Genomic insights into kin selection and developmental conflict in co-occurring hairworm parasites

Abstract Many parasites manipulate the behaviour or appearance of their host to improve their own survival or transmission, with manipulation timing tightly linked to a parasite’s developmental stage. However, host manipulations are complicated by the presence of co-occurring parasites within the same host. Conspecific co-occurring parasites of similar developmental stages may interact collaboratively to manipulate a host. However, co-occurring parasites of different developmental stages will conflict with one another, especially when the manipulation is fatal to developmentally immature co-occurring parasites. Kin selection further complicates these interactions by predicting that closely related co-occurring parasites may not interfere with the other’s manipulation. Co-occurring hairworm (Nematomorpha) parasites are common, and the water-seeking manipulation mature worms induce is probably lethal to co-occurring juvenile worms. To understand the role that kin selection may have on these interactions, we assess kin relationships in a wild hairworm population. We sequence, to our knowledge the first, New Zealand hairworm (Gordius paranensis) genome and use reduced representation sequencing to estimate relatedness among co-occurring worms. We show that co-occurring hairworm relatedness varies from unrelated to highly related and that both mature and immature worms inhabit the same host. We discuss how these developmental and kinship dynamics may shape host manipulations and hairworm survival.