Bird hosts, blood parasites and their vectors--associations uncovered by molecular analyses of blackfly blood meals

The level of host specificity of blood-sucking invertebrates may have both ecological and evolutionary implications for the parasites they are transmitting. We used blood meals from wild-caught blackflies for molecular identification of parasites and hosts to examine patterns of host specificity and how these may affect the transmission of avian blood parasites of the genus Leucocytozoon . We found that five different species of ornithophilic blackflies preferred different species of birds when taking their blood meals. Of the blackflies that contained avian blood meals, 62% were infected with Leucocytozoon parasites, consisting of 15 different parasite lineages. For the blackfly species, there was a significant association between the host width (measured as the genetic differentiation between the used hosts) and the genetic similarity of the parasites in their blood meals. The absence of similar parasite in blood meals from blackflies with different host preferences is interpreted as a result of the vector–host associations. The observed associations between blackfly species and host species are therefore likely to hinder parasites to be transmitted between different host-groups, resulting in ecologically driven associations between certain parasite lineages and hosts species.     

An analysis of hatching success in the great reed warbler Acrocephalus arundinaceus

Hatching success is a potentially important fitness component for avian species. Previous studies of hatching success in natural populations have primarily focused on effects of inbreeding but a general understanding of variation in hatching success is lacking. We analyse data on hatching success in a population of great reed warblers Acrocephalus arundinaceus in Lake Kvismaren in south central Sweden. The effects of a range of covariates, including three measures of inbreeding as well as effects of classifications in the data (such as identities of individuals), on hatching success are analysed simultaneously. This is done by means of fitting Bayesian binomial mixed models using Markov chain Monte Carlo methods. Using random effects for each individual parent we check for unexplained variation in hatching success among male and female individuals and compare it to effects of covariates such as degree of inbreeding. Model selection showed that there was a significant amount of unexplained variation in hatching probability between females. This was manifested by a few females laying eggs with a substantially lower hatching success than the majority of the females. The deviations were of the same order of magnitude as the significant effect of parent relatedness on hatching success. Whereas the negative effect of parent relatedness on hatchability is an expression of inbreeding, the female individual effect is not due to inbreeding and could reflect maternal effects, that females differ in fertilisation and/or incubation ability, or an over representation of genetic components from the female acting on the early developing embryo.     

Cross-species testing of 27 pre-existing microsatellites in Podarcis gaigeae and Podarcis hispanica (Squamata: Lacertidae)

We tested 27 microsatellite loci for cross-species amplification in the lacertids Podarcis gaigeae and Podarcis hispanica. We detected 11 and 15 polymorphic loci in the former and the latter species, respectively. In a larger sample of individuals from a single population of each species, the number of alleles ranged from five to 23 in 10 of the polymorphic loci in P. gaigeae, and between four and 13 in nine of polymorphic loci in P. hispanica. Two locus deviated from Hardy-Weinberg equilibrium in P. hispanica. Between 11 and 16 of the 27 loci also amplified successfully in three other Podarcis species.     

Postglacial colonisation patterns and the role of isolation and expansion in driving diversification in a passerine bird

Pleistocene glacial cycles play a major role in diversification and speciation, although the relative importance of isolation and expansion in driving diversification remains debated. We analysed mitochondrial DNA sequence data from 15 great reed warbler (Acrocephalus arundinaceus) populations distributed over the vast Eurasian breeding range of the species, and revealed unexpected postglacial expansion patterns from two glacial refugia. There were 58 different haplotypes forming two major clades, A and B. Clade A dominated in Western Europe with declining frequencies towards Eastern Europe and the Middle East, but showed a surprising increase in frequency in Western and Central Asia. Clade B dominated in the Middle East, with declining frequencies towards north in Central and Eastern Europe and was absent from Western Europe and Central Asia. A parsimonious explanation for these patterns is independent postglacial expansions from two isolated refugia, and mismatch distribution analyses confirmed this suggestion. Gene flow analyses showed that clade A colonised both Europe and Asia from a refugium in Europe, and that clade B expanded much later and colonised parts of Europe from a refugium in the Middle East. Great reed warblers in the eastern parts of the range have slightly paler plumage than western birds (sometimes treated as separate subspecies; A. a. zarudnyi and A. a. arundinaceus, respectively) and our results suggest that the plumage diversification took place during the easterly expansion of clade A. This supports the postglacial expansion hypothesis proposing that postglacial expansions drive diversification in comparatively short time periods. However, there is no indication of any (strong) reproductive isolation between clades and our data show that the refugia populations became separated during the last glaciation. This is in line with the Pleistocene speciation hypothesis invoking that much longer periods of time in isolation are needed for speciation to occur.     

Heritability of dispersal in the great reed warbler

Dispersal is commonly considered to be a condition‐dependent behaviour with no or low heritability. Here, we show that dispersal in the great reed warbler (Acrocephalus arundinaceus) has a high heritability. Analyses of capture–recapture data of male great reed warblers gathered from the species’ whole Swedish breeding range revealed a remarkable offspring–parent resemblance in dispersal behaviour (philopatry vs. inter‐population dispersal). Also, the degree of dispersal differed between cohorts, which shows that dispersal was partly conditionally dependent. The offspring to mid‐parent estimate of heritability was 0.50. In a previous study of the same data set of male offspring, we did not detect associations between dispersal and several relevant environmental, parental and offspring condition factors. Thus, our results indicate that variation in dispersal partly has a genetic basis in great reed warblers.     

