Data from: The role of host-range expansion and co-speciation in host-parasite associations with the divergence of the great tit species complex

During the evolution of parasites, co-speciation and host-range expansion
are thought to play roles in establishing associations with hosts, while
sorting events can lead to dissolution of those associations. To address
the roles of these processes, we focus on avian haemosporidian parasites
infecting hosts of the intensively studied great tit species complex. We
estimated the phylogeography of lineages detected in the species complex,
and quantified their transition probabilities among hosts. Lineages
detected in different host species presented a strong geographical signal
but do not form monophyletic groups. Yet, distributions of lineages are
not merely the result of their dispersal limitation, as many lineages that
infect only one of focal species can be found in birds sympatric with
other focal species. Besides, closely related lineages that infect the
same host species reach more similar rates of infection than expected by
chance. Finally, Haemoproteus and Leucocytozoon lineages infecting P.
major, the most recently dispersed species, were more generalized than
others, in consistent with a pattern of generalist parasites expanded
their host ranges by infecting newly encountered host species. Our results
suggest that host-parasite associations in this system are mainly the
result of sorting events and host-range expansion of parasites, rather
than co-speciation.

在寄生虫的演化历程中，协同物种形成（co-speciation）与宿主范围扩展（host-range expansion）被认为在建立宿主-寄生虫共生关联的过程中发挥关键作用，而分选事件则可能导致此类关联的解体。为厘清上述过程的具体作用机制，我们将研究对象聚焦于寄生于被广泛深入研究的大山雀（great tit）物种复合体宿主的禽血孢子虫（avian haemosporidian）寄生虫。我们对该物种复合体中检出的寄生虫谱系进行了系统地理学（phylogeography）推断，并量化了它们在不同宿主间的转移概率。研究发现，在不同宿主物种中检出的谱系呈现出显著的地理分布特征，但并未形成单系群（monophyletic groups）。然而，谱系的分布并非仅由扩散限制所决定：许多仅能在某一种目标宿主中检出的谱系，也可在与其他目标宿主同域分布（sympatric）的鸟类体内被发现。此外，寄生于同一宿主物种的近缘谱系，其感染率的相似性显著高于随机预期水平。最后，寄生于近期扩散的优势宿主大山雀（P. major）的血变虫属（Haemoproteus）与住白细胞虫属（Leucocytozoon）谱系，相较于其他谱系具有更广泛的宿主适应性，这与泛化寄生虫通过侵染新遇到的宿主物种以扩展自身宿主范围的演化模式相符。我们的研究结果表明，该研究系统中的宿主-寄生虫关联主要由分选事件与寄生虫的宿主范围扩展所塑造，而非协同物种形成。