鸟类血孢子虫包含疟原虫（Plasmodium）、血液变形虫（Haemoproteus）、住白细胞原虫（Leucocytozoon）3个属，是鸟类中常见的体内寄生虫，会引起疟疾等血孢子虫症，对鸟类的健康造成危害。其生活史可分为鸟类宿主体内的无性生殖阶段和媒介昆虫体内的有性生殖阶段。系统发生研究表明，包括人疟原虫在内的所有现生血孢子虫的共同祖先均起源于鸟类血孢子虫，因此研究鸟类血孢子虫对认识人疟疾的毒力和传播机制以及新发传染病的产生机制有重要意义。血孢子虫可以感染绝大多数现生鸟类物种，基于形态学特征确定的鸟类血孢子虫超过250种，但今年来遗传及生态学证据的积累显示，这个类群的多样性大大超出形态学分类的物种数。鸟类血孢子虫的多样性主要受到环境、鸟类宿主、媒介昆虫以及血孢子虫之间相互关系等因素的影响。受制于众多影响因素和这些因素之间错综复杂的交互作用以及传统分析检测技术的制约，有关鸟类血孢子虫多样性的维持机制仍处于探索阶段。 本研究对北京西部山区灰眉岩鹀（Emberiza godlewskii）种群的血孢子虫多样性与感染格局进行了连续四年的检测，分析了灰眉岩鹀感染血孢子虫的多样性特征和时间动态以及宿主特异性与易感性的关系。其次，本研究结合海拔梯度和其它多种环境因子数据，分析了灰眉岩鹀血孢子虫感染率在海拔梯度上的微变化过程以及多种环境因子对血孢子虫感染率的影响。最后，本研究还通过分析灰眉岩鹀血孢子虫不同类群间多重感染的相关性和感染强度特征，探讨了血孢子虫之间共存与竞争的机制。主要研究结果如下： 1、灰眉岩鹀种群的血孢子虫感染率高达89.63%，共检出血孢子虫支系（lineage）29个，其多样性与感染率均没有显著的年际变化。其中4个优势支系的感染率（13.36% ~ 43.32%）远高于其它支系（均不足3%），合计感染的个体数占总体的84.56%。其中三个优势支系未在本地其它雀形目鸟类中发现过，具有较高的宿主特异性；只有ALARV04在宿主特异性较低的情况下仍可以在灰眉岩鹀种群中获得很高的感染率。以上结果表明，在灰眉岩鹀种群中，由少数专性寄生的优势血孢子虫支系感染造成的稳定的高感染率，可能是寄生虫与宿主通过长期协同演化发展出的关系，相互之间可借此获得较高的相对适合度。因而，灰眉岩鹀血孢子虫的宿主特异性和感染率之间的关系更符合权衡假说的预期：即专性寄生者只需应对少数宿主物种的免疫系统，从而可以更充分的利用特异宿主的资源，由此在其适宜宿主（competent host）中获得比泛性寄生者更高的多度。 2、海拔梯度分析结果表明，优势支系疟原虫ALARV04的感染率与海拔梯度呈正相关，DENVID02的感染率与海拔梯度负相关，并且两者的感染率变化主要集中于1000 m ~ 1200 m海拔区间。环境因子分析结果表明，气温、降水、地形方面的环境因子与多个血孢子虫类群（ALARV04、DENVID02、EMSPO05、血液变形虫、住白细胞原虫）的感染率表现出了不同的相关趋势。不同类群血孢子虫与环境因子之间多样的相关关系反映了环境异质性对塑造血孢子虫多样性的空间格局有重要作用。这种影响可能由环境直接作用于血孢子虫，也可能通过鸟类宿主或媒介昆虫间接作用于血孢子虫。 3、在感染灰眉岩鹀的4个血孢子虫优势支系中，遗传距离较近（ALARV04与PADOM02）和较远（疟原虫属于住白细胞原虫属）的支系之间可以共存，甚或有显著的协同关系。而遗传距离居中的的支系之间（ALARV04与DENVID02、PADOM02与DENVID02）则有显著的拮抗关系。单一感染ALARV04或PADOM02的宿主与同时感染这两个支系的宿主相比，在各项身体质量指标上均没有显著差异。利用微滴式数字PCR（ddPCR）对ALARV04和PADOM02在不同感染类型宿主中感染强度的检测表明，单一感染时，ALARV04的感染强度显著高于PADOM02；两个支系多重感染时，ALARV04的感染强度显著下降至与共同感染的PADOM02没有显著区别，而PADOM02的感染强度相比单一感染时没有显著变化。以上结果表明，遗传距离较近和较远的血孢子虫支系之间都可以在多重感染中稳定共存，并且遗传距离较近的血孢子虫支系并没有在多重感染中表现出强烈的竞争关系，很好的支持了共存理论中的自组织相似性假说。

The avian haemosporidian parasite, including Plasmodium, Haemoproteus and Leucocytozoon, is a taxon of common blood parasite in birds, which can cause malaria and other haemosporidiosis. These diseases are harmful to the health of birds. Life history of haemosporidian parasites is divided into two stages: the asexual reproduction stage and the sexual reproduction stage. Phylogenetic studies have shown that all the haemosporidian parasites of other vertebrates originates from the avian haemosporidian parasites, so the study of avian haemosporidian parasites is important for the understanding of the virulence and transmission mechanism of human malaria and the mechanism of emerging zoonosis. There are more than 250 species of bird species based on morphological characteristics, and the genetic and ecological evidence in this year shows that the diversity of this group is much more than the number of morphological taxonomy. The diversity of avian haemosporidian parasites is mainly influenced by factors such as environment, bird hosts, vector insects and haemosporidian parasites. It is still in the exploration stage for the maintenance mechanism of the diversity of the avian haemosporidian parasites diversity, as well as the complex interaction between these factors and the constraints of traditional analysis and detection technology. In this study, the diversity and infection pattern of the Godlewski's Bunting (Emberiza godlewskii) population in mountain area of western Beijing were tested for four years. The diversity and time dynamics of these parasites and the relationship between the host specificity and the susceptibility were analyzed. Secondly, this study combined the data of altitude gradient and other environmental factors to analyze