European flyway permeability and abmigration in Teal Anas crecca, an analysis based on ringing recoveries

Abmigration, the switch between flyways, is thought to be frequent in dabbling ducks, and supposedly results from high female philopatry combined with winter pairing: a male pairing in winter with a female from another flyway may follow her to her breeding area and thus abmigrate. On this basis, the frequency of abmigration should be much higher amongst males than amongst females, should increase with time since ringing, and be higher if environmental conditions force birds from different flyways into the same geographical area in winter (in this case the Iberian peninsula in the case of cold spells). Analysing more than 9000 recoveries of Teal ringed in the Camargue, southern France, showed that even with the most conservative flyway definition, 15% of Camargue (Mediterranean flyway) individuals (both males and females) were subsequently recovered in the North-west European flyway. Moving a flyway boundary closer to the Camargue (i.e. to the south-east) increased this percentage to c . 32%. None of the predicted patterns were supported by the data: there was no systematic sex difference in abmigration rate; abmigration showed no consistent increase with time from ringing, and was not significantly more frequent after cold spells. These results suggest that there is permeability between these two flyways for all classes of individuals, which might better be considered as a continuum. This should be taken into account in the development of management and conservation policies for Teal in Europe.     

Evidence of parasite-mediated disruptive selection on genetic diversity in a wild fish population

Identifying the processes maintaining genetic variability in wild populations is a major concern in conservation and evolutionary biology. Parasite-mediated selection may strongly affect genetic variability in wild populations. The inbreeding depression theory predicts that directional selection imposed by parasites should act against the most inbred hosts, thus favouring genetic diversity in wild populations. We have tested this prediction by evaluating the strength and shape of the relationship between the load of a harmful fin-feeder ectoparasite ( Tracheliastes polycolpus ) and the genome-wide genetic diversity (i.e. heterozygosity measured at a set of 15 microsatellites) of its fish host, the rostrum dace ( Leuciscus leuciscus ). Contrary to expectation, we found a nonlinear relationship between host genetic diversity and ectoparasite load, with hosts that were either homozygous or heterozygous harbouring significantly fewer parasites than hosts with an intermediate level of heterozygosity. This relationship suggests that parasites could increase the variance of global heterozygosity in this host population through disruptive selection on genetic diversity. Moreover, when genetic diversity was measured at each locus separately, we found two very strong positive associations between host genetic diversity and the ectoparasite load. This latter result has three main implications: (i) genome-wide effect cannot alone explain the nonlinear relationship between global heterozygosity and ectoparasite load, (ii) negative non-additive allelic interactions (i.e. underdominance) may be a mechanism for resisting ectoparasite infection, and (iii) ectoparasites may favour homozygosity at some loci in this host population.     

Analysis of Australian fur seal diet by pyrosequencing prey DNA in faeces

DNA-based techniques have proven useful for defining trophic links in a variety of ecosystems and recently developed sequencing technologies provide new opportunities for dietary studies. We investigated the diet of Australian fur seals ( Arctocephalus pusillus doriferus ) by pyrosequencing prey DNA from faeces collected at three breeding colonies across the seals' range. DNA from 270 faecal samples was amplified with four polymerase chain reaction primer sets and a blocking primer was used to limit amplification of fur seal DNA. Pooled amplicons from each colony were sequenced using the Roche GS-FLX platform, generating > 20 000 sequences. Software was developed to sort and group similar sequences. A total of 54 bony fish, 4 cartilaginous fish and 4 cephalopods were identified based on the most taxonomically informative amplicons sequenced (mitochondrial 16S). The prevalence of sequences from redbait ( Emmelichthys nitidus ) and jack mackerel ( Trachurus declivis ) confirm the importance of these species in the seals' diet. A third fish species, blue mackerel ( Scomber australasicus ), may be a more important prey species than previously recognised. There were major differences in the proportions of prey DNA recovered in faeces from different colonies, probably reflecting differences in prey availability. Parallel hard-part analysis identified largely the same main prey species as did the DNA-based technique, but with lower species diversity and no remains from cartilaginous prey. The pyrosequencing approach presented significantly expands the capabilities of DNA-based methods of dietary analysis and is suitable for large-scale diet investigations on a broad range of animals.     

Polymorphic microsatellites for the study of newly established populations of the gastropod Cyclope neritea

Both human‐mediated introductions and climatic changes may promote the settlement of species in new areas outside of their natural geographical range. To investigate the settlement of recently established populations of the neogastropod Cyclope neritea, we developed eight microsatellite markers. Their usefulness was studied in two native populations previously found to be monomorphic with mitochondrial markers. The eight loci were found to be polymorphic in both populations, with two to 18 alleles per locus. This result shows promise for these loci in studies of recently founded populations of C. neritea.     

Climate change causes rapid changes in the distribution and site abundance of birds in winter

Detecting coherent signals of climate change is best achieved by conducting expansive, long‐term studies. Here, using counts of waders (Charadrii) collected from ca. 3500 sites over 30 years and covering a major portion of western Europe, we present the largest‐scale study to show that faunal abundance is influenced by climate in winter. We demonstrate that the ‘weighted centroids’ of populations of seven species of wader occurring in internationally important numbers have undergone substantial shifts of up to 115 km, generally in a northeasterly direction. To our knowledge, this shift is greater than that recorded in any other study, but closer to what would be expected as a result of the spatial distribution of ecological zones. We establish that year‐to‐year changes in site abundance have been positively correlated with concurrent changes in temperature, but that this relationship is most marked towards the colder extremities of the birds' range, suggesting that shifts have occurred as a result of range expansion and that responses to climate change are temperature dependent. Many attempts to model the future impacts of climate change on the distribution of organisms, assume uniform responses or shifts throughout a species' range or with temperature, but our results suggest that this may not be a valid approach. We propose that, with warming temperatures, hitherto unsuitable sites in northeastern Europe will host increasingly important wader numbers, but that this may not be matched by declines elsewhere within the study area. The need to establish that such changes are occurring is accentuated by the statutory importance of this taxon in the designation of protected areas.