A generalist vector-transmitted parasite exhibits population genetic structure among host genera.

Abstract

Generalist parasites experience selective pressures from the various host species they infect. However, it is unclear if parasite transmission among host species precludes the establishment of host-specific adaptations and population genetic structure. We assessed the population genetic structure of the vector-transmitted avian haemosporidian parasite(lineage WW2; = 34 infections) in a single site in southern Sweden among 10 of its host species. The 2 best-sampled host genera were(2 species, = 15 infections) and(4 species, = 15). We designed a sequence capture protocol to isolate 1.13 Mbp (5%) of the parasite genome and identified 1399 variable sites among the sequenced infections. In a principal components analysis, infections ofandspecies mostly separated along the first 2 principal components. Sites with the highestvalues between the genera were found in genes that have mostly not been implicated in infection pathways, but several sites code for amino acid changes. An analysis of molecular variance confirmed significant variation among host genera, but not among host species within genera. The distribution of Tajima'samong sequenced loci was negatively skewed, plausibly reflecting a history of bottleneck followed by population expansion. Tajima'swas lower in infections ofthan, plausibly because WW2 began infectinghosts after it was already a parasite ofhosts. Our results provide evidence of vector-transmitted parasite population differentiation among host species in a single location. Future work should focus on identifying the mechanisms underlying this genetic population structure.