the fine process of the prevalence of haemosporidian parasites on the altitude gradient and the influence of various environmental factors on the prevalence. Finally, the mechanism of coexistence and competition among these parasites was studied by analyzing the correlation and parasitemia of multiple infection among different haemosporidian parasites. The main results are as follows: 1. The prevalence of the haemosporidian parasites of the population in the western mountain area of Beijing was 89.63%, and 29 lineages were detected. There was no significant annual variation in the diversity and prevalence. The prevalence of 4 dominant lineages (13.36% ~ 43.32%) were much higher than those of others (all less than 3%), and the total prevalence of these 4 lineages was 84.56%. Three dominant lineages with high host specificity were not found in other local passerine birds, and host specificity of ALARV04 is also higher than other generalist parasite lineages of local passerine community, despite it has a few other host species. The above results show that the stable high prevalence caused by a few parasitic lineages, may be the result of long-term coevolution between parasite and host. Therefore, the relationship between host specificity and prevalence of the haemosporidian parasites of Godlewski's Bunting is more consistent with the trade-off hypothesis: that the specific parasites only need to respond to the immune system of a few host species, so that the resources of the specific host can be more fully utilized and thus more ubiquitous parasitism is obtained in the competent host. 2. The results of altitude gradient analysis showed that the prevalence of Plasmodium ALARV04 was positively correlated with the elevation gradient, and the prevalence of DENVID02 was negatively correlated with the elevation gradient, and the change of the prevalence mainly concentrated on the altitude of 1000 m ~ 1200 m. The results of environmental factors analysis showed that the environmental factors of temperature, precipitation and topography were related to the prevalences of ALARV04, DENVID02, EMSPO05, Haemoproteus and Leucocytozoon. The diversity of relationship between haemosporidian parasites and environmental factors shows that environmental heterogeneity plays an important role in the spatial pattern of haemosporidian diversity. This effect may be directly affected by environment on haemosporidian parasites, or indirectly by avian hosts and vectors. 3. Among the 4 dominant haemosporidian lineages, the closely related lineages(ALARV04 and PADOM02) and the distantly related lineages(lineages from Plasmodium and lineages from Leucocytozoon) can coexist, but the moderately related lineages (ALARV04 and DENVID02, PADOM02 and DENVID02) has significant antagonistic relationship. Single and muntiple infection of ALARV04 or PADOM02 has no significant difference influence to body condition of Godlewski's Bunting. Parasitemia of ALARV04 and PADOM02 (tested by droplet digital PCR, ddPCR) in different types of infected showed that the parasitemia of ALARV04 was significantly higher than that of PADOM02 in single infection. In multiple infection, the infection intensity of ALARV04 decreased significantly to similar to parasitemia of PADOM02. The results showed that the closely and distantly related haemosporidian lineages could coexist in multiple infections, and the closely related lineages did not show a strong competitive relationship in multiple infections. This result supported the self-organization similarity hypothesis.