male squirrels had higher mean intensity compared to adult females. Adult lice comprised most of the population infesting emerging adult squirrels in the spring but nymphs predominated for most of the active season of the host. Infestations were highly aggregated with k=0.203 and index of discrepancy D=0.813. The seasonal dynamics of L. laeviusculus appear to be strongly correlated with the annual cycle of the squirrel host.