寄生虫在传播过程中往往会感染新物种，即发生宿主扩张。这一过程可能导致传染病的发生，对新宿主产生较大危害，近年来愈加受到关注。鸟类血孢子虫（ Hemosporidian）是一种胞内寄生虫，分布广泛，多样性高，在野生鸟类中有较高的感染率，是研究寄生虫宿主扩张的理想系统。本研究使用2009-2021年间北京小龙门地区鸟类感染血孢子虫的多样性和感染率数据，结合宿主系统发育关系，分析了血孢子虫在小龙门鸟类群落中的年际动态。结果表明：（1）血孢子虫感染宿主的情况存在明显的年际动态变化，包括感染率和感染宿主范围；（2）感染宿主个体数多的血孢子虫谱系支在不同物种间分布较为分散，可能对当地鸟类群落威胁不大；（3）血孢子虫谱系支感染宿主数量和感染率的变化与其感染宿主范围的变化基本同步；（4）对于有明显主要宿主的血孢子虫，除ALARV04外，其余谱系支的宿主扩张行为与宿主亲缘关系的相关性不显著。

Parasites may occasionally expand their host range by infecting novel host species and lead to emerging infectious diseases. The importance in understanding host range expansion has been addressed by multiple outbreaks of infectious diseases in recent years. Hemosporidian are intracellular parasites with a wide distribution and high diversity, and present a high prevalence in wild bird populations, therefore can be used as an ideal model in studying host range expansion. In this study, we analyzed the annual dynamics of hemosporidian diversity and infection rates in the bird community of Xiaolongmen, Beijing from 2009 to 2021, and combined this with analyses of host phylogenetic relationships to understand the dynamics of these parasites in the bird community. The results showed that: (1) the infection status of hemosporidian parasites in hosts exhibited significant interannual dynamics in terms of infection rates and host range; (2) the parasite lineages infecting higher numbers of host individuals showed dispersed infection patterns among host species and therefore may pose a relatively small threat to the local bird community; (3) for most lineages, annual variations in the number of infected hosts and infection rates were closely synchronized with changes in their host ranges; and (4) except for ALARV04, host range expansion of hemosporidian lineages which present a certain major host was not significantly restricted by host phylogenetic relationships.