Data from: Infection with Haemoproteus iwa affects vector movement in a hippoboscid fly – frigatebird system

Haemosporidian parasites, which require both a vertebrate and invertebrate host, are most commonly studied in the life stages occurring in the vertebrate. However, aspects of the vector's behavior and biology can have profound effects on the parasite dynamics. Here we explore the effects of a haemosporidian parasite, Haemoproteusiwa, on a hippoboscid fly vector, Olfersiaspinifera. Olfersiaspinifera is an obligate ectoparasite of the great frigatebird, Fregata minor, living among bird feathers for all of its adult life. This study examines the movements of O. spiniferabetween great frigatebird hosts. Movement, or host-switching, was inferred by identifying host (frigatebird) microsatellite genotypesfrom fly bloodmeals that did not match the host from which the fly was collected. Such host-switches were analyzed using a logistic regression model, and the best-fit model included the H. iwa infection status of the fly and the bird host sex. Uninfected flies are more likely to have a bird genotype in their blood meal that was different from their current host's genotype (i.e., to have switched hosts) than infected flies. Flies collected from female birds were more likely to have switched hosts than those collected on males. Reduced movement of infected flies suggests that there may be a cost of parasitism for the fly. The effect of host sex is likely driven by differences in the sex ratio of bird hosts available to moving flies.

血孢子虫（Haemosporidian）需要脊椎动物与无脊椎动物两类宿主完成生活史，现有研究多聚焦于该类寄生虫在脊椎动物宿主体内的发育阶段。然而，媒介昆虫的行为与生物学特征，可对寄生虫的种群动态产生深远影响。本研究针对血变虫（Haemoproteus iwa）及其虱蝇媒介刺盘首虱蝇（Olfersia spinifera）展开探究，旨在明确前者对后者的影响。刺盘首虱蝇是大军舰鸟（Fregata minor）的专性外寄生虫，成虫整个生命周期均栖息于军舰鸟的羽毛间。本研究调查了刺盘首虱蝇在不同大军舰鸟宿主间的移动行为：通过检测虱蝇血餐中的宿主（军舰鸟）微卫星基因型（microsatellite genotypes），并将其与捕获该虱蝇的原宿主基因型进行比对，以此推断宿主转换（host-switching）事件的发生。研究采用逻辑回归模型（logistic regression model）对宿主转换事件进行分析，最优拟合模型纳入了虱蝇的血变虫感染状态以及宿主鸟类的性别两个变量。结果显示，未感染的虱蝇相较于感染个体，其血餐中的宿主基因型与当前宿主基因型不一致（即发生宿主转换）的概率更高；此外，从雌性军舰鸟体内捕获的虱蝇，发生宿主转换的概率也显著高于从雄性宿主捕获的个体。感染虱蝇的移动能力降低，提示寄生作用可能给媒介昆虫带来适合度代价。而宿主性别产生的上述影响，大概率源于移动中的虱蝇可接触到的鸟类宿主存在性比差异。