Male‐biased gene flow across an avian hybrid zone: evidence from mitochondrial and microsatellite DNA

Mating pattern and gene flow were studied in the contact zone between two morphologically very similar Chiffchaff taxa (Phylloscopus collybita, P. brehmii) in SW France and northern Spain. Mating was assortative in brehmii, but not in collybita. Mixed matings were strongly asymmetric (excess of collybita male × brehmii female pairs), but did produce viable offspring in some cases. Sequence divergence of the mitochondrial cytochrome b gene was 4.6%. Haplotypes segregated significantly with phenotype (only five ‘mismatches’ among 94 individuals), demonstrating that mitochondrial gene flow was very restricted. The estimated proportion of F₁ hybrids in the reproductive population was significantly lower than expected under a closed population model, indicating strong selection against hybrids. Genetic typing of 101 individuals at four microsatellite loci also showed significant population differentiation, but nuclear gene flow was estimated to be 75 times higher than mitochondrial gene flow. This strong discrepancy is probably due to unisexual hybrid sterility (Haldane’s rule). Thus, there is a strong, but incomplete, reproductive barrier between these taxa.     

The Large-billed Reed Warbler Acrocephalus orinus revisited

The Large-billed Reed Warbler Acrocephalus orinus is known only from the type specimen, collected in Himachal Pradesh, India, in 1867. The specimen is poorly prepared, and it has been suggested that it could represent an isolated form of the Clamorous Reed Warbler A. stentoreus or an aberrant Blyth's Reed Warbler A. dumetorum . We tested the affinity of A. orinus by (1) re-examining the morphology of the type specimen and (2) amplifying and sequencing a portion of its mitochondrial cytochrome b gene. Both the morphological and the mitochondrial analyses showed the specimen to be similar to dumetorum , but distinct enough to qualify as a species of its own. Relative to dumetorum , it has a more rounded wing, longer bill, longer and more graduated tail with more pointed tail feathers, and larger claws. The divergence in mitochondrial DNA between orinus and dumetorum was 7.8%, well above the value expected between subspecies. A. orinus is smaller than any of the forms of A. stentoreus or the related Australian Reed Warbler A. australis . It has a somewhat longer first primary, more pointed tail feathers and paler, less robust feet and claws. DNA comparison places it in the clade of small unstreaked Acrocephalus warblers, and apart from the clade of large unstreaked warblers that contains stentoreus and australis .     

Stereoisomeric flavour compounds XLV: Structure analysis of 2-alkoxy-5-alkyl-tetrahydrofurans

The synthesis of several 2-alkoxy-5-alkyl-tetrahydrofurans is of interest in our investigations of structure–function relationships of chiral flavour compounds. For the preparation of the enantiomeric acetals the unambiguous configurational assignment of the cis and trans series of these compounds is indispensable. By means of crystalline acetal derivatives the absolute structure of a model compound in the cis and the trans configuration is revealed by X-ray measurement and correlated with the corresponding cis and trans configurated aroma compounds. The first complete structure elucidation of the class of 2-alkoxy-5-alkyltetrahydrofurans has been carried out.     

A peroxisome proliferator-activated receptor alpha/gamma dual agonist with a unique in vitro profile and potent glucose and lipid effects in rodent models of type 2 diabetes and dyslipidemia

LSN862 is a novel peroxisome proliferator-activated receptor (PPAR)alpha/gamma dual agonist with a unique in vitro profile that shows improvements on glucose and lipid levels in rodent models of type 2 diabetes and dyslipidemia. Data from in vitro binding, cotransfection, and cofactor recruitment assays characterize LSN862 as a high-affinity PPARgamma partial agonist with relatively less but significant PPARalpha agonist activity. Using these same assays, rosiglitazone was characterized as a high-affinity PPARgamma full agonist with no PPARalpha activity. When administered to Zucker diabetic fatty rats, LSN862 displayed significant glucose and triglyceride lowering and a significantly greater increase in adiponectin levels compared with rosiglitazone. Expression of genes involved in metabolic pathways in the liver and in two fat depots from compound-treated Zucker diabetic fatty rats was evaluated. Only LSN862 significantly elevated mRNA levels of pyruvate dehydrogenase kinase isozyme 4 and bifunctional enzyme in the liver and lipoprotein lipase in both fat depots. In contrast, both LSN862 and rosiglitazone decreased phosphoenol pyruvate carboxykinase in the liver and increased malic enzyme mRNA levels in the fat. In addition, LSN862 was examined in a second rodent model of type 2 diabetes, db/db mice. In this study, LSN862 demonstrated statistically better antidiabetic efficacy compared with rosiglitazone with an equivalent side effect profile. LSN862, rosiglitazone, and fenofibrate were each evaluated in the humanized apoA1 transgenic mouse. At the highest dose administered, LSN862 and fenofibrate reduced very low-density lipoprotein cholesterol, whereas, rosiglitazone increased very low-density lipoprotein cholesterol. LSN862, fenofibrate, and rosiglitazone produced maximal increases in high-density lipoprotein cholesterol of 65, 54, and 30%, respectively. These findings show that PPARgamma full agonist activity is not necessary to achieve potent and efficacious insulin-sensitizing benefits and demonstrate the therapeutic advantages of a PPARalpha/gamma dual agonist.