Strong neutral genetic differentiation in a host, but not in its parasite.

The genetic diversity and population structure of a parasite with a complex life cycle generally depends on the dispersal by its most motile host. Given that high gene flow is assumed to hinder local adaptation, this can impose significant constraints on a parasite's potential to adapt to local environmental conditions, intermediate host populations, and ultimately to host-parasite coevolution. Here, we aimed to examine the population genetic basis for local host-parasite interactions between the eye fluke Diplostomum lineage 6, a digenean trematode with a multi-host life cycle (including a snail, a fish, and a bird) and its second intermediate host, the three-spined stickleback Gasterosteus aculeatus L.

Distribution of common stickleback parasites on North Uist, Scotland, in relation to ecology and host traits.

Analysing spatial differences among macroparasite communities is an important tool in the study of host-parasite interactions. Identifying patterns can shed light on the underlying causes of heterogeneity of parasite distribution and help to better understand ecological constraints and the relative importance of host and parasite adaptations. In the present study, we aimed to find correlational evidence that the macroparasite distribution patterns on the Scottish island of North Uist, which had been described by de Roij and MacColl (2012), are indicative of local processes rather than an unspecific influence of habitat characteristics.

Sperm quality but not relatedness predicts sperm competition success in threespine sticklebacks (Gasterosteus aculeatus).

Background: Mating between close relatives often leads to a reduction of an individual's fitness, due to an increased expression of deleterious alleles. Thus, in many animal taxa pre- as well as postcopulatory inbreeding avoidance mechanisms have evolved. An increased risk of inbreeding and hence a loss of genetic variation may occur during founder events as in most cases only few individuals establish a new population.

In vitro leukocyte response of three-spined sticklebacks (Gasterosteus aculeatus) to helminth parasite antigens.

Helminth parasites of teleost fish have evolved strategies to evade and manipulate the immune responses of their hosts. Responsiveness of fish host immunity to helminth antigens may therefore vary depending on the degree of host-parasite counter-adaptation. Generalist parasites, infective for a number of host species, might be unable to adapt optimally to the immune system of a certain host species, while specialist parasites might display high levels of adaptation to a particular host species.