Host-related genetic differentiation of a polyxenic avian ectoparasite, Ornithomya avicularia (Hippoboscidae)

Abstract

Ectoparasites play a key role in ecosystems, affecting the health, behaviour, and reproductive success of their hosts. The parasite-host relationships are complex and dynamic, and selective pressures exerted by the hosts can lead to local adaptations and changes in the genetic structure of the parasite population. Our aim was to investigate how parasitism on a diverse range of avian hosts with varying ecology and habitat preferences shapes the genetic variation of the parasite. For this purpose, we quantified the genetic structure and differentiation of host-related populations of a common polyxenic avian ectoparasite Ornithomya avicularia (Hippoboscidae, Ornithomyinae), a louse fly species parasitizing various bird species occupying diverse ecological niches. Using 20 polymorphic microsatellite markers, we genotyped louse flies collected from four phylogenetically (passerine and non-passerine) and ecologically (wetland vs. forest) divergent avian hosts caught during autumn migration. Despite the ecological and phylogenetic differences among hosts, the genetic differentiation among louse fly populations was modest, indicating ongoing gene flow. Bayesian clustering and discriminant analysis identified two genetic clusters with relatively weak barriers to gene flow, but this clustering reflected neither phylogenetic nor ecological differences between hosts. We suggest that the high dispersal abilities and the specific reproductive strategy of O. avicularia likely contribute to the genetic homogeneity of its populations across ecologically and phylogenetically distant hosts. This study provides novel insights into the population genetics of an understudied ectoparasite, with implications for understanding host-parasite interactions and disease transmission in avian systems.

Keywords: Avian parasites; Birds; Ectoparasites; Hippoboscidae; Louse flies; Microsatellite markers; Ornithomya avicularia.

Graphical abstract

Fig. 1

Map of Poland with sampling sites for Ornithomya avicularia. Relative frequencies of avian hosts at each sampling site are shown with pie charts, where red – common blackbird, blue – common snipe, green – long-eared owl, yellow – reed warblers.

Fig. 2

Bayesian assignment of Ornithomya avicularia from four populations occurring at different avian hosts to genetic clusters. Each bar at the assignment plot (C) represents the estimated proportional posterior probability of each individual belonging to each of two inferred genetic clusters, as marked with different colours (blue and orange). Genetic clusters were inferred for seventeen microsatellite markers and ln-transformed probability for different number of clusters (K) is shown in the B panel.

Fig. 3

Genetic clustering by the Discriminant Analysis of Principal Components (DAPC) for four Ornithomya avicularia populations occurring at different avian hosts: Eurasian blackbird Turdus merula, common snipe Gallinago gallinago, long-eared owl Asio otus, and Acrocephalus warblers (i.e. great reed warbler A. arundinaceus and common reed warbler A. scirpaceus). Individuals of Ornithomya avicularia are shown as dots and the avian host species as inertia ellipses (marked with a different colour). Two discriminant functions (DF1 and DF2) explaining most between-host genetic variance in the data are shown. Eigenvalues of principal components and discriminant functions used in the analysis are displayed in upper left and bottom right insets, respectively.