Medeiros M C I, Ellis V A, Ricklefs R E
Department of Biology, University of Missouri-St. Louis, One University Boulevard, St. Louis, MO, USA.
J Evol Biol. 2014 Nov;27(11):2520-8. doi: 10.1111/jeb.12514. Epub 2014 Oct 13.
Parasite specialization on one or a few host species leads to a reduction in the total number of available host individuals, which may decrease transmission. However, specialists are thought to be able to compensate by increased prevalence in the host population and increased success in each individual host. Here, we use variation in host breadth among a community of avian Haemosporida to investigate consequences of generalist and specialist strategies on prevalence across hosts. We show that specialist parasites are more prevalent than generalist parasites in host populations that are shared between them. Moreover, the total number of infections of generalist and specialist parasites within the study area did not vary significantly with host breadth. This suggests that specialists can infect a similar number of host individuals as generalists, thus compensating for a reduction in host availability by achieving higher prevalence in a single host species. Specialist parasites also tended to infect older hosts, whereas infections by generalists were biased towards younger hosts. We suggest that this reflects different abilities of generalists and specialists to persist in hosts following infection. Higher abundance and increased persistence in hosts suggest that specialists are more effective parasites than generalists, supporting the existence of a trade-off between host breadth and average host use among these parasites.
寄生物对一种或少数几种宿主物种的专一化会导致可利用宿主个体总数减少，这可能会降低传播率。然而，一般认为专性寄生物能够通过提高在宿主种群中的流行率以及在每个宿主个体中的成功率来进行补偿。在此，我们利用鸟类疟原虫群落中宿主广度的差异，来研究泛化和特化策略对不同宿主中流行率的影响。我们发现，在它们共有的宿主种群中，专性寄生物比泛性寄生物更为普遍。此外，研究区域内泛性和专性寄生物的感染总数并未随宿主广度而显著变化。这表明，专性寄生物能够感染与泛性寄生物数量相近的宿主个体，从而通过在单一宿主物种中实现更高的流行率来弥补宿主可利用性的降低。专性寄生物还倾向于感染年龄较大的宿主，而泛性寄生物的感染则偏向于较年轻的宿主。我们认为，这反映了泛性和专性寄生物在感染后在宿主体内持续存在的不同能力。在宿主体内更高的丰度和更强的持续存在能力表明，专性寄生物比泛性寄生物是更有效的寄生物，这支持了这些寄生物在宿主广度和平均宿主利用之间存在权衡的观点